DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

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NONRESIDENTTRAININGCOURSE

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September 1999

Utilitiesman BasicVolume 2NAVEDTRA 14279�

DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

Although the words “he,” “him,” and“his” are used sparingly in this course toenhance communication, they are notintended to be gender driven or to affront ordiscriminate against anyone.

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PREFACE

By enrolling in this self-study course, you have demonstrated a desire to improve yourself and the Navy.Remember, however, this self-study course is only one part of the total Navy training program. Practicalexperience, schools, selected reading, and your desire to succeed are also necessary to successfully roundout a fully meaningful training program.

COURSE OVERVIEW: In completing this nonresident training course, you will demonstrate aknowledge of the subject matter by correctly answering questions on the following subjects:

Boilers Galley and Laundry EquipmentBoiler Maintenance RefrigerationSteam Distribution Systems Air ConditioningHeating Systems

THE COURSE: This self-study course is organized into subject matter areas, each containing learningobjectives to help you determine what you should learn along with text and illustrations to help youunderstand the information. The subject matter reflects day-to-day requirements and experiences ofpersonnel in the rating or skill area. It also reflects guidance provided by Enlisted Community Managers(ECMs) and other senior personnel, technical references, instructions, etc., and either the occupational ornaval standards, which are listed in the Manual of Navy Enlisted Manpower Personnel Classificationsand Occupational Standards, NAVPERS 18068.

THE QUESTIONS: The questions that appear in this course are designed to help you understand thematerial in the text.

VALUE: In completing this course, you will improve your military and professional knowledge.Importantly, it can also help you study for the Navy-wide advancement in rate examination. If you arestudying and discover a reference in the text to another publication for further information, look it up.

1999 Edition Prepared byUTC(SCW) Dennis E. Richmond

Published byNAVAL EDUCATION AND TRAINING

PROFESSIONAL DEVELOPMENTAND TECHNOLOGY CENTER

NAVSUP Logistics Tracking Number0504-LP-026-9110

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Sailor’s Creed

“I am a United States Sailor.

I will support and defend theConstitution of the United States ofAmerica and I will obey the ordersof those appointed over me.

I represent the fighting spirit of theNavy and those who have gonebefore me to defend freedom anddemocracy around the world.

I proudly serve my country’s Navycombat team with honor, courageand commitment.

I am committed to excellence andthe fair treatment of all.”

CONTENTS

CHAPTER Page

1. Boilers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

2. Boiler Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

3. Steam Distribution Systems . . . . . . . . . . . . . . . . . . . . . . 3-1

4. Heating Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

5. Galley and Laundry Equipment . . . . . . . . . . . . . . . . . . . . 5-1

6. Refrigeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

7. Air Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

APPENDIX

I. Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AI-1

II. Tables for Maintenance Procedures . . . . . . . . . . . . . . . . . AII-1

III. Math Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . AIII-1

IV. Answers Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . AIV-1

V. References Used to Develop the TRAMAN . . . . . . . . . . . . AV-1

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX-l

Nonresident Training Course follows Index

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SUMMARY OF UTILITIESMAN BASIC

VOLUME 1

Utilitiesman Basic, Volume 1, NAVEDTRA 11019, consists of chapters onConstruction Plans, Specifications, Color Coding: Advanced Base FunctionalComponents (ABFC); Plumbing; Plumbing Valves and Accessories; PlumbingFixtures and Plumbing Repairs; Pumps and Compressors; Water Treatment; andMaintenance of Water Treatment Equipment.

VOLUME 2

Utilitiesman Basic, Volume 2, NAVEDTRA 11020, consists of chapters onBoilers; Boiler Maintenance; Steam Distribution Systems; Heating Systems; Galleyand Laundry Equipment; Refrigeration; and Air Conditioning.

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SAFETY PRECAUTIONS

Safety is a paramount concern for all personnel. Many of the Naval Ship’sTechnical Manuals, manufacturer’s technical manuals, and every Planned MaintenanceSystem (PMS) maintenance requirement card (MRC) include safety precautions.Additionally, OPNAVINST 5100.19 (series), Naval Occupational Safety and Health(NAVOSH) Program Manual for Forces Afloat, and OPNAVINST 5100.23 (series),NAVOSH Program Manual, provide safety and occupational health information. Thesafety precautions are for your protection and to protect equipment.

During equipment operation and preventive or corrective maintenance, theprocedures may call for personal protective equipment (PPE), such as goggles, gloves,safety shoes, hard hats, hearing protection, and respirators. When specified, your use ofPPE is mandatory. You must select PPE appropriate for the job since the equipment ismanufactured and approved for different levels of protection. If the procedure does notspecify the PPE, and you aren't sure, ask your safety officer.

Most machinery, spaces, and tools requiring you to wear hearing protection areposted with hazardous noise signs or labels. Eye hazardous areas requiring you to weargoggles or safety glasses are also posted. In areas where corrosive chemicals are mixedor used, an emergency eyewash station must be installed.

All lubricating agents, oil, cleaning material, and chemicals used in maintenanceand repair are hazardous materials. Examples of hazardous materials are gasoline, coaldistillates, and asphalt. Gasoline contains a small amount of lead and other toxiccompounds. Ingestion of gasoline can cause lead poisoning. Coal distillates, such asbenzene or naphthalene in benzol, are suspected carcinogens. Avoid all skin contact anddo not inhale the vapors and gases from these distillates. Asphalt contains componentssuspected of causing cancer. Anyone handling asphalt must be trained to handle it in asafe manner.

Hazardous materials require careful handling, storage, and disposal. PMSdocumentation provides hazard warnings or refers the maintenance man to theHazardous Materials User’s Guide. Material Safety Data Sheets (MSDS) also providesafety precautions for hazardous materials. All commands are required to have anMSDS for each hazardous material they have in their inventory. You must be familiarwith the dangers associated with the hazardous materials you use in your work.Additional information is available from you command's Hazardous MaterialCoordinator. OPNAVINST 4110.2 (series), Hazardous Material Control andManagement, contains detailed information on the hazardous material program.

Recent legislation and updated Navy directives implemented tighter constraints onenvironmental pollution and hazardous waste disposal. OPNAVINST 5090.1 (series),Environmental and Natural Resources Program Manual, provides detailedinformation. Your command must comply with federal, state, and local environmentalregulations during any type of construction and demolition. Your supervisor willprovide training on environmental compliance.

Cautions and warnings of potentially hazardous situations or conditions arehighlighted, where needed, in each chapter of this TRAMAN. Remember to be safetyconscious at all times.

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INSTRUCTIONS FOR TAKING THE COURSE

ASSIGNMENTS

The text pages that you are to study are listed atthe beginning of each assignment. Study thesepages carefully before attempting to answer thequestions. Pay close attention to tables andillustrations and read the learning objectives.The learning objectives state what you should beable to do after studying the material. Answeringthe questions correctly helps you accomplish theobjectives.

SELECTING YOUR ANSWERS

Read each question carefully, then select theBEST answer. You may refer freely to the text.The answers must be the result of your ownwork and decisions. You are prohibited fromreferring to or copying the answers of others andfrom giving answers to anyone else taking thecourse.

SUBMITTING YOUR ASSIGNMENTS

To have your assignments graded, you must beenrolled in the course with the NonresidentTraining Course Administration Branch at theNaval Education and Training ProfessionalDevelopment and Technology Center(NETPDTC). Following enrollment, there aretwo ways of having your assignments graded:(1) use the Internet to submit your assignmentsas you complete them, or (2) send all theassignments at one time by mail to NETPDTC.

Grading on the Internet: Advantages toInternet grading are:

• you may submit your answers as soon asyou complete an assignment, and

• you get your results faster; usually by thenext working day (approximately 24 hours).

In addition to receiving grade results for eachassignment, you will receive course completionconfirmation once you have completed all the

assignments. To submit your assignmentanswers via the Internet, go to:

http://courses.cnet.navy.mil

Grading by Mail: When you submit answersheets by mail, send all of your assignments atone time. Do NOT submit individual answersheets for grading. Mail all of your assignmentsin an envelope, which you either provideyourself or obtain from your nearest EducationalServices Officer (ESO). Submit answer sheetsto:

COMMANDING OFFICERNETPDTC N3316490 SAUFLEY FIELD ROADPENSACOLA FL 32559-5000

Answer Sheets: All courses include one“scannable” answer sheet for each assignment.These answer sheets are preprinted with yourSSN, name, assignment number, and coursenumber. Explanations for completing the answersheets are on the answer sheet.

Do not use answer sheet reproductions: Useonly the original answer sheets that weprovide—reproductions will not work with ourscanning equipment and cannot be processed.

Follow the instructions for marking youranswers on the answer sheet. Be sure that blocks1, 2, and 3 are filled in correctly. Thisinformation is necessary for your course to beproperly processed and for you to receive creditfor your work.

COMPLETION TIME

Courses must be completed within 12 monthsfrom the date of enrollment. This includes timerequired to resubmit failed assignments.

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PASS/FAIL ASSIGNMENT PROCEDURES

If your overall course score is 3.2 or higher, youwill pass the course and will not be required toresubmit assignments. Once your assignmentshave been graded you will receive coursecompletion confirmation.

If you receive less than a 3.2 on any assignmentand your overall course score is below 3.2, youwill be given the opportunity to resubmit failedassignments. You may resubmit failedassignments only once. Internet students willreceive notification when they have failed anassignment--they may then resubmit failedassignments on the web site. Internet studentsmay view and print results for failedassignments from the web site. Students whosubmit by mail will receive a failing result letterand a new answer sheet for resubmission of eachfailed assignment.

COMPLETION CONFIRMATION

After successfully completing this course, youwill receive a letter of completion.

ERRATA

Errata are used to correct minor errors or deleteobsolete information in a course. Errata mayalso be used to provide instructions to thestudent. If a course has an errata, it will beincluded as the first page(s) after the front cover.Errata for all courses can be accessed andviewed/downloaded at:

http://www.advancement.cnet.navy.mil

STUDENT FEEDBACK QUESTIONS

We value your suggestions, questions, andcriticisms on our courses. If you would like tocommunicate with us regarding this course, weencourage you, if possible, to use e-mail. If youwrite or fax, please use a copy of the StudentComment form that follows this page.

For subject matter questions:

E-mail: n314.products@cnet.navy.milPhone: Comm: (850) 452-1001, Ext. 1826

DSN: 922-1001, Ext. 1826FAX: (850) 452-1370(Do not fax answer sheets.)

Address: COMMANDING OFFICERNETPDTC N3146490 SAUFLEY FIELD ROADPENSACOLA FL 32509-5237

For enrollment, shipping, grading, orcompletion letter questions

E-mail: fleetservices@cnet.navy.milPhone: Toll Free: 877-264-8583

Comm: (850) 452-1511/1181/1859DSN: 922-1511/1181/1859FAX: (850) 452-1370(Do not fax answer sheets.)

Address: COMMANDING OFFICERNETPDTC N3316490 SAUFLEY FIELD ROADPENSACOLA FL 32559-5000

NAVAL RESERVE RETIREMENT CREDIT

If you are a member of the Naval Reserve,you may earn retirement points for successfullycompleting this course, if authorized undercurrent directives governing retirement of NavalReserve personnel. For Naval Reserve retire-ment, this course is evaluated at 12 points.(Refer to Administrative Procedures for NavalReservists on Inactive Duty, BUPERSINST1001.39, for more information about retirementpoints.)

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Student Comments

Course Title: Utilitiesman Basic, Volume 2

NAVEDTRA: 14279 Date:

We need some information about you:

Rate/Rank and Name: SSN: Command/Unit

Street Address: City: State/FPO: Zip

Your comments, suggestions, etc.:

Privacy Act Statement: Under authority of Title 5, USC 301, information regarding your military status isrequested in processing your comments and in preparing a reply. This information will not be divulged withoutwritten authorization to anyone other than those within DOD for official use in determining performance.

NETPDTC 1550/41 (Rev 4-00

CHAPTER 1

BOILERS

Learning Objectives: Describe the principles and theory of steam generation.Identify different types of boilers and the design requirements for boilers. Describethe purpose and operation of the different types of boilers and their fittings andaccessories. Describe the methods and procedures for the testing and treatment ofboiler water. Describe methods and procedures involved in fireside and watersidecleaning.

A boiler is an enclosed vessel in which water is

heated and circulated, either as hot water or steam, to

produce a source for either heat or power. A centralheating plant may have one or more boilers that usegas, oil, or coal as fuel. The steam generated is used toheat buildings, provide hot water, and provide steamfor cleaning, sterilizing, cooking, and launderingoperations. Small package boilers also provide steam

and hot water for small buildings.

A careful study of this chapter can help youacquire useful knowledge of steam generation, typesof boilers pertinent to Seabee operations, variousfittings commonly found on boilers, and so on. Theprimary objective of this chapter is to lay thefoundation for you to develop skill in the operation,maintenance, and repair of boilers.

STEAM GENERATION THEORY

Learning Objective: Describe the principles andtheory of steam generation.

To acquaint you with some of the fundamentalsunderlying the process of steam operation, supposethat you set an open pan of water on the stove and turnon the heat. You find that the heat causes thetemperature of the water to increase and, at the sametime, to expand in volume. When the temperaturereaches the BOILING POINT (212°F or 100°C at sealevel). a physical change occurs in the water; the waterstarts vaporizing. When you hold the temperature at theboiling point long enough, the water continues tovaporize until the pan is dry. A point to remember is thatTHE TEMPERATURE OF WATER DOES NOTINCREASE BEYOND THE BOILING POINT. Even ifyou add more heat after the water starts to boil, the water

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cannot get any hotter as long as it remains at the samepressure.

Now suppose you place a tightly fitting lid on the panof boiling water. The lid prevents the steam fromescaping from the pan and this results in a buildup ofpressure inside the container. However, when you makean opening in the lid, the steam escapes at the same rate itis generated. As long as water remains in the pan and aslong as the pressure remains constant, the temperature ofthe water and steam remains constant and equal.

The steam boiler operates on the same basic principleas a closed container of boiling water. By way ofcomparison, it is as true with the boiler as with the closedcontainer that steam formed during boiling tends to pushagainst the water and sides of the vessel. Because of thisdownward pressure on the surface of the water, atemperature in excess of 212°F is required for boiling.The higher temperature is obtained simply by increasingthe supply of heat; therefore, the rules you shouldremember are as follows:

1. All of the water in a vessel, when held at theboiling point long enough, will change into steam. ASLONG AS THE PRESSURE IS HELD CONSTANT,THE TEMPERATURE OF THE STEAM ANDBOILING WATER REMAINS THE SAME.

2. AN INCREASE IN PRESSURE RESULTS INAN INCREASE IN THE BOILING POINTTEMPERATURE OF WATER.

A handy formula with a couple of fixed factors willprove this theory. The square root of steam pressuremultiplied by 14 plus 198 will give you the steamtemperature. When you have 1 psig of steam pressure,the square root is one times 14 plus 198 which equals212°F which is the temperature that the water will boil at1 psig.

There are a number of technical terms used inconnection with steam generation. Some of thesecommonly used terms you should know are as follows:

"Degree" is defined as a measure of heat intensity.

"Temperature" is defined as a measure indegrees of sensible heat. The term sensible heatrefers to heat that can be measured with athermometer.

"HEAT" is a form of energy measured in Britishthermal units (Btu). One Btu is the amount of heatrequired to raise 1 pound of water 1 degreeFahrenheit at sea level.

"Steam" means water in a vapor state. DRYSATURATED STEAM is steam at the saturationtemperature corresponding to pressure, and itcontains no water in suspension. WETSATURATED STEAM is steam at the saturationtemperature corresponding to pressure, and itcontains water particles in suspension.

The "QUALITY" of steam is expressed in terms ofpercent. For instance, if a quantity of wet steamconsists of 90 percent steam and 10 percentmoisture, the quality of the mixture is 90 percent.

"SUPERHEATED STEAM" is steam at atemperature higher than the saturation temperaturecorresponding to pressure. For example, a boilermay operate at 415 psig (pounds per square inchgauge). The corresponding saturation temperaturefor this pressure is 483°F, and this will be thetemperature of the water in the boiler and the steamin the drum. (Charts and graphs are available forcomputing this pressure-temperaturerelationship.) This steam can be passed through asuperheater where the pressure remains about thesame, but the temperature will be increased tosome higher figure.

Q4.

Q5.

Q1. When heat is applied to water, what physicalchange occurs?

Q2. How is a "degree" of heat defined?

Q3. As long as the pressure in a boiler is heldconstant, what factor remains the same in theboiler?

BOILER DESIGN REQUIREMENTS

Learning Objective: Describe the design requirementsfor boilers.

A boiler must meet certain requirements before it isconsidered satisfactory for operation. Three importantrequirements for a boiler are as follows:

1. The boiler must be safe to operate.

2. The boiler must be able to generate steam at thedesired rate and pressure.

3. The boiler must be economical to operate.

NOTE

Make it a point to familiarize yourselfw i t h t h e b o i l e r c o d e a n d o t h e rrequirements applicable to the area inwhich you are located.

Design rules for boilers are established by the ASME(American Society of Mechanical Engineers). Theserules are general guidelines used by engineers whendesigning boilers. These rules require that for economyof operation and to generate steam at the desired rate andpressure, a boiler must have the following attributes:

Adequate water and steam capacity

Rapid and positive water circulation

A large steam generating surface

Heating surfaces that are easy to clean on bothwater and gas sides

Parts accessible for inspection

A correct amount and proper arrangement ofheating surface

A firebox for efficient combustion of fuel

What three requirements must a boiler meet beforebeing considered satisfactory for operation?

What organization has established guidelines fordesigning boilers?

TYPES OF BOILERS

Learning Objective: Identify the different types ofboilers and describe the operation of each.

The Utilitiesman is concerned primarily with theFIRE-TUBE type of boiler, since it is the type generallyused in Seabee operations. However, the WATER-TUBE type of boiler may occasionally be used at someactivities. The information in this chapter primarilyconcerns the different designs and construction feature:of fire-tube boilers.

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concerns the different designs and construction featuresof fire-tube boilers.

The basis for identifying the two types is as follows:

WATER-TUBE BOILERS are those in which theproducts ofcombustion surround the tubes throughwhich the water flows.

FIRE-TUBE BOILERS are those in which theproducts of combustion pass through the tubes andthe water surrounds them.

WATER-TUBE BOILERS

Water-tube boilers may be classified in a number ofways. For our purpose, they are classified as eitherstraight tube or bent tube. These classes are discussedseparately in succeeding sections. To avoid confusion,make sure you study carefully each illustration referredto throughout the discussion.

Straight Tube

The STRAIGHT-TUBE class of water-tube boilersincludes three types:

1. Sectional-header cross drum

2. Box-header cross drum

3. Box-header longitudinal drum

In the SECTIONAL-HEADER CROSS DRUMboiler with vertical headers, the headers are steel boxesinto which the tubes are rolled. Feedwater enters andpasses down through the downcomers (pipes) into therear sectional headers from which the tubes are supplied.The water is heated and some of it changes into steam as itflows through the tubes to the front headers. Thesteam-water mixture returns to the steam drum throughthe circulating tubes and is discharged in front of thesteam-drum baffle that helps to separate the water andsteam.

Steam is removed from the top of the drum throughthe dry pipe. This pipe extends along the length of thedrum and has holes or slots in the top half for steam toenter.

Headers, the distinguishing feature of this boiler. areusually made of forged steel and are connected to thedrums with tubes. Headers may be vertical or at rightangles to the tubes. The tubes are rolled and flared intothe header. A handhold is located opposite the ends ofeach tube to facilitate inspection and cleaning. Itspurpose is to collect sediment that is removed by blowingdown the boiler.

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Baffles are usually arranged so gases are directedacross the tubes three times before being discharged fromthe boiler below the drum.

BOX-HEADER CROSS DRUM boilers are shallowboxes made of two plates—a tube-sheet plate that is bentto form the sides of the box, and a plate containing thehandholds that is riveted to the tube-sheet plate. Some aredesigned so that the front plate can be removed for accessto tubes. Tubes enter at right angles to the box header andare expanded and flared in the same manner as thesectional-header boiler. The boiler is usually built withthe drum in front. It is supported by lugs fastened to thebox headers. This boiler has either cross or longitudinalbaffling arranged to divide the boiler into three passes.Water enters the bottom of the drum, flows throughconnecting tubes to the box header, through the tubes tothe rear box header, and back to the drum.

BOX-HEADER LONGITUDINAL DRUMboilers have either a horizontal or inclined drum. Boxheaders are fastened directly to the drum when thedrum is inclined. When the drum is horizontal, thefront box header is connected to it at an angle greaterthan 90 degrees. The rear box header is connected tothe drum by tubes. Longitudinal or cross baffles can beused with either type.

Bent Tube

Bent tube boilers usually have three drums. Thedrums are usually of the same diameter and positioned atdifferent levels with each other. The uppermost orhighest positioned drum is referred to as the STEAMDRUM, while the middle drum is referred to as theWATER DRUM, and the lowest, the MUD DRUM. Tubebanks connect the drums. The tubes are bent at the ends toenter the drums radially.

Water enters the top rear drum, passes through thetubes to the bottom drum, and then moves up through thetubes to the top front drum. A mixture of steam and wateris discharged into this drum. The steam returns to the toprear drum through the upper row of tubes, while the watertravels through the tubes in the lower rear drum by tubesextending across the drum and enters a small collectingheader above the front drum.

Many types of baffle arrangements are used withbent-tube boilers. Usually, they are installed so that theinclined tubes between the lower drum and the top frontdrum absorb 70 to 80 percent of the heat. The water-tubeboilers discussed above offer a number of worthwhileadvantages. For one thing, they afford flexibility instarting up. They also have a high productive capacity

ranging from 100.000 to 1,000,000 pounds of steam perhour. In case of tube failure, there is little danger of adisastrous explosion of the water-tube boiler. Thefurnace not only can carry a high overload, it can also bemodified for tiring by oil or coal. Still another advantageis that it is easy to get into sections inside the furnace toclean and repair them. There are also severaldisadvantages common to water-tube boilers. One of themain drawbacks of water-tube boilers is their highconstruction cost. The large assortment of tubes requiredof this boiler and the excessive weight per unit weight ofsteam generated are other unfavorable factors.

FIRE-TUBE BOILERS

There are four types of fire-tube boilers—the Scotchmarine boiler. the vertical-tube boiler, the horizontalreturn tubular boiler. and the firebox boiler. These fourtypes of boilers are discussed in this section.

Scotch Marine Boiler

The Scotch marine tire-tube boiler is especiallysuited to Seabee needs. Figure 1-1 is a portable Scotchmarine tire-tube boiler. The portable unit can be movedeasily and requires only a minimal amount of foundationwork. As a complete self-contained unit. its designincludes automatic controls. a steel boiler. and burnerequipment. These features are a big advantage becauseno disassembly is required when you must move theboiler into the field for an emergency.

The Scotch marine boiler has a two-pass (or more)arrangement of tubes that run horizontally to allow theheat inside the tubes to travel back and forth. It also hasan internally fired furnace with a cylindrical combustionchamber. Oil is the primary fuel used to fire the boiler;however. it can also be fired with wood, coal, or gas. Amajor advantage of the Scotch marine boiler is that itrequires less space than a water-tube boiler and can beplaced in a room that has a low ceiling.

The Scotch marine boiler also has disadvantages.The shell of the boiler runs from 6 to 8 feet in diameter, adetail of construction that makes a large amount ofreinforcing necessary. The fixed dimensions of theinternal surface cause some difficulty in cleaning thesections below the combustion chamber. Anotherdrawback is the limited capacity and pressure of theScotch marine boiler.

An important safety device sometimes used is thefusible plug that provides added protection againstlow-water conditions. In case of a low-water condition.the fusible plug core melts, allowing steam to escape, anda loud noise is emitted which provides a warning to theoperator. On the Scotch boiler the plug is located in thecrown sheet, but sometimes it is placed in the upper backof the combustion chamber. Fusible plugs are discussedin more detail later in this chapter.

Access for cleaning, inspection, and repair of theboiler watersides is provided through a manhole in thetop of the boiler shell and a handhold in the water leg. Themanhole opening is large enough for a man to enter the

Figure 1-1.—Scotch marine type of fire-tube boiler.

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boiler shell for inspection, cleaning, and repairs. On suchoccasions, always ensure that all valves are secured,locked, tagged, and that the person in charge knows youare going to enter the boiler. Additionally, always have aperson located outside of the boiler standing by to aid youin case of an incident occurring that would require you toneed assistance. The handholds are openings large

enough to permit hand entry for cleaning, inspection, andrepairs to tubes and headers. Figure 1-2 shows a

horizontal fire-tube boiler used in low-pressureapplications. Personnel in the Utilitiesman rating are

assigned to operate and maintain this type of boiler moreoften than any other type of boiler.

Vertical-Tube Boiler

In some fire-tube boilers, the tubes run vertically, asopposed to the horizontal arrangement in the Scotchboiler. The VERTICAL-TUBE boiler sits in an uprightposition, as shown in figure 1-3. Therefore, the productsof combustion (gases) make a single pass, travelingstraight up through the tubes and out the stack. Thevertical fire-tube boiler is similar to the horizontalfire-tube boiler in that it is a portable, self-contained unitrequiring a minimum of floor space. Handholds are alsoprovided for cleaning and repairing. Thoughself-supporting in its setting (no brickwork or foundationbeing necessary), it MUST be level. The vertical

1. VENTS 7. WATER LEVEL GAUGE2. AIR DAMPER 8. BURNER SWlTCH3. HIGH-LIMIT PRESSURE CONTROL 9. PRIMING TEE4. STEAM PRESSURE GAUGE 10. OIL UNIT, TWO STAGE5. GAUGE GLASS SHUTOFF COCK 11. SOLENOID OIL VALVE (Maintenance)6. LOW-WATER CONTROL 12. SERVICE CONNECTION BOX

13. FUEL OIL SUPPLY CONNECTION14. FUEL OIL PRESSURE GAUGE15. IGNITION CABLE16 IGNITION CABLE17. NAMEPLATE18. BLOWER MOTOR

UTB2f0102

Figure 1-2.—Horizontal fire-tube boiler used in low-pressure applications.

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fire-tube boiler has the same disadvantages as that of thehorizontal-tube design—limited capacity and furnacevolume.

Before selecting a vertical fire-tube boiler, you mustknow how much overhead space is in the building whereit will be used. Since this boiler sits in an uprightposition, a room with a high ceiling is necessary for itsinstallation.

The blowdown pipe of the vertical tire-tube boiler isattached to the lowest part of the water leg. and thefeedwater inlet opens through the top of the shell. Theboiler fusible plug is installed either (1) in the bottomtube sheet or crown sheet or (2) on the outside row oftubes, one third of the height of the tube from the bottom.

Horizontal Return Tubular Boiler

In addition to operating portable boilers, such as theScotch marine and vertical fire-tube boilers. theUtilitiesman must also be able to operate stationaryboilers, both in the plant and in the field. ASTATIONARY BOILER can be defined as one having apermanent foundation and not easily moved or relocated.A popular type of stationary fire-tube boiler is theHORIZONTAL RETURN TUBULAR (HRT) boilershown in figure 1-4.Figure 1-3.—Cutaway view of a vertical fire-tube boiler.

Figure 1-4.—Horizontal return tubular (HRT) fire-tube boiler.

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The initial cost of the HRT boiler is relatively lowand installing it is not too difficult. The boiler setting canbe read i ly changed to mee t d i f f e ren t fue lrequirements—coal, oil, wood, or gas. Tube replacementis also a comparatively easy task since all tubes in theHRT boiler are the same in size, length, and diameter.

The gas flows in the HRT boiler from the firebox tothe rear of the boiler. It then returns through the tubes tothe front where it is discharged to the breaching and outthe stack.

The HRT boiler has a pitch of 1 to 2 inches to the rearto allow sediment to settle toward the rear near the bottomblowdown connection. The fusible plug is located 2inches above the top row of tubes. Boilers over 40 inchesin diameter require a manhole in the upperpart of theshell. Those over 48 inches in diameter must have amanhole in the lower, as well as in the upper, part of theshell. Do not fail to familiarize yourself with the locationof these and other essential parts of the HRT boiler. Theknowledge you acquire will definitely help in theperformance of your duties with boilers.

Firebox Boiler

Another type of fire-tube boiler is the FIREBOXboiler that is usually used for stationary purposes. A splitsection of a small firebox boiler is shown in figure 1-5.

Gases in the firebox boiler make two passes through thetubes. Firebox boilers require no setting except possiblyan ash pit for coal fuel. As a result, they can be quicklyinstalled and placed in service. Gases travel from thefirebox through a group of tubes to a reversing chamber.They return through a second set of tubes to the flueconnection on the front of the boiler and are thendischarged up the stack.

Q6.

Q7.

Q8.

What are the two types of boilers?

What are the four types office-tube boilers?

What is the primary factor that allows the fireboxboiler to be quickly installed and placed intoservice?

BOILER FITTINGS AND ACCESSORIES

Learning Objective: Describe the function andoperation of the different types of boiler fittings andaccessories.

Now that the basic structure of a boiler has beenexplained, boiler fittings (fig. 1-6) and the operation orfunction of various devices, such as controls, valves, andtry cocks, must be presented. A sufficient number ofessential boiler fittings and accessories are discussed inthis section to provide a background for further study. Asa reminder, and in case you should run across some unit

Figure 1-5.—Split section of a small firebox boiler.

1-7

Figure 1-6.—Boiler fittings.

or device not covered in this text, check the manu-facturer's manual for information on details of itsconstruction and method of operation.

The term fittings include various control devices onthe boiler. Fittings are vitally important to the economyof operation and safety of personnel and equipment. Youmust understand fittings if you are to acquire skill in theinstallation, operation, and servicing of steam boilers.

All boilers require boiler fittings to operate safely.The American Society of Mechanical Engineers (ASME)requires all boiler fittings to be made of materials thatwithstand the pressure and temperatures that boilers aresubject to. All of the boiler fittings discussed areimportant and must be operated and maintained properlyto operate a boiler safely.

AIR COCK

An air cock is located in the uppermost steam spaceof a boiler, as shown in item 7 in figure 1-6. This designallows for air to enter and escape during filling anddraining of the boiler. Before firing a cold boiler with nosteam pressure, the air cock is opened to allow air toescape during the heating of the water. When steambegins to come out of the air cock piping, close the valve.

CHIMNEYS, DRAFT FANS, ANDBREECHINGS

Chimneys are necessary for discharging the productsof combustion at an elevation high enough to complywith health requirements and to prevent a nuisance

because of low-flying smoke, soot, and ash. A boilerneeds a draft to mix air correctly with the fuel supply andto conduct the flue gases through the complete setting.The air necessary for combustion of fuel cannot besupplied normally by a natural draft. Therefore, draftfans may be used to ensure that the air requirements areproperly attained. Two types of draft fans used on boilersare forced-draft and induced-draft fans. They are dampercontrolled and usually are driven by an electric motor.

The FORCED-DRAFT fan forces air through thefuel bed, or fuel oil burner, and into the furnace to supplyair for combustion. The INDUCED-DRAFT fan drawsgases through the setting, thus facilitating their removalthrough the stack. Breechings (see item 1 in fig. 1-6) areused to connect the boiler to the stack. They are usuallymade of sheet steel with provision for expansion andcontraction. The breaching may be carried over theboilers, in back of the setting, or even under the boilerroom floor. Keep breechings as short as possible and freefrom sharp bends and abrupt changes in area. Thecross-sectional area should be approximately 20 percentgreater than that of the stack to keep draft loss to aminimum. A breaching with a circular cross sectioncauses less draft loss than one with a rectangular orsquare cross section.

BLOWDOWN VALVES

Blowdown valves on boilers are located on the watercolumn and on the lowest point of the water spaces of theboiler (see items 2, 5, 10, and 11 in fig. 1-6). The blowdownvalves on a boiler installed at the bottom of each water

1-8

drum and header are used to remove scale and otherforeign matter that have settled in the lowest part of thewater spaces. Boilers are also blown down to controlconcentration ofdissolved and suspended solids in boilerwater. The water column blowdown permits removal ofscale and sediments from the water column.Additionally, some boilers have what is called a surfaceblowdown. The surface blowdown is located at theapproximate water level so as to discharge partial steamand water. The surface blowdown removes foaming onthe top of the water surface and any impurities that are onthe surface of the water.

FUSIBLE PLUGS

FUSIBLE PLUGS are used on some boilers toprovide added protection against low water. They areconstructed of bronze or brass with a tapered hole drilledlengthwise through the plug. They have an even taperfrom end to end. This tapered hole is filled with alow-melting alloy. consisting mostly of tin. There are twotypes of fusible plugs—fire actuated and steam actuated.

The FIRE-ACTUATED plug is filled with an alloyof tin, copper. and lead with a melting point of 445°F to450°F. It is screwed into the shell at the lowestpermissible water level. One side of the plug is in contactwith the tire or hot gases, and the other side is in contactwith the water (see item 9). As long as the plug is coveredwith water, the tin does not melt. When the water leveldrops below the plug, the tin melts and blows out. Oncethe core is blown out, a whistling noise will warn theoperator. The boiler then must be taken out of service toreplace the plug.

The STEAM-ACTUATED plug is installed on theend of a pipe outside the drum. The other end of the pipe.which is open, is at the lowest permissible water level inthe steam drum. A valve is usually installed between theplug and the drum. The metal in the plug melts at atemperature below that of the steam in the boiler. Thepipe is small enough to prevent water from circulating init. The water around the plug is much cooler than thewater in the boiler as long as the end of the pipe is belowthe water level. However, when the water level dropsbelow the open end of the pipe, the cool water runs out ofthe pipe and steam heats the plug. The hot steam meltsand blows the tin out, allowing steam to escape from theboiler warning the operator. This type of plug can bereplaced by closing the valve in the piping. It is notnecessary to take the boiler out of service to replace theplug.

Fusible plugs should be renewed regularly once ayear. Do NOT refill old casings with new tin alloy anduse again. ALWAYS USE A NEW PLUG.

WATER COLUMN

A WATER COLUMN (fig. 1-7) is a hollow vesselhaving two connections to the boiler. Water columnscome in many more designs than the two shown in figure1-7; however, they all operate to accomplish the sameprinciple. The top connection enters the steam drum ofthe boiler through the top of the shell or drum. The waterconnection enters the shell or head at least 6 inches belowthe lowest permissible water level. The purpose of thewater column is to steady the water level in the gaugeglass through the reservoir capacity of the column. Also,the column may eliminate the obstruction on smalldiameter, gauge-glass connections by serving as asediment chamber.

The water columns shown are equipped with high-and low-water alarms that sound a whistle to warn theoperator. The whistle is operated by either of the twofloats or the solid weights shown in figure 1-7.

Water Level Control

The water level control not only automaticallyoperates the boiler feed pump but also safeguards theboiler against low water by stopping the burner. Varioustypes of water level controls are used on boilers. AtSeabee activities, boilers frequently are equipped with afloat-operated type, a combination float and mercuryswitch type, or an electrode probe type ofautomatic waterlevel control. Each of these types is described below.

The FLOAT-OPERATED TYPE of feedwatercontrol, similar in design to the feedwater control shownin figure 1-8, is attached to the water column. Thiscontrol uses a float, an arm, and a set of electricalcontacts. As a low-water cutoff, the float rises or lowerswith the water level in an enclosed chamber. Thechamber is connected to the boiler by two lines, whichallow the water and steam to have the same level in thefloat chamber as in the boiler. An arm and linkageconnects the float to a set of electrical contacts thatoperate the feedwater pump when the water lowers thefloat. When the water supply fails or the pump becomesinoperative and allows the water level to continue todrop, another set of contacts operates an alarm bell,buzzer, or whistle, and secures the burners.

The COMBINATION FLOAT AND MERCURYSW ITCH TYPE of water level control shown in figure 1-8

1-9

Figure 1-7.—Typical water columns.

Figure 1-8.—Combination float and mercury switch type offeedwater control.

reacts to changes made within a maintained water levelby breaking or making a complete control circuit to thefeedwater pump. It is a simple two-position type control,having no modulation or differential adjustment orsetting. As all water level controllers should be, it is

wired independently from the programmer. The controlis mounted at steaming water level and consists of apressurized float, a pivoted rocker arm, and acradle-attached mercury switch. The combination floatand mercury switch type of water level control functionsas follows: As the water level within the boiler tends todrop, the float lowers. As the float lowers, the position ofthe mercury switch changes. Once the float drops to apredetermined point, the mercury within the tube runs toits opposite end. This end contains two wire leads, andwhen the mercury covers both contacts, a circuit iscompleted to energize the feedwater pump. The pump,being energized, admits water to the boiler. As the waterlevel within the boiler rises, the float rises. As the floatrises, the position of the mercury switch changes. Oncethe float rises to a predetermined point, the mercury runsto the opposite end of its tube, breaking the circuitbetween the wire leads and securing the feedwater pump.The feedwater pump remains off until the water levelagain drops low enough to trip the mercury switch.

1-10

The ELECTRODE PROBE TYPE of feedwatercontrol (fig. 1-9) and low-water cutoff consists of anelectrode assembly and a water level relay. The electrodeassembly contains three electrodes of different lengthscorrespondin g to high. low, and burner cutout in theboiler drum.

To understand the operation of a boiler circuit, referto figures 1-9 and 1-10 as you read the information intable 1-1. Although this information is not complete. it ispresented here to acquaint you with the operation of theelectrode type of boiler water level control.

Try Cocks

The location of the try cocks is shown as item 6 infigure 1-6. The purpose of the try cocks is to prove thewater level in the boiler. You may see water in the gaugeglass. but that does not mean that the water level is at thatposition in the boiler. lf the gauge glass is clogged up. thewater could stay in the glass giving a false reading. Thetry cocks, on the other hand, will blow water. steam. or amixture of steam and water out of them when they are

Figure 1-9.—Electrode type of water level control.

manually opened. When steam is discharged from thelowest try cock, you have a low-water condition.

Table 1-1.—Operation of a Boiler Circuit

Operation A c t i o n Results

When the feed pump switch The feed pump motor is The feed pump will operate under control of theis in the auto position. energized. water level relay (item #6 in fig. 1-10).

When the water level in the The c i r cu i t t h rough the All of the CONTACTS labeled #6 change position.boiler reaches the level of electrode is grounded and this The three feed pump contacts that are normallyelectrode #3. completes the circuit. closed, i.e., 6-1, 6-2, and 6-3 open, and contact 6-4

closes which maintains the grounded circuit throughelectrode #2.

When the water level falls The circuit through relay #6 This de-energizes relay #6, so all of the CONTACTSbelow electrode #2. will no longer be grounded labeled #6 return to their normal positions. Contacts

because the water is not in 6-1 through 6-3 close and 6-4 opens. The feedwatercontact with the electrode. pump is energized and water is pumped into the

boiler.

When the water level rises Relay #6 will energize again. The cycle continues and the water level in the boileragain to electrode #3. is maintained.

When the water level falls Relay #5 will be de-energized. CONTACT 5-1 will open. This action de-energizesbelow electrode #1. the entire control circuit. The boiler is now shut

down and the low-water alarm is sounded.

1-11

Figure 1-10.—A typical boiler circuit.

WARNING

When the water level is proved using thetry cocks, personnel should stand off tothe side of the try cocks away from thedischarge. The discharged hot steam orvery hot water can cause severe burns.

Gauge Glass

The gauge glass is located on the water column, asshown in figure 1-6, item 3. The gauge glass allows theboiler operator to see the water level in the boiler.Normally there are two valves associated with the gaugeglass. One valve is located at the top and one is located atthe bottom of the gauge glass. These two valves, namedgauge cock valves (fig. 1-6, item 2). secure the boilerwater and steam from the gauge glass. Another valve (fig.1-6, item 4) located in line with the gauge glass, is used toblow the gauge glass down.

SAFETY VALVE

The SAFETY VALVE shown in figure 1-11 is themost important of boiler fittings. It is designed to openautomatically to prevent pressure in the boiler fromincreasing beyond the safe operating limit. The safetyvalve is installed in a vertical position and attacheddirectly to the steam space of the boiler. The location can

be seen in figure 1-6, item 8. Each boiler has at least onesafety valve; when the boiler has more than 500 squarefeet of heating surface, two or more valves are required.

Figure 1-11.—A spring-loaded safety valve.

1-12

There are several different types of safety valves in usebut all are designed to open completely (POP) at aspecific pressure and to remain open until a specifiedpressure drop (BLOWDOWN) has occurred. Safetyvalves must close tightly. without chattering, and mustremain tightly closed after seating.

To understand the difference between boiler safetyvalves and ordinary relief valves is important, Theamount ofpressure required to lift a reliefvalve increasesas the valve lifts, because the resistance of the springincreases in proportion to the amount of compression.When a relief valve is installed on a steam drum, it opensslightly when the specified pressure was exceeded; asmall amount of steam is discharged; and then the valvecloses again. Thus a relief valve on a steam drum isconstantly opening and closing; this repeated actionpounds the seat and disk and causes early failure of thevalve. Safety valves are designed to open completely at aspecified pressure to overcome this difficulty.

Several different types of safety valves are used onboilers; however, they all lift on the same generalprinciple. In each case, the initial lift of the valve disk, orfeather, is caused by static pressure of the steam actingupon the disk. or feather. As soon as the valve begins toopen, however, a projecting lip, or ring, of the larger areais exposed for the steam pressure to act upon. Theresulting increase in force overcomes the resistance ofthe spring. and the valve pops; that is, it opens quicklyand completely. Because of the larger area nowpresented, the valve reseats at a lower pressure than thatwhich caused it to lift originally.

Lifting levers are provided to lift the valve from itsseat (when boiler pressure is at least 75 percent of that atwhich the valve is set to pop) to check the action and toblow away any dirt from the seat. When the lifting leveris used, raise the valve disk sufficiently to ensure that allforeign matter is blown from around the seat to preventleakage after being closed.

The various types of safety valves differ chiefly as tothe method of applying compression to the spring, themethod of transmitting spring pressure to the feather, ordisk, the shape of the feather. or disk, and the method ofblowdown adjustment. Detailed information on theoperation and maintenance of safety valves can be foundin the instruction books furnished by the manufacturersof this equipment.

STEAM INJECTOR FEED SYSTEM

The STEAM INJECTOR (fig. 1- 12) is a boiler FEEDPUMP that uses the velocity and condensation of a jet ofsteam from the boiler to lift and force a jet of water into

Figure 1-12.—A cross-sectional view of a steam injector.

the boiler. This injection of water is many times theweight of the original jet of steam.

The injector is used to some extent in boiler plants asan emergency or standby feed unit. It does not feed veryhot water. Under the best conditions, it can lift a stream ofwater (that has a temperature of 120°F) about 14 feet.

The installation of an injector is not a difficultoperation because the unit is mounted on the side of theboiler. The four connections (fig. 1-13) to the injector areas follows:

1. The discharge line to the boiler feedwater inlet

Figure 1-13.—Injector piping.

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2 . The steam supply line from the boiler

3 . The water overflow line

4. The water supply line from the reservoir

The controls for the injector (fig. 1-13) include thefollowing:

A. Steam supply valve

B. Water supply valve

C. Discharge valve to the boiler

D. Check valve in the discharge line

As you might expect. some degree of skill is neededto start the injector. After the injector begins to operate.however, it continues automatically until shutdown bythe operator.

When starting the injector. first open the watersupply valve (fig. 1-13B) about one full turn. Nestquickly turn the steam supply valve (fig. 1-13A) all theway open. At this point, steam rushes into the combiningtube of the injector As the steam speeds past the watersupply opening. it creates a suction that draws waterthrough the opening into the combining tube. Water andsteam are now mixed together inside the injector and thepressure opens a valve that leads to the boiler.Meanwhile. there is an excess of water in the injector; thisexcess is discharged through the overflow valve. As thenest step of the procedure, slowly turn the water supplyvalve (fig. 1-13B) toward the closed position until theoverflow stops. The overflow valve has now closed andall of the water being picked up from the supply line isgoing into the boiler. Remember, this feedwater systemis used on boilers only as a standby method for feedingwater.

The water supply should not be hotter than 120°F forthe injector to operate. When several unsuccessfulattempts are made to operate the injector. it will becomevery hot and cannot be made to prime. When you shouldencounter this problem. pour cold water over the injectoruntil it is cool enough to draw water from the supply whenthe steam valve is opened.

HANDHOLES AND MANHOLES

Handholds and manholes provide maintenancepersonnel access into a boiler to inspect and clean itinternally as needed. These handholds and manholes willbe covered in depth when boiler maintenance isdiscussed later in this volume.

BOILER ACCESSORIES

Figure 1-14 provides a graphic presentation ofimportant boiler accessories. Refer to it as you study thetable 1-2 which gives a brief description of eachaccessory, its location, and function.

Learning Objective: Identify the automatic controlscommonly used on boilers and describe the function ofeach.

Automatic controls are a big asset since they reducemanual control of the furnace. boilers. and auxiliaryequipment. For this reason. Utilitiesman personnelshould be able to recognize and understand the basicoperations of different types of boiler operating controls.The types of controls the Utilitiesman should becomefamiliar with are as follows: float. pressure, combustion.flame failure. and operation controls.

FLOAT CONTROL

The float in a boiler control works on the same basicprinciple as the float in a flush-tank type of water closet.Float, or level, control depends on the level of fluid in atank or boiler to indicate the balance between the flow outof and the flow into the equipment and to operate acontroller to restore the balance.

A float is often used to measure the change in fluidlevel and to operate the controlled valve to restore thebalance. It may be arranged to increase the flow when thefluid level drops. Figure 1-15 shows one of the methodsused to accomplish this. Here, the float is connected to thecontrol valve.

Q9. Blowdown valves are installed at what location ina boiler?

Q10. How often should the fusible plugs in a boiler berenewed?

Q11. The two connections to the boiler of a watercolumn are at what locations?

Q12. What are the three types of water level controlsmost often encountered by Seabees?

Q13. The electrode probe type of feedwater control haswhat total number of electrode sensors?

Q14. What boiler fitting is considered the mostimportant?

Q15. What is the function of the guard valve on a boiler?

AUTOMATIC CONTROLS

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Table 1-2.—Boiler Accessories, Its Location, and Function

ITEM ACCESSORY LOCATION PURPOSE

1

2

3

4

5

6

7

8

9

Boiler Boiler room Generate steam or hot water in aclosed vessel

Main steam stop On the steam outlet of a boiler Place the boiler on line or off line

Guard valve On the steam outlet of a boiler Guard or backup to the main steam-directly following the main steam- stop valvestop valve

Daylight (drain) valve Between the main steam-stop valve Open only when the main steam andand the guard valve guard valves are closed. Indicates if

one of the valves is leaking through

Main steam line The line that conveys steam from a Carry steam from the boiler to theboiler to all branch or distribution branches or distribution lineslines. When a system is supplied bya bank of boilers connected into thesame header, the line(s) conveying

steam for the boiler(s) to the header

Root valve Installed in branch or distribution Isolate a branch or distribution linelines just off of the main steam line (serves as an emergency shutoff)

Pressure regulating valve Installed as close as practical (after a Equipment that requires lower(PRV) reducing station) to the equipment or pressure than main steam line

area it serves pressure (coppers, dishwashers,steam chest, turbines, etc.)

Steam trap Installed on the discharge side of all Automatically drains condensates t e a m h e a t i n g o r c o o k i n g and prevents the passage of steamequipment, dead ends, low points, or through equipmentat regular intervals throughout asteam system (automatic drip legs)

Drip legs Provided throughout a system where Remove condensate from a systemcondensation is most likely to occur, manuallysuch as low spots, bottom of risers,and dead ends

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Table 1-2.—Boiler Accessories, Its Location, and Function—Continued

ITEM ACCESSORY LOCATION PURPOSE

10

11

12

13

14

15

16

17

18

19

Temperature regu-lating valve (TRV)

Heat exchanger

Strainer

Condensate line

Condensate/makeuptank

Feed pump

Feedwater pipe

Relief valve

Feed check valve

Feed stop valve

Install in the steam supply line close toequipment needing temperatureregulation (sensing element is installedat a point where the temperature is to becontrolled, such as the hot- waterdischarge side of a heat exchanger

Locate as close as practical to thesource for which it is going to supplyheated water or oil

Install in steam and water lines justahead of PRVs, TRVs, steam traps, andpumps

Return line extends from the discharges i d e o f s t e a m t r a p s t o t h econdensate/makeup feedwater tank

Close to the boiler as practical and at ahigher level than the boiler feed-pumpsuction line

Supplies water to the boiler as required

This line extends from the dischargeside of the feedwater pump to the boilershell or drum (installed below thesteaming water level)

Between the feed pump and the nearestshutoff valve in the external feed line

Between the feed pump and the stopvalve in the feed-water pipe

In the feedwater line as close to theboiler as possible between the boilerand feed check valve

Control steam flow through a vessel or

heating equipment

An unfired pressure vessel that containsa tube nest or electrical element. Used

to heat oil or water

Prevent malfunctions or costly repairsto equipment and com- ponents bytrapping foreign matter, such as rust,scale, and dirt

Carry condensed steam back throughpiping for reuse in the boiler or heatingvessel

Provide storage space for condensateand makeup/feedwater and ventnoncondensable gases to the atmosphere

Installed between the condensate/makeup/feedwater tank and the boilersheall or steam drum

Provide feedwater to the boiler whenrequired

Relieve excessive pressure should theexternal feed line be secured and thefeed pump started accidently. Aruptured line or serious damage to thefeed pump could occur if there were norelief valve

Prevent backflow from the boilerthrough the feedwater line into the

condensate/feedwater tank during theoff cycle of the pump

Permit or prevent the flow of water tothe boiler

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Figure 1-14.—Boiler accessory equipment.

Figure 1-15.—Float controller.

PRESSURE-REGULATING CONTROL

Pressure regulating is the process of maintaining adifference of pressure between two points in a system.One type of pressure regulating maintains a definite

pressure in one part of the system, while the other partfluctuates or changes within certain limits. An exampleof this type of control is a pressure-regulator valve (fig.1-16) that maintains a definite pressure on the dischargeside of the valve by controlling the flow of steam, air, orgas through the valve.

A second type of regulator maintains a definitedifference in pressure between two points and alsocontrols the flow. This type of regulator is often appliedto a boiler feeding to maintain a fixed difference betweenthe pressure of water supplied at the feed valve and thepressure in the boiler steam drum. The pressure regulatormay consist of a self-contained device that operates theregulating valve directly, or it may consist of apressure-measuring device, such as a Bourdon-tubegauge, that operates a pilot or relay valve. The valvepositions the regulating valve or mechanism to maintainthe desired conditions.

Pressure controls (fig. 1-17) are designed primarilyfor steam-heating systems but are also available forcontrolling air, liquids, or gases that are not chemicallyinjurious to the control. The function of the pressurecontrol is as follows:

To control the pressure in the boiler

1-17

Figure 1-16.—Pressure regulator.

Figure 1-17.—Typical pressure control with a differentialfrom 0 to 10 pounds.

To secure the fuel-burning equipment when thepressure reaches a predetermined cutout

To start the fuel-burning equipment when thepressure drops to the cut-in point

There are two settings on the pressure control—thecut-in point and the differential. To find the cut-out point,you add the differential to the cut-in pressure; for example,when you were operating a boiler with a cut-in pressure of90 pounds and a differential of 13 pounds, the cut-outpressure should be 103 pounds. When excessive vibrationsare encountered, you should mount the pressure controlremotely from the boiler on a solid mounting with asuitable piping connection between them. When a mercurytype of switch control is used, be sure that it is mountedlevel and that the siphon (pigtail) has the loop extending inthe direction of the back of the control and at a 90-degreeangle to the front, as shown in figure 1-18. This positionprevents expansion and contraction of the siphon fromaffecting the mercury level and accuracy of the control.Additionally, when you install any pigtail, ensure the tubeis filled with water. The water will prevent hot steam fromcontacting the control.

The pressure control can be mounted either on a teealong with the pressure gauge on the pressure-gaugetapping, as shown in figure 1-18, or it can be mounted onthe low-water cutout provided by some manufacturers.In either case, be sure that the pipe dope does NOT enterthe control. The procedure you should follow is to applythe dope to the male threads, leaving the first two threadsbare.

Figure 1-18.—A typical steam gauge installation.

1-18

COMBUSTION CONTROL

Combustion control is the process of regulating themixed flow of air and fuel to a furnace as necessary tosupply the demand for steam. A modulating pressuretrolcontrols the movement of the modutrol motor which, inturn. opens or closes the oil valve and air shutters to adjustthe rate of firing to suit the demands of the boiler.

A modulating motor (fig. 1-19) consists of the motorwindings, a balancing relay, and a balancingpotentiometer, The loading is transmitted to the windingthrough an oil-immersed gear train from the crank arm.The crankshaft is the double-ended type, and the crankarm may be mounted on either end of the motor. Themotor works with the potentiometer coil in themodulating pressuretrol. An electrical imbalance iscreated by pressure change signals to the pressuretrol.This causes the motor to rotate in an attempt to rebalancethe circuit. The crank arm, through linkage, positions theburner air louvers and the oil regulating valve,maintaining a balanced flow of air and oil throughout theburner firing range.

Another process of controlling, combustion air is touse a manually adjusted air damper. A centrifugalblower, mounted on the boiler head and driven by theblower motor, furnishes combustion air. A definiteamount of air must be forced into the combustionchamber to mix with the atomized oil to obtain efficientcombustion. In operation, a pressure is built up in theentire head and the secondary air is forced through adiffuser to mix thoroughly with the atomized oil ascombustion takes place.

The combustion airflow diagram in figure 1-20shows a cutaway view of those components thatinfluence most the path of the air through the burnerassembly. Air is drawn into the motor-driven blowerthrough the adjustable air damper at (A) and forced

Figure 1-19.—A modulating motor.

through openings (B) into the air box. Sufficient pressureis built up to force the air through openings (C) and thediffusor (D). In the area immediately beyond the diffusor(D), combustion is completed. The hot gaseous productsof combustion are forced on through the remaining threepasses where they give up a large portion of the heatcontained to the water which completely envelopes thepasses.

The rate at which combustion air is delivered can bechanged by throttling the intake to the blower by openingor closing the air damper to obtain the exact rate ofairflow required for complete combustion. Since the rateat which fuel is delivered is predetermined by the designand is not readily adjustable, setting of the air damper isthe only means of obtaining the correct ratio of fuel to airto ensure the most efficient combustion.

A pressure-regulating valve is built into the pumpthat controls the fuel. The fuel pump (fig. 1-21) contains atwo-stage gear-type pump, a suction strainer, apressure-regulating valve, and a nozzle cutoff valve, allassembled in a single housing. Knowledge of thefunctional relationship of the component parts can begained by studying the internal oil flow diagram shown infigure 1-22. Observe that the two-stage fuel unit consistsessentially of two pumps operating in tandem andarranged in a common housing. The first stage develops apressure below the atmospheric pressure level at its inletthat causes the oil to flow from storage or supply to thestrainer chamber reservoir. All air drawn into the unitrises to the top of this chamber. This air and excess oil aredrawn into the first-stage-pumping element and pumpedback to the fuel oil storage tank. The second stagewithdraws air-free oil from the strainer chamberreservoir and raises the oil pressure to that required forproper atomization at the burner nozzles. The secondstage, operating against a combination pressureregulating and nozzle cutoff valve, develops atomizingpressure because of the flow restriction imposed by thisvalve. The pressure-regulating valve also bypassesexcess second-stage oil back to the bottom of the strainerchamber reservoir. The atomizing pressure can be variedwithin a restricted range by adjustment of thespring-loaded pressure-regulating valve. Normalatomizing pressures generally range between 95 and 120pounds per square inch.

An orifice is included in the fuel line to the main oilburner. as shown in figure 1-22. The orifice serves tokeep the oil pressure from experiencing a sudden dropwhen the solenoid oil valve in that line opens. The orificeis commonly built into the solenoid oil valve (fig. 1-22,item 1). Included in the schematic diagram is a photocell

1-19

Figure 1-20.—Airflow diagram.

(3) which, if it sights no flame, reacts to cause a switchingaction that results in shutting down the burner.

FLAME FAILURE AND OPERATIONALCONTROLS

Frequently on fully automatic boilers, you will findan electronic type of device provided for the control offlame failure. The device provides automatic start andoperation of the main burner equipment. Some controlsare designed to close all fuel valves, shut down the burnerequipment within 4 seconds after a flame failure. andactuate an alarm. Some controls also create a safetyshutdown within 4 seconds after de-energization ofignition equipment when the main burner flame is notproperly established or fails during the normal startingsequence. These controls must create a safety shutdownwhen the pilot flame is not established and confirmedwithin 7 seconds after lighting. A safety shutdownrequires manual reset before operation can be resumedand prevents recycling of the burner equipment.

Q16.

Q17.

Q18.

Q19.

What is the process of maintaining a difference ofpressure between two points in a systemcalled?

The flow of the air-fuel mixture supplied to thefurnace is regulated by steam demand. What is thisprocess called?

The rate at which combustion air is delivered to theblower can be changed by throttling what device?

Once a safety shutdown of a boiler has occurred,what action must be taken before operations can

resume?

INSTRUMENTS AND METERS

Learning Objective: Identify the instruments and metersused on boilers and describe the function of each.

A pressure gauge is essential for safe operation of aboiler plant. However, the use of additional instruments.

1-20

Figure 1-21.—Fuel oil pump.

such as flowmeters and draft gauges, increases safety andpromotes efficiency. All of these instruments may beeither indicating or recording.

STEAM FLOWMETERS

A Utilitiesman must be able to identify the differenttypes of monitoring instruments and understand theiroperation and use. Meters used to measure quantities aredivided into two general types:

1. Those indicating rate, such as flowmeters

2. Those indicating the total, such as scales

Many devices are designed to measure and indicatethe pressure of steam flow. One of these devices isshown in figure 1-23. This meter uses a weightedinverted bell (called a Ledoux bell) sealed with mercury.The bell moves up and down as the rate of flow changes.The movement is transmitted to a pen that records theflow.

STEAM AND AIR FLOWMETERS

A combustion air and steam flowmeter is shown infigure 1-24. This meter is used as a guide in controllingthe relationship between air required and air actually

supplied to burn the fuel. The rate of steam generation isused as a measure of air necessary to burn the requiredamount of fuel. The flow of gases through the boilersetting is used as a measure of air supplied.

The essential parts of the meter are two airflow bellssupported from knife-edges on a beam, which issupported by other knife-edges, and a mercury displacerassembly supported by a knife-edge on the beam. Thebottoms of the bells are sealed with oil, and the spacesunder the bells are connected to two points of the boilersetting.

DRAFT GAUGES

A draft gauge is a form of pressure gauge. In boilerpractice, the term draft usually refers to the pressuredifference producing the flow. Drafts are pressuresbelow atmospheric pressure. They are measured ininches of water. A draft gauge is essential to boileroperation. Its use increases the safety of operation.

A simple type of draft gauge is the U-tube gauge.The source of draft is connected to one leg of the U andthe other end is left open. The difference between thelevels of the liquid in the two legs is a measure of thedraft. Water is generally used in this type of gauge. Take

1-21

Figure 1-22.—The internal oil flow diagram.

Figure 1-23.—Flowmeter.

1-22

Figure 1-24.—Airflow mechanism of a boiler air flowmeter.

a close look at figure 1-25 that shows a comparison of aninclined-draft gauge and a U-tube gauge.

When one leg of the U tube is arranged on an incline,the distance moved by the liquid in the inclined portion isincreased for a given draft change which makes moreaccurate reading possible.

Two or more draft gauges are required for

economical boiler operation. The gauges inform theoperator of the relative amount of air being supplied toburn the fuel and the condition of the gas passages. Draftgauges are made as indicators, recorders, or both. Themeasuring element uses a column of liquid, a diaphragm,

Figure 1-25.—Comparison of inclined-draft gauge and U-tube gauge.

1-23

or a bellows. The liquids used are oil, water, or mercury.The gauge shown in figure 1-26 is an indicating type thatoperates on the same principle as the U tube (differencebetween the levels of the liquid in the two legs is ameasure of the draft).

The bottom of the inverted bell is sealed with oil ormercury, depending on the magnitude of the draft orpressure to be measured. It is supported by knife-edgeson the beam to reduce friction as much as possible. Theweights counterbalance the weight of the bell. and thepointer is returned to zero. The source of draft isconnected to the tube, which projects into the invertedbell, so an increase in draft causes the pointer to movedown.

CO2 METERS (ANALYZERS)

Figure 1-27 shows one type of carbon dioxide meter.The meters are also known as analyzers and are designedfor determining, indicating, and recording the percentageof CO2 (carbon dioxide) in the products of combustion.The principle of this instrument is based on the fact thatthe specific weight of flue gas varies in proportion to itsCO2 content (CO2 being considerably heavier than theremaining parts of the flue gas).

Q20. Meters are divided into what two generalcategories?

Q21. In reference to boiler operations, what does theterm "draft" mean?

BOILER WATER TREATMENT AND

CLEANING

Learning Objective: Describe the methods andprocedures for the testing of and treatment of boilerwater.

A Utilitiesman must understand the methods, tests,and safety precautions involved in boiler water treatmentand the procedures for cleaning boiler firesides andwatersides. To ensure a boiler operates at peakefficiency, you must treat and clean it. Water testing,treatment. and cleaning go hand-in-hand. The reason forthis is because the effect of the impurities in the water oninterior surfaces determines the method and frequency ofboiler cleaning. In this section, we will discuss therelationships between water testing. treatment. andcleaning and the procedures for each.

WATER IMPURITIES

All natural waters contain acid materials andscale-forming compounds of calcium and magnesiumthat attack ferrous metals. Some water sources containmore scale-forming compounds than others; therefore,some waters are more corrosive than others. Subsurfaceor well waters are generally more scale-forming, whilesurface waters are usually more corrosive. To preventscale formation on the internal water-contacted surfacesof a boiler and to prevent destruction of the boiler metalby corrosion, chemically treat feedwater and boiler

Figure 1-26.—Liquid-sealed draft gauge.

1-24

1. GASKET 6. PLUNGER SEATS. 11. FILTER NIPPLE.2. TOP CAP HOLDING SCREW. 7. CO2 SCALE. 12. CONNECTION SAMPLING TUBE3. TOP CAP 8 SCALE LOCKlNG SCREW. TO FILTER NIPPLE.4. PLUNGER CAP 9. RUBBER ASPIRATOR BULB 13 FILTER TUBE.5. CONNECTOR TIP. 10. BOTTOM OF ANALYZER. 14. CONNECTION TUBING TO

UTB2f0127 SAMPLING TUBE.

Figure 1-27.—CO2 meter (analyzer).

water. This chemical treatment prolongs the useful life ofthe boiler and results in appreciable savings in fuel, sincemaximum heat transfer is possible with no scale deposits.

SCALE

Crystal clear water, satisfactory for domestic use,may contain enough scale-forming elements to render itharmful and dangerous in boilers. Two suchscale-forming elements are precipitates of hardness andsilica.

Scale deposited on the metal surfaces of boilers andauxiliary water heat exchange equipment consists largelyof precipitates of the HARDNESS ingredients—calciumand magnesium and their compounds. Calcium sulfatescale is, next to silica, the most adherent and difficult toremove. Calcium and magnesium carbonates are themost common. Their removal requires tedious handscraping and internal cleaning by power-driven wirebrushes. When deposits are thick and hard, the more

costly and hazardous method of inhibited acid cleaningmust be used. Scale deposits are prevented by thefollowing: removal of calcium and magnesium in thefeedwater to the boiler (external treatment); chemicaltreatment of boiler water (phosphate, organic extracts,etc.); and changing scale-forming compounds to formsoft nonadherent sludge instead of scale that can be easilyremoved from the boiler by blowdown (internaltreatment).

SILICA in boiler feedwater precipitates and forms ahard, glossy coating on the internal surfaces. In thefeedwater of high-pressure boilers, such as those used inelectric generating plants, a certain amount of silicavaporizes under the influence of high pressure andtemperature. The vapor is carried over with steam andsilica deposits on the intermediate and low-pressureblading of turbines. In boilers operating in the range of10- to 125-psig pressure, the silica problem is not sotroublesome. When the water is low in hardness,contains phosphate that prevents calcium silicate scale

1-25

from forming, or has enough alkalinity to keep the silicasoluble. no great difficulty is encountered. The amountof soluble silica can be limited by continuous or routineboiler blowdown to prevent buildup of excessiveconcentrations.

CORROSION

Corrosion control occurs with the problem of scalecontrol. Boilers, feedwater heaters, and associatedpiping must be protected against corrosion. Corrosionresults from water that is acidic (contains dissolvedoxygen and carbon dioxide). Corrosion is prevented byremoving these dissolved gases by deaeration offeedwater, by neutralizing traces of dissolved gases ineffluent of the deaerating heater by use of suitablechemicals. and by neutralizing acidity in water with analkali.

METHODS OF TREATMENT

The specific method of chemical treatment usedvaries with the type of boiler and the specific propertiesof the water from which the boiler feed is derived. Ingeneral, however, the chemical treatment of feedwaterand boiler water is divided into two broad types ormethods-external treatment and internal treatment ofmakeup water for alkalinity control and for removal ofscale-forming materials and dissolved gases (oxygen andcarbon dioxide) before the water enters the boiler."Internal treatment" means that chemicals are putdirectly into the boiler feedwater or the boiler waterinside the boiler. Frequently, both external and internalchemical treatments are used.

External treatment. frequently followed by someinternal treatment, often provides better boiler waterconditions than internal treatment alone. However,external treatment requires the use of considerableequipment, such as chemical tanks, softening tanks, filters,or beds of minerals, and the installation costs are high.Such treatment is therefore used only when the makeupwater is so hard or so high in dissolved minerals or wheninternal treatment by itself does not maintain the desiredboiler water conditions. What is the dividing line betweenthe hardness and the concentration of dissolved matter inwater? What factors other than the dividing line determinethe need for external treatment? These factors are thephysical makeup of the plant. the type and design of theboilers used, the percentage of makeup water being used,the amount of sludge the boiler can handle, the spaceavailable, and the adaptability of the operators. Many

1-26

methods of INTERNAL TREATMENT are in use. Mostof these treatments use carefully controlled boiler wateralkalinity, an alkaline phosphate, and organic material.One of the organic materials used is tannin. Tannin is aboiler water sludge dispersant; that is, it makesprecipitates more fluid and prevents their jelling intomasses that are difficult to remove by blowdown.Because of treatment costs and simplicity of chemicalconcentration control, the alkaline phosphate-tanninmethod of internal treatment is perhaps the most widelyused. When properly applied and controlled, thistreatment prevents formation of scale on internal boilersurfaces and prevents corrosion of the boiler tubes andshell.

BOILER WATER TESTING

As we have just seen. boiler water must be treatedwith chemicals to prevent the formation of scale on theinternal surface of the boiler and to prevent deteriorationof the boiler metal by corrosion. Boiler water must betested to determine the sufficiency of chemical residualsto maintain clean boiler surfaces. As a Utilitiesman, youshould be able to make various boiler water tests (fig.1-28). The procedures for a few types of tests that youmay have to make is given here—tests for hardness.phosphate. tannin. caustic alkalinity (with and withouttannin), sodium sulfite, and pH. A test kit is provided forthe different tests. Each test kit contains the equipmentand materials for the specified test. If a kit is notavailable, you have to use the laboratory equipment (figs.1-29 and 1-30) provided in the boiler or water treatmentplants.

Figure 1-28.—Testing boiler water is an important job.

Figure 1-29.—General laboratory equipment.

CAUTION Test for Hardness

The following caution applies to each

test that is discussed: IF THE TESTING

PROCEDURES OF THE EQUIPMENT

AND/OR REAGENT SUPPLIER

DIFFERS FROM THAT PRESCRIBED

IN THIS TEXT, THE SUPPLIER’S

PROCEDURE SHOULD BE USED.

Boilers operating at pressures of 15 psi and less arenormally used for space heating and hot-watergeneration. Practically all the condensate is returned tothe plant. Only a small amount of makeup is required,and secondary feedwater treatment usually is sufficient.When appreciable quantities of steam are used in processwork and not returned as condensate to the plant, theproblem of scaling and corrosion arises, and more

1-27

Figure 1-30.—General laboratory equipment.

complete treatment of feedwater must be considered. Theideal water for boilers does not form scale or deposits.does not pit feedwater systems and boiler surfaces, anddoes not generate appreciable CO2 in steam. However.such raw makeup water is impossible to get in the naturalstate from wells or surface sources. Does the advantageof treatment make up for the cost of treatment?

Feedwater of 20- to 25-ppm hardness as calciumcarbonate (CaCO3) need not be treated externally toreduce hardness if enough alkalinity is present toprecipitate the hardness in the boiler as CaCO3, or ifhardness reducers, such as phosphates, are introduced tocombine with and precipitate the hardness. Precipitationof this hardness in a low- or medium-pressure boilergenerally does not cause wasteful blowdown. When themixture ofcondensate and makeup in a medium-pressuresteam plant has a hardness greater than 20 to 25 ppm asCaCO3, the hardness should be reduced to a level of 0 to 2ppm as CaCO3.

Feedwater of a hardness in excess of 2 ppm asCaCO3 should be treated to bring it within the range of0 to 2 ppm as CaCO3. This small remaining hardness

can be precipitated in the boiler by secondarytreatment and removed by continuous blowoffequipment.

The test for hardness, as presented here, uses thecalorimetric titration method. This test is based onfinding the total calcium and magnesium content of asample by titration with a sequestering agent in thepresence of an organic dye sensitive to calcium andmagnesium ions. The end point is a color change fromred to blue, which occurs when all the calcium andmagnesium ions are separated.

The following equipment is used for the hardnesstest:

One 25-ml buret, automatic, complete

One 210-ml casserole, porcelain

One 50-ml cylinder, graduated

One stirring rod, glass

The reagents for the test are as follows:

Hardness indicator

1-28

Hardness buffer

Hardness titrating solution

The steps of the hardness test are as follows:

1.

2.

3.

4.

Measure 50 ml of the sample in the graduatedcylinder and transfer it to the casserole.

With the calibrated dropper, add 0.5 ml of thehardness buffer reagent to the sample, and stir.

Add 4 to 6 drops of hardness indicator. Ifhardness is present, the sample will turn red.

Add the hardness titrating solution slowly fromthe burette, and stir continually. Whenapproaching the end point, note that the samplebegins to turn blue, although you can still see adefinite reddish tinge. The end point is the finaldischarge of the reddish tinge. Adding morehardness titrate solution does not producefurther color change.

In using this procedure, add the hardness titratingsolution slowly because the end point is sharp andrapid. For routine hardness determination, measure 50ml of the sample, but add only approximately 40 to 45ml to the casserole at the start of the test. The hardnessbuffer reagent and the hardness indicator should thenbe added as directed and the mixture titrated rapidly tothe end point. The remaining portion of the sampleshould then be added. The hardness in the remainderof the sample will turn the contents of the casserole redagain. Titrating is continued slowly until the final endpoint is reached. A record should be kept of the totalmilliliters of hardness titrating solution used.

To calculate the results in ppm hardness, use thefollowing equation:

ppm hardness = ml titrating solution x 1,000

(CaCO3) (ml sample)

With a 50-ml sample, the hardness in ppm asCaCO3 is equal to the ml of titrating solution used,multiplied by 20.

Test for Phosphate

The calorimetric test for phosphate uses adecolorizing carbon to remove tannin. Carbon absorbsthe tannin, and the carbon and tannin are then filteredout. When tannin is not present, carbon improves thetest for residual phosphate by making the tricalciumphosphate sludge more filterable.

The equipment required for the phosphate test is asfollows:

One phosphate color comparator block of twostandards—30 ppm and 60 ppm of phosphate asPO4. (The Taylor high-phosphate slidecomparator may be used instead.)

Four combination comparator mixing tubes,each marked 5, 15, and 17.5 ml, with stoppers.

One filter funnel, 65-mm diameter.

One package of filter paper, 11 cm in diameter.

One 20-ml bottle.

One 0.5-ml dropper.

One 1/4-tsp measuring spoon or spatula.

Two plain test tubes, 22 mm by 175 mm (about50 ml).

Two rubber stoppers, No. 3 flask.

One 250-ml glass-stoppered bottle or flask,labeled comparator molybdate reagent.

The reagents you need are as follows:

One 32-oz comparator molybdate.

One 2-oz concentrated stannous chloride.

One 32-oz standard phosphate test solution (45ppm of phosphate, PO4).

One pound decolorizing carbon. (This is a specialgrade of decolorizing carbon tested to make sure itdoes not affect the phosphate concentration in thesample.)

For test purposes, the stannous chloride is suppliedin concentrated form. The reagent must be diluted andshould be prepared from the concentrated stannouschloride on the day it is to be used, because the dilutedsolution deteriorates too rapidly for supply by a centrallaboratory. If not fresh, diluted stannous chloridegives low test results. Concentrated stannous chloridealso deteriorates and should not be used if more than2 months old.

The procedure for making diluted stannouschloride is as follows:

1. Fill the 1/2-ml dropper up to the mark with theconcentrated stannous chloride.

2. Transfer it to a clean 20-ml bottle.

3. Add distilled water up to the shoulder of thebottle, then stopper and mix by shaking.

1-29

CAUTION

Any diluted stannous chloride not usedthe day it is made should be discarded.

The following procedure is used to make the testfor phosphate:

1. Without disturbing any settled sludge, transferenough of the sample to the test tube to till it about halffull.

2. Add 1/4 tsp of decolorizing carbon. Stopper thetube and shake vigorously for about 1 minute. Thecarbon absorbs the tannin so it can be filtered out.

3. Fold a filter paper and place it in the filterfunnel. Do not wet down the filter paper with water.Filter the shaken sample, using a combination mixingtube as a receiver. The carbon absorbs tannin, and thetannin and sludge present are filtered out more rapidly.Avoid jiggling the funnel, as unfiltered boiler watermay overflow the edge of the filter paper into the tube.You have to support the funnel.

4. After 5 ml of the sample has filtered through, asindicated by the level in the tube, discard it. Continuefiltering to bring the level in the test tube again up to the5-ml mark. The sample should come through clear andfree, or nearly free, of any color from the tannin. If notnearly free of tannin color. repeat the test, using 1/2 tspof carbon. adding it in two 1/4-tsp portions, shaking itfor 1 minute after each addition.

5. Add the comparator molybdate reagent to bringthe level up to the second mark ( 15 ml). Stopper and mixby inverting the tube several times.

6. Add fresh diluted stannous chloride up to thethird mark (17.5 ml). Stopper and mix by inverting. Ifphosphate is present, the solution in the mixing tubeturns blue.

7. Place the tube in the comparator block.Compare the color of the solution in the tube with thestandard colors of the phosphate color block. Colorsbetween the two standard colors may be estimated.Take the reading within 1 minute after adding thestannous chloride, because the color fades quickly.

8. Record the results as LOW, if below 30 ppm;HIGH, if above 60 ppm, or OK, if between 30 and 60

ppm.

Test for Tannin

The purpose of the TANNIN TEST is to determinethe amount of tannin in the boiler water. Tannin holds

sludge in suspension. In treating boiler water withtannin, control the dosage by the depth of brownformed in the boiler water by the tannin. To estimatethe depth of the color, which is necessary in adjustingtannin dosages, compare a sample of the boiler waterwith a series of brown color standards of successivelyincreased depths of color. A tannin color comparator,which is used for the comparison, has five glass colorstandards: No. 1, very light; No. 2, light: No. 3,medium; No. 4, dark; and No. 5, very dark.

The kit for the tannin test contains the following:

One tannin color comparator

Two square tubes, 13-mm viewing depth

One plain test tube, 22 mm by 175 mm

One filter funnel, 65 mm by 65 mm

One package of filter paper, 11 cm in diameter

making this test, you first fill a plain test tubealmost to the top with cool boiler water. Then place asquare test tube in the slot of the comparator, and insertthe filter funnel in it. Fold a filter paper and place it inthe funnel without wetting it down. Filter water fromthe plain test tube into the square tube until the tube isneatly full. Remove the square tube from thecomparator and hold it up to a good source of naturallight. Note the appearance of the filtered boiler water.Is it free of suspended solids and sludge? If not, refilterthe sample, using the same funnel and filter paper.Repeat, using a double filter paper if necessary, untilthe sample does come through free of suspended solidsand sludge.

To complete the test, place the square tube offiltered sample in the middle slot of the comparator.Then compare the color of the sample with the fivestandards, viewing it against a good source of naturallight. The color standard most closely matching thecolor of the filtered sample gives the tanninconcentration of the boiler water. For a number ofboiler water conditions, the tannin dosage is usuallysatisfactory if it maintains a medium (No. 3) tannincolor. If the tannin color is too high, blow down; if toolow, add tannin.

Test for Caustic Alkalinity (OH) withoutTannin

The boiler water sample for this test is collected ata temperature of 70°F or below.

1-30

The equipment required is as follows:

Two 8-in. droppers with bulbs

Two 250-ml glass-stoppered bottles or flaskslabeled causticity No. 1 and causticity No. 2

Four marked test tubes, 22 mm by 185 mm

Three plain test tubes, 22 mm by 175 mm

Three rubber stoppers, No. 2

One 14-in. test-tube brush

One test-tube clamp

Two 9-in. stirring rods

One 1-oz indicator dropping bott le forphenolphthalein

One test-tube rack

The following reagents also are required:

One 24-oz bottle or flask causticity reagent No. 1

One 24-oz bottle or flask causticity reagent No. 2

One 4-oz bottle phenolphthalein indicator

The following are the steps to follow in conductinga test for causticity when tannin is not used:

CAUTION

Avoid exposure of the sample to the air asmuch as possible to reduce absorption ofthe CO2.

1. Without disturbing the settled sludge, fill amarked test tube exactly to the first mark (25 ml) withsome of the original boiler water sample.

2. Shake causticity reagent No. 1 (barium chloridesolution saturated with phenolphthalein) thoroughly andadd enough to the graduated tube to bring the levelexactly to the second, or long, mark (30 ml).

3. Stir the solution with the 9-inch stirring rod,which must be kept clean and reserved for the causticitytest only. When the mixture remains colorless or doesnot turn pink, the causticity in the boiler water is zero andthe test is finished. When the mixture turns pink,causticity is present. (If the pink color is not deep,intensify it by adding two drops of phenolphthaleinindicator to the mixture in the tube.) Add causticityreagent No. 2 (standard one-thirtieth normal acid), usingthe 8-inch dropper, thatch must be kept clean andreserved for the causticity test only. Causticity reagentNo. 2 is sucked from the reagent bottle into the dropper

by its rubber bulb and added, drop by drop, to the testtube. After each addition, stir the mixture with astirring rod. After sufficient reagent has been added,the pink color disappears; the change point is usuallysharp. As soon as the pink color just fades out, stopadding the reagent.

4. The amount of causticity reagent No. 2required to make the pink color disappear shows theconcentration of hydroxide (OH) or causticity in theboiler water. The amount of reagent used is shown bythe marks on the test tube above the long mark (30 ml).The distance between any two marks on the test tubeequals 5 ml, and readings less than 5 ml can beestimated. For example, when only three fifths of thedistance between the long mark and the next markabove were filled, then 3 ml was added. When thedistance filled was past one mark plus three fifths of thedistance to the next, then 5 + 3 = 8 ml was used. Toobtain the actual ppm of hydroxide or causticity shownby the test, multiply the number of ml by 23. Thisconstant number, 23, represents the amount of sodiumhydroxide in the boiler water by volume. Thus, for 8 mlof causticity reagent No. 2, there are 8 x 23 = 184 ppmhydroxide or causticity in the water.

5. Record the results of the test in a boiler log orchemical log and adjust the range to meetrequirements. When causticity is too high, blow down;if too low, add sodium hydroxide (caustic soda).

Test for Caustic Alkalinity (OH)with Tannin

For this test, start with a warm sample of about160°F. I t may be reheated by placing thesample-collecting container in a stream of hot boilerwater drawn through the boiler water coolerconnection. In a test for causticity when tannin isused, make sure you observe the same precautions ascarefully as when tannin is not used.

CAUTION

Avoid exposure of the sample to the airas much as possible to reduce absorptionof the CO2.

The equipment and reagents required for this testare the same as those listed in the preceding sectionwhere tannin was not used.

1-31

The procedure for conducting a test for causticitywith tannin is as follows:

1. Fill two test tubes to the first mark (25 ml) withsome of the original boiler water sample, taking care notto disturb the settled sludge in the container. (Transferas little sludge as possible from the sample-collectingcontainer to the test tubes.)

2. Shake causticity reagent No. 1 thoroughly andadd enough to each of the two marked tubes to bring thelevels up to the second, or long, mark (30 ml). Stir bothwith the stirring rod, which must be kept clean andreserved for the causticity test only.

3. Stopper both tubes and let them stand until anysludge formed has settled to the bottom. The sludgecarries down with it much of the tannin or other coloredmatter in the solution; settling takes a few minutes if thesample is warm.

4. Without disturbing the sludge at the bottom,pour enough solution from the tubes into the thirdmarked tube to fill it to the second, or long, mark.Discard the mixture left in the first two. When thesample in the third tube is still warm, cool it by lettingcold water run on the outside of the tube. It is sometimespossible to intensify the pink color by adding two dropsof phenolphthalein from the indicator-dropping bottleto the sample in the tube. Stir the solution. When it isnot pink, the causticity in the boiler water is zero.

5. When the sample is not pink, the test is finished.But if the mixture turns pink, proceed in the samemanner as directed in Steps 3, 4, and 5 when no tannin isused.

Here is a brief explanation of an ALTERNATEPROCEDURE for making the test for causticity whentannin is used. In this procedure any glass container,such as a large test tube or graduated cylinder, markedfor 50 to 60 ml can be used instead of the two standardmarked test tubes used in Steps 1 and 2 above. With thelarge test tube or graduated cylinder, the warm (160°F)sample is added up to the 50-ml mark and causticityreagent No. 1 up to the 60-ml mark. Stir the mixtureand stopper the tube, or graduate. After the sludgesettles, pour off enough of the solution into one of thestandard marked test tubes to fill it to the long mark (30ml). When the sample is warm, cool it by letting coldwater run on the outside of the tube. Adding two dropsof phenolphthalein may intensify the pink color.When the solution is not pink, the causticity in theboiler water is zero. But if it turns pink, proceed in thesame manner as in Steps 3, 4, and 5 when no tannin isused.

1-32

Test for Sodium Sulfite

The sample for this test should be cooled to 70°F,or below, and exposed to the air as little as possible,because oxygen in the air combines with sodiumsulfite in the sample and causes low readings. Collect aseparate sample, using the boiler water sample cooler,with the line reading to the bottom of the samplingbottle. Allow the boiler water to run until a fewbottlefuls overflow to waste.

The equipment necessary to make the sodiumsulfite test is as follows:

One 30-ml acid-dropping bottle, with droppermarked at 0.5 ml for hydrochloric acid 3N

One 30-ml starch-dropping bottle, with droppermarked at 0.5 ml for starch indicator

One 150-ml beaker

One stopper for plain test tube

One stirring rod

One 8-in. dropper

One 1/4-measuring tsp

One 50-ml beaker

Two plain test tubes

Two marked test tubes

The reagents required are as follows:

One 2-oz bottle of potato, or arrowroot starch

One 8-ml vial of thymol

One 24-oz bottle of hydrochloric acid 3N

One 1-pt amber bottle of standard potassiumiodate-iodide reagent

The starch indicator for this test must be preparedlocally. The procedure to adhere for good results is asfollows:

1. Measure out a level one-fourth tsp of potato orarrowroot starch and transfer it to the 50-ml beaker.

2. Add a few milliliters of distilled water and stirthe starch into a thick paste, using the end of the stirringrod.

3. Put 50 ml of distilled water into the 150-mlbeaker. (It is convenient in this step to have the 150-mlbeaker marked at the point where it holds 50 ml, or oneof the marked test tubes can be used by filling it withdistilled water to the fourth mark above the long mark.)

4. Bring the water in the 150-ml beaker to a boil byany convenient method.

5. Remove the source of heat and immediatelypour the starch paste into the boiling water while stirringthe solution.

6. Put a crystal of thymol into the starch solutionand stir. After the solution has cooled, pour off anyscum on the surface and transfer 30 ml to theindicator-dropping bottle.

7. The starch solution loses its sensitivity as anindicator after a time. Addition of the thymol preservesit for about 2 weeks. The starch should be dated whenprepared.

In making the sodium sulfite test, proceed asfollows:

1. Transfer 1 ml of hydrochloric acid 3N to a clean,marked test tube by measuring out 0.5-ml portions withthe dropper of the acid-dropping bottle.

2. From the starch-dropping bottle, transfer 0.5 mlof starch to the marked test tube.

3. Without disturbing any settled sludge in thesample, pour enough of the sample into the marked testtube to bring the level up to the first mark (25-ml). Stirthe mixture in the tube with the plunger end of thestirring rod.

4. To add the standard potassium iodate-iodidereagent to the mixture in the marked test tube, have themarked test tube supported and the stirring rod placed inthe tube, so the reagent can be added with one handwhile the mixture is stirred with the other. Fill the8-inch dropper with standard potassium iodate-iodidereagent from the stock bottle by sucking it up with therubber bulb. (The dropper must be kept clean andreserved for this test only.)

5. Add the reagent to the mixture in the marked testtube, one drop at a time, counting the number of dropsand stirring after each is added until a permanent bluecolor, which is not removed by stirring, is obtained. Thestandard iodate-iodide reagent reacts with sodiumsulfite in the mixture, and the formation of thepermanent blue color from the action of excess reagentwith the starch shows that the iodate-iodide reagent hasconsumed all the sodium sulfite in the mixture.

6. Each drop of iodate-iodide reagent used (exceptthe last one) indicates 5 ppm of sodium sulfite in theboiler water sample. To figure the concentration ofsodium sulfite in the boiler water, multiply the totalnumber of drops of the standard iodate-iodide reagent

used, less one, by 5. For example, when 5 drops wereused, subtract 1 from 5 = 4, 5 x 4 = 20 ppm.

7. Record the results of the test as ppm.

Test for pH

The value of pH indicates the degree of acidity oralkalinity of a sample. A pH of 7.0 represents theneutral point; the lesser values denote acidity; thegreater values denote alkalinity. The test is made assoon as possible after you take the sample. Avoidexposure to the air as much as possible to reduceabsorption of CO2.

The following equipment is used in making the pHtest of boiler water:

One 2-oz bottle

One 50-ml beaker

Two vials of indicator paper, hydrions C pH 11to 12

Two vials of indicator paper, hydrions pH 10 to20

In conducting the test for pH of boiler water,remove a strip of pH 10 to 12 indicator paper from thevial and dip it into the sample in the beaker. Keep thepaper immersed for 30 seconds; then remove it. Whenthe sample does not change the color of the paper orcolors it yellow or light orange, the pH of the sample istoo low and the test is finished. When the paper turnsorange or red, the pH is either satisfactory or too high.

In that case, remove a strip of paper of pH 11 to 12from the vial and dip it into the sample in the beaker.Keep the paper immersed for 30 seconds; then removeit. When the sample does not change the color of thepaper or colors it a light blue, the pH is satisfactory.When the paper turns deep blue, the pH is higher thannecessary. Blow down or reduce the dosage of causticsoda (NaOH).

Test for pH of TreatedCondensate

In making a test for pH of treated condensate, takethe sample from a point in the return piping near whichcondensation takes place, such as after a trap, orpreferably where the return-line corrosion is known tooccur. The sample must represent water flowing in thereturn lines. Water taken from the return tank,especially of large installations, generally shows ahigher pH. A sample should not be taken from a

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collecting tank if other water, such as makeup, isreceived in the tank.

The equipment required for this test is as follows:

One 100-ml beaker, marked at 50 ml

One 1-oz indicator bottle, with dropper markedat 0.5 ml

One 4-oz brown bottle of condensate pHindicator

One 9-in. stirring rod, glass

In making a test for pH of treated condensate,proceed as follows:

1. Pour a freshly drawn sample into the testingbeaker until it is filled to the 50-ml mark. You do nothave to cool the sample.

2. Transfer 0.5 ml of indicator solution to the50-ml testing beaker, using the marked dropper. Stir thesolution in the beaker. If the color of the solutionchanges to light pink. the sample is NEUTRAL, orslightly alkaline; therefore, the condensate pH issatisfactory and the test is over.

3. Record in a log that the pH range is between 7and 7.5.

4. When the color change is green, the sample is inthe acid range and the boiler water must be treated withAmines. Treat the boiler water with Amines gradually(in small amounts at a time), and retest after eachtreatment. Amines are the only chemicals used to treatboiler water that will vaporize and leave with the steamand thereby protect the return system.

WARNING

Permission to treat with Amines must beobtained from your supervisor. Aminesare volatile, poisonous, and in thealkaline range.

6. When the color change is red or purple, thesample is in an excessive alkaline (pH) range. In thatcase, reduce the Amines treatment gradually (in smallamounts at a single time), and retest after eachtreatment. Remember, the condensate pH normalacceptable range is between 7 and 7.5.

Test for Total Dissolved Solids

The solu-bridge method is a simple and rapid wayto determine the total dissolved solids (TDS) content.Ionizable solids in water make the solution conduct

electricity. The higher the concentration of ionizablesalts, the greater the conductance of the sample. Purewater, free from ionizable solids, has low conductanceand thus high resistance. The solu-bridge instrumentmeasures the total ionic concentration of a water sample,the value of which is then converted to parts permillion. The solu-bridge test equipment and reagent arefurnished by the supplier in a kit.

CAUTION

The model of the solu-bridge given belowis not suitable for measuring solids incondensed steam samples or an effluent ofthe demineralizing process. A low-conductivity meter is necessary. becauseof the extremely low solids content ofcondensed steam and demineralized water.

The equipment and reagent are as follows:

One solu-bridge, Model RD-P4 or equivalent, for a105 to 120-volt, 50- to 60-cycle ac outlet. (Thismodel has a range of 500 to 7,000 micromhos/cm.)

One polystyrene dip cell, Model CEL-S2.

One thermometer, 0°F to 200°F.

One 0.1-g dipper for gallic acid.

One cylinder, marked at the 50-ml level.

Gallic acid powder, 1 lb.

Calibration test solution. I qt.

The test is made as follows:

Without shaking, pour 50 ml of the sample into thecylinder. Add 2 dippers of gallic acid powder and mixthoroughly with a stirring rod.

2. Connect the dip-cell leads to the terminals of thesolu-bridge and plug the line cord into a 110-volt ac outlet.Turn the switch ON. and allow the instrument to warm upfor 1 minute.

3. Clean the cell by moving it up and down severaltimes in distilled water. Measure the temperature of thesample to be tested; then set the point of the solu-bridgetemperature dial to correspond to the thermometerreading.

4. Place the cell in the cylinder containing the 50-mlsample. Move the cell up and down several times underthe surface to remove air bubbles inside the cell shield.Immerse the cell until the air vents on the cell shield aresubmerged.

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5. Turn the pointer of the solu-bridge upper dial untilthe dark segment of the tube reaches its widest opening.

6. Calculate the result in ppm by multiplying the dialreading either by 0.9 or by a factor recommended by localinstructions. For example, when the dial reading is4,000 micromhos and the factor used is 0.9, then 4,000 x0.9 = 3,600 ppm.

7.

Q22.

Q23.

Q24.

Q25.

Q26.

Record the results of the test in ppm.

Scale deposited on metal surfaces of’ boilersconsists largely of what scale-forming element?

What are the two broad types or methods ofchemical treatment of‘ boiler water?

Results of a phosphate test would need to bebetween what lower and higher ppm to be at anacceptable level?

In a causticity test without tannin, when themixture turns pink, what does this mean?

A sample of boiler water for a sodium sulfite testshould be cooled to what temperature beforeconducting the test?

CLEANING BOILER FIRESIDES ANDWATERSIDES

Lesson Objective: Describe met hods and proceduresinvolved in fireside and waterside cleaning.

Boiler heat transfer surfaces must be kept clean toprovide for safe and economical boiler operation. In thissection we will describe the methods and proceduresinvolved in fireside and waterside cleaning.

CLEANING BOILERFIRESIDES

Excessive fireside deposits of soot, scale, and slagcause the following conditions: reduced boilerefficiency, corrosion failure of tubes and parts, reducedheat transfer rates and boiler capacity, blocking of gaspassages with high draft loss and excessive fan powerconsumption, and fire hazards.

Methods for cleaning boiler tiresides include wirebrush and scraper cleaning, hot-water washing.wet-steam lancing, and sweating.

Wire Brush and Scraper Cleaning

When too much soot is deposited and the passagesbecome plugged, hand lancing, scraping, and brushingare generally used. Special tools required for reaching

between the lanes of tubes may be made from flat bars,sheet metal strips cut with a saw-toothed edge, rods, andsimilar equipment. Some boilers have different sizes oftubes, so you need various sizes of brushes and scrapersto clean the boiler tubes. The brushes or scrapers arefastened to a long handle, usually a piece of pipe, insertedand pushed through the tubes.

Hot-Water Washing

This method of cleaning is often used to cleansuperheaters, economizers, and other sections of thesteam generator that are difficult or impossible to reachby brushing or scraping. The water may be appliedwith hand lances and/or boiler soot blowers. Dry outthe boiler setting immediately after water washing toreduce damage to the refractory and other parts of thesetting.

Safety is always paramount; therefore, always becautious when washing boiler firesides. Someprecautions you should observe are as follows:

Wet the boiler refractory and insulation as little aspossible. Install canvas shields or gutters wherepossible to reduce wetting of refractories.

Protect electrical equipment from water damage.

Provide all necessary instructions and protectiveequipment for workers.

Provide a compressed air lance to loosen scale afterwater washing.

Provide adequate equipment to heat and pump thehot water. The water should be heated andmaintained at a temperature close to about 150°F,because water exceeding this temperature cannotbe handled safely and efficiently. However,because cold water does not clean satisfactorily,you have to maintain the water temperature asclose as 150 degrees as possible. A water pressureof 200 to 250 psig should be provided at thecleaning lances or soot blowers. The water jetsmust penetrate the tube banks and strike withenough force to break up the slag accumulations.

Start the water washing at the top of the unit andwork down.

The unit must be dried out immediately afterwashing.

Wet-Steam Lancing

The wet-steam lancing method is similar to thehot-water method except that wet steam is used instead of

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hot water. The steam should be wet and at a pressure of70 to 150 psig. The unit must be dried out immediatelyafter lancing is completed.

Sweating

Fireside slag can be removed from the convectionsuperheaters by forming a sweat on the outside of thetubes. Cold water is circulated through the tubes. andmoisture from the air condenses on the tubes to producesweat. The hard slag is changed into mud by the sweat,and the mud can be blown off by an air or a steam lance. Alarge tank filled with water and ice can be used as thecold-water source. Steam can be blown into the areaaround the tubes during the cold-water circulating periodto provide adequate moisture in the air.

Cleaning Procedures

The procedures for cleaning boiler tiresides are asfollows:

1. Remove the boiler from service and allow it tocool. Make sure the boiler is cool enough for a person toenter. Someone must be standing by whenever a person isin the boiler. DO NOT force-cool the boiler.

2. Disconnect the fuel line openings. Secure allvalves, and chain. lock. and tag all fuel lines to the burnerand install pipe caps.

3. Disconnect the electrical wiring. Secure and tagthe electrical power to the boiler. Disconnect the burnerconduit and wiring. Mark and tag all electrical wiring toensure proper reinstallation.

4. Open the boiler access doors by loosening all nutsand dogs and swing the door open. Be careful not todamage the refractory door lining.

5. Remove the burner from the boiler openings.Follow the manufacturer’s instructions for specifiedburners. Wrap this equipment with plastic, rags. or othersuitable protective coverings. Remember. soot and loosecarbon particles must be kept out of the moving parts of theburner because they can cause the burner to malfunction.

6. Provide all spaces with free-air circulation byopening doors and windows, or provide fresh air bymechanical means. An assistant should be stationedoutside the opening and be ready at all times to lend a handor to be of service in case of a mishap.

7. Cover the floor area around the tube ends withdrop cloths to catch soot. Position a vacuum cleaner hoseat the end of the tube being cleaned. Keep soot from

contacting wet areas because soot and water form carbonicacid.

8. Remove tube baffles where possible and pass ahand lance or rotating power cleaner brush through eachtube slowly and carefully so no damage occurs topersonnel or equipment.

9. Inspect tube surfaces for satisfactory conditionbefore continuing on to the nest tube. Use a drop cord orflashlight for viewing through the entire length of a tube.Wire brush all tube baffles either by hand or use of powertools.

10. Apply a light coat of mineral oil to all cleanedsurfaces. To do this, fix an oil soaked rag to the end of abrush or rod long enough to extend through the tubes andthoroughly swab each surface, including baffles. Mineraloil is the only lubricant that prevents rusting and also burnsoff freely without leaving a carbon deposit.

11. Clean all flat surfaces by brushing with the hand orpower tools. Make sure that powered equipment isgrounded.

12. Use an industrial vacuum cleaner to remove loosesoot.

CLEANING BOILER WATERSIDES

Any waterside deposit interferes with heat transferand thus causes overheating of the boiler metal. Wherewaterside deposit exists, the metal tube cannot transferthe heat as rapidly as it receives it. What happens? Themetal becomes overheated so that it becomes plastic andblows out, under boiler pressure, into a bubble or blister.

The term waterside deposits include sludge. oil,scale. corrosion deposits. and high-temperature oxide.Except for oil. these deposits are not usually solubleenough to be removed by washing or boiling out theboiler.

The term waterside corrosion is used to include bothlocalized pitting and general corrosion. Most, if not all, isprobably electrochemical. There are always some slightvariations (both chemical and physical) in the surface ofboiler metal. These variations in the metal surface causeslight differences in the electric potential between onearea of a tube and another area. Some areas are ANODES(positive terminals).

Iron from the boiler tube tends to go into solutionmore rapidly in the anode areas than at other points on theboiler tube. This electrolytic action cannot be completelyprevented in any boiler. However, it can be reduced bymaintaining the boiler water at the proper alkalinity and

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by keeping the dissolved oxygen content of the boilerwater as low as possible.

The watersides of naval boilers may be cleaned intwo ways—mechanically, by thorough wire brushing ofall drums, headers, and tubes; and chemically. bycirculating chemical cleaning solutions through theboiler.

Mechanical Cleaning

Before mechanical cleaning of watersides is begun,the internal fittings must be removed from the steamdrum. The fittings (particularly the steam separators andapron plates) must be marked or otherwise identified as toposition in the steam drum to ensure their correctreinstallation. All internal fittings must be wire brushedand cleaned before they are reinstalled.

Cleaning the watersides of the generating tubesrequires a special tube cleaner. There are several typesavailable, but perhaps one of the most common is thepneumatic turbine-driven tube cleaner shown in figure1-31. This type of cleaner consists of a flexible hose, anair-driven motor, a flexible brush holder, and anexpanding wire bristle brush. The turbine-driven motorconsists of a set of turbine blades made to revolve whencompressed air is admitted through the hose. Theturbine-driven motor, in turn, drives the wire brush.There are several sizes of brushes available (figs. 1-32and 1-33). Figure 1-34 shows a brush refill for the type ofbrush shown in figure 1-32.

Before you start cleaning tubes, be sure that adequateventilation and lighting have been arranged. Someoneshould also be stationed outside the drum to act as tender

Figure 1-32.—Wire bristle brush for cleaning generatingtubes.

and to assist whomever is working in the drum. Keep awritten checkoff list of all tools and equipment taken intothe watersides and be sure that the same tools andequipment are removed.

With the air shut off, insert the tube cleaner in thetube until the brush is about even with the far end of thetube. Wrap friction tape, a rag, or some other marking

Figure 1-31.—Boiler tube cleaner (pneumatic turbine-driven type).

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Figure 1-33.—Wire bristle brush for cleaning large tubes.

Figure 1-34.—Brush refill.

material around the hose to show how far the tube cleanercan be inserted without having the brush protrude beyondthe far end of the tube. Then remove the cleaner from thetube. Remember that the tubes in each row are the samelength; however, the tube lengths vary from row to row.Therefore, separate markings have to be made on the hosefor each row of tubes.

After the hose has been marked, insert the brush inthe tube and turn on the air to start the brush rotating. Passthe brush SLOWLY along the length of the tube until theidentifying mark has been reached. Then slowly draw thebrush back. withdrawing the cleaner from the tube. Youdo not have to shut off the air to the tube cleaner each timethe cleaner is withdrawn from the tube. However, be sureto steady the brush assembly with your hand to keep thecleaner from whipping. Allowing the brush to whip ateither end of the tube is the most common cause of brokentubes.

Establish a new mark for the next row and proceedwith the cleaning. Make as many passes as necessarythrough each tube to ensure adequate cleaning. Becareful not to stop the tube cleaner in any one place in thetube, as the continued rotation of the brush in one placemight damage the tube. Be careful, also, to see that the

brush and the flexible shaft do not protrude from the otherend of the tube, as this may result in a broken shaft.

The tube is most easily cleaned from the steam drum.However, some rows of tubes are not accessible from thesteam drum and must be cleaned from the water drum orheader. The lower ends of ALL tubes must be cleanedfrom the water drum or header. You may also find tubesbent so that brushes cannot be forced around the bendwithout breaking the tube cleaner. These tubes must becleaned from both ends. Tube cleaners must be kept ingood operating condition. The rotor and blades of the airmotor should be kept clean and well lubricated. The hoseconnections should be kept tight and free from leaks. Theflexible shafts should be inspected frequently andrenewed when they show signs of wear or damage. Whenthe brushes become too worn to work efficiently, a newset of brush refills should be inserted into the brush body.Store tube cleaners in a clean, dry container.

After all tubes, drums, and headers have beencleaned and after all tools and equipment have beenremoved from the watersides, blow through the tubeswith air; then wash out the drums, tubes, and headers withfresh water. Ensure all dirt is removed from the handholdseats. Then examine the seats for scars, pits, or otherdefects that might cause leakage. All bottom blow,header blow, and test cock valves should be inspected andrepaired under the manufacturer’s instructions duringeach waterside cleaning.

After washing, thoroughly dry out the boilerwatersides. Inspect the watersides to determine thecondition of the metal to see if the cleaning wassatisfactory. Also, inspect the boiler to be sure that all theparts are tight. Be sure that all openings between drumsand gauge glasses, blow valves, and safety valves areclean and free of foreign matter. These openings aresometimes overlooked.

Chemical Cleaning

In most cases. mechanical cleaning is the preferredmethod for cleaning watersides. Chemical (acid)cleaning requires special authorization. since it requireselaborate and costly equipment and rather extensiveSAFETY precautions. However, you may have to use thechemical method, so a limited discussion on it is givenhere.

Inhibited acid cleaning is used to remove mill scalefrom the watersides of new or recently serviced boilers.When compared with mechanical cleaning, acid cleaningof boilers has the following advantages:

Less outage time is required.

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Because the cleaning is more complete, it is

possible to examine the unit thoroughly for

defects, such as cracks and corrosion pitting.

cleaners.

A more thorough job is accomplished becausethe acid reaches areas inaccessible to mechanical

Less dismantling of the unit.

Lower cost and labor.

ACIDS FOR CLEANING.—The following acidsare used to clean boilers: hydrocholoric acid, phosphoricacid, sulfamic acid, citric acid, and sulfuric acid.

HYDROCHLORIC ACID is most frequently usedfor boiler cleaning because it has a relatively low cost andsatisfactory inhibitors are available. Also, the chemicalreactions of the hydrochloric acid with the boiler depositsusually result in soluble chlorides.

PHOSPHORIC ACID can remove mill scale fromnew boilers. With this acid, the boiler can be fireddirectly without producing noxious or corrosive fumes.Direct firing produces good circulation and distributionof the cleaning solution. Another advantage ofphosphoric acid cleaning is that the metal surfaces resistcorrosion after cleaning. When cleaned withphosphoric acid, you must protect metal surfaces fromsurface corrosion during draining and beforeneutralization.

SULFAMIC ACID is available in powder that mustbe placed in solution. The powdered acid is easier andsafer to handle than liquid acids in carbons. It does notproduce noxious fumes as it dissolves and it is lesscorrosive than hydrochloric acid, especially at higherconcentrations and temperatures.

CITRIC ACID AND SULFURIC ACID are used forremoving boiler waterside deposits. Sulfuric acid iseconomical and easily inhibited. However, a danger isthat the sulfuric acid can form insoluble salts, such ascalcium sulfate.

INHIBITORS.—Without inhibitors, acid solutionsattack the boiler metal as readily as they attack thedeposits. With the addition of suitable inhibitors, thereaction with the boiler metal is greatly reduced.Inhibitors used include arsenic compounds, barium salts,starch, quinolin, and pyridin. Commercial inhibitors aresold under trade names by various chemical concerns.Other inhibitors are manufactured by companies thatfurnish complete acid cleaning services.

SAFETY PRECAUTIONS—When acid cleaninga boiler installation, you must observe SAFETYprecautions as follows:

Slowly pour the acid into water when mixing thesolutions.

Use goggles, rubber gloves, and rubber apronswhen handling acids.

After acid cleaning, be sure to thoroughly flush outall of the tubes that are horizontal or slightlysloping. Obstructions in these tubes can causepoor circulation, overheating, and failure of tubeswhen the unit is placed in service.

Do not exceed the specified acid and inhibitorallowable temperature. The inhibiting effectdecreases with the temperature rise and theprobability of acid attack of the boiler metalincreases.

Provide competent chemical supervision for thecleaning process.

Close all valves connecting the boiler with otherpiping or equipment.

Provide adequate venting for safe release of acidvapors.

Before acid cleaning, replace all brass or bronzeparts temporarily with steel or steel alloy parts.

CAUTION

NEVER POUR WATER INTO ACID.

Do not chemically clean boilers with riveted joints.

During acid cleaning, hydrogen gas can developthrough the reaction of the acid on the boiler metal.Some of the generated gas becomes part of theatmosphere inside the boiler, and the remainder isabsorbed by the boiler metal, then liberatedgradually. Because hydrogen air mixtures arepotentially explosive, be careful when opening aunit for inspection after acid cleaning. Until theatmosphere within the boiler pressure parts hasbeen definitely cleared of explosive gases, do NOTuse open flames. flashlights, lighting equipment.or anything that might produce a spark near theopenings to the pressure parts. Do NOT enter theboiler. The unit can be cleared of explosive gasesby thoroughly flushing the unit with warm waterwith a positive overflow from the highest ventopenings. The water temperature should be as near

1-39

to 212° F as possible to accelerate the liberation ofhydrogen absorbed in the metal. Afteropening the unit, place air blowers at the opendrum manholes to circulate air through the unit.Use a reliable combustible gas indicator to test theboiler atmosphere for explosive mixtures.

ACID CLEANING PROCEDURES—Boilerunits can be acid cleaned by either the "circulation" or"fill and soak" method. The circulation method (fig.1-35) can be used to clean units with positive liquid flowpaths, such as forced circulation boilers. The inhibitedacid solution is circulated through the unit at the correcttemperature until test analyses of samples from thereturn line indicate that the acid strength has reached abalance and no further reaction with the deposits istaking place. Because the strength of the acid solutioncan be determined frequently during the cleaningprocess, this method can be more accurately controlledand can use lower strength solutions than thefill-and-soak method.

The fill-and-soak method (fig. 1-36) is used forcleaning units with natural circulation. The boiler unit isfilled with the inhibited acid solution at the correcttemperature and allowed to soak for the estimated time. Itis not possible to obtain accurate representative samplesof the cleaning solution during the soaking period.

FLUSHING AND NEUTRALIZING—After acidcleaning, drain and then flush the unit with clean, warmwater until the flushing water effluent is free of acid andsoluble iron salts.

Next, a neutralizing solution is circulated through theunit until the effluent shows a definite alkaline reaction.The types of neutralizing solutions used are as follows:soda ash, trisodium phosphate. sodium tripolyphosphate,or other nontoxic chemicals. After circulation of theneutralizing solution, the water level can be dropped tothe normal level and the boiler fired at 50 psig with openvents to permit the escape of liberated gases. Finally. theboiler is again drained and flushed with clean, warmwater.

Boiling Out

New boilers. or boilers that have been fouled withgrease or scale, should be boiled out with a solution ofboiler compound. New boilers must be washed outthoroughly. The steps required for one method of boilingout are as follows:

1. Dissolve 5 pounds of caustic soda and 1 1/2pounds of sodium nitrate or 10 pounds of trisodiumphosphate for each 1,000 gallons of water the boiler holdsat steaming level. Put the mixture into the boiler as a

Figure 1-35.—Acid cleaning by circulation method.

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Figure 1-36.—Acid cleaning by fill-and-soak method.

solution. In multiple-drum boilers, divide the charge and

put equal amounts in each of the lower drums.

2. Fill the boiler with hot feedwater to the level of the

bottom of the steam drum. Turn the steam into the boiler

through the usual boiling out connections, or bottom blow,

and allow the boiler to fill gradually to the top of the gaugeglass.

3. Steam pressure in the boiler should be keptbetween 5 and 10 pounds. The boiling out should continuefor 48 hours. Immediately after boiling out, give a series of

bottom blows to remove the bulk of the sludge. The boiler

should be cooled, washed out immediately, and given theusual mechanical cleaning.

You may not always want to use the above methodfor boiling out. The steps for a second satisfactorymethod for boiling out are as follows:

1. Clean out all loose scale and any scale adhering to

the boiler that can be removed manually.

2. Place about 15 pounds of caustic soda or soda ash

and 10 pounds of metaphosphate for each 100-boilerhorsepower (hp) of the boiler.

3. Seal the boiler openings but OPEN ALL VENTS.Fill the boiler about three-quarters full with water.

4. Start the burner and raise the temperature of thewater in the boiler to about 200°F. Maintain this

temperature for about 24 to 48 hours. Add makeupwater as required during this period to fill the boiler to

the base of the safety valve.

5. Analyze the boiler water during the boiling outperiod and add enough caustic soda and metaphosphate tomaintain the following concentrations:

Causticity as ppm OH 300 to 500

Phosphate as ppm PO3 100 to 150

6. Open the boiler at the end of the boiling-out period

and clean out the sludge and loose scale. Pay particularattention to removing scale and sludge from water legs infire-tube boilers.

7. Flush the boiler thoroughly.

8. If a lot of corrosion is exposed when the scale isremoved, notify your superior so a boiler inspection can be

made.

When the boiler is operated, any residual scale maycause faulty operation. The boiler should be taken out ofservice at frequent intervals to remove sludge formedfrom disintegrated scale. As soon as personnel can workin the boilers, wire brush the drums and ends of all tubes.

1-41

Then clean the interior of all tubes, using the approved

style of boiler tube cleaning brushes.

You should operate all cleaners in the same way.

After cleaning all the tubes, follow up by blowing them

out thoroughly with a strong air jet. Then inspect to see if

replacement of any of the tubes is necessary.

Q27. What are the four methods used to clean boilerfiresides?

Q28. What pressure range should steam be for effectivewet-steam lancing?

Q29. What conditions are considered watersidecorrosion?

Q30. What acids are used for cleaning boilerwatersides?

Q31. What are the two methods of acid cleaning?

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CHAPTER 2

BOILER MAINTENANCE

Learning Objective: Recognize maintenance requirements and procedures forboilers and auxiliary equipment; recognize boiler operation steps and checks andsafety requirements.

As a Utilitiesman, it is your responsibility to operate,maintain, and repair boilers. You can perform operatormaintenance on shore-based boilers; perform preventivemaintenance and minor repairs on boilers and associatedequipment; complete chemical tests on boiler water andfeedwater; replace defective boiler tubes; test, adjust, andrecalibrate boiler gauges and other accessories.

This chapter provides information on some of themethods, procedures, and techniques used to operate,maintain, and repair boilers and associated equipmentsafely under typical conditions. Because of the broadscope of tasks involved in operating and servicingboilers, this chapter does not tell you all you need toknow about the subject. Learning how to accomplishthe procedures given in the following sections can helpyou acquire a basis on which to develop moreadvanced skills. While the procedures given in thischapter are typical, you should always follow themanufacturer’s instructions for the equipment.

MAINTENANCE OF AUXILIARYEQUIPMENT

Learning Objective: Recognize andauxiliary equipment maintenance.

understand basic

A well-planned maintenance program is the key toavoid unnecessary downtime or costly repairs,promotes safety, and aids local inspection. Aninspection schedule listing the procedures should beestablished. It is recommended that a boiler room logor record be maintained for recording the daily,weekly, monthly, and yearly maintenance activities.This provides a valuable guide and aids in theoperational efficiency, length of service, and safeoperation of a boiler. It is also important to rememberthat improperly performed maintenance is just asdamaging to a boiler as no maintenance at all.

MAINTENANCE REQUIREMENTS FORCONTROL OF WATER LEVEL

The need to check water level controls and thewater side of the pressure vessel periodically cannot beoveremphasized. Most instances of major boilerdamage are the result of operating with low water orusing untreated (or incorrectly) treated water. Alwaysbe sure of the boiler water level and blow down thewater column routinely. Check samples of boiler waterand condensate according to procedures recom-mended by your water consultant (figs. 2-1 and 2-2).

Since the manufacturer generally sets low watercutoff devices, no attempt should be made to alter oradjust these controls. If a low water device shouldbecome erratic in operation or if the setting changesfrom previously established levels, check for reasonsand correct it by repair or replacement.

Figure 2-3 is a replica of the low water cutoff plateattached to a steam boiler. These instructions should befollowed on a definite schedule. These controlsnormally function for long periods of time and maylead to laxity in testing on the assumption that normaloperation will continue indefinitely.

On a steam boiler, the head mechanism of the lowwater cutoff devices should be removed from the bowlat least once a month to check and clean the float ball,the internal moving parts, and the bowl or watercolumn. Remove the pipe plugs from the tees orcrosses and make certain the cross-connecting piping

is clean and free of obstructions. Controls must bemounted in a plumb position for proper performance.

A scheduled blowdown of the water controls on asteam boiler should be maintained. It is impractical toblow down the low water cutoff devices on a hot-waterboiler since the entire water content of the systemwould be involved. Many hot-water systems are fullyclosed and any loss of water would require makeup and

2-1

Figure 2-1.—Typical water column and low water cutoff high-pressure steam boiler.

Figure 2-2.—Typical water column for low-pressure boiler.

2-2

Figure 2-3.—Low water plate.

additional feedwater treatment that might nototherwise be necessary. Since the boiler and systemarrangements usually make it impractical to performdaily and monthly maintenance of the low water cutoffdevices, it is essential to remove the operatingmechanism from the bowl annually, or morefrequently if possible, to check and clean the float ball,the internal moving parts, and the bowl housing. Also,check the cross-connecting piping to make certain thatit is clean and free of obstructions.

GAUGE GLASS REPLACEMENT

A broken or discolored gauge glass should bereplaced at once. Always use new gaskets whenreplacing a gauge glass. Use the proper size rubberpacking. Do not use "loose packing" that could beforced below the glass and possibly plug the valveopening.

Close the valves when replacing the glass. Slip apacking nut, a packing washer, and a packing ring ontoeach end of the glass. Insert one end of the glass into theupper gauge valve body far enough to allow the lowerend to be dropped into the lower body. Slide thepacking nuts onto each valve and tighten.

If the glass is replaced while the boiler is in service,open the blowdown valve and slowly bring the glass tooperating temperature by cracking the gauge valvesslightly. After the glass is warmed up, close theblowdown valve and open the gauge valvescompletely. Check the try cocks and gauge cocks forfreedom of operation and clean them as required. It isimperative for the gauge cocks to be mounted in exactalignment. If they are not, the glass will be strained andmay fail prematurely.

FEEDWATER REGULATORMAINTENANCE

Proper control of the water level requires that thefeedwater regulator be maintained. Here are a fewpointers for regulators.

If the water level changes from its normal position,make sure you adjust the bypass to manual operationand check promptly for the source failure. If leaksdevelop around the packed stems, see that they arestopped immediately. If the boiler is off line, close thehand valve in the feed line. Bear in mind that theregulator is not designed for use as a stop valve. Aboutonce every 3 months, you will probably be called on toassist in blowing down the steam and waterconnections separately.

VALVE MAINTENANCE

Valves deserve special care and attention if theyare to work as intended. There may be variationsamong activities in the type and frequency of valveinspection and servicing requirements. Therefore,follow instructions issued by your activity when theydiffer from those outlined here.

Types of valves that you may be responsible forhelping service and maintain at regular intervalsinclude (1) stop valves of the globe or gate type and (2)stop-and-check valves, which combine in one tray andangle or stop valve of the globe type and a check valve.At least once every 3 months, valves that have not beenoperated for some time should be operated to preventsticking. Make sure that you also check for leaks, bentstems, a missing or broken handle, and lubricate theexposed threads and gearing of the valve stem.

Loosen and lift the packing follower about onceevery 3 months or more often if possible. Lubricate thepacking with graphite bearing oil or graphite bearinggrease. Replace the packing followers and tightensufficiently to ensure against leaks.

BLOWOFF or BLOWDOWN VALVES shouldbe opened at least once a day. There are four reasonsfor using these valves:

1. Controlling high water

2. Removing sludge and sediment

3. Controlling chemical concentrations in thewater

4. Dumping a boiler for cleaning or inspection

The amount and frequency of blowing downdepends on a chemical analysis of the water in theboiler and operating conditions.

On a quarterly basis, inspect the blowoff valveswhen the boiler is washed out and an internalinspection is made. Check the valves for leaks, andinspect the pipe and fittings between the blowoff

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valves and the boilers. If repairs are needed, see thatthey are made promptly. In making a quarterly checkon the blowoff valves, do not overlook the insulation,bearing in mind that it should be kept dry. Another itemis the discharge piping leaking from the valves. Makesure the discharge piping is not mounted so rigidly thatproper expansion and contraction are affected.

Keep SAFETY VALVES (fig. 2-4) in top workingorder. At regular intervals, depending upon operatingconditions, the safety valves must be lifted manually.At least once each year the valves should be tested byraising steam pressure to popping pressure of therespective valve. If safety valves function improperly,promptly report the matter to your immediatesupervisor . For detai led information on themaintenance of safety valves, refer to manufacturer’smanual.

STEAM INJECTOR MAINTENANCE

With injectors, little maintenance is required. Attimes you will have to reseat the overflow and ringvalve. Lime deposits also can reduce the operation byclosing down the size of the combining and deliverytubes. A good way to remove lime deposits is to placethe injector in a tube of muriatic acid for several hours.

To clean the injector, remove the bottom plug (fig.2-5). The delivery tube and ring valve drop out.Examine and clean all passages and holes. Aftercleaning, replace them in the plug (which acts as aguide) and screw tightly in place.

STEAM TRAP MAINTENANCE

Once each month, see that steam traps are testedfor correct operation. Methods used in testing steamtraps (such as the test valve method, the glove testmethod, etc.) are discussed in another section of thistraining manual.

Once a year, or more often if required, dismantleand clean all traps. Inspect for the following:

1. The accumulation of foreign matter

2. Plugging of orifices, valves, and vents

3. Cracked, corroded, broken, loose, worn, ordefective parts

4. The excessive wear, grooving, and wiredrawing of valves and seats

5. Defective bellows, buckets, or floats

6. Leaky vessels and pipes

7. Defective bypass valves

Repair or replace defective parts as requiredfollowing yearly inspection. Replace or repair all

Figure 2-4.—A typical spring-loaded safety valve. Figure 2-5.—A cross-sectional view of an injector.

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defective gaskets, bellows, valves, valve seats, floats,buckets, linkages, and orifices. Use only matched setsof replacement valves and seats. Make certain allreplacement parts are of the correct size. Do not changethe weight of floats or buckets when repairing traps, oroperation may be affected. Often, it is moreeconomical to purchase and install new parts than torecondition defective elements. Repair or replaceleaking bypass valves. Repack valve stems.

header and one on the plate). Be sure you remove allthe corrosion or other surface deposits and all adheringpieces of the old gasket. It is impossible to obtain atight joint as long as any foreign matter remains oneither seating surface or in the corners of the fitting. Besure to water-soak the new gasket for 24 hours before

FAN MAINTENANCE

The forced-draft fan should be checked daily toprevent an accumulation of dust in or around the fan.KEEP THE FAN CLEAN! Also, check daily on thesound of the fan. If it is not normal, report the matterpromptly to your supervisor.

A daily check should also be made to ensureadequate lubrication of the fan. The temperature isanother item that should not be overlooked. This youcan test by feel. In case of excessive temperature,notify your supervisor immediately.

Because induced-draft fans are exposed to hot,dirty gases, they must be observed closely to preventoperating difficulty. Taking proper care of the fanrequires DAILY attention to ensure that the followingconditions are met:

1. Bearings are kept cool and well lubricated.

2. Fan is kept clean. Also, see that any change fromthe normal in sound is reported promptly to yoursupervisor.

HANDHOLE AND MANHOLE GASKETMAINTENANCE

At each regular boiler overhaul, all handhole andmanhole fittings and gasket seating surfaces on thedrums and headers must be cleaned, inspected,repaired, or renewed if necessary. If the plates arewarped, distorted, or otherwise damaged, they must berepaired or renewed.

Whenever handholes and manholes are opened,new gaskets must be fitted. After a gasket has oncebeen compressed, it must be discarded, as it will notprovide a seal. Be sure to use the correct size and typeof gasket. Never use any makeup compound on theseating surfaces when installing the gaskets. Graphitemay be used on the threads of the stud to preventseizure of the nut.

installation.

Power-driven wire brushes are best for cleaningthe seating surfaces. Scrapers should be used onlywhen wire brushes are not enough to clean the surface.Scrapers must be used with great care, if they are usedat all, since they tend to remove too much metal fromthe seating surfaces.

If the gasket seating surfaces show a lot of pitting,you may have to get these surfaces machined orreground. If the seating surface on a handhole ormanhole plate is badly pitted or damaged, discard theplate and replace it with a new one or one that has beenmachined to blueprint specifications.

The clearance between the shoulder of a manholeplate and the manhole must not exceed one-sixteenth ofan inch when the plate is centered accurately. Figure 2-6shows where the clearance is measured. If the clearanceis greater than one-sixteenth of an inch, the plate shouldbe built up by electric welding at the inner edge of theshoulder. Steelworkers should do the welding, so themanhole plate may be stress-relieved after it is weldedand the welded surface may be remachined.

To position a manhole gasket properly, fit it on thelong axis until the inner edge of the gasket fits theshoulder snugly at the ends of the long axis of themanhole plate. The clearance between the gasket andthe shoulder should be equalized at the top and bottomof the short axis. Do NOT allow the outer edge of thegasket to protrude at any point beyond thegasket-seating surface in the drumhead. If an edgeprotrudes, the gasket may unravel when it iscompressed by the tightening of the manhole cover.Discard any gasket that protrudes beyond the edge ofthe gasket-seating surface.

theBefore installing a new gasket, thoroughly cleantwo gasket seating surfaces (one on the drum or

Figure 2-6.—Manhole plate clearance.

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To install a manhole or handhole plate, first centerthe fitting in the opening. Make sure the shoulder doesnot bind on the edges of the opening. Then slip the yokeon and start the stud nut. Run the nut on the stud until itis hand tight; then give the nut one-quarter of a turnwith a wrench. Do NOT tighten the nut enough tocompress the gasket.

When the boiler is given a hydrostatic test, thepressure of the water usually forces the manhole andhandhole gaskets into place and thus ensures properseating. The plates are first set up lightly. When theboiler is ready for testing, the pressure should bepumped up to within 50 psi of the hydrostatic testpressure, regardless of any leakage from the manholeor handhole plates. Leakage is likely to be general atfirst, but it decreases as the pressure is increased. Whenthe pressure is within 50 psi of the test pressure, mostof the leakage stops although the nuts are still loose.

If some plates are leaking badly, the trouble isprobably caused by improper seating of the gaskets. Asa rule, the gasket is caught on the outer edge betweenthe edge of the plate and the edge of the counterbore forthe seat. A light blow with a hammer on the outside ofthe plate usually relieves the tension on the gasket and

allows it to seat properly.

After leaky gaskets have been adjusted and whilefull test pressure is on the boiler, tighten up all platesfirmly. Use only the wrenches specified for thispurpose.

Some economizer headers and a few superheaterheaders are fitted with handhole plugs instead ofhandhole plates. Also, some economizers havebayonet types of cleanout plugs on the front ends of thetube loops to allow access to the tubes at the returnbend end. Detailed instructions for installing andremoving the plug type of manhole fittings and thereturn bend cleanout fittings are given in appropriatemanufacturer’s technical manuals.

HYDROSTATIC TESTS

The boiler should be given a hydrostatic testannually or whenever the operator doubts the boilerstrength. The purpose of the test is to prove theTIGHTNESS of all the parts of the boiler or theSTRENGTH of the boiler and its parts.

In preparing the boiler for a test, rinse it out withfresh water. Then check carefully to see that no loosescale or tools are left in any part of the boiler.

The procedures for making boiler hydrostatic tests

are as follows:

1.

2.

3.

4.

5.

6.

7.

8.

Close all openings and "gag" (clamp down) allsafety valves. Gags should be only hand tightand straight. Do NOT use a wrench; it will bendthe valve stem and possibly damage the seat.Remember that valves are easily damaged iflifted by water pressure. Close all connectionson the boiler except air cocks, test pressuregauge, and valves of the line through whichpressure is to be applied.

Reduce the water level in the boiler by openingan air cock, and blow down the boiler until thewater level is below the feedwater inletconnection. Clear the blowdown area beforeblowdown.

Connect a hydrostatic pump between the boilerand water service connection. Install all pipeand fittings between the pump and the boiler.Remember, the pipe and fittings must be able towithstand test pressures. Install a hose betweenthe pump and the chosen water service. Ensurethe chosen water service supplies ample waterpressure to conduct the test.

Remove the plug from the feedwater inlet crossby turning it in a counterclockwise direction.

Open the boiler casing access doors or plates, sotube ends can be inspected during the test.

Install a wedge between the control switch andthe pressure-actuating platform. Also, install astop valve before the control switch to protectthe control, so hydrostatic pressure will notactuate or damage the control. The range of thepressure control is usually less than thehydrostatic pressure being applied. Do NOTbend or damage the actuating parts.

Fill the boiler with water until water dischargesout of the air cock; then close the air cock.Ensure all the air is expelled from the boilerbefore closing the air cock. Turn on the waterservice valve. The water temperature should bethe same as the surrounding atmosphere. Theminimum water temperature must be 70°F.

Check the boiler steam pressure gauge in-linecock to ensure that it is open. Ensure thebutterfly handle is in-line (parallel) with thetubing.

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9.

10.

11.

Apply water pressure of 1 1/2 times themaximum allowable working pressure. Toavoid rapid shock and strain, bring this pressureup in 10 equal increments, inspecting for leaksand deformities at each increase.

Inspect tube ends, boiler seams, pressurefittings, and connections. Make the correctionsand repairs wherever possible. In case ofunusual conditions, DISCONTINUE the testIMMEDIATELY and NOTIFY YOURSENIOR PETTY OFFICER. Do NOT exceedthe test pressure. NEVER apply more than 10pounds of pressure above the maximumworking pressure on a low-pressure boiler.Consult the ASME code for testing proceduresfor other than welded steel boilers.

Secure pressurizing connections at the requiredtest pressure. Continually inspect the boilertubes, seams, fittings, and connections. If theboiler and fittings are tight, the pressure shouldNOT drop more than 1.5 percent in 4 hours. Ifloss of pressure is over 1.5 percent, find theleak(s) and make the repairs.

Following all hydrostatic testing, steam pressure israised to lift safety valves and to determine the fitnessof the boiler for use.

Q1.

Q2.

Q3.

Q4.

Most cases of major boiler damage is caused bywhat operating condition?

What could happen if "loose packing" is used ona gauge glass?

What are the four reasons for using blowoff orblowdown valves?

What is the purpose of a hydrostatic test on aboiler?

BOILER TUBES

Learning Objective: Recognize and understandmethods for renewing, repairing, and cleaning boilertubes and sheets.

For any boiler retubing job, it is absolutelyessential to use tubes that conform in every way to thetube requirements of the particular boiler. Boiler tubesare NOT identical. They differ in such importantcharacteristics as composition of the metal, outsidediameter, wall thickness, length, and curvature.

Much of the required information on sizes,thickness, and number of tubes per boiler is given inthe manufacturer’s technical manual. Some of theinformation is under the heading of "Tube Data." Moredetailed information is usually given on the drawingsincluded in the manual.

COMPOSITION OF BOILER TUBES

Generating tubes are usually made of low carbons t e e l . T h e y m a y b e e i t h e r s e a m l e s s o rresistance-welded. Seamless tubes were oncedefinitely preferred for naval use. However, improvedmethods of manufacturing the welded tubes have led to- -an increased use of welded tubes in naval boilers.Repair ships, tenders, and other naval activities thatuse, handle, or issue plain carbon steel tubes have beeninstructed to make no distinction between the seamlessand the welded tubes, but to stock, issue, and installthem interchangeably without regard to the method ofmanufacture.

Superheater tubes usually are not made of plainlow carbon steel. On boilers where the superheatedsteam temperature reaches 850°F or higher, thesuperheater tubes may be made of carbon-molybdenum steel, chromium-molybdenum steel, oran 18-8 chromium-nickel (stainless) steel.

To find detailed information on the composition ofthe metals used for generating tubes and superheatertubes in any particular boiler, check the manufacturer’stechnical manual. The information may be given on thedrawings, or it may be included in the text.

Once you have found information on thecomposition of the metals used for boiler tubes, yournext problem is to understand it. Do you know what itmeans when you see "mild steel" on a blueprint? Canyou identify metals by their chemical symbols? Do youknow what an "alloy steel" is, or anything about thedifferent kinds of alloy steels? Do you know anythingabout the various systems of classifying steels? Do youknow why different steels are used for different kindsof tubes? Answers to these questions are necessarybefore you can make much sense out of the informationyou are likely to find on blueprints on the compositionof boiler tubes.

Although we all have a general idea of what wemean by the word metal it is not easy to give a simple,accurate definition. Chemical elements are metals ifthey are lustrous, hard, good conductors of heat andelectrcity, malleable, ductile, and heavy. In general,these propert ies of hardness, conductivi ty,

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malleability, and so forth, are known as metallicproperties, and chemical elements that possess theseproperties are generally called metals. Chemicalelements that do not possess these properties are callednonmetals. Oxygen, hydrogen, chloring, and iodineare a few examples of nonmetallic chemical elements.A few chemical elements behave sometimes likemetals and sometimes like nonmetals. These elementsare often called metalloids. Carbon, phosphorus,sulfur, and silicon are examples of metalloids.

Most types of steel look quite a lot alike, so youcannot go by appearances. On Navy blueprints and ondrawings furnished in the manufacturer’s technicalmanuals, materials are usually specified by federal ormilitary specification numbers. In addition, theblueprints and drawings may refer to a commercialclassification system, such as the Society ofAutomotive Engineers (SAE) system or the AmericanIron and Steel Institute (AISI) system.

Federal or military specifications usually requirethe tubes to be identified by some marking system. Forexample, one specification for boiler tubes requiresthat boiler tubes 1 1/4 inches or greater and 3 feet inlength be legibly marked by paint stenciling, whilesmaller or shorter tubes may be bundled and tagged.Another boiler tube specification requires the tubes tobe marked by ink stenciling approximately 3 inchesfrom each end and again in the middle of the tube. As ageneral rule, boiler tube identification markings mustinclude (1) the name or trademark of the manufacturer,(2) the heat number, (3) the class letter, (4) thespecification number, and (5) the outside diameter, thewall thickness, and the length.

RENEWING TUBES

Boiler tubes should be replaced when they cannotbe made tight, or when they are warped, or otherwiseseriously damaged. As a general rule, boiler tubesshould not be straightened in place; leaks may developthat could cause permanent damage to other parts ofthe boiler. Occasionally, however, you may find ascreen tube or a wall tube that has bowed out ofposition for no apparent reason; you can straighten thetube in place and re-roll it if a replacement tube is notavailable. Tubes that have bowed out of positionb e c a u s e o f l o w w a t e r S H O U L D N O T B ESTRAIGHTENED.

To renew tubes in the A row, the correspondingtubes in the B row must also be renewed, regardless oftheir condition. Similarly, whenever superheated tubes

are renewed, remove the superheater support tubeswhen they are not accessible without removal of thesuperheater tubes.

General renewal of tubes in a boiler should not beundertaken without approval of the battalion or basecommander. The commander’s decision as to whetherto approve a general renewal of the tubes will be basedon the results of inspection and examination of tubesamples.

Before beginning to renew tubes, be sure allpreparations have been made. Be sure the right types ofreplacement tubes are available and that all tools andequipment required for the job are on hand and in goodworking order. Check the cutters, the air hoses, and thefittings for the pneumatic tools, the tube benders, theelectric equipment, and the staging.

The steam drum must be opened and some fittingsremoved to allow access to the ends of the tubes. Also,the water drums and headers must be opened. Anyfittings removed from the drums should be carefullyset aside and marked, if necessary, to ensure correctreplacement.

Before allowing a person to enter the boiler, besure all safety precautions are observed. Make it yourpersonal responsibility to see that all cross-connectingvalves between the boiler being retubed and anysteaming boiler are closed and locked or wired shut andare tagged DANGER. DO NOT OPEN. Be sure, also,that the control valves of the steam-smothering systemare locked in the CLOSED position. See that enoughventilation is provided; keep portable blowers runningat all times while people are working in the boiler. Donot allow unauthorized types of lights in the boiler.Flashlights are preferred for boiler work. If portablelights are used, the electric leads must be thoroughlyinsulated and the portable fixture itself must be thegrounded, watertight type. Before use, portable lightsshould be checked by an electrician to ensure they aresafe.

REMOVING TUBES

Using an air-powered side-cutting chisel (fig. 2-7)ground, cut the old tube flush with the drum or header.Carefully work the cutter so as not to damage thesurface of the drum or header. When you are removingsuperheater tubes, it will be impossible to cut the tubeflush with the header with a side-cutting chisel. Anexpandable fly cutter must then be used to cut out thetubes.

2-8

Figure 2-7.—Side-cutting chisel.

After removing the main part of the tube from theboiler, use a safety ripping chisel of the type shown infigure 2-8 to make a cut on the inside of the remainingportion of the tube. The safety ripping chisel isdesigned so it cannot cut entirely through the tube;therefore, it cannot score the tube sheet.

After cutting the tube approximately three fourthsof the way along the tube sheet, crimp the edges of thetube and drive out the stub with a blunt chisel. If thetube is a large one, you may have to make two cuts withthe safety ripping chisel instead of one; the cuts shouldbe about an inch apart.

If a safety ripping chisel is not available, you canremove the tube by the following method:

1. Split the ends of the tube with a flat chisel, fromthe end of the tube to the drum or header, at twoplaces about three fourths of an inch apart.

2. Force the 3/4-inch piece upward with a bar untilit has been raised off its seat and has curled intothe tube.

3. Split the tube to a point beyond the other side ofthe tube seat with a tool ground to conform to the tubehole. Be careful not to damage the tube hole.

4. Break in the ends of the tube with a crimpingtool, and then drive out the stub.

Arc welding equipment can be used as an aid to thetube removal on some boilers. This procedure requiresrunning two beads, three fourths of an inch apart,through the entire tube sheet, quenching with water,and then using a backing-out tool. Do NOT use thismethod of tube removal if the drums or headers aremade of 4-6 chromium steel.

CLEANING TUBES

Replacement tubes must be thoroughly cleaned toremove all scale, dirt, and preservatives. One way ofcleaning a tube is to push a kerosene-soaked ragthrough it and wipe the outside of the tube with asimilar rag. Diesel oil may also be used. If a largeenough tank is available, boiler tubes may be cleanedby immersing them in an approved cleaning solution,such as a saturated solution of boiler compound in hotwater, to which a small amount of kerosene has beenadded. Boiler tubes may also be cleaned with steamjets.

Figure 2-8.—Safety ripping chisel.

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PREPARING TUBE SHEETS

The tube sheet holes must be prepared beforereplacement tubes are inserted. The best way is to use apiece of hardwood turned to a diameter slightly less thanthe diameter of the hole and covered with a mediumfine-grit emery cloth. Pass the wooden piece in acircular motion, back and forth through the tube sheet orheader holes to smooth the surface. Finish the job byusing a fine emery cloth wrapped around your finger.Keep working until the hole is clean and smooth.

When preparing tube seats, check the size andtrueness of the tube holes; use a tube nipple ofcorresponding size as a template. It is impossible tomake tube seats tight if the tube holes are muchenlarged or if they are too elliptical (out-of-round). Toensure the tightness of the tube seats, be sure that themaximum enlargement and the maximum ellipticity ofthe tube holes do not exceed the figure shown in tableA, appendix II.

REPAIRING TUBE SHEETS

Out-of-round tube holes, small steam cuts, and otherminor defects may, in some cases, be corrected bywelding. NAVFAC approval is not required for this typeof welding repair on drums and headers made of lowcarbon steel, carbon-molybdenum steel, or steelcontaining less than 1 percent chromium if a qualifiedwelder uses approved welding procedures for thewelding, filler metal, and position of welding underMIL-STD-248. Always check the blueprints for thematerial of the drums and headers before welding.

PREPARING TUBE ENDS

After the tubes have been thoroughly cleaned,prepare the tube ends inside and outside. Clean theends with a wire brush and polish them with abrasivepaper and a liquid cleaner until the tube ends arecompletely clean, free of burrs and mill scale, andthoroughly polished. Clean and polish the tube ends fora distance equal to the thickness of the tube seat plus 2or 3 inches.

Round off the tube ends with a file, so no square orsharp edges remain. If the tubes are not rounded off atthe ends, the tubes may split when they are belled.

FITTING TUBES

When installing tubes, always fit the tubes into thesteam drum before inserting the other end in the waterdrum or header. Inserting the tubes into drums and

headers is not particularly difficult, since all tube holesare drilled normal to the tube sheet.

If you are renewing a complete row of tubes, fit atube at each end of the row and then work toward&middle. You may find slight differences in the lengthsof tubes required, if the boiler has been in service forsome years. These differences are more likely to showup at the ends of the rows than in the middle.

When fitting tubes into drums or headers, be sureeach tube extends far enough into the header or drum.Tubes up to (but not including) 2 inches in outsidediameter (OD) should project 3/16 to 5/16 inch into thedrum or header. Tubes 2 inches OD and larger shouldproject 5/16 to 7/16 inch into the drum or header.

After you have fitted a tube and allowed for theamount it must project into the steam drum and into thewater drum or header, remove the tube and cut off theexcess. You may be able to use one tube as a guide forcutting off the excess on several other tubes; if yourecall, the tubes may vary slightly in length,particularly in older boilers. Do NOT use one tube tomeasure the rest of the tubes in a row if you believethere are big differences in tube lengths in the row. Ifyour sample tube happened to be a little on the shortside, you would end up with a whole row of tubes thatwere too short; therefore, they could not be used.

Each tube must be carefully aligned with the othertubes. Use a plywood batten about 1/2 inch thick, 3 feetlong, and 3 inches wide to align tubes in the generatingbank. After positioning the tubes, check them with thebatten. Then place small, wooden wedges to hold thetubes in place until they have been expanded into thetube sheets. Be sure to remove the batten and thewedges before starting work on the next row. Thesewooden pieces cannot be left in the boiler. You willhave a real job on your hands if, after installing five orsix more rows of tubes, you suddenly discover that youhave overlooked the batten or one of the wedges.

EXPANDING TUBES

The basic joint in boiler construction is anexpanded joint that must not leak nor lack holdingpower. Leakage, if permitted to go uncorrected, leadsto deficiency of holding power because ofdeterioration of the tube seat. Slight leakage itselfshould not be taken as cause for alarm, but rather asevidence to correct the fault as soon as possible.Deficiency of holding power causes the tube to pull outof its seat. In most cases, the tubes are installed withinthe furnace of the boiler, and any danger to personnel,if the tubes pull out of the seat, is reduced since the

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steam will be discharged up the stack. For this reason,tubes l-inch-outside diameter (OD) up to andincluding 2 inches OD are expanded by "boilerman'sfeet" as only a small amount of expansion is required tohold the tubes firmly in place. With tubes 3 inches ODand larger and all external downcomers, specialprecautions must be taken to ensure the tubes areproperly expanded in the tube seat. Through a series oftests, the point of maximum holding power for varioussizes of tubes has been found and is expressed in termsof standard diameters that should be measured after thetube has been expanded in place. In new constructionor replacement of tubes where the tube and holemeasurements can be obtained, the correct amount ofexpansion can be found by using the followingformulas:

For tubes in drums: Diameter of tube hole minusOD of tube, plus 0.012 inch per inch OD of tube.

For tubes in headers for boiler design pressureunder 500 psi: Diameter of tube hole minus OD of tube,plus 0.015 inch per inch OD of tube.

For tubes in headers for boiler design pressure over500 psi: Diameter of tube hole minus OD of tube, plus0.020 inch per inch OD of tube.

The figure arrived at by using the above formulasshould be added to the OD of the tube as measured togive the required OD of the tube after rolling.

If it is impossible to reach the outside of the tubesin drums to gauge them, the inside diameter (ID) of thetube must be mea sured. Since the plastic deformationof the tube wall varies with tube wall thickness, the IDof the tube for different wall thickness will vary.Where the outside of the tube is inaccessible, thefollowing formula is used in the expansion of a tube:

The ID of the tube, plus the tube hole diameterminus the OD of the tube plus the expansion increasefactor.

Boiler tubes should be expanded with theexpanding equipment furnished to the shop. Selectexpanders of the proper size for the tube size and theseat thickness and expanders proper for the operationto be perform ed.

There are two types of expanders: roller-type andball-drift type. Roller-type expanders are furnished foruse by the shop labor force. Roller-type expanders areshown in figure 2-9. A series of adapters are furnishedfor use if tube holes are not readily accessible. Some ofthese adapters are shown in figure 2-10.

Figure 2-9.—Roller-type tube expanders.

Figure 2-10.—Adapters for tube expanders.

Tube expanders are operated by air motors. Theair, at about 100 psi, enters through a controllinghandle and goes into the motor housing where it drivesan air turbine. The turbine is attached to the shaft of themotor. The controlling handle can be turned clockwiseor counterclockwise. A chuck with a tapered shankengages the shaft of the air motor, thus transmitting thepower of the motor to the rollers used for expandingtubes into the tube sheet.

Both the air motors and the chucks are available invarious sizes. The large sizes of motors and chucks areused for expanding the larger sizes of tubes. Figure2-11 shows a tube expander in use.

Figure 2-11.—Expanding a tube.

2-11

Tube expanders must be used carefully to avoiddamage to the expanders and to prevent injury topersonnel. The centrifugal force developed by the airturbine is great, so the air motor must be gripped firmlywith both hands. If the roller-mandrel combinationshould bind, the force of the air motor could break themandrel and quite possibly cause injury to theoperator. Always have a person stationed nearby togive immediate assistance if necessary. If you run intoany trouble, your safety person may be able to crimpthe hose quickly and thus keep the mandrel frombreaking.

BELLING TUBES

Most tubes are expanded and belled. However, Figure 2-12.—Belling tool.

check the drawing to determine if any specificinstructions are shown. Some tubes in 1,200 psi boilersare lightly expanded or belled before welding; someare directly butt-welded to the studs. A roller-type or adrift-type belling tool is used. The drift-type tool isshown in figure 2-12.

When belling a tube, be careful not to overdo theoperation. Tubes up to, but not including 2 inches ODshould be belled at least 1-15 inch but no more than 1/8inch. Tubes 2 inches OD and larger should be belled atleast 1/8 inch, but no more than 3/16 inch. The increaseis to be measured over the outside tube diameter at theend of the tube. Figure 2-13 shows the process ofbelling a tube.

Some expanders are fitted with belling rolls, asshown in figure 2-9. When these expanders are used,the tubes are expanded and belled at the same time;thus, there is no need for a separate belling job.

RENEWING WELDED TUBES

In some boilers of recent design, the superheatertubes and the economizer tubes are welded after theyhave been expanded. The renewal of these tubes ismore complicated than the renewal of ordinary tubes.Procedures for renewing welding tubes are given in theappropriate manufacturer’s technical manual.

PLUGGING BOILER TUBES

CAUTION

Any tube that is plugged must have a hole

be replaced.

drilled in it to prevent pressure buildup inthe tube when the boiler is steamed.

As an emergency measure, it is sometimesnecessary to plug defective boiler tubes until they can

Figure 2-13.—Belling a tube.

Various sizes of tube plugs are carried in thesupply system. The plugs are tapered to the requiredshape and are usually drilled and threaded at the largerend, so they may be removed with a tube plugextractor.

Tubes must be plugged at each end. Before drivinga tube plug into position, be sure the plug and the insideof the tube are absolutely clean, so the plug makesgood metal-to-metal contact with the tube. Drive theplug far enough in to ensure it will hold, but do notdrive it so far in that it damages the tube sheet.

In plugging superheater tubes, use an offset driverto drive in the plugs when the tube holes do not fall inline with the handhole opening. When a superheatertube is plugged, it will eventually burn away after aperiod of service. When tubes have burned away (orwhen they have been removed) so much that they leavea gas lane more than three tube rows wide through theentire superheater tube bank, plug the gas lane with a

2-12

plastic or castable refractory. If the lane cannot beplugged, the firing rate of the boiler must be restrictedto avoid overheating the superheater tubes next to thegas lane.

When a sidewall tube needs to be plugged, cut thetube 3 to 4 inches above the sidewall heater and 3 to 4inches below the steam drum. The space left exposedafter removal of the tube should be packed with plasticrefractory to protect the pressure parts previouslycooled by the plugged tube. Do not plug more than twotubes next to each other, since an exposed area widerthan this cannot be effectively protected for anextended operation. Sidewall tubes that have beenplugged should be replaced at the earliest opportunity.

When a rear wall tube needs to be plugged, cut thetube 3 to 4 inches from the headers or at other cutoffpoints specified in the manufacturer’s technicalmanual. Use a plastic refractory to plug casingopenings, to cover exposed areas not protected byfirebrick or high-temperature castable refractory, andto cover the exposed pressure parts previously cooledby the plugged tube. Rear wall tubes that have beenplugged should be replaced at the earliest opportunity.

Superheater screen 1 1/2 and 2 inches in outsidediameter should, in general, be replaced, rather thanplugged, when tube failure occurs.

In plugging generating tubes 1 inch and 1 1/4inches in outside diameter behind the superheater tubebank (in single-furnace boilers) and behind the 2-inchtubes (in double-furnace boilers), consider gas laningand drum protection. Any complete lane through thetube bank more than three tube rows wide should beretubed, especially if such a lane is bounded by theboiler casing. Any drum area greater than 4 inchessquare should have refractory protection over the drumor, if this is not practicable, have blind nipples replacethe failed tubes instead of just plugging the failedtubes. The blind nipples give greater protection to thedrum than plugged tubes.

If an economizer element develops a leak, the endsof the element should be plugged at the inlet header andat the outlet header. To install a tapered plug in aneconomizer element, screw the plug extractor into theplug and insert the plug into the tube. Unscrew andremove the extractor from the plug. Drive the plugsecurely into position by holding one end of a piece ofpipe against the plug and striking the pipe on the otherend.

Figure 2-14.—Removing plug from economizer element.

plug. Place the handhole plate binder in position overthe extractor, and then thread on the handhole fittingnut. As you tighten the handhole fitting nut, the plugpulls out.

Some activities, using boilers of recent design, arefurnished with expandable gasketed plugs forplugging economizer elements. One of these plugs isshown in figure 2-15. The installation of theexpandable plug is shown in figure 2-16. Afterinserting the plug assembly into the tube, hold ascrewdriver in the slot of the retainer stem to keep the

Figure 2-15.—Expandable gasketed plug for economizerelement.

Figure 2-16.—Installing expandable plug in economizerFigure 2-14 shows how to remove a plug from aneconomizer element. Screw the plug extractor into the element.

2-13

floor may need repairing. The procedure for this repairis as follows:

Figure 2-17.—Removing expand able plug from economizerelement.

plug from turning, as you tighten the nut. As youtighten the nut using an open-end wrench or a socketwrench, the gaskets expand radially, as they arecompressed axially.

The removal of an expandable plug is shown infigure 2-17. Insert a socket wrench or an open-endwrench through the handhole and remove the retainernut. Insert the economizer plug extractor and thenthread it onto the retainer. Place the handhole platebinder in position over the extractor and the thread onthe handhole fitting nut. As you tighten the nut, theplug pulls out.

Q5.

Q6.

Q7.

Q8.

Q9.

What five items of information are generallyrequired on boiler tubes?

When tubes on a boiler drum or header made of4-6 choromium steel are removed what methodof removal cannot be used?

When tubes are fitted, tubes up to 2-inch-outsidediameter should project how far into the drum orheader?

Tubes 2 inches or larger should be belledbetween what size range?

What should you do to a plugged boiler tube toavoid pressure buildup in the tube when theboiler is operating?

REPAIRING BOILER REFRACTORIES

Learning Objective: Recognize maintenance andrepair procedures for boiler refractories.

Furnaces are built with high-grade, fire-resistantmaterials that take a lot of punishment. Sooner or later,however, repairs become necessary. Furnace walls or

First, mix the mortar, using a Navy-recommended fireclay or fire cement and fresh water. Do not add anythingelse. Make the mortar rather thin and without lumps.

Inspect the bricks for flaws and evenness. Choosethe best edge for the furnace side. Dip the brick in freshwater and allow the excess water to drip off.

Now, dip one end and side of the brick into themortar, using an edgewise motion to prevent airbubbles from forming. Lift the brick from the mortarand allow the excess mortar to drip off. Do not placeany mortar on the wall or brick with a trowel.-Themortar sticking to the brick is all that is used.

If the mortar is too thick, you will not get the thinjoints that you want. The mortar should be a littlethinner than the usual wall plaster. You can feel theproper thickness with your hand. Some mortar willstick to your hand, as you lift it away from the mortar.Add more clay or water as necessary, and stir the batchoften to keep the mortar at the desired consistency.

Place the brick quickly in position in the wall andpound it in place with a wooden mallet until no mortar canbe forced out of the joints. With high-grade brick, jointscan be made less than one thirty-second of an inch thick.Joints should never exceed one-sixteenth of an inch.

With a small trowel, fill in any unevenness in thefurnace side of the seam and bead over the joints, asshown in figure 2-18. Be sure that no edges of the brickare exposed. The wall should be laid up evenly andsmoothly. Any excess mortar that protrudes from thejoints should be smoothed off with a small trowel, sothe corners of the brick are protected.

Allow the wall to dry for about 12 hours with theburner shutters open to allow circulation of air, whichpermits the escape of some of the water added to themortar. As soon thereafter as practicable, light theburner under the boiler and slowly bring the furnace upto operating temperature to bond the mortar to theadjacent brickwork.

Figure 2-18.—Cementing brick.

2-14

When inspecting the boiler, you may find cracks orholes in the furnace lining. To make necessary repairs,mix some of the fire clay you used for brick mortar intoa thick mixture. Use more mortar than you used for thebrick mortar mix. Use a trowel to apply this wash.

While standard firebrick generally is used fornormal refractory work, plastic firebrick is recom-mended for emergency patches and for building upfurnace openings. Plastic firebrick is unfired firebrickin a stiff plastic condition. It offers a particularadvantage in that, because of its plastic nature, it can bepounded into places where otherwise a firebrick ofspecial shape would be required. The fusion point ofplastic firebrick is practically equal to that of standardfirebrick. Because of the moisture in the plasticmaterial, however, a greater degree of shrinkage takesplace. This factor prevents its general use forsidewalls. It provides an excellent material, though, forrepairing brickwork, topping off side and back walls,repairing and constructing the burner openings and,general, for any part of the furnace not exposed totemperatures in excess of 2000°F. It is particularlyadapted for use in place of specially formed brick ofcomplicated shapes.

Plastic firebrick material, as received from thefactory, ordinarily contains enough moisture forworking. Avoid the addition of water or any foreignmaterial. In laying up, chunks of plastic just as takenfrom the can should be rammed tightly into place(preferably in horizontal layers). In general, the moresolidly the section of plastic is rammed up, the better itwill be.

As the next step, the plastic section should bevented with 3/16-inch holes. Ensure that the holesextend clear through the plastic and are not more than 2inches apart. This positioning allows deeper heatpenetration during the baking-out process. It alsopermits ready escape of the steam formed from themoisture in the plastic. Do NOT trowel the surface of anew plastic section. This tends to prevent the escape ofsteam during baking out.

The plastic section should be held in place with asmany anchor bolts as would have been provided hadstandard firebrick been used instead of plastic. Theplastic section should be air-dried. This takes from 48to 72 hours, depending upon the atmosphere. As soonas practicable after air drying, the furnace should befired with a small fire and gradually brought up tooperating temperature to complete baking out. Plasticrequires a temperature of about 2900°F to 3000°F forbaking out. If small shrinkage cracks open up, they

should be filled with fire clay. If large cracks occur,they should be filled with plastic.

When used for patches, as in the case of brickfalling out, the hole should be cleaned out to give atleast 4 inches of body thickness to the plastic brick. Inbuilding up furnace openings, the use of a metal form isdesirable. However, it is not absolutely necessary ifcare is exercised in making openings of the propershape and concentric with the atomizer at every point.If furnace openings, as built, have a smooth surface,they should be roughened with a stiff wire brush beforebaking out.

The following ways to maintain newer boilers arerecommended. The boiler is normally shipped with acompletely installed refractory. This consists of therear head (fig. 2-19), the inner door, and the furnaceliner (fig. 2-20). Follow the instructions in themanufacturer's manual for the boiler you aremain ta in ing . Where spec i f i c d i rec t ions o rrequirements are furnished, follow them.

Normal maintenance requires little time andexpense and prolongs the operating life of therefractory. Preventive maintenance through periodicinspection keeps the operator informed of thecondition of the refractory and helps guard againstunexpected downtime and major repairs.

Frequent wash coating of refractory surfaces isrecommended. A high-temperature bonding air-drytype of mortar diluted with water to the consistency oflight cream is used for this purpose. Recoatingintervals vary with operating loads and are bestdetermined by the operator when the heads are openedfor inspection.

Maintenance consists of occasional wash coatingof the entire liner. Face all joints or cracks by applyinghigh-temperature bonding mortar with a trowel or useyour fingertips. This should be done as soon as thecracks are detected. Should segments of the linerbecome burned out or broken, replace the entirerefractory. Any refractory that may break out should beremoved as soon as detected, so it will not fuse to thebottom of the furnace and obstruct the burner flame.

Remove the existing refractory and thoroughlyclean that portion of the furnace covered by the liner toremove all old refractory cement or other foreignmaterial to ensure the new liner seats firmly to thesteel. Inspect all furnace metal for soundness. Theremay be metal clips welded in the furnace at the extremeend of the liner. These clips were installed to preventshifting during original shipment and serve no other

2-15

Figure 2-19.—Rear door open.

Figure 2-20.—Front head open-gas-fired CB 125-150-200.

2-16

purpose. They are tack-welded in place and can beremoved when you are installing the new liner. If theyare not removed, make sure the liner has clearancebetween this clip and the end of the refractory to allowfor expansion in this direction.

Depending upon the design pressure of the boiler,the furnace may be of the corrugated type. Although itis not necessary to fill in the depressions forconvenience of installation, some or all of thecorrugation valleys may be filled with insulatingcement. The liner tile should be fitted tightly againstthe crown of the corrugations.

The furnace extension of the boiler or a dry oven isshown in figure 2-21. The throat tile should be installedflush with the front of the oven and should fit tightlyagainst its sides. The two rows of furnace tile should befitted tightly against the furnace wall. It is notnecessary to allow for expansion.

It is recommended that the tile be dry fitted, matchmarked, removed, and then reinstalled with the properamount of refractory cement. Thin joints are desirable.

Generally, it is necessary to shave a portion from oneor more tiles to obtain a fit. If a fill piece is required, cutit to fit and install this piece at the bottom of thefurnace. It is important to have a good seal between-theburner housing and the throat tile. Liberally coat-thesealing area with an insulating pulp cement orequivalent mixed with water before swinging theburner housing into place.

The rear door is a steel shell containing horizontalbaffle tiles and lined with insulation material and acastable refractory (fig. 2-19).

Burned or discolored paint on the outer surface ofthe door does not necessarily indicate refractorytrouble but may be an indication of other conditionssuch as the following:

Leaking gaskets.

Improper seal.

Door retaining bolts insufficiently or unevenlytightened.

Air line to the rear sight tube is blocked or loose.

Figure 2-21.—Furnace liner refractory—125-150-200 hp.

2-17

Repainted with other than heat-resistant paint.

Therefore, before you assume the refractoryrequires re-working. check the following:

Condition of the tadpole gasket.

The condition of the insulating cement

protecting the tadpole gasket.

Horizontal baffle tile for large cracks, breaks,

chipped corners, and so forth.

Cracks in the castable refractory at the ends of

the baffle tile.

Tightness of door bolts.

Air line to the sight tube to ensure it is clear and

all connections are tight. If necessary, blow it

clear with an air hose.

It is normal for refractories exposed to hot gases todevelop thin "hairline" cracks. This by no meansindicates improper design or workmanship. Sincerefractory materials expand and contract to somedegree with changes in temperature, they should beexpected to show minor cracks because of contractionwhen examined at low temperature. Cracks up toapproximately one-eighth of an inch across may beexpected to close at high temperature. If there are anycracks that are relatively large (1/8-inch to 1/4-inchwidth), clean and fill them with high-temperaturebonding mortar. Any gap that shows between thecastable refractory and the baffle tile should befilled-in in a similar fashion.

After opening the rear door, clean off the flangesurface of the door with a scraper or wire brush. Cleanthe surface of the refractory carefully with a fiber brushto avoid damaging the surface. Clean the matingsurfaces of the baffle tile and the boiler shell. Removeall dried-out sealing material. Wash-coat the lowerhalf of the rear door refractory before closing it. Theupper half of the door contains a lightweight insulatingmaterial similar to that used in the inner door. A thinwashcoat mixture applied gently with a brush ishelpful in maintaining a hard surface.

The front inner door is lined with a lightweightcastable insulation material. Thin "hairline" cracksmay develop after a period of time; however, thesecracks generally tend to close because of expansionwhen the boiler is fired. Here, again, a thin washcoatmixture is helpful in maintaining a hard surface. Minorrepairs can be accomplished by enlarging or cuttingout affected areas, making certain they are clean, andthen patching as required.

Should the entire installation require replacement,remove existing material and clean to the bare metal.Inspect the retaining pins and replace if necessary.Reinforcing wire suitably attached may also be used.The recommended insulation is known as Vee BlockMix and is available in 50-pound bags. Mix thematerial with water to a troweling consistency. Mixingshould be completely uniform with no portion eitherwetter or drier than another. Trowel this mixture intoany areas that are being patched. If replacing completeinsulation, begin at the bottom of the door and applythe mixture to a thickness equal to the protectingshroud. With a trowel, apply the mixture horizontallyback and forth across the door in layers until therequired thickness is reached. Allow the mixture toair-dry as long as possible. If immediate use of theboiler is required, fire as slowly as possible to avoidrapid drying of the material.

Whenever the front or rear door is opened forinspection, the head gasket should be checked forhardening and brittleness. Doubtful gaskets should bereplaced. Coat the gasket with an oil and graphitemixture before closing the door. Make certain allgaskets retaining rivets are in place. The flange of thedoor should be clean and free of any hardened cement,scale, and so forth. Check the condition of the ropegasket used as a baffle seal. Replace if necessary. If therope is in good condition, liberally coat it with aninsulating pulp before closing. Make sure the rope isproperly positioned.

If it is necessary to replace the rope, wire brush thetube sheet area to remove all of the old sealingmaterial. Place a new piece of 1 1/2-inch-diameter ropegasket on the lip of the baffle tile. Hold it in place withfurnace cement or an adhesive.

NOTENOTE

Earlier models have several steel barsegments tack-welded across the tubesheet to serve as a gasket retainer for5/8-inch-diameter rope. It is suggestedthat these bars are removed and 11/2-inch-diameter rope be used.

Generously apply a seal, consisting of a pulpmixture of insulating cement and water, around theentire rear door circumference. Place the pulp aroundthe inside diameter of the head gasket, as shown infigure 2-16. Also coat the tube sheet area adjacent tothe baffle tile. When the door is closed, the pulpcompresses to protect the tadpole gasket and to form a

2-18

seal between the refractory surface and the tube sheet.The insulating pulp seal is not needed or used on the fronthead. Make sure the gaskets are in position when closing.

When you are closing the door, bolts should besnug and tightened evenly to avoid cocking the doorand damaging the gasket. Start tightening at the topcenter bolt and alternate between the top center boltand the bottom center bolt until both are drawn-uptight. Do not overtighten. Continue the tighteningsequence along top and bottom, tightening the boltsalternately until the door is secured and gas-tight. Afterthe boiler is back in operation, retighten the bolts tocompensate for any expansion.

Q10.

Q11.

Q12.

When plastic firebrick is used, troweling the newsection of refactory will cause what condition tooccur during the baking-out process?

What temperatures are required to bake outplastic firebrick?

Leakage of combustion gases, loss of heat, andloss of operating efficiency can be caused bywhat condition?

BOILER OPERATIONS

Learning Objective: Recognize different boilerchecks, start-up, securing procedures, and boileremergencies. Understand the purpose and types of datain boiler operating logs.

Proper sealing of the doors is essential toavoid leakage of combustion gases and

NOTE

loss of heat and operating efficiency.

The operation of a boiler consists of seven majorphases: (1) prewatch assumption checks, (2)preoperating checks, (3) lining up systems, (4)operating procedures, (5) operating checks, (6)securing procedures, and (7) boiler emergencies.

PREWATCH ASSUMPTIONCHECKS

The prewatch assumption checks are oftenneglected by boiler watch standers. Before you assumethe responsibility of a boiler watch stander, you mustcomplete specified checking procedures to ensure thatthe equipment in service is in sound operatingcondition and is functioning satisfactorily. When the

watch is relieved, the watch stander coming on dutyinspects the instrument readings and charts, visuallyinspects all equipment, and exchanges informationwith offgoing watch standers. Oncoming watchstanders should complete the following inspectionsand tests before assuming duty:

Visually inspect the setting and casting.

Observe the furnace and firing conditions.

Inspect the charts, logs, controls, and so forth, onequipment performance during previous watch.

Inspect the fans, dampers, damper drives, andother driven auxiliaries.

Test the water columns and gauge glasses.

Obtain information from the watch standers onduty on the boiler operating condition and anyunusual event or trouble that occurred during theprevious watch.

Immediately after accepting the operationalresponsibility, you should make a complete inspectionof all auxiliary equipment as follows:

Inspect all electric motor drives for abnormaltemperature, condition of bearings, and so forth.

Inspect the fan and pump bearings foroverheating and adequacy of lubrication.

Visually inspect the boiler and all associatedequipment, listen for unusual sounds, friction,vibration, and other abnormal conditions.

Inspect the burners, fuel supply, pilot systems,and other fuel supply components.

Review the log sheets to obtain information onpast operating conditions and unusual events.

REOPERATING CHECKS

The preoperating checks should be completedbefore lining up and lighting off a boiler. These checksare performed to ensure that the plant and associatedequipment are in a safe and efficient operablecondition. The major preoperating proceduresapplicable to boilers in general, as well as additionalprocedures for gas-fired and oil-fired boilers areshown in tables B, C, and D, appendix II.

LINING UP SYSTEMS

After you have completed the preoperatingchecks, your next job is to line up the boiler systems.The procedure used in lining up boiler systems (fuel,

2-19

water, steam, and electrical) vary with different typesand kinds of boil ers. Always follow the manufacturer'sinstructions for the boiler being used. Before lining upa boiler, complete the following basic tasks:

1. Fuel oil

a. Measure with a stick or gauge.

b. See that the proper valves are open.

c. Remove any excess accumulation of water inthe tank.

2. Gas

a. Check the pressure.

b. Check for leaks.

3. Gas-fired unit

a. Check and regulate the water level and line upthe feed system.

b. Examine the burner, control valves, and safetyshutouts for proper working condition beforelighting off.

c. Purge air out of the gas lines by external ventsbefore lighting off.

d. Check the draft devices and purge thecombustion chamber.

e. Light the pilot and set the flame.

f. Open the main gas cock.

g. Close the burner controls switches to light theburner.

h. Maintain the fuel-air ratio for completecombustion.

4. Oil-fired unit

a.

b.

c.

Check and regulate the water level. Line up thefeedwater system. Check the operation of thefeed pump.

Line up the fuel oil system.

Purge the combustion chamber.

d. Close the burner control switch; if automatic,the burner should light off.

e. Should ignition fail, the furnace must bepurged before a second attempt is made.

f. Do not allow oil to impinge on brickwork orpart of the boiler.

g. Maintain the proper air-fuel ratio.

In general, the basic lighting off procedures formost boilers are as follows:

1. Close the following valves:

a.

b.

c.

d.

e.

f.

g.

h.

All blowdown valves and boiler drains.

Chemical feed valves.

Boiler nonreturn.

Main steam stops.

Soot blower header (steam system) and all sootblowers.

All burner fuel valves.

Water column and feedwater regulator drains.

Auxiliary valves, as necessary.

2. Open the following valves:

a.

b.

C.

d.

e.

f .

g.

h.

3 .

4 .

5.

6.

7.

8.

9.

Vent valves on boiler drums and superheaters.

Superheater drain valves.

Recirculating line valves in economizer, if sofitted.

Feedwater stop and check.

Drum steam gauge connection.

Water column gauge connections.

Water column gauge glass valves.

Auxiliary valves, as necessary.

Start filling the boiler with properly treatedwater at a temperature close to the temperatureof the pressure parts. The temperaturedifference should not be greater than 50°F toavoid severe temperature stresses. Fill the boilerto level just below the middle of the glass on thewater column.

Close the induced draft fan dampers (or otherflue gas control dampers).

Start the induced draft fan.

Close the forced draft fan dampers (or other aircontrol dampers).

Start the forced draft fan.

Start the air heater rotor, if a regenerative type ofair heater is installed.

Light off the boiler under the manufacturer’sinstructions and maintain a firing rate so thewater temperature in the boiler is raised 100oFper hour until operating pressure is reached. On

2-20

10.

11.

12.

14.

15.

16.

13.

new boilers, expansion movement should bechecked to see that no binding or interferenceoccurs.

When burning oil, prevent incompletecombustion in the furnace: Unburned oil isdeposited on the cooler surfaces in the back ofthe unit, such as the economizer and air heater,and this creates a potentially dangerouscondition.

When the steam drum reaches about 25 psig,close the vent valves on the boiler drum. Checkthe steam pressure gauge now to be sure that it isregistering.

Ease up on the stem of the main steam stop valveto prevent any serious expansion stresses. Ifthere is no steam on either side of the main steamstop valve, gently lift and reseat it to make surethat it is not stuck. Open the drain valve on theboiler side of the main stop valve.

Observe the water level carefully to ensure thatno water is carried over into the superheater.Maintain a normal water level in the drum byblowing down or feeding water as may berequired.

Operate the vent and drain valves in thesuperheater headers and economizer byfollowing the manufacturer’s instructions. Ingeneral, drain valves in the superheater inletheader are closed first, followed by the drains inthe superheater outlet header. In any case, thesuperheater outlet header drain and vent valvesmust not be completely closed until enoughsteam flow through the boiler outlet valve isassured.

Check for leaking gasket joints. If a leakinggasket is discovered, shut down the boiler andtighten the joints.

If the gasket still leaks, drop the pressure again,replace the gasket, and repeat the lighting offsequence.

Before cutting in the boiler, proceed as follows:

1. Open all drain valves between the boiler and theheader, especially the drains between the boilerand the two stop valves.

2. Warm up the steam line between the boiler andthe header by backfeed through the drip line orby means of the bypass valve.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

When the steam line is thoroughly heated and atheader pressure, open the bypass valve.

When the boiler pressure almost reaches linepressure, open the bypass line around the mainsteam stop valve to equalize pressures andtemperatures in the piping; then slowly open themain steam stop valve. As the boiler reaches linepressure and is actually steaming, slowly raisethe nonreturn valve stem to the full openposition.

After the boiler is on line, close all superheaterdrains.

Inspect the entire boiler, and close any drainvalves that are not discharging condensate.

Close the economizer-recirculating valve whenan adequate continuous feedwater flow isestablished.

Close the drain valve at the nonreturn valve.

Close the bypass valve around the nonreturnvalve.

A boiler with a pendant (nondrainable)superheater has a slightly different operation.Superheaters of this type trap condensate in theloops that must be boiled off before the firingrate can be increased and the steam flow started.

Maintain a constant firing rate. The strength ofthick steam drums may be impaired byexcessive temperature differentials between thetop and the bottom of the drum, if the properfiring rate is not maintained. Tubes may startleaking at rolled seats and the superheater tubesmay overheat.

On boilers generating saturated steam, followthe above instructions for removing air andcondensate.

OPERATING PROCEDURES

Success in operating boilers depends largely uponthe operator’s performance. No fixed set of rules can beestablished to fit all conditions. Consequently, theoperator must see and interpret all prevailing operatingconditions and, if necessary, take action to control,modify, or correct them. To be able to do this, theoperator must be thoroughly familiar with thecharacteristics and standard operating procedures forthe boiler for which the operator is responsible. Thissection acquaints you with some of the basic operatingprocedures that generally apply to most, if not all,

2-21

boilers you will be assigned to operate. For specificoperating instructions, consult the manufacturer’smanual for the boiler concerned.

Normal Operation

During normal operation of boilers, the operatorshave two major responsibilities. First is to maintainproper water level at all times. If the water level is toolow, tubes may overheat, blister, and rupture. If waterlevel is too high, carry-over of water to the superheatertubes may damage the superheater elements and theturbine. The second is to prevent loss of ignition whenburning fuel is in suspension. Maintain safe andefficient combustion conditions in the furnace andcorrect fuel-air ratios.

Blowdown

Establish definite intervals for blowing down theboiler, depending on the type of operation andchemical analysis of the boiler water. During regularoperation, never blow down economizers orwater-cooled furnace walls. Blowdown valves on thistype of equipment serve only as drain valves.

Blowdown should be at reduced or moderaterates of steam for low point drains or blowdownvalves. When the water glass is not in full view of theoperator blowing down a boiler, another operatorshould be temporarily assigned to observe the waterglass and signal the operator handing the valves. Forcontrol of water conditions when working, usecontinuous blowdown to maintain the properconcentration at all times and to prevent blowingdown large quantities of water while the boiler isoperating at a high capacity.

1. Flue-gas temperature

a. Keep the temperature low.

b. Temperature should be about 150 degreeshigher than temperature of steam produced.

2. Flue-gas analysis

a. Take periodically.

b. Maintain proper CO;! level for fuel used.

3. Flame

a. Should be long and lazy.

b. Must not enter the tubes.

c. Not dark and smoky.

d. Have a light brown haze from stack, except

gas.

e. When the fuel is oil, have a yellow flame withdark or almost smoky tips.

4. Draft

Boiler Makeup Water a. Usually 0.03-0.06 inch of water.

Use only properly treated water for makeup, andmaintain the boiler water conditions as specified inwater treatment instructions. Make an accurate wateranalysis at specified intervals. Carefully control theblowdown and the addition of treatment chemicals tomeet the manufacturer's specifications.

b. Check the manufacturer‘s recommendations.

5. Makeup feed

a. Maintain low rate.

b. Avoid excessive boiler blowdown.

6. Insulation

Soot Removal

Remove soot from hoppers and pits at definitelyestablished intervals, as necessary.

a. Ensure boiler and lines are well insulated.

7. Water treatment

a. Carry out prescribed treatment of boiler water.

Instrument Readings

Establish definite intervals for observing andrecording the readings on all important instrumentsand controls. Be sure you obtain accurate readings-andsee that the readings are recorded properly on the logsheet or other required record.

OPERATING CHECKS

To help ensure efficient operation of the boiler,operators should ensure that proper operating checksare done during boiler operations. Operating checks, asshown in table E, appendix II, apply to most, if not allboilers.

Keys to efficient boiler operation and performanceare as follows:

2-22

SECURING PROCEDURES

The recommended procedures for securing boil

are as follows:

1. Reduce the load on the boiler slowly, cutting

ers

outthe fuel supply by proper operation of thefuel-burning equipment.

2. Maintain normal water level.

3. When the boiler load is reduced to about 20% ofrating, change the combustion control and thefeedwater control to manual operation.

4. Before securing the final fuel burner, open thedrain valves at the steam and nonreturn valveand the drain valve on the superheater outletheader. Be sure the bypass valve around thenonreturn valve is closed.

5. Secure the final fuel burner when the load hasbeen reduced sufficiently.

6. Continue operating the draft fans until the boilerand the furnace have been completely purged.

7. Shut down the draft fans.

8. Close the dampers, including the air heater andsuperheater bypass dampers, when provided.

9. Follow the manufacturer’s instructions for therate of cooling the boiler. A thermal strain mayoccur if the change is too fast.

10. When the boiler pressure has started to drop,close the steam stop and nonreturn valve.

11. When the boiler no longer requires any feed andthe nonreturn valve is closed, open the valve inthe recirculating connection of the economizer,if provided.

12. Let the boiler pressure drop by relieving steamthrough the superheater drain valve and thedrain valve at the nonreturn valve. If the boiler islosing pressure at a rate faster than specified bythe manufacturer, throttle the drain valves asnecessary to get the proper rate. Do not close thevalves completely.

13. When the drum pressure drops to 25 psig, openthe drum vent valves.

14. If a regenerative type of air heater is used, therotor may be stopped when the boiler exit gastemperature is reduced to 200°F.

15. The boiler can be emptied when the temperatureof the boiler is below 200°F. Before sending

someone into any part of the boiler, close andproperly tag all controls, valves, and drains orblowdown valves connected with similar partsof other units under pressure at the time. Thismove prevents any steam or hot water fromentering the unit. The tags are to be removedonly by the authorized person who tagged outthe boiler and must remain in place until thework is completed. Ventilate the boilerthoroughly and station a person outside. Inside,use only low voltage portable lamps providedwith suitable insulation and guards. Even 110volts can kill under the conduction conditionsinside a boiler. All portable electrical equipmentshould be grounded; and electric extensioncords should be well insulated, designed towithstand rough usage, and maintained in goodcondition.

BOILER EMERGENCIES

Typical emergency situations encountered withthe operation of boilers are (1) low water, (2) highwater, (3) serious tube failure making it impossible tomaintain water level, (4) flarebacks caused by anexplosion in the combustion chamber, (5) minor tubefailure indicated by trouble in maintaining water levelunder normal steam demand, and (6) broken gaugeglass on the water column. Table F, appendix II, liststhe safe procedures to follow when these boileremergencies occur.

BOILER OPERATING LOGS

The main purpose of boiler operating logs is torecord continuous data on boiler plant performance.Logs become a source of information for analyzing theoperation of the boiler for maintenance and repair. Thedaily operating log sheets provide the basicinformation around which maintenance programs aredeveloped. The log is arranged for use over a 24-hourperiod divided into three 8-hour shifts. Log sheets varyamong different activities, but you should have nodifficulty in making log entries once you understandwhat information is required. The types of informationto be entered in the appropriate column of the log are asfollows:

Steam pressure. Based on steam gauge readingsand indicates the performance of the boiler.

Steam flow. Actual output of the plant, in poundsper hour, to obtain steam flow. The data from theseentries are used to determine the number of boilers tooperate for greatest efficiency.

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Feedwater heater pressure. Indicates whether theproper deaerating temperature can be maintained in theheater.

Feedwater heater temperature. Shows theeffectiveness of the feedwater heater. A drop insteam-supply pressure or insufficient venting maycause low heater temperature.

Feed pump pressure. Indicates the effectivenessof the boiler feed pumps. If the feedwater supply fails,the pressure reading enables the operator to determinewhether the trouble is in the feed pumps. Pumps aredefective when the feed pump pressure reading is belownormal.

Last-pass draft. Indicates the actual draftproduced by the stack or the induced-draft fan. Adecrease in the last-pass draft with other conditionsconstant indicates leaking baffles. An increase showsgas passages are becoming clogged.

Percent CO2 flue gas. This value is a measure ofrelative quantities of air supplied with fuel. It is kept at avalue that has been established as most satisfactory forthe plant, fuel, firing rate, and other related factors. Inplants not equipped with CO2 recording meters, thisvalue is determined with a hand gas analyzer.

Flue gas temperature. Shows the quantity of heatleaving the boiler with flue gases. This heat represents adirect energy loss in fuel. Dirty heating surfaces orleakage of baffles causes high flue gas temperatures.Excessive fouling of firesides of boilers increases draftloss, while leaking baffles decrease draft loss. Eithercondition raises the temperature of flue gas abovenormal.

Fuel. Fuel oil quantities are determined by theuse of a measuring stick and tables supplied with a giventank. Some tanks are equipped with gauges to show thefuel volume. Always determine the quantity of fuelused, as this represents a major operating cost.

Outside temperature. The load on a heating plantis greatly influenced by outside temperature. Recordthis temperature for comparison with steam generatedand fuel used. These comparative values are useful infinding abnormal fuel consumption and in estimatingfuture requirements.

Makeup water. Record the quantity of makeupwater used to enable the operator to note an abnormalincrease before a dangerous condition develops. Returnall possible condensate to the boiler plant to save waterand chemicals used to treat water.

Water pressure. Indicates whether water issufficient.

Hot-water supply temperature. Insufficientlyheated water can cause scaling or deposits in aboiler.

Water softeners. Where softeners are used, adecrease in the quantity of time used for runs betweenregeneration indicates either an increase in hardness ofincoming water or a deterioration of softeningmaterial.

Total and average. Space is provided forrecording the total and average quantities per shift.

Steam flowmeter. The steam flowmeterintegrator reading at the end of a shift and multiplied bythe meter constant gives the quantity of steamgenerated. Dividing steam generated by fuel burned(gallons of oil) yields a quantity that shows the economyobtained. If a plant does not have a steam flowmeter,pumps can be calibrated for flow and a record kept oftheir operating time or condensate and makeup watercan be metered.

Boiler feed pumps in service. Makes it possibleto determine operating hours and to ensure that variouspumps are used for equal lengths of service.

Phosphate, caustic soda, and tannin added. Isvaluable in keeping the correct boiler water analysis andin determining total chemicals used.

Remarks. The Remarks column is used to recordvarious types of information for which space is notprovided elsewhere on the log sheet. Note irregularitiesthat are found during inspections, dates boilers aredrained and washed out, equipment to be checked daily,and so forth.

Other personnel . Names of personnelresponsible for specific tasks and data must be enteredon the log sheet, if required.

Q13. Why are prewatch assumption checksperformed?

Q14. What is the next step after completingpreoperating checks?

Q15. What is the first step to be taken when cutting inthe boiler?

Q16. What are the two major responsibilities ofboi ler operators during normal boi leroperations?

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Q17.

Q18.

Flu-gas temperatures should be at how many

degrees above steam production temperature

during boiler operations?

When securing a boiler, at what pressure should

you open the drum vent valves?

Q19. What is the purpose of a boiler operating log?

SAFETY

Learning Objective: Understand the relationship of

safety in operating and maintaining boilers. Recognize

the different types and use of lockout devices in boiler

maintenance.

In servicing boilers, the need for SAFETY cannotbe overemphasized. Much progress has been madeover the years in the development of safety devices forboilers. There are still many ways, however, in whichserious accidents can happen around boilers. A boileroperator or serviceman who is careless on the jobthreatens the safety of everyone. Accidents somehowhave a way of happening at a moment we least expect.All the more reason, therefore, for constant alertnessand close attention to detail. Do not take chances! BESAFETY CONSCIOUS!

Some of the major safety precautions to beobserved by Utilitiesmen engaged in boiler operationand servicing are presented below.

As protection against toxic or explosive gases,boiler settings must be ventilated completely andtested for toxic or explosive gases before crews arepermitted to enter.

The covers of manholes must be removed forventilation before people enter the drum.

Before anyone enters a steam drum, mud drum, orother waterside enclosure, steam and feed linesconnected to the headers under pressure should beisolated by a stop valve and a blank with an opentelltale valve in between, or by two stop valves with atelltale valve opened in between.

A ventilating fan should be operating in the drumwhen someone is working in the boiler.

Workers should not be inside the waterside of theboiler when pressure is being applied to test a valvethat has not been under pressure.

Workers should wear protective clothing whenmaking boiler water tests.

Boiler settings must be examined daily for externalair leaks. Cracks, blisters, or other dangerousconditions in joints, tubes, seams, or blowoffconnections are to be reported to your senior chiefpetty officer immediately.

Boilers should also be examined regularly fordeposits on their heating surfaces and for grease orother foreign matter in the water. Boilers showing anysuch faults should be cleared at the first opportunityand should not be used until cleared.

Performing certain adjustments and repairs whilepressure is up is prohibited. A complete absence ofpressure is to be ensured by opening the air cock or testand water gauge cocks connecting with the steam spacebefore fittings or parts subject to pressure are removed ortightened, and before manhole or handhole plate fittingsare loosened on a boiler that has been under pressure.

large warning sign, such as Caution-Man WorkingInside, should be placed near the furnace entrance.

The use of open-flame lights is prohibited inboilers. When cleaning where flammable vapors andgases may be present, workers are to use onlyexplosionproof portable lamps equipped with heavilyinsulated three-wire conductors, with one conductorconnecting the guard to ground.

Safety-toed shoes or toe guards must be worn toprevent injuries from falling slag.

When someone is working inside the furnace, a

a respirator must be worn.When a worker is chopping slag inside a furnace,

Hard hats and goggles must be worn.

When cleaning operations are performed, workersshould wear the proper personal protective equipment.The following requirements apply:

Combustion control, feed control, and burner,stoker, or similar adjustments are permitted with theboiler steaming, since many adjustments can be madeonly when pressure is up.

Oil accumulated on furnace bottoms should becleaned out immediately.

The fuel-oil suction and discharge strainersshould be cleaned at least every 8 hours and morefrequently if necessary.

Condensate pits in boiler rooms should havemetal covers. If the pits must be opened formaintenance, adequate guards should be placed aroundthem and warning signs posted.

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Wear goggles with dark lenses, Number 1.5 to 3shade, and suitable fireproof face shields when workingnear or looking through furnace doors of boilers inoperation.

When firing a cold boiler, be sure that the airvents are open on the boiler proper and that the drainsare open on the superheater; keep these open until steamis liberated from the openings. Superheater vents mustremain open until the boiler is on the line.

Be sure gas-fired and oil-fired boilers, whethermanual or automatic, are cleared of combustible gasesafter each false start.

All semiautomatic (multiburner) boilers and allfully automatic boilers should be equipped with amanually activated switch for pilot ignition and acontrol device to prove the pilot flame is on before themain fuel valve is opened. DO NOT USE A HANDTORCH TO LIGHT OFF A BOILER. If a hand torch isapplied to a firebox filled with vaporized oil, a severeboiler explosion is likely to occur.

Prevent overheating of boilers equipped withsuperheaters by. firing at a slow rate during thewarm-up period and by allowing a small amount ofsteam to flow through the superheater.

When taking over a watch, blow the water gaugesand note the return of the water in the glass. Be certainof the water level at all times. Do NOT be misled by adirt marking on the gauge that may look like thesurface of the water. Do NOT depend entirely uponautomatic alarm devices and automatic feedwaterregulators.

If the water goes out of sight in the bottom of thegauge glass, kill the fire with the quickest meansavailable; immediately close the steam stop valve, andallow the boiler to cool slowly; then, drain the boilercompletely and open it for inspection. DO NOT FEEDCOLD WATER TO A BOILER THAT HAS HADLOW WATER UNTIL THE BOILE R H A SCOOLED.

Check safety valves often to be sure they will popat the correct pressure, as marked on the nameplate. DoNOT break the seal of a safety valve or change itsadjustment, unless such action has been authorized.NEVER weight pop valves, relief valves, and so on, toincrease the recommended steam pressure for whichthe boiler is approved.

Check the water on steaming boilers by try cocks atleast once each watch and before connecting a boiler tothe line.

Do not use oil from a tank in which a lot of water ismixed with oil unless a high suction connection isprovided. When an atomizer sputters, shift the suctionto the standby tank or another storage tank. Asputtering atomizer indicates water in the oil.

Reduce the fouling of oil heaters by using as fewheaters as possible. Recirculate the oil through theused heaters for a short time after securing the burners.Maintain the prescribed fuel-oil temperature; do NOTexceed it.

If a large steam leak occurs in a boiler, shut off theburners, continue to feed water until the fire is out,close the steam stop valve, ease the safety valves, clearthe furnace of gases, close the registers, and cool theboiler slowly.

Do NOT tighten a nut, bolt, or pipe thread, norstrike any part, nor attempt other adjustments to partswhile the boiler is under steam or air pressure.

Take care to prevent lubricating oil, soap, or otherforeign substances from getting into the boiler.Condensate from cleaning vats should be drained towaste and not returned to the boiler.

Close the furnace openings as soon as all fires havebeen put out and the furnace has been cleared of gases.

At shore installations, the handles on pull chains toboiler water-gauge cocks and water-gauge glass stopvalves should be painted the following colors:

Opening water-gauge glass stop valves WHITE

Closing water-gauge glass stop valves RED

Top gauge cock YELLOW

Center gauge cock GREEN

Bottom gauge cock BLUE

Do NOT use water to put out an oil fire in thefurnace.

When fires are banked, make certain the draft isenough to carry off flammable gas accumulations.

The following lists contain a number of actions towhich you should ALWAYS be alert and a number ofactions you should NEVER perform.

SAFETY PRECAUTIONS

know exactly what action to take.Always study every conceivable emergency and

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Always proceed to proper valves or switchesrapidly but without confusion in time of emergency.You can think better walking than running.

Always check the water level in the gauge glasswith the gauge cocks at least daily—also at any othertime you doubt the accuracy of the glass indication.

Always accompany orders for importantoperations with a written memorandum. Use a logbookto record every important fact or unusual event.

Always have at least one gauge of water beforelighting off. The gauge cocks should check the level.

Always be sure the blowdown valves are closed,and proper vents, water-column valves, andpressure-gauge cocks are open.

Always use the bypass if one is provided. Crackthe valve from its seat slightly and await pressureequalization. Then open it slowly.

Always watch the steam gauge closely and beprepared to cut the boiler in, opening the stop valveonly when the pressures are nearly equal.

Always lift the valve from its seat by the hand leverwhen the pressure reaches about three quarters ofpopping pressure.

Always consult the CEC officer in charge of theplant, your CPO, or other proper superior and accepthis/her recommendations before increasing thesafety-valve setting.

Never fail to anticipate emergencies. Do not waituntil something happens before you start thinking.

Never start work on a new job without tracingevery pipeline in the plant and learning the locationand purpose of each and every valve regardless of size.Know your job!

Never leave an open blowdown valve unattendedwhen a boiler is under pressure or has a fire in it. Playsafe, your memory can fail.

Never give verbal orders for important operationsor report such operations verbally with no record. Havesomething to back you up when needed.

Never light a fire under a boiler without checkingall valves. Why take a chance?

Never open a valve under pressure quickly. Thesudden change in pressure, or resulting water hammer,may cause piping failure.

Never cut a boiler in on the line unless its pressureis within a few pounds of header pressure. Suddenstressing of a boiler under pressure is dangerous.

Never bring a boiler up to pressure without tryingthe safety valve. A boiler with its safety valve stuck isthe same as playing with dynamite.

Never increase the setting of a safety valve withoutauthority. Serious accidents have occurred fromfailure to observe this rule.

In case of an oil fire in the boiler room, close themaster fuel-oil valve and stop the oil pump.

Other than the above precautions, the followinglist contains a number of SAFE practices that youshould try to follow in your work. It also contains anumber of UNSAFE practices that you must avoid.

SAFE PRACTICES

Always have the valve fitted with a new spring andrestamped by the manufacturer for changes over 10percent.

Always keep out loiterers, and place plantoperation in the hands of proper persons. A boiler roomis not a safe place for a club meeting.

Always consult the CEC officer in charge of theplant, your CPO, or other proper superior beforemaking any major repair to a boiler.

Always allow the draft to clear the furnace of gasand dust for several minutes. Change draft conditionsslowly.

Always consult someone in authority. Two headsare better than one.

UNSAFE PRACTICES

Never change adjustment of a safety valve morethan 10 percent. Proper operation depends on theproper spring.

Never allow unauthorized persons to tamper withsteam plant equipment. If they don’t injure themselves,they may injure you.

Never allow major repairs to a boiler withoutauthorization.

Never attempt to light a burner without venting thefurnace until clear. Burns are painful.

Never fail to report unusual behavior of a boiler orother equipment. It may be a warning of danger.

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LOCKOUT DEVICES

A lockout device is a mechanism or arrangementthat allows the use of key or combination locks (mostcommonly padlocks) to hold a switch lever or valvehandle in the OFF position. Some switches and valveshave lockout devices built in; others must be changedbefore locks can be used. As a Utilitiesman, you mayuse lockout devices when working on potentiallyhazardous equipment, such as high-pressure steamlines, electrically operated equipment, and boilers. Theuse of a lockout device is a great advantage since themachine or equipment cannot be started up, energized,or activated while you are working on it. Thephotographs in figure 2-22 will give you an idea ofhow devices may be used in locking out valves.

Multiple Lock Adapter

It is often an advantage for a lockout device toaccommodate more than one padlock. In this way,when you are working on a machine or an item-ofequipment with the valve locked off, another personcan come along and use the padlock to do otherhazardous work on the machine or equipment at thesame time, rather than wait until you are finished.

Since most controls are not designed toaccommodate more than one padlock at a time,multiple lock adapters, called lockout clamps or tongs,may be used (fig. 2-23). These adapters should bepermanently chained to the control, or, alternately,issued to all people with padlocks.

Figure 2-22.—Locking out valves.

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Figure 2-23.—Multiple lock adapters.

Locks

Perhaps you are wondering what kind of lock

should be used—key or combination? What person

should have a lock? Who should be in possession of

the keys or combinations? How should the lock be

identified? The answers to these questions may vary

from one activity to another, but some guidelines are as

follows:

1. Key-operated padlocks are more commonlyused than combination locks. Supervisors can controlkeys easier than combinations.

2. Locks should be issued to every person whoworks on closed-down equipment. No key (orcombination) should fit more than one lock.

3. Only one key should be issued to a person

authorized to use the lock. At some activities, the

supervisor may be permitted to maintain a duplicate set

of keys for locks under his/her control, or a master key.

Some activities, however, may have only one lock-one

key. In an emergency, bolt cutters may be used to

remove a lock. As a word of caution: KEYS AND

LOCKS SHOULD NEVER BE LOANED.

4. Locks should identify the user by name, rate,

and shop. This information can be stamped into the lock

case, stenciled on, or carried on a metal tag fixed to the

shackle of the lock. In addition, locks may be color

coded to identify the skill or rating of the lock folder,

such as UT, CE, or CM. The colors could also follow the

hard hat color code.

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Lockout Procedures

If locks, lockout devices, and multiple lockadapters are to be effective, they must be used properlyon every occasion where they are needed. Make surethat you follow the steps of the lockout procedurebelow.

1. Before any equipment is locked out, thereshould be agreement as to the specific machine or unit tobe taken out of operation. The supervisor shouldoversee lockout procedures.

2. Turn off the point-of-operation controls.(Remember that disconnect switches should never bepulled while under load because of the possibility ofarcing or even explosion.)

3. See that the main power controls (switch,breaker, or valve) are turned OFF. Where electricalvoltages are involved, do NOT attempt this yourself buthave it done by a Construction Electrician.

Q20.

Q21.

Q22.

Q23.4. After the switch has been opened or the valve

closed, the person who will be doing the work shouldsnap the locks on the control lever or multiple lockadapter. At this point, tag the switch, valve, or device

being locked. Tags should indicate the type of workbeing done, approximately how long the job will take,and the name of the supervisor.

5. Try the disconnect or valve to make sure itcannot be moved to ON.

6. Try the machine controls as a test to ensure themain controls are really off.

7. As each person completes work, only thatperson should remove the lock and supplemental tag.The person removing the last lock should notify thesupervisor that the work is finished and the equipment isready to be placed back in operation.

When cleaning operations are performed, whatbasic personal protective equipment should beworn?

What color should the pull chain handle bepainted for the center gauge cock?

You should never bring a boiler up to pressureunless what valve has been tested?

Why are key-operatedpadlocks more commonlyused than a combination lock for a lockoutdevice?

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CHAPTER 3

STEAM DISTRIBUTION SYSTEMS

Learning Objective: Recognize the purpose, operating principles, andmaintenance procedures of steam distribution systems.

"What good is steam without some means oftransporting it from the steam plant to the user"? Inanswer to this question, you will find information in thischapter about steam distribution systems. A steamboiler is virtually useless for heating without a gooddistribution system for taking the steam to the areas tobe heated. In this chapter, both exterior and interiorsteam distribution systems are discussed. Alsodiscussed in this chapter are maintenance requirementsalong with the various components and their purpose inthe distribution system. The term distribution system, asused in this chapter, refers to the network of pipingrequired to distribute steam from a boiler room or aboiler plant through the steam pipes to the equipmentusing it. Steam distribution systems are grouped undertwo classifications: exterior and interior. The firstdiscussion pertains to the types of exterior distributionsystems.

EXTERIOR STEAM DISTRIBUTIONSYSTEMS

Learning Object ive: Recogn ize types andconfigurations of exterior distribution systems and theirapplication and maintenance.

The exterior distribution system is further dividedinto underground and aboveground systems.

UNDERGROUND SYSTEMS

The major underground systems are the conduit andthe utilidor types of systems. These systems arenormally installed only in permanent heatinginstallations because of their high cost of installation.

Conduit Type

In the conduit type of steam distribution system, thepipe is installed inside a conduit that is usually buried in

the ground below the frost line. The frost line is thelowest depth that the ground freezes during the coldestpart of the winter. The pipe used for steam is black steelpipe, which is not as strong as that required forcondensate return lines. The conduit and insulationserve to protect and insulate the steam pipe. One type ofconduit is shown in figure 3-1. The conduit must bestrong enough to withstand the pressure of the earth andthe usual additional loads imposed upon it.

Several types of materials and various designs areused in the manufacture of conduit. Common types ofconduit are constructed of masonry cement, galvanizediron, and steel. The conduit is usually sealed withasphaltic tar or some other type of sealer to preventwater from getting into the insulation and deterioratingit. Insulation may be attached directly to the pipe,attached to the inner surface of the conduit, or in looseform and packed between the pipe and the conduit.

The bottom of the trench for the conduit should befilled with coarse gravel or broken rock to providesupport and adequate water drainage. When water isallowed to collect, it seeps into the conduit throughporous openings in the sealer. This wets the insulationand causes it to lose much of its insulating value.Manholes are required at intervals along the line to

Figure 3-1.—One type of steam distribution conduit.

3-1

ABOVEGROUND SYSTEMS

Figure 3-2.—A typical manhole for distribution system.

house the necessary valves, traps, and expansion joints.A typical manhole is shown in figure 3-2.

Utilidor Type

The utilidors, or tunnels, of the utilidor type ofsystem are constructed of brick or concrete. The sizeand shape of the utilidor usually depend upon thenumber of distribution pipes to be accommodated andthe depth the utilidor must go into the ground.Manholes, sometimes doors, are installed to provideaccess to the utilidor (tunnel). A typical utilidor isshown in figure 3-3. The utilidor is usually constructedso the steam and condensate return lines can be laidalong one side of the tunnel on pipe hangers or anchors.This is usually done with the type of hanger with rollersthat provides for free movement required by theexpansion of the pipe. The other side of the utilidorshould be a walkway that provides easy access to lineswhen you are inspecting and doing maintenance.

Figure 3-3.—A typical utilidor.

Aboveground steam distribution systems arefurther divided into overhead and surface systems:

Overhead Distribution Systems

Overhead distribution systems are often used intemporary installations; however, they are sometimesused in permanent installations. The main drawback tothis type of distribution system is the high cost ofmaintaining it. These overhead systems are similar inmany respects to underground distribution systems.They require valves, traps, provision for pipeexpansion, and insulated pipes. The main difference isthat the steam distribution and condensate return pipingare supported on pipe hangers from poles, as shown infigure 3-4, instead of being buried underground.

Surface Distribution Systems

In some cases, you will find that steam andcondensate lines are laid in a conduit along the surfaceof the ground. These systems, however, are not ascommon as overhead and underground systems.Surface systems require about the same components asthe overhead and the underground systems—traps,valves, pipe hangers to hold the pipes in place, andprovision for pipe expansion. Sometimes an expansionloop, formed by a loop of pipe, is used instead of anexpansion joint to provide for pipe expansion.

MAINTENANCE

The maintenance required for exterior distributionsystems normally consists of inspecting, repairing, andreplacing insulation, traps, valves, pipe hangers,expansion joints, conduit, utilidors, and aluminum or

Figure 3-4.—Steam and condensate lines supported by poles.

3-2

distribution systems. The maintenance required onconduit and utilidors consists of keeping the materials ofwhich they are constructed from being damaged and ofensuring that water is kept out of the tunnels and pipes. Themaintenance required on outside metal coverings is aboutthe same as that for the conduit and utilidors.

Q1. What are the two classifications of exteriorsteam distribution systems?

Q2. Conduit and utilidor steam distribution systemsare normally installed as a permanentinstallation because of what reason?

Q3. What is the main disadvantage of an overheadsteam distribution system?

INTERIOR STEAM DISTRIBUTIONSYSTEMS

Learning Object ive: Recogn ize types andconfiguration of interior distribution systems.Understand their basic installation, operation, andmaintenance.

Interior steam distribution systems may be classifiedaccording to pipe arrangement, accessories used, methodof returning condensate to the boiler, method of expellingair from the system, or the type of control used. Theinterior steam systems discussed in this chapter areclassified according to pipe arrangment.

Steam may be fed to interior steam distributionsystems from a boiler in the same building or from theexterior distribution system of a central plant.

GRAVITY, ONE-PIPE, AIR-VENTSYSTEM

The gravity, one-pipe, air-vent system, as shownin figure 3-5, is one of the oldest types of internaldistribution systems. Its capacity is usually ample, andits installation cost is low. Because the condensate isreturned to the boiler by gravity, this system is usuallyconfined to one building and is seldom used as acentral plant distribution system. The steam issupplied by the boiler and is carried by a single systemof piping to the radiators. The return of condensatedepends upon the hydrostatic head. Therefore, the endof the steam main, where the main is drained to the wetreturn, should be high enough above the waterline toprovide the required hydrostatic head above theentrance to the boiler. The radiators in the system areequipped with an inlet valve and an air valve. The inletvalve is the radiator shutoff valve, while the air valvepermits the venting of air from the radiators.Condensate is drained from the radiators through thesame pipe that supplies the steam; they flow inopposite directions, however, which is a dis-advantage. Under certain conditions, the condensate isheld in the radiators. This causes noisy operation and afluctuating water level in the boiler. Water hammer andslow heating are characteristic of this system when thepipe sizing, pitch, and general design are inadequate.

Figure 3-5.—A gravity, one-pipe, air-vent system.

3-3

Installation You will also note that the radiator valves in

Although all gravity, one-pipe, air-vent systems arealike in design, it is seldom that two installations arealike in detail. Since the details differ with the make andmodel of equipment, it is recommended that themanufacturer’s installation procedures be followed.Also, you should follow the mechanical blueprints for aparticular installation. There is some generalinformation in this section that applies to most heatingsystems of this type.

To prevent water hammer and re-evaporation of thewater, drain all condensate from the lines. Thenecessary internal drainage can be obtained by slopingthe lines down, in the direction of condensate flow, atleast one-fourth of an inch for every 10 feet of pipe. Theradiators must also be tilted, so the condensate flows outof them into the same pipe through which the steam isentering.

Air vents are installed in the steam lines andradiators to eliminate air in the system. Air in the systemtends to block the flow of steam, and it consequentlyacts as an insulator by preventing the emission of heatfrom the heating surface. Therefore, the air must be‘quickly and effectively vented from the heatingequipment and steam lines to get quick and even heatingfrom the steam-heating system. Most steam distributionsystems are now fitted with automatic vents that permitthe air to pass but which block the passage of steam.Figure 3-5 shows air vents in the radiator and thedistribution system.

Operation

The operating instructions for gravity, one-pipe,air-vent systems vary from one installation to another.The manufacturer of the equipment usually furnishesthe specific operating instructions for the equipment.

Generally speaking, most steam systems have amain steam stop valve located on the top of the boiler.The purpose of this valve is to hold the steam in theboiler until you are ready to let it out. When you areready to turn the steam into the distribution system, youshould only crack (open very little) the valve. Thereason for doing this is to allow the system to warm upslowly and avoid any thermal shock to the lines andfittings. After the system has warmed up, the mainsteam stop valve should be opened slowly. Whileopening the valve, you should check often to ensure thatthe proper water level is maintained in the boiler.

one-pipe steam distribution systems should be eithercompletely open or completely closed. Partial openingof the valve interferes with the proper drainage of waterfrom the radiator.

Maintenance

In this portion of the text, the common problemsyou are most likely to encounter in the field whenmaintaining a gravity, one-pipe distribution system arediscussed. The most probable causes of these problemsand the remedies for them are considered.

When a radiator fails to heat or water hammeroccurs, there are several probable causes. One is thefailure of the air vents to function, thereby causing theradiator to become air bound. A second cause is that theradiator valves are not completely open. Another causeis that the radiators and lines are not correctly pitched.To remedy these causes of heat failure, you shouldinspect the operation of the air vents and the positions ofthe radiator valves to make sure they are open. Youshould then check and correct, if necessary, the pitch ofthe radiators and lines when the other checks do notcorrect the trouble.

A fluctuating waterline in the boiler can be causedby an excessive pressure drop in the supply lines, which,in turn, is usually caused by partial stoppage in thepipes. This, of course, can only be remedied byremoving the cause of the stoppage. Uneven heatdistribution is another trouble that you may encounter.This can be caused either by inoperative radiator vents,improperly vented steam mains, or incorrectly pitchedmains. To eliminate this uneven heat distribution, youshould check and clean the air vents at the radiator andthose in the steam mains. Then check and correct, asrequired, the pitch of the steam lines if the otherremedies have not corrected the trouble.

TWO-PIPE VAPOR SYSTEM WITH ARETURN TRAP

The two-pipe vapor system with an alternatingreturn trap, as shown in figure 3-6, is an improvementover the one-pipe system. The return from the radiatorhas a thermostatic trap that permits the flow ofcondensate and air from the radiator. It also preventssteam from leaving the radiator. Because the returnmains are at atmospheric pressure, or less, a mechanicalreturn trap is installed in the system to equalize thecondensate return pressure with the boiler pressure. Themechanical return trap is primarily a double-valve float

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Figure 3-6.—A two-pipe vapor system with a return trap.

mechanism, which permits equalization of the boilerpressure and the pressure within the return trap.

Installation

Vapor-steam systems with return traps are similarin design. However, it is seldom that two installationsare alike. Since the details differ with the type of heatingequipment, it is recommended that the manufacturer’sinstallation instructions be followed.

However, the mechanical return trap should beinstalled on a vertical pipe in the return system that isadjacent to the boiler. The top of the trap should be levelwith, or below, the bottom of the dry return main. Thebottom of the trap should be approximately 18 inchesabove the boiler waterline to provide a sufficienthydrostatic head to overcome friction in the returnpiping to the boiler.

Operation

The two-pipe vapor system with a return trapalternately fills and dumps. It returns condensate to theboiler by a mechanical alternating-return trap instead ofby gravity. The alternating-return trap consists of avessel with a float that, by linkage, controls two valvessimultaneously so that one is closed when the other isopen. One valve opens to the atmosphere; the other isconnected to the steam header. The bottom of the vesselis connected to the wet return.

In operation, when the float is down, the valveconnected to the steam header is closed and the other is

open. As the condensate returns, it goes through the firstcheck valve and rises into the return trap, which isnormally located 18 inches above the boiler waterline.The float starts to rise when the water reaches a certainlevel in the trap, the air vent closes, and the steam valveopens. This action equalizes the trap and boilerpressures and permits the water to flow by gravity fromthe trap, move through the boiler check valve, and gointo the boiler. The float then returns the trap to itsnormal vented condition, ready for the next flow ofreturning water.

Maintenance

The problems you are likely to encounter in main-taining the two-pipe vapor system with a return trap willdiffer with each system. Some of the more commontroubles are discussed here. For specific instructions,you should refer to the manufacturer's manual orpamphlet pertinent to each piece of equipment.

When a radiator fails to heat, the air vent beingplugged or the radiator being waterlogged because of aplugged or defective trap can cause the condition. Incase there is a plugged air vent, all you need to do isclean it. When there is a waterlogged radiator, the trapshould be checked to determine if it is plugged; also youshould check to see if the bellows is serviceable. If thetrap is plugged, then cleaning it should solve yourproblem. However, if the trap is damaged, the damagedpart, or the whole trap, must be replaced.

When the entire steam distribution system fails, thetrouble can be caused by inoperative return traps or

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inoperative check valves. The return traps and the checkvalves should be cleaned and inspected; and, ifnecessary, the defective parts or the whole unit shouldbe replaced.

TWO-PIPE VAPOR SYSTEM WITH ACONDENSATE PUMP

The two-pipe vapor system with a condensatepump, as shown in figure 3-7, is similar to the two-pipevapor system with the return trap, except that thecondensate is returned to the boiler by a power-drivencentrifugal pump, instead of by a return trap. Thissystem includes a separate main, a radiator feed at thetop, and a return system with thermostatically trappedoutlets located at the bottom of the radiators opposite tothe feed end. The return main terminates at the receiverof the condensate pump, where all of the air in thesystem is discharged to a vent on the receiver. With theuse of a condensate pump, all of the returns to the pumpare kept dry and the radiators can be located below theboiler waterline. This is not possible with the steamdistribution systems previously described. Theradiators should be installed above the return main topermit gravity flow of the condensate from the radiator,and the return main should pitch downward to the pumpreceiver.

Installation

Two-pipe vapor systems with condensate pumpsare basically alike in design. However, since twoinstallations are seldom alike, it is necessary to install

each system according to the mechanical blueprintsfurnished by the civil engineer and the instructions ofthe manufacturer of the equipment.

Operation

The two-pipe vapor steam distribution system canbe operated at the pressure limit of the steam plantboiler, provided the condensate pump is designed forsufficient discharge head necessary to overcomedischarge pipe friction loss, boiler pressure, and thehydrostatic head between the pump outlet and thewaterline of the boiler. The ends of the steam mains aredrained and vented into the dry return main through acombination float and thermostatic trap.

The two-pipe system with a condensate pump isadapted to relatively large installations and is probablythe most practical and trouble-free system. Most vaporsystems differ somewhat with each installation. Forspecific instructions for the correct operatingprocedures, you should refer to the manufacturer’sinstructions for the specific type of equipment installed.

Maintenance

Most of the two-pipe vapor steam distributionsystems differ from one system to another. Therefore,you will encounter different maintenance problemswith each system. It is not feasible to try and cover all ofthe problems you might encounter with differentsystems of this type. However, the more common onesare discussed.

Figure 3-7.—A two-pipe vapor system with a condensate pump.

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When you find that the individual radiator fails toheat, either an inoperative steam trap or a radiator that isnot installed correctly can cause the trouble. Repairingor replacing the steam trap or correcting the improperinstallation of the radiator can eliminate these troubles.

When it is the whole distribution system that fails toheat, clogged or closed receiver vents can cause thetrouble, a flooded return line, the lack of pump capacity,or air binding the system. These troubles can beremedied by opening the vents, checking and adjustingthe pump cut-in, replacing the pump, or repairinginoperative rerun traps.

One common trouble that occurs in this type ofdistribution system is the overflow of water from thereceiver vent. An inoperative pump usually causes thiscondition. The pump may be causing the floodingbecause of its inadequate capacity or because it isunable to handle the volume of condensate required.This condition can be corrected by either repairing orreplacing the pump.

Another cause of overflow of water from thereceiver vents is an obstruction in the line between thecondensate receiver and the boiler. The trouble can beremedied by eliminating the obstruction, regardless ofwhether it is a closed valve or a clogged line.

TWO-PIPE VAPOR SYSTEM WITH AVACUUM PUMP AND A CONDENSATERETURN

The two-pipe vapor distribution system with avacuum pump and a condensate return, as shown in

figure 3-8, is similar to the two-pipe vapor system with acondensate pump. The piping in this system includesseparate steam and return mains.

Installation

Most vapor distribution systems with vacuumpumps and condensate returns are similar. However, itis seldom that two steam distribution installations arealike in detail. When installing vapor-heatingdistribution systems, it is advisable to refer to themanufacturer's recommendations, civil engineermechanical drawings, and specifications for the properinstallation procedures.

Operation

When this type of distribution system is operated,the steam is supplied at the top of the radiator and the airand condensate discharged through a thermostatic trapfrom the bottom of the opposite end of the boiler. Allreturns are dry and terminate at the vacuum pump. Thevacuum pump is usually a motor-driven unit, althoughlow-pressure steam turbines have been successfullyused to a limited extent. The vacuum pump returns thecondensate to the boiler and maintains the vacuum orsubatmospheric pressure in the return system. Themaintenance of a vacuum in the return system (3 to 10inches of water) enables almost instantaneous filling ofthe heating units at low steam pressure (0 to 2 psi) sinceair removal is not dependent upon steam pressure.

The vacuum pump withdraws the air and waterfrom the system, separates the air from the water, expelsthe air to the atmosphere, and pumps the water to the

Figure 3-8.—A two-pipe vapor system with a vacuum pump.

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boiler, feedwater heater, or surge tank. Usually, thevacuum pump is supplied with a float switch as well as avacuum switch, and it can be operated as a condensatepump unit. The float switch should be used only whenthe vacuum switch is defective, and then only until thedefects can be repaired or corrected.

This system can be used in all types of buildings,and it is of particular advantage for the satisfactoryoperation of indirect radiation units, heating coils, andventilating units, and for other units that requires closeautomatic control. Indirect radiation is a term applied towarm-air heating systems that receive their heat fromsteam supplied to their heat exchanger coils.

Maintenance

When considering the subject of maintenance on atwo-pipe vapor distribution system having a vacuumpump, you will find that most of the troubles that havepreviously been discussed also apply to this system. Inthis distribution system, however, keeping air fromleaking into the system is more of a problem than in theother distribution systems. Excessive air leakage oftencauses the pump to run all the time, or the leakage cancause the system to fail to heat altogether. To eliminate-air leakage, you must find the point where air is leakingand repair it, so air cannot get into the system. Rustyspots and water seepage usually indicate the points atwhich air is leaking into the system.

Q4.

Q5.

Q6.

Q7.

On a gravity, one-pipe, air vent system, thereturn of condensate to the boiler depends onwhat factor?

Air in a one-pipe system has what adverseeffects?

What is the major difference between a two-pipesystem with a return trap and a two-pipe systemwith a condensate pump?

What is the function of the vacuum pump on atwo-pipe vapor system?

STEAM DISTRIBUTION SYSTEMCOMPONENTS

Learning Objective: Recognize different systemcomponents and understand their basic operation,application, and maintenance.

In previous sections of this chapter, you readabout various components as you studied the variousdistribution systems. The components were only

mentioned, however, and not explained in detail.Therefore, in this section, we are going to discussthese components, their purpose, operation, andmaintenance.

RADIATORS

Steam radiators. are normally classified into twocategories. One is the fin-tube radiator, which consistsof a metal tube that has metal fins attached on theoutside to increase its total heating surface. It generallyhas a valve at one end and a trap at the other end. Thisradiator has been used more extensively in the past 15years. It is readily adaptable to areas where floor spaceis limited, since the radiator is normally mounted on thewalls. The second category is the cast-iron radiator,which is made in sections. A typical cast-iron radiator isshown in figure 3-9. These radiators are similar to thoseused in hot-water heating systems. The cast-ironradiator is generally used in the one-pipe distributionsystem. In this system, there is only one distributionpipe connected to the radiator. This pipe delivers steamto the radiators, and it also returns water from thecondensed steam to the boiler. For this reason, theradiators must be tilted slightly toward the distribution

pipe.

The radiators in a two-pipe steam distribution

condenses into water.prevents steam from leaving the radiator until it

system are connected to the boiler by means of adistribution pipe as well as by a condensate return pipe.Since the steam and condensate in this system flow inseparate pipes, the pipes are smaller than those requiredfor the same size radiator in a one-pipe system. Theradiator outlet is usually equipped with a steam trap that

Figure 3-9.—A typical cast-iron radiator.

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Figure 3-10.—A typical automatic air vent.

prevents the proper heating of the radiator or othersteam equipment. Also, steam that is permitted to blowthrough a defective trap results in heat loss.

Types of Traps

Traps are generally classified according to theiroperation. The most common types of traps are float,bucket thermostatic, float thermostatic, impulse,thermodynamic, throttling, and bimetallic element.

FLOAT TRAP.—The float trap normally consistsof a body, float, linkage, seat, and valve. A typical floattrap is shown in figure 3-11. As water enters the trap, thefloat rises, opens the valve, and allows the accumulationof water to flow into the return lines that take it to theboiler. When the water has run out, the float falls, closesthe valve, and traps the steam.

RADIATOR AIR VENTSThe maintenance to be done on a float trap is of a

simple nature. One of the most common difficulties isthat of the float getting water in it and not rising. In thiscase, the float must be replaced. The valve sometimesgets plugged or worn and has to be cleaned or replaced.

There are two types of radiator air vents: automaticand manually operated. A typical automatic air vent isshown in figure 3-10. Air vents are installed to removeair from the radiators, because air keeps the radiatorfrom heating properly.

The type of air vent shown consists of a hermeti-cally sealed bellows, a valve disk and seal, and a ventbody. The bellows contains a volatile liquid with aboiling point 10°F or lower than that of water. So, whenthis liquid is heated to a temperature 10oF below thesteam and water temperature, the liquid volatilizes,expands, and closes the valve. When air surrounds thebellows, the air is cooler than the steam. This causes thebellows to contract, to open the valve, and to allow theair to escape. This cycle then starts over again.

The type that is operated manually is usually a smallvalve that has a slotted screw incorporated in the stemand a little spout on one side for the discharged air.These manual vents are normally installed in the sameplace in the distribution system as automatic vents.

STEAM TRAPS

Steam traps are designed to retain the steam in aradiator or other using device until it changes intocondensate. After the steam has turned into condensate,the trap releases the water so it can enter the return lines.However, it keeps the steam coming into the radiatorfrom escaping. The trap performs an importantfunction, since the excessive accumulation of water

BALL-FLOAT TRAP.—In a ball-float trap, thevalve of the trap is connected to the float so the valveopens when the float rises. When the trap is in operation,the steam and water that may be mixed with it flow intothe float chamber. As the water level rises, the float islifted, thereby lifting the valve plug and opening thevalve.

The condensate drains out and the float movesdown to a lower position, closes the valve. Thecondensate that passes out of the trap is returned to thefeed system.

Figure 3-11.—A typical float trap.

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Figure 3-12.—An inverted bucket trap.

BUCKET TRAP.—There are two types of bucket

traps: the upright and the inverted. An example of the

inverted bucket trap is shown in figure 3-12.

During operation of the upright bucket trap, thesteam and water both enter the trap body. As the waterenters, it causes the bucket to float and the valve toclose. The water continues to rise; it overflows into thebucket that sinks. When the bucket sinks, the trap valveis opened and the steam pressure forces the water out.When all of the water is expelled from the bucket, thebucket again floats, the valve closes, and the cycle startsagain.

During the operation of the inverted bucket trap, thesteam and water both enter under the bucket. The steammakes the bucket buoyant, causes it to rise, and closesthe valve. When the steam condenses, the bucket drops,opens the valve, and the steam blows the water out of thetrap.

Maintenance on bucket traps consists mainly ofcleaning and inspecting them periodically. If the trapbegins to leak steam, replace the valve disk and seat.However, if the bucket fails to open the valve, the trapusually becomes waterlogged. When a valve disk orseat becomes damaged, the trap allows steam to leakthrough. The condensate return line becomesexcessively hot when the trap is leaking steam. Buckettraps contain some water at all times. Therefore, theymust be drained when the system is to be off duringfreezing weather.

Figure 3-13.—A typical thermostatic trap.

THERMOSTATIC TRAP.—The thermostatictrap is often used on radiators and is commonly knownas a radiator trap. It has a bellows that contains volatilefluid that expands and vaporizes when heated. Pressurebuilds up inside the bellows and causes it to lengthenand close the valve. A typical thermostatic trap is shownin figure 3-13.

When water collects around and cools the bellows,the bellows contracts. This action opens the valve andpermits water to escape. As the water goes out, thesteam that enters contacts the bellows and causes it toexpand, closing the valve and preventing the steamfrom escaping.

The most common trouble with the thermostatictrap is that the bellows develops holes. So, the bellowsdoes not work and has to be replaced. The bellows andlower valve seat can be removed for repair withoutdisconnecting any of the piping.

FLOAT THERMOSTATIC TRAP.—The floatthermostatic trap operates on the principle of the floattrap and the thermostatic trap. Practically the samemaintenance is required. A typical example of the floatthermostatic trap is shown in figure 3-14. Thethermostatic bellows acts as an air eliminator.

IMPULSE TRAP.—The operation of the- impulsetrap (fig. 3-15) is based on the principle that a portion ofhot water, under pressure, flashes into steam when itspressure is reduced. The trap is operated by a movingvalve impelled by changes of pressure in a controlchamber. The valve has tiny orifices drilled through itscenter that allow the continuous bypassing ofcondensate from the inlet of the trap to the controlchamber. This bypassing reduces the chamber pressurebelow the inlet pressure, so the valve opens and allows

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Figure 3-14.—A float thermostatic trap.

Figure 3-15.—An impulse trap.

free discharge of the condensate. The temperature of theremaining condensate rises and flashes back to steam.The flow through the valve orifice is choked andpressure builds up in the control chamber, closing thevalve.

About 5 percent of the rated capacity of the trapflows through the valve orifice. The pressure on thedischarge side of the trap should not be over 25 percentof the inlet pressure if the trap is to function properly.Very little maintenance, except some periodic cleaning,

is required for the impulse trap. The trap may bedisassembled for cleaning or repairing withoutdisturbing any of the piping.

THERMODYNAMIC TRAP.—A typical ther-modynamic trap is shown in figure 3-16. It containsonly one moving part—a disk. This disk is operated bychanges in steam pressure. Pressure under the diskraises it to allow the condensate to be discharged.Droplets of condensate form on top of the disk. Thensteam enters at high velocity and creates a low pressureunder the disk; the droplets of water above the disk thenflash into steam and create a high pressure above thedisk. (You recall that water expands to as much as 1,728times its volume when it changes to steam.) The highpressure against the top of the disk overcomes the lowerpressure of the incoming steam, so the trap closes. Asmore condensate collects in the trap, the steam abovethe disk condenses and relieves the high pressure andthe cycle is repeated.

The most common trouble is that the trap becomesplugged and has to be disassembled and cleaned. Thethermodynamic trap can be cleaned or repaired withoutdisturbing any of the piping. Very little other

Figure 3-16.—A thermodynamic steam trap.

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maintenance is required for this trap because of itssimple construction. Too, the trap is usually constructedof stainless steel.

THROTTLING TRAP.—The operation of thethrottling trap (fig. 3-17) is based on the principle thatthe flow of water through an orifice decreases as itstemperature approaches that of the steam used. The rateof flow of the condensate may be adjusted by raising orlowering a stem (needle valve) that fits into a taperedseat. This throttling trap has no moving parts.

Condensate that is slightly cooler than steam entersthe trap, travels up through a baffle arrangement, and isdischarged through an orifice. If the condensatedischarge rate is higher than the inlet rate, the water(condensate) level in the chamber drops. This allowssteam to enter the baffle passage and heat thecondensate. The amount of water flashing into steamincreases; so the volume of steam-water mixture Pointers on Operating Procedureshandled by the orifice increases and thereby reduces thecapacity of the orifice. The reduced flow through theorifice permits the level of condensate in the chamber torise until the heater water in the baffle passage has beencompletely discharged and replaced with water that isslightly cooler. Then the cycle is repeated. Air is ventedfrom this trap through the same passage as thecondensate.

The throttling trap can be replaced withoutdisturbing any of the piping.

Figure 3-17.—A throttling trap.

BIMETALLIC-ELEMENT TRAP.—Thebimetallic-element trap, as shown in figure 3-18,contains bimetallic elements that bend when heated.The metals in the bimetallic strip generally are Emvarand copper. The copper expands rapidly when heated,but Emvar expands very little. Therefore, the bimetallicstrip bends when it is heated. This trap may be used forhigher or lower steam pressure by increasing ordecreasing the number of bimetallic leaves in the trap.

This trap works basically the same as thethermostatic trap. When steam enters the trap, theelement is heated and bends, thus closing the valve. Assteam condenses, the elements cool and straighten outto allow the valve to open and let the condensate escape.The bimetallic trap can be repaired without disturbingany of the piping.

To help ensure trouble-free service of steam traps,follow the proper operating procedures carefully. Someimportant factors involving operating procedures arefurnished below.

Steam traps should be operated within thecapacity rating and pressure differentials recommendedby the manufacturer. Use traps for the correct pressureand temperature. If operating pressures change, it maybe necessary to change trap sizes, or internal parts, to fitthe new pressure conditions.

Traps should be insulated where heat must beconserved. Some types of traps, which depend on thecooling effect of the condensate for operation, should beleft bare. Check the manufacturer’s instructionsregarding insulation.

Where continuity of service is a requirement, athree-valve bypass is usually provided to permitdrainage while the trap is being overhauled. Bypassesare also used to speed up the discharge of condensateand air when you are starting a system. In normaloperation, however, the bypass valve should be keptclosed to prevent steam from being wasted.

Check valves, located in the discharge line, areimportant in parallel installations to prevent thedischarge of one trap from backing up into that ofanother. Also, when condensate from the trap mustdischarge to a higher elevation, a check valve preventsbackflow of condensate.

Inverted bucket traps must be primed foroperation by providing a condensate seal in the bottom

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Figure 3-18.—A bimetallic-element steam trap.

of the trap. Prime the trap before starting operation byremoving the test plug on top of the trap and filling thetrap with water. If no test plug is available, the trap canbe primed by closing the discharge valve and openingthe steam supply valve slowly until the steam iscondensed and the trap is filled with condensate.

Blow down steam traps periodically to rid themof dirt and sediment. Blow down and clean strainers asrequired.

When overhauling traps, do not removethermostatic elements while hot. This practice mayresult in expansion beyond the stroke range of thebellows or diaphragm.

Periodically, open the air vents of float traps notprovided with thermostatic air vents to vent outaccumulated air.

Steam Trap Tests

Methods for testing traps without breaking theinstallation are stated below:

TEST VALVE METHOD.—Close the dischargevalve and open the test valve. Observe discharge

characteristics. Intermittent discharge, dribble, orsemicontinuous discharge indicates correct operation.A continuous steam blow indicates loss of prime,defective valve operation, or foreign matter embeddedin the valve seat. A continuous condensate flow mayindicate that the trap is too small, the amount ofcondensate abnormally high, or a pressure differentialthat is too low.

GLOVE TEST METHOD.—Grab inlet and out-let pipes simultaneously, using a canvas glove on eachhand for protection. A slight temperature differenceindicates that no condensate is passing.

PYROMETER TEST METHOD.—This methodis more accurate than the previous one, as it uses asurface contact pyrometer to check inlet- and outlettemperatures. File a clean spot on both pipes beforetaking readings.

PYROMETRIC CRAYON TEST METHOD.—Temperature-indicating crayons can be used when nopyrometer is available. Select crayons of propertemperature ratings and mark the required pipe spots.When the crayon marks melt, the temperature of the testspots corresponds to those of the crayon ratings.

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EAR TEST METHOD.—Hold one end of a metalrod to the trap body and place the other end in the ear, oruse an engineer's stethoscope. If the trap is operatingproperly, you will hear the regular opening and closingof the valve. If operation is defective, you will hearconsiderable rattling or the continuous flow of steam.

PROTECTION AGAINST FREEZING.—Pro-tect traps from freezing in cold weather. If the steam isshut off during freezing weather, drain the traps andpiping of all condensate. Make certain insulation is ingood condition. The inverted bucket is especially proneto freezing because, in normal operation, it is half filledwith water.

WATER TANKSFigure 3-19.—A typical unit heater installation.

A boiler plant and heating system cannot beoperated so the flow of water and the flow of steam arealways in balance. The demand for water by the boilermay exceed the rate at which water is being returnedfrom the heating system, or the water may be returningat a rate that is greater than the requirements of theboiler. One or more tanks can be installed tocompensate for uneven flows and for differencesbetween the demand and supply of water. These vesselsare called surge tanks.

Sudden reductions in pressure may lead to violentsteam formation. Flash tanks help el iminatedisturbances in the piping system caused by thisprocess. These tanks are usually small and are locatednear the traps where the pressure release occurs.

Unit steam heaters are convection heaters in whichthe air is circulated by means of a fan. The unit heater issimilar to an automobile radiator. It is enclosed in asheet metal case with the fan mounted at the rear. Atypical unit heater is shown in figure 3-19. The steamenters the unit at the top and the heat is transferred to thefins of the heater. The fan blows the air over the fins andout into the space to be heated. When the steamcondenses, the steam trap, usually a float thermostatictype, allows the condensate to drain into the condensatereturn line. A strainer is installed just ahead of the trap tohelp keep foreign matter out of the trap.

Unit heaters are usually suspended from theceilings of shops, offices, dining halls, and warehouses.This type of installation saves on floor space, providesfor rapid heating, and gives wide distribution of heat.

Unit heaters should be taken down periodically andcleaned, because dust and lint collect between the finsand reduce the flow of air.

WATER HEATERS

Steam-operated water heaters are used to supply hotwater for laundries, dining halls, latrines, and otherfacilities. There are two general types of these heaters:storage and instantaneous.

Storage Type

The storage type of water heater is used to providepotable (drinking) water. The steam-operated storagetype of water heater consists of a steel tank that containsa steam-heating coil like that shown in figure 3-20. Thehot-water tank is connected to the base water supplysystem and remains full of water at all times.

The steam is circulated through the heating coil or"bundle," as it is sometimes called. The heat from thesteam is transferred through the walls of the coil to thewater in the tank. Because of the difference in weightbetween hot and cold water, the hot water rises and thecold water goes to the bottom of the tank where the

Figure 3-20.—The storage-type water heater.

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steam-heating coil is located. Here the water is heatedand begins to circulate. Eventually, all of the water inthe tank becomes heated. When hot water is drawn,more cold water enters the tank and this heating processrepeats itself. This action maintains a full tank of hotwater for use whenever hot water is needed. Accordingto safety regulations, the hot water should not exceed180°F. The storage type of water heater may beconstructed to be installed in either the horizontal or thevertical position.

Tappings are usually provided in the tank for athe rmomete r—a the rmos ta t i c e l ement fo r atemperature-regulating valve (which will be discussedlater in this chapter) and a safety valve. The tube coilshould be inspected annually to make sure steam is notleaking into the water. The chemicals that aresometimes used in the steam may make the people whouse the water sick if they drink it.

Instantaneous Type

Instantaneous heaters are used primarily as boilerfeedwater heaters; however, they are sometimes used toprovide potable (drinking) water at some installations.The operation of the instantaneous-type heater isbasically the same as the storage-type heater; theirconstruction, however, is quite different. The diameterof the instantaneous heater is small in comparison to thestorage-type heater. The outer shell of the instantaneousheater is small in comparison to the storage-type heater.The outer shell of the instantaneous heater barely coversthe tube coil, as you can see in figure 3-21. In somemakes, the water is circulated through the coil, and thesteam is released in the shell and surrounds the coil. Atemperature-regulating valve controls the watertemperature for both types of heaters.

TEMPERATURE REGULATORS

The temperature regulator is used to regulate thequantity of steam necessary to maintain the hot water at

Figure 3-21.—The instantaneous-type water heater.

the desired temperature. The unit consists of atemperature bulb, copper line, diaphragm, spring andtemperature adjustment, and steam valve. A typicaltemperature-regulating valve is shown in figure 3-22.

The bulb and copper tube are called the capsule andcapillary tube. They contain a gas that expands orcontracts with a change in temperature. The capillarytube is connected to the top of the temperature regulatorwhich contains a diaphragm (bellows). The diaphragm(bellows) is connected to the valve stem. A spring holdsthe valve open at low temperatures. When thetemperature rises in the water tank, the gas in thetemperature bulb expands and forces the diaphragmdown, closing the steam valve. Adjusting the tension ofthe spring can control the water temperature. A steamtrap in the steam-heating system returns the condensedsteam to the condensate tank.

The hot-water tank accessories consist of atemperature gauge that has a range of 40°F to 210°F anda safety valve or pressure relief valve. The relief valve isset at a pressure that is 10 pounds higher than theoperating pressure, and both the setting and the valvemust comply with current ASME code specifications.

CONDENSATE RETURN PUMP

Condensate return pumps cause the water that hascondensed from the steam in radiators, heating coils,convectors, and unit heaters to circulate back to theboiler. One type of condensation return pump is shown

Figure 3-22.—A typical temperature-regulating valve.

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in figure 3-23. Units of this type normally consist of areceiver or condensate tank and pump independentlycontrolled by float switches. A check valve and a venton the receiver allow the receiver to fill and empty as theneed arises.

Condensate return pumps are maintained asprescribed by the manufacturer of the unit. Usually, themotor should be oiled, the check valves and ventscleaned, the float switches adjusted, the pump repacked,and the tank cleaned at least once each year.

EXPANSION JOINTS

Expansion joints and expansion loops in longheating lines are convenient devices for handling thepipe elongation caused by expansion. The five majortypes of expansion joints are as follows: slip joint,bellows joint, swing joint, expansion loop, and balljoint.

The slip joint is shown in figure 3-24. The femalepart of the joint is placed over the male part and the jointis held tight by the packing that permits expansion. Thekind of packing used determines the temperature towhich the joint can be subjected.

The bellows joint, as shown in figure 3-25, has ametal bellows that flexes as expansion occurs. The joint

Figure 3-23.—A typical condensate return pump.

Figure 3-24.—-A typical slip-type expansion joint.

cons ists of a thin-walled corrugated copper stainlesssteel tube clamped between flanges. Rings help to keep

Figure 3-25.—A typical bellows-type expansion joint.

the corrugations under relatively high pressure. Thesteam pipe and joint should be supported and guided tokeep misalignment to a minimum.

The swing, or swivel, joint is most often used toallow expansion to occur naturally in a system that hasscrewed joints. When it is used with welded elbows, theswing joint introduces torsional strains in the elbowsand in the swing piece.

The expansion loop absorbs expansion through theformation of U- or Z-loops in the pipeline.

The ball joint is often used instead of the expansionloop, because it requires less space and material. A balljoint consists of four basic parts. The joint has a casingor body to hold the gaskets and a ball. The ball is ahollow fitting shaped externally like a ball at one end(inside the casing) and is threaded, flanged, or adaptedfor welding to the pipe at the other end. There are twogaskets that hold the ball and provide the seat. There isalso a retaining nut or flange that holds the ball andgaskets in the casing. The end of the two pipes beingcoupled is connected to the joint casing; the end of theother pipe is connected to the ball. In operation, the balljoint allows the movement of the pipe with 30° to 40° offlexibility, plus a rotating or swivel motion of 360°.

The slip-type joint must be kept properly aligned,adequately packed, within the proper limit of travel, andthoroughly cleaned and lubricated. You should adjustor replace the packing, as required, to prevent leaks and

3-16

assure a free-working joint. It is necessary to lubricateevery 6 months with the proper grease for this type ofjoint and the service conditions. Once a year, you shouldcheck the flange-to-flange distance of the slip joints.You should check the flanges first when they are coldand next when they are hot. Measuring makes sure thatthe travel is within the limits shown in the manu-facturer’s data. A change in slip travel usually indicatesa shift in anchorage of a pipe guide, so you must locateand correct the difficulty. You should also inspectannually for signs of erosion, corrosion, wear, deposits,and binding. Then you should repair or replace thedefective parts, as required.

The bellows-type joint is checked annually formisalignment, metal fatigue, corrosion, and erosion.You should note the amount of travel between cold andhot conditions. If the joint fails, you should replace thebellows section of the joint.

Expansion loops require little specific maintenanceexcept inspection for alignment and leaks.

The ball joint must be kept adequately packed. Youshould adjust or replace the gaskets, as required, tocorrect leaks and obtain a free-working joint. Youshould always refer to the manufacturer’s instructionsfor doing maintenance work.

The swing joint requires only the normal

maintenance required for pipe fittings.

Q8.

Q9.

Q10.

Q11.

Q12.

Q13.

Q14.

Q15.

Q16.

Q17.

What are the two categories of radiators?

The bellows of an automatic air vent contains aliquid with a boilingpoint of what temperature?

What are the two types of bucket steam traps?

What is the most common trouble with athermostatic steam trap?

The bimetallic strip in a bimetallic-element trapis made of what materials?

Which steam trap test method uses a crayon?

What are the two general types of steam-operated water heaters?

What device controls the quantity of steamrequired for both types of water heaters?

What are the five major types of expansionjoints?

A bellows type expansion joint is inspected formisalignment, metal fatigue, corrosion, anderosion how often?

3-17

CHAPTER 4

HEATING SYSTEMS

Learning Objective: Identify the principles and theory of heating and theprocedures required for installing, operating, maintaining, troubleshooting, andrepairing warm-air heating and hot-water heating systems and associated peripheralequipment.

Heat is one of the prime necessities of life. It is asessential as food, clothing, and shelter. You can have avery good shelter, but you still need heat to becomfortable in it. By studying this chapter, you will startto gain knowledge of what you will be required to knowto become efficient in the Utilitiesman (UT) field.

PRINCIPLES OF HEATING

Learning Objective: Understand the basic principlesand theory of heat, heat measurement, and heat transfer.

Long after people had advanced to the stage ofhouse building, heating methods had not improvedmuch. For centuries fires for heating and lighting werecontained in braziers or confined to an unused cornerof a room. The smoke was supposed to escape througha hole left in the roof of the building duringconstruction. Of course, a considerable amount of rainand snow entered the room during bad weather. Duringthe twelfth century, however, the people in thenorthern part of Europe started using crude fireplacesand flues to replace the brazier and hole-in-the-roofmethod of heating. Some of these rudimentary heatingsystems still exist in France.

In the thirteenth and fourteenth centuries, the round,hollow stone chimneys began to be used. At the end ofthe fourteenth century, people were using a number offireplaces in their homes and grouping the chimneystogether in a vertical, rectangular mass of masonry withdecorative effect. By the end of the Italian renaissanceperiod, chimneys were in common use.

During colonial days in America, the fireplacechimneys were a large masonry mass projectedthrough the center of the roof or were an importantfeature of the gable end walls. This general trend isoften followed in architecture today because centralheating, required in places where fires are required 5 or6 months of the year, makes the chimney an important

feature of a heating plant. There are heatinginstallations, however, that do not make use of themasonry ch imney and have subs t i tu t ed aninconspicuous metal smoke pipe. Other types ofheating, such as electrical heating, require no chimney.Methods and equipment used for heating the places welive and work have progressed quickly in the last 100years. This quick advance is due to our understandingof the principles and theory of heat, which in earliertimes was not yet understood.

THEORY OF HEAT

Heat is a form of energy that is known for its effect.Heat can be produced or generated by the combustionof fuels, by friction, by chemical action, and by theresistance offered to the flow of electricity in a circuit.However, the particular form of generated heat withwhich the heating specialist will be dealing is producedby combustion. Generated heat is obtained by burningcommon types of fuels, such as coal, oil, and gas.

MEASUREMENT

To operate a heating plant efficiently, you must befamiliar with the measurement of heat and how thisheat is transferred from the plant to the space beingheated. The first part of this section is devoted tomeasuring temperature; the second part is concernedwith the transfer of heat from the plant to the spacebeing heated.

Measurements of temperature and pressure, whichare obtained continuously, are very important factorsin the operation of a heating plant. The degree ofcorrectness of these measurements directly affects thesafety, the efficiency, and the reliability of theoperation of the heating plant. Although heat andtemperature have a direct relationship, there is also adistinction between them. For example, a burningmatch develops a much higher temperature than asteam radiator, but the match does not give off enough

4-1

heat to warm a room. Another example tells us that IOpounds of water at 80°F will melt more ice in a givenlength of time than 1 pound of water at 100oF. Theformer has more heat, but the latter has a highertemperature. Temperature is the measurement of heatintensity in degrees Fahrenheit or Celsius. Therefore,temperature measurements can be made by using aglass thermometer calibrated either in degreesFahrenheit or Celsius. The generally accepted way ofs t a t i n g m e a s u r e m e n t s o f t e m p e r a t u r e i nEnglish-speaking countries is in degrees Fahrenheit.

The thermometer measures the degree of sensibleheat of different bodies. The thermometer can make acomparison only between the temperature of a bodyand some definitely known temperature such as themelting point of ice or the boiling point of water.Figure 4-1 shows a comparison of the scales ofFahrenheit and Celsius thermometers. It also showsthe marking of the freezing and boiling points of purewater at sea level. The range of the Fahrenheitthermometer between the freezing point and theboiling point is 180° (32° to 212° = 180°). On theCelsius thermometer, the range is 100° (0° to 100° =100°) from the freezing point to the boiling point.

Figure 4-1.—Comparison of Fahrenheit and Celsius

thermometers.

To convert Fahrenheit readings to Celsius:

(°F - 32°) ÷ 1.8 = °C

To convert Celsius readings to Fahrenheit:

(°C x 1.8) + 32° = °F

The heat that can be measured by a thermometerand sensed or felt is referred to as "sensible heat." Anexample of sensible heat is presented by placing asmall vessel of cold water over a gas flame and puttinga thermometer in the water. Upon observation, younote that the thermometer indicates a rise intemperature. Also, if you place your finger in the waterseveral times, you will feel (or sense) the change intemperature that has taken place.

The unit of measurement for a given quantity ofheat is the British thermal unit, abbreviated andcommonly known as Btu. One Btu is the amount ofheat needed to change the temperature of 1 pound ofwater 1° Fahrenheit at sea level. If one Btu is added to1 pound at 50°F, the temperature of that pound of waterwill be raised to 51°F.

All substances above absolute zero contain heat.There is heat even in ice, and its melting point is fixedat 32°F. Because of a fundamental law of nature, whenice at 32°F melts into water at 32°F, a change of statetakes place. The ice (solid) has turned into water(liquid). A certain amount of heat is required duringthis change of state. This heat is known as latent heat.Latent heat is the amount of heat required to change thestate of a substance without a measurable change intemperature.

There are other types of heat that you willencounter in heating. These are as follows:

Specific heat–The ratio between the quantity ofheat required to raise 1 pound of any substance1oF and the amount of heat required to raise thetemperature of 1 pound of water 1oF.

Superheat–The amount of heat added to asubstance above its boiling point.

Total heat–Is the sum of sensible heat plus latentheat.

We previously mentioned absolute zero. But, whatis absolute zero? Scientists have determined that whenthe temperature of a substance has been reducedto -460°F that all the heat has been removed from asubstance. At this point all the molecules cease to havemotion. Absolute zero is the lowest temperatureobtainable. Heat is present in all substances when thetemperature is above absolute zero.

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HEAT TRANSFER

The transfer of heat is the next problem to considerafter the heat has been produced. It must be moved to thespace where it is to be used. Heat always flows from awarmer to a cooler substance; consequently, there mustbe a temperature difference before heat can flow.Naturally, the greater the temperature difference, thefaster the heat flow. Two objects that have differenttemperatures, when placed together, tend to equalizetheir temperature. Heat travels in heating systems fromone place to another by three different methods. Allthree of these methods are used in most heating systems.They are discussed in the paragraphs that follow

Conduction

Conduction is the flow of heat from one part of asubstance to another part of the same substance or fromone substance to another when they are in directcontact.

When one end of a stove poker is held in a flame,the other end will soon be too hot to hold. Thisindicates that the heat is being conducted, ortransferred, from one end of the poker to the other end.Such a transfer of heat is called conduction.Conduction is used to transfer heat through the walls ofa stove, furnace, or radiator so that the warmth can beused for heating. Some materials do not conduct heatas well as others. For example, if a piece of wood hadbeen used instead of the poker, the end of the woodaway from the fire would have remained cool. Thosematerials that offer considerable resistance to heatflow are referred to as insulators or poor conductors.

Convection

Convection is the transfer of heat by means ofmediums, such as water, air, and steam. When air isheated, it expands, becomes lighter in weight, andrises. The cooler air, which is heavier, then flows in toreplace the warm air. Thus a convection current is setup. Water, when heated, acts in the same way as air.The water next to the heating surface becomes warmer,lighter, and rises. This action allows the cooler water toflow in next to the heating surface and become heated.Convection is a very important factor in a heatingsystem. It is this force, developed by heating themedium, which circulates that medium to the space tobe heated.

Radiation

Radiation is the transfer of heat through space.When a hand is held in front of a stove, it is quickly

warmed by means of radiation. In this same manner,the earth receives its heat from the sun.

Radiated heat is transferred by heat waves, similarto radio waves. Heat waves do not warm the air throughwhich they pass, but they must be absorbed by somesubstance to produce heat. For example, when youstand in the shade of a tree, you feel cool because theleaves and limbs are absorbing the heat waves beforethey reach you.

When heat waves strike an object, some arereflected, some may pass through, and the objectabsorbs the rest. Polished metals are the best reflectorsknown; therefore, they are a poor absorber of heat. Apoor absorber is also a good radiator. Rough metalabsorbs heat more readily than a highly polished metal,and it also loses heat faster by radiation.

The color of a substance also affects its absorbingpower. A black surface absorbs heat faster than a whiteone. That is why light-colored clothes are cooler insummer than are dark-colored clothes.

Q1. Heat can be produced or generated by whatmethods?

Q2. What two types of measurements directly affectthe safety, efficiency, and reliability of heat plantoperations?

Q3. Temperature is the measurement of what?

Q4. Convert 82 degrees Fahrenheit to degreesCelsius.

Q5. Heat travels in heating systems by what threemethods?

COMBUSTIBLE FUELS

Learning Objective: Understand the types andcharacteristics of combustible gases and fuel oils usedin heating systems.

If electricity and coal are disregarded, the fuelsmost commonly used with heating equipment areeither gas or petroleum. Next, we will take a brief lookat the types and characteristics of combustible gasesand fuel oils used for heating.

TYPES OF GASES

Gaseous fuels are usually classified according totheir source that, in turn, determines their chemicalcomposition. The heat valve (Btu per cubic foot) varieswith the types of gas and determines the quantity

4-3

required for a specific heating requirement. Thetypes principally in use are natural gas, manufacturedgas, and liquid petroleum gas (table G, appendix II).

Natural Gas

Natural gas is a mixture of combustible gases andusually small amounts of inert gases obtained fromgeologic formations. While the composition of naturalgas varies with the source, methane (CH4) is alwaysthe major constituent. Most natural gases also containsome ethane (C2H6) along with small amounts ofnitrogen and carbon dioxide (CO2). Natural gas iscolorless and odorless in its natural form; however; adistinctive odor is usually added as a safety factor fordetecting leaks. Natural gas mixes readily andcompletely with combustion air and thus issubstantially free from ash and practically smokeless.T h e s e c h a r a c t e r i s t i c s c o n t r i b u t e t o g o o denvironmental pollution control. From a standpoint oftrouble-free performance, ease of handling, andcontrol, natural gas offers many advantages that makeit the most desirable of all heating fuels.

Manufactured Gas

The common manufactured gases are carburetedwater gas, oil gas, and producer gas. These gases areroughly one-half hydrogen and one-third methane,plus small amounts of carbon dioxide, nitrogen, andoxygen. They are made by converting low-gradeliquid or solid fuels to the gaseous form by destructivedistillation (cracking) of oil or coal, by thesteam-carbon reaction, or by a combination of bothprocesses. These gases are ordinarily used at or nearthe production point because of high manufacturingcosts rule out the added expense of distribution.

Liquefied Petroleum Gas

Liquefied petroleum gases are hydrocarbon gasesnormally obtained as a by-product of oil refineries orby stripping natural gas. These compounds arenormally gaseous under atmospheric conditions;however, they can be liquefied by moderate pressure atnormal temperatures.

The principal LPG products are propane (C3H8)and butane (C4H10). Propane, the most common, isavailable by the bottle or cylinder and in bulk form. Itsboiling point is -44°F (note that this is very close to thatof refrigerant R-22).

Butane is generally available in bulk form. It boilsor vaporizes at 32°F. In other words, if the temperature

of butane is 32°F or lower, at atmospheric pressure, itremains a liquid, and heat must be applied to bring it tothe gaseous state. Note in table G, appendix II, the highheating. values of propane and butane.

Fuel Oils

Fuel oils are derived from crude oil, which consistsprimarily of compounds of hydrogen and carbon

(hydrocarbons), and smaller amounts of oxygen,nitrogen, and depending on the source, sulfur.Practically all fuel oil is either a product or aby-product of refining crude oil by the fractionaldistillation process or by cracking.

The Bureau of Standards, United StatesDepartment of Commerce, standardizes commerciallyused fuel oils. The oils are numbered in grades 1, 2, 4,5, and 6 and are titled commercial standard grades(CSG). These grades are identified in the Navy bymilitary specifications and are intended for use inoil-burning equipment for the generation of heat infurnaces for heating buildings, for the generation ofsteam, and for other purposes. A more in-depthdiscussion of fuels and their characteristics iscon ta ined in Fundamenta l s o f Pe t ro leum,NAVEDTRA 10883. A comparison of fuel oils bygrade is given in table H, appendix II.

Q6. What are the principal types of gases used inheating?

Q7. Fuel oils consist primarily of what compounds?

WARM-AIR HEATING EQUIPMENT

Learning Objective: Identify the different types ofwarm-air heating units and equipment and basicinstallation and maintenance guidelines.

Advances in the field of warm-air heating havemade it one of the most popular and widespread formsof heating in use today. It has the advantage ofadaptability with various fuels and can be used in avariety of buildings, including barracks, hangars,personnel housing, schools, and theaters. It is likely,therefore, that at one time or another you will beresponsible for performing technical maintenance andrepair and installation of warm-air heating equipmentand systems.

The different types of heating equipment that willbe discussed include unit heaters, electric and gas- and

4-4

oil-fired space heaters, and gas-fired and oil-firedfurnaces.

UNIT HEATERS

In this manual the term unit heater is defined as aninstalled equipment item and a component of a systemconsisting of an extended finned heat transfer surface(coil) and a propeller or blower fan to create airflowthrough it. Unit heaters are indirect units that differfrom space heaters because they generate heatindirectly from a medium of steam or hot water pipedthrough a central distribution system. Space heatersare direct-fired units that generate heat directly by theuse of an electrical coil or by a combustible fuel.

Unit heaters can be used for many heatingrequirements, the major limiting factor being theavailability of a steam or hot-water system. They arecommonly used with heating systems in shops, offices,dining halls, and warehouses. There are three basictypes: (1) the suspended horizontal discharge, (2) thesuspended ve r t i ca l d i scha rge , and (3 ) thefloor-mounted or horizontal type of blower unit (fig.4-2).

The units are rated in Btu or equivalent directradiation heat output and cubic feet per minute airdischarge capacity at a given fan or motor speed. Theseratings are important in the application of unit heaters.

Figure 4-2.—Unit heaters: A. Suspended vertical discharge; B. Suspended horizontal disc harge.

4-5

Manufacturers furnish information regarding the areaeffectively heated by units to enable proper planningand location of the units. Generally, units under50,000 Btu per hour are designated to operate onlow-pressure steam or high-temperature hot water.

Space Heaters

Space heaters are used for heating rooms andsimilarly enclosed spaces, either in addition to, or inplace of, a central heating system. They are desirable asa means of providing heat to a small space because oftheir simplicity of construction, low initial cost, andreasonable fuel consumption. They may be placeddirectly in the space or at such a location where heat canbe delivered through a single register into the space.

Space heaters are sometimes classified by themanner in which they transfer heat to the space to beheated; for example, by radiation and/or convection.The terms direct-fired and indirect-fired are also usedto identify such heaters. In this manual, space heatersare identified as direct-fired units and by their heatsource or fuel. This discussion will include electric,gas-fired, coal-fired, and oil-fired units.

Electric Heaters and Installation

Space heaters with electrically powered heatingelements are used in spaces where it is desired toel iminate cold spots and maintain uniformtemperatures, where other fuels are useful as portableunits on the floor to overcome floor drafts, and as fixedunits mounted in, or to walls or ceilings. They aregenerally rated in kilowatts (kW). One kW (1,000watts) is equal to 3,415 Btu per hour.

Electric space heaters are available in two generaltypes—the radiant and natural convection type and theforced warm-air (fan) type. In the radiant and naturalconvection type, heat from electric elements rises andstrikes parabolic (bowl-shaped) reflectors. Thereflectors are highly polished curved metal surfaces,which deflect the heat outward into the place whereheat is desired (fig. 4-3). Some radiant heat units haveno deflectors but provide a combination of radiant andnatural convection heat, which rises from the coils intoa chamber open on the side where heat is required. Theelectric baseboard convection heater is an example ofthis type. The forced warm-air type uses a motorizedfan to circulate heat from the heating element outwardinto the space (fig. 4-4). The electric units are operatedmanually with an ON-OFF switch or automaticallywith a thermostat.

Figure 4-3.—Radiant electric space heater.

Figure 4-4.—Forced warm-air electric space heater.

In the selection and installation of electrical spaceheaters, safety must be assured. Units that are to beinstalled should bear the label of the Underwriter’sLaboratories (UL). They should also conform to thesafety standards outlined in space heating equipmentUL-573. All electrical work required for aninstallation should be done according to themanufacturer’s instructions and by a qualifiedelectrician.

Gas Heaters and Installation

Gas-fired space heaters are clean in operation; theyare easily operated and require no fuel handling. Theyare adaptable for use with natural gas, manufacturedgas, or liquefied petroleum gas. Their constructionfeatures are similar regardless of the type of gas used.Basically, there are two types—the vented and theunvented.

VENTED UNITS are enclosed metal cabinetswith either top and bottom or front and rear grilles for

4-6

warm-air circulation. The flame burns in a closed satisfactory than the unvented type because there iscombustion chamber, and the heater vent carries away less danger of carbon monoxide poisoning. A panelthe gases (fig. 4-5). The flow of heat is maintained by a unit is one type of vented unit (fig. 4-6). It may bemotor-driven fan and is controlled by vanes, fins, recessed or surface-mounted in either an interior orlouvers, or diffusers. This type of unit is more exterior wall with a vent properly insulated and run up

Figure 4-5.—Rear view of a vented gas-fired space heater.

Figure 4-6.—Gas-fired panel space heaters.

4-7

through the wall. This type of unit has the advantage ofrequiring less floor or ceiling space.

UNVENTED UNITS are usually the open-flametype where the gas burns in an open combustionchamber. These heaters should be used in awell-ventilated area. Ventilation ensures that the carbonmonoxide produced by the gas flame is removed.

Gas-fired space heaters and their connectionsmust be of the type approved by the American GasAssociation (AGA). They must also be installedaccording to AGA specifications. Installation factors,such as the type of gas, the capacity of the heater, andthe line pressure drops, must be known to ensureproper plumbing procedures with respect to the gasservice line. All newly installed piping should betested for gas leaks. These tests should comply withNAVFAC DM3.

On vented gas units, be careful to install theventing system properly to minimize the harmfuleffects of condensation and to ensure that thecombustion products are carried away. Duringoperat ion, the inner surface of the vent must be heatedabove the dew point of the combustion products. Thisprevents water from forming in the flue pipe. Ventsections must be installed with the male ends of theinner liner down to allow any condensation that formsto return. This is important since the burning of 1,000cubic feet of natural gas produces approximately 12gallons of water. For the same reason, horizontal fluepipes should have an upward pitch of at least 1-inch perrunning foot.

Vent pipes should be equipped with draftdiverters. A diverter is a type of inverted cone through

which the flue gases must pass on their way todischarge. It allows air from the heated room to bedrawn into the flue pipe joining the combustion-gases.This action prevents excessive downdrafts or updraftsthat are apt to extinguish the pilot light or possibly themain burner.

Oil-Fired Space Heaters

In areas where oil is the principal fuel, oil-firedspace heaters are used for many space heatingrequirements. Oil-fired space heaters are very simplein construction. They consist of a burner, a combustionchamber and outer casing, a fuel tank, and fuel controlvalve. An air space is provided between thecombustion chamber and the outer casing. Air entersthrough grilles in the bottom of the heater, is heated,and passes out through grilles in the top of the unit.Some oil-burning heaters are equipped with a blowerand electric motor to force the heated air out into theroom. They turn at slow speed and may be either directdrive or belt driven.

Oil-fired space heaters have atmosphericvaporizing-type burners. The burners require a lightgrade of fuel oil that vaporizes readily at lowtemperatures and leaves only small amounts of carbonand ash. Number 1 fuel oil is generally used. The twotypes of burners that will be discussed are the naturaldraft pot and the perforated sleeve.

N A T U R A L D R A F T P O T D I S T I L L A T EBURNERS are widely used for space heaters, roomheaters, and water heaters. A cutaway view of a naturaldraft pot type of burner is shown in figure 4-7. Inoperation, the distillate (oil) is fed at the bottom of theburner, either at the center or on the sides, and is

Figure 4-7.—Cutaway view of a natural draft pot type of burner.

4-8

vaporized at this point by radiant heat from above. The Installationvapors rise and mix with the air drawn through theperforated holes in the burner. During high fireconditions, the flame burns above the top combustionring, as shown in figure 4-8; and under low fireconditions, the flame burns in the lower portion or pilotring of the burner, as shown in figure 4-9.

The PERFORATED SLEEVE BURNER consistsof a metal base formed of two or more circular fuelvaporizing grooves and alternate air channels (fig.4-10). Several pairs of perforated sleeves or cylindersforce the air through the perforations into the oil vaporchamber. In this way a large number of jets of air areintroduced into the oil vapor, bringing about a goodmixture. This mixture burns with a blue flame and isclean and odorless.

These burners usually have a short kindling wick.Some burners have a cup below the base in whichalcohol is burned to provide heat for starting. The wickand alcohol are used only for lighting.

Figure 4-8.—High fire flame.

Oil-burning heaters are portable and are easilymoved from one location to another. For satisfactoryoperation, follow the installation procedures suppliedby the manufacturer. In both pot type and perforatedsleeve burners, oil is fed to the burner under control ofa float-operated metering valve (fig. 4-11). Set the unitlevel so the oil can be properly distributed in theburner.

Figure 4-10.—Perforated sleeve burner.

Figure 4-9.—Low fire flame. Figure 4-11.—Oil-controlled metering valve.

4-9

NOTE

The fuel level control valve is the onlysafety device on the oil-fired spaceheater.

When several space heaters are installed in abuilding, an oil supply from an OUTSIDE TANK to allof the heaters is often desirable. This eliminatesfrequent filling of individual tanks and reduces wastefrom spilling. Figure 4-12 shows the principalelements of such a system and important points toconsider during installation.

Be sure that the space heater is placed a safedistance from the wall. You also need a metal pan for itto sit in. This pan catches the oil if a leak occurs. Do notuse a sandbox or cement as both absorb oil and create afire hazard. In case of wood floors, place a piece offire-retardant material, such as Gypsum board(Sheetrock) on the floor underneath the metal pan. Itmay also be needed on the wall behind the heater if thewall is made of wood.

Since the flow of air to a vaporizing type of burneris induced by a chimney DRAFT, pay careful attentionto this feature. The draft produced by any chimneydepends upon the height of the chimney and thedifference in temperature between the flue gas andoutside air. The cross-sectional area required dependsupon the volume of flue gas to be carried. Sinceoutside air temperature varies during the heatingseason, arrange the chimney or flue to produce thenecessary draft under the most unfavorable conditionslikely to be encountered, usually an outside

temperature of 60°F. Above this temperature, heat isnot usually required, and below this temperature, draftwould be increased.

Install the draft REGULATOR to maintain aconstant draft adjustment for the rate at which theheaters are fired. The regulator is a swinging damper orgate with provision for adjustment. Since balance andfree action are the fundamentals on which its operationdepends, be sure the installation provides for thesefeatures. Install the damper section with the word top atthe true top position. Make sure the face is plumb. Whenthe damper regulator is installed in a horizontal run ofpipe, do not use a counterweight on the damper.

A DOWNDRAFT may seriously interfere withproper functioning of these burners. Downdraft mayresult when the chimney is not high enough above theroof line or is too close to other high buildings, trees, orterrain features. The chimney top must be at least 3 feetabove the highest point of the building roof. If thedifficulty is caused by other factors, a downdraft hoodmay prove effective. There are several successfuldesigns; a simple constructed type is shown in figure4-13.

Copper tubing is often used in an oil supply systemto burners because of its high resistance to corrosionand ease of installation. The use of compressionfittings or flair fittings is best for fuel supplyapplications. A major advantage in using coppertubing is that it can be bent easily without collapsingthe tube, especially if a tubing bender is used; this cutsdown on the number of fittings required forinstallation.

Figure 4-12.—Space heaters installed in series.

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Figure 4-13.—H-type downdraft hood.

UNIT HEATER MAINTENANCE

Oil-fired space heaters require periodic cleaning.Frequent checks must be made to ensure thatequipment is kept clean, because accumulations ofcarbon and soot can cause disastrous fires. Unitsshould be moved when they are cleaned, so they can becleaned inside and out. Accumulations of soot must beremoved from inside the fuel pipe. All piping andtubing should be kept clean and free of oil drippings.

The pot or burner assembly may be cleanedwithout removing the heater. When cleaning thiscomponent, remove it through the front door openingand clean all the air holes using a soft copper wire. Donot remove all the carbon from the bottom, because asmall accumulation of carbon at the bottom acts as awick and helps maintain the pilot light. In replacing theburner assembly, make sure both sides of the burnerare tightened equally, so the top of the burner and thefire-retardant gasket are set firmly against the flueprojection.

In checking the constant-level control valve, checkthe operation of the heater through a complete cycle ofoperation from the pilot fire position to the main fireposition, and then back to the pilot fire position. Set thecontrol valve, if it is the manual type, to high fire; and ifequipped with a thermostatic device, set the thermostatabove room temperature. If the heater fails to operateproperly through the cycle, check the constant-level

control valve and fol low the manufacturer 'sinstructions for disassembly and cleaning. A partsbreakdown of the valve is shown in figure 4-14.

Some of the common problems with pot and sleeveoil burners, gas-fired space heaters, their causes, andpossible remedies are listed in appendix II, tables I andgentlemen.

Q8.

Q9.

Q10.

Q11.

Q12.

Q13.

Q14.

What are the basic types of unit heaters?

How are electrically powered space heatersgenerally rated?

When you select and install an electric spaceheater, what factor should be paramount?

On vented gas-fired space heaters, it isimportant to install the venting system properlyto minimize the effects of what problem?

What type of burner is used in an oil-fired spaceheater?

What is the only safety device on an oil-firedspace heater?

To maintain a constant draft for the burner of anoil-fired space heater, what device should youinstall in the chimney?

Figure 4-14.—Constant-level control valve.

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WARM-AIR HEATING SYSTEMS

Learning Objective: Identify the different types ofwarm-air systems, gas-fired and oil-fired furnaces,components, controls, and the procedures forinstallation, operation, and maintenance.

Heating equipment for complete air-conditioningsystems is classified according to the type of fuelburned, the Btu capacity of the furnace, and the methodof circulating the warm air. Warm-air systems aregenerally identified as either a gravity-type or aforced-air type system.

GRAVITY SYSTEM

Gravity furnaces are often installed at floor level.These are really oversized, jacketed space heaters. Themost common difficulty experienced with this type offurnace is a return-air opening of insufficient size at thefloor. Make the return-air opening on two or threesides of the furnace wherever possible. Provide heatinsulation above the furnace top to avoid a possible firehazard.

Gravity warm-air heating systems operate becauseof the difference in specific gravity (weight) of warmair and cold air. Warm air is lighter than cold air andrises when cold air is available to replace it.

FORCED-AIR SYSTEM

The majority of the furnaces produced today are ofthe forced warm-air type. This type of furnace includesthe elements of a gravity warm-air system plus a fan toensure adequate air distribution. It may include filtersand a humidifier to add moisture to the air. Theinclusion of a positive pressure fan makes possible theuse of smaller ducts and the extension of the system toheat larger areas without the need for sloping ducts. Itis possible to heat rooms located on floors below thefurnace if necessary. Forced-air furnaces aremanufactured in a variety of designs. A typicaloil-fired furnace is shown in figures 4-15 and 4-16. Atypical gas-fired furnace is shown in figure 4-17.

In a forced-air system, the fan or blower is turnedon and off by a blower control which is actuated by theair temperature in the bonnet or plenum. The plenum is

Figure 4-15.—Cutaway view of a typical oil-designed furnace.

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Figure 4-16.—Cutaway view of a horizontal stowaway oil furnace.

Figure 4-17.—Gas-fired vertical warm-air furnace.

that part of the furnace where it joins the main trunkduct (fig. 4-18). The blower control starts the fan orblower when the temperature of the heated air rises to aset value and turns the fan or blower off when the

temperature drops to a predetermined point. Thus theblower only circulates air of the proper temperature.

AIR DISTRIBUTION

A knowledge of air distribution principles isimportant when dealing with central warm-air heatingsystems. Satisfactory heating from warm-air systems isabsolutely dependent upon proper distribution of warmair from the heat source to all portions of the spaceserved. Warm air must be distributed in quantities thatare required to offset the rate of heat released to eachroom. With radiator systems, distribution is primarily aproblem of getting enough hot water or steam to eachradiator to be sure the radiator heats to its rated capacity.It is not possible to deliver more heat through steam orhot water than the radiator is designed to transmit. Withwarm-air systems, however, the rate of air delivery andthe temperature of the air delivered to the roomdetermine the amount of heat reaching each room.Temperature balance, therefore, is primarily a problemof controlling air distribution.

Factors, such as velocity, volume, temperature,and airflow direction, play an important part intemperature balance. In addition and for humancomfort, space-temperature variations and noise levelsmust also be considered. Convection currents resultfrom the natural tendency of warm air to rise and coldair to fall. Examples are the temperature variationsnear doors and windows, and when dense, cool air isdrawn away quicker than warm air. Objectionablenoise will result at supply diffusers if room velocitiesexceed 25 to 35 feet per minute (fpm). Air stratificationand cold floors may also result when supply diffusersare not properly located within the space.

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Figure 4-18.—Electrical circuit showing how blower control operates blower motor when temperature in plenum rises.

Patterns of air distribution vary with the positionsof supply diffusers. A diffuser that discharges throughthe floor in an upward direction or downward throughthe ceiling provides a vertical distribution of air. Onthe other hand, a diffuser that discharges through a wallprovides a horizontal distribution of air. The spread foreither the horizontal or the vertical pattern depends onthe setting of the diffuser vanes. A low horizontal

discharge provides the most effective distributionAirdistribution that results from different diffuserlocations is shown in figure 4-19.

As previously mentioned, warm-air heating systemsare generally identified as either the GRAVITY TYPE orthe FORCED-AIR TYPE. The type of duct distributionused further identifies these installations. There are two

Figure 4-19.—Air diffuser distribution.

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types of duct layouts: (1) the INDIVIDUAL DUCT,where each duct is connected directly to the furnaceplenum, and (2) the TRUNK AND BRANCH DUCT,where the trunk duct connects to the furnace plenum andthen branches off to the outlets. These two types areshown in figures 4-20 and 4-21.

Gravity-type furnaces are rated in leader areacapacity, the LEADERS being the warm-air pipes.With respect to return ducts, the register-free area andthe return-air duct should not be less than 1 1/4 timesthe area of the leader serving a given area. Gravity-typeinstallations, as shown in figure 4-21, use theindividual duct layout.

Forced warm-air systems usually have a registertemperature range of 150°F to 180°F. Ducts can be inthe form of a trunk with branches or with individualleaders from a plenum chamber. Furnaces used withforced-air installations must be equipped withautomatic firing devices. Velocities usually are in therange of 750 to 900 fpm in trunks and approximately600 fpm in branches. Outlet velocities at registers maybe as high as 350 fpm.

GAS-FIRED FURNACES

In this section, construction features, basiccomponents, gas burners, and controls of gas-firedfurnaces are discussed.

Construction Features

The various gas-fired furnaces available todayhave similar basic components; however, there, arevariations in design with respect only to dimensionsand airflow. Unit features pertinent to dimensions andairflow are important when selecting a furnace for aparticular space or application. A vertical counter-flowunit, for example, is normally used where supply ductsare located beneath the floor, because it has the returnin the top and the outlet in the bottom. The mostcommonly used unit is the UPFLOW HIGHBOYwhich, as a rule, draws air from the side or bottom anddischarges it from the top. It can be installed in smallspaces. In the HORIZONTAL UNIT, the air flows inone side and out the other. This unit is suitable forinstallation in crawl spaces, attics, and basements. Inanother type, sometimes called a LOWBOY, both thereturn and the outlet are at the top. It is a shorter andwider version of the up-flow unit. The differentairflows are shown in figure 4-22.

Another type of furnace is the DUCT FURNACE.It is designed for mounting in a duct system where aircirculation is provided by an external fan. It isgenerally used with an air- conditioning system tosupply heat during the heating season by using thesame ductwork. This type can be installed as asingle unit or in batteries for larger requirements. A

Figure 4-20.—Trunk and branch duct distribution systems.

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Figure 4-21.—A typical gravity warm-air heating system (individual duct).

Figure 4-22.—Furnace airflow designs.

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typical gas-fired duct furnace is shown in figure4-23.

Gas-fired furnaces have three main parts—thereturn-air compartment that houses the blower and filtercomponents, the warm-air compartment that includesthe heat exchanger radiators and combustion enclosure,and the combustion air and fuel compartment. Thisarrangement is shown in figure 4-24.

Basic Components

The components and assemblies of a gas-firedfurnace can be broken down into six units. Each unit isdiscussed briefly below. Refer to figures 4-23 and 4-24as we go along to identify the location of individualparts.

The furnace casing, sometimes called the cabinet,along with the framework, contains and supports thecomponents of the unit. It also provides an insulatingchamber for directing return air through the heatexchanger into the warm-air outlet.

The blower is a centrifugal fan that provides thecirculation required to move warm air across theheated space. It also pulls the return air from the spaceback to the furnace.

The burners are usually the Bunsen type regardlessof their size or shape. Figures 4-25 and 4-26 showBunsen burners. The burner nourishes the flame, as itprovides the correct mixture of primary air and fuel gasto the combustion area.

Figure 4-23.—Typical gas-fired duct furnace.

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Figure 4-24.—Internal view of a furnace.

The gas manifold assembly includes the gasvalves, pressure regulator, and those components thatautomatically control the flow of gas to the pilot andmain burner. It is directly connected to the burner.

burner mixing tube or "venturi," where it mixes withthe gas that burns at the burner ports. The secondary airis supplied around the base of each separate burnerflame by natural draft or is induced by a draft fan.

Gas Burners and Controls

To use natural gas, a nearly ideal fuel, requirescomparatively simple equipment and unskilled labor.This clean gas is almost free of noncombustible and istherefore clean. However, it is relatively dangerouscompared to coal or oil because it mixes easily with airand burns readily. Extreme care must be exercised toprevent or stop any leakage of gas into an unlightedfurnace or into the boiler room. All gas burners shouldbe approved by the American Gas Association andinstalled according to the standards of the NationalBoard of Fire Underwriters.

The gas burners used in gas-fired furnaces usuallyhave a nonluminous flame and are the Bunsen type, asshown in figures 4-25 and 4-26. Part of the air neededfor combustion is primary air that is drawn into the

The gas burner controls include the followingunits—manual gas valve, gas pressure regulator,solenoid gas valve, diaphragm valve, pilot light,thermocouple, thermocouple control relay limitcontrol, heat exchanger, draft diverter, and humidifier(fig. 4-27). A manual gas cock or valve must beinstalled ahead of all the controls.

MANUAL GAS VALVE.—The manual gasvalve is installed on the heating unit next to the gaspressure regulator. It is used to shut off the gas to theheating unit in case some of the controls must berepaired or replaced.

GAS PRESSURE REGULATOR.—The gaspressure regulators used in domestic gas-heatingsystems are usually of the diaphragm type, as shown infigure 4-28. A gas pressure regulator maintains thedesired pressure in the burner as long as the gas main

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Figure 4-25.—Typical Bunsen burners.

Figure 4-26.—Bunsen type of burner.

pressure is above the desired pressure. When the gaspressure to the burner is low, the pressure-regulatingspring pushes the diaphragm down, in turn, pushingthe pilot valve down. When the pilot valve opens,supply pressure is applied to the top of the operatingpiston. As the operating piston moves down, the mainvalve opens, admitting supply pressure to the burner.As burner pressure rises, the diaphragm is pushed upagainst the pressure-regulating spring, closing thepilot valve. This removes the supply pressure from thetop of the operating piston and the piston return springpushes the piston up, closing the main valve. Theregulator is thus closed every time the burner pressure

gets above the desired amount. Turning the adjustingscrew at the top can vary the setting of the regulator.

SOLENOID GAS VALVE.—The basicprinciples of construction and operation applied in allsolenoid gas valves are similar. However, the design ofeach individual unit differs somewhat from the others.The two most common types of solenoid gas valves arethe standard solenoid valve and the recycling solenoidvalve discussed in the following paragraphs.

The standard solenoid gas valve shown in figure4-29 is of the electric type. It is suitable for use withgas furnaces, steam and hot-water boilers, conversionburners, and industrial furnaces. This valve operateswhen a thermostat, limit control, or other device closesa circuit to energize the coil. The energized coiloperates a plunger, causing the valve to open. Whenthere is a current failure, the valve automatically closesbecause of the force of gravity on the plunger and valvestem. The gas pressure in the line holds the valve diskupon its seat. To open this valve during current failure,use the manual-opening device at the bottom of thevalve. When the electric power is resumed, you shouldplace the manual-opening device in its formerposition.

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Figure 4-27.—An automatic gas burner control system.

Figure 4-28.—A gas pressure regulator.

The recycling solenoid gas valve shown in figure4-30 can be used with the same heating equipment asthe standard solenoid gas valve. The design of thisvalve differs from that of the standard solenoid gasvalve, because it is equipped with an automaticrecycling device that allows the valve to switch tomanual operation during power failure. However,upon the resumption of power, the thermostatautomatically resumes control of this valve.

DIAPHRAGM VALVE.—The diaphragm gasv a l v e s h o w n i n f i g u r e 4 - 3 1 c a n b e u s e d

Figure 4-29.—A standard gas solenoid valve.

interchangeably with a solenoid gas valve. Its mainfeature is the absence of valve noise when it is openingor closing. In this type of diaphragm valve, the relayenergizes and opens the three-way valve, so the gaspressure on the top of the diaphragm is released to theatmosphere. Reducing the pressure on the top of thediaphragm in this manner causes the gas supplypressure to flex the diaphragm upward, opening themain gas valve. When the relay is de-energized, thevent to the atmosphere is sealed and pressure from the

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Figure 4-30.—A recycling solenoid valve.

Figure 4-31.—A diaphragm gas valve.

gas supply is allowed to be applied to the top of thediaphragm, forcing it down and sealing the main valve.

PILOT LIGHT.—The gas pilot light in agas-heating unit is a small flame that burnscontinuously and lights the main burner during normaloperation of the heating unit. It is located near the mainburner, as shown in figure 4-27.

The gas flow to the pilot light is, in some cases,supplied by a small, manually operated gas shutoffvalve on the main gas line above the main gas valve. Inother cases, the gas can be supplied from the pilottapping on a solenoid gas valve, as shown in figure4-29. In more expensive heating units, the gas for thepilot light is often supplied by a thermocouple-controlled relay.

THERMOCOUPLE. —A thermocouple isprobably the simplest unit in the electrical field that isused to produce an electric current by means of heat. It

is constructed of two U-shaped conductors of unlikemetals in the form of a circuit, as shown in figure 4-32.If these conductors were composed of copper andnickel, respectively, and are joined as shown in thefigure, two junctions between the metals exist. If aflame heated one of these junctions, a weak electriccurrent would be produced in the circuit of theseconductors. A series of junctions can be arranged toform a thermopile to increase the amount of currentproduced, as shown in figure 4-33.

In the heat ing f ield, thermocouples andthermopiles are used to produce the electrical currentused to operate such units as gas valves, relays, andother safety devices.

The thermocouple is located next to the pilot lightof the main gas burner, as shown in figure 4-27. Itgenerates the electric current (usually 50,000microvolts) which holds open a main gas valve, a relay,or any other safety devices, permitting gas to flow tothe main burner. Soon after the pilot light isextinguished, current ceases to flow to these safetydevices, thus causing them to shut off the gas to theheating unit. These safety devices will not operateagain until the pilot light is lighted and current is againgenerated by the thermocouple.

THERMOCOUPLE CONTROL RELAY.—The thermocouple-operated relay shown in figure 4-34is a safety device used on gas-fired heating equipment.The thermocouple, when placed in the gas pilot flame,generates electricity. The electric current energizes anelectromagnet that holds a switch or valve in the OPENposition as long as the pilot flame is burning. When thepilot flame goes out because of high drafts or fuelfailure, the electromagnet is de-energized, thus closingand preventing the opening of the switch or valve. The

Figure 4-32.—The principle of a thermocouple.

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Figure 4-33.—A thermopile.

Figure 4-34.—A typical thermocouple and valve relayassembly.

closing of the valve or switch prevents the burner fromfilling the combustion chamber with unburned gases.

To re-light the pilot light, push up the reset buttonat the bottom of the relay and allow the gas to flow tothe pilot light. Since some heating units are notequipped with relays, the pi lot l ight is notautomatically shut off in case of gas supply failure.

The relay shown in figure 4-35 is an electricalswitch type of relay. It is entirely electrical and can beused as a controlling unit for either the magnetic ordiaphragm gas valves. This unit is actuated by theelectric current generated by the thermocouple. Itcontrols the operation of the gas valve in the magneticand diaphragm valves. A relay of this type must also bereset manually for normal operation.

LIMIT CONTROL.—The limit control in a gasburner system is a safety device. It shuts off the gassupply when the temperature inside the heating unitbecomes excessive. The limit control device can beadjusted to the desired setting. It exercises directcontrol on the gas or diaphragm valve.

HEAT EXCHANGER.—This unit or assemblymay be either a single or sectional contoured steelshell. It extends vertically from the burner enclosure tothe flue exit. Functionally, it transmits heat from thehot gases of combustion to the circulating warm airthat passes the outer surfaces.

Draft Diverter.—The diverter is simply a sheetmetal chamber that encircles the flue. It has an openingat the bottom to allow air to be drawn in by the fluedraft. Its purpose is to reduce the downdrafts andupdrafts that are objectionable to pilot and burneroperation.

Humidifiers. —Humidifiers used with forcedwarm-air heating systems are usually of the pan typeshown in figure 4-36. Unless the water is relatively freeof solids, these humidifiers require frequent attention,since the float may stick in the OPEN position or thevalve may clog. Overflowing of the pan may result in acracked heating section, and a stopped-up inlet valvewill make the humidifier inoperative.

The drum type of evaporative humidifier uses anevaporation pad in the shape of a wheel. Theslow-turning wheel is submerged in the water in thelower pan where the spongelike plastic foam materialbecomes saturated with water. The wheel lifts thisportion of the pad and exposes it to the warm, dry airflowing through it. The air then absorbs more moisturebecause of lower relative humidity at a highertemperature.

OIL-FIRED FURNACES

Oil-fired furnaces are similar to gas-fired units inphysical arrangement. Internally, oil-fired units havethree areas—the burner compartment, the combustion

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Figure 4-35.—An electric switch type of relay.

Figure 4-36.—Cutaway view of a typical humidifier.

and radiating chamber, and the blower compartment.Figure 4-37 shows a cutaway view of a typical oil-firedfurnace.

Like gas-fired units, oil-fired units are alsoavailable with various airflow designs. The modelshown in figure 4-15 is designed with both thereturn-air inlet and the warm-air outlet in the top. Morecompact models (fig. 4-37) are available with thereturn-air inlet at the side or bottom below the radiatingand combustion area. The warm-air outlet is at the top.

A floor furnace is shown in figure 4-38. This typeof oil-fired unit is smaller, lighter in construction, andis designed to be hung from the floor of the spaceserved. Only a minimum of clearance is requiredbelow the floor.

Oil burners may be separated into various classes,such as domestic and industrial. Since domestic oilburners are used almost universally in warm-air

furnaces, they are the only ones covered in detail in thischapter.

Domestic Oil Burners

Domestic oil burners atomize the oil and areusually electrically power driven and are used in smallcentral heating plants. They deliver a predeterminedquantity of oil and air to the combustion chamber,ignite it, and automatically maintain the desiredtemperature.

Domestic oil burners are classified according tovarious methods, none of which is entirely satisfactorybecause of the overlapping among a great number ofmodels. Classification may be by type of ignition,draft, operation, method of oil preparation, or featuresof design and construction.

DESIGN AND CONSTRUCTION.—One of themost common types of domestic oil burners is thepressure-atomizing gun type of burner. Gun type

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burners atomize the oil by fuel-oil pressure. Thefuel-oil system of a pressure-atomizing burner consistsof a strainer, pump, pressure-regulating valve, shutoffvalve, and atomizing nozzle (fig. 4-39). The nozzle andelectrode assembly includes the oil pipe, nozzleholder, nozzle, strainer, electrode insulators,electrodes, supporting clamp for all parts, and staticdisk. The oil pipe is a steel rod with a fine hole drilledthrough it. This hole reduces oil storage in the nozzle toa minimum that prevents squirting at the nozzle whenthe burner shuts off.

The air system consists of a power-driven blowerwith means to throttle the air inlet, an air tube thatsurrounds the nozzle and electrode assembly, andvanes or other means to provide turbulence for propermixing of the air and oil. The blower and oil pump aregenerally connected by a flexible coupling to theburner motor. Atomizing nozzles can be furnished tosuit both the angle of spray and the oil rate of aparticular installation. Flame shape can also be variedby changing the design of the air exit at the end of theair tubes. Oil pressures are usually about 100 psi, butpressures considerably greater are sometimes used.

Electric ignition is almost exclusively used.Electrodes are located near the nozzle but must not bein the path of the fuel oil spray. The step-uptran sform er provides the high voltage (usually 10,000

the electrode tips.volts) necessary to make an intense spark jump across

Figure 4-37.—Cutaway view of a typical oil-fired furnace.

Figure 4-38.—Oil-fired floor furnace.

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Figure 4-39.—High-pressure gun type of oil burner.

body of the pump, it is correctly arranged for asingle-line system. It is set up for a two-line systemwhen the cover is turned so Number 2 is adjacent to thesame letter.

A two-line system is necessary when the bottomof the fuel tank is below the level of the pump. Thesuction line from the tank is connected to the pumpport marked "Inlet." The return line is connected tothe pump bypass port and is directed back into thetank. With the one-line system, the return line is notused.

Ignition Electrodes.—The heat of a sparkjumping between two ignition electrodes ignites thefuel (fig. 4-39). The voltage necessary to cause thespark to jump is much more than the line voltageavailable. Therefore, an electric transformer is usedto step up the line voltage to approximately 10,000volts.

FUEL UNIT.—There are many types of fuel unitsavailable for oil burners; however, the T-type,two-stage fuel unit is the most commonly used. Figure4-40 shows this type of unit. It is an oil pump with twostrainers mounted on the body of the oil burner and

blades mounted on a vertical shaft directly connected

operated by the blower motor shaft.

to the motor. The oil distributor projects the oil to aflame ring made of either refractory material or metal.Figure 4-41 shows this type of burner. The hot flamering vaporizes the oil, and the oil vapors mix with airand burn with a quiet blue flame that sweeps the walls

The T-type, two-stage fuel unit can be used on asingle-line or on a two-line system. When Number 1 onthe strainer cover is next to the letter marked on the

of the furnace. Ignition may be electric, gas-electric, orgas. High-grade fuel oil is necessary for satisfactoryperformance.

The wall flame burner has an oil distributor and fan

Figure 4-40.—A typical T-type, two-stage fuel pump.

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Figure 4-41.—Vertical-rotary burner of the vaporizing or wallflame type.

Horizontal Rotary Type.—The horizontal rotarytype was originally designed for industrial use;however, sizes are available for domestic use. It has awider range of fuel-burning capacity than thehigh-pressure gun type and can accommodate heaviergrades of fuel. Figure 4-42 shows this type of burner.

The major parts of the burner are the housing, fan,motor, fuel tube, and rotating atomizing cup. Theatomizing cup and fan are driven at the same speed by adirectly connected electric motor. Oil is fed throughthe fuel tube to the inner surface of the atomizing cup.The oil spreads over the surface of the cup, which turnsat 3,450 revolutions per minute (rpm). It then flows tothe edge of the cup where it is thrown off. The whirlingmotion and the resulting centrifugal force separates theoil into fine particles, as it leaves the cup. Primary airsupplied by the fan is thrown in around the outer edgeof the rotating cup and given a whirling motion in thedirection opposite that of the oil. The streams of air andoil collide and thoroughly mix, as they enter thecombustion chamber.

OIL BURNER CONTROLS.—The purpose ofoil-burner controls is to provide automatic, safe, andconvenient operation of the oil burner. The system isdesigned to maintain the desired room temperature, to

Figure 4-42.—A horizontal-rotary oil burner.

start the burner as required, and to ignite the fuel toinitiate combustion. However, in case trouble arisesduring operation, the burner must be stopped andfurther operation prevented until the trouble has beencorrected.

Oil-burner controls are essentially the same asstoker or gas controls. The only difference is that theoil burner has, in addition, two ignition electrodes anda primary or safety control. A diagram of a typicalforced warm-air control system is shown in figure4-43.

Primary Control.—The burner primary control iselectrically connected between the thermostat and theburner, as shown in figure 4-43, and it performs severalfunctions. The primary control closes the motor andignition circuits when the thermostat calls for moreheat. It breaks the motor circuit and stops the burnerwhen the motor first starts if the fuel fails to ignite or ifthe flame goes out. The control prevents starting of theburner in case of electrical failure until all safetydevices are in the normal starting position.

An interior view of a primary control is shown infigure 4-44. This control device is also equipped with ahigh-temperature limit control. This control shutsdown the heating plant whenever the temperature ofthe furnace becomes excessive. For example, if thethermostat is exposed to a blast of cold air for a longperiod of time, the heating plant could run long enoughto become overheated to the point of severe damage orexternal fire if it was not for this high-temperature limitcontrol.

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Figure 4-43.—Typical forced warm-air control system.

Limit Control.—The limit control is a device thatresponds to changes in air temperature (in a warm-airheating system), to changes in water temperature (in ahot-water heating system), and to changes in steampressure (in a steam-heating system). The limit control

has two distinct functions. The first function is tocontrol the operation of the fire so the temperature andpressure of the heating plant never exceeds safeoperating limits. This function is distinctly for safetycontrol.

The second function of the limit control is to limitthe temperature and pressure of the heating system forbetter temperature regulation in the building. Thisfunction is particularly useful in controlling coal-firedheating systems where the coal bed continues to giveoff heat when the stoker motor stops. By lowering thesetting of the limit control, however, it is possible toprevent an excessively hot fire that would continue tothrow off excessive amounts of heat after thethermostat has been satisfied.

Temperature-Responsive Devices.—Manyautomatic control units, such as the thermostat, limitcontrol, fan control, and many others, must respond totemperature changes. Actually, these are theinstruments that use a temperature change to cause theelectrical contacts inside each unit to open and close.The opening and closing is an indicating signal that istransmitted to the primary control for specific action,such as starting or stopping the operation of the heatingplant.

Bimetallic Strip.—Some automatic control unitsare equipped with a switch that contains a straight

Figure 4-44.—Interior view of a primary control.

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bimetallic strip to open and close electrical contacts.This actuating device is made by welding together twopieces of dissimilar metals, such as brass and Invar, asshown in figure 4-45, view A. Below a certainpredetermined temperature, this strip does not deflector bend. However, when the strip is heated, it bends inthe direction of the metal that expands the least, asshown in figure 4-45, view B.

Actually, this electrical switch is constructed, asshown in figure 4-45, view C, by welding two electricalconnections and contacts to the strip. A switch of this typecan then be used to control electrical circuits, because thebimetallic strip responds to temperature changes. This isa basic example of how this principle of bimetallic strip

operation is used in many temperature-responsiveautomatic units. Other control switches containbimetallic strips that are spiral, U-shaped, Q-shaped, oreven in the shape of a helix, as shown in figure 4-46.

Vapor-Tension Device.—The vapor-tensionprinciple is also used to actuate some types ofautomatic control units. This is a common type oftemperature-measuring device in which the effects oftemperature changes are transmitted into motion by ahighly volatile liquid. The most used vapor-tensiondevice is the simple compressible bellows, as shown infigure 4-47, view A.

The bellows is made of brass. It is partially-filledwith alcohol, ether, or other volatile liquid not

Figure 4-45.—Bimetallic strips: A. Typical strip; B. Expansion of the strip; C. With electrical switch.

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Figure 4-46.—Various types of bimetallic strips.

corrosive to brass. When the temperature around thebellows increases, the heat gasifies the liquid insideand causes the bellows to extend. The extension closesa set of electrical contacts, as shown in figure 4-47,view B. When the bellows cools again, it contracts.The contraction opens the electrical contacts.

Remote-Bulb Device.—Liquid-filled devices arenot always limited to the simple bellows. There aresome remote-bulb devices that not only have a bellowsbut also have a capillary tube and a liquid-filled bulb,as shown in figure 4-48.

When the liquid in the bulb is heated, part of itgasifies and forces its way through the capillary tubeinto the bellows. This increased pressure inside thebellows causes it to extend and open a set of electricalcontacts (or open or close a valve). When the bulbcools, the gas liquefies and decreases pressure insidethe bell ows. This decreased pressure allows thebellows to contract and close the electrical contacts.

Pressure-responsive devices are actuatingmechanisms installed in units, such as steam-pressurecontrols, steam-pressure gauges, and pressureregulators.

Bellows.—One type of pressure-responsiveactuating device uses bellows in a way similar to that ofthe remote-bulb type. In this application, the bellowsextends and contracts in response to changes in steampressure. The action caused by movement of thebellows opens or closes a set of electrical contacts.

B o u r d o n T u b e .—Another type ofpres sure-responsive actuating device is found inside ofthe pressure gauge shown in figure 4-49. In thisactuating device, the pressure is applied inside a

Figure 4-47.—Tension devices: A. Vapor-tension device;

B. Pressure-tension device closing electrical contacts.

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Figure 4-48.—Schematic of a remote-bulb device.

Figure 4-49.—A typical Bourdon spring tube.

hollow, partially flattened, bent tube, called a Bourdonspring tube. The pressure inside this tube tends tostraighten it, and in so doing, it moves the levermechanism that turns the pointer. The pressure gaugemeasures the pressure in pounds per square inch (psi).

Humidity-responsive devices open or closesolenoid or motorized valves, which control the flowof water or steam to humidifying equipment. Thesensitive element, which actuates the motion in thisdevice, consists of a group of human hairs. These hairslengthen when the humidity is high and shorten whenthe humidity is low.

Accumulation of dust and grease on these hairs,while not damaging, may decrease the sensitivity ofthe controller. Consequently, the element should be

cleaned periodically with a camel's-hair brush andclean ether. A complete wetting with distilled watershould follow this cleaning.

Electrical Switches.—Electrical switches inheating control equipment operate electrical circuits inresponse to signals from automatic control units. Inother words, the actions initiated by devicesresponsive to temperature, pressure, and humiditychanges open or close switch contacts. These, in turn,control the operation of the heating plant throughelectrical circuits. Switches may be either thesnap-action type or the mercury type.

Snap-action switches vary in their designs.-Someare constructed so they have an over-center springarrangement that is designed so the movement of theactuating lever engages the spring and causes theswitch to move with snap-action. The snap-action typeof switch is shown in figure 4-50, view A.

Another snap-action switch shown in figure 4-50,view A, has a small magnet that causes the electricalcontacts to remain firmly closed. It also provides theswitch with the snap-action effect. The contacts of thisswitch must open or close quickly to avoid excessivearcing across the points. Arcing burns the contactingsurfaces, which eventually causes switch failure.

A mercury switch has the electrical contacts and asmall amount of mercury in a hermetically sealed shortglass tube, as shown in figure 4-50, view B. Tilting theswitch causes the mercury inside the tube to cover oruncover the contacts. When the contacts are covered,the electrical circuit is completed.

Every electrical switch is designed so it has aspecific rated capacity in amperes and volts; forexample, a capacity of 8 amperes at 110 volts. Anelectrical switch should never be overloaded becauseoverloading causes overheating, which eventuallyresults in switch failure that can create a fire hazard.

The standard controls furnished for automaticfuel-burning equipment come in sets designed forwarm-air, hot-water, and steam-heating systems. Astandard set usually consists of a thermostat, limitcontrol, primary control, and electric motor. Auxiliarycontrols are those designed for a specific function in awarm-air, hot-water, or steam-heating system. Theyare in addition to the standard controls.

Thermostat. —The thermostat is the nerve centerof the heating-control system. It is the sensitive unitthat responds to changes in room temperature. Itindicates whether more or less heat is required from the

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Figure 4-50.—Electrical switches: A. Snap-action switch;B. Mercury switch.

heating plant. It transmits the indicating signal to aprimary control for action. This indicating signal isinitiated by closing or opening electrical contacts in thethermostat.

Thermostats often differ in construction accordingto the type of primary control with which they are to beused. Probably the most used thermostats are thespiral-bimetallic type and the mercury-bulb type.

An electric clock thermostat has the additionalfeatures of an electric clock and an automaticmechanism that can be adjusted to change thethermostat setting at a desired time. For instance, it canbe adjusted to reset the thermostat automatically from80°F to 60°F at 11:00 p.m. (when 80oF heat is notneeded). Then it will reset the thermostat to 80oF at6:00 a.m. (when more then 60°F heat is needed).

The location for the thermostat should berepresentative of that part of the building in which heatis needed to maintain a comfortable temperature. Thebest location is on an inside wall, just a few feet from an

outside wall and about 4 1/2 feet above the floor. Thethermostat wiring must conform to local electricalordinances.

To check the calibration of a thermostat, hang-anaccurate test thermometer within 2 inches of thedevice. Allow 15 to 30 minutes for the thermostat andthe rmomete r to ad jus t themse lves to roomtemperature. The thermostat contacts should closewhen the control knob or dial is set at the temperatureindicated by the test thermometer. You should not tryto recalibrate the thermostat if the closing point varies1°F or less. When calibration is necessary, follow themanufacturer's instructions.

FURNACE INSTALLATION

Since there are many types and makes of oil- andgas-fired warm-air furnaces on the market, detailedassembly instructions to suit all makes and typescannot be given in this manual. However, somegeneral instructions, which apply to both oil-fired andgas-fired furnaces, except as noted, are given below.

Carefully follow assembling instructions includedwith each furnace or blower shipment. Each piece orcasting is manufactured to fit in its proper place. Partsare seldom interchangeable.

Install furnaces in a level position. If the floor isuneven, use a steel wedge, a cast-iron wedge, or theleveling bolts provided on some equipment. Use aspirit level to make sure the unit is level.

Gas-fired and oil-fired forced-air units, whichhave the blower below the heating element orcombustion chamber, should be set on masonry at least3 inches thick and extending at least 12 inches beyondthe casing wall. Install all other units on a cold masonryfloor. Provide enough clearance to permit easy accessfor repairs. Make the clearance at least 18 inches fromwood or other combustible material unless you installan asbestos board at least 1 inch from the combustiblematerial. Units may be installed near masonry walls;however, leave ample room to permit proper servicing.

Furnace cement is furnished with each cast-ironfurnace. Seal all furnace joints with a liberal amount offurnace cement between sections to ensure the furnaceis gastight. Asbestos rope is furnished with a numberof furnaces; follow the manufacturer's instructionscovering its use. See that projections from the furnace,such as the smoke pipe or clean-out doors, extendthrough the outside of the casing.

In assembling a furnace, be sure to tighten all bolts.Draw each bolt until it is almost tight. Then, after all

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bolts have been installed, draw each one graduallyuntil all are uniformly and properly tight. Avoiddrawing bolts too tight, as this can crack or break acasting or buckle a steel plate.

After assembling the furnace, check all doors forfree operation and tight fit.

Install the downdraft diverters furnished with theequipment on all gas-burning furnaces. Diverters aredeveloped for individual furnaces.

Use a vent or smoke pipe that is at least as large asthe smoke-pipe outlet of the furnace.

Securely fasten the vent or smoke pipe at each jointwith a minimum of three sheet metal screws. Installhorizontal pipe with a pitch upward of at least l-inchper linear foot (fig. 4-51).

Ventilate the furnace room adequately to supplyair for combustion. Provide an opening having 1square inch of free-air area for each 1,000 Btu per hourof furnace input rating with a minimum of 200 squareinches. Locate the opening at or near the floor linewhenever possible. In addition, provide two louveredopenings, each having a free-air area of at least 200square inches in it, at or near the ceiling as nearopposite ends of the furnace room as possible.

Tank installation is largely governed by localconditions. Listed here are the principles of tankinstallation that give greatest freedom from serviceproblems. Adhere as closely to these recom-mendations as local conditions permit.

Figure 4-51.—Typical smoke pipe (flue) installation.

When possible, install single-pipe gravity oil feedon inside tanks or elevated outside tanks (fig. 4-52).This type of installation is used for single-stage pumps.Use a 1/4-inch globe valve at the tank instead of alarger size. Larger valves sometimes cause tank hum.

For all installations, use a continuous piece of1/2-inch copper tubing from the oil tank or valve to theburner and a similar piece for the return when required.The principle is to minimize the number of joints andthus minimize the possibility of air or oil leaks.

For inside installations where it is necessary to runthe piping overhead between the tank and burner, whenthe burner is either above or below the tank level, thetwo-pipe system is recommended. This requires theuse of a two-stage pump.

A dual-stage pump may be changed from asingle-stage to a two-stage pump to accommodate asingle-pipe or two-pipe system. The stages on aWebster fuel pump can be changed by removing thefour screws on the pressure side of the pump and liningthe Number 1 up with the letter on the pump body for aone-pipe system. The Number 2 lined up with the letteris for a two-pipe system. Most Sunstrand fuel pumpsare shipped from the factory set up for a one-pipesystem. To change to a two-pipe system, remove the3/8-inch pipe plug from the bottom of the pumphousing. There you will find an Allen head plug.Remove this plug for a two-pipe system.

Install the outside tanks (fig. 4-53) according to theinstruction below.

Normally, when you are installing an undergroundfuel tank, the suction and return lines are made of blackiron from the tank to the inside of the building, andthere the burner is connected by copper tubing with acoil in it (not shown in the illustration) to eliminatevibration.

The return line is usually installed in the oppositeend of the tank. Carry it to within 5 inches of thebottom. This creates an oil seal in the two lines, and anyagitation caused by return oil is safely away from thesuction line.

A 1 1/2-inch fill line and a 1 1/2-inch vent line arerecommended. Carry the vent well aboveground andput a weatherproof cap on it. Pitch the vent line downtoward the tank.

Use special pipe dope on all iron pipe fittings thatcarry oil. Treat the underground outside tank andpiping with a standard preparation or commercialcorrosion-resistant paint.

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Figure 4-53.—Diagram of piping for buried outside tank.

MAINTENANCE OF FUEL OIL SYSTEMS Fuel Oil Firing

Among the major duties of the Utilitiesman are

troubleshooting and servicing oil burners. To keep the

burner in good operating condition, you must be able to

recognize the symptoms of various types of trouble

and must know how to make various service and

maintenance adjustments to the burner.

Because fuel oils do not burn in the liquid state,

several physical conditions must be attained to affect

complete and efficient combustion.

1. Either the liquid must be thoroughly vaporized

or gasified by heating within the burner, or the

burner must atomize it so vaporization can

Before getting into a discussion on trouble- occur in the combustion space.

shooting and servicing of oil burners, let’s point out

some information on fuel oil firing.

2. The mist must be thoroughly mixed with

sufficient combustion air.

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3. Required excess air must be maintained at aminimum to reduce stack thermal loss.

4 . Flame propagation temperature must bemaintained.

Vaporization within the burner is generallyconfined to small domestic services, such as waterheating, space heating, and cooking, and to someindustrial processes. Burners for this purpose areusually of the pot type with natural or forced draft,gravity float-type feed control, and hand or electricignition. Kerosene, diesel oils, and commercial oils ofgrades Nos. 1 and 2 are suitable fuels because theyvaporize at relatively low temperatures.

If oil is to be vaporized in the combustion space inthe instant of time available, it must be broken up intomany small particles to expose as much surface aspossible to the heat. This atomization is done in threebasic ways:

1. By using steam or air under pressure to break theoil into droplets

2. By forcing oil under pressure through a suitablenozzle

3. By tearing an oil film into tiny drops bycentrifugal force

Primary combustion air is usually admitted to thefurnace through a casing surrounding the oil burner.The casing is spiral-vaned to impart a swirling motionto the air, opposite to the motion of the oil. Three typesof burners used for atomization are the steam- orair-atomizing burner, the mechanical-atomizingburner, and the rotary-cup burner.

Burners should be piped with a circulating fuelline, including cutout, bypass, pressure-relief valves,and strainer ahead of the burner. Burners should beaccessible and removable for cleaning, and the orificenozzle plates should be exchan geable to compensate

Steam-atomizing burners are simpler and lessexpensive than the air-atomizing type and are usuallyused for locomotive and small power plants. Theyhandle commercial grade fuel oils Nos. 4, 5, and 6 andrequire a steam pressure varying from 75 to 150 psi.The oil pressure needs to be enough to carry oil to theburner tip, usually from 10 to 15 psi. Burners using airas the atomizing medium are designed for three airpressure ranges: low pressure to 2 psi, mediumpressure to 25 psi, and high pressure to 100 psi.

Figure 4-54 shows a steam-atomizing burner of theexternal mixing type. In view (A), the oil reaches thetip through a central passage and whirls against asprayer plate to break up at right angles, view (B), tothe stream of steam. The atomizing stream surroundsthe oil chamber and receives a whirling motion fromvanes in its path. When air is used as the atomizingmedium in this burner, it should be at 10 psi for lightoils and 20 psi for heavy oils. In view (C), combustionair enters through a register; vanes or shutters areadjustable to give control of excess air.

Mechanical-Atomizing Burner

The burner is universally used except in domesticor low-pressure service. Good atomization resultswhen oil under high pressure (to 300 psi) passesthrough a small orifice and emerges as a conical mist.The orifice atomizing the fuel is often aided by aslotted disk that whirls the oil before it enters thenozzle.

for a wide range in load demand.

Steam-Atomizing and Air-Atomizing Burners

The burners consist of a properly formedjet-mixing nozzle to which oil and steam or air is piped.The conveying medium mixes with fine particles offuel passing through the nozzle, and the mixture isprojected into the furnace. Nozzles may be of theexternal or internal mixing type, designed to project aflame that is flat or circular and long or short. A burnershould be selected to give the form of flame that is mostsuitable for furnace conformation. Nozzles should be

Figure 4-55 shows a mechanical-atomizingburner. View (A) is a cross section of the burner; view(B) shows the central movable control rod that varies,through a regulating pin, the area of tangential slots inthe sprayer plate and the volume of oil passing throughthe orifice; view (C) shows a design with awide-capacity range, obtained by supplying oil to theburner tip at a constant rate in excess of demand. Theamount of oil burned varies with the load; the excess isreturned.

Horizontal Rotary-Cup Burner

The burner (fig. 4-56) atomizes fuel oil by tearingit into tiny drops. A conical or cylindrical cup rotates athigh speed (about 3,450 rpm), if motor driven. Oilmoving along this cup reaches the periphery wherecentrifugal force flings it into an airstream. It issuitable for small low-pressure boilers.

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positioned so there is no flame impingement on thefurnace walls and so combustion is completed beforethe i-lame contacts the boiler surfaces.

ORIFICE

Figure 4-54.—Steam-atomizing burner.

OIL-BURNER MAINTENANCE

Before attempting to start or to service oi I burners,see that you have the proper maintenance equipmentavailable. One item of equipment needed is a pressuregauge set. This should consist of a 150 psi pressuregauge, fittings to connect it, and a petcock forremoving the air from the oil line when starting theburner. You will need a full set of Allen setscrewwrenches for bypass plugs and for adjusting the nozzleholder and electrodes. Make sure you have a socketwrench of proper size for removing or replacing the

Figure 4-55.—Mechanical-atomizing burner.

nozzle, an open-end wrench as required for the nozzleholders, and a small thermostat wrench. This wrenchcomes packed with the thermostat and is used foradjusting the differential. A small screwdriver isrequired for adjusting pressure at the regulator andinstalling and servicing the thermostat. Anotherimportant item is pipe dope, and if available, use theoil-line type only. If in doubt, order a can of specialoil-pipe dope for use on all pipe threads requiring dope.A nozzle assortment should also be kept on hand. It ischeaper to make a change, time considered, than toclean the nozzle on the job. When a few nozzles haveaccumulated, clean them in the shop.

When installing a nozzle, use a socket wrench forturning the nozzle. Be sure the nozzle seat is clean.Screw it on until it reaches the bottom, then back it offand retighten it several times to make sure of a tight oilseal. Do not overtighten the nozzle or the brass threadswill become deformed, making it difficult to removethe nozzle.

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Figure 4-56.—Rotary-cup oil burner.

Clean the nozzles in the shop on a clean bench. Anozzle is a delicate device. Handle it with care. Usekerosene or safety solvent to cut the grease and gum;

use compressed air, if available, to blow the dirt out.Use goggles for eye protection when blowing dirt outwith compressed air. Never use a Jnetal needle to cleanthe opening; it will ruin the nozzle. Sharpen the end ofa match or use a nonmetallic bristle brush to clean theopening.

When you are checking the nozzle, adjustmentsmay have to be made in the distance of the nozzle fromthe tube end, the distance of the ignition points aheadof and above the nozzle, and the distance or gapbetween the ignition points. Figure 4-57 shows thesenozzles adjustments. The nozzle tip is set 5/8 inchapart, 1/8 inch ahead of the nozzle, and 1/2 inch abovethe nozzle center line. These settings are given only forthis particular illustration. Actual adjustments shouldalways be made according to the specific settings in themanufacturer's instruction manual. Always tightenelectrodes securely to ensure permanent adjustment.

When reinstalling either the pump or the motor,check the coupling to ensure there is no end pressure onthe pump shaft as evidenced by lack of end play. Ifthere is end pressure, the coupling should be loosened,moved closer to the pump, and re-tightened.

Troubleshooting

When oil burners are operated, operating problemswill occur. These problems can cause interruption ofservice, inefficiency, and damage to the equipment inthe system. To ensure proper operation and efficiency,you will need to be able to identify and correct thesedifficulties. A list of common difficulties and theirremedy are contained in appendix II, table L.

Flame Adjustment

After the burner has been visually adjusted andallowed to run about 30 minutes, reduce the stack draftuntil there is just enough over-fire draft in fireboxto keep the pressure from increasing under unfavorabledraft conditions. The draft regulator helps Jnaintain aconstant draft in the furnace regardless of outsideweather conditions. Adjust the draft by properlysetting the ad-juster. Too little draft is likely to causefirebox pressure, odors in the building, and possiblesmoke or smothering of the flame. Too much draftaccentuates the effect of a possible leak in the furnace,lowers the percentage of CO2 in the flue gas, and, inturn, reduces the overall efficiency of the unit. Afterthe burner flame and draft are properly adjusted, aflue-gas analysis should show a CO2 content ofapproximately 10 percent. If it does not, recheck theburner air adjustment and inspect for air leaks. For bestresults, the flame should be just large enough to heatthe building properly in cold weather.

Air supplied to the burner will then be theminimum for clean combustion. If the furnace is largeenough and the burner has been set for correct oil flowand minimum amount of air, stack temperature shouldnot exceed 600°F. Higher stack temperatures indicatethat the fire is too large or the furnace too small, or thatthere is too much excess air.

Test Equipment

It is almost impossible to set and adjust a burnerwithout instruments or test equipment. Properinstruments, in good working order, must be availablein the heating shop for use by personnel who servicethis equipment.

The draft gauge, usually of the pointer-indicatingtype, is used to determine suction in the smoke pipe orcombustion chamber. Suction is measured in inches ofwater. Carefully follow the instructions for operatingthe instrument.

The stack thermometer is used to indicate thetemperature of gases in the smoke pipe. Insert the

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Figure 4-57.—Setting of ignition points and nozzle.

thermometer halfway between the center and outsideof the smoke pipe and not more than 12 inches from thefurnace between the smoke pipe connection and thedraft regulator or barometric damper. Be careful toprevent the thermometer from being influenced bycold air taken in by the draft regulator.

The flue-gas analyzer is used to determine thepercentage of CO2 produced by combustion. The CO2

reading shows how much excess air is being used.Along with the stack temperature, it denotes theefficiency of the furnace. If, despite a good flamesetting, CO2 readings are low, examine the furnace forair leaks.

FUEL PUMP

Maintenance requirements include cleaning thestrainer, servicing the valve seat and needle valve, andadjusting the pressure regulator. Strainers must becleaned frequently to prevent the screen from cloggingand causing a shutdown. A good test for valve

operation consists of removing the nozzle line at thepump connection, starting and stopping the pump, andobserving whether the valve cuts off sharp and lean.When necessary, the valve is easily serviced byremoving the valve chamber cover, holding spring,washer, adjusting spring, cap, and bellows assembly.Then, by taking off the nut that is marked "Nozzle," thevalve, valve guide, and plug assembly can be removed.

Adjustment of the pressure regulator can be doneby replacing the vent plug with a pressure gauge,removing the cover screw, and using an Allen wrenchto turn the adjusting screw clockwise to increase thepressure or counterclockwise to decrease the pressure.

Burner failure or improper unit operation can becaused by various problems. Often the problem can bepinpointed by observing the type of failure and givingit some thought before attacking the problem. At othertimes, the cause can only be determined by a process ofelimination. Table M in appendix II lists specific oilpump troubleshooting procedures, while table K, alsoin appendix II, lists general oil burner troubleshooting

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procedures. Check the simplest and more obviousitems before progressing to the other checks.

Q15.

Q16.

Q17.

Q18.

Q19.

Q20.

Q21.

Q22.

Q23.

Q24.

With warm-air systems, the amount of heatreaching each room is determined by what twofactors?

What are the four airflow designs of gas-firedfurnaces?

What safety device on gas-fired heatingequipment reacts to the operation of the pilotflame?

What device shuts off the gas supply when thetemperature inside the heating unit becomesexcessive?

What are the three internal areas of an oil-firedfurnace?

What device is the nerve center of the heatingcontrol system?

What are the two most commonly used types ofthermostats?

A steam-atomizing burner requires a steampressure of what range for atomizing?

Electrode adjustments should always be set onburners according to what publication?

What instrument is used to determine the percentof CO2 produced by combustion?

DOMESTIC HOT-WATER HEATINGAND HOT-WATER BOILERS

Learning Objective: Identify types of hot-waterboilers, their fittings and accessories, and theiroperation.

The Navy uses both cast-iron and steel hot-waterboilers as sources of heat for domestic hot-watersystems in residences and other buildings. Smallhot-water heaters heat the hot water for domestic andfor limited industrial uses.

Hot-water boilers come in many shapes and sizes.They are constructed with a firebox for burning fueland have provisions for passing the hot gases over theheat-absorbing surfaces of the boiler. In most cases,baffles guide the gases over the most effective route.These baffles also retard the flow of the gases from thefurnace, so water can absorb as much of the heat aspossible. Both ends of the boiler have openings forcleaning the boiler tubes and for washing the interior of

the boiler. Since most boilers are stationary unitspermanently installed at the site, they have specifiedfittings and accessories for a specific heating job.Some boilers, however, called package boilers, arecomplete units, including fittings and accessories.These boilers are normally mounted on skids so theycan be moved to different sites.

This accounts for the term package boiler.Package boilers usually have the same accessories andcontrols as the comparable stationary type of hot-wateror steam boiler. Cast-iron boilers are seldom used aspackage boilers because of the danger of cracking theboiler sections during transportation.

Cast-iron hot-water boilers vary in size from smalldomestic units to moderately sized units capable ofdeveloping 31 through 98 horsepower. These boilers areusually constructed of several sections joined togetherby push nipples (round pieces of metal pipe tapered atboth ends). Pipes, known as header connections (fig.4-58) ordinarily connect the boiler sections.

Cast-iron boilers normally do not have bricksettings. Usually, the only bricks used with theseboilers are those that are sometimes used as a base forthe boilers. In most cases, the bases are made of castiron. Square sectional cast-iron boilers are similar tothe typical unit shown in figure 4-59. This boilerconsists of a front and rear section and a number ofintermediate sections, depending on the size of theboiler. The sections are connected on each side at thetop and bottom either by push nipples or by an outsideheader. When nipples are used, these sections are heldfirmly together by rods and nuts.

The boiler has a separate base that does not containwater and, therefore, requires a floor of fireproofconstruction. Boilers that have water in their bases arereferred to as wet-bottom boilers. These boilers arerelatively small water units that may be installed onfloors constructed of combustible materials. Thismethod of installation, however, is not desirable.

The construction of square sectional boilers isordinarily such that the sections can be taken throughregular-sized doors for assembly inside the boilerroom. This is a distinct advantage from the standpointof both installing new equipment and replacing brokensections. Cast-iron boilers resist the chemical action ofcorrosive agents much better than steel boilers.

The disadvantage of cast-iron hot-water heatingboilers is the danger of the sections cracking orbreaking when improperly handled or fired.

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Figure 4-58.—Cast-iron boiler castings.

Figure 4-59.—Cutaway view of a cast-iron boiler.

STEEL HOT-WATER BOILERS

Most steel hot-water boilers are constructed in twosections. One section consists of the water jackets,combustion chamber, and smoke passages. Thesecomponents are either welded or riveted together as aunit. The other section consists of the base and eitherthe grates or burner and is constructed according to thetype of fuel used (fig. 4-60).

by water lanes. It rests either on a cast-iron or a brickbase. The front part of the boiler rests on a pedestal. Adisadvantage of this one-piece steel boiler is that it isheavy and requires special equipment to lift it.

Another steel boiler is a horizontal unit of theportable type, having an internal firebox surrounded

INSTALLING BOILERS FORHOT-WATERHEATING

A boiler must have a good foundation. The topsurface of the foundation should be level to ensure

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Figure 4-60.—Typical hot-water boiler-light oil or gas fired.

proper alignment of the boiler sections, and thuseliminate strain on the boiler castings. The furnacefoundation should be poured separately from thefinished floor. It should be of sufficient width anddepth to support the boiler without any settling, and itshould extend 2 inches above the finished floor.Assembly procedures vary in detail for various boilers.However, manufacturers furnish detailed proceduresfor the assembly of their boilers. Usually, the plans forthe foundations can be procured from them.

OPERATION OF HOT-WATERBOILERS

Hot-water boilers, regardless of their design andtype, operate on the same basic principle. The fuelburns in the combustion chamber and produces heat.The resultant heat is radiated and conducted to thewater in the water jackets surrounding the combustionchambers and passes through the boiler tubes; heat isliberated by the flue gases and absorbed by the water

surrounding the tubes. The amount of heat transferredinto the water depends on the rate of heat conductionthrough the metal in the boiler tubes and the rate ofwater circulation in the boiler. For this reason, boilersare designed with baffles to hold the hot gases as longas possible. They give up maximum heat beforepassing into the chimney.

BOILER FITTINGS AND ACCESSORIES

All boilers have certain accessories for safety andease of operation. These accessories are pressure-reliefvalves, pressure gauges, water-level control valves,and automatic controls.

Pressure-Relief Valve

In a closed hot-water heating system, there isalways the possibility of building up a dangerouspressure. Consequently, a pressure-relief valve isinstalled to allow this pressure to escape. A typical

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pressure-relief valve is shown in figure 4-61. Thisvalve is usually on the top of the boiler. It contains aspring-loaded valve that unseats when the pressure inthe system increases to a predetermined value, therebyallowing water to escape until the pressure drops to asafe point. A valve of this type can be adjusted fordifferent pressure.

Pressure-relief valves may eventually corrode andstick if they are not forced to operate occasionally. It isa good practice, once each month, to increase thepressure to a point that operates the valve. When therelief pressure on the gauge exceeds the setting of thevalve, check the valve pressure with an accurate gaugeand adjust it to the required amount. However, do notexceed the maximum safe pressure of the boiler.

Pressure Gauge

The operator must know the water pressure in theboiler at all times. A gauge is connected to the top ofthe boiler. It shows the water pressure in the boiler andin the system in pounds per square inch. This gauge isusually a combination gauge that also indicates boilerwater temperature and altitude. The type shown infigure 4-62, however, indicates pressure only.

Little maintenance is required for this unit otherthan to clean the glass so the gauge can be read. Sometypes of pressure gauges are constructed so they can bere-calibrated. However, the proper equipment to dothis is not always available in the heating shop. Tocalibrate a pressure gauge properly, you must haveeither a master gauge set or a deadweight tester.

Water-Level Control Valve Figure 4-62.—A typical water pressure gauge.

Water is added to a hot-water heating system byeither a manually operated water valve or an automaticvalve, which is controlled by a float mechanism. Bothvalves are nearly identical to those used in thefree-water system of a steam boiler.

Airflow Switch

The airflow switch, or "sail switch" as it issometimes called, is in the stack, breeching, or the airinlet to the boiler. This switch shuts down the firingequipment in the event of an induced or forced draftfailure. To check the operation of this switch, yourestrict or shut off the draft. When you have done this,the switch should shut off the burning equipment.

Q25. It is a good practice to test the pressure reliefvalve by what method and what frequency?

Figure 4-61.—A typical pressure-relief valve.

Q26. What is the name sometime used to refer to an

airflow switch?

HOT-WATER HEATINGDISTRIBUTION SYSTEMS

Learning Objective: Identify types of hot-waterdistribution systems and components. Understand theoperation and maintenance of these systems.

In hot-water heating systems, the water is heated ata central source and circulated through pipes toradiators, convectors, or unit heaters. There are twogeneral types of low-temperature, hot-water heatingsystems. The first type is a gravity system in whichwater circulation depends upon the weight differencebetween the hot column of water leading to the

4-41

radiators and the relatively cooler, heavier column ofwater returning from the radiators. The second type isthe forced-circulation system in which water iscirculated by a power-driven pump.

GRAVITY SYSTEMS

The distribution systems and piping for hot-waterheating systems and for domestic hot-water supplysystems are simpler in design than those for steambecause there are no traps, drips, or reducing valves.Several items, such as supports, insulation, and somevalves and fittings, are the same for steam andhot-water distribution.

Gravity hot-water distribution systems operatebecause of the gravitational pull on the heavier coolwater, which sinks as the heated water becomes lighterand rises. At this point, some of the types of gravitysystems that are currently used are discussed.

Figure 4-63.—A one-pipe, open-tank gravity hot-waterdistribution system.One-Pipe, Open-Tank System

The one-pipe, open-tank gravity distributionsystem shown in figure 4-63 consists of a singledistribution pipe that carries the hot water to all of theconvectors or radiators and returns it to the boiler. Thissystem is easy to install and moderate in cost.

The water that flows into the radiators at the end ofthe system has a lower temperature than the waterentering the first radiators. A system of this type shouldbe designed so the water reaching the last convector isnot too much cooler than the water reaching the firstconvector. Because of this progressive temperaturedrop in the distribution system, convector radiatorsshould be installed at the end of the system to equalizethe amount of heat radiation per radiator. It is difficultto get enough circulation by gravity to give the systemsmall convector temperature drops; consequently, wedo not recommend the one-pipe, open-tank gravitysystem.

Two-Pipe, Open-Tank SystemFigure 4-64.—A two-pipe, open-tank gravity hot-water

distribution system.Many hot-water gravity distribution systems aretwo-pipe, open-tank systems, as shown in figure 4-64. are usually made into a gravity return, which pitchesThis heating system is constructed with separate water downward to the return opening in the heating boiler.mains for supplying hot water and returning cold The water temperature is practically the same in allwater. The radiators are connected in parallel between radiators, except for the allowance to be made for thethe two mains. In the two-pipe, open-tank gravity temperature drop in the distribution supply mainssystem, the distributing supply mains are either in the occurring between the boiler and the end of the circuit.basement with upfeed to the radiators or in the attic. Water temperatures are the lowest at the end of theWhen the system is in the attic, it has overhead circuit. The amount of temperature drop between thedownfeed supply risers. The return mains are in the beginning and the end of the line depends upon thebasement. Return connections for the two-pipe system length of the main and upon the heating load.

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A tank with its vent open to the atmosphere isinstalled in the system above the highest radiator forwater expansion. The water level in the expansion tankrises and falls, as the system is heated and cooled, andthe system is full of water and free from air at all times.In the open-tank gravity hot-water heating system, theexpansion tank is installed on a riser directly above theboiler, so the air liberated from the boiler water entersthe tank and is not retained in the system.

One-Pipe, Closed-Tank System

A one-pipe, closed-tank gravity hot-waterdistribution system, as shown in tigure 4-65, is similarto the one-pipe, open-tank gravity hot-water heatingsystem, except the expansion tank is a pneumaticcompression tank not open to the atmosphere. Whenthe water in a closed-tank system is heated, it. expandsinto the pneumatic compression tank. This actionpermits system operation at a much higher watertemperature, without boiling, than the temperature inthe one-pipe, open-tank gravity system. This alsoresults in higher heat emission from the radiators.

A gravity open-tank system with an average boilerwater temperature of 170°F has a radiator emissionrate of 150 Btu psi, whereas a gravity closed-tanksystem with an average boiler water temperature of190°F has a radiator emission of 180 Btu per squarefoot (psf). Higher boiler water temperatures permithigher temperature drops through the radiators;consequently, smaller pipe sizes can be used. Theclosed pneumatic compression system requires a reliefvalve, usually set for the relief of water pressure over30 psi, depending upon the height of the building. Apressure-regulating valve automatically maintains thesystem full of water. Installation of the radiators andpiping for an equivalent two-pipe, closed-tank gravityupfeed or overhead downfeed system is the same asthat for the open system, except the sizes of both thepipe and the radiators are uniform and can be smaller.The open-tank system may have a reversed return mainthat does not go directly back to the boiler.

It doubles back from the last radiator and parallelsthe supply main back to the boiler entrance. Thereversed return system allows equal length of heatingcircuits for al I radiators. Friction and temperaturelosses for all radiators are nearly equal. In most cases,the reversed return system involves no more pipingthan other piping arrangements. With the correct sizeof piping and radiator supply tappings, the reversedreturn system provides even heat and circulation to allradiators, even those near the end of the circuit.

Figure 4-65.—.A typical one-pipe, closed-tank distribution

system.

Expansion in a Gravity Hot-WaterDistribution System

In the gravity and forced-circulation systems, openand closed expansion tanks allow the water in thedistribution system to expand as the temperature rises.An open tank must be mounted at the highest point inthe system; a closed tank can be located at any point. Ifthe air cushion leaks out of the closed expansion tank,it fills with water. At times, you must recharge the tankby draining part of the water out of the tank andallowing air to -fill the space.

In the open system, an expansion tank open to theatmosphere allows the system to expand. The opensystem is normally designed to operate at themaximum boiler temperature of 180°F. This gives anaverage radiator temperature of 170°F or a radiatoroutput of 150 Btu psf. The closed system, in which theexpansion takes place against a cushion of air in thetank closed against the atmosphere, can be operated attemperatures above 212°F because the pressure builtup in the system prevents the water from boiling.Radiator temperatures then become equal to those oflow-pressure steam systems.

When a hot-water system is first filled with water,it is normally necessary to bleed the air out of thesystem at the same time. You can remove the air byopening an air vent on a radiator or by breaking a unionnear the end of the line. The temperature of the waterdistributed is from 150°F to 250°F. The highertemperatures are used with the forced-circulationsystems.

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FORCED-CIRCULATION SYSTEMS

Forced-circulation hot-water distribution systemshave several advantages. They permit the use ofsmaller pipe sizes and allow the installation ofradiators at the same level as the boiler, or below,without impairing water circulation. By using acirculation pump, a positive flow of water is assuredthroughout the system. In larger installations,especially where more than one building is served,forced circulation is almost invariably used. With thedevelopment of a circulation pump of moderate cost,the forced-circulation system is being used more insmall heating installations.

Even as in gravity systems, forced-circulationsystems can consist of a one-pipe or a two-pipe, upfeedor downfeed, and can be equipped with a direct or areversed return. Although these systems usually haveclosed expansion tanks, they may have open tanks.

One-Pipe, Closed-Tank System

The general arrangement of a one-pipe,closed-tank, forced-circulation system shown in figure4-66 is similar to the one-pipe gravity system, but withthe addition of a circulating pump.

The circulation to individual radiators is improvedby special supply and return connecting tees. Thesetees, by an ejecting action on the distribution supplymain and an ejecting action on the return, combine touse a portion of the velocity head in the main toincrease circulation through the radiators. Tees of thistype also aid stratification of hot and cold water withinthe distributing main. They are designed to take off thehot-test water from the top of the main and to depositthe colder water on the bottom of the main.

Figure 4-67.—A two-pipe, closed-tank, forced-circulations y s t e m .

Two-Pipe, Closed-Tank System

The general arrangement of the piping andradiators for the two-pipe, forced-circulationdistribution system is the same as that for the two-pipegravity system. The relative locations of thecompression tank relief valve and the circulating pumpare shown in figure 4-67.

DISTRIBUTION SYSTEMCOMPONENTS

The component parts of a hot-water distributionsystem are similar to that of steam heating systems asdescribed in chapter 3. They include the following:pipelines, radiators, convectors, unit heaters,

Figure 4-66.—A one-pipe, closed-tank distribution system witha circulating pump.

circulating pumps, reducing valves, flow-controlvalves, and special tlow fittings.

Pipelines

The piping system constitutes the closedpassageway for the delivery of hot water to the pointswhere it is used. Pipelines are made of lengths of pipefastened by screwed, flanged, or welded joints. Theyhave valves and fittings, such as tees, unions, andelbows, according to the needs of the installation.Pipelines are supported by hangers and fastened byanchors. Expansion joints or loops allow forexpansion.

Mains and branches of the pipeline should bepitched so the air in the system can be dischargedthrough open expansion tanks, radiators, and relief

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valves. The pitch is generally not less than 1 inch forevery 10 feet. The piping arrangements for a newsystem should provide for draining the entire system.

Radiators

The radiator transfers heat from the hot water inthe pipes of a hot-water heating system into thesurrounding air in a room. A radiator is usually of twotypes. Cast-iron radiators are constructed andassembled in sections, as shown in figure 4-68, view A.Damaged radiator sections can be replaced withoutreplacing the entire radiator assembly. Fin-tuberadiators (fig. 4-68, view B) are constructed of steelpipe and fins, which are welded to the pipe.

Radiators usually rest on the floor. However, theycan be either mounted on a wall or hung from theceiling. The location of a radiator depends on the typeof room to be heated and its location with respect to thelocation of the boiler. For instance, in a forced-circulation hot-water distribution system, the radiatorsmay be on the same level with the boiler.

Convectors

Convectors are supported on the wall much in thesame way as a pipe. The convectors consist of afin-tube radiator mounted in a metal cabinet andtransfer heat much in the same way, although adamaged section must be welded or the entireconvector must be replaced (fig. 4-68, view C).

Hot-water heating system radiators and highpoints in the distribution lines must have some type ofvent that releases air from the system. Air trapped inthe system prevents the circulation of water. For thispurpose, a manually operated key-type air vent, asshown in figure 4-69, can be used.

Manually operated key-type air vents can bereplaced by automatic air vents. One type of automaticair vent is shown in figure 4-70. It automatically allowsthe air that forms in the system to escape. When airvents fail, replace them.

Radiators also have shutoff valves, as shown infigure 4-71, which reduce or stop the flow of hot waterthrough a radiator. They are installed in the piping nextto the inlet side of the radiator. Occasionally, you musttighten the packing nut on these valves to prevent thewater from leaking around the valve stem.

C. Convector.Figure 4-68.—Radiators: A. Cast iron; B. Fin tube;

Figure 4-69.—A manually operated key-type air vent.

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Figure 4-70.—One type of automatic air vent.

Figure 4-71.—A typical radiator shutoff valve.

Unit Heaters

Unit heaters are the same as those used in warm-airheating, except hot water is used vice coils for theheating medium. The heater consists of a heating coilsupplied with hot water. The coil is usually of thefinned type, and an electric fan circulates air over it. Aunit heater installed in a distribution main is shown infigure 4-72.

Servicing unit heaters includes a monthlyinspection. Each month, check for water leaks,cleanliness of the finned coils, and the operation of the

Figure 4-72.—A typical hot-water unit heater installation.

fan motor. Other accessories which you also shouldinspect are traps, air vents, fan blades, and valves.Make any needed repairs. Lubricate the electric fanmonthly.

Circulating Pumps

A forced hot-water heating system has awater-circulating pump in the return line near theboiler. This pump ensures the positive flow of waterregardless of the height of the system or the drop in thewater temperature. Greater velocities of water flow areobtainable with forced circulation than with gravitycirculation.

Circulating pumps are free of valves and floatcontrol elements. They are operated under asufficiently high water inlet temperature to eliminatethe difficulties caused by vapor binding. The pumpsare usually operated by electric motors.

up so tight that they score the shaft.

Reducing Valves

A reducing valve is normally installed in thecold-water line going to the boiler. It automatically

During maintenance servicing, check the pumpcarefully for proper rotation, and lubricate the electricmotor and pump according to the manufacturer'sinstructions. Also, periodically clean the pump ofsand, rust, and other foreign matter that has collected inthe pump casing. Be sure the pump rotates freely andthe shaft packing glands, if there are any, are not drawn

keeps the closed system supplied with water at apredetermined safe system pressure. These valves are

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usually set at the factory, but you may adjust them inthe shop to a desired pressure. You should install thisvalve at approximately the same level as the top of theboiler.

Flow-Control Valves

Forced hot-water circulating systems use theflow-control valve shown in figure 4-73. It is normallyinstalled in the distribution main. This valve preventsgravitational flow of water through the system. Thevalve does not offer any serious resistance to the flowof water when the circulating pump is in operation.However, when the pump is not operating, the smallgravitational head of water cannot open the valve.Each week you should check the flow-control valve forproper operational down-free movement. Examine thevalve for water leaks and repair it when necessary.

Special Flow Fittings

Various types of special tees designed to deflectmain-line water into the radiator branches are used inone-pipe and two-pipe forced-circulation systems.These fittings are designed and calibrated to the size ofthe radiator and system-operating temperature.Fittings of this type are required with one-pipe,forced-flow systems, and they do equally well forradiators above and below the distribution mains.

MAINTAINING AND TROUBLESHOOTINGHOT-WATER HEATING SYSTEMS

Hot-water heating systems require l i t t lemaintenance other than periodic checks to makecertain that all air is out of the system and all radiatorsare full of water. The circulating pumps should be oiledregularly according to the manufacturer's instructions,and the pressure-relief valves should be checkedperiodically.

Figure 4-73.—One type of flow-control valve.

Some of the common discrepancies encounteredwhen troubleshooting hot-water heating systems arecontained in appendix II, table O.

Operator maintenance on the electrically drivenfeed pump consists mostly of cleaning the pump andmotor. However, the pump motor is lubricatedaccording to the manufacturer's specifications.Remember that not using enough lubricant can resultin the bearings running dry or seizing on the motorshaft. But, too much lubricant causes the motor tobecome dirty, and it can result in the motor windingsbecoming saturated with oil and burning out.

When a water leak develops around the pumpshaft, tighten the packing-gland nuts or repack thestuffing box as necessary. The strainer, installedbetween the pump and the condensate receiver, shouldbe kept clean to avoid any restriction of the flow ofwater to the pump.

The maintenance of feed-water heaters andeconomizers normally includes removing solid matterthat accumulates in the unit; stopping steam and waterleaks; and repairing inoperative traps, floats, valves,pumps, and other such associated equipment.

Q27. What is the main reason to install a two-pipe,open tank, gravity distribution system over aone-pipe, open-tank, gravity distributionsystem?

Q28. The operations of what component of theone-pipe, closed-tank distribution system resultsin higher heat emission from the radiators?

Q29. Air vents release trapped air in the system. If the airis not released, how would this affect the system?

HIGH-TEMPERATURE HOT-WATERSYSTEMS

Learning Objective: Recognize different types ofhigh-temperature hot-water systems, their components,and understand their application and installation.

High-temperature hot-water (HTHW) systemsoperate at high pressure to maintain water temperaturethat exceeds the normal boiling temperature of 212°F(at atmospheric pressure) used in other types of heatingsystems.

High-temperature hot-water systems consist ofstandard and heavy-duty equipment, including boilers(sometimes referred to as generators), expansiondrums, system circulator pumps, distribution piping,and heat-consuming equipment.

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High-temperature hot-water systems have the hotwater pumped from the generator throughout thedistribution system. The circulator pumps are largeenough to deliver the water at sufficient pressure toovercome any drop in the distribution system and theheat-consuming equipment. The major advantages ofthe HTHW heating system are makeup requirements,minimum maintenance, high thermal efficiency, andsafe, easy operation and control.

The HTHW system is a closed system, so the onlywater waste is the normal leakage at the pump andvalve packing glands. Consequently, little water isconsumed during system operation. This means only asmall amount of makeup water is used, practicallye l imina t ing bo i l e r b lowdowns . The c losedre-circulating system operates at high thermalefficiency. All of the heat not used by heat-consumingdevices in the system or lost through pipe radiation isreturned to the boiler plant. Because few boilerblowdowns are required, the heat loss fromblowdowns is kept to a minimum.

TYPES OF HTHW SYSTEMS

The high-temperature range for most military andfederal heating plants is 350°F to 450°F which

corresponds to saturated pressures of 135 psi to 425psi. However, some types of plants operate at higherpressures and the re fo re have h igher wa te rtemperatures. The installation of HTHW plants thatoperate at temperatures above 400°F must be approvedby the Naval Facilities Engineering Command. Costsusually determine the maximum water temperatureused, because the types of HTHW systems using thehigher pressures require more expensive piping,valves, fittings, and heat exchangers.

The degree of complexity of HTHW systemsvaries according to the size, type, and heat loadrequirement of the installation. Since methods used tomaintain pressure and to assure uniform flow ratesdepend upon the amount of heat load, they affect thecomplexity of the heating system. There are twomethods of circulating the HTHW through thesystem—the one-pump system and the two-pumpsystem.

The one-pump system uses only one pump tocirculate the hot water throughout the system, whichincludes the generator. The two-pump system uses onepump to circulate the water through the distributionsystem, and a second pump to circulate the waterthrough the generator for positive circulation. Figure

4-74 shows some typical pumps that are used forcirculation in the HTHW system. Note that the pumpsare of the centrifugal type. Each pump shown is used tocirculate the water to different areas in the distributionsystems.

There are two common ways of heating the waterin the HTHW system—one way is to use hot-waterboilers or generators and the other way is to use thecascade or direct contact heater. The water in theHTHW generator is heated as low-temperature hotwater is heated. In the cascade heater, however, thewater is forced through spray nozzles and comes intodirect contact with the steam. The steam condensesinto the circulating water. A typical spray nozzle headis shown in figure 4-75. The spray nozzles are installedin a combination cascade heater expansion drum. Atypical cascade heater expansion drum installation isshown in figure 4-76. In the paragraphs that follow,some ways of pressurizing the HTHW system arediscussed.

PRESSURIZING THE HTHW SYSTEM

Since water volume varies with changes intemperature, the extra water must be taken care ofwhen the water is heated. It is desirable to operate withthe water above the boiling temperature of 212°F;therefore, the pressure in the system must bemaintained equal to, or greater than, the correspondingsaturation (steam or vaporization) temperature. Anexpansion tank is required because the water, which isnot compressible to a smaller volume, expands when itis heated. Also, the pressurization prevents theformation of saturated steam or vaporization when thewater temperature is raised. There are two basicdesigns used for pressurizing HTHW systems—first,the saturated steam cushion, and second, themechanical gas cushion. Although both des igns have avariety of modifications, their characteristics are stilltypical of the basic pressurized system design.

Saturated Steam Cushion

Pressurizing the heating system with steam in theexpansion tank is a natural method. Firing the HTHWgenera to r to ma in ta in the sys tem pressu recorresponding to the required saturation (steam orvaporization) temperature pressurizes the system.Excess heat is generated to offset the radiant heat lossfrom the expansion tank. All of the HTHW in thesteam-pressurized system flows through the expansiontank and thereby maintains the saturation (steam orvaporization) temperature there.

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Figure 4-74.—Typical high-temperature hot-water circulation pumps.

Figure 4-75.—A typical cascade heater spray nozzle head.

The steam in the space in the expansion tankprovides the pressure or cushion for the system. Thepressure maintained is that of the saturated steam. Thewater in the lower portion of the tank will be

approximately saturation (steam or vaporization)

temperature corresponding to this pressure. The water

to be used in the HTHW heating system is drawn from

the lower part of the expansion tank, mixed with the

system return water, and circulated throughout the

system. The mixing is necessary to prevent cavitation

(steam flashing) at the pump suction.

Here are some conditions that are typical of the

saturated-steam cushion design. The expansion tank,

either integral or separate, is a part of the HTHW

system. The entire amount of hot water flowing in the

heating system passes through the expansion tank and

exposes the tank to maximum system heat and any

form of contamination which, in turn, subjects the

expansion tank to thermal stresses and corrosion.

There are explosion hazards typical of a steam boiler in

the system, and good water-level control is important

in maintaining proper operating conditions. Load

variations, causing supply pressure changes, create

flashing of saturated liquid in the system and produce

water hammer.

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Mechanical Gas Cushion Operation

Figure 4-76.—A combination cascade heater expansion drum installation.

The expansion tank contains the mechanical-gascushion and is connected to the HTHW system returnline just ahead of the circulating pump suctionconnection. The tank contains an inert gas (usuallynitrogen) and is the source of pressure in this method.When the system has been pressurized by the nitrogen,pressure in excess of saturation must be maintained;that is, the water temperature throughout the systemmust always be less than its saturation temperature. Inthe nitrogen-pressurized system, the expansion tank isinstalled in the system as a standpipe arrangement sothe water does not flow through it. The water in thelower part of this tank is stagnant, except for thechanges caused by expansion and contraction broughton by load fluctuations. If you assume the water isvirtually incompressible, the tank provides the spaceavailable for these changes in the water volume of thesystem.

Here are some characteristics that are typical ofthis design. The expansion tank is independent of thegenerator and remains cool. Corrosion is practicallyeliminated because the heating system is flooded withthe exception of the nitrogen space in the expansion(cushion) tank. When properly designed, the system issealed with its fixed charge of water and nitrogen.However, this design does not contain a steam drum orany steam spaces that permit the accumulation ofsteam. The generator tubes are the weakest link in thisentire system. An explosion caused by the dissociationof hydrogen and oxygen cannot occur. The formationof steam cools the otherwise red-hot metal surfaces.Hot-water conditions do not allow the flashing ofsteam.

To ensure normal operation, fill the system withtreated water taken from the water softener. To preventoxygen corrosion, add the chemicals for treating thewater to furnish 20 to 40 parts of sodium sulfite permillion parts (ppm) of water. You thereby maintain apH value of 9.3 to 9.9. While the water is circulating inthe generator and in the system, you should fire theboiler at about 25 percent of its rated capacity to bringthe system up to normal operating temperature. Youshou ld a l low the expans ion d rum ven t insteam-pressurized systems to blow for about 1 hour torid the system of all oxygen and other non-condensablegases.

The start-up and firing of HTHW boilers orgenerators arc done in much the same manner as fordomestic hot water and steam boilers, depending uponthe type of fuel-burning equipment used. The specificstart-up and operating procedures vary with differentinstallations. Therefore, this information is furnishedby your local supervisor and the manufacturer of theequipment.

Coal, oil, and gas are the types of fuels normallyused to fire the boilers of HTHW systems. The specifictype of fuel used depends upon the type of firingequipment installed in the plant. Each type of fuelrequires designated inspections be made -and certainprecautions be taken to eliminate fire and safetyhazards.

When you are transferring fuel oil from one tank toanother, be sure both tanks are grounded. Checks mustthen be made to ensure excessive oil pressures are notgenerated in the tanks by the expansion of the fuel.Although natural gas is not normally stored on a baseashore, liquid petroleum (LP) gas is often stored nearthe heating plant. You should check the areas where

4-50

this gas is stored often to ensure there is no leakage.

Liquid petroleum gas is heavier than air, settles in low

areas, and creates explosive hazards. When checking

for gas leaks, use a standard soap solution.

The possibilities of line failure are remote whenthe construction recommended above is used. Thesystem piping material is subjected to a minimumfactory test of 700 psi. The generator tubes aresubjected to an ASME test of 900 psi. All valves and

Because of the large heat storage capacity of accessories are rated at working pressures of 540 to

HTHW systems, the load demand change for the boiler

is slow and smooth. This characteristic provides for

improved and safer operation than that provided by the

saturated-steam cushion.

1,075 psi at 400°F. The weakest link in the pipingnetwork lies within the generator tubing. The worstlikely failure is the loss of tubes, and therefore thegenerator. The safety of the piping system ismaintained over the life of the installation because ofthe absence of corrosion in the hot-water heatingsystems due to boiler water treatment.PIPING SYSTEM INSTALLATION

All piping in an HTHW system should be welded.

No screwed joints should be permitted, and flanges

should be allowed only where necessary, such as at

expansion joints, pumps, and generator connections.

Only schedule 40 black steel piping or better is used for

HTHW systems. Upon completion, the entire heating

Q30. What is the high-temperature range for mostmilitary and federal heating plants?

Q31. What are the two common ways of heating waterin HTHW systems?

Q32. To prevent oxygen corrosion in an HTHWsystem, treat the water with chemicals toproduce whatppm of sodium sulfite?

system is subjected to a test of 450 psi that lasts for not Q33. Should all piping in an HTHW system beless than 24 hours. welded? True/False

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CHAPTER 5

GALLEY AND LAUNDRY EQUIPMENT

Learning Objective: Recall the procedures required for the maintenance of galleyequipment and the procedures for installing, maintaining, troubleshooting, andrepairing laundry equipment.

Most stateside galleys and laundries, as well asmany overseas, are now operated and maintainedthrough civilian contracts. But there are stillinstallations maintained by overseas Public WorksDepartments, which require military personnel. Thischapter presents information on the maintenance ofcommon types of galley and laundry equipment.Because of the contracted galley and laundry facilitiesand differences in types of equipment you are expectedto maintain, only general information is presented inthis chapter. Remember you should study themanufacturer’s manual that comes with a new piece ofequipment before you attempt to install or maintain it.

GALLEY EQUIPMENT

Learning Objective: Identify different types of galleyequipment and recall the procedures required for theirmaintenance.

Galley equipment must be maintained in a safe,sanitary, and economical way. Utilitiesmen not onlyinstall and maintain the equipment but they alsosupervise others who perform work on the equipment.It is always a good practice to post operatinginstructions near the various pieces of equipment in agalley or a bakeshop. This action should reduce thenumber of operators who abuse the machines. This isparticularly important where messmen and strikers areworking. As a further safeguard, you should conductperiodic preventive maintenance inspections asrequired for the equipment at your location or as calledfor in the manufacturer's instructions. After theinspection, you should attach a tag to each piece ofequipment that contains pertinent information, such asthe date, the type of inspection, and by whom theinspection was made.

The maintenance of food preparation equipmentmay vary. In peacetime, most types of equipment arelocated in a permanent galley or bakeshop. While

deployed to an island or an overseas shore station, aconstruction battalion might have either a permanentgalley or a semi-permanent galley, using either fieldunits or fixed types of equipment.

Whatever the need or the location, your mostimportant duty is to keep all items of equipment in acondition of readiness to ensure safe, sanitary, andexcellent operation at all times. The medicaldepartment is responsible for conducting sanitaryinspections, and the supply department is responsiblefor preparing food and keeping food-handlingequipment and spaces clean. Coordinate yourmaintenance efforts in conjunction with thesedepartments. Once any maintenance or repair iscompleted on equipment, ensure that it is inspectedbefore it is put back into service for food preparation.Field galley range is briefly covered in this chapter.For more information on its operation, refer to chapter2 of Utilitiesman Basic, volume 1, NAVEDTRA11019.

STEAM KETTLES

Steam kettles, more commonly called "coppers,"are either direct-steam or self-contained type units.Self-contained units generate their own steam thougheither a gas burner or electrical connections.Direct-steam coppers are supplied with steam from acentral boiler located in the galley. Becaused i rec t - s t eam un i t s a re more common thanself-contained units, this chapter mainly coversdirect-steam coppers.

Maintenance requirements for coppers are smallwhen compared to other pieces of galley equipment.You should consider this fact when you are developinga preventive maintenance inspection schedule. Themaintenance schedule for coppers requires monthlyinspections and an annual preventive maintenanceinspection. When conducting monthly or annual

5-1

inspections, talk to galley personnel about theoperation of the coppers. These personnel can giveyou information that will assist you in diagnosingpossible operational or maintenance problems. A fewfactors for inspecting direct-steam coppers (fig. 5-1)are as follows:

inspection and maintenance of coppers are provided intable P of appendix II.

STEAM CHESTS

MONTHLY inspection:

Check the faucets, valves, and piping for leaks.

Check the steam pressure-reducing valve toensure it is in good condition and functionsproperly.

Lubricate the hinges of the cover with mineraloil.

Steam chests are used to cook food through asteaming process. The escape of steam from a steamchest harms the food being prepared and also poses asafety hazard to personnel. To ensure steam-tightoperation, ensure the door latches, hinges, and gasketsare kept close fitting. A physical preventivemaintenance inspection of the steam chests (fig. 5-2)should be made each week.

ANNUAL inspection:

The weekly inspection should ensure thefollowing:

Check the copper for leaks, cracks, and dents.

Examine the cover, hinges, and latch for warpand alignment.

The compartment drains are free of obstructions.

The door hinges, locking devices, and shelfdrawbars work well.

Check the steam and condensate piping, valves,and traps for leaks and obstructions.

The pressure setting of the gauge pressure iscorrect.

Remove the safety valves and remove any rustand corrosion using Navy-approved solvents.Then, lubricate and calibrate the valves beforereplacing them.

Other than visual inspections, each individualpiece of galley equipment requires its own type of

When a plunger type of valve is used with thelocking device, the plunger must be adjusted so thevalve is fully depressed when the door is closed. Thisaction allows a full measure of steam to enter thecompartment. When the door is opened, the valvemust function to stop the steam supply completely. Toensure a tight fit of the doors, replace hinge pins andbushings when they show too much wear. Somefull-floating doors are adjustable by means ofhexagon-head bolts extending through the door neareach corner. When door gaskets must be replaced, youmust remove the door from the unit because this makesit easier to remove the worn gasket and to clean thechannel. Failure to complete these actions can providea path for steam leakage. Apply gasket cement, andthen force the new gasket into the channel at thecorners, working it in toward the center of the sides andends. You are now ready to hang the door; but first,place paper along the edge of the door opening toprevent excess cement from adhering to the matingsurfaces when the door is closed. Any surplus cementcan be cleaned off after it has hardened. When the doorhas hexagon-head bolts, adjust them so the closed doortouches the steamer evenly without binding at thecorners. Unless you have a good fit, the gasket will cutby the corners of the door and steam will escape. Forinspection and preventive maintenance of the steamservice and condensate system, include those itemsthat apply in table P of appendix II.

preventive maintenance. Recommended schedules for

Figure 5-1.—A pedestal and a trunnion or tilt type ofdirect-steam coppers.

5-2

Figure 5-2.—Direct-connected steam chests.

STEAM TABLES

Steam tables are used to keep food hot duringserving by use of steam and hot water. Steam tables(fig. 5-3) should be carefully inspected monthly andyearly.

The MONTHLY inspection should include thefollowing:

Check the water compartment, steam coil,valves, and piping for leaks and corrosion.

Check the steam pressure on the gauge, keepingin mind that the PRESSURE SHOULD NOTEXCEED MAXIMUM PRESSURE SHOWNON THE NAMEPLATE.

Check and calibrate the temperature control, ifneeded.

The ANNUAL inspection should include thefollowing:

Descale the water compartment, examine the topand frame for scale, and check the level of thesteam tabletop.

Figure 5-3.—Schematic drawing of a steam table.

5-3

Remove the rust and corrosion within the watercompartment, as necessary, with solvent, andpaint the bare spots with heat-resistantaluminum paint.

Check the thermostat with a mercurythermometer. The thermostat must be accurateto within either plus or minus 5°F.

NOTE

Use table P of appendix II to check otheritems that apply to this equipment.

DISHWASHERS

From time to time, you may be called upon toadjust dishwashing machines that have becomedefective (figs. 5-4 and 5-5). Some of the most

common difficulties, the usual reasons for theiroccurrence, and possible remedies for them are listedin table Q of appendix II.

Now and then, descaling deposits from within themachine, the piping, and the pumps will be required.You can fill the tank halfway with hot water, add anapproved cleaning solution, fill the tanks tooverflowing, and then operate the machine for 30minutes at high temperature with trays, spray arms,and curtains in place. Next, drain the tanks and fillthem with hot water and run the machine for 5 minutes.This rinsing action should be repeated several times tomake sure all of the cleaning solution is removed fromthe unit.

Dishwashing machines and accessories should belubricated according to the manufacturer’sinstructions. This is especially true in the selection of

Figure 5-4.—A semiautomatic single-tank dishwasher.

5-4

Figure 5-5.—A cutaway view of a double-tank automatic dishwasher.

grades and viscosities of the oil used, the levels atwhich the oil is to be maintained, and the places to beoiled. All damaged or missing lubrication fittingsshould be replaced. The grease cups on the drive end,connecting rod, and the rinse lever should be turnedonce each quarter and be refilled when empty. Also,the revolving wash arms and valve stems should have afew drops of light oil applied to them about once eachquarter.

CAUTION

Be sure to turn off the power beforelubricating the equipment.

Because of limited space, this chapter does notattempt to provide all the necessary details concerningthe parts and accessories of dishwashing machines.Study the manufacturer’s manual for the type andmake of machine concerned. Some of the machineparts and accessories of the dishwasher that should bemaintained and serviced regularly are as follows:

Repair or replace the torn or worn curtains.

Straighten the warped pans so they stay flat inthe machine.

Replace the packing with new material of thesame type and size. Do not overpack the packinggland because this condition causes binding ofthe shaft.

Replace the broken or damaged thermometers.Check the accuracy of the thermometer bymeasuring the water temperature with ahigh-grade thermometer and comparing resultswith a thermostat setting. The thermostat shouldbe set for a wash water temperature between138°F to 145°F and rinse water for a temperatureof 180°F or above.

Defective conveyors should be properlyadjusted or replaced. Check the nylon coveringof steel parts and replace the coverings whenthey are worn or torn.

The inspection doors of wash and rinsecompartments should be kept tight at all times.

Straighten or replace bent or loose doors.

Check the chains and pulleys of counterbalanceddoors. Apply oil regularly to moving parts.

Check the dish racks for bent or warped surfacesand replace broken parts.

5-5

Inspect the utility fittings, such as steam coils,traps, heating elements, gas burners, and allthermostats. Follow the manufacturer's repairinstructions. Usually, you have to detach thesecomponent parts and take them to themaintenance shop for repairs.

Frequently check the ventilating hoods (ifinstalled), the hood fans, and fan accessories,such as baffles, clampers, vanes, access doors,louvers, registers, protective grilles, and bird orinsect screens for corrosion and rust.

Check the ventilating hood fans for grease andother impurities that should be scraped off with aknife. Tighten any items that have becomeloosened by vibration.

Remove the rust from dishwashers with solventsand paint over corroded areas with two coats ofrust-resistant paint. In selecting a solvent, usethe air-inhibited sulfamic acid type according tothe manufacturer's instructions.

CAUTION

Never use steel wool for cleaning interiorsurfaces of dishwashers because smallpart icles may contact dishes andeventually become embedded in food.

With regular inspection and lubrication, withrepairs and adjustments made as necessary, and withstrict observance of the manufacturer’s operatinginstructions, these machines will last along time. Toensure they receive the required attention, set up aregular schedule of inspection. Monthly and annualinspections may be satisfactory in many cases.

MONTHLY inspect ion and maintenance shouldinclude the following:

Check the lubrication of bearings, gearboxes,chains, and sprockets; lubricants should beadded, if required.

Check the drive V-belt tension and alignment,flexible couplings, chains, and sprockets.

Check the electrical components for properfunctioning and safety features, including propergrounding.

Ensure the machine and the tables are level;check for misalignment of parts, loose parts andleaks, and unusual noises.

Check the piping system for faults.

During ANNUAL inspections, give carefulattention to the following:

Check the frames for adequacy of support;tightness of casings, seams, joints, andcounterweights; evidence of corrosion;watertightness of doors, hinges, and gaskets; andcorrectness of clearance and alignment.

Check the pumps and impellers for corrosion orextreme wear of parts. Disassemble them, cleanall parts thoroughly, and repair or replace badlyworn parts. Reassemble and adjust.

Lubricate all parts requiring lubrication.

Be sure to tag the dishwasher, stating the date ofthe current inspection, repairs made, and the dateof the next inspection.

RANGES

Observing a schedule of monthly and annualinspections ensures the safe and efficient operation of arange, including the oven, broiler, griddle, and so on.Some of the major items that should be covered as partof the MONTHLY inspection are as follows:

Check the pipe for leaks.

Clean and lubricate the motors.

Check the burner flame. Remember, the burnershould give off a blue flame when the air-oilmixture is correct. A flue-gas analysis should beperformed to find the proper fuel-air mixture.

Check the equipment for alignment and fit ofdoors, for sliding action of racks, and forlevelness.

The ANNUAL inspection of oil- and gas-firedequipment should include the following:

Check on all the parts for damage, corrosion, andlack of paint. Remove the rust with solvents,and paint the bare spots with heat-resistantaluminum paint. (NOTE: If bare spots totalmore than 20 percent of the entire surface, paintthe equipment.)

Check the thermostat. If the accuracy of thethermostat cannot be adjusted to within 5°Faccuracy, replace it with a new thermostat.

Clean soot deposits and jet openings and repairor replace leaking piping. Clean and tighten thenuts and bolts.

5-6

NOTE

Refer to table R of appendix II for atrouble-shooting chart covering themaintenance of ranges, ovens, andbroilers.

FIELD RANGE

As a Utilitiesman, you need to know how tomaintain, repair, and troubleshoot the field range.Unfortunately, this manual can NOT cover all youneed to know about the field range; therefore, youshould have your supervisor refer you to other sourcesof pertinent information. A gas-fired field range isshown in figure 5-6 and the procedures for setting upand operating the range burner unit is detailed inchapter 2, Utilitiesman Basic, volume 1, NAVEDTRA11019.

Keeping the field range in a constant state ofreadiness is important to everyone in the field. This isaccomplished by performing preventive maintenancechecks and services quarterly or after every 250 hoursof operation, whichever occurs first. Table R ofappendix II provides a listing of possible malfunctionsthat may occur in the field range outfit. This listingwil l help vou in diagnosing and correct ingunsatisfactory operation or failure of the field rangeoutfit. Also, an excellent source of information islisted in the references listed in appendix IV.

Figure 5-6.—Field range with fire unit in position for cooking.

BAKERY OVENS

Routine maintenance of bakery ovens (fig. 5-7)requires weekly, monthly, and annual inspections.

The WEEKLY inspections should include thefollowing:

Adjust the heating units for proper fuel-airmixtures and constant operating temperature.

Check the pilot flame of the gas-fired ovens andadjust it, if necessary, so the burner gas igniteswithout wasting fuel and the flame is not blownout by the flue draft. Adjust the fuel-air mixtureto produce a blue flame.

Check the operation of the purging fan and theflame failure devices.

Clean the soot and dirt from the pilot and gasburner.

Check the oil supply for eaks and stoppages andclean the strainer basket of oil-fired ovens.

Examine the operation of the electric-ignitionand flame-failure devices, and repair them ifnecessary.

Adjust the oil burner for proper spread of fuelacross the combustion chamber and for properfuel-air mixture to maintain a blue flame.

Examine the operation of dampers and clean andadjust them if required.

Check the settings of automatic temperature andhumidity controls; reset the settings of thethermostat and humidistat if necessary.

The MONTHLY inspections should include thefollowing:

Inspect the conveyor and drive and adjust loosechains, belt tension, and any other componentthat may be misaligned.

Adjust the chains of the V-belt tension bymoving the idler sprocket or sliding motor base.

Check the lubrication of gearboxes, bearings,and moving parts.

Examine the oven top and walls for cracks andbreaks; make the repairs if necessary to ensuretightness.

The ANNUAL inspections should include thefollowing:

Drain, flush, and renew the lubricant in thegearboxes. Check the sprockets, gears, and

5-7

Figure 5-7.—Reel oven.

bearings and renew the lubricant according to grease from the waste. They may need cleaning oncethe manufacturer's instructions. each day.

Conduct electrical checks of the insulationresistance of motor windings, controls, andwiring. Clean all contacts of the controls.

Remember that outside grease traps are intended toserve kitchen plumbing fixtures and equipment only.So they should never be connected to soil and wastelines from toilet rooms. To help ensure properfunctioning, clean grease traps at least once a week.Since accumulated odor-forming solids cause septicaction within a short time, remove all solids each timethe traps are cleaned.

INTERCEPTORS AND GREASE TRAPS

Removal of grease from greasy wastes isnecessary if the sewage system is to function properly.One way grease is collected is by ceramic or cast-irongrease interceptors installed inside mess halls.Among the types of interceptors you may encounter isthe Zurn interceptor shown in figure 5-8. Another wayof collecting grease is to use concrete or brick greasetraps outside of buildings. Mess personnel usuallyclean the inside interceptors but you may have to cleanthe outside traps. When inside grease interceptors aremaintained properly, they should collect most of the

The steps of the procedure for cleaning outsidegrease traps include the following:

1. Skim grease from the surface of the trap using anordinary perforated sewer scoop, and place it insuitable containers for disposal.

2. Remove as much odor-forming material aspossible with the same scoop. Treat this refuseas disposable.

5-8

3. Pump out the liquid from the traps every 3

Figure 5-8.—Zurn interceptor.

Q1.

Q2.

Q3.

Q4.

Q5.

Q6.

Q7.

months, and remove all sediment from the

sidewalls and the bottom if necessary.

What person is responsible for conductingsanitary inspections of galley equipment?

What type of steam kettle generates its ownsteam?

When a plunger type of valve is used on steamchests, the valve must be fully depressed whenthe steam chest compartment door is closed.True/False.

How often should the temperature control on asteam table be calibrated?

A steam table thermostat must be accuratewithin plus or minus how many degrees. inFahrenheit?

The wash water temperature of a dishwashershould be maintained within what temperaturerange, in degrees Fahrenheit?

Steel wool should never be used to clean interiorsurfaces of dishwashers for what reason?

Q8. When the proper air-oil mixture is present, a

range burner will have a flame that is what

color?

Q9. How often should the pilot and gas burner be

inspected for soot and dirt?

Q10. Other than ceramic or cast iron, what types of

grease traps are used?

Q11. How often should liquid be pumped from a

grease trap?

LAUNDRY EQUIPMENT

Learning Objective: Recall the procedures forinstallation, maintenance, and repair of laundryequipment.

Laundry equipment varies from one activity toanother, depending upon such factors as the size of thelaundry and the differences in individual types ofequipment produced by various manufacturers, suchas Pellen-Milnor, Bock, Cissell, or Huebsch. Somecommon types of equipment used in most laundries arewashers, extractors, and drying tumblers.

5-9

One type of laundry unit you may encounter inyour work is shown in views A, B, and C of figure 5-9.This laundry unit is mounted on three skids that arefitted together in assembling; the unit. On one skid isthe washer unit, which consists of two, 75-pound, 26-

by 26-inch end-loading washers, and one 30-inch

Figure 5-9.—Skid-mounted laundry unit.

top-loading extractor. View C shows the extractor andthe back of the washers more clearly. The middle skidhas the dryer unit, which consists of two 42- by 42-inchsteam-heated drying tumblers, one air compressor, anelectric-driven motor, and one stainless steel surgetank. The other skid has the boiler unit; it consists ofan oil-fired 33-horsepower steam generator with areturn hot well, a water softener, and a 350-gallonhot-water storage tank. This laundry unit can washand fluff dry 225 pounds (dry weight) of laundry perhour.

In the following sections, information is providedabout the installation, maintenance, and minor repairof laundry equipment. This information is notintended to furnish all the details you need to knowconcerning installation, maintenance, and repair ofwashers, extractors, drying tumblers, and steamgenerators. For specific information, you shouldalways refer to the instruction manual provided by themanufacturer of the equipment.

WASHER

The purpose of a washer is to wash clothes andother suitable materials. The washing process is aseries of baths during which soil is loosened from thematerials, suspended in the water, and finally rinsedaway. Several baths are usually necessary to removethe soil completely.

Operation

The type of washer most often used at Navyactivities is the Pellerin-Milnor end-loaded, fullyautomatic washer (fig. 5-10) that is often referred toosimply as the "Milnor." This washer is provided with aremovable FORMULA CHART, which can be easilychanged at the discretion of the operator. Each formulachart provides a full 88 minutes of operation if desired.Marker labels affixed to the formula show theoperation in progress and which supplies are neededwhen the timer signals. The Milnor washer is alsoequipped with a Miltrol timer to carry the washerthrough a complete cycle by following the formula cutin the chart.

The Milnor washer has an automatic supplyinjector unit that consists of five compartments.Various supplies are placed into these compartments atthe start of the washing cycle. At a designated time,the supplies are flushed from each compartment intothe washer.

5-10

Figure 5-10.—Washer.

Machines equipped with automatic supplyinjection may also be operated manually at any time.To operate manually, however, you must turn the chartto the uncut position. When required, the Milnorwasher can be supplied with an electrically operatedtempering control to thermostatically control thetemperature of the water for the washer.

Milnor washers, when required, can be furnishedwith a device to inject supplemental s teamautomatically when called for by the formula chart andraise the water temperature above that available fromthe hot-water source. This device can also be used tomaintain minimum hot-water temperature in the

generate enough hot water to keep up with thehot-water demand of the plant or to raise the water

washer when the normal hot-water source is unable to

tern perature near the boiling point.

Installation

The steps required to install the Milnor washer areas follows:

1. Install the washer on a steady, level floor, orfoundation. Make sure the machine is properlybolted down to prevent vibration.

2. Assemble the water inlet valves on the rear shellof the washer. (The water inlet valve assemblyand two water inlet valve strainers are shippedinside of the washer.) Assembling the inletvalves consists of plugging in a twist-lockconnection to the rear of the Miltrol timer orplugging bullet connectors into rubber sleeves,as shown on the inside of the Miltrol box.

NOTE

On some models, the inlet valves are

control and do not require installation.permanently attached and wired to the

3. Connect the hot and cold waterlines to the hot-and cold-water inlet valves. (The hot-watervalve is on the left, and the cold-water valve is onthe right when you face the front of the washer.)

6 .

7 .

8.

5 .

4 . Install one of the strainers in each of thewaterlines just ahead of the solenoid valve.Note that some machines have water valves thatdo not require strainers, so when this type ofvalve is used, no strainers are shipped inside ofthe washer cylinder.

Some models are furnished with a "Steam Boil"circuit to allow any or all of the washingoperations at boiling temperature. In such cases,connect the steam line to the steam solenoidvalve near the bottom of the washer shell at therear of the machine.

To eliminate water hammer when the inletvalves close, connect the inlet valves to thewater main with a short piece of rubber hose(about 15 to 24 inches long) between the watermain and the upstream side of the strainers. Theelasticity of the rubber hose prevents thepounding noise that might otherwise occurevery time an inlet valve is closed.

Water inlet valves are rated to handle amaximum of 90-psi pressure. A pressure-reducing valve should be used to limit waterpressure when the pressure exceeds this figure.The steam valve (when furnished) is rated tohandle a maximum of 110-psi pressure, and apressure-reducing valve should be used to limitsteam pressure when it exceeds this figure.

Connect the pressure supply for the automaticdrain valve to the air line or to the cold waterline.The automatic drain valve requires a minimumof 25-psi pressure AT ALL TIMES.

5-11

9.

10.

11.

12.

13.

Connect the drain line to the connection in theBOTTOM of the automatic drain valve. Thethreaded connection in the side of the automaticdrain valve is a cleanout hole only.

The Miltrol timer is equipped with a step-downtransformer to lower the voltage at the contactfingers to 24 volts. Some electrical componentsin the timer operate on 24 volts (the lamps, timerrelays, water valves, etc.). Provide a linedisconnect switch for each washer, so anywasher in your installation can be turned off forrepairs without affecting the operation of theothers.

Adjust the level control for the desired high- andlow-water levels. The level control is set at thefactory to deliver the approximate water depths.However, the final adjustment must be made inthe field.

Connect the supply injector unit to a source ofwater for flushing. Use one size larger if thepipe run is more than 5 feet. When the waterpiping for the supply injector is too small, thesupply injector does hot flush the suppliesproperly. When available, hot water should beused for flushing but only if your hot-watersource is dependable, has at least 20-psipressure, and does not occasionally boil overand produce steam in the hot waterline. If hotwater is not available, use cold water.

Five solenoid valves are within the supplyinjector. These valves can handle a maximumof 30 psi. They are adequately protected againsthigher pressure by the pressure-reducing valvethat has been properly set at the factory todeliver between 25 to 28 psi. Be sure to checkthe pressure gauge and reset it to 25 to 28pounds, as vibration and/or handling inshipment may cause the regulator to get out ofadjustment.

Maintenance and Repair

The Milnor washer should be inspected at regularintervals to ensure that it works properly. If aninspection reveals adjustments or repairs are needed,they should be made promptly.

NOTE

Some models are equipped with electricdrain valves that do not require air orwater pressure connections.

The inspection of a washer should ensure thatproper conditions exist. These conditions include thefollowing:

The machine is level.

All bolts, nuts, and screws are tight.

Latches on cylinder doors work properly.

The thermometers are accurate.

Switches are properly adjusted and workingcorrectly.

Timers are in good working order.

Water level gauges are correct.

All electric controls are working.

you should make special inspections as follows:In addition to the regular scheduled inspections,

EVERY 2 MONTHS:

Check the gearbox oil level and replenish withfresh oi I, if necessary.

SEMIANNUALLY:

Lubricate the clutch drag spring with two orthree drops of light machine oil between theleft-hand chassis end frame and the chart dragspring holder, a shown by arrow (1) in figure5-11.

ANNUALLY:

Drain the gearbox and replenish it with fresh oil.The drain plug in the bottom of the gearbox has asmall magnet in its end to attract metallicparticles in the oil. Be sure to clean off themagnet each time the gearbox is drained andbefore reinserting the drain plug.

Clean the motor clutch assembly, as shown byarrow 2 in figure 5-11, with one or two squirts ofNavy-approved nonflammable cleaning fluid.Wipe the fluid off with a clean, dry rag andlubricate with two or three drops of lightmachine oil to prevent the clutch spring from"gumming up" and allowing the clutch to slip.Wipe off excess lubricant.

Troubleshooting

The washer is a rugged machine, but from time totime you can expect trouble. A troubleshooting chartfor the Milnor washer is contained in table X ofappendix II of this TRAMAN.

5-12

EXTRACTOR

Figure 5-11.—Lubrication and cleaning points on timer.

The purpose of the extractor is to extract waterfrom clothes after rinsing. Water is extracted byspinning the clothes at a high speed, applyingcentrifugal force, pushing the water to the outersurface, and discharging it through small holes in thebasket of the extractor to drain.

Extractors may be equipped with a manual brake(fig. 5-12) or an automatic brake. An assemblydrawing of a manual brake stainless steel extractor isshown in figure 5-13.

Installation

The procedure for installing extractors varies withd i f f e r e n t m a k e s a n d m o d e l s . C o n s u l t t h emanufacturer's manual for specific instructions on the

Figure 5-12.—A manual brake extractor.

model that you are installing. These machines may beinstalled on any good floor or foundation, and theyoperate without excessive vibration if properly leveledand bolted down.

When installing the extractor, you should payspecial attention to the following:

Support the extractor so it is 1 inch above thefoundation. Ensure there is 100 percent contactbetween the hold-down pads and the grout forleveling the extractor.

Check the nameplate before connecting theelectrical source to ensure the proper powersource is connected.

If the extractor is equipped with an automaticbrake, which is operated by air, ensure the properair supply pressure is connected.

When connecting the drain piping, you shouldinstall a short piece of hose on the drain line nearthe extractor to avoid possible problems due tovibration of the unit.

Ensure the rotation of the basket is in theclockwise direction as shown on the nameplate.

Once installation is complete, thoroughly cleanthe inside of the basket to remove the dust andgrime that have accumulated during shipment.

Maintenance and Repair

If the extractor is to give satisfactory service for along period of time, it should be properly maintainedand repaired promptly. Maintenance and upkeep ofthe Milnor extractor requires the following:

The extractor rubbers should be checked atregular intervals. When necessary, the rubbersshould be tightened or replaced.

5-13

Figure 5-13.—An assembly drawing of a manual brake stainless steel extractor.

Remove the basket from the spindle. The basketis held to the spindle with a locknut on the insideof the basket, and the shaft and basket are fittedtogether with a taper. The basket may beremoved from the spindle by "jolting" it off ofthe spindle or, if the extractor has been in servicefor a long period of time, you may have to pressthe basket off of the spindle. Next, remove thepulley, loosen the packing nut, and remove thebearing housing assembly with its shaft andbearings, after which new rubbers may beinstalled and the extractor assembled in reverseorder. When installing new rubbers, be sure toplace the flat face of the rubbers so they face theflange on the bearing housing; this will ensurethat the concave side of the rubbers is down onthe lower rubber and up on the upper rubber.

Ensure the extractor is lubricated at all pointsrecommended by the manufacturer. Also, uselubricants approved by the manufacturer. As forthe frequency, lubricate every 30 days or asexperience dictates.

Troubleshooting

In troubleshooting the extractor, you must be ableto recognize common troubles and know the possiblecauses of the trouble. Obviously, a lot of time mayoften be saved if the cause is found before anycorrective action is started. Table X of appendix IIwill be useful to you as a guide in finding the sources oftroubles in Milnor extractors.

TUMBLER

The tumbler, also called the "drying tumbler," isthe machine used in Navy laundries to removemoisture from materials. The efficient removal ofmoisture by the tumbler provides material that can beironed properly. There are various brands of tumblersmanufactured by such companies as Cissell andHuebsch.

The Huebsch Loadmaster model 42-inch tumbler isoften used at Navy activities. This is a commercial typeof tumbler with a drying capacity of 100 pounds (dryweight) of laundry per hour. A two-motor drive systemprovides independent fan and cylinder operation. Aone-way cylinder rotation and a door safety switch arestandard.

5-14

Another type of tumbler used at Navy activities isthe Cissell model 36-inch tumbler. This tumbler has adrying capacity of 50 pounds (dry weight) of laundryper hour. This tumbler can have heat for dryingsupplied by a oil-fired burner attached to the unit orsupplied by a permanent plant source. It also has a"cool down" feature for permanent press and othermodern-day fabrics.

Installation

The following instructions on the installation,maintenance, and repair of tumblers apply to theHuebsch Loadmaster model 42-inch tumbler. Alwaysconsult the manufacturer's instructions for the brandand model that you are installing.

When installing the tumbler, you should ensure thefollowing:

Ensure the tumbler is level and properly securedto the floor. In leveling, use shims of adequatesize to avoid weight concentration.

The dryer room must be well ventilated. Anopening of 2 square feet to the atmosphere mustbe supplied for each 1,700-cubic-feet per minute(cfm) model and 4 square feet for each3,000-cfm model. Allow adequate clearance onall sides for servicing and efficient loading anddispatching of dried materials.

On steam-heated laundry tumblers, a minimumof 100 psi should be maintained for efficientperformance. Connect 3/4-inch steam supplyand return lines to the coils as marked on the coilhousing.

Laundry tumblers are factory-wired foroperation and require only a power supplyconnection.

A fused disconnect should be installed. Formultiple-tumbler installations, each unit shouldbe equipped with a disconnect switch.

Ensure the fan rotation is correct.

For maximum efficiency of single- ormultiple-unit installation, air discharge must beducted individually to the atmosphere by theshortest possible route. For runs less than 20 feet,the duct size must equal the discharge spout or belarger. For each additional 30 feet of duct run,increase the entire duct diameter by one tenth forround duct or the entire duct area by one fifth forrectangle duct. Discharge to the atmospheremust be constructed to get rid of too much back

pressure and to prevent the entrance of weather.The end of the duct should be at least onediameter away from any obstacle.

Check for correct cylinder, belt, and chainadjustment before starting the unit, as describedlater in this chapter. Turn the power on and startthe tumbler to check the cylinder and fan rotationand the door switch adjustment.

Turn the steam on. Place a load of damp rags inthe cylinder and run until dry. Check thecylinder adjustment under load and check forvibration or unusual noise. Reversing modelsmust be checked for correct time delay betweehreversing cycles. Correct any adjustment beforeplacing the tumbler in service.

Maintenance and Repair

Two views of the tumbler are shown in figures5-14 and 5-15. Try to keep the tumblers operating atpeak efficiency.

Some general maintenance and minor repairprocedures in the care and upkeep of tumblers are asfollows:

MONTHLY:

Loose wire connections can cause tumblerfailure and possible damage. Remove thecontrol box cover and check the controls.

Replace the contactor points when pitted orworn. Check and tighten all wire connections,including thermal overload heating coils.Check for secure mounting of controls to thecontrol box.

ANNUALLY:

Ensure that electric motors are removed andcleaned thoroughly. Frequent tripping of thethermal overload circuit breakers may be causedby low voltage, loose connections, reversed fan,or high ambient temperature. Never increasethermal overload heater size without completeinvestigation.

The door switch, thermostat, and other optionalelectrical equipment require replacement uponfailure. After exchange, check the wiringdiagram before turning on the power. Checkwith the power on. Adjust if necessary beforereturning to service.

ADJUSTMENTS.—In servicing the tumbler,you may have to adjust the belt, chain, cylinder, and

5-15

Figure 5-14.—Right side view of tumbler.

reversing timer (on machines so equipped), and doorsafety switch at various times. To make theseadjustments, refer to the manufacturer’s instructionsfor specific procedures.

LUBRICATION.—Once a month, remove thecircular cover on the drive guard and oil the chain,using SAE-30 oil. The pillow block, trunnion, andmotor bearings are sealed and require no service.

STEAM GENERATOR

The purpose of the steam generator is to provideenough steam to operate tumblers, as well as to providea continuous supply of hot water to the washers underconstant operation. One type of steam generatorfrequently used in laundries at Navy activities is theClayton steam generator, Model RO-33-PL.

NOTE

Some portable skid-mounted units use aself-contained oil-fired water heater tosupply hot water for washers instead of asteam generator.

The Clayton steam generator is a water-tubeboiler that delivers its rated output of 99 percentquality steam (containing less than 1 percentmoisture) per hour from 60°F feedwater. Thegenerator develops its full-rated pressure within 5minutes from a cold start.

The generator features a continuous circulatingfeedwater system with a constant capacity pump thatensures a wet tube in the generator-heating unit at alltimes. Automatic controls regulate the feedwater rate

5-16

Figure 5-15.—Rear view of tumbler.

and modulate or stop the burner by steam demand.Standard equipment includes safety devices forprotection against water fai I ure, burner failure, toomuch pressure, and electrical overload. A flowdiagram of the water and steam circuit of the generatoris shown in figure 5-16. Supply water enters thefeedwater section of the water pump from the hotwell/feedwater tank and is pumped directly to thesteam accumulator. The circulating liquid is drawnfrom the accumulator by the circulating section of thewater pump and pumped into the single-passageheating coil, and then back to the accumulator wherethe steam is separated.

The pump is driven directly by an electric motorand contains no packing boxes. It is arranged in twosections—the feedwater section and the circulatingsection. The pump diaphragms are operatedhydraulically by oil displaced by reciprocating pistonswithin the pump. A built-in solenoid-operated bypassvalve is on the hydraulic pressure section of the

feedwater pump to prevent the feedwater section frompumping when the valve is open. The valve is actuatedby the water level control according to the liquid levelin the accumulator.

Installation

When installing a steam generator, always use themanufacturer's instructions. Pay attention to the fuel,water, electrical, and venting facilities when installingthe boiler and ensure the following:

Ample clearance should be allowed on all sidesto make operation and maintenance easier.

When installing external piping, use pipe unionsnext to the boiler connections to allow easyremoval of parts for inspection and cleaning.

The boiler is equipped to burn No. 2 diesel fueloil. Connect the fuel supply line to the inletconnection on the fuel filter. Connect the return

5-17

Figure 5-16.—Flow diagram of the water and steam circuit in a generator.

line to the return connection below the fuel allow a 60-inch gravity feed to the inlet of thepump. The return line must be a separate line feedwater pump check valve housing forback to the fuel tank and NOT connected to the hot-well temperatures up to 180°F. If higherfuel suction line to prevent locking of air in thefuel system that will cause erratic burner

hot-well temperatures are anticipated, a highergravity feed is required to prevent vapor locking

operation. Do NOT install a shutoff valve in the of the feedwate r pump. For ho t -we l lreturn line; however, a swing check valve may temperatures of 180°F to 200°F, a 72-inchbe installed if the fuel pump is below the fuel gravity feed is necessary. Temperatures abovetank. 200°F require a gravity feed of 84 inches.

Install a stack adapter (supplied with the steamgenerator) directly on the heater cover stackoutlet. Install a stack extension if desired, using12-inch-diameter flue pipe (minimum), andinstall a weather cap (supplied with the unit) atthe top of the flue pipe. If the unit is operated inan enclosed building, extend the flue pipethrough the roof and install a weather cap.

Typical hot-well installation and connectiondata are shown in figure 5-17. The hot well mustbe elevated on a suitable stand or bracket to

The feedwater connection is made byconnecting a line between the feed pumpconnection on the hot well and the feedwaterintake valve. The connection is made by using aminimum of 1-inch-diameter pipe.

The steam header should be connected to thesteam discharge valve. Ensure that the headerpipe size is not smaller than the steam dischargevalve.

A valve bleed line to the atmosphere should beinstalled at the steam discharge. This design

5-18

Figure 5-17.—A typical installation of horizontal hot-well tank and connection data.

be clockwise as viewed from the front of theplant.

Preventive Maintenance and Repair

Like any piece of mechanical equipment, thesteam generator requires proper maintenance andsome repairs will be needed to maintain the efficiencyand service it is designed to provide. The followingdiscussion covers some of the maintenance and repairrequirements for the Clayton steam generator, ModelRO-33-PL. For detai led information on themaintenance and upkeep of this and other types of

allows the release of steam to permit the steamgenerator to operate under full load whenadjustments are made.

Connect the pipe accumulator blowdown valveand coil drain valve to waste. These lines may bemanifolded into a common line of not less thanl-inch-diameter pipe. Connect the pipedischarge from the steam safety valve to thea t m o s p h e r e . Y o u s h o u l d p r o v i d e a1/4-inch-diameter (minimum) pipe drain at thelowest point in the safety valve vent line piping.

The pipe outlet from the accumulator steam trapshould be connected to the condensate returnconnection on the hot well with 3/4-inch-diameter pipe.

To permit periodic checking of the automaticblowdown valve adjustment, you should install ashutoff valve and a flow test valve, as shown infigure 5-18. Pipe the discharge from the shutoffvalve to the automatic blowdown connection onthe hot well.

Make electrical connections to terminals in theelectrical control box. Install a disconnectswitch in the line next to the steam generator toease the isolation of electrical components fromthe line if service is necessary. Start the motormomentarily to check rotation. Rotation should

Figure 5-18.—Suggested automatic blowdown valve discharge

piping.

5-19

generators, consult the manufacturer's instruction sections that follow refer to the name and location of

manual. Before proceeding, observe that figure 5-19

shows the operating controls and parts as seen from the

front of the generator, and figure 5-20 shows the

operating controls and parts as viewed from the rear.

The letters and numbers shown in parentheses in the

operating controls and parts in figures 5-19 and 5-20.

S o m e g e n e r a l m a i n t e n a n c e a n d r e p a i rrequirements for the steam generator are as follows:

If dirt or lint accumulates on the cupped sides ofthe blower rotor blades, a shortage of air to the

1.2.3.4.5.6.7.8.9.

10.11.12.13.14.

START-STOP SWITCH

STEAM SAFETYWATER PUMPR

EMERGENCY RUN SWITCH A. SOOT BLOWER VALVECHECK VALVE B. STEAM DISCHARGE VALVEELECTRICAL CONTROLS BOX C. ACCUMULATOR GAUGE GLASSINTAKE SURGE CHAMBER D. CIRCULATlNG PUMP HOUSINGWATER PUMP SOLENOID E. CIRCULATlNG FEED VALVEAUTOMATIC BLOWDOWN VALVE F. FEEDWATER PUMP HOUSINGFUEL PUMP G. FEEDWATER INTAKE VALVEWATERPUMP DISCHARGE SNUBBER H. ACCUMULATOR BLOWDOWNVALVEBURNER BASE J . COIL DRAIN VALVEHEATING UNIT K. BURNER CONTROL VALVETHERMOSTAT SWITCH L. COIL FEED VALVE

Figure 5-19.—Operating controls and component identification of Clayton steam generator, Model RO-33.PL, front view.

5-20

Figure 5-20.—Operating controls and component indentification of Clayton steam generator, Model RO-33-PL, rear view.

burner causes reduced burner efficiency. Thefrequency of cleaning depends on the amount ofdirt or lint in the air at the installation.

Check the operation of the thermostat controlevery 100 operating hours. Consult themanufacturer's instructions for test procedures.

When a water pump is noisy, the trouble issometimes due to a restricted heating coil thatcauses excessive feed pressure. The feedpressure should be checked for coil restriction.When checking for coil restriction, compare thereading on the feed pressure gauge with that onthe steam pressure gauge. Normal feed pressuremay vary slightly with each installation.Carefully note the pressure right after the steamgenerator is installed, so an accurate check ofcoil restriction can be made for the unit. The coil

is restricted if feed pressure is 30 pounds or moreabove the normal feed pressure notedimmediately after installation or when the coilwas completely clean.

The steps of the procedure used to blowdown thesystem are as follows:

1. With the plant operating at normal steampressure, close the circulating feed valve (E) andopen the coil drain valve (J). Start a time check.After 30 seconds, shut off the burner and closethe steam discharge valve (B).

NOTE

If the burner is shut down by the thermostatc o n t r o l d u r i n g t h e t i m e c h e c k ,immediately open the burner control valve(K); then close the steam discharge valve.

5-21

2.

3.

4.

5.

Open the accumulator blowdown valve (H).

When the steam pressure drops to zero, close thecoil drain valve (J) and the accumulatorblowdown valve (H).

Open the circulating feed valve (E).

To resume operation, allow the plant to fill withwater and start the burner in the normal manner.You may have to reprime the circulating pumpafter the blowdown. To prime the feedwaterpump, refer to the manufacturer’s instructions.

Additional inspection and maintenance factors forthe steam generator are as follows:

When the electric motor is equipped with sealedbearings, the bearings are prelubricated for thelife of the bearings. However, motors equippedwith oil-wick-lubricated bearings should have 1teaspoon of good grade oil added to thereservoirs every 6 months.

If the motor is equipped with pressure greasefittings, remove the plug below the motor shaftevery 6 months and force a light grade of greaseinto the port at the top until the clean greaseappears at the plug outlet. To prevent rupture ofthe grease seals, run the motor for 4 or 5 minutesbefore replacing the plug below the motor shaft.

Every year (more o f ten under severeoperations), drain and refill the water pumpcrankcase with a good grade of SAE 20 motor oil(about 5 quarts required). With the pumprunning, oil should show at least halfway in thesight gauge.

The water pump check valves should also beinspected and cleaned when you remove scalefrom a restricted heating coil. Check the disks,springs, and valve seats for scale and pitting.

The relief valve (fig. 5-21) of the water pumpshould be adjusted to open at about 500-psi feedpressure but remain driptight during operation.Leakage from this valve results in a lack of waterto the heating unit and causes overheating.Sometimes when the unit is started, the feedpressure may temporarily rise enough to causethe relief valve to release a small amount ofwater; however, the feed pressure will return tonormal after the unit heats and the systembecomes stabilized.

The water pump discharge snubber (fig. 5-22) isnonadjustable. If the rubber insert has to be

Figure 5-21.—Pump relief valve.

replaced, the old insert must be cut away fromthe retainer. To ease assembly, lubricate thenew insert with glycerine (do not use oil) toallow it to be pushed into the retainer and bottomhousing.

To keep the ring thermostat control of thegenerator (fig. 5-23) at peak operation, you mayhave to adjust the thermostat switch and thethermostat ring channel. The plant must beoperated long enough to be thoroughly heatedbefore you adjust the thermostat switch. Inmaking these adjustments, refer to themanufacturer's instructions.

Adjust the thermostat ring channel (Number 23of fig. 5-23) when replacing the heating coil or ifthe original assembly has been disturbed. Acareful check of the adjustment must also bemade if the thermostat switch cannot be adjustedwithout erratic response.

Figure 5-22.—Water pump discharge snubber.

5-22

Figure 5-23.—Ring thermostat control.

The automatic damper should be kept in properadjustment to ensure a proper supply of air to theburner.

The burner manifold (fig. 5-24) requirescleaning and adjusting at times to keep it in goodshape. Remove the manifold. Scrape carbondeposits from the manifold and ignitionelectrodes. Clean the burner nozzles andstrainer.

CAUTION

When cleaning, you should NOT use asharp instrument that can scratch ordisfigure the tip orifice or slots in thedistributor. A slight scratch on theseparts can seriously impair nozzleoperation.

Adjust the ignition electrodes to conform withthe dimensions shown in figure 5-24. The gapmust be positioned as accurately as possible, soit is at the immediate edge of the nozzle spray.Be careful when bending and adjusting theelectrodes to avoid cracking the insulators. Theinsulators may develop an invisible short due tosuch a fracture, resulting in ignition failure.

The fuel pressure to the burner must be properlymaintained. Excessive fuel pressure causes theburner to smoke and results in sooting of theheating coil. However, if fuel pressure is too

low, the plant comes up to pressure slowly anddoes not maintain adequate steam pressureduring periods of maximum steam demand.Adjust the pressure as needed.

Figure 5-25 shows a drawing of a fuel pressureswitch. To adjust the switch, close the light andfuel indicator pilot when fuel pressure rises toabout 70 psi by turning the adjusting screw (1)clockwise to increase or counterclockwise todecrease pressure at which the switch closes.This step allows enough pressure to induceproper atomization when fuel is admitted to theburner. Secure the adjusting screw with thelocknut after adjustment.

The steam pressure switch (SPS) can be adjustedto open and stop the burner at any maximumpressure between 65 and 195 psi. The switchcloses and restarts the burner when steampressure drops about 8 psi below that point.

The modulating pressure switch (MPS) isnormally adjusted to modulate the burner to"low-fire" operation when steam pressurereaches 10 psi below maximum and to return theburner to "high-fire" operation when steampressure drops about 8 psi below that point. Therecommended setting of 10 psi below themaximum, in most cases, provides both stableoperation and stable steam pressure duringfluctuating demand.

5-23

The automatic blowdown valve (fig. 5-26) isoperated by oil pressure from the water pump. Ifthe blowdown valve diaphragm gets ruptured,oil will likely appear in the waste discharge.Rep lace a rup tu red va lve d iaphragmimmediately to prevent the loss of oil from thepump crankcase.

As preventive maintenance, replace theblowdown valve diaphragm whenever the waterpump diaphragms are replaced. Since wear mayaffect the operation of the blowdown valve,dissemble the valve each time the diaphragm isreplaced.

Troubleshooting

A troubleshooting chart for the Clayton steamgenerator, Model RO-33-PL, is provided in table S ofappendix II. This chart will guide you in finding andcorrecting troubles in that make and model ofgenerator. You will find similar charts in theinstruction manuals provided by the manufacturers ofother makes of steam generators. Make sure you arefamiliar with the manufacturer's manual for thegenerator used at your activity, and follow the

Figure 5-24.—Burner manifold.

procedures prescribed for the maintenance and repairof the equipment.

RESIDENTIAL WASHING MACHINES

The automatic washer (fig. 5-27), described in thischapter, is typical of the machines on the market today.

more common features found in several differentmodels. For the equipment you are installing orworking on, follow the manufacturer's instructionmanual.

The circuits and timing diagrams are composites of the

The automatic clothes washing cycle can bebroken down into four basic operations—fill, agitate,spin, and drain. Nearly all of these operations arerepeated two or more times throughout a completewashing cycle and, for the most part, are controlled bya timing assembly.

The FILL operation begins immediately afterstarting the washer, but the timer does not start until thewater level is at the proper height. Some models usetimed-fill operations that start and end under thecontrol of the timer of the washer. Also, note that thereare no timed-fill operations. This type of washer uses ano timed-fill feature initiated by the timer but

5-24

Figure 5-25.—Fuel pressure switch.

terminates whenever the water level sensing switchcloses. When the water level sensing switch is finallyactivated, the timer starts running and the agitationoperation commences.

The AGITATION operation function is to providewashing and rinsing of the laundry once the tub is filledwith water. There are two basic methods of washingaction in general use. One is a reciprocating agitator

tank. The other is a rotating drum that picks up thethat swirls the water and clothes back and forth in a

clothes and allows them to drop into a pool or stream ofwater. Most automatic washers are of the agitator,top-loading variety.

The SPIN operation function is to remove excesswater from the laundry fabrics. During this operation,the main drive motor spins the laundry tub at arelatively high rate of speed, forcing water out of thetub and laundry fabrics by means of centrifugal force.The drain pump removes this spun-out water from thewasher; therefore, the DRAIN operation function is topump the used wash water and rinse water out of thewasher and into the wastewater system.

Modern automatic clothes washers include anumber of optional features that do not appear asnecessary parts of the timing diagram. The morecommon options are as follows:

Most washers have a high/low water levelselector switch; some give the user a choice ofhigh, medium, and low water levels; and a fewwashers have an "infinite" water leveladjustment that lets the user set the water to anydesired level. The purpose of such a switch is toconserve water whenever the laundry tub is onlypartially filled with laundry. Some washers donot have a water level selector switch, and allwash and rinse phases run with the tub filled tocapacity.

In most washers you normally have access to aset of switches, push buttons, or a dial that allowsa choice of water temperatures. Newer andbetter washers have separate selector switchesfor the wash water and rinse water phases; hotwater, warm water, or cold water for the washingphase; and warm water or cold water for therinsing phase. In the simplest washers, theswitch might only permit a selection of either hotor cold water for both the washing and rinsingphases of the wash cycle.

The agitation speed selector lets you select anormal or gentle speed for the agitation action.The gentle speed is used only in instances wherethere is a chance that normal speed might harmcertain types of fabrics. It is important to notethat this speed selector switch does not influencethe timing in any way. For example, if you setup a 10-minute washing operation, the operationoccupies a full 10 minutes whether the agitatorspeed is set to normal or gentle.

Operation

An automatic washer can be an elaborate piece ofelectromechanical equipment. Most modern washershave a number of basic electrical and mechanical partsthat work much the same way in every make andmodel. The primary parts include the following:

1. a timer assembly,

2. solenoids for controlling the inflow of hot andcold water,

3. a transmission and a main drive motor forproviding the powerful agitation and spinactions,

5-25

Figure 5-26.—Automatic blowdown valve.

4. a water pump assembly for recirculating and

removing water from the washer, and

5. a host of controls and switches.

These components are discussed in terms of whatthey do and how they do it in the following paragraphs.

TIMER ASSEMBLY.—The timer assembly isthe "brain" of the automatic washer. The timers foundin automatic washers are not much different from thosefound in some other major appliances, includingautomatic dryers and dishwashers. The cam-operatedswitch contacts are responsible for starting andstopping most of the basic washer operations.

The basic elements of a timing switch assemblyare a split-phase motor, a set of cams, and some contactswitches. The motor, usually geared down to a speedof about one-half revolution per hour, turns a set ofcams that open and close banks of switch contacts.

The switch contacts control the flow of line power tothe various electrical devices in the washer.

TRANSMISSON ASSEMBLY.—The trans-mission in an automatic washer is the most complexpiece of mechanical machinery in the applianceindustry. The transmission is wholly responsible forconverting the rotary motion of the main drive motorinto either an agitating motion or spinning action.Although there is often a direct linkage between thedrive motor shaft and the cam assembly that producesthe agitating motion, the motor is connected to the spinsection of the transmission by means of a frictionclutch that lets the laundry tub reach its normalspinning speed gradually without overloading themotor.

In some current models, the transmission is shiftedfrom one type of action to another by means of asolenoid-operated gearshift. The majority, however,shift between agitate and spin according to the

5-26

Figure 5-27.—A typical automatic residential washer.

direction the drive motor spins. Whenever the drivemotor turns in one part icular direct ion, thetransmission is shifted to the spin gear. Reversing themotor then automatically shifts the transmission to itsagitate gear.

Some washing machine transmissions also have aneutral gear that allows the drive motor to turn withoutcausing either the spin or agitation action to occur.This feature is used during drain operations that call forrunning the water pump by itself.

MAIN DRIVE MOTOR.—The main drivemotor is responsible for converting electrical energyinto the kind of mechanical power that is necessary forcarrying out the agitation, spin, and pumping actions ofthe washer. The motor is normally a split-phaseinduction motor that is rated at about one-halfhorsepower. Washer motors, almost withoutexception, operate on 120-volt line power.

A capacitor-start feature is not necessary forwashing machines using fractional horsepower drivemotors, but a centrifugal switch or relay-startmechanism is always an integral part of the controlsystem of the main drive motor. In some cases, youwill find that washer motors are also reversible andthey sometimes have built-in speed control windings.

WATER PUMP ASSEMBLY.—The primarypurpose of the water pump is to draw used water out ofthe washer at the end of the washing and rinsing stepsand during spin operations. The pump is also used to

turning.

recirculate the wash and rinse water with the use of alint filter. The water pump is mechanically driven bythe transmission and main drive motor and is operatinganytime the main drive motor is running. Considernow the fact that the main drive motor is reversible inmost models. It runs in one direction for agitationoperations and in the opposite direction for spinoperations. This means the water pump runs in bothdirections as well; and the logical conclusion is thepump moves water in two different directions,depending on which way the main drive motor is

It is possible to take advantage of this two-direction characteristic of the water pump by using it inconjunction with a two-way flapper-valve assembly.The idea is to recirculate the wash or rinse water duringagitation operations and to pump the water out of thesystem during spin operations. By turning the drivemotor and pump in the agitation direction (fig. 5-28,view A), valve A is opened and valve B is closed. Thewater is thus routed through the water recirculationsystem inside the machine. By turning the drive motorand pump in the spin direction (fig. 5-28, view B),valve A is closed and valve B is opened. Since valve Bleads to the wastewater system, moving the water inthat direction effectively drains it all out of the washer.This makes it possible to use a flapper-valve assemblyfor routing the water without using extra electricalcontrols and timer switches. Some washers control therouting of the pump water by means of solenoid valves.

Figure 5-28.—Operation of a flapper-valve water controlsystem: A. Pump turning in the agitate direction torecirculate the water; B. Pump turning in the spindirection to pump water out of the washer.

5-27

keeping their respective valve ports closed. The portsopen only when electrical power is sent to the solenoidwindings.

WATER VALVES.—The water valves controlthe inflow of hot and cold water during fill operations.The valves are electrically operated, as shown in figure5-29. The solenoids are turned off most of the time,

The two water valve solenoids can be operatedindividually or at the same time. Activating the "hot"valve, for instance, fills the washer with hot water.Energizing the "cold" valve fills the washer with coldwater, and energizing both valves at the same time fillsthe washer with warm water—a mixture of hot andcold.

The water temperature selector switch determinesthe water valves to be operated during any given filloperation; timer contacts are responsible forenergizing the selected solenoids at the appropriatetimes.

A typical water-fill circuit for modern automaticwashers is shown in figure 5-30. The hot- andcold-water solenoid valves are energized throughseveral sets of timer contacts and a water temperatureselector switch assembly.

WATER LEVEL SENSING SWITCH.—Washers that do not use a timed-fill interval must haveprovisions for sensing the water level and turning offthe water supply whenever a given water level isreached. This sensor normally takes the form of apressure switch that is activated either directly by thewater pressure on the bottom of the laundry tub orindirectly activated by air pressure in a tube located atthe rear of the washer.

The diagram in figure 5-31 shows the operation ofthe indirect, or air pressure, sensing mechanism. Thewater level in the tub is always the same as the water

level in the washer. As the water level rises, the airpressure at the top of the tub increases. A pressureswitch at the top of the tub can be adjusted to close atvarious pressure levels, representing different waterlevels in the washer.

ongoing operation.

DOOR INTERLOCK SWITCH.—The doorinterlock switch is a safety feature that completelyshuts down the washer whenever the door or lid isopened during a spin operation. Opening the doorduring any other part of the cycle does not affect the

The diagram in figure 5-32 shows how the doorinterlock switch is bypassed by a timer contact. Thetimer contact is closed throughout most cycles of thewasher, allowing the lid switch to be opened withoutinterrupting current flow to the motor circuit. Duringevery spin operation, however, the timer opens thebypass switch, letting the lid switch interrupt thecomplete circuit to the motor whenever the lid isopened during that particular operation.

This list of mechanical and electrical componentsis not complete as far as the full range of modernclothes washer models is concerned. This list iscomplete, however, in the sense that it describes themost critical components and those that are unique toclothes washers.

Installation

Satisfactory performance of an automatic washingmachine depends on a carefully planned and properlydesigned first installation. The place where thelaundry is done should be well lighted and adequatelyequipped with convenient electrical outlets. Theplumbing connections must be anchored to the floor toprevent movement.

Figure 5-29.—Hot- and cold-water solenoid valve control system.

5-28

Figure 5-30.—Water temperature selector circuit: A. Circuit diagram; B. Switch closes for different combinations of wash andrinse water temperatures.

Figure 5-31.—A water level sensor scheme: A. Water level below the set point on the sensor; B. Water level at the set point.

Various local code regulations apply in mostcommunities to permanent plumbing and electricalinstallations; however, local codes and militaryspecifications can vary. The National Plumbing Codeand NAVFACENGCOM guide specifications alsoprovide installation requirements. Figure 5-33 shows

ROICC (Resident Officer in Charge of Construction)says is the final word.

Troubleshooting

Now you know what the components in a washingmachine do and how they do it. Use the trouble-

an installation that meets the requirements of the shooting chart in table T of appendix II as a guide orNational Plumbing Code. In summary, installation checklist for some of the common problems, causes,depends upon where you are. In a conflict, what the and ways to fix them.

5-29

Figure 5-32.—Door switch and override circuit.

RESIDENTIAL CLOTHES DRYERS

Automatic clothes dryers (fig. 5-34) have twoprimary advantages over the old clothesline process.First, the laundry drying job is much faster with theautomatic dryer. The user does not spend as muchtime setting up the process and the actual dryingoperation takes less time. The other advantage of anautomatic drying scheme is that it can be used at anytime of the day, in any season of the year, and under anysort of weather conditions.

Depending on the type of heat energy used,clothes dryers may be divided into two generalclasses—electric dryers and gas dryers. The source ofheat in the electric dryer is obtained electrically by aheating element mounted in the dryer. A centrallylocated thermostat and timer control the heating

Figure 5-34.—A typical residential dryer.

element. In a gas dryer, the source of heat is derivedfrom ignited gas, which is obtained by turning on thegas flow; however, a pilot light must first be burning inthe combustion chamber. This pilot ignition isautomatic; lighting takes place when a spark is createdby turning a knob usually on the dryer control panel.

All dryers, irrespective of heating methods used,are equipped with a forced-air blower to draw in freshair, force it through a heating assembly, and then

Figure 5-33.—Automatic washer installation.

5-30

channel it into the rotating hamper. The warmed airpicks up moisture from the laundry, as it passesthrough the hamper. The blower finally directs themoisture-laden air through a lint filter that traps mostof the dry, lightweight particles of lint and otherforeign materials picked up by the moving air beforethe air is discharged from the dryer.

The heating assembly in an all-electric dryerconsists of a set of nichrome heating elements situatedin the forced-air steam. The heating assembly in a gasdryer performs exactly the same function, but it usesgas flame heat.

The electrical sections of modern clothes dryerscan be rather simple compared to some other kinds ofmodern appliances. The basic electrical units of adryer include heating controls that maintain a fairlyconstant drying temperature and a timer mechanismthat turns off the dryer at the end of a selected dryinginterval. The essential differences between thesimpler dryer models and the top-of-the-line versionscan be found in the number and types of heat and timercontrols.

All automatic dryers include a basic cycle that isnormally labeled a "Timed Cycle"” on the timer controlknob. When operation is done in this mode, the dryertumbles the laundry continually and regulates the levelof the forced air throughout the entire drying interval.The tumbling and heating actions both stop at the endof the selected drying time. You can set the dryinginterval to any point between zero and about180 minutes, depending on the amount and wetness ofthe load.

Operation

Automatic clothes dryers operate on a simpleprinciple, involving the following essential parts:

An exhaust fan

A perforated metal drum

Automatic controls

An electric motor to rotate the drum

A source of heat—either gas or electric.

In operation, wet or damp clothes are placed intothe drum, and after the door is closed, the thermostaticcontrol is set to the correct heat level; the timer is alsoset to the desired running time. The best temperatureand running time combination depends on the type ofclothing, the material of which it is made, the weight ofthe clothing, and the amount of water it contains. Thecorrect combination for various loads is normally

indicated on a chart near the control knobs; if not,consult the owner's manual.

Once the correct control combination has been set,the drum begins to rotate at about 50 revolutions perminute, and the heat turns on to start the dryingfunction. Air circulation is provided simultaneouslyby the motor-driven fan, circulating the heated airthrough the clothing. Baffles on the sides of the drumtend to carry the clothes to the top of the dryer drum, atwhich time they drop to the bottom. These bafflesprevent the clothes from lumping together and providea tumbling action that speeds up the drying process.The door may be opened at any time during the cycle.When the controls are functioning properly, anyopening of the dryer door stops the dryer cycle, turningoff the heater and other motors. If more time remainsin the cycle, the drying action resumes when the door isclosed; in some cases, the start button must be pressed.

Although a motor drive belt may break from timeto time or a bearing becomes jammed, most problemsinvolving automatic clothes dryers are in the automaticcontrols. In most cases, the contacts become worn,wiring becomes short-circuited or open, and so on.

Installation

When installing a dryer, either a new one or onethat has been repaired, observe all codes andordinances that apply to the particular dryer. Theinformation below will help you in installing,repairing, and locating a dryer. Leave enough spacearound the dryer for ease of installation, use, andservice.

If the dryer is to be installed in a confined area,such as a closet or bathroom, it must be exhausted tothe outside. Furthermore, it must have enough spacearound it and enough air circulation to operateproperly.

The electric service should conform with theNational Electric Code as well as local codes andordinances. When gas is used as the heat source, theinstallation must conform to the National Fuel GasCode and local codes and ordinances.

Never exhaust the dryer into a chimney or anyother duct or vent. The dryer must have its ownexhaust system. Before putting a dryer into use afterinstalling or servicing, replace all access and servicepanels. If still attached, read and follow all caution anddirection labels attached to the dryer.

While servicing, review the wiring diagram thataccompanies the dryer. This diagram is usually

5-31

attached to the access panel. The dryer vent should notexceed a maximum length of 4 feet primarily becausethe buildup of condensation increases the timerequired to dry the clothes.

Troubleshooting

You need to be acquainted with the operation andfunctioning of both the mechanical and electricalsystems. Although the various types of clothes dryersmay differ in appearance and location of controls, theyall operate on the same principles and arefundamentally similar in servicing. Clothes dryertimers are quite similar to those on an automaticwashing machine, while thermostats used in automaticdryers are the same type as those used on electricranges.

Since the only moving parts consist of the motor,drive, drum, and exhaust fan, the clothes dryer, whenproperly installed, should give years of trouble-freeservice. When called on, the service personnel shouldbe fami l i a r wi th the r ecommenda t ions andspecifications of the particular manufacturer's servicemanual to replace any worn-out or faulty componentcorrectly. When a dryer does not operate properly,always try the service manual first. However, table Uof appendix II may be used for further troubleshootingand repair should it become necessary.

Q12. What is the maximum operation time that can beprovided by the formula chart on the Milnorwasher?

Q13. The automatic supply injector of a washerconsists of how many compartments?

Q19.

Q14.

Q15.

Q16.

Q17.

Q18.

Q20.

Q21.

Q22.

Q23.

Q24.

Q25.

Q26. What are the two classes of residential dryers?

The automatic drain valve for a washer requiresa minimum of whatpsi?

The supply injectorwhat maximum psi?

solenoid valves can handle

How often should the gearbox oil level bechecked?

Extractors are eq uipped with either anautomatic or manual brake. True/False.

When installing an extractor, you should checkthe equipment nameplate before connecting thepower source for what reason?

An opening of how many square feet must beprovided for a 3,000 cfm dryer for properventilation?

The electric motors on a tumbler should becleaned and inspected annually.’ True/False.

The Clayton steam generator can develop itsfull-rated capacity from a cold start in whatlength of time?

When. installing a boiler, you should always usewhat manual?

Reduced burner efficiency can be caused by dirtor lint on what device?

What are the four basic operations of aresidential washer?

What component converts electrical energy intomechanical power necessary to carry out washeroperations?

5-32

CHAPTER 6

REFRIGERATION

Learning Objective: Describe the stages of heat theory and the principles involvedin heat transfer, and recognize various components of refrigeration systems andtheir application. Recognize the characteristics and procedures required to serviceand troubleshoot rcfri gerat ion systems.

Modern refrigeration has many applications, suchas preserving medicine, blood, and the most importantapplication, the preservation of food. Most foods keptat room temperature spoil rapidly. This is due to therapid growth of bacteria. Refrigeration preserves foodby keeping it cold, which greatly slows down thegrowth of bacteria. In days past, blocks of ice wereused in iceboxes to refrigerate food and other items.These iceboxes were small and not very practical.Today, mechanical refrigeration systems maketransportation, storage, and use of refrigerated goodseasy and practical.

The installation, operation, adjustment, and repairof refr igerat ion equipment are the primaryresponsibility of the Utilitiesman rating. To performthese duties required of a refrigeration mechanic, youneed to understand the principles and theory ofrefrigeration and recognize system components andunderstand the way they work within the system.

Methods of installing, maintaining, and repairingrefrigeration equipment and maintaining, servicing,and repairing domestic refrigerators and freezers arealso covered in this chapter.

HEAT AND REFRIGERATIONPRINCIPLES

Learning Objective: Explain the basics of heat theoryand the basic principles of refrigeration.

REFRIGERATION is the process of removingheat from an area or a substance and is usually done byan artificial means of lowering the temperature, suchas the use of ice or mechanical refrigeration.MECHANICAL REFRIGERATION is defined as amechanical system or apparatus so designed andconstructed that, through its function, heat istransferred from one substance to another. Sincerefrigeration deals entirely with the removal or transfer

of heat, some knowledge of the nature and effects ofheat is necessary for a clear understanding of thesubject.

NATURE OF HEAT

Heat is a form of energy contained to some extentin every substance on earth. All known elements aremade up of very small particles, known as atoms,which, when joined together, form molecules. Thesemolecules are particular to the form they represent.For example, carbon and hydrogen in certaincombinations form sugar and in others form alcohol.

Molecules are in a constant state of motion. Heat isa form of molecular energy that results from the motionof these molecules. The temperature of the moleculesdictates to a degree the molecular activity within asubstance. For this reason, substances exist in threedifferent states or forms—solid, liquid, and gas.Water, for example, may exist in any one of thesestates. As ice, it is a solid; as water, it is a liquid; and assteam, it is a gas (vapor).

When heat is added to a substance, the rate ofmolecular motion increases, causing the substance tochange from a solid to a liquid, and then to a gas(vapor). For example, in a cube of ice, molecularmotion is slow, but as heat is added, molecular activityincreases, changing the solid "ice" to a liquid "water"(fig. 6-1). Further application of heat forces themolecules to greater separation and speeds up theirmotion so that the water changes to steam. The steamformed no longer has a definite volume, such as a solidor liquid has, but expands and fills whatever space isprovided for it.

Heat cannot be destroyed or lost. However, it canbe transferred from one body or substance to another orto another form of energy. Since heat is not in itself asubstance, it can best be considered in relation to its

6-1

Figure 6-1.—The three states of matter.

effect on substances or bodies. When a body orsubstance is stated to be cold, the heat that it contains isless concentrated or less intense than the heat in somewarmer body or substance used for comparison.

UNITS OF HEAT

In the theory of heat, the speed of the moleculesindicates the temperature or intensity of heat, while thenumber of molecules of a substance indicates thequantity of heat.

The intensity and quantity of heat may beexplained in the following simple way. The water in aquart jar and in a 10-gallon container may have thesame intensity or temperature, but the quantity of heatrequired to raise these amounts of water to a higheruniform temperature (from their present uniformtemperature) will differ greatly. The 10 gallons ofwater will absorb a greater amount of heat than thequart jar of water.

The amount of heat added to, or subtracted from, abody can best be measured by the rise or fall intemperature of a known weight of a substance. Thestandard unit of heat measure is the amount of heatnecessary to raise the temperature of 1 pound of water1°F at sea level when the water temperature is between32°F and 212°F. Conversely, it is also the amount ofheat that must be extracted to lower by 1oF thetemperature of a pound of water between the sametemperature limits. This unit of heat is called a British

thermal unit (Btu). The Btu's equivalent in the metricsystem is the calorie, which is the amount of heatrequired to raise one gram of water 1o Celsius.

Suppose that the temperature of 2 pounds of waterwas raised from 35°F to 165°F. To find the number ofBtu required to increase the temperature, subtract 35from 165. This equals a 130° temperature rise for 1pound of water. Since 2 pounds of water were heated,multiply 130 by 2, which equals 260 Btu required toraise 2 pounds of water from 35°F to 165°F.

MEASUREMENT OF HEAT

The usual means of measuring temperature is athermometer. It measures the degree or intensity ofheat and usually consists of a glass tube with a bulb atthe lower portion of the tube that contains mercury,colored alcohol, or a volatile liquid. The nature ofthese liquids causes them to rise or fall uniformly in thehollow tube with each degree in temperature change.Thermometers are used to calibrate the controls ofrefrigeration. The two most common thermometerscales are the Fahrenheit and the Celsius.

On the Fahrenheit scale, there is a difference of180° between freezing (32°) and the boiling point(212°) of water. On the Celsius scale, you have only100° difference between the same points (0° freezingand 100° boiling point).

Of course, a Celsius reading can be converted to aFahrenheit reading, or vice versa. This can beexpressed in terms of the following formula:

F = (C x 1.8) + 32

To change Fahrenheit to a Celsius reading, theterms of the formula are as follows:

C = (F-32) ÷ 1.8

TRANSFER OF HEAT

Heat flows from a substance of higher temperatureto bodies of lower temperature in the same manner thatwater flows down a hill, and like water, it can be raisedagain to a higher level so that it may repeat its cycle.

When two substances of different temperatures arebrought in contact with each other, the heat willimmediately flow from the warmer substance to thecolder substance. The greater the difference intemperature between the two substances, the faster theheat flow. As the temperature of the substances tendsto equalize, the flow of heat slows and stopscompletely when the temperatures are equalized. This

6-2

characteristic is used in refrigeration. The heat of theair, of the lining of the refrigerator, and of the food tobe preserved is transferred to a colder substance, calledthe refrigerant.

Three methods by which heat may be transferredfrom a warmer substance to a colder substance areconduction, convection, and radiation. Theseprinciples are explained in chapter 4 of this TRAMAN.

SPECIFIC HEAT

SPECIFIC HEAT is the ratio between the quantityof heat required to change the temperature of 1 poundof any substance 1°F, as compared to the quantity ofheat required to change 1 pound of water 1°F. Specificheat is equal to the number of Btu required to raise thetemperature of 1 pound of a substance 1oF. Forexample, the specific heat of milk is .92, which meansthat 92 Btu will be needed to raise 100 pounds of milk1oF. The specific heat of water is 1, by adoption as astandard, and specific heat of another substance (solid,liquid, or gas) is determined experimentally bycomparing it to water. Specific heat also expresses theheat-holding capacity of a substance compared to thatof water.

A key RULE to remember is that .5 Btu of heat isrequired to raise 1 pound of ice 1oF when thetemperature is below 32°F; and .5 Btu of heat isrequired to raise 1 pound of steam 1°F above thetemperature of 212°F.

SENSIBLE HEAT

Heat that is added to, or subtracted from, asubstance that changes its temperature but not itsphysical state is called SENSIBLE HEAT. It is theheat that can be indicated on a thermometer. This is theheat human senses also can react to, at least withincertain ranges. For example, if a person put their fingerinto a cup of water, the senses readily tell that personwhether it is cold, cool, tepid, hot, or very hot. Sensibleheat is applied to a solid, a liquid, or a gas/vapor asindicated on a thermometer. The term sensible heatdoes not apply to the process of conversion from onephysical state to another.

LATENT HEAT

LATENT HEAT, or hidden heat, is the term usedfor the heat absorbed or given off by a substance whileit is changing its physical state. When this occurs, theheat given off or absorbed does NOT cause a

temperature change in the substance. In other words,sensible heat is the term for heat that affects thetemperature of things; latent heat is the term for heatthat affects the physical state of things.

To understand the concept of latent heat, you mustrealize that many substances may exist as solids, asliquids, or as gases, depending primarily upon thetemperatures and pressure to which they are subjected.To change a solid to a liquid or a liquid to a gas, ADDHEAT; to change a gas to a liquid or a liquid to a solid,REMOVE HEAT. Suppose you take an uncovered panof cold water and put it over a burner. The sensible heatof the water increases and so does the temperature. Asyou continue adding heat to the water in the pan, thetemperature of the water continues to rise until itreaches 212°F. What is happening? The water is nowabsorbing its latent heat and is changing from a liquidto a vapor. The heat required to change a liquid to a gas(or, the heat that must be removed from a gas tocondense it to a liquid) without any change intemperature is known as the LATENT HEAT OFVAPORIZATION.

Now suppose you take another pan of cold waterand put it in a place where the temperature is below32°F. The water gradually loses heat to i tssurroundings, and the temperature of the water drops to32°F until all the water has changed to ice. While thewater is changing to ice, however, it is still losing heatto its surroundings. The heat that must be removedfrom a substance to change it from a liquid to a solid(or, the heat which must be added to a solid to change itto a liquid) without change in temperature is called theLATENT HEAT OF FUSION. Note the amount ofheat required to cause a change of state (or the amountof heat given off when a substance changes its state)varies according to the pressure under which theprocess takes place. Figure 6-2 shows the relationshipbetween sensible heat and latent heat for one substance– water at atmospheric pressure. To raise thetemperature of 1 pound of ice from 0°F to 32°F, youmust add 16 Btu. To change the pound of ice at 32°F toa pound of water at 32°F, you add 144 Btu (latent heatof fusion). There is no change in temperature while theice is melting. After the ice is melted, however, thetemperature of the water is raised when more heat isapplied. When 180 Btu are added, the water boils. Tochange a pound of water at 212°F to a pound of steam at212°F, you must add 970 Btu (latent heat ofvaporization). After the water is converted to steam at212°F, the application of additional heat causes a risein the temperature of the steam. When you add 44 Btu

6-3

to the steam at 212°F, the steam is superheated to300°F.

TOTAL HEAT

TOTAL HEAT is the sum of sensible heat andlatent heat. Since measurements of the total heat in acertain weight of a substance cannot be started atabsolute zero, a temperature is adopted at which it isassumed that there is no heat; and tables of data areconstructed on that basis for practical use. Data tablesgiving the heat content of the most commonly usedrefrigerants start at 40°F below zero as the assumedpoint of no heat; tables for water and steam start at 32°Fabove zero. Tables of data usually contain a notationshowing the s tar t ing point for heat contentmeasurement.

DAY-TON OF REFRIGERATION

A day-ton of refrigeration (sometimes incorrectlycalled a ton of refrigeration) is the amount ofrefrigeration produced by melting 1 ton of ice at atemperature of 32°F in 24 hours. A day-ton is oftenused to express the amount of cooling produced by arefrigerator or air-conditioner. For example, a 1-tonair-conditioner can remove as much heat in 24 hours as1 ton of 32°F ice that melts and becomes water at 32°F.

Figure 6-2.—Relationship between temperature and theamount of heat required per pound (for water at atmospheric

pressure).

It is a rate of removing heat, rather than a quantity ofheat. A rate can be converted to Btu per day, hour, orminute. To find the rate, proceed as follows:

Per Day: Multiply 2,000 (number of pounds ofice in 1 ton) by 144 (latent heat of fusion perpound) = 288,000 Btu per day

Per Hour: 288,000 (Btu per day) ÷ 24 (hours in aday) = 12,000

So, a "1-ton" air-conditioner would have a ratingof 12,000 Btu per hour.

PRESSURE

PRESSURE is defined as a force per unit area. It isusually measured in pounds per square inch (psi).Pressure may be in one direction, several directions, orin all directions, as shown in figure 6-3. The ice (solid)exerts pressure downward. The water (fluid) exertspressure on all wetted surfaces of the container. Gasesexert pressure on al I inside surfaces of their containers.

Pressure is usually measured on gauges that haveone of two different scales. One scale is read as somany pounds per square inch gauge (psig) andindicates the pressure above atmospheric pressuresurrounding the gauge. The other type of scale is readas so many pounds per square inch absolute (psia) andindicates the pressure above absolute zero pressure (aperfect vacuum).

Atmospheric Pressure

Atmospheric pressure is the pressure of the weightof air above a point on, above, or under the earth. Atsea level, ATMOSPHERIC PRESSURE is 14.7 psia,as shown in figure 6-4. As one ascends, theatmospheric pressure decreases about 1.0 psi for every2,343 feet. Below sea level in excavations anddepressions, atmospheric pressure increases.Pressures underwater differ from those under air onlybecause the weight of the water must be added to thepressure of the air.

Figure 6-3.—Exertion of pressures.

6-4

Figure 6-4.—Atmospheric pressure.

Scale Relationships

A relationship exists between the readings of agauge calibrated in psig and calibrated in psia. Asshown in figure 6-5, when the psig gauge reads 0, the

ABSOLUTE GAUGE INCHES INCHESSCALE SCALE O F O F(PSIA) (PSIG) MERCURY WATER

4 4 . 7 3 0 NOT USED NOT USED2 4 . 7 1 0 NOT USED NOT USED1 4 . 7 0 0 0

0 NOT USED - 3 0 - 4 0 8

UTB2f605

Figure 6-5.—Pressure relationship.

psia gauge reads the atmospheric pressure (14.7 psia atsea level). In other words, the psia reading equals thepsig reading plus the atmospheric pressure (7.7 psia at16,400 feet), or, a psig reading equals the psia readingminus the atmospheric pressure.

For pressure less than the atmospheric pressure(partial vacuums), a measuring device with a scalereading in inches of mercury (Hg) or in inches of water(H2O) is used. A perfect vacuum is equal to -30 inchesof mercury or -408 inches of water (fig. 6-5). Inrefrigeration work, pressures above atmospheric aremeasured in pounds per square inch, and pressuresbelow atmospheric are measured in inches of mercury.

Effects of Pressure on Gases

The exertion of pressure on a substance with aconstant temperature decreases its volume inproportion to the increase of pressure. For example,suppose that a given amount of gas is placed in acylinder that is sealed on one end and has a movablepiston on the other end. When 60 psi of absolutepressure is exerted on the piston, as shown in view A offigure 6-6, the volume of the gas is compressed to 3cubic feet. When 90 psi of absolute pressure is exertedon the piston, as shown in view B, the volume of the gasis compressed to 1.5 cubic feet. Finally, when 180 psiof absolute pressure is exerted on the piston, as shownin view C, the volume of the gas is compressed to 1cubic foot. Thus, if a given amount of gas is confinedin a container and subject to changes of pressure, itsvolume changes, so the product of volume multipliedby absolute pressure is always the same.

Pressure has a relationship to the boiling point of asubstance There is a definite temperature at which aliquid boils for everv definite pressure exerted upon it.

Figure 6-6.—Pressure-volume relationship.

6-5

For instance, water boils at 212°F at atmosphericpressure (14.7 psia), as shown in view A, figure 6-7.The same water boils at 228°F if the pressure is raised5.3 psig (20 psia), as shown in view B, figure 6-7. Onthe other hand, the same water boils at 32°F in a partialvacuum of 29.74 inches of mercury (Hg), as shown infigure 6-8.

Figure 6-7.—A. Water boils at atmospheric pressure; B.

Water boils at 20-psia absolute pressure.

Figure 6-8.—Water boils quicker in a vacuum.

This effect of reduced pressure on the boilingtemperature of refrigerants makes the operation of arefr igerat ion system possible. The pressuretemperature relationship chart in figure 6-9 gives thepressures for several different refrigerants.

An increase in the temperature of a refrigerantresults in an increase in pressure, and a decrease intemperature causes a decrease in pressure. By thesame token, a decrease in pressure results in acorresponding decrease in temperature.

This means that as the pressure of a refrigerant isincreased, so is the temperature at which therefrigerant boils. Thus, by regulating the pressure ofthe refrigerant, the temperature at which evaporationtakes place and at which the latent heat of evaporationis used can be controlled.

VAPORIZATION

VAPORIZATION is the process of changing aliquid to vapor, either by evaporation or boiling. Whena glass is filled with water, as shown in figure 6-10, andexposed to the rays of the sun for a day or two, youshould note that the water level drops gradually. Theloss of water is due to evaporation. Evaporation, in thiscase, takes place only at the surface of the liquid. It isgradual, but the evaporation of the water can bespeeded up if additional heat is applied to it. In thiscase, the boiling of the water takes place throughoutthe interior of the liquid. Thus the absorption of heatby a liquid causes it to boil and evaporate.

Vaporization can also be increased by reducing thepressure on the liquid, as shown in figure 6-11.Pressure reduction lowers the temperature at whichliquid boils and hastens its evaporation. When a liquidevaporates, it absorbs heat from warmer surroundingobjects and cools them. Refrigeration by evaporationis based on this method. The liquid is allowed toexpand under reduced pressure, vaporizing andextract ing heat from the container (freezingcompartment), as it changes from a liquid to a gas.After the gas is expanded (and heated), it iscompressed, cooled, and condensed into a liquid again.

CONDENSATION

CONDENSATION is the process of changing avapor into a liquid. For example, in figure 6-12, awarm atmosphere gives up heat to a cold glass of water,causing moisture to condense out of the air and form onthe outside surface of the glass. Thus the removal ofheat from a vapor causes the vapor to condense.

6-6

141b

29.0

28.8

28.6

28.3

28.1

27.7

27.3

26.9

26.4

25.8

25.2

24.5

23.7

22.8

21.8

20.7

19.5

18.1

16.7

13.1

13.4

11.5

9 . 4

7 . 2

4 . 8

2 . 3

0 . 2

1 . 7

3 . 2

4 . 8

6 . 6

8 . 4

10.4

12328.8

28 .6

28 .3

28 .1

27 .7

27 .3

26 .9

26 .4

25 .8

25.2

24 .5

23.7

22 .8

21 .8

20 .7

19 .5

18.1

16 .6

15 .0

13 .1

11 .2

9 . 0

6 . 6

4 . 1

1 . 3

0 . 9

2 . 5

4 . 2

6 . 1

8 . 1

10.2

12.6

15 .0

P R E S S U R E T E M P E R A T U R E C H A R T

Temp °F

- 4 0 . 0

- 3 5 . 0

- 3 0 . 0

- 2 5 . 0

- 2 0 . 0

- 1 5 . 0

- 1 0 . 0

- 5 . 0

0 . 0

5 . 0

1 0 . 0

1 5 . 0

2 0 . 0

2 5 . 0

3 0 . 0

3 5 . 0

4 0 . 0

4 5 . 0

5 0 . 0

5 5 . 0

6 0 . 0

6 5 . 0

7 0 . 0

7 5 . 0

8 0 . 0

8 5 . 0

9 0 . 0

9 5 . 0

1 0 0 . 0

1 0 5 . 0

1 1 0 . 0

1 1 5 . 0

1 2 0 . 0

113

29.5

29.4

29.3

29.2

29.0

28 .8

28.7

28.4

28.2

27.9

27.5

27.2

26.7

26.3

25.7

25.1

24.4

23.7

22.9

21.9

20.9

19.8

18.6

17.3

15 .8

14.2

12 .5

10.6

8 . 6

6 . 4

4 . 0

1 . 4

0 . 7

11

28.4

28.1

27.8

27.4

27.0

26.6

26.0

25.4

24.7

23.9

23.1

22.1

21.1

19.9

18.6

17.1

15.6

13.8

12.0

9 . 9

7 . 7

5 . 2

2 . 6

0 . 1

1 .6

3 . 3

5 .0

6 .9

8 .911.1

13.4

15.9

18.5

114

26.1

25.4

24.7

23.8

22.9

21.8

20.6

19.3

17.8

16.2

14.4

12.4

10.2

7 .8

5 .1

2 .2

0 .4

2 .1

3 .9

5 .9

8 . 0

10.3

12.7

15.3

18.2

21.2

24.4

27.8

31.4

35.3

39.4

43.8

48.4

124

22.8*

20.2*

16.9*

12.7*

7.6*

1.4*

3 . 0

7 . 5

12.7

18.8

25 .9

34.1

43.5

54.1

66.2

79.7

94.9

134a

14.7

12.3

9 . 7

6 . 8

3 . 6

0 .0

2 .0

4 . 1

6 . 5

9 . 1

12.0

15.1

18.4

22 .1

26 .1

30 .4

3 5 . 0

4 0 . 0

45 .4

51 .2

57 .4

64 .0

7 1 . 1

7 8 . 6

8 6 . 7

9 5 . 2

104.3

113.9

124.1

134.9

146.3

158.4

171.1

1 211.0

8 .4

5 .5

2 .3

0 .6

2 .5

4 .5

6 . 7

9 .2

11.8

14.7

17.7

21.1

24.6

28.5

32.6

37.0

41.7

46.7

52.1

57.8

63.8

70.2

77.0

84.2

91.7

99.7

108.2

117.0

126.4

136.2

146.5

157.3

500

7 .6

4.6

1 .2

1 .2

3 .2

5 . 4

7 . 8

10.4

13.3

16.4

19.7

23.3

27.2

31.4

36.0

40.8

46.0

51.6

57.5

63.8

70.6

77.7

85.3

93.4

101.9

110.9

120.5

130.5

141.1

152.2

163.9

176.3

189.2

2 2

0 . 6

2 .6

4 .9

7 .5

10.2

13.2

16.5

20.1

24.0

28.3

32.8

37.8

43.1

48.8

54.9

61.5

68.5

76.1

84.1

92.6

101.6

111.3

121.4

132.2

143.7

155.7

168.4

181.8

196.0

210.8

226.4

242.8

260.0

5 0 2

4.1

6.5

9.2

12.1

15.3

18.8

22.6

26.7

31.1

35.9

41.0

46.5

52.5

58.8

65.6

72.8

80.5

88.7

97.4

106.6

116.4

127.6

137.6

149.1

161.2

174.0

187.4

201.4

216.2

231.7

247.9

264.9

282.7

1254.9

10.6

17.4

25.6

35 .1

46.3

59.2

74.1

91.2

110.6

132.8

157.8

186.0

217.5

252.7

291.6

334.3

Vapor pressures in psig, except (*) which are inches of mercury (Hg).

Figure 6-9.—Pressure temperature chart.

UTBf609

An increase in pressure on a confined vapor alsocauses the vapor to change to a liquid. This fact isshown in figure 6-13. When the compressor increases

The condenser removes the superheat, latent heat ofvaporization, and, in some cases, sensible heat fromthe refrigerant.

the pressure on the vapor, the condensing vaporchanges to a liquid and gives up heat to the coolersurrounding objects and atmosphere.

Q1.

These conditions exist when the vaporizedrefrigerant is compressed by the compressor of arefrigeration system and forced into the condenser. Q2.

When two substances of different temperaturesare brought in contact with each other, heat willflow from the colder substance to the warmersubstance. True/False.

What is specific heat?

6-7

Figure 6-12.—Condensation of moisture on a glass of coldwater.

Figure 6-10.—Normal surface evaporation.

Figure 6-11.—Evaporation by pressure reduction.

Q3. What is the difference between "sensible heat"

and "latent heat"? Figure 6-13.—Pressure causes a vapor to condense.

Q4. What is the atmospheric pressure at 4,686 feet?Mechanical refr igerat ion systems are an

arrangement of components in a system that puts the

theory of gases into practice to provide artificial

cooling. To do this, you must provide the following:

(1) a metered supply of relatively cool liquid under

pressure; (2) a device in the space to be cooled that

operates at reduced pressure so that when the cool,

pressurized liquid enters, it will expand, evaporate,

and take heat from the space to be cooled; (3) a meansof repressurizing (compressing) the vapor; and (4) a

means of condensing it back into a liquid, removing its

Q5. Exertion of pressure on a substance with a

constant pressure does what to the substance?

Q4. Removal of heat from a vapor causes what

change to occur?

MECHANICAL REFRIGERATIONSYSTEMS

Learning Objective: Identify and understand differenttypes of refrigeration system components and theiroperation.

6-8

superheat, latent heat of vaporization, and some of itssensible heat.

Every mechanical refrigeration system operates attwo different pressure levels. The dividing line isshown in figure 6-14. The line passes through thedischarge valves of the compressor on one end andthrough the orifice of the metering device or expansionvalve on the other.

The high-pressure side of the refrigeration systemcomprises all the components that operate at or abovecondensing pressure. These components are thedischarge side of the compressor, the condenser, thereceiver, and all interconnected tubing up to themetering device or expansion valve.

The low-pressure side of a refrigeration systemconsists of all the components that operate at or belowevaporating pressure. These components comprise thelow-pressure side of the expansion valve, theevaporator, and all the interconnecting tubing up toand including the low side of the compressor.

Refrigeration mechanics call the pressure on the The refrigerant low-pressure vapor drawn from thehigh side discharge pressure, head pressure, or evaporator by the compressor through the suction line,high-side pressure. On the low side, the pressure is in turn, is compressed by the compressor to acalled suction pressure or low-side pressure. high-pressure vapor, which is forced into the

The refrigeration cycle of a mechanicalrefrigeration system may be explained by using figure6-14. The pumping action of the compressor (1) drawsvapor drawn from the evaporator (2). This actionreduces the pressure in the evaporator, causing theliquid particles to evaporate. As the liquid particlesevaporate, the evaporator is cooled. Both the liquidand vapor refrigerant tend to extract heat from thewarmer objects in the insulated refrigerator cabinet.The ability of the liquid to absorb heat as it vaporizes isvery high in comparison to that of the vapor. As theliquid refrigerant is vaporized, the low-pressure vaporis drawn into the suction line by the suction action ofthe compressor (1). The evaporation of the liquidrefrigerant would soon remove the entire refrigerantfrom the evaporator if it were not replaced. Thereplacement of the liquid refrigerant is usuallycontrolled by a metering device or expansion valve (3).This device acts as a restrictor to the flow of the liquidrefrigerant in the liquid line. Its function is to changethe high-pressure, subcooled liquid refrigerant tolow-pressure, low-temperature liquid particles, whichwill continue the cycle by absorbing heat.

Figure 6-14.—Refrigeration cycle.

6-9

condenser (4). In the condenser, the high-pressurevapor condenses to a liquid under high pressure andgives up heat to the condenser. The heat is removedfrom the condenser by the cooling medium of air orwater. The condensed liquid refrigerant is then forcedinto the liquid receiver (5) and through the liquid lineto the expansion valve by pressure created by thecompressor, making a complete cycle.

Although the receiver is indicated as part of therefrigeration system in figure 6-14, it is not a vitalcomponent. However, the omission of the receiverrequires exactly the proper amount of refrigerant in thesystem. The refrigerant charge in systems withoutreceivers is to be considered critical, as any variationsin quantity affects the operating efficiency of the unit.

The refrigeration cycle of any refrigeration systemmust be clearly understood by a mechanic beforerepairing the system. Knowing how a refrigerantworks makes it easier to detect faults in a refrigerationsystem.

COMPONENTS

The refrigeration system consists of four basiccomponents - t h e compressor, the condenser, theliquid receiver, the evaporator, and the control devices.These components are essential for any system tooperate on the principles previously discussed.Information on these components is described in thefollowing sections.

Compressors

Refrigerat ion compressors have but onepurpose—to withdraw the heat-laden refrigerant vaporfrom the evaporator and compress the gas to a pressurethat will liquefy in the condenser. The designs ofcompressors vary, depending upon the application andtype of refrigerant. There are three types ofcompressors classified according to the principle ofoperation— reciprocating, rotary, and centrifugal.

You may recall that material on compressors waspresented in chapter 6, Utilitiesman Basic, volume 1.They will not be explained further here except todiscuss the special methods used to seal compressorsto prevent escape of refrigerant. Many refrigeratorcompressors have components besides those normallyfound on compressors, such as unloaders, oil pumps,mufflers, and so on. These devices are too complicatedto explain here. Before repairing any compressor,check the manufacturer's manual for an explanation oftheir operation, adjustment, and repair.

EXTERNAL DRIVE COMPRESSOR.—Anexternal drive or open-type compressor is boltedtogether. Its crankshaft extends through the crankcaseand is driven by a flywheel (pulley) and belt, or it canbe driven directly by an electric motor. A leakproofseal must be maintained where the crankshaft extendsout of the crankcase of an open-type compressor. Theseal must be designed to hold the pressure developedinside of the compressor. It must prevent refrigerantand oil from leaking out and prevent air and moisturefrom entering the compressor. Two types of seals areused—the stationary bellows seal and the rotatingbellows seal.

An internal stationary crankshaft seal shown infigure 6-15 consists of a corrugated thin brass tube(seal bellows) fastened to a bronze ring (seal guide) atone end and to the flange plate at the other. The flangeplate is bolted to the crankcase with a gasket betweenthe two units. A spring presses the seal guide mountedon the other end of the bellows against a seal ringpositioned against the shoulder of the crankshaft. Asthe pressure builds up in the crankcase, the bellowstend to lengthen, causing additional force to press theseal guide against the seal ring. Oil from the crankcaselubricates the surfaces of the seal guide and seal ring.This forms a gastight sea whether the compressor isoperating or idle.

Figure 6-15.—An internal stationary bellows crankshaft seal.

6-10

An external stationary bellows crankshaft seal isshown in figure 6-16. This seal is the same as theinternal seal, except it is positioned on the outside ofthe crankcase.

An external rotating bellows crankcase seal isshown in figure 6-17. This seal turns with thecrankshaft. This seal also consists of a corrugated thinbrass tube (seal bellows) with a seal ring fastened toone end and a seal flange fastened to the other. A sealspring is enclosed within the bellows. The completebellows assembly slips on the end of the crankshaft andis held in place by a nut. The seal ring that is the innerportion of the bellows is positioned against anonrotating seal fastened directly to the crankcase.During operation, the complete bellows assemblyrotates with the shaft, causing the seal ring to rotateagainst the stationary seal. The pressure of the sealspring holds the seal ring against the seal. Theexpansion of the bellows caused by the pressure fromthe crankcase also exerts pressure on the seal ring.Because of this design, double pressure is exertedagainst the seal ring to provide a gastight seal.

HERMETIC COMPRESSOR.—In thehermetically sealed compressor, the electric motor andcompressor are both in the same airtight (hermetic)housing and share the same shaft. Figure 6-18 shows ahermetically sealed unit. Note that after assembly, thetwo halves of the case are welded together to form anairtight cover. Figure 6-19 shows an accessible type ofhermetically sealed unit. The compressor, in this case,is a double-piston reciprocating type. Othercompressors may be of the centrifugal or rotary types.

Figure 6-16.—An external stationary bellows crankshaft seal.

Figure 6-17.—An external rotating bellows crankcase seal.

Cooling and lubrication are provided by the circulatingoil and the movement of the refrigerant vaporthroughout the case.

The advantages of the hermetically sealed unit(elimination of pulleys, belts and other couplingmethods, elimination of a source of refrigerant leaks)are offset somewhat by the inaccessibility for repairand generally lower capacity.

Condensers

The condenser removes and dissipates heat fromthe compressed vapor to the surrounding air or water to

Figure 6-18.—Hermetic compressor.

6-11

Figure 6-19.—A cutaway view of a hermetic compressor and

motor.

condense the refrigerant vapor to a liquid. The liquidrefrigerant then falls by gravity to a receiver (usuallylocated below the condenser), where it is stored, andavailable for future use in the system.

There are three basic types of condensers—air-cooled, water-cooled, and evaporative. The firsttwo are the most common, but the evaporative typesare used where low-quality water and its disposal makethe use of circulating water-cooled types impractical.

AIR-COOLED CONDENSERS.—The con-struction of air-cooled condensers makes use ofseveral layers of small tubing formed into flat cells.The external surface of this tubing is provided with finsto ease the transfer of heat from the condensingrefrigerant inside the tubes to the air circulated throughthe condenser core around the external surface of thetubes (fig. 6-20). Condensation takes place as therefrigerant flows through the tubing, and the liquidrefrigerant is discharged from the lower ends of thetubing coils to a liquid receiver on the condensing unitassembly.

W A T E R - C O O L E D C O N D E N S E R S .—Water-cooled condensers are of the multipass shell andtube type, with circulating water flowing through thetubes. The refrigerant vapor is admitted to the shell

Figure 6-20.—Air-cooled condenser mounted on a compressor unit.

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and condensed on the outer surfaces of the tubes (fig.6-21).

The condenser is constructed with a tube sheetbrazed to each end of a shell. Copper-nickel tubes areinserted through drilled openings in the tube sheet andare expanded or rolled into the tube sheet to make agastight seal. Headers, or water boxes, are bolted to thetube sheet to complete the waterside of the condenser.Zinc-wasting bars are installed in the water boxes tominimize electrolytic corrosion of the condenser parts.

A purge connection with a valve is at the topside ofthe condenser shell to allow manual release of anyaccumulated air in the refrigerant circuit.

The capacity of the water-cooled condenser isaffected by the temperature of the water, quantity ofwater circulated, and the temperature of the refrigerantgas. The capacity of the condenser varies wheneverthe temperature difference between the refrigerant gasand the water is changed. An increased temperaturedifference or greater flow of water increases thecapacity of the condenser. The use of colder water cancause the temperature difference to increase.

E V A P O R A T I V E C O N D E N S E R S .—Anevaporative condenser operates on the principle thatheat can be removed from condensing coils byspraying them with water or letting water drip ontothem and then forcing air through the coils by a fan.

This evaporation of the water cools the ‘coils andcondenses the refrigerant within.

Liquid Receiver

A liquid receiver as shown at position (5) on figure6-14, serves to accumulate the reserve liquidrefrigerant, to provide a storage for off-peak operation,and to permit pumping down of the system. Thereceiver also serves as a seal against the entrance ofgaseous refrigerant into the liquid line. When stopvalves are provided at each side of the receiver forconfinement of the liquid refrigerant, a pressure reliefvalve is generally installed between the valves in thereceiver and condenser equalizing line to protect thereceiver against any excessive hydraulic pressurebeing built up.

Evaporators

The evaporator is a bank or coil of tubing placedinside the refrigeration space. The refrigerant is at alow-pressure and low-temperature liquid, as it entersthe evaporator.

As the refr igerant circulates through theevaporator tubes, it absorbs its heat of vaporizationfrom the surrounding space and substances. Theabsorption of this heat causes the refrigerant to boil.As the temperature of the surrounding space (and

Figure 6-21.—Water-cooled condenser.

6-13

contents) is lowered, the liquid refrigerant graduallychanges to a vapor. The refrigerant vapor then passesinto the suction line by the action of the compressor.

Most evaporators are made of steel, copper, brass,stainless steel, aluminum, or almost any other kind ofrolled metal that resists the corrosion of refrigerantsand the chemical action of the foods.

Evaporators are mainly of two types—dry orflooded. The inside of a dry evaporator refrigerant isfed to the coils only as fast as necessary to maintain thetemperature wanted. The coil is always filled with amixture of liquid and vapor refrigerant. At the inletside of the coil, there is mostly liquid; the refrigerantflows through the coil (as required); it is vaporizeduntil, at the end, there is nothing but vapor. In a floodedevaporator, the evaporator is always filled with liquidrefrigerant. A float maintains liquid refrigerant at aconstant level. As fast as the liquid refrigerantevaporates, the float admits more liquid, and, as aresult, the entire inside of the evaporator is floodedwith liquid refrigerant up to a certain level determinedby the float.

The two basic types of evaporators are furtherclassified by their method of evaporation, either directe x p a n d i n g o r i n d i r e c t e x p a n d i n g . I n t h edirect-expanding evaporator, heat is transferreddirectly from the refrigerating space through the tubesa n d a b s o r b e d b y t h e r e f r i g e r a n t . I n t h eindirect-expanding evaporator, the refrigerant in theevaporator is used to cool some secondary medium,other than air. This secondary medium or refrigerantmaintains the desired temperature of the space.Usually brine, a solution of calcium chloride is used asthe secondary refrigerant.

Natural convection or forced-air circulation isused to circulate air within a refrigerated space. Airaround the evaporator must be moved to the storedfood so that heat can be extracted, and the warmer airfrom the food returned to the evaporator. Naturalconvection can be used by installing the evaporator inthe uppermost portion of the space to be refrigerated,so heavier cooled air will fall to the lower food storageand the lighter food-warmed air will rise to theevaporator. Forced-air circulation speeds up this

to ensure all areas are cooled.process and is usually used in large refrigerated spaces

Control Devices

To maintain correct operating conditions, controldevices are needed in a refrigeration system. Some ofthe control devices are discussed in this chapter.

METERING DEVICES.—Metering devices,such as expansion valves and float valves, control theflow of liquid refrigerant between the high side and thelow side of the system. It is at the end of the linebetween the condenser and the evaporator. Thesedevices are of five different types: an automaticexpansion valve (also known as a constant-pressureexpansion valve), a thermostatic expansion valve,low-side and high-side float valves, and a capillarytube.

Automatic Expansion Valve.—An automaticexpansion valve (fig. 6-22) maintains a constantpressure in the evaporator. Normally this valve is usedonly with direct expansion, dry type of evaporators. Inoperation, the valve feeds enough liquid refrigerant tothe evaporator to maintain a constant pressure in thecoils. This type of valve is generally used in a systemwhere constant loads are expected. When a largevariable load occurs, the valve will not feed enoughrefrigerant to the evaporator under high load and willoverfeed the evaporator at low load. Compressordamage can result when slugs of liquid enter thecompressor.

Thermostatic Expansion Valve.—Beforediscussing the thermostatic expansion valve, let’sexplain the term SUPERHEAT. A vapor gas issuperheated when its temperature is higher than theboiling point corresponding to its pressure. When theboiling point begins, both the liquid and the vapor areat the same temperature. But in an evaporator, as thegas vapor moves along the coils toward the suctionline, the gas may absorb additional heat and itstemperature rises. The difference in degrees betweenthe saturation temperature and the increasedtemperature of the gas is called superheat.

A thermostatic expansion valve (fig. 6-22) keeps aconstant superheat in the refrigerant vapor leaving thecoil. The valve controls the liquid refrigerant, so theevaporator coils maintain the correct amount ofrefrigerant at all times. The valve has a power elementthat is activated by a remote bulb located at the end ofthe evaporator coils. The bulb senses the superheat atthe suction line and adjusts the flow of refrigerant intothe evaporator. As the superheat increases (suctionline), the temperature, and therefore the pressure, inthe remote bulb also increases. This increasedpressure, applied to the top of the diaphragm, forces itdown along with the pin, which, in turn, opens thevalve, admitting replacement refrigerant from thereceiver to flow into the evaporator. This replacementhas three effects. First, it provides additional liquid

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Figure 6-22—A. Thermostatic expansion valve; B. Automatic expansion valve.

refrigerant to absorb heat from the evaporator.Second, it applies higher pressure to the bottom of thediaphragm, forcing it upward, tending to close thevalve. And third, it reduces the degree of superheat byforcing more refrigerant through the suction line.

Low-Side Float Expansion Valve.—Thelow-side float expansion valve (fig. 6-23) controls theliquid refrigerant flow where a flooded evaporator isused. It consists of a ball float in either a chamber orthe evaporator on the low-pressure side of the svstem.

The float actuates a needle valve through a levermechanism. As the float lowers, refrigerant entersthrough the open valve; when it rises, the valve closes.

High-Side Float Expansion Valve.—In ahigh-side float expansion valve (fig. 6-24), the valvefloat is in a liquid receiver or in an auxiliary containeron the high-pressure side of the system. Refrigerantfrom the condenser flows into the valve andimmediately opens it, allowing refrigerant to expandand pass into the evaporator. Refrigerant charge iscritical. An overcharge of the system floods back anddamages the compressor. An undercharge results in acapacity drop.

Figure 6-23.—A low-side float expansion valve. Figure 6-24.—A high-side float expansion valve.

6-15

Capillary Tube.—The capillary tube consists of along tube of small diameter. It acts as a constantthrottle on the refrigerant. The length and diameter ofthe tube are important; any restrictions cause trouble inthe system. It feeds refrigerant to the evaporator as fastas it is produced by the condenser. When the quantityof refrigerant in the system is correct or the charge isbalanced, the flow of refrigerant from the condenser tothe evaporator stops when the compressor unit stops.When the condensing unit is running, the operatingcharacteristics of the capillary tube equippedevaporator are the same as if it were equipped with ahigh-side float.

The capillary tube is best suited for householdboxes, such as freezers and window air-conditioners,where the refrigeration load is reasonably constant andsmall horsepower motors are used.

Accessory Devices

The four basic or major components of arefrigeration system just described are enough for arefrigeration unit to function. However, additionaldevices, such as the receiver already described, makefor a smoother and more controlled cycle. Some of theaccessory devices used on a refrigeration unit aredescribed in this section. Before proceeding, take aclose look at figure 6-25 that shows one type ofrefrigeration system with additional devices installed.

Some of the devices and their functions are explainedt o h e l p y o u u n d e r s t a n d i n s t a l l a t i o n a n dtroubleshooting of a refrigeration unit.

RELIEF VALVE.—A refrigeration system is asealed system in which pressures vary. Excessivepressures can cause a component of the system toexplode. The National Refrigeration Code makes theinstal lat ion of a rel ief valve mandatory. Aspring-loaded relief valve is most often used and it isinstalled in the compressor discharge line between thecompressor discharge connection and the dischargeline stop valve to protect the high-pressure side of thesystem. No valves can be installed between thecompressor and the relief valve. The discharge fromthe relief valve is led to the compressor suction line.

DISCHARGE PRESSURE GAUGE ANDTHERMOMETER. —A discharge pressure gaugeand thermometer are installed in the compressordischarge line (liquid line) to show the pressure andtemperature of the compressed refrigerant gas. Thetemperature indicated on the gauge is always higherthan that corresponding to the pressure when thecompressor is operating.

COMPRESSOR MOTOR CONTROLS.—Thestarting and stopping of the compressor motor isusually controlled by either a pressure-actuated ortemperature-actuated motor control. The operation ofthe pressure motor control depends on the relationship

Figure 6-25.—A basic refrigeration system.

6-16

between pressure and temperature. A pressure motorcontrol is shown in figure 6-26. The device consists ofa low-pressure bellows, or, in some cases, a low-pressure diaphragm, connected by a small diametertube to the compressor crankcase or to the suction line.The pressure in the suction line or compressorcrankcase is transmitted through the tube and actuatesthe bellows or diaphragm. The bellows moveaccording to the pressure, and its movement causes anelectric switch to start (cut in) or stop (cut out) thecompressor motor. Adjustments can be made to thestart and stop pressures under the manufacturer’sinstruction. Usually the cutout pressure is adjusted tocorrespond to a temperature a few degrees below thedesired evaporator coil temperature, and the cut-inpressure is adjusted to correspond to the temperature ofthe coil.

The tem perature-actuated motor control is similarto the pressure device. The main difference is that atemperature-sensing bulb and a capillary tube replacethe pressure tube. The temperature motor control cutsin or cuts out the compressor according to thetemperature in the cooled space.

The refrigeration system may also be equippedwith a high-pressure safety cutout switch that shuts offthe power to the compressor motor when the high-sidepressure exceeds a preset limit.

SOLENOID STOP VALVES.—Solenoid stopvalves, or magnetic stop valves, control gas or liquid

flow. They are most commonly used to control liquidrefrigerant to the expansion valve but are usedthroughout the system. The compressor motor andsolenoid stop valve are electrically in parallel; that is,the electrical power is applied or removed from both atthe same time. The liquid line is open for passage ofrefrigerant only when the compressor is in operationand the solenoid is energized. A typical solenoid stopvalve is shown in figure 6-27.

Improper operation of these valves can be causedby a burned-out solenoid coil or foreign materiallodged between the stem and the seat of the valve,allowing fluid to leak. Carefully check the valvebefore replacing or discarding. The valve must beinstalled so that the coil and plunger are in a truevertical position. When the valve is cocked, theplunger wi II not reseat properly, causing refrigerantleakage.

THERMOSTAT SWITCH.—Occasionally, athermostat in the refrigerated space operates a solenoidstop valve, and the compressor motor is controlledindependently by a low-pressure switch. The solenoidcontrol switch, or thermostat, makes and breaks theelectrical circuit, thereby controlling the liquidrefrigerant to the expansion valve. The control bulb ischarged with a refrigerant so that temperature changesof the bulb itself produce like changes in pressurewithin the control bulb. These pressure changes aretransmitted through the tubing to the switch powerelement to operate the switch. The switch opens thecontacts and thus releases the solenoid valve, stoppingthe flow of refrigerant to the cooling coil when thetemperature of the refrigerated space has reached thedesired point. The compressor continues to operateuntil it has evacuated the evaporator. The resulting low

Figure 6-26.—Pressure-actuated motor control. Figure 6-27.—A solenoid stop valve.

6-17

pressure in the evaporator then activates thelow-pressure switch, which stops the compressor. Asthe temperature rises, the increase in bulb pressurecloses the switch contacts, and the refrigerant issupplied to the expansion valve.

LIQUID LINE.—The refrigerant accumulated inthe bottom of the receiver shell is conveyed to thecooling coils through the main refrigerant liquid line.A stop valve and thermometer are usually installed inthis line next to the receiver. Where the sight-flowindicator, dehydrator, or filter-drier is close to thereceiver, the built-in shutoff valves may be usedinstead of a separate shutoff valve.

L I Q U I D L I N E F I L T E R - D R I E R O RDEHYDRATOR. —A liquid line filter-drier (fig.6-28) prevents or removes moisture, dirt, and otherforeign materials from the liquid line that would harmthe system components and reduce efficiency. Thistank like accessory offers some resistance to flow. and,for this reason, some manufacturers install it in abypass line. A filter-drier consists of a tubular shellwith strainers on the inlet and outlet connections toprevent escape of drying material into the system.Some filter-driers are equipped with a sight-glassindicator, as shown in figure 6-28. A dehydrator issimilar to a filter-drier, except that it mainly removesmoisture.

Figure 6-28.—A liquid line filter-drier with sight-glassindicator.

SIGHT-FLOW INDICATOR.—The sight-flowindicator, also known as a sight glass (fig. 6-29), is aspecial fitting provided with a gasketed glass, single ordouble port, and furnished with or without seal caps forprotection when not in use. The double-port unitpermits the use of a flashlight background. Therefrigerant may be viewed passing through the pipe todetermine the presence and amount of vapor bubbles inthe liquid that would indicate low refrigerant orunfavorable operating conditions. Some filter-driersare equipped with built-in sight-flow indicators, asshown in figure 6-29.

SUCTION LINE.—Suction pressure regulatorsare sometimes placed between the outlet of theevaporator and the compressor to prevent theevaporator pressure from being drawn down below apredetermined level despite load fluctuations. Theseregulators are usually installed in systems that requirea higher evaporator temperature than usual.

PRESSURE CONTROL SWITCHES.—Pressure control switches (fig. 6-30), often calledlow-pressure cutouts, are essentially a single-pole,single-throw electrical switch and are mainly used tocontrol starting and stopping of the compressor. Thesuction pressure acts on the bellows of the powerelement of the switch and produces movement of alever mechanism operating electrical contacts. A risein pressure closes the switch contacts and therebycompletes the circuit of the motor controller, which, inturn, starts the compressor automatically. As theoperation of the compressor gradually decreases thesuction pressure, the movement of the switch linkage

Figure 6-29.—Sight-flow indicators with different types ofconnections.

6-18

reverses until the contacts are separated at a pre-determined low-suction pressure, thus breaking themotor controller circuit and stopping the compressor.

SUCTION LINE FILTER-DRIER.—Somesystems include a low-side filter-drier (fig. 6-31) at thecompressor end of the suction line. The filter-drierused in the suction line should offer little resistance toflow of the vaporized refrigerant, as the pressuredifference between the pressure in the evaporator andthe inlet of the compressor should be small. Thesefilter-driers function to remove dirt, scale, andmoisture from the refrigerant before it enters thecompressor.

G A U G E S A N D T H E R M O M E T E R S .—Between the suction line stop valve and thecompressor, a pressure gauge and thermometer may beprovided to show the suction conditions at which thecompressor is operating. The thermometer shows ah i g h e r t e m p e r a t u r e t h a n t h e t e m p e r a t u r ecorresponding to the suction pressure indicated on thegauge, because the refrigerant vapor is superheatedduring its passage from the evaporator to thecompressor.

ACCUMULATORS AND OIL SEPARA-TORS.—Liquid refrigerant must never be allowed toenter the compressor. Liquids are noncompressible; inother words, their volume remains the same whencompressed. An accumulator (fig. 6-32) is a small tankaccessory; that is, a safety device designed to preventliquid refrigerant from flowing into the suction lineand into the compressor. A typical accumulator has an

Figure 6-30.—Pressure type cut-in, cutout control switch.

Figure 6-31.—A suction line filter-drier.

outlet at the top. Any liquid refrigerant that flows intothe accumulator is evaporated, and then the vapor willflow into the suction line to the compressor.

Oil from the compressor must not move into therest of the refrigeration system. Oil in the lines andevaporator reduces the efficiency of the system. An oilseparator (fig. 6-33) is located between the compressordischarge and the inlet of the condenser. The oilseparator consists of a tank or cylinder with a series ofbaffles and screens, which collect the oil. This oilsettles to the bottom of the separator. A floatarrangement operates a needle valve, which opens areturn line to the compressor crankcase.

Q7.

Q8.

Q9.

Q10.

Q11.

Q12.

What are the three types of compressors used inrefrigeration systems?

What is the difference between the internal andexternal bellows crankshaft seal?

What are the two drawbacks of a hermeticcompressor?

What are the two primary types of evaporators?

A capillary tube-metering device is mostcommonly used on what type of refrigerationequipment?

What is the function of a sight-flow indicator?

REFRIGERANTS

Learning Objective: Understand and identifyclassification of common refrigerants and theirapplication. Understand the requirements for ozoneprotection and the Clean Air Act.

Figure 6-32.—Accumulator location.

6-19

Figure 6-33.—A cutaway view of an oil separator.

Refrigerants are fluids that change their state uponthe application or removal of heat within a system and,in this act of change, absorb or release heat to or froman area or substance. Many different fluids are used asrefrigerants. In recent years, the most common hasbeen air, water, ammonia, sulfur dioxide, carbondioxide, and methylchloride.

Today, there are three specific types of refrigerantsused in refrigeration and air-conditioning systems—( 1)Chlorofluorocarbons or CFCs, such as R-11, R-12, andR-114; (2) Hydrochlorofluorocarbons or HCFCs, suchas R-22 or R-123; and (3) Hydrofluorocarbons or HFCs,such as R-134a . Al l these re f r ige ran t s a re"halogenated," which means they contain chlorine,fluorine, bromine, astatine, or iodine.

Refrigerants, such as Dichlorodifluoromethane(R-12), Monochlorodifluoromethane (R-22), andRefrigerant 502 (R-502), are called PRIMARYREFRIGERANTS because each one changes its stateupon the application or absorption of heat, and, in thisact of change, absorbs and extracts heat from the areaor substance.

The primary refrigerant is so termed because itacts directly upon the area or substance, although it

may be enclosed within a system. For a primaryrefrigerant to cool, it must be placed in a closed systemin which it can be controlled by the pressure imposedupon it. The refrigerant can then absorb at thetemperature ranges desired. If a primary refrigerantwere used without being controlled, it would absorbheat from most perishables and freeze them solid.

SECONDARY REFRIGERANTS are substances,such as air, water, or brine. Though hot refrigerants inthemselves, they have been cooled by the primaryrefrigeration system; they pass over and around theareas and substances to be cooled; and they arereturned with their heat load to the primaryrefrigeration system. Secondary refrigerants pay offwhere the cooling effect must be moved over a longdistance and gastight lines cost too much.

Refrigerants are classified into groups. TheNational Refrigeration Safety Code catalogs allrefrigerants into three groups—Group I – safest of therefrigerants, such as R-12, R-22, and R-502; Group II –toxic and somewhat flammable, such as R-40 (Methylchloride) and R-764 (Sulfur dioxide); Group III –flammable refrigerants, such as R-170 (Ethane) andR-290 (Propane).

R-12 DICHLORODIFLUOROMETHANE(CC12F2)

Dichlorodifluoromethane, commonly referred toas R-12, is colorless and odorless in concentrations ofless than 20 percent by volume in air. In higherconcentrations, its odor resembles that of carbontetrachloride. I t is nontoxic, noncorrosive,nonflammable, and has a boiling point of -21.7°F(-29°C) at atmospheric pressure.

WARNING

Because of its low-boiling point atatmospheric pressure, it prevents liquidR12 from contacting the eyes because ofthe possibility of freezing.

One hazard of R-12 as a refrigerant is the healthrisk should leakage of the vapor come into contact withan open flame of high temperature (about 1022°F) andbe decomposed into phosgene gas, which is highlytoxic. R-12 has a relatively low latent heat value, and,in smaller refrigerating machines, this is an advantage.R-12 is a stable compound capable of undergoing thephysical changes without decomposition to which it is

6-20

commonly subjected in service. The cylinder code

color for R-12 is white.

R-22 MONOCHLORODIFLUOROME-THANE (CHCIF2)

Monochlorodifluoromethane, normally calledR-22, is a synthetic refrigerant developed forrefrigeration systems that need a low-evaporatingtemperature, which explains its extensive use inhousehold refrigerators and window air conditioners.R-22 is nontoxic, noncorrosive, nonflammable, andhas a boiling point of -41°F at atmospheric pressure.R-22 can be used with reciprocating or centrifugalcompressors. Water mixes readily with R-22, so largeramounts of desiccant are needed in the filter-driers todry the refrigerant. The cylinder code color for R-22 is

green.

R-502 REFRIGERANT(CHCIF2/CCIF2CF3)

R-502 is an azeotropic mixture of 48.8 percentR-22 and 51.2 percent R-115. Azeotropic refrigerantsare liquid mixtures of refrigerants that exhibit aconstant maximum and minimum boiling point. Thesemixtures act as a single refrigerant. R-502 isnoncorrosive, nonflammable, practically nontoxic,and has a boiling point of -50°F at atmosphericpressure. This refrigerant can only be used withreciprocating compressors. It is most often used inrefrigeration applications for commercial frozen foodequipment, such as frozen food walk-in refrigerators,frozen food display cases, and frozen food processingplants. The cylinder color code for R-502 is orchid.

R-134a TETRAFLUOROETHANE(CH2FCF3)

R-134a, tetrafluoroethane, is very similar to R-12,the major difference is that R-134a has no harmfulinfluence on the ozone layer of the earth's atmosphereand is a replacement for R-12 applicat ions.Noncorrosive, nonflammable, and nontoxic, it has aboiling point of -15°F at atmospheric pressure. Usedfor medium-temperature applications, such as airconditioning and commercial refrigeration, thisrefrigerant is now used in automobile air-conditioners.

The cylinder color code for R-134a is light (sky) blue.

ADDITIONAL REFRIGERANTS

In addit ion to the previously mentionedrefrigerants, other less common refrigerants are usedin a variety of applications.

R-717 Ammonia (NH3)

Ammonia, R-717, is commonly used in industrialsystems. It has a boiling point of -28°F at atmosphericpressure. This property makes it possible to haverefrigeration at temperatures considerably below zerowithout using pressure below atmospheric in theevaporator. Normally it is a colorless gas, is slightlyflammable, and, with proper portions of air, it can forman explosive mixture, but accidents are rare. Thecylinder color code for R-717 is silver.

R-125 Pentafluoroethane (CHCF5)

Pentafluoroethane, R-125, is a blend componentused in low- and medium-temperature applications.With a boiling point of -55.3°F at atmosphericpressure, R-125 is nontoxic, nonflammable, andnoncorrosive. R-125 is one replacement refrigerantfor R-502.

All refrigerants have their own characteristics. Itis extremely important to charge a system with therefrigerant specified. Use of an incorrect refrigerantcan lead to reduced efficiency, mechanical problems,and dangerous conditions.

OZONE PROTECTION AND THE CLEANAIR ACT

Several scientific studies conducted in the 1970sshowed that chlorine was a leading cause of holes inthe ozone. In 1987, 30 countries signed the MontrealProtocol, which mandated the phase out of theproduction, and eventual use, of all harmful CFCs. In1990, the most significant piece of legislation affectingthe air conditioning and refrigeration industry, theClean Air Act, was passed. Regulated by theEnvironmental Protection Agency (EPA), Title VI ofthe Clean Air Act states fully halogenated refrigerants(CFCs) will be phased out. It also calls for the phaseout of HCFCs by the year 2030. Both of these types ofrefrigerants adversely affect the atmosphere, and as ofJuly 1992, it is illegal to discharge refrigerant to theatmosphere. The production of R-12 was discontinuedin December 1995, and the production of R-11, R-113,R-114, and R-115 is scheduled to be discontinued by

6-21

January 2000. Depending on the rate of depletion ofthe ozone layer, these timetables could be accelerated.

As a result of the Clean Air Act of 1990, there hasbeen a determined effort by manufacturers to developalternative refrigerants to replace those to bediscontinued. CFCs, R-11, and R-12, primarily used inchillers, residential, and automotive refrigeration, canbe substituted with HCFC R-123 and HFC R-134a.Future replacements include HCFC R-124 in place ofCFC, R-114, in marine chillers, and HFC R-125, inplace of CFC R-502, used in stores and supermarkets.

These replacement refrigerants have slightlydifferent chemical and physical properties; thus theycannot just be "dropped" into a system designed to useCFCs. Loss of efficiency and improper operationcould be the result. When changing the refrigerant inan existing system, parts of the system specificallydesigned to operate with a CFC refrigerant may need tobe replaced or retrofitted to accommodate the newrefrigerant.

Q13. What are CFCs and HCFCs?

Q14. What can happen if improper refrigerant is usedin a refrigeration system?

Q15. What types of refrigerants are to be phased outby the Clean Air Act in 2030?

Q16. What refrigerant has been developed to replaceR-12?

REFRIGERANT SAFETY

Learning Objective: Recall the safety requirementsfor handling and storage of refrigerants and refrigerantcylinders.

Safety is always paramount and this is especiallytrue when you are working with refrigerants. Majorsafety concerns are discussed in this section.

PERSONAL PROTECTION

Since R-12, R-22, and R-502 are nontoxic, youwill not have to wear a gas mask; however, you mustprotect your eyes by wearing splashproof goggles toguard against liquid refrigerant freezing the moistureof your eyes. When liquid R-12, R-22, and R-502contact the eyes, get the injured person to the medicalofficer at once. Avoid rubbing or irritating the eyes.Give the following first aid immediately:

Drop sterile mineral oil into the eyes and irrigatethem.

Wash the eyes when irrigation continues with aweak boric acid solution or a sterile salt solutionnot to exceed 2 percent salt.

Should the refrigerant contact the skin, flush theaf fec ted a rea repea ted ly wi th wa te r . S t r iprefrigerant-saturated clothing from the body, wash theskin with water, and take the patient immediately to thedispensary. Should a person be overcome in a spacewhich lacks oxygen due to a high concentration ofrefrigerant, treat the victim as a person who hasexperienced suffocation; render assistance throughartificial respiration.

HANDLING AND STORAGE OFREFRIGERANT CYLINDERS

Handling and storage of refrigerant cylinders aresimilar to handling and storage of any other type ofcompressed gas cylinders. When handling and storingcylinders, keep the following rules in mind:

Open valves slowly; never use any tools exceptthose approved by the manufacturer.

Keep the cylinder cap on the cylinder unless thecylinder is in use.

When refrigerant is discharged from a cylinder,immediately weigh the cylinder.

Record the weight of the refrigerant remaining inthe cylinder.

Ensure only regulators and pressure gaugesdesigned for the particular refrigerant in thecylinder are used.

Do use different refrigerants in the sameregulator or gauges.

Never drop cylinders or permit them to strikeeach other violently.

Never use a lifting magnet or a sling. A cranemay be used when a safe cradle is provided tohold the cylinders.

Never use cylinders for any other purpose than tocarry refrigerants.

Never tamper with safety devices in the cylindervalves.

Never force connections that do not fit. Ensurethe cylinder valve outlet threads are the same aswhat is being connected to it.

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Never attempt to alter or repair cylinders orvalves.

Cylinders stored in the open must be protectedfrom extremes of weather and direct sunlight. Acylinder should never be exposed to temperatureabove 120°F.

Store full and empty cylinders apart to avoidconfusion.

Never store cylinders near elevators organgways.

Never store cylinders near highly flammablesubstances.

Never expose cylinders to continuous dampness,salt water, or spray.

Q17. Goggles are not required when working withrefrigerants. True/False

Q18. How often should you weigh a refrigerantcylinder?

Q19. Why are full and empty refrigerant cylindersstored separately?

REFRIGERATION EQUIPMENT

Learning Objective: Understand and recognize thebasic types of commercial and domestic refrigerationequipment.

Refrigeration equipment can be classified as eitherself-contained or remote units. Self-containedequipment houses both the insulated storagecompartments (refrigerated), in which the evaporatoris located, and an uninsulated compartment(nonrefrigerated), in which the condensing unit islocated, in the same cabinet. This type of equipmentcan be designed with a hermetically sealed,semisealed, or an open condensing unit. These unitsare completely assembled and charged at the factoryand come ready for use with little or no installationwork. Self-contained refrigerating equipment includessuch equipment as domestic refrigerators and freezers,water coolers, reach-in and walk-in refrigerators,small cold-storage plants, and ice plants.

Remote refr igerat ing equipment has thecondensing unit installed in a remote location from themain unit. These types of units are used where the heatliberated from the condenser cannot enter the spacewhere the unit is installed or space is limited forinstallation.

REACH-IN REFRIGERATORS

Reach-in refrigerators have a storage capacity of15 cubic feet or greater. At Navy installations, they areused to store perishable foods in galleys and messes.Also, at Navy hospitals and medical clinics they areused to store biologicals, serums, and other medical

Figure 6-34.—A reach-in refrigerator with a remote condensing unit.

6-23

supplies requiring temperatures between 30°F and45°F. Standard-size units most frequently used arethose with storage capacities between 15 and 85 cubicfeet. Figure 6-34 shows a typical reach-in refrigeratorwith a remote (detached) condensing unit.

Exterior finishes for reach-in refrigerators areusually of stainless steel, aluminum, or vinyl, while theinterior finishes are usually metal or plastic, and therefrigerator cabinet is insulated with board or battentype polystyrene or urethane. Reach-in refrigeratorsare normally self-contained, with an air-cooledcondenser, but in larger refrigerators, with remotecondensers, water-cooled condensers are sometimesused. A typical self-contained unit is shown in figure6-35. The evaporator is mounted in the center of theupper portion of the food compartment. In operation,warm air is drawn by the fan into the upper part of theunit cooler, where it passes over the evaporator coils, iscooled, and then is discharged at the bottom of thecooler. The air then passes up through the interior andaround the contents of the refrigerator. The cycle iscompleted when the air again enters the evaporator.The low-pressure control is set to operate theevaporator on a self-defrosting cycle, and temperatureis thus control led. Another type of control system usesboth temperature and low-pressure control or defroston each cycle. The evaporator fan is wired forcontinuous operation within the cabinet.

Figure 6-35.—A self-contained reach-in refrigerator.

Evaporators in reach-in refrigerators are generallythe unit cooler type with dry coils (fig. 6-36). Insmaller capacity refrigerators, ice-making coils,similar to those used in domestic refrigerators, areoften used as well as straight gravity coils. R-12 andR-502 are normally used in these units.

WALK-IN REFRIGERATORS

Walk-in refrigerators are normally larger thanreach-in types and are either built-in or prefabricatedsectional walk-in units. They are made in two

Figure 6-36.—A. Unit cooler in a reach-in refrigerator; B.

Dome cooler in a reach-in refrigerator.

6-24

types—one for bulk storage of fresh meats, dairyproducts , vegetables, and frui ts requir ing atemperature from 35°F to 38°F and the other for thestorage of frozen food at temperatures of 10oF orbelow. The 35°F to 38°F refrigerators are built andshipped in sections and assembled at the location theyare installed. They can be taken apart, moved, andreassembled in another area if needed. Standard-sizecoolers can be from 24 square feet up to 120 square feetin floor area. A walk-in refrigerator with reach-indoors is shown in figure 6-37.

The exterior and interiors of these units arenormally galvanized steel or aluminum. Vinyl,porcelain, and stainless steel are also used. Mostwalk-in refrigerators use rigid polyurethane board,batten, or foamed insulation between the inner andouter walls. For storage temperatures between 35°F to40°F, 3 to 4 inches of insulation is generally used. Forlow-temperature applications, 5 inches or more ofinsulation is used. These refrigerators are equippedwith meat racks and hooks to store meat carcasses.Walk-in refrigerators also have a lighting systeminside the refrigerator compartment. Most systemshave the compressor and condenser outside the mainstructure and use either a wall-mounted forced-air orgravity-type evaporator that is separated from the mainpart of the cabinet interior by a vertical baffle.

The operation of the walk-in refrigerator is similarto that of the reach-in units. The evaporator must have

Figure 6-37.—A walk-in refrigerator with reach-in doors.

sufficient capacity (Btu per hour) to handle the heatload from infiltration and product load.

DOMESTIC REFRIGERATORS

Domestic refrigerators are used in most facilitieson a Navy installation. Most domestic refrigerators areof two types—either a single door fresh foodrefrigerator or a two-door refrigerator-freezercombination, with the freezer compartment on the topportion of the cabinet, or a vertically split cabinet(side-by-side), with the freezer compartment on theleft side of the cabinet. They are completelyself-contained units and are easy to install. Mostrefrigerators use R-22 refrigerant , normallymaintaining temperatures of 0°F in the freezercompartment and about 35°F to 45°F in the refrigeratorcompartment. The Utilitiesman must be able toperform various duties in the maintenance and repairof domestic refrigerators, water coolers, and icemachines at Navy activities. This section providesinformation to aid you in handling some of the morecommon types of troubles. But let us remind you thatthe information given here is intended as a generalguide and should, therefore, be used with them a n u f a c t u r e r ' s d e t a i l e d i n s t r u c t i o n s . F o rtroubleshooting guidance, see table Y in appendix II atthe back of this TRAMAN.

Single Door Fresh Food Refrigerator

A single door fresh food refrigerator (fig. 6-38)consists of an evaporator placed either across the top orin one of the upper corners of the cabinet. The

Figure 6-38.—Single door fresh food refrigerator.

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condenser is on the back of the cabinet or in the bottomof the cabinet below the hermetic compressor. Duringoperation, the cold air from the evaporator flows bynatural circulation through the refrigerated space. Theshelves inside the cabinet are constructed so air cancirculate freely past the ends and sides, eliminating theneed for a fan. This refrigerator has a manual defrost,which requires that the refrigerator be turned offperiodically (usually overnight) to enable the buildupof frost on the evaporator to melt. Both the outside andinside finish is usually baked-on enamel. Porcelainenamel is found on steel cabinet liners. The interior ofthe unit contains the shelves, lights, thermostats, andtemperature controls.

Two-Door Refrigerator-Freezer Combination

The two-door refrigerator-freezer combination isthe most popular type of refrigerator. It is similar to thefresh food refrigerators in construction and thelocation of components except it sometimes has anevaporator for both the freezer compartment and therefrigerator compartment. Also, if it is a frost-free unit,the evaporators are on the outside of the cabinet.Because of the two separate compartments(refrigerator-freezer) and the larger capacity, thesetypes of refrigerators use forced air (fans) to circulatethe air through the inside of both compartments. Thetwo-door refrigerator also has one of the followingthree types of evaporator defrost systems: manualdefrost, automatic defrost, or frost-free.

There are two types of automatic defrosting: thehot gas system or the electric heater system. The hotgas system, through the use of solenoid valves, uses theheat in the vapor from the compressor discharge lineand the condenser to defrost the evaporator. The othersystem uses electric heaters to melt the ice on theevaporator surface.

A frost-free refrigerator-freezer (fig. 6-39) has theevaporator located outside the refr igeratedcompartment. On the running part of the cycle, air isdrawn over the evaporator and is forced into the freezerand refrigerator compartments by a fan. On the off partof the cycle, the evaporators automatically defrost.

Refrigerator-freezer cabinets are made of pressedsteel with a vinyl or plastic lining on the interior wallsurfaces and a lacquer exterior finish. Most domesticrefrigerators have urethane foam or fiber glassinsulation in the cabinet walls. The side-by-siderefrigerator-freezer arrangement has a number offeatures not found in other refrigerators. In addition to

Figure 6-39.—Frost-free refrigerator airflow diagram.

the automatic icemaker in the freezer compartment, ithas an option for a cold water dispenser, a cube orcrushed ice dispenser, and a liquid dispenser built intothe door.

WATER COOLERS AND ICE MACHINES

Water coolers provide water for drinking at atemperature under 50°F. Two types of water coolersare instantaneous and storage. The instantaneous typeonly cools water when it is being drawn; the storagetype maintains a reservoir of cooled water. Oneinstantaneous method used places coils in a floodedevaporator through which the water flows. A secondinstantaneous method uses double coils with waterflowing through the inner coil with refrigerant flowingin the space between the inner coil and the outer coil. Athird instantaneous method is to coil the tubing in awater storage tank. This allows refrigerant to flowthrough it (fig. 6-40).

Water coolers are of two basic designs—wallmounted or floor mounted. Both types are the same inconstruction and operation; the only difference is in the

6-26

Figure 6-40.—Storage type of water cooler.

method of installation. Water cooler cabinets have asheet metal housing attached to a steel framework. Thecondenser and hermetic compressor are located in thehousing base, and the evaporator is located in thecabinet depending on its type of evaporator, butnormally under the drain basin. Most water coolers usea heat exchanger or precooler, which precools the freshwater line to the evaporator, reducing coolingrequirements for the evaporator. A thermostat, whichis manually set and adjusted, is located in the coolerhousing close to the evaporator.

Automatic ice machines, similar to the unitsshown in figures 6-41 and 6-42, are often used ingalleys, barracks, gymnasiums, and other public areas.Ice machines are self-contained, automatic machines,ranging from a small unit producing 50 pounds of iceper day to a commercial unit producing 2,400 poundsof ice per day. The primary difference in the design ofthese machines is the evaporator. They automaticallycontrol water feed to the evaporator, freeze the water inan ice cube mold, heat the mold and empty the ice into astorage bin, and shut down when the storage bin is full.Floats and solenoids control water flow, and switchesoperate the storing action when ice is made. Electricalheating elements, hot water, hot gas defrosting, ormechanical devices remove the ice from the freezing

surfaces depending on the unit. Figures 6-43 and 6-44show the freezing and defrost cycle of a typical icecube machine. In recent years, many companies havebegun to manufacture their units to use HFC R-404arefrigerant instead of HCFC R-22.

Figure 6-41.—Flake or chipped-ice machine.

6-27

Figure 6-42.—A cutaway view of an automatic ice machine.

Q20.

Q21.

Q22.

Q23.

Q24.

Q25.

Q26.

What design factor makes remote refrigerationequipment different from self-contained

equipment?

Reach-in refrigerators are operated at atemperature that falls within what range, in

degrees Fahrenheit?

Reach-in refrigeration units are equipped with

what type of evaporator?

Why are walk-in refrigerators manufactured and

constructed in sections?

Domestic refrigerators come in what two design

configurations?

What are the two types of automatic defrosting inthe two-door refrigerator-freezer combination

unit?

What component of a water cooler precools the

fresh water line to the evaporator?

Q27. What design factor is the primary difference in

the different types of ice machines?

INSTALLATION OF REFRIGERATIONEQUIPMENT

Learning Object ive: Reca l l r e f r ige ra t ionrequirements and the types of installation forrefrigeration equipment.

Utilitiesman are often tasked to installationrefrigeration systems. Therefore, it is important foryou to understand the basic requirements applicable tothe installation of the various types of the equipment.

When installing a refrigeration or air-conditioningplant, you must not allow dirt, scale, sand, or moistureto enter any part of the refrigerant system. Since aircontains moisture, its entrance into the circuit shouldbe controlled as much as possible during installation.Most maintenance problems come from carelesserection and installation. All openings to therefrigerant circuit—piping, controls, compressor,condensers, and so on—must be adequately sealedwhen work on them is not in progress. The R-12refrigerant is a powerful solvent that readily dissolvesforeign matter and moisture that may have entered thesystem during installation. This material is sooncarried to the operating valves and the compressor. Itbecomes a distinct menace to bearings, pistons,cylinder walls, valves, and the lubricating oil. Scoringof moving parts frequently occurs when the equipmentis first operated, starting with minor scratches thatincrease until the operation of the compressor isseriously affected.

Under existing specifications, copper tubing andcopper piping needed for installation should becleaned, deoxidized, and sealed. When there is aquestion about cleanliness of tubing or piping to beused, each length of pipe should be thoroughly blownout. Use a strong blast of dry air when blowing out, andclean the tubing with a cloth swab attached to copperwire pulled back and forth in the tube until it is cleanand shiny. Then the ends of the tubes should be sealeduntil connected to the rest of the system.

EFFECTS OF MOISTURE

As little as 15 to 20 parts of moisture per millionparts of R-12 can cause severe corrosion in a system.The corrosion results from hydrochloric acid formedby R-12 in contact with water. A chemical reactiontakes place between the acid and the iron and copper in

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Figure 6-43.—An ice cube machine refrigeration cycle during the freezing process.

the system to form corrosion products. A strong acidcombined with high discharge and compressortemperature can cause decomposition of lubricatingoil and produce a sludge of breakdown products.Either the corrosion or the oil breakdown products canplug valves, strainers, and dryers and cause a seriouscasualty.

NOTE: The formation of ice from a minutequantity of moisture in expansion valves and capillarytubes can occur when operating below 32°F.

LOCATION OF EQUIPMENT

Adequate space should always be left aroundmajor portions of equipment for servicing purposes;otherwise, the equipment must be moved afterinstallation so serviceable parts are accessible (figs.6-45 and 6-46). Compressors require overheadclearance for removal of the head, discharge valveplate, and pistons with side clearance to permitremoval of the flywheel and crankshaft wherenecessary. Water-cooled condensers require a free

area equal to the length of the condenser at one end toprovide room for cleaning tubes, installing new tubes,or removal of the condenser tube assembly. Space isneeded for servicing valves and accessory equipment.Service openings and inspection panels on unitaryequipment require generally at least 18 inches ofclearance for removal of the panel. Air-cooledcondensing units should be placed in a location thatpermits unrestricted flow of air for condensing,whether the condenser is in a unitary piece ofequipment or separate. Inadequate ventilation aroundair-cooled condensers can cause overloading of themotor and loss of capacity.

REFRIGERANT PIPING

Certain general precautions for the installation ofrefrigerant lines should be followed. When thereceiver is above the cooling coil, the liquid line shouldbe turned up before going down to the evaporator.This inverted loop prevents siphoning of the liquidfrom the receiver over into the cooling coil through anopen or leaking expansion valve during compressor

6-29

Figure 6-44.—The defrost cycle of an ice cube machine.

shutdown periods. If siphoning starts, the liquidrefrigerant flashes into a gas at the top of the loop,breaking the continuity of the liquid volume andstopping the siphoning action. Where the coolingcoils and compressors are on the same level, both thesuction and liquid lines should be run to the overheadand then down to the condensing unit, pitching thesuction line toward the compressor to ease oil return.On close-coupled installations, running both lines upto the overhead helps to eliminate vibration strains aswell as provide the necessary trap at the cooling coil.

Prepare pipe and fittings with care, particularlywhen cutting copper tubing or pipe to prevent filings orcuttings from entering the pipe. The small particles ofcopper should be completely removed since the finelydivided copper may pass through the suction strainer.The tube should be cut square, and all burrs and dentsshould be removed to prevent internal restrictions andto permit proper fit with the companion fittings. If ahacksaw is used to cut, a fine-toothed blade should beused, preferably 32 teeth per inch. The use of ahacksaw should be avoided whenever possible. When

making silver-solder joints, brighten up the ends of thetubing or pipe with a wire brush or crocus cloth to makea good bond. Do not use sandpaper, emery cloth, orsteel wool for this cleansing, as this material may enterthe system and cause trouble.

Acid should never be used for soldering, norshould flux be used if its residue forms an acid. Useflux sparingly so no residue will enter inside thesystem and eventually be washed back to thecompressor crankcase. If tubing and fittings areimproperly fitted because of distortion, too much flux,solder, and brazing material may enter the system.

The temperature required to solder or braze pipejoints causes oxidation within the tubing. Theoxidation eventually will be removed by therefrigerant flow after the system is in operation. Theoxide breaks up into a fine powder to contaminate thelubricant in the compressor and to plug strainers anddriers. To eliminate this possibility, provide a neutralatmosphere within the tube being soldered or brazed.Use gas-bled nitrogen through the tubing duringsoldering or brazing and for a sufficient time after the

6-30

Figure 6-45.—A low-temperature screw or helix compressor system. (1) Compressor; (2) Oil separator and reservoir;(3) Oil coller; (4) Oil filters (5) Hot -gas discharge line.

bond is made until the heat of the copper has beenreduced below the temperature of oxidation.

All joints should be silver-soldered and kept to aminimum to reduce leaks. Special copper tube fittingsdesigned for refrigeration service should be used sincethese are manufactured with close tolerances to assuretight capillary joints in the brazing process.

SAE flare joints are generally not desired, butwhen necessary, care should be taken in making thejoint. The flare must be of uniform thickness andshould present a smooth, accurate surface, free fromtool marks, splits, or scratches. The tubing must be cutsquare, provided with a full flare, and any burrs andsaw filings removed. The flare seat of the fittingconnector must be free from dents or scratches. Theflare can best be made with a special swivel headflaring tool, available as a general stores item, whichremains stationary and does not tear or scar the face of

the flare in the tubing. Oil should not be used on theface of the flare, either in making up the flare or insecuring it to the fitting, since the oil will eventually bedissolved by the refrigerant in the system and cause aleak through the displacement of the oil. The flarejo in t shou ld a lways be t igh tened wi th twowrenches—one to turn the nut and the other to hold theconnecting piece to avoid strain on the connection andcause a leak.

Where pipe or tubing has to be bent, bends shouldbe made with special tools designed for this type ofwork. Do not use rosin, sand, or any other filler insidethe tubing to make a bend. Threaded joints should becoated with a special refrigerant pipe dope. In anemergency, use a thread compound for making up ajoint; remember R-12 and R-22 are hydrocarbons,which dissolve any compound containing oil. Acompound containing an acid or one whose residualsubstance forms an acid should not be used. The use of

6-31

Figure 6-46.—A twelve-cylinder semihermetic reciprocating direct drive compressor. (1) Compressor; (2) control Panel;(3) Oil Return from Reservoir; (4) Suction Line; (5) Hot Gas Discharge Line.

a thick paste made of fresh lethargy and glycerin makesa satisfactory joint compound; however, the jointshould be thoroughly cleaned with a solvent toeliminate oil or grease. Thread compounds should beapplied to the male part of the thread after it has enteredthe female coupling one and one-half to two threads toprevent any excess compound from entering thesystem.

When securing, anchoring, or hanging the suctionand liquid lines, be sure and allow enough flexibilitybetween the compressor and the first set of hangers orpoints where the lines are secured to permit somedegree of freedom. This flexibility relieves strain inthe joints of these lines at the compressor due tocompressor vibration.

MULTIPLE COMPRESSORS

Parallel operation of two or more reciprocatingcompressors should be avoided unless there are strongand valid reasons for not using a single compressor. In

a situation where two compressors must be used,extreme care in sizing and arranging the piping systemis essential.

An acceptable arrangement of two compressorsand two condensers is shown in figure 6-47. Anequalizer line connects the crankcase at the oil level ofeach machine. Therefore, the oil in both machines willbe at a common level. If machines of different sizesare used, the height of the bases beneath the machinesmust be adjusted so the normal oil level of bothmachines is at the same elevation; otherwise, the oilaccumulates in the lower machine.

This arrangement is called a single-pipe crankcaseequalizer. It can be used only on those machines with asingle equalizer tapping entering the crankcase in sucha position that the bottom of the tapping just touchesthe normal oil level.

Another method of piping to maintain proper oillevel in two or more compressors uses two equalizerlines between the crankcase—one above the normal oil

6-32

Figure 6-47.—Parallel compressors with separate condensers.

level and one below. The double equalizer systemmust be used on compressors having two equalizertappings. A single equalizer line on machines havingtwo equalizer tappings should never be used.

The lower oil equalizer line must not rise above theoil level in the crankcase and should be as level aspossible. This is important since the oil builds up inone crankcase if the line rises. The upper equalizer lineis a gas line intended to prevent any difference incrankcase. pressure that would influence the gravityflow of oil in the lower equalizer line or the level of oilin the crankcase. This upper line must not dip, andcare should be taken to eliminate pockets in which oilcould accumulate to block the flow of gas. Valves inthe crankcase equalizer lines are installed with thestems horizontal, so no false oil levels are created byoil rising over the valve seat and minimize flowresistance.

It is poor practice to skimp on piping when makingup these equalizer lines. Oversize piping is preferredto undersize piping. General practice indicates the useof oil equalizer lines equal to the full size of the tappingin the compressor.

The discharge lines from the compressors are alsoequalized before they enter the condensers. This, in

effect, causes the individual condensers to function asa single unit. This is the most critical point in thepiping system. It is here that pressure drop isextremely important—a pressure drop of 0.5 psi beingequal to a 1.0 foot head of liquid. Excessive pressuredrop in the equalizer line may rob one condenser of allliquid by forcing it into the other condenser. One ofthe results may be the pumping of large quantities ofhot refrigerant vapor into the liquid lines from thecondenser of the operating compressor. This couldreduce the capacity of the system materially. For thisreason, the equalizer line should be just as short andlevel as possible. A long equalizer line introduces anunequal pressure in condensers if one of thecompressors is not operating. The refrigerant thenaccumulates in the condenser of the nonoperatingcompressor. The equalizer line should also begenerously sized and should be equal to or larger thanthe discharge 1 ine of the largest compressor being

used.

If the condensers are more than 10 feet above thecompressor, U-traps or oil separators should beinstalled in the horizontal discharge line where itcomes from each compressor.

6-33

The traps or separators prevent the oil fromdraining back to the compressor head on shutdown.Should a single compressor or multiple compressorswith capacity modulation be used in an instance of thiskind, another solution may be dictated. When acompressor unloads, less refrigerant gas is pumpedthrough the system. The velocity of flow in therefrigerant lines drops off as the flow decreases. It isnecessary to maintain gas velocities above someminimum value to keep the entrained oil moving withthe refrigerant. The problem becomes particularlyacute in refrigerant gas lines when the flow is upward.It does not matter whether the line is on the suction ordischarge side of the compressor; the velocity must notbe allowed to drop too low under low refrigerant flowconditions. Knowing the minimum velocity, 1,000feet per minute (fpm), for oil entrainment up a verticalriser and the minimum compressor capacity, thedesigner of the piping can overcome this problemusing a double riser.

The smaller line in the double riser is designed forminimum velocity, at the minimum step, ofcompressor capacity. The larger line is sized to assurethat the velocity in the two lines at full load isapproximately the same as in the horizontal flow lines.A trap of minimum dimensions is formed at the bottomof the double-riser assembly, which collects oil atminimum load. Trapped oil then seals off the largerline so the entire flow is through the smaller line.

If an oil separator is used at the bottom of adischarge gas riser, the need for a double riser iseliminated. The oil separator will do as its nameimplies—separate the major part of the oil from the gasflowing to it and return the oil to the compressorcrankcase. Since no oil separator is 100 percenteffective, the use of an oil separator in the dischargeline does not eliminate the need for double risers in thesuction lines of the same system if there are verticalrisers in the suction lines. When multiple compressorswith individual condensers are used, the liquid linesfrom the condenser should join the common liquid lineat a level well below the bottoms of the condensers.The low liquid line prevents gas from an "empty"condenser from entering the line because of the sealformed by the liquid from other condensers.

NOTE: A common water-regulating valve shouldcontrol the condenser water supply for a multiplesystem using individual condensers, so each condenserreceives a proportional amount of the condenser water.

Frequently, when multiple compressors areinstalled, only one condenser is provided. Such

installations are satisfactory only as long as all of thecompressors are operating at the same suctionpressure. However, several compressors mayoccasionally be installed which operate at differentsuction pressures—the pressures corresponding, ofcourse, to the various temperatures needed for thedifferent cooling loads. When this is the case, aseparate condenser must be installed for eachcompressor or group of compressors operating at thesame suction pressure. Each compressor, or group ofcompressors, operating at one suction pressure musthave a complete piping system with an evaporator andcondenser, separate from the remaining compressorsoperating at other suction pressures. Separate systemsare required because the crankcase of compressorsoperating at different suction pressures cannot beinterconnected. There is no way of equalizing the oilreturn to such compressors.

The suction connection to a multiple compressorsystem should be made through a suction manifold, asshown in figure 6-47. The suction manifold should beas short as possible and should be taken off in such amanner that any oil accumulating in the header returnsequally to each machine.

Evaporative condensers can be constructed withtwo or more condensers built into one spray housing.This is accomplished quite simply by providing aseparate condensing coil for each compressor, or agroup of compressors, operating at the same suctionpressure. All of the condensing coils are built into onespray housing; this provides two or more separatecondensers in one condenser housing.

Q28.

Q29.

Q30.

Q31.

Q32.

What type of acid is formed when R-12 is mixedwith water?

Air-cooled condensers should be located inareas that provide plenty of clear space aroundthem for what reason?

On close-coupled systems, running refrigerantlines up to the overhead helps eliminate whatproblem?

To eliminate possible oxidation from occurringwhile conduct ing soldering or brazingoperations, you should ensure what conditionexists within the tube or pipe?

U-traps or oil separators should be installed onmult iple compressor systems when thecondensers are how many feet above thecompressor?

6-34

Q33. If an oil separator is used at the bottom of a

discharge riser on multiple compressor

applications, the need for a double riser is

eliminated. True/False.

MAINTENANCE, SERVICE, ANDREPAIR OF REFRIGERATION

EQUIPMENT

Learning Objective: Understand different types ofmaintenance equipment and methods for basicmaintenance, service, and repair of refrigerationsystems and components.

As a Utilitiesman, you must be able to maintain,service, and repair refrigeration equipment. Thisphase of our discussion provides information ondifferent jobs that you may be assigned. Wheninformation here varies from that in the latest federal ormilitary specifications, the specifications apply. Youwi l l f ind the "Troub leshoo t ing Check l i s t–Refrigeration Systems," which is presented in table V,appendix II, at the end of this book, helpful in locatingand correcting troubles. It is not intended to be allencompass ing . Manufac tu re r s a l so p rov ideinstruction manuals to aid you in maintaining andservicing their equipment.

SERVICING EQUIPMENT

Repair and service work on a refrigeration systemconsists mainly of containing refrigerant andmeasuring pressures accurately. One piece ofequipment is the refrigerant gauge manifold set (fig.6-48). It consists of a 0-500 psig gauge for measuringpressure at the compressor high side, a compoundgauge (0-250 psig and 0 to -30 inches of mercury) tomeasure the low or suction side, and valves to controladmission of the refrigerant to the refrigerationsystem. It also has the connections and lines requiredto connect the test set to the system. Depending on testand service requirements, the gauge set can beconnected to the low side, the high side, a source ofvacuum, or a refrigerant cylinder. A swiveling hangerallows the test set to be hung easily, and the threeadditional blank connections allow for securing theopen ends of the three lines when the gauge set is not inuse. There is always a path from the low-side andhigh-side input to the low-side and high-side gauge(fig. 6-49).

Another important piece of equipment is theportable vacuum pump. The type listed in the Seabee

Figure 6-48.—Refrigerant gauge manifold set.

Figure 6-49.—Internal view of a refrigerant gauge manifold

set.

Table of Allowance is a sealed unit consisting of asingle-piston vacuum pump driven by an electricmotor. A vacuum pump is the same as a compressor,except the valves are arranged so the suction valve isopened only when the suction developed by thedownward stroke of the piston is greater than thevacuum already in the line. This vacuum pump candevelop a vacuum close to -30 inches of mercury,which can be read on the gauge mounted on the unit

6-35

(fig. 6-50). The pump is used to reduce the pressure in arefrigeration system to below atmospheric pressure.

Various manufacturers manufacture hermeticrefrigeration systems used by the Navy; therefore, theconnectors and size of tubing vary. The Table ofAllowance provides for a refrigeration service kit thatcontains several adapters, wrenches, and othermaterials to help connect different makes of systems tothe refrigerant manifold gauge set and the vacuumpump lines. A table affixed to the lid of the storagecontainer identifies the adapter you should use for aparticular refrigeration unit.

Figure 6-50.—Portable vacuum pump.

TRANSFERRING REFRIGERANTS

Refrigerants are shipped in compressed gascylinders as a liquid under pressure. Liquids areusually removed from the shipping containers andtransferred to a service cylinder (fig. 6-51).

Before attempting transfer of refrigerants from acontainer to a cylinder, precool the receiving cylinderuntil its pressure is lower than that of the storagecontainer or cylinder. Precool by placing the cylinderin ice water or a refrigerated tank. You must alsoweigh the service cylinder, including cap, and compareit with the tare weight stamped or tagged on thecylinder. The amount of refrigerant that may be placedin a cylinder is 85 percent of the tare weight (the weightof a full cylinder and its cap minus the weight of theempty cylinder and its cap).

To transfer refrigerants, connect a flexiblecharging line on a 1/4-inch copper tube several feetlong with a circular loop about 8 to 10 inches indiameter. Be sure to install a 1/4-inch refrigerantshutoff valve (fig. 6-51) in the charging line to theservice cylinder. This valve should be inserted so nomore than 3 inches of tubing is between the last fittingand the valve itself. This arrangement prevents the lossof refrigerant when the service drum is finallydisconnected. The entire line must be cleared of air byleaving the flare nut on the service cylinder loose andcracking the storage cylinder valve. This arrangementallows refrigerant to flow through the tubing, clearingit. After clearing, tighten the flare nut and then openthe valve on the service cylinder, the valve on the

Figure 6-51.—Method of transferring refrigerants to service cylinders.

6-36

storage cylinder, and then the 1/4-inch valve in therefrigerant line. When the weight of the servicecylinder shows a sufficient amount of refrigerant is inthe serviced cylinder, close all valves tightly, anddisconnect the charging line at the service cylinder.

CAUTION

To warm refrigerant containers orcylinders for more rapid discharge, usecare to prevent a temperature above120°F because the fusible plugs in thecylinder and valve have a melting pointof about 157°F.

Figure 6-52.—Connections for drawing a vacuum.

EVACUATING AND CHARGING ASYSTEM

One of your duties will be charging a system withrefrigerant. If a system develops a leak, you mustrepair it first, then charge the system. Similarly, if acomponent of the system becomes faulty and must bereplaced, some refrigerant will be lost and the systemwill require charging.

Evacuation

Before a system can be charged, all moisture andair must be eliminated from the components bydrawing a vacuum on the system. To draw a vacuumon the system, proceed as follows:

1. Connect the portable vacuum pump to thevacuum fitting on the refrigerant manifoldgauge set (fig. 6-48).

2. Connect the LO line (suction) to the suctionservice valve of the compressor, usingappropriate connectors if required.

3. Turn the suction service valve to mid-position,so vacuum draws from the compressorcrankcase and suction line back through theevaporator, expansion valve, and liquid line.When the receiver service valve, condenserservice valve, and discharge service valve areopen, the pump draws back through the receiverand condenser to the compressor.

4. Attach one end of a 1/4-inch copper tube to thevacuum pump discharge outlet (fig. 6-52).Allow the vacuum pump to draw a vacuum of atleast 25 inches. Submerge the other end of the

copper tubing under 2 or 3 inches of cleancompressor oil contained in a bottle.

5. Continue to operate the vacuum pump untilthere are no more bubbles of air and vapor in theoil, which indicates that a deep vacuum has beenobtained.

6. Maintain the deep vacuum operation for at least5 minutes, and then stop the vacuum pump.Leaking discharge valves of a vacuum pumpcause oil to be sucked up into the copperdischarge tube. Keep the vacuum pump off atleast 15 minutes to allow air to enter the systemthrough any leaks. Then start the vacuumpump. A leaky system causes bubbling of theoil in the bottle.

7. Examine and tighten any suspected joints in theline, including the line to the vacuum pump.Repeat the test.

Charging

In most small refrigerating systems, low-sidecharging (fig. 6-53) is generally recommended foradding refrigerant after repairs have been made. Afterthe system has been cleaned and tested for leaks, thesteps to charge the system are as follows:

1. Connect a line from a refrigerant cylinder to thebottom center connection on the refrigerantgauge manifold set. Be certain the refrigerantcylinder is in a vertical position, so onlyrefrigerant in the form of gas, not liquid, canenter the system. Leave the connection looseand crack the valve on the cylinder. This fills

6-37

Figure 6-53.—Connections for low-side charging.

2 .

3 .

4 .

5 .

the line with gas and clears the air from the line.

After clearing, tighten the connection.

Connect a line from the LOW (LO) valve

(suction) on the gauge manifold set to the

suction service valve of the compressor.

Start the compressor.

Open the valve on the cylinder and the LOW

(LO) valve (suction) on the gauge manifold set.

Open the suction service valve on thecompressor to permit the gas to enter thecompressor where it will be compressed and fedto the high side. Add the refrigerant slowly andcheck the liquid level indicator regularly untilthe system is fully charged. It is easy to checkthe receiver refrigerant level in some makes ofcondensing units because the receiver hasminimum and maximum liquid level indicatorvalves which show the height of the liquid levelwhen opened. If a liquid line sight glass is used,the proper charge may be determined whenthere is no bubbling of refrigerant as it passes by

the glass. The sight glass will appear empty.

Again, be certain the refrigerant cylinder is in thevertical position at all times; otherwise, the liquidrefrigerant will enter the compressor and, liquid notbeing compressible, damage the piston or other parts ofthe compressor.

REFRIGERANT LEAKS

system is when there is enough pressure to increase the

The best ti me to test joints and connections in a

rate at which the refrigerant seeps from the leakingjoint. There is usually enough pressure in thehigh-pressure side of the system; that is, in thecondenser, receiver, and liquid line, includingdehydrators, strainers, line valves, and solenoidvalves. This is not necessarily true of the low-pressureside of the system, especially if it is a low-pressureinstallation, such as for frozen foods and ice cream,where pressures may run only slightly above zero onthe gauge. When there is little pressure, increase thepressure in the low-pressure side of the system bybypassing the discharging pressure from the condenserto the low-pressure side through the service gaugemanifold Small leaks cannot be found unless thepressure inside the system is at least 40 to 50 psi,regardless of the method used to test for leaks.

Halide Leak Detector

The use of a halide leak detector (fig. 6-54) is themost positive method of detecting leaks in a refrigerantsystem using halogen refrigerants (R-12, R-22, R-11,R-502, etc.). Such a detector consists essentially of atorch burner, a copper reactor plate, and a rubberexploring hose.

Detectors use acetylene gas, alcohol, or propane asa fuel. A pump supplies the pressure for a detector thatuses alcohol. If a pump-pressure type of alcohol-burning detector is used, be sure that the air pumpedinto the fuel tank is pure.

Figure 6-54.—Halide leak detector.

6-38

An atmosphere suspected of containing a halogenvapor is drawn through the rubber exploring hose intothe torch burner of the detector. Here the air passesover the copper reactor plate, which is heated toincandescence. If there is a minute trace of a halogenrefrigerant present, the color of the torch flamechanges from blue (neutral) to green as the halogenrefrigerant contacts the reactor plate. The shade ofgreen depends upon the amount of halogen refrigerant;a pale green color shows a small concentration and adarker green color, a heavier concentration. Too muchof a halogen refrigerant causes the flame to burn with avivid purple color. Extreme concentrations of ahalogen refrigerant may extinguish the flame bycrowding out the oxygen available from the air.

Normally, a halide leak detector is used for R-12and R-22 systems. In testing for leaks always start atthe highest point of the system and work towards thelowest point because halogen refrigerants are heavierthan air.

When using a leak detector, you will obtain thebest results by following the Precautions listed below.

3.

4.

1.

2.

5.

6.

Be sure the reactor plate is properly in place.

Adjust the flame so it does not extend beyondthe end of the burner. (A small flame is moresensitive than a large flame. If it is hard to lightthe torch when it is adjusted to produce a smallflame, block the end of the exploring hose untilthe fuel ignites; then gradually open the hose.)

Clean out the rubber exploring hose if the flamecontinues to have a white or yellow color. (Awhite or yellow flame is an indication that theexploring tube is partially blocked with dirt.)

Check to see that air is being drawn into theexploring tube; this check can be made fromtime to time by holding the end of the hose toyour ear.

Hold the end of the exploring hose close to thejoint being tested to prevent dilution of thesample by stray air currents.

Move the end of the exploring hose slowly andcompletely around each joint being tested.(Leak testing cannot be safely hurried. There isa definite time lag between the moment when airenters the exploring hose and the moment itreaches the reactor plate; permit enough time forthe sample to reach the reactor plate.)

If a greenish flame is noted, repeat the test in thesame area until the source of the refrigerant is located.

Always follow a definite procedure in testing forrefrigerant leaks, so none of the joints are missed.Even the smallest leaks are important. However slighta leak may seem, it eventually empties the system of itscharge and causes faulty operation. In the long run, theextra time spent in testing each joint will be justified.A refrigerant system should never be recharged untilall leaks are discovered and repaired.

Electronic Leak Detector

The most sensitive leak detector of all is theelectronic type. The principle of operation is based onthe dielectric difference of gases. In operation, the gunis turned on and adjusted in a normal atmosphere. Theleak-detecting probe is then passed around the surfacessuspected of leaking. If there is a leak, no matter howtiny, the halogenated refrigerant is drawn into theprobe. The leak gun then gives out a piercing sound, ora light flashes, or both, because the new gas changesthe resistance in the circuit.

When using an electronic leak detector, minimizedrafts by shutting off fans or other devices that causeair movement. Always position the sniffer below thesuspected leak. Because refrigerant is heavier than air,it drifts downward. Always remove the plastic tip andclean it before each use. Avoid clogging it with dirtand lint. Move the tip slowly around the suspectedleak.

Soap and Water Test

Soap and water may be used to test for leakage ofrefrigerant with a pressure higher than atmosphericpressure. Make a soap and water solution by mixing alot of soap with water to a thick consistency. Let itstand until the bubbles have disappeared, and thenapply it to the suspected leaking joint with a soft brush.Wait for bubbles to appear under the clear, thick soapsolution.

Find extremely small leaks by carefully examiningsuspected places with a strong light. If necessary, usea mirror to view the rear side of joints or otherconnections suspected of leaking.

PUMPING DOWN

Quality refrigeration repair includes preventingloss of refrigerant in the system. Whenever acomponent is removed from the system, the normally

6-39

closed system is opened and, unless precautions are

taken, refrigerant is lost to the atmosphere. The best

way to contain the refrigerant (gas and liquid) is to trap

it in the condenser and receiver by pumping down the

system.

To pump down the system, proceed as follows:

1. Secure electric power to the unit and connect therefrigerant manifold test set, as shown in figure6-55.

2. Close the receiver stop (king) valve (by turningthe valve stem inwards as far as it will go), andclose both gauges on the gauge manifold (LOand HI valves).

3. Start the compressor and mid-seat the dischargeand suction service valves.

4. Operate the compressor until the pressure on thesuction (LO) gauge on the manifold shows avacuum at 0 to 1 psi.

5. Stop the compressor. If the pressure rebuildsappreciably, operate the unit again untilpressure registers between 0 to 1 psi. Repeatthis step until the pressure no longer rebuildsappreciably.

6. When suction pressure remains at about 0 to 1pound as read on the compound gauge, thenfront-seat the suction and discharge service

valves (fig. 6-56). This procedure trapspractically all the refrigerant in the condenserand receiver.

RECOVERY, RECYCLING, ANDRECLAIMING REFRIGERANT

Laws governing the release of chlorofluorocarbonrefrigerants (CFCs) into the atmosphere have resultedin the development of procedures to recover, recycle,and reuse these refrigerants. Many companies havedeveloped equipment necessary to prevent the releaseof CFCs into the atmosphere. Refrigerant recoverymanagement equipment can be divided into threecategories—recovery, recycle, and reclaimingequipment.

Recovery

Removing refrigerant from a system in anycondition and storing it in an external container iscalled "recovery." Removal of refrigerant from thesystem is necessary, in some instances, when repair ofa system is needed. To accomplish this, you can usespecial recovery equipment, which is now arequirement when removing refrigerant from a system.This equipment ensures complete removal of therefrigerant in the system.

Recovery is similar to evacuating a system withthe vacuum pump and is accomplished by either thevapor recovery or liquid recovery method. In the vapor

Figure 6-55.—Connections for pumping down a system.

6-40

Figure 6-56.—Three-way service valve positions.

recovery method (fig. 6-57), a hose is connected to thelow-side access point (compressor suction valve)through a filter-drier to the transfer unit, compressorsuction valve. A hose is then connected from thetransfer unit, compressor discharge valve to anexternal storage cylinder. When the transfer unit isturned on, it withdraws vapor refrigerant from thesystem into the transfer unit compressor, which, inturn, condenses the refrigerant vapor to a liquid anddischarges it into the external storage cylinder.

In the liquid recovery method (fig. 6-58), a hose isconnected to the low-side access point to the transferunit compressor discharge valve. A hose is thenconnected from the transfer unit compressor suctionvalve through a filter-drier to a two-valve externalstorage cylinder. A third hose is connected from the

high-side access point (liquid valve at the receiver) tothe two-valve external storage cylinder. When thetransfer unit is turned on, the transfer unit compressorpumps refrigerant vapor from the external storagecylinder into the refrigeration system, whichpressurizes it. The difference in pressure between thesystem and the external storage cylinder forces theliquid refrigerant from the system into the externalcylinder. Once the liquid refrigerant is removed fromthe system, the remaining vapor refrigerant is removedusing the vapor recovery method as previouslydescribed.

Most recovery units automatically shut off whenthe refrigerant has been completely recovered, butcheck the manufacturer's operational manual forspecific instructions. You should make sure that the

Figure 6-57.—The vapor recovery method.

6-41

Figure 6-58.—The liquid recovery method.

external storage cylinder is not overfilled. Eightypercent capacity is normal. If the recovery unit isequipped with a sight-glass indicator, any changes thatmay occur should be noted.

Recycling

performed by most recycling machines reduces thecontaminants through oil separation and filtration.Normally recycling is accomplished during therecovery of the vapor or liquid refrigerant by use ofequipment that does both recovery and recycling ofrefrigerant.

The process of cleaning refrigerant for reuse by oil Recycling machines use either the single-pass or

separation and single or multiple passes through multiple-pass method of recycling. The single-pass

filter-driers which reduce moisture, acidity, and matter method (fig. 6-59) processes refrigerant through a

is called "recycling." In the past, refrigerant was filter-drier and/or uses distillation. It makes only onetypically vented into the atmosphere. Modern pass through the recycling process to a storagetechnology has developed equipment to enable reuse cylinder. The multiple-pass method (fig. 6-60)of old, damaged, or previously used refrigerant. recirculates refrigerant through the filter-drier manyRefrigerant removed from a system cannot be simply times, and after a period of time or number of cycles,reused—it must be clean. Recycling in the field as the refrigerant is transferred to a storage cylinder.

Figure 6-59.—Single-pass method of recycling.

6-42

Figure 6-60.—Multiple-pass method of recycling.

Reclaiming

The reprocessing of a refrigerant to originalproduction specifications as verified by chemicalanalysis is called "reclaiming." Equipment used forthis process must meet SAE standards and remove 100percent of the moisture and oil particles.

Most reclaiming equipment uses the same processcycle for reclaiming refrigerant. The refrigerant entersthe unit as a vapor or liquid and is boiled violently at ah igh t empera tu re a t ex t reme h igh p ressu re(distillation). The refrigerant then enters a large,unique separator chamber where the velocity isradically reduced, which allows the high-temperaturevapor to rise. During this phase all the contaminants,such as copper chips, carbon, oil, and acid, drop to thebottom of the separator to be removed during the "oilout" operation. The distilled vapor then leaves theseparator and enters an air-cooled condenser where itis converted to a liquid. Then the liquid refrigerantpasses through a filter-drier into a storage chamberwhere the refrigerant is cooled to a temperature of 38°F

to 40°F by an evaporator assembly.

COMPONENT REMOVAL ORREPLACEMENT

To maintain a refrigerant system at a optimum

operating condition sometimes requires removal orreplacement of some component. Procedures for

removal and replacement of some of the components

most often requiring action are covered in this section.

Removing Expansion or Float Valves

To help ensure good results in removing expansion

or float valves, you should pump the system down to a

suction pressure of just over zero. You should do this

at least three times before removing the expansionvalve. Plug the opened end of the liquid line and

evaporator coil to prevent air from entering the system.Repair or replace the expansion valve and connect it tothe liquid valve. Crack the receiver service valve toclear air from the liquid line and the expansion valve.

Connect the expansion valve to the evaporator coilinlet and tighten the connection. Pump a vacuum into

the low side of the system to remove any air.

6-43

Replacing an Evaporator

To replace an evaporator, pump down the system

and disconnect the liquid and suction lines. Then

remove the expansion valve and the evaporator. Make

the necessary repairs or install a new evaporator as

required. Replace the expansion valve and connect the

liquid and suction lines. Remove moisture and air by

evacuating the system. When the evaporator is back in

place, pump a deep vacuum as in starting a new

installation for the first time. Check for leaks and

correct them if they occur. If leaks do occur, be certain

to repair them; then pump the system into a deep

vacuum. Repeat the process until no more leaks are

found.

Removing the Compressor

Using the gauge manifold and a vacuum pump,

pump down the system. Most of the refrigerant will be

trapped in the condenser and the receiver. To remove

the compressor from service, proceed as follows:

1. Once the pump down is complete, the suctionvalve should already be closed and the suctiongauge should read a vacuum. Mid-seat thedischarge service valve. Open both manifoldvalves to allow high-pressure vapor to build upthe compressor crankcase pressure to 0 psi.

2. Front-seat (close) the discharge service valve.Then crack the suction service valve until thecompound gauge reads 0 to 1 psi to equalize thepressures and then front-seat the valve.

3. Joints should be cleaned with a grease solventand dried before opening. Unbolt the suctionservice and discharge service valves from thecompressor. DO NOT remove the suction ordischarge lines from the compressor servicevalves.

4. Immediately plug all openings through whichrefrigerant flows using dry rubber, "cork"stoppers, or tape.

5. Disconnect the bolts that hold the compressor tothe base and remove the drive belt or disconnectthe drive coupling. You can now remove thecompressor.

Removing Hermetic Compressors

Systems using hermetic compressors are not easilyrepaired, as most of the maintenance performed on

them consists of removal and replacement.

1.

2.

3.

4.

5.

Disconnect the electrical circuit including theoverload switch.

Install a gauge manifold. Use a piercing valve(Schraider) if needed.

Remove the refrigerant using an EPA approvedrecovery/recycling unit.

Disconnect the suction and discharge lines.Using a pinching tool, pinch the tubing on boththe suction and discharge lines, and cut bothlines between the compressor and the pinchedarea.

Disconnect the bolts holding the compressor tothe base and remove the compressor.

Do not forget to pump down the system and

equalize the suction and head pressure to theatmosphere, if applicable. Wear goggles to preventrefrigerant from gett ing in your eyes. After

replacement, the procedures given for removing airand moisture and recharging the system can befollowed; however, the procedures may have to bemodified because of the lack of some valves and

connections. Follow the specif ic procedures

contained in the manufacturer's manual.

Q34.

Q35.

Q36.

Q37.

Q38.

Q39.

Q40.

What are the two major pieces of maintenanceequipment used for refrigeration work?

Before attempting transfer of refrigerantfrom acontainer to a cylinder, you should precool thereceiving cylinder for what reason?

What i s t he purpose o f evacua t ing arefrigeration system?

You should continue to operate the vacuumpump during evacuation of a system until whatcondition is obtained?

What method of charging a system is generallyrecommended?

What are the three methods used to detectrefrigerant leaks?

When you pump down a system, where is therefrigerant stored?

6-44

Q41. What are the two methods of refrigerantrecovery?

Q42. Recycling refrigerant reduces contaminantsthrough what two processes?

MAINTENANCE OF COMPRESSORS

Learning Objective: Recall the inspection points foropen-type compressors and repair procedures forcommon problems in open-type refrigerationcompressors.

Inspection points for open-type compressors andrepair procedures for common problems in open-typerefrigeration compressors are covered in this section.

OPEN TYPES OF COMPRESSORS

Figure 6-61 shows a vertical single-actingreciprocating compressor. Some of the duties you mayperform in maintaining this and other open-typecompressors are discussed below.

Shaft Bellows Seal

Refrigerant leakage often occurs at the shaftbellows seal with consequent loss of charge. Install a

test gauge in the line leading from the drum to thecompressor. Attach a refrigerant drum to the suctionend of the shutoff valve outlet port. Apply the properamount of pressure, as recommended in themanufacturer's instructions. Test for leaks with ahalide leak detector around the compressor shaft, sealgasket, and seal nut. Slowly turn the shaft by hand.When a leak is located at the seal nut, replace the sealplate, gasket, and seal assembly; when the leak is at thegasket, replace the gasket only. Retest the seal afterreassembly. (This procedure is typical for most shaftseals on reciprocating open-type compressors.)

Valve Obstructions

Obstructions, such as dirt or corrosion, may beformed under seats of suction or discharge valves. Tolocate the source of trouble, proceed as follows:

When the suction side is obstructed, the unit tendsto run continuously or over long periods. Connect thegauge manifold and start the unit. This pressure gauge(HI) will not indicate an increase in pressure. Thelow-side gauge (LO) will fluctuate and will notindicate any decrease in pressure. Clean out anyobstructions and recheck again by using the test gaugeassembly.

Figure 6-61.—Vertical single-acting reciprocating compressor.

6-45

To determine if there is a discharge valve leak,connect the gauge manifold and start the unit. Run ituntil the low-side (LO) pressure gauge indicatesnormal pressure for the unit. Stop the unit. With an earnear the compressor housing, listen for a hissingsound. Also, watch the gauges. When leaking causedby an obstruction is present, the low-side pressurerises, and the high side decreases until the pressures areequalized. A quick equalization of pressures indicatesa bad leak that should be repaired immediately or thecompressor replaced.

Compressor Lubrication

The oil level in the compressor crankcase shouldbe checked by the procedure in the followingmanufacturer's manual. This procedure normallyincludes the following steps:

1.

2.

3.

4.

Attach the gauge manifold to the suction anddischarge service valves.

Pump the system down.

Close the suction and discharge valves, isolatingthe compressor.

Remove the oil filter plug and measure the oillevel as per the manufacturer’s manual.

Compressor Knocks

When the compressor knocks, you may have todisassemble the compressor to determine whether thecause is a loose connecting rod, piston pin, orcrankshaft. Sometimes a loose piston can be detectedwithout the complete disassembly. In cases requiringdisassembly, you should take the following steps:

First, remove the cylinder head and valve plate toexpose the top of the piston. Start the motor and pressdown with your finger on top of the piston. Anylooseness can be felt at each stroke. The loose partshould be replaced.

Check the oil level because oil levels that are toohigh often cause knocks. Always make sure that a lowoil level is actually the result of a lack of oil, rather thana low charge.

Stuck or Tight Compressor

A stuck or tight compressor often occurs as a resultof poor reassembly after a breakdown repair. In suchcases, determine where the binding occurs and

reassemble the unit with correct tolerances; avoiduneven tightening of screws or seal covers.

INSPECTION OF COMPRESSORS

An inspection should be performed on arefrigeration unit from time to time for knocks,thumps, rattles, and so on, while the unit is inoperation. When any of the external parts haveexcessive grease, dirt, or lint, they should be cleaned.Before cleaning, you should always ensure the poweris off.

A careful check of the entire system withinstruments or tools is essential to determine if therehas been any loss of refrigerant. NO LEAK IS TOOSMALL TO BE FIXED. Each leak must be stoppedimmediately.

Some specific conditions to look for during theinspection of a refrigeration system are as follows:

Inadequate lubrication of bearings and othermoving parts.

Rusty or corroded parts discovered during theinspection should be cleaned and painted.

Hissing sounds at the expansion valve, lowreadings on the discharge pressure gauge, and bubblesin the receiver sight glass, all indicate a weakrefrigerant charge.

Loose connections and worn or pitted switchcontacts result in inoperative equipment or reducedreliability. Thermostats with burned contacts mayproduce abnormal temperatures in the cooledcompartment.

Fans difficult to rotate by hand, with bent blades,or loose or worn belts are a source of trouble easy tolocate and correct during inspection.

Air filters clogged with dirt should be cleaned orreplaced during the inspection.

Hermetically sealed units should be inspected forsigns of leaks and high temperatures and for too muchnoise or vibration.

Q43. On compressors, refrigerant leaks most oftenoccur at what location?

Q44. Hissing sounds at the expansion valves, lowdischarge pressure, and bubbles in the receiversight glass during inspections indicate whatpossible problems?

6-46

Q45. When inspecting hermetic compressors, you freezing point of water. As a result, ice can form in theshould look for what type of problems?

MAINTENANCE OF MOTORS

Learning Objective: Understand basic maintenance ofmotors and methods of electrical troubleshooting ofmotors.

Troubles with the electrical motors used to drivethe compressors of mechanical refrigeration systemsfall into two classes—mechanical and electrical.

MECHANICAL PROBLEMS

Some compressors are belt-driven from theelectrical motor. For proper operation, both the belttension and pulley alignment adjustments must bemade. Belt tension should be adjusted so a l-poundforce on the center of the belt, either up or down, doesnot depress it more than one-half inch. To adjust thealignment, loosen the setscrew on the motor pulleyafter tension adjustment is made. Be sure the pulleyturns freely on the shaft; add a little oil if necessary.Turn the flywheel forward and backward severaltimes. When it is correctly aligned, the pulley does notmove inward or outward on the motor shaft. Tightenthe setscrew holding the pulley to the shaft beforestarting the motor.

Compressors may also be driven directly by amechanical coupling between the motor andcompressor shafts. Be sure the two shafts arepositioned so they form a straight line with each other.The coupling on direct drive units should be realignedafter repair or replacement. Clamp a dial indicator tothe motor half coupling with its pointer against theouter edge of the compressor half coupling. Rotate themotor shaft, and observe any fluctuations of theindicator. Move the motor or compressor until theindicator is stationary when revolving the shaft one fullturn. Secure the hold-down bolts and then recheck.

Moisture in the System

When liquid refrigerant that contains moisturevaporizes, the moisture separates from the vapor.Because the vaporization of the refrigerant causes acooling effect, the water that has separated can freeze.Most of the expansion and vaporization of therefrigerant occurs in the evaporator. However, a smallamount of the liquid refrigerant vaporizes in theexpansion valve, and the valve is cooled below the

expansion valve and interfere with its operation. If theneedle in the valve freezes in a slightly off-seatposition, the valve cannot permit the passage ofenough refrigerant. If the needle freezes in a positionfar from the seat, the valve feeds too much refrigerant.In either case, precautions must be observed to assure amoisture-free system.

A dehydrator is filled with a chemical known as adesiccant, which absorbs moisture from the refrigerantpassing through the dehydrator. Dehydrators areinstalled in the liquid line to absorb moisture in thesystem after the original installation. An arrow on thedehydrator indicates the direction of flow. Desiccantsare granular and are composed of silica gel, activatedalumina, or calcium sulfate. Do not use calciumchloride or chemicals that form a nonfreezing solution.These solutions may react with moisture to formundesirable substances, such as gums, sludges, orwaxes. Follow the manufacturer's instructions as tolimitations of dehydrators, as well as operation,recharging, replacing, and servicing.

Loose Copper Tubing

In sealed units, loose copper tubing is usuallydetected by the sound of rattling or metallic vibration.Bending the tubing carefully to the position of leastvibration usually eliminates the defect. Do not touch itagainst other tubing or parts at a point of freemovement, and do not change the tubing pitch or thetubing diameter by careless bending.

In open units, lengths of tubing must be wellsupported by conduit straps or other devices attachedto walls, ceilings, or fixtures. Use friction tape pads toprotect the copper tubing from the metal of the strap.When two tubes are together in a parallel position,wrapping and binding them together with tape canprevent vibration. When two lines are placed incontact for heat exchange, they should be soldered toprevent rattling and to permit better heat transfer.

Doors and Hardware

When hinges must be replaced because of lack oflubrication or other reasons, the use of exact duplicatesis preferable. Loose hinge pins must be securelybraided. When thrust bearings are provided, they areheld in place by a pin.

The latch or catch is usually adjusted for propergasket compression. Shims or spacers may be added

6-47

or removed for adjustment. Latch mechanisms shouldbe lubricated and adjusted for easy operation. Latchrollers must not bind when operated. Be sure toprovide sufficient clearance between the body of thelatch and catch, so no contact is made. The onlycontact is made between the catch and the latch bolt orroller. These instructions also apply to safety doorlatches, when they are provided for opening the doorfrom the inside, although it is locked from the outside.Warping of the door usually causes lack of completegasket contact between the door overlap and thedoorframe. Correct the condition by installing a long,tapered wooden shim or splicer rigidly in place underthe door seal. If this does not tighten the door to theframe, remove the door and either reline or rebuild it.

Repair or replace missing, worn, warped, or loosedoor gaskets. If the gasket is tacked on, rustproof tacksor staples should be used. If the gasket is clamped orheld in place by the doorframe or the door panel, anexact replacement is necessary. In either case, thegasket should be installed so when the door is closed acomplete and uniformly tight seal results. If doorsfreeze closed due to condensation and subsequentfreezing, apply a light coat of glycerine on the gaskets.

Defrosting

Cooling units in the 35°F to 45°F reach-in orwalk-in refrigerators or cold storage rooms aregenerally defrosted automatically by setting thelow-pressure control switch to a predetermined level.If this setting causes overload with consequent heavyfrosting of the coil, manual defrosting is necessary.Cooling units of 35°F and lower temperatures aredefrosted manually. The most common method formanual defrosting is to spray water over the cooling

coil, although warm air, electric heating, or hot gasrefrigerant defrosts too. In any case, the fans must notbe in operation during the defrosting. Defrostplate-type evaporator banks in below-freezingrefrigerators when the ice has built up to a thickness ofone-half inch or when the temperature of the fixtures orthe suction pressure is affected by the buildup of ice.Before removing frost from the plates, place atarpaulin on the floor or over the contents of therefrigerator to catch the frost under the bank.

ELECTRICAL DEFECTS

The control systems for modern refrigerationsystems are composed of many components that use orpass electrical power, including compressor drivemotors, pressure switches, thermostats, and solenoidstop valves. Although as a Utilitiesman second classyou are not responsible for troubleshooting theseelectrical components, you must be able to use themultimeter for locating opens, shorts, and grounds,and measuring voltage and current. Module 3 of theNavy Electricity and Electronics Training Series,NAVEDTRA 172-03-00-93 (Introduction to CircuitProtection, Control, and Measurement), will help youin learning to use electrical meters and testingequipment. When you have finished studying themodule, return to this chapter and learn how to locateopens, shorts, and grounds in refrigeration controlcircuits.

Opens

Figure 6-62 shows a simple refrigeration controlsystem. You have learned the basics of electricity andhow to use meters. Using this figure, you will put thatknowledge to work. Remember one fact—if you are

Figure 6-62.—Simple refrigeration control system.

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not sure what you are doing, call your supervisor orarrange for a Construction Electrician to assist you.

An "open" is defined as the condition of acomponent that prevents it from passing current. Itmay be a broken wire, a burned or pitted relay contact,a blown fuse, a broken relay coil, or a burned-out coilwinding. An open can be located in one of two ways.For the components in series, such as the maindisconnect switch, fuses, the wire from Point C toPoint D (fig. 6-62), the relay contacts, and the wirefrom Point E to Point F, a voltmeter should be used.Set up the voltmeter to measure the source voltage (120volts ac, in this case). If the suspected component isopen, the source will be measured across it. To checkpart of the main disconnect switch, close the switchand measure from Point A to Point B. If the meterreading is 0 volts, that part of the switch is good; if thevoltage equals the source voltage, the switch is open.To check the fuse F2, measure across it, Point B toPoint C. Measuring across Points C and D or E and Fwill check the connecting wires for opens. One set ofrelay contacts can be checked by taking meter readingsat Points D and E. These are just a few examples, butthe rule of series components can always be applied.Remember, the three sets of contacts of relay K1 willnot close unless voltage is present across the relay coil;the coil cannot be open or shorted. When testing anelectrical circuit, follow the safe practices you havebeen taught and use procedures outlined in equipmentmanuals.

Opens in components that are in parallel cannoteasily be found with a voltmeter because, as you know,parallel components have voltage across them at alltimes when the circuit is energized. In figure 6-62, thebranch with the motor relay K1 and the dual refrigerantpressure control are considered a parallel circuit.Because when the main disconnect switch is closedand the fuses are good, there is voltage between PointsC and H, regardless of whether the relay coil andpressure switch are open. To check for opens in thesecomponents, use an ohmmeter set at a low range.Disconnect all power by opening (and locking out, ifpossible) the main disconnect switch. This actionremoves all power and ensures both personal andequipment safety. To check the motor relay K1 to seeif its coil is open, put the ohmmeter leads on Points Cand G. A reading near infinity (extremely highresistance) indicates an open. The contacts of the dualrefrigerant pressure control can be tested by putting theohmmeter leads from Point G to Point H. Again, areading near infinity indicates open contacts. Youmay need to consult the manufacturer's manual for the

physical location of Points G and H. Notice thecontacts of the control are normally closed whenneither the head pressure nor the suction pressure isabove its set limits.

Shorts

Shorts are just the opposite of opens. Instead ofpreventing the flow of current, they allow too muchcurrent to flow, often blowing fuses. The ohmmeteron its lowest range is used to locate shorts bymeasur ing the r e s i s t ance ac ross suspec tedcomponents. If the coil of the motor relay K1 issuspected of being shorted, put the leads on Points Cand G. A lower than normal reading (usually almostzero) indicates a short. You may have to determine thenormal reading by consulting the manufacturer’smanual or by measuring the resistance of the coil of aknown good relay. If fuses F2 and F3 blow and yoususpect a short between the middle and bottom lines(fig. 6-62), put the ohmmeter leads between Points Cand H. Again, a low reading indicates a short.Remember, in all operations using an ohmmeter, it isimperative that all power be removed from the circuitfor equipment and personal safety. Don't fail to dothis!

Grounds

A ground is an accidental connection between apart of an electrical circuit and ground, due perhaps, tophysical contact through wearing of insulation ormovement. To locate a ground, follow the sameprocedure you used to locate a short. The earth itself, acold-water pipe, or the frame of a machine are allexamples of ground points. To see whether acomponent is shorted to ground, put one ohmmeterlead on ground and the other on the point suspected tobe grounded and follow the rules for locating a short.Be sure to turn off all power to the unit. It may even bewise to check for the presence of voltage first. Use avoltmeter set to the range suitable for measuringsource voltage. If power does not exist, then use theohmmeter.

The limited amount of instruction presented here isnot enough to qualify you as an electrician, but itshould enable you to find such troubles as blown fuses,poor electrical connections, and the like. If the troubleappears more complicated than this, call yoursupervisor or ask for assistance from a ConstructionElectrician.

6-49

Testing the Motor

As a Utilitiesman, you should be able to makevoltage measurements in a refrigeration system toensure the proper voltage is applied to the drive motor,as shown on the rating plate of the motor. If the propervoltage is applied (within 10 percent) to the terminalsof the motor and yet it does not run, you must decidewhat to do. If it is an open system (not hermeticallysealed), it is the Construction Electrician's job to repairthe motor. If it is a hermetically sealed unit, however,you must use special test equipment to completefurther tests and perhaps make the unit operationalagain.

If the unit doesn't run, it may be because the motorrotor or compressor crankshaft is stuck (remember, in ahermetically sealed unit, they are one and the same). Ifyou apply electrical power to try and move the motor inthe correct direction first and then reverse the power,you may be able to rock it free and not have to replacethe unit. This is one of the purposes of the hermeticunit analyzer (fig. 6-63). To rock the rotor of anhermetically sealed unit, follow these steps:

1. Determine from the manufacturer's manualwhether the motor is a split-phase or a capacitor-start type.

2. Remove any external wiring from the motorterminals.

Figure 6-63.—Hermetic unit analyzer.

3. Place the analyzer plugs in the jacks of the samecolor. If a split-phase motor is used, put the redplug in jack No. 3; if the capacitor-start motor isused, put the red plug in jack No. 4; and select acapacity value close to the old one with thetoggle switches.

4. Connect the test clips as follows:

White to common

Black to the running winding

Red to the starting winding

5. Hold the push-to-start button down and at thesame time move the handle of the rocker switchfrom normal to reverse. The frequency ofrocking should not exceed five times within a15-second period. If the motor starts, be certainthat the rocker switch is in the normal positionbefore releasing the push-to-start button.

6. More tests can be made with the hermetic unitanalyzer, such as testing for continuity ofwindings and for grounded windings.Procedures for these tests are provided in themanual that comes with the analyzer.Generally, if the rocking procedure does notresult in a free and running motor, the unit mustbe replaced.

TROUBLESHOOTING REFRIGERATIONEQUIPMENT

Troubleshooting of any type of refrigeration unitdepends, in part, on your ability to compare normaloperation with that obtained from the unit beingoperated. Obviously for you to detect these abnormaloperations, you must first know what normal operationis. Climate affects running time. A refrigeration unitgenerally operates more efficiently in a dry climate. Inan ambient temperature of 75°F, the running periodusually approximates 2 to 4 minutes, and the offperiod, 12 to 20 minutes.

It is beyond the scope of this text to cover all of thetroubles you may encounter in working withrefrigeration equipment. If you apply yourself, youcan acquire a lot of additional information throughon-the-job training and experience and studying themanufacturer's instruction manuals.

First and foremost, safety must be stressed and safeoperating practices followed before and while doingany troubleshooting or service work. All local and

6-50

Fire extinguishers must be readily available, ingood working order, and adequate for thesituation.

Safety tags with such notations as "Danger,""Hands Off," "Do Not Operate," and "Do NotThrow Switch" should be attached to valves,switches, and at other strategic locations whenservicing or making repairs.

Install machinery guards properly beforeoperating machinery.

national codes, as well as DoD rules concerning safety,must be observed. Some of the more important safetysteps that are often overlooked are as follows:

Protective equipment, such as eye protection,gloves, hard hats, and so forth, must be availableand worn.

The above is only a short list and not intended to beall-inclusive. You will also find table W, appendix II,"Troubleshooting — Industrial Refrigeration," andtable Y, appendix II, "Troubleshooting — DomesticRefrigerators and Freezers," useful guides for locatingand correcting different troubles in refrigerationequipment.

Q46.

Q47.

Q48.

Q49.

Q50.

Q51.

Q52.

Q53.

Most problems with electrical motors forrefrigeration system compressors fall into whatclasses?

How often is the coupling on the shafts of directdrive motors realigned?

What piece of equipment is installed in arefrigeration system just before the expansionvalve to remove moisture?

Manually defrosting is normally required onrefrigeration units that operate at whattemperature?

If you suspect a component is open, you shouldtest the source in what way?

What unit of measurement on a multimeter doyou use to test for a short?

When checking for a ground, you use the sametroubleshooting procedure as used for whatother problem?

Troubleshooting a refrigeration system dependspartly on your knowledge of how the equipmentruns normally. True/False.

LOGS

Learning Objective: Understand the importance anduse of maintaining, operating, and inspecting logs forrefrigeration equipment.

When maintaining, standing watch, operating, orinspecting refrigerating and air-conditioningequipment, the Utilitiesman may be responsible forkeeping operation, inspection, or maintenance logs onthe equipment. Try to keep the logs neat and clean.You must ensure that any information recorded inthem is accurate and legible.

Operation and maintenance logs may help to spottrouble in the equipment. They also aid in ensuringproper periodic maintenance and inspection areperformed on the equipment. Logs may provide ameans of self-protection when trouble occurs and thecause can be placed on an individual.

Good judgment must always be used in analysis ofservice troubles and specific corrections should befollowed whenever possible. One of the methods fordetermining when and what corrective measures arenecessary on equipment or a plant which is notoperating properly is to compare the pressures andtemperatures of various parts of the system withcorresponding readings taken in the past when theequipment or plant was operating properly undersimilar heat load and circulating water temperatureconditions.

A typical operating log may contain entries such asthe following:

Oil level in the compressor

Operating hours

Evaporator pressure and temperature

Condenser pressure and temperature

Discharge pressure and tem perature readings

Suction pressure and temperature readings

Ambient temperature

Date and time of readings

These types of readings give a complete picture ofthe current and past operating conditions of theequipment or plant and can assist the Utilitiesman inkeeping the equipment or plant at its maximumefficiency.

Maintenance logs contain entries of when, what,and who performed routine periodic maintenance on

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the equipment or plant. Such logs help ensure that theequipment or plant is well maintained and that the lifeexpectancy of the equipment or plant is fully used.These logs also can assist in determining estimates forfuture budget requirements for maintenance on theequipment or plant. Maintenance log entries mayinclude the following:

Date of maintenance

Type of maintenance

What was done

Who did the work

Cost of the work

Materials used

It is important to compare operating log readingsof the equipment or plant before the maintenance withthose taken after the maintenance was completed toensure maintenance was accomplished properly, andthat it had no ill effects on the equipment or plant.

Q54. Operating and maintenance logs can assist inspotting troubles in refrigeration equipment orplants. True/False.

Q55. Maintenance logs can be used to figure futuremaintenance cost requirements. True /False.

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CHAPTER 7

AIR CONDITIONING

Learning Objectives: Understand the principles of air conditioning and the operationof basic air-conditioning systems. Recognize the characteristics and proceduresrequired to install, operate, and maintain air-conditioning systems

Air conditioning is the simultaneous control oftemperature, humidity, air movement, and the qualityof air in a conditioned space or building. The intendeduse of the conditioned space is the determining factorfor maintaining the temperature, humidity, airmovement, and quality of air. Air conditioning is ableto provide widely varying atmospheric conditionsranging from conditions necessary for dryingtelephone cables to that necessary for cotton spinning.Air conditioning can maintain any atmosphericcondition regardless of variations in outdoor weather.

This chapter explains the following subjects as theypertain to air conditioning: principles of airconditioning, heat pumps, chilled-water systems,periodic maintenance, cooling towers, troubleshooting,automotive air conditioning, and ductwork.

PRINCIPLES OF AIR CONDITIONING

Learning Objective: Understand the basic principlesof temperature, humidity, and air motion in relation toair conditioning.

Air conditioning is the process of conditioning theair in a space to maintain a predetermined temperature-humidity relationship to meet comfort or technicalrequirements. This warming and cooling of the air isusually referred to as winter and summer airconditioning.

Here, you are introduced to the operating principlesof air-conditioning systems, the environmental factorscontrolled by air conditioning, and their effects onhealth and comfort. Refrigerative air conditioners andgeneral procedures pertaining to the installation,operation, and maintenance of these systems areexamined. Also, the operation and maintenance of thecontrols used with these systems are explained.

TEMPERATURE

Temperature, humidity, and air motion areinterrelated in their effects on health and comfort. Theterm given to the net effects of these factors is effectivetemperature. This effective temperature cannot bemeasured with a single instrument; therefore, apsychrometric chart aids in calculating the effectivetemperature when given sufficient known conditionsrelating to air temperatures and velocity.

Research has shown that most persons arecomfortable in air where the effective temperature lieswithin a narrow range. The range of effectivetemperatures within which most people feelcomfortable is called the COMFORT ZONE. Sincewinter and summer weather conditions are markedlydifferent, the summer zone varies from the winterzone. The specific effective temperature within thezone at which most people feel comfortable is calledthe COMFORT LINE (fig. 7-1).

HUMIDITY

Air at a high temperature and saturated withmoisture makes us feel uncomfortable. However, withthe same temperature and the air fairly dry, we mayfeel quite comfortable. Dry air, as it passes over thesurface of the skin, evaporates the moisture soonerthan damp air and, consequently, produces greatercooling effect. However, air may be so dry that itcauses us discomfort. Air that is too dry causes thesurface of the skin to become dry and irritates themembranes of the respiratory tract.

HUMIDITY is the amount of water vapor in agiven volume of air. RELATIVE HUMIDITY is theamount of water vapor in a given amount of air incomparison with the amount of water vapor the airwould hold at a temperature if it were saturated.Relative humidity may be remembered as a fraction orpercentage of water vapor in the air; that is, DOESHOLD divided by CAN HOLD.

7-1

Figure 7-1.—Comfort zones and lines.

Relative humidity is determined by using a slingpsychrometer. It consists of a wet-bulb thermometerand a dry-bulb thermometer, as shown in figure 7-2.The wet-bulb thermometer is an ordinary thermometersimilar to the dry-bulb thermometer, except that thebulb is enclosed in a wick that is wet with distilledwater. The wet bulb is cooled as the moistureevaporates from it while it is being spun through theair. This action causes the wet-bulb thermometer toregister a lower temperature than the dry-bulbthermometer. Tables and charts have been designedthat use these two temperatures to arrive at a relativehumidity for certain conditions.

A comfort zone chart is shown in figure 7-3. Thecomfort zone is the range of effective temperatures

within which the majority of adults feel comfortable.In looking over the chart, note that the comfort zonerepresents a considerable area. The charts show thewet- and dry-bulb temperature combinations that arecomfortable to the majority of adults. The summercomfort zone extends from 66°F effective temperatureto 75°F effective temperature for 98 percent of allpersonnel. The winter comfort zone extends from 63°Feffective temperature to 71°F effective temperature for97 percent of all personnel.

Dew-Point Temperature

The dew point depends on the amount of watervapor in the air. If the air at a certain temperature is not

Figure 7-2.—A standard sling psychrometer.

7-2

Figure 7-3.—Comfort zone chart.

saturated (maximum water vapor at that temperature)and the temperature of that air falls, a point is finallyreached at which the air is saturated for the new and

lower temperature, and condensation of the moisturebegins. This is the dew-point temperature of the air for

the quantity of water vapor present.

Relationship of Wet-Bulb, Dry-Bulb, andDew-Point Temperatures

A definite relationship exists between the wet-bulb,dry-bulb, and dew-point temperatures. These

relationships are as follows:

When the air is not saturated but contains somemoisture, the dew-point temperature is lowerthan the dry-bulb temperature, and the wet-bulbtemperature is in between.

As the amount of moisture in the air increases,the amount of evaporation (and, therefore,cooling) decreases. The difference between thetemperatures becomes less.

When the air becomes saturated, all threetemperatures are the same and the relativehumidity is 100 percent.

To HUMIDIFY air is to increase its water vaporcontent. To DEHUMIDIFY air is to decrease its watervapor content. The device used to add moisture to theair is a humidifier, and the device used to remove themoisture from the air is a dehumidifier. The controldevice, sensitive to various degrees of humidity, iscalled a HUMIDISTAT.

Methods for humidifying air in air-conditioningunits usually consist of an arrangement that causes airto pick up moisture. One arrangement consists of a

7-3

heated water surface over which conditioned air passesand picks up a certain amount of water vapor byevaporat ion, depending upon the degree ofhumidifying required. A second arrangement tohumidify air is to spray or wash the air as it passesthrough the air-conditioning unit.

During the heat of the day, the air usually absorbsmoisture. As the air cools at night, it may reach the dewpoint and give up moisture, which is deposited onobjects. This principle is used in dehumidifying air bymechanical means.

Dehumidifying equipment for air conditioningusually consists of cooling coils within the airconditioner. As warm, humid air passes over thecooling coils, its temperature drops below the dewpoint and some of its moisture condenses into water onthe surface of the coils. The condensing moisture givesup latent heat that creates a part of the cooling load thatmust be overcome by the air-conditioning unit. For thisreason, the relative humidity of the air entering the airconditioner has a definite bearing on the total coolingload. The amount of water vapor that can be removedfrom the air depends upon the air over the coils and thetemperature of the coils.

PURITY OF AIR

The air should be free from all foreign materials,such as ordinary dust, rust, animal and vegetablematter, pollen, carbon (soot) from poor combustion,fumes, smoke, and gases. These types of pollution areharmful to the human body alone; however, theyinclude an additional danger because they also carrybacteria and harmful germs. So, the outside air broughtinto a space or the recirculating air within a spaceshould be filtered during air conditioning.

Air in an air conditioner may be purified or cleanedby filters, air washing, or electricity.

Filters may be designed as permanent orthrowaway types. They are usually made of fibrousmaterial, which collects the particles of dust and otherforeign matter from the air as it passes through thefilter. In some cases, the fibers are dry, while in othersthey have a viscous (sticky) coating. Filters usuallyhave a large dust-holding capacity. When filtersbecome dust-laden, they are either discarded orcleaned. Permanent filters are usually cleaned.Throwaway filters are only one-time filters and arediscarded when they become dust-laden.

Often water sprays are used to recondition the airby washing and cleaning it. These sprays may alsoserve to humidify or dehumidify the air to some extent.

In some large air-conditioning systems, air iscleaned by electricity. In this type of system, electricalprecipitators remove the dust particles from the air.The air is first passed between plates where the dustparticles are charged with electricity; then the air ispassed through a second set of oppositely chargedplates that attract and remove the dust particles (fig.7-4). This method is by far the best method of aircleaning, but the most expensive.

CIRCULATION OF AIR

The velocity of the air is the primary factor thatdetermines what temperature and humidity arerequired to produce comfort. (The chart in figure 7-3 isbased on an air movement of 15 to 25 feet per minute.)We know from experience that a high velocity of airproduces a cooling effect on human beings. However,air velocity does not produce a cooling effect on asurface that does not have exposed moisture. A fandoes not cool the air, but merely increases its velocity.The increased velocity of air passing over the skinsurfaces evaporates moisture at a greater rate; thereby,cooling the individual. For this reason, circulation ofair has a decided influence on comfort conditions. Aircan be circulated by gravity or mechanical means.

When air is circulated by gravity, the cold, andtherefore heavier, air tends to settle to the floor, forcingthe warm and lighter air to the ceiling. When the air atthe ceiling is cooled by some sort of refrigeration, itwill settle to the floor and cause the warm air to rise.The circulation of the air by this method willeventually stop when the temperature of the air at theceiling is the same as the temperature on the floor.

Air may be circulated by mechanical means byaxial or radial fans. When either the axial or radial fanis mounted in an enclosure, it is often called a blower.

Q1. What is the term given to the net effects oftemperature, humidity, and air motion?

Q2. The comfort line is the specific effectivetemperature at which most people feelcomfortable. True /False

Q3. What is the term for the amount of water vapor ina given volume of air?

Q4. What instrument is used to measure relativehumidity?

7-4

Figure 7-4.—Diagram of an electrostatic filter.

Q5. The point where water vapor condenses is calledthe dew point. True /False

Q6. What condition exists when the dry-bulb,wet-bulb, and dew-point temperatures are thesame?

Q7. What are the two types of filter designs?

Q8. What is the primary factor that determines thetemperature and humidity required for roomcomfort?

AIR-CONDITIONING SYSTEMS

Learning Objective: Recognize basic types ofair-conditioning systems, and understand the operation,maintenance, and repair methods and procedures.

A complete air-conditioning system includes ameans of refrigeration, one or more heat transfer units,air filters, a means of air distribution, an arrangementfor piping the refrigerant and heating medium, andcontrols to regulate the proper capacity of thesecomponents. In addition, the application and designrequirements that an air-conditioning system mustmeet make it necessary to arrange some of thesecomponents to condition the air in a certain sequence.

For example, an installation that requires re-heating ofthe conditioned air must be arranged with there-heating coil on the downstream side of thedehumidifying coil; otherwise, re-heating of thecooled and dehumidified air is impossible.

There has been a tendency by many designers toclassify an air-conditioning system by referring to oneof its components. For example, the air-conditioningsystem in a building may include a dual ductarrangement to distribute the conditioned air;therefore, it is then referred to as a dual duct system.This classification makes no reference to the type ofrefrigeration, the piping arrangement, or the type ofcontrols.

For the purpose of classification, the followingdefinitions are used:

An air-conditioning unit is understood to consistof a heat transfer surface for heating and cooling,a fan for air circulation, and a means of cleaningthe air, motor, drive, and casing.

A self-contained air-conditioning unit isunderstood to be an air-conditioning unit that iscomplete with compressor, condenser,evaporator, controls, and casing.

7-5

An air-handling unit consists of a fan, heat

transfer surface, and casing.

A remote air-handling unit or a remote

air-conditioning unit is a unit located outside of

the conditioned space that it serves.

SELF-CONTAINED AIR-CONDITIONING

UNITS

Self-contained air-conditioning units may bedivided into two types: window-mounted andf l o o r - m o u n t e d u n i t s . W i n d o w - m o u n t e dair-conditioning units usually range from 4,000 to36,000 Btu per hour in capacity (fig. 7-5). The use ofwindows to install these units is not a necessity. Theymay be installed in transoms or directly in the outsidewalls (commonly called a "through-the-wall"installation). A package type of room air conditioner,showing airflow patterns for cooling, ventilating, andexhausting services, is shown in figure 7-6.

In construction and operating principles, thewindow unit is a small and simplified version of muchlarger systems. As shown in figures 7-7 and 7-8, thebasic refrigeration components are present in thewindow unit. The outside air cools the condenser coils.The room air is circulated by a fan that blows across theevaporator coils. Moisture, condensed from the humidair by these coils, is collected in a pan at the bottom ofthe unit; it is usually drained to the back of the unit anddischarged. Most window units are equipped withthermostats that maintain a fixed dry-bulb temperatureand moisture content in an area within reasonablelimits. These units are installed so there is a slight tilt ofthe unit towards the outside, toward the condenser, toassist in drainage of the condensate. It is a good idea tomount the unit on the eastside of the building to takeadvantage of the afternoon shade. These units requirevery little mechanical attention before they are put intooperation. Window units are normally operated by theuser who should be properly instructed on their use.

Floor-mounted air-conditioning units range in sizefrom 24,000 to 360,000 Btu per hour and are also

Figure 7-5.—Window air conditioner.

7-6

Figure 7-6.—Package type of air-conditioning unit showing airflow patterns.

Figure 7-7.—A refrigerant cycle of a package air conditioner.

Figure 7-8.—Air-handling components of a package type of room air conditioner.

referred to as PACKAGE units, as the entire system islocated in the conditioned space. These larger units,like window units, contain the complete system ofrefrigeration components. A self-contained unit withpanels removed is shown in figure 7-9. These units

normally use either a water-cooled or air-cooledcondenser.

Self-contained units should be checked regularlyto ensure they operate properly. Filters should be

7-7

Figure 7-9.—A floor-mounted air-conditioning unit.

renewed or cleaned weekly or more often if necessary.Always stop the blower when changing filters to keeploose dust from circulating through the system. Whenthe filters are permanent, they should be returned to theshop for cleaning. At least once a year, the unit shouldbe serviced. When the unit is designed with sprayhumidifier, spray nozzle, water strainers, and coolingcoils, each device should be cleaned each month toremove water solids and scale. Cooling coil casings,drain pans, fan scrolls, and fan wheels should be wirebrushed and repainted when necessary. Oiling andgreasing of the blower and motor bearings should beperformed as required.

HEAT PUMPS

A heat pump removes heat from one place and putsit into another. A domestic refrigerator is a heat pumpin that it removes heat from inside a box and releases iton the outside. The only difference between a

refrigerator and a residential or commercial heat pumpis that the latter can reverse its system. The heat pumpis one of the most modern means of heating andcooling. Using no fuel, the electric heat pumpautomatically heats or cools as determined by outsidetemperature. The air type of unit works on the principleof removing heat from the atmosphere. No matter howcold the weather, some heat can always be extractedand pumped indoors to provide warmth. To coolduring the hot months, this cycle is merely reversedwith the unit removing heat from the area to be cooledand exhausting it to the outside air. The heat pump isdesigned to control the moisture in the air and toremove dust and pollen. Cool air, provided during hotweather, enters the area with uncomfortable moistureremoved. In winter, when a natural atmosphere isdesirable, air is not dried out when pumped indoors.

The heat pump is simple in operation (fig. 7-10).In summer, the evaporator is cooling and the condenseroutside is giving off heat the evaporator picked up. In

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winter, the condenser outside is picking up heat from

the outside air because its temperature is lower than

that of the outside air (until it reaches the balance

point). This heat is then sent to the evaporator by the

compressor and is given off into the conditioned space.

A reversing valve is the key to this operation. The

compressor always pumps in one direction, so the

reversing valve changes the hot-gas direction from the

condenser to the evaporator as indicated by the setting

on the thermostat. The setting of the thermostat

assures the operator of a constant temperature through

an automatic change from heating to cooling anytime

outside conditions warrant. Heat pumps are made not

only for small homes but large homes and commercial

buildings as well. The heat pump does not require an

equipment room, and its minor noise is discharged into

the atmosphere. The remote heat pump has only a

blower and evaporator, which can be installed under

the floor, in an attic, or other out-of-the-way location,

depending on the application and its requirements.

Supplemental heat can be added into the duct and be set

to come on by a second stage of the thermostat, an

outside thermosat, or both, depending on design of thesys tem.

Heating Cycle

The initial heating demand of the thermostat startsthe compressor. The reversing valve is de-energizedduring the heating mode. The compressor pumps thehot refrigerant gas through the indoor coil where heatis released into the indoor air stream. This supply ofwarmed air is distributed through the conditionedspace. As the refrigerant releases its heat, it changesinto a liquid, which is then transported to the outdoorcoil. The outdoor coil absorbs heat from the air blownacross the coil by the outdoor fan. The refrigerantchanges from a liquid into a vapor, as it passes throughthe outdoor coil. The vapor returns to the compressorwhere it increases temperature and pressure. The hotrefrigerant is then pumped back to the indoor coil tostart another cycle. A graphic presentation of the ninesteps of the cycle is shown in figure 7-11.

Cooling Cycle

Once the thermostat is put in the cooling mode, thereversing valve is energized. A cooling demand startsthe compressor. The compressor pumps hothigh-pressure gas to the outdoor coil where heat isreleased by the outdoor fan. The refrigerant changesinto a liquid, which is transported to the indoor blower.The refrigerant absorbs heat from the indoor air of the

Figure 7-10. —Basic heat pump operation.

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Figure 7-11.—Heating cycle.

supply air, which is distributed throughout the Supplemental Heatcontrolled space. This temperature change removesmoisture from the air and forms condensate, whichmust be piped away. The compressor suction pressuredraws the cool vapor back into the compressor wherethe temperature and pressure are greatly increased.This completes the cooling refrigerant cycle. Agraphic presentation of the nine steps of the cycle isshown in figure 7-12.

Defrost Cycle

As the outside temperature drops, the heat pumpruns for longer periods until it eventually operatescontinually to satisfy the thermostat. The system"balance point" is when the heat pump capacityexactly matches the heating loss. The balance pointvaries between homes, depending on actual heat lossand the heat pump capacity. However, the balancepoint usually ranges between 15°F and 40°F. Eitherelectric heat or fossil fuels provide the auxiliary heat.

Heat pumps operating at temperatures below 45°Faccumulate frost or ice on the outdoor coil. Therelative humidity and ambient temperature affect thedegree of accumulation. This ice buildup restricts theairflow through the outdoor coil, which consequentlyaffects the system operating pressures. The defrostcontrol detects this restriction and switches the unitinto a defrost mode to melt the ice.

The reversing valve is energized and the machinetemporarily goes into the cooling cycle where hotrefrigerant flows to the outdoor coil. The outdoor fanstops at the same time, thus allowing the dischargetemperature to increase rapidly to shorten the length ofthe defrost cycle. If there is supplemental heat, adefrost relay activates it to offset the cooling releasedby the indoor coil.

Conventional heat pump applications use electricheaters downstream from the indoor coil. This designprevents damaging head pressures when the heat pumpand auxiliary heat run simultaneously. The indoor coilcan only be installed downstream from the auxiliaryheat if a "fuelmaster" control system is used. Thiscontrol package uses a two-stage heat thermostat withthe first stage controlling heat pump operation and thesecond stage controlling furnace operation.

CHILLED-WATER SYSTEMS

Water chillers (figs. 7-13 and 7-14) are used in airconditioning for large tonnage capacities and forcentral refrigeration plants serving a number of zones,each with its individual air-cooling and air-circulating

7-10

Figure 7-12.—Cooling cycle.

Figure 7-13.—Rotary screw compressor unit.

7-11

Figure 7-14.—Two-stage semihermetic centrifugal unit.

units. An example is a large hospital with wings off acorridor. Air conditioning may be necessary inoperating rooms, treatment suites, and possibly somerecovery wards. Chilled water-producing andwater-circulating equipment is in a mechanicalequipment room. Long mains with many jointsbetween condensing equipment and conditioning unitsincrease the chance of leaks. Expensive refrigerant hasto be replaced. I t may be better to providewater-cooling equipment close to the condensing unitsand to circulate chilled water to remote air-coolingcoils . Chil led water is circulated to variousroom-located coils by a pump, and the temperature ofthe air leaving each coil may be controlled by athermostat that controls a water valve or stops andstarts each cooling coil fan motor.

Types of Coolers

The two most commonly used water coolers(evaporators) for chilled water air conditioning areflooded shell-and-tube and dry-expansion coolers.The disadvantage of the flooded shell-and-tube cooler

is that it needs more refrigeration than other systems ofequal size. Furthermore, water in tubes may freeze andsplit tubes when the load falls off.

Controls

Flooded coolers should be controlled with alow-pressure float control-a float valve placed so thefloat is about the same level as the predeterminedrefrigerant level. The float, as a pilot, moves a valve inthe liquid line to control the flow of refrigerant to theevaporator. Automatic or thermostatic expansionvalves control the dry-expansion coolers. Therefrigerant is inside the tubes; therefore, freezing ofwater on the tubes is less likely to cause damage.

Condensers

The primary purpose of the condenser is to liquefythe refrigerant vapor. The heat added to the refrigerantin the evaporator and compressor must be transferredto some other medium from the condenser. Thismedium is the air or water used to cool the condenser.

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W A T E R - C O O L E D C O N D E N S E R S .—Condensing water must be noncorrosive, clean,inexpensive, below a certain maximum temperature,and available in sufficient quantity. The use ofcorrosive or dirty water results in high maintenancecosts for condensers and piping. Dirty water, as from ariver, can generally be economically filtered if it isnoncorrosive; corrosive water can sometimes beeconomically treated to neutralize its corrosiveproperties if it is clean. An inexpensive source of waterthat must be filtered and chemically treated willprobably not be economical to use without some meansof conservation, such as an evaporative condenser or acooling tower.

Water circulated in evaporative condensers andcooling towers must always be treated to reduce theformation of scale, algae, and chalky deposits.Overtreatment of water, however, can waste costlychemicals and result in just as much maintenance asundertreatment.

SHELL-AND-COIL CONDENSERS.—Ashell-and-coil water-cooled condenser (fig. 7-15) issimply a continuous copper coil mounted inside a steelshell. Water flows through the coil, and the refrigerantvapor from the compressor is discharged inside theshell to condense on the outside of the cold tubes. Inmany designs, the shell also serves as a liquid receiver.

The shell-and-coil condenser has a lowmanufacturing cost, but this advantage is offset by thedisadvantage that this type of condenser is difficult toservice in the field. If a leak develops in the coil, thehead from the shell must be removed and the entire coilpulled from the shell to find and repair the leak. Acontinuous coil is a nuisance to clean, whereas straighttubes are easy to clean with mechanical tube cleaners.In summary, with some types of cooling water, it may

be difficult to maintain a high rate of heat transfer witha shell-and-coil condenser.

SHELL-AND-TUBE CONDENSERS.—Theshell-and-tube water-cooled condenser shown infigure 7-16 permits a large amount of condensingsurface to be installed in a comparatively small space.The condenser consists of a large number of 3/4- or5/8-inch tubes installed inside a steel shell. The waterflows inside the tubes while the vapor flows outsidearound the nest of tubes. The vapor condenses on theoutside surface of the tubes and drips to the bottom ofthe condenser, which may be used as a receiver for thestorage of l iquid refr igerant . Shell-and-tubecondensers are used for practically all water-cooledrefrigeration systems.

To obtain a high rate of heat transfer through thesurface of a condenser, it is necessary for the water topass through the tubes at a fairly high velocity. For thisreason, the tubes in shell-and-tube condensers areseparated into several groups with the same watertraveling in series through each of these variousgroups. A condenser having four groups of tubes isknown as a four-pass condenser because the waterflows back and forth along its length four times.Four-pass condensers are common although anyreasonable number of passes may be used. The fewerthe number of water passes in a condenser, the greaterthe number of tubes in each pass.

The friction of water flowing through a condenserwith a few passes is lower than in one having a largenumber of passes. This means a lower power cost inpumping the water through a condenser with a smallernumber of passes.

TUBE-WITHIN-A-TUBE CONDENSERS.—The use of tube-within-a-tube for condensing purposesis popular because it is easy to make. Water passing

Figure 7-15.—A typical shell-and-coil water-cooled condenser.

7-13

Figure 7-16.—A typical shell-and-tube condenser-liquid receiver.

through the inner tube along with the exterior aircondenses (fig 7-17) the refrigerant in the outer tube.This "double cooling" improves efficiency of thecondenser. Water enters the condenser at the pointwhere the refrigerant leaves the condenser. It leavesthe condenser at the point where the hot vapor from thecompressor enters the condenser. This arrangement iscalled counterflow design.

The rectangular type of tube-within-a-tubecondenser uses a straight, hard copper pipe with

Figure 7-17.—Tube-within-a-tube condenser designed to The simplest method of removing scale and dirtpermit cleaning of water tubes. from condenser tubes not accessible for mechanical

manifolds on the ends. When the manifolds areremoved, the water pipes can be cleaned mechanically.

CLEANING WATER-COOLEDCONDENSERS

You may be assigned to some activities wherewater-cooled condensers are used in theair-conditioning system. So, the Utilitiesman willprobably have the job of cleaning the condensers.Information that assists you in cleaning water-cooledcondensers is presented below.

Water contains many impurities—the content ofwhich varies in different localities. Lime and iron areespecially injurious; they form a hard scale on thewalls of water tubes that reduces the efficiency of thecondenser. Condensers can be cleaned mechanicallyor chemically.

Scale on tube walls of condensers with removableheads is removed by attaching a round steel brush to arod and by working it in and out of the tubes. After thetubes have been cleaned with a brush, flush them byrunning water through them. Some scale deposits areharder to remove than others, and a steel brush may notdo the job. Several types of tube cleaners for removinghard scale can usually be purchased from local sources.Be sure that the type selected does not injure watertubes.

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cleaning is by using inhibited acid to clean coils ortubes through chemical action. Figure 7-18 shows theconnections and the equipment for cleaning thecondenser with an inhibited acid, both when the acidflows by gravity (view 1) and when forced circulationis used (view 2). When scale deposit is not great,gravity flow of the acid provides enough cleaning.When the deposit almost clogs the tubes, forcedcirculation should be used.

WARNING

Preven t chemica l so lu t ion f romsplashing in your eyes and on your skinor clothing.

Equipment and connections for circulatinginhibited acid through the condenser using gravityflow, as shown in figure 7-18, view 1, are as follows:

1. A rubber or plastic bucket for mixing solution.Do not use galvanized materials because prolongedcontact with acid deteriorates such surfaces.

2. A crock or wooden bucket for catching thedrainage residue.

3. One-inch steel pipe that is long enough to makethe connections shown.

4. Fittings for l-inch steel pipe. The vent pipeshown should be installed at the higher connection ofthe condenser.

Equipment and connections for circulatinginhibited acid through the condenser using forcedcirculation, as shown in figure 7-18, are as follows:

1. A pump suitable for this application. Acentrifugal pump and a 1/2-horsepower motor isrecommended (30 gallons per minute at 35-foot headcapacity).

2. A nongalvanized metal tank, stone or porcelaincrock, or wooden barrel with a capacity of about 50gallons with ordinary bronze or copper screening tokeep large pieces of scale or dirt from getting into thepump intakes.

3. One-inch pipe that is long enough to make thepiping connections shown.

4. Fittings for l-inch steel globe valves. The ventpipe, as shown, should be installed at the higherconnection of the condenser.

Handle the inhibited acid for cleaning condenserswith the usual precautions observed when handlingacids. It stains hands and clothing and attacks concreteand if an inhibitor is not present, it reacts with steel.Therefore, use every precaution to prevent spilling orsplashing. When splashing might occur, cover thesurfaces with burlap or boards. Gas produced duringcleaning that escapes through the vent pipe is notharmfu but prevents any liquid or spray from beingcarried hrough with the gas. The basic formula should

Figure 7-18.—Cleaning water-cooled condensers with acidsolution.

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be maintained as closely as possible, but a variation of5 percent is permissible. The inhibited acid solution ismade up of the following:

1. Water.

2. Commercial hydrochloric (muriatic) acid withspecific gravity of 1.19. Eleven quarts of acid should beused for each 10 gallons of water.

3. Three and two-fifths ounces of inhibitor powderfor each 10 gallons of water used.

4. Place the required amount of water in anongalvanized metal tank or wooden barrel, and add thenecessary amount of inhibitor powder while stirring thewater. Continue stirring the water until the powder iscompletely dissolved; then add the required quantity ofacid.

WARNING

NEVER add water to acid; this mistakemay cause an explosion.

In charging the system with an acid solution whenGRAVITY FLOW is used, introduce the inhibited acidas shown in figure 7-18. Do not add the solution fasterthan the vent can exhaust the gases generated duringcleaning. When the condenser has been filled, allowthe solution to remain overnight.

When FORCED CIRCULATION is used, thevalve in the vent pipe should be fully opened while thesolution is introduced into the condenser but must beclosed when the condenser is completely charged andthe solution is circulated by the pump. When acentrifugal pump is used, the valve in the supply linemay be fully closed while the pump is running.

The solution should be allowed to stand or becirculated in the system overnight for cleaning outaverage scale deposits. The cleaning time alsodepends on the size of the condenser to be cleaned. Forextremely heavy deposits, forced circulation isrecommended, and the time should be increased to 24hours. The solution acts more rapidly if it is warm, butthe cleaning action is just as thorough with a coldsolution if adequate time is allowed.

After the solution has been allowed to stand or hasbeen circulated for the required time through thecondenser, it should be drained and the condenserthoroughly flushed with water. To clean condenserswith removable heads by using inhibited acid, use theabove procedure without removing the heads.

MAINTENANCE

A well-planned maintenance program avoidsunnecessary downtime, prolongs the life of the unit,and reduces the possibility of costly equipment failure.It is recommended that a maintenance log bemaintained for recording the maintenance activities.This action provides a valuable guide and aids inobtaining extended length of service from the unit.This sect ion describes specif ic maintenanceprocedures, which must be performed as a part of themaintenance program of the unit. Use and follow themanufacturer’s manual for the unit you are to domaintenance on. When specific directions orrequirements are furnished, follow them. Beforeperforming any of these operations, however, ensurethat power to the unit is disconnected unless otherwiseinstructed.

However, extra precaution must be exercised influshing out the condenser with clear water after theacid has been circulated through the condenser toensure acid removal from all water passages.

WARNING

W h e n m a i n t e n a n c e c h e c k s a n dprocedures must be completed with theelectrical power on, care must be taken toa v o i d c o n t a c t w i t h e n e r g i z e dcomponents or moving parts. Failure toexercise caution when working withelectrically powered equipment mayresult in serious injury or death.

Coil Cleaning

Refrigerant coils must be cleaned at least once ayear or more frequently if the unit is located in a dirtyenvironment. This action helps maintain unitoperating efficiency and reliability. The relationshipbetween regular coil maintenance and efficient/reliable unit operation is as follows:

Clean condenser coils minimize compressorhead pressure and amperage draw and promotesystem efficiency.

Clean evaporator coils minimize watercarry-over and helps eliminate frosting and/orcompressor flood-back problems.

7-16

Clean coils minimize required fan brakehorsepower and maximize efficiency by keepingcoil static pressure loss at a minimum.

Clean coils keep the motor temperature andsystem pressure within safe operating limits forgood reliability.

The following equipment is required to cleancondenser coils: a soft brush and either a gardenpump-up sprayer or a high-pressure sprayer. Inaddition, a high-quality detergent must be used.Follow the manufacturer's recommendations formixing to make sure the detergent is alkaline with a pHvalue less than 8.5.

Specific steps required for cleaning the condensercoils are as follows:

1. Disconnect the power to the unit.

WARNING

Open the unit disconnect switch. Failureto disconnect the unit from the electricalpower source may result in severeelectrical shock and possible injury ordeath.

2. Remove enough panels from the unit to gainaccess to the coil.

3. Protect all electrical devices, such as motors andcontrollers, from dust and spray.

4. Straighten coil fins with a fin rake, if necessary.

5. Use a soft brush to remove loose dirt and debrisfrom both sides of the coil.

6. Mix the detergent with water according to themanufacturer's instructions. The detergent andwater solution may be heated to a maximum of150°F to improve its cleaning ability.

WARNING

Do not heat the detergent and watersolution to temperatures in excess of150°F. High-temperature l iquidssprayed on the coil exterior raise thepressure within the coil and may cause itto burst. Should this occur, the resultcould be both injury to personnel andequipment damage.

7. Place the detergent and water solution in thesprayer. If a high-pressure sprayer is used, besure to follow these guidelines:

Minimmum nozzle spray angle is 15 degrees.

Spray the solution perp endicular (at a90-degree angle) to the coil face.

Keep the sprayer nozzle at least 6 inches fromthe coil.

Sprayer pressure must not exceed 600 psi.

CAUTION

Do NOT spray motors or other electricalcomponents. Moisture from the spraycan cause component failure.

8. Spray the side of the coil where the air leavesfirst; then, spray the other side (where the airenters). Allow the detergent and water solutionto stand on the coil for 5 minutes.

9. Rinse both sides of the coil with cool water.

10. Inspect the coil and if it still appears dirty, repeatSteps 8 and 9.

11. Remove the protective covers installed in Step3.

2. Replace all unit panels and parts, and restoreelectrical power to the unit.

Fan Motors

Inspect periodically for excessive vibration ortemperature. Operating conditions vary the frequencyof inspection and lubrication. Motor lubricationinstructions are found on the motor tag or nameplate. Ifnot available, contact the motor manufacturer forinstructions.

To re-lubricate the motor, complete the following:

WARNING

Disconnect the power source for motorlubrication. Failure to do so may result ininjury or death from electrical shock ormoving parts.

1. Turn the motor off. Make sure it cannotaccidentally restart.

7-17

2. Remove the relief plug and clean out anyhardened grease.

3. Add fresh grease through the fitting with alow-pressure grease gun.

4. Run the motor for a few minutes to expel anyexcess grease through the relief vent.

5. Stop the motor and replace the relief plug

Fan Bearing Lubrication

Fan bearings with grease fittings or with greasel ine extensions should be lubricated with alithium-base grease that is free of chemical impurities.Improper lubrication can result in early bearing failure.To lubricate the fan bearings, complete the following:

1. Lubricate the bearings while the unit is notrunning; disconnect the main power switch.

2. Connect a manual grease gun to the grease lineor fitting.

3. Add grease, preferably when the bearing iswarm, while turning the fan wheel manuallyuntil a light bead of grease appears at the bearinggrease seal.

Filters

To clean permanent filters, wash under a stream ofhot water to remove dirt and lint. Follow with a washof mild alkali solution to remove old filter oil. Rinsethoroughly and let dry. Recoat both sides of the filterwith filter oil and let dry. Replace the filter element inthe unit.

CAUTION

Always install filters with directionalarrows pointing toward the fans.

PERIODIC MAINTENANCE

Perform all of the indicated maintenanceprocedures at the intervals scheduled. This prolongsthe life of the unit and reduces the possibility of costlyequipment failure and downtime. A checklist shouldbe prepared which lists the required service operationsand the times at which they are to be performed. Thefollowing is a sample of such a list.

Weekly

1. Check the compressor oil level. If low, allowthe compressor to operate continually at full load for 3to 4 hours; check the oil level at 30-minute intervals. Ifthe level remains low, add oil.

2. Observe the oil pressure. The oil pressure gaugereading should be approximately 20 to 35 psi above thesuction pressure gauge reading.

3. Stop the compressor and check the shaft seal forexcessive oil leakage. If found, check the seal with arefrigerant leak detector (open compressor only).

4. Check the condition of the air filters andair-handling equipment. Clean or replace filters, asnecessary.

5. Check the general operating conditions, systempressures, refrigerant sight glass, and so forth.

Monthly

(Repeat Items 1 through 5)

6. Lubricate the fan and motor bearings, asnecessary. Obtain and follow the manufacturer’slubricant specifications and bearing care instructions.

7. Check the fan belt tension and alignment.

8. Tighten all fan sheaves and pulleys. If found tobe loose, check alignment before tightening.

9. Check the condition of the condensingequipment. Observe the condition of the condenser coilin the air-cooled condenser. Clean, as necessary. Checkthe cooling tower water in the water-cooled condenser.If algae or scaling is evident, water treatment is needed.Clean the sump strainer screen of the cooling tower.

Annually

(Repeat Items 1 through 9)

10. Drain all circuits of the water-condensingsystem. Inspect the condenser piping and clean anyscale or sludge from the tubes of the condenser.

11. If a cooling tower or evaporative condenser isused, flush the pumps and sump tank. Remove any rustor corrosion from the metal surfaces and repaint.

12. Inspect all motor and fan shaft bearings for signsof wear. Check the shafts for proper end-playadjustment.

7-18

13.

14.

15.

16.

Replace worn or frayed fan belts.

Clean all water strainers.

Check the condition of the ductwork.

Check the condition of the electrical contacts ofall contactors, starters, and controls. Remove thecondensing unit control box cover and inspect the panelwiring. All electrical connections should be secure.Inspect the compressor and condenser fan motorcontactors. If the contacts appear severely burned orpitted, replace the contactor. Do not clean the contacts.Inspect the condenser fan capacitors for visible damage.

S e a s o n a l S h u t d o w n

In preparation for seasonal shutdown, it isadvisable to pump down the system and valve off thebulk of the refrigerant charge in the condenser. Thisaction minimizes the quantity of refrigerant that mightbe lost due to any minor leak on the low-pressure sideof the system, and, in the case of the open compressor,refrigerant that might leak through the shaft seal.

The following steps should be followed for thehermetic compressor pump down.

1. Close the liquid line shutoff valve at thecondenser and start the system. When the suctionpressure drops to the cutout setting of the low-pressurecontrol, the compressor stops.

2. Open the compressor electrical disconnectswitch to prevent the compressor from restarting, andthen front-seat the compressor discharge and suctionvalves.

The following steps should be followed for theopen compressor pump down.

1. If the system is not equipped with gauges, installa pressure gauge in the back-seat port of the compressorsuction valve. Crack the valve off the backseat.

2. Close the liquid line shutoff valve at thecondenser.

3. Manually open the liquid line solenoid valve(s).If the valves do not have manual opening devices, lowerthe setting of the system temperature controller so thevalves are held open during the pump down.

4. Install a jumper wire across the terminals of thelow-pressure switch. Since the system suction pressureis to be pumped down below the cutout setting of the

low-pressure switch, the jumper is necessary to keep thecompressor running.

5. Start the compressor. Watching the suctionpressure gauge, stop the compressor by opening itselectrical disconnect switch when the gauge readingreaches 2 psig.

6. Front-seat the compressor discharge valve.

CAUTION

Do not allow the compressor to pump thesuction pressure into a vacuum. A slightpositive pressure is necessary to preventair and moisture from being drawn intothe system through minor leaks andthrough the now unmoving shaft seal.

7. Remove the jumper wire from the low-pressurecontrol.

8. Remove the gauge from the port of the suctionvalve; replace the port plug and front-seat the valve.

The following steps are required for all systems:

1. Using a refrigerant leak detector, check thecondenser and liquid receiver, if used, for refrigerantl e a k s .

2. Valve off the supply and return waterconnections of the water-cooled condenser. Allow thecondenser to remain full of water during the off season.A drained condenser shell is more likely to rust andcorrode than one full of water. If the condenser will besubjected to freezing temperatures, drain the water andrefill it with an antifreeze solution.

3. Drain the cooling tower or evaporativecondenser, if used; flush the sump and paint any rustedor corroded areas.

4. Open the system master disconnect switch andpadlock it in the OPEN position.

Seasonal Start-up

The steps to follow for the seasonal start-up are asfollows:

1 Perform all annual maintenance onair-handling system and other related equipment.

the

2 Fill the water sump of the cooling tower orevaporative condenser, if used.

7-19

3. Open the shutoff valves of the water-cooled

condenser.

4. Make certain the liquid line solenoid valve(s) is

on automatic control.

5. Open the liquid line shutoff valve.

6. Back-seat the compressor suction and discharge

valves.

7. Close the system master electrical disconnect

switch.

8. Start the system.

9. After the system has operated for 15 to 20

minutes, check the compressor oil level sight glass, oil

pressure, and the liquid line sight glass. If satisfactory,

readjust the system temperature controller to the proper

temperature setting.

SAFETY WARNINGS

Most units used for comfort air conditioningoperate using R-12 or R-22 refrigerants that are nottoxic except when decomposed by a flame. If theliquefied refrigerant contacts the eyes, the personsuffering the injury must be taken to a doctor at once.

Should the skin come in contact with the liquefiedrefrigerant, the skin is to be treated as though it hadbeen frostbitten or frozen. Refer to NAVEDTRA13119, Standard First Aid for Treatment of Frostbite.

Do not adjust, clean, lubricate, or service any partsof equipment that are in motion. Ensure that movingparts, such as pulleys, belts, or flywheels, are fullyenclosed with proper guards attached.

Before making repairs, open all electric switchescontrolling the equipment. Tag and lock the switchesto prevent short circuits or accidental starting ofequipment. When moisture and brine are on the floor,fatal grounding through the body is possible whenexposed electrical connections can be reached ortouched by personnel. De-energize electrical linesbefore repairing them, and ground all electrical tools.

Q9. What are the two types of self-containedair-conditioning units?

Q 1 0 . W h o n o r m a l l y o p e r a t e s a w i n d o wair-conditioning unit?

Q11. Floor units are often referred to as what type ofunit?

Q12.

Q13.

Q14.

Q15.

Q16.

Q17.

Q18.

Q19.

Q20.

What type of unit cools and heats by reversing its

cycle?

The reversing valve changes the direction of hotgas from what component to what other

component in the system?

Heat pumps operating below 45°F develop what

problem on the outside coils?

When the capacity of a heat pump matches the

heat loss, it has reached what point?

What are the two most common evaporators

used for water chiller systems?

Dry-expansion evaporators are controlled by

what type of expansion valve?

Why is a tube-within-a-tube condenser popular?

Condensers can be cleaned in what two ways?

Refrigerant coils should be cleaned at least how

often?

MAJOR SYSTEM COMPONENTS ANDCONTROLS

Learning Objectives: Recognize and understanddifferent types of cooling towers, compressors, andcontrols. Understand basic maintenance requirementsfor cooling towers.

In this section, cooling towers and compressorswhich are the two major components of anair-conditioning system are discussed. In addition, themajor control elements of an air-conditioned systemare also covered.

COOLING TOWERS

Cooling towers are classified according to themethod of moving air through the tower as naturaldraft, induced draft, or forced draft (figs. 7-19 and7-20).

Natural Draft

The natural draft cooling tower is designed to coolwater by means of air moving through the tower at thelow velocities prevalent in open spaces during thesummer. Natural draft towers are constructed ofcypress or redwood and have numerous wooden decksof splash bars installed at regular intervals from thebottom to the top. Warm water from the condenser is

7-20

Figure 7-19.—A package tower with a remote, variable speed pump.

Figure 7-20.—Paralleled package towers.

7-21

flooded or sprayed over the distributing deck and flowsby gravity to the water-collecting basin.

A completely open space is required for the naturaldraft tower since its performance depends on existingair currents. Ordinarily, a roof is an excellent location.Louvers must be placed on all sides of a natural drafttower to reduce drift loss.

Important design considerations are the windvelocity and the height of the tower. A wind velocity of3-miles per hour is generally used for a design ofnatural draft cooling towers. The natural draft coolingtower was once the standard design for coolingcondenser water in refrigeration systems up to about75 tons. It is now rarely selected unless low initial costand minimum power requirements are primaryconsiderations. The drift loss and space requirementsare much greater than for other cooling tower designs.

Induced Draft

An induced draft cooling tower is provided with atop-mounted fan that induces atmospheric air to flowup through the tower, as warm water falls downward.An induced draft tower may have only spray nozzlesfor water backup, or it may be filled with various slatand deck arrangements. There are several types ofinduced draft cooling towers.

In a counterflow induced draft tower (fig. 7-21, C),a top-mounted fan induces air to enter through thebottom of the tower and to flow vertically upward asthe water cascades down through the tower. Thecounterflow tower is particularly well adapted to arestricted space as the discharge air is directedvertically upward, and if equipped with a inlet on each

side, requires only minimum clearance for air intakearea. The primary breakup of water may be either bypressure spray or by gravity from pressure-filledflumes.

A parallel-flow induced draft tower (fig. 7-21, A)operates the same way as a counter-flow tower, exceptthe top-mounted fan pulls the air in through the top ofthe tower and pushes it out the bottom. The airflowgoes in the same direction as the water.

Comparing counterflow and parallel-flow induceddraft towers of equal capacity, the parallel-flow toweris somewhat wider but the height is much less. Coolingtowers must be braced against the wind. From astructural standpoint, therefore, it is much easier todesign a parallel-flow than a counterflow tower, as thelow silhouette of the parallel-flow type offers muchless resistance to the force of the winds.

Mechanical equipment for counterflow andparallel-flow towers is mounted on top of the tower andis readily accessible for inspection and maintenance.The water-distributing systems are completely openon top of the tower and can be inspected duringoperation. This makes it possible to adjust the floatvalves and clean stopped-up nozzles while the towersare operating.

The cross-flow induced draft tower (fig. 7-21, B) isa modified version of the parallel-flow induced drafttower. The fan in a cross-flow cooling tower draws airthrough a single horizontal opening at one end anddischarges the air at the opposite end.

The cooling tower is a packaged tower that isinexpensive to manufacture and is extremely popularfor small installations. As a packaged cooling tower

Figure 7-21.—Types of induced fan cooling towers.

7-22

with piping and wiring in place, it is simple to installand may be placed wherever there is a clearance of 2feet for the intake end and a space of 10 feet or more infront of the fan. The discharge end must not face theprevailing wind and should not be directed into atraffic area because drift loss may be objectionable.

In some situations, an indoor location for thecooling tower may be desirable. An induced drafttower of the counterflow or cross-flow design isgenerally selected for indoor installation. Twoconnections to the outside are usually required—onefor drawing outdoor air into the tower and the other fordischarging it back to the outside. A centrifugal bloweris often necessary for this application to overcome thestatic pressure of the ductwork. Many options arepossible as to the point of air entrance and airdischarge. This flexibility is often important indesigning an indoor installation. Primary waterbreakup is by pressure spray and fill of various types.

The induced draft cooling tower for indoorinstallation is a completely assembled packaged unitbut is so designed that it can be partially disassembledto permit passage through limited entrances. Indoorinstallations of cooling towers are becoming morepopular. External space restrictions, architecturalcompatibility, convenience for observation andmaintenance all combine to favor an indoor location.The installation cost is somewhat higher than anoutdoor location. Packaged towers are available incapacities to serve the cooling requirements ofrefrigeration plants in the 5- to 75-ton range.

Forced Draft

A forced draft cooling tower uses a fan to force airinto the tower. In the usual installation, the fan shaft isin a horizontal plane. The air is forced horizontallythrough the fill and upward to be discharged out of thetop of the tower.

Underflow cooling towers are an improved designof the forced draft tower that retains all the advantagesof the efficient parallel-flow design. Air is forced intothe center of the tower at the bottom. The air is thenturned horizontally (both right and left) through fillchambers and is discharged vertically at both ends. Byforcing the air to flow upward and outward through thefill and leave at the ends, operating noise is baffled anda desirable reduction of sound level is achieved. Allsides of the underflow tower are smoothly encasedwith no louver openings. This blends with modernarchitecture and eliminates the necessity of masonry

walls or other screening devices oftentimes necessaryto conceal cooling towers of other types.

Materials

Redwood has been the standard constructionmaterial for cooling towers for many years. Thoughcypress, as well as treated fir and pine, has been usedoccasionally, these materials have not enjoyed a wideapplication. Casings are constructed of laminatedwaterproof plywood. Such casings, as well as othernoncorrosive materials at critical points, are essentialin areas having a highly corrosive atmosphere. Nails,bolts, and nuts of copper or aluminum are almoststandard practice for cooling tower construction.

Cooling towers of metal coated with plastic orbituminous materials that have air intake louvers andfill made of redwood have met with only limitedsuccess. The limited success is primarily because ofthe high maintenance cost as compared to woodtowers.

Packaged towers with metal sides and wood fill arereasonably common. Some manufacturers have usedsheet aluminum for siding for limited periods of time.Plastic slats have been used for fill material but havenot proved satisfactory in all cases.

Fire ordinances of a large city may require that nowood be used in construction of cooling towers. Withsteel or some other fireproof casing and without fill, acooling tower will comply with the most restrictiveordinances.

Maintenance

Recently, cooling towers have been linked to thes p r e a d o f L e g i o n n a i r e ' s d i s e a s e . S e v e r a lprecautionary measures are recommended to helpeliminate this problem. These include placing ofcooling towers downwind and use of chloridecompounds as disinfectants on a monthly maintenanceschedule.

Water treatment is an important part of theoperation of a cooling tower. The evaporation of waterfrom a cooling tower leaves some solids behind.Recirculation of the water in the condenser coolingtower circuit, and the accompanying evaporation,causes the concentration of solids to increase. Thisconcentration must be controlled or scale andcorrosion will result.

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Though draining the system from time to time andrefilling with fresh water is one method of control, it isnot recommended. Soon after refilling, the dissolvedsolids again build up to a dangerous concentration. Amore common practice is to waste a certain amount ofwater continually from the system to the sewer. Thewater wasted is called blowdown. Blowdown issometimes accomplished by wasting sump waterthrough an overflow. A better practice, however, is tobleed the required quantity of blowdown from thewarm water leaving the condenser on its way to thecooling tower. A mineral salt buildup (calciumbicarbonate concentration) of 10 grains per gallon isconsidered the maximum allowable concentration foruntreated water in the sump if serious corrosion andscaling difficulties are to be avoided.

Cooling towers evaporate about 2 gallons of waterevery hour for each ton of refrigeration. A gallon ofwater weighs 8.3 pounds, and about 1,000 Btu isneeded to evaporate 1 pound of water. Thus, toevaporate a gallon of water, 8.3 x 1,000 or 8,300 Btu isrequired.

In many instances, the makeup water containsdissolved salts in excess of 10 grains per gallon. It isobvious, then, that even 100 percent blowdown willnot maintain a sump concentration of 10 grains. If theblowdown alone cannot maintain satisfactory control,then chemicals should be used.

Makeup water for a cooling tower is the sum ofdrift loss, evaporation, and blowdown. The drift lossfor mechanical draft towers ranges from 0.1 percent ofthe total water being cooled for the better designedtowers to as much as 0.3 percent. In estimatingmakeup water for a cooling tower, the higher value of0.3 percent for drift loss is suggested. If the drift loss isactually less than this, the excess makeup watersupplied is merely wasted down the overflow. Thisdoes, in effect, increase the amount of blowdown and isfavorable from the viewpoint that the concentration ofscale-forming compounds in the tower sump will besomewhat lower.

Redwood is a highly durable material; however, itis not immune to deteriorat ion. The type ofdeteriorat ion varies with the nature of theenvironmental conditions to which the wood isexposed. The principal types of deterioration areleaching, delignification, and microbiological attack.

Algae and slime are present in water and must becontrolled chemically or the rate of heat transfer in thecondenser will be materially reduced. Condenser

tubing, cooling tower piping, and metal surfaces in thewater-circulating system must be protected from scaleand corrosion.

Using too much of a chemical or using the wrongchemical is known as overtreatment. It can materiallyreduce the performance or the life of a cooling towercondenser circuit.

COMPRESSORS

A compressor is the machine used to withdraw theheat-laden refrigerant vapor from the evaporator,compress it from the evaporator pressure to thecondensing pressure, and push it to the condenser. Acompressor is merely a simple pump that compressesthe refrigerant gas. Compressors may be divided intothe following three types—reciprocating, rotary, andcentrifugal. The function of compressing a refrigerantis the same in all three general types, but themechanical means differ considerably. Rotarycompressors are used in small sizes only, and their useis limited almost exclusively to domestic refrigeratorsand small water coolers. Centrifugal compressors areused in large refrigerating and air-conditioningsystems (fig. 7-22).

Reciprocating Compressors

Reciprocating compressors are usually poweredby electric motors, although gasoline, diesel, andturbine drivers are sometimes used. In terms ofcapacity, reciprocating compressors are made infractional horsepower for small, self-contained airconditioners and refrigeration equipment, increasingin size to about 250 tons or more capacity in largerinstallations. Reciprocating compressors are furnishedin open, semisealed, and sealed (hermetic) types.

OPEN.—An open type of compressor shaft isdriven by an external motor. The shaft passes throughthe crankcase housing and is equipped with a shaft sealto prevent refrigerant and oil from leaking or moistureand air from entering the compressor. Pistons areactuated by crankshafts or eccentric drive mechanismsmounted on the shaft. Discharge valves are usuallymounted in a plate over the pistons. Suction valves areusually mounted either in the pistons, if suction vaporsenter the cylinder through the side of the cylinder orthrough the crankcase, or in the valve plate over thepistons, if suction vapors enter the cylinder through thehead and valve plate.

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1. Centrifugal compressor with 3. Control center.5-inch impeller. 4. Chiller section.

2. Refrigerant colled motor. 5. Condenser section.

Figure 7-22.—High-speed (36,000 rpm) single-stage centrifugal chiller.

pins. Hermetically sealed compressor units used in

Figure 7-23 shows a cross section of a typical opentype of eccentric shaft compressor with suction valvesin the valve plate of the head. Most belt-driven opentype of compressors under 3 horsepower use a splashfeed lubrication, but in larger size compressors, forcedfeed systems having positive displacement oil pumpsare more common. The oil pump is usually drivenfrom the rear end of the main shaft. Oil from thecrankcase is forced under pressure through a hole inthe main shaft to the seal, main bearing, and rodbearing, and through a hole in the rod up to the piston

window air conditioners are quite common incommercial sizes (under 5 horsepower) and are evenmade by some manufacturers in large tonnage sizes.

SEMISEALED. —Semisealed compressors aresometimes made in small sizes, but large tonnage unitsare always of the semisealed type. The primary

difference between a fully sealed and a semisealedmotor compressor is that in semisealed types the valveplates, and in some units the oil pump, can be removedfor repair or replacement. This type of construction ishelpful in larger sizes that are so bulky they wouldcause considerable trouble and expense in shipping,removing, and replacing the unit as a whole. Figure7-24 shows a small semisealed compressor.

Sealed or semisealed units eliminate the belt driveand crankshaft seal, both of which are among the chiefcauses of service calls. Sealed and semisealedcompressors are made either vertical or horizontal.The vertical type (fig. 7-25) usually has a positivedisplacement oil pump that forces oil under pressure of10 to 30 psi to the main bearings, rod, or eccentric andpins, although they are sometimes splash oiled.

Although oil pumps for forced feed lubrication arealso used on horizontal hermetic compressors, oil

7-25

Figure 7-23.—Cross section of an open type of reciprocating compressor.

Figure 7-24.—Small semisealed compressor.

circulation at low oil pressure may be provided byslingers, screw type of devices, and the like. Splash andother types of oil feed must hot be considered inferiorforced feed. With good design, they lubricate well. Itis most important to maintain the proper oil level, use acorrect grade of oil, and keep the system clean and freeof dirt and moisture. This is true for all compressionrefrigeration systems, especially those equipped with Figure 7-25.—Vertical semisealed compressor.

7-26

Figure 7-26.—Reciprocating hermetic compressor. (A) Motor rotor; (B) Motor stator; (C) Compressor cylinder; (D) Compressor piston;(E) Connecting rod; (F) crankshaft; (G) Crank throw; (H) Compressor shell (I) Glass sealed electrical connection.

hermetically sealed units whose motor windingsmay be attacked by acids or other corrosivesubstances introduced into the system or formed bythe chemical reaction of moisture, air, or otherforeign substances.

HERMETIC. —The term sealed or hermetic unitmerely means that the motor rotor and compressorcrankshaft of the refrigeration system are made in onepiece, and the entire motor and compressor assembly isput into a gastight housing that is welded shut (fig.7-26). This method of assembly eliminates the need forcertain parts found in the open unit. These parts are asfollows: motor pulley, belt, compressor flywheel, andcompressor seal. The elimination of the precedingparts in the sealed unit similarly does away with thefollowing service operations: replacing motor pulleys,replacing flywheels, replacing belts, aligning belts,and repairing or replacing seals. When it is realizedthere are major and minor operations that maintenancepersonnel must perform and the sealed unit dispenses

with only five of these, it can be readily seen that

servicing is still necessary.

Rotary Compressors

Rotary compressors are generally associated withrefrigerators, water coolers, and similar small capacityequipment. However, they are available in largersizes. A typical application of a large compressor isfound in compound compressor systems where highcapacity must be provided with a minimum of floor

space.

In a rotary compressor (fig. 7-27), an eccentricrotor revolves within a housing in which the suctionand discharge passages are separated by means of asealing blade. When the rotating eccentric first passesthis blade, the suction area is at a minimum. Furtherrotation enlarges the space and draws in the charge ofrefrigerant. As the eccentric again passes the blade, thegas charge is shut off at the inlet, compressed, anddischarged from the compressor. There are variations

7-27

Figure 7-27.—Rotary compressor: A. Part identification; B. Operation.

7-28

of this basic design, some of which provide the rotor

with blades to trap and compress the vapor.

Centrifugal Compressors

Centrifugal compressors are used in largerefrigeration and air-conditioning systems, handlinglarge volumes of refrigerants at low-pressuredifferentials. Their operating principles are based onthe use of centrifugal force as a means of compressingand discharging the vaporized refrigerant. Figure 7-28is a cutaway view of one type of centrifugalcompressor. In this applicat ion, one or twocompression stages are used, and the condenser andevaporator are integral parts of the unit. The heart of

this type of compressor is the impeller wheel.

Scroll Compressors

A scroll compressor has two different offset spiraldisks to compress the refrigerant vapor. The upperscroll is stationary, while the lower scroll is the drivenscroll. Intake of refrigerant is at the outer edge of the

driven scroll, and the discharge of the refrigerant is atthe center of the stationary scroll. The driven scroll isrotated around the stationary or "fixed" scroll in anorbiting motion. During this movement, the refrigerantvapor is trapped between the two scrolls. As the drivenscroll rotates, it compresses the refrigerant vaporthrough the discharge port. Scroll compressors havefew moving parts and have a very smooth and quiet

operation.

CONTROLS

Controls used in air conditioning are generally thesame as for refrigeration systems—thermostats,humidistats, pressure and flow controllers, and motoroverload protectors (fig. 7-29).

Thermostats

The thermostat is an adjustable temperature-sensitive device, which through the opening andclosing of its contacts controls the operation of the

Figure 7-28.—Cutaway view of one type of centrifugal compressor.

7-29

1. Commpressor breakers. 4. High-pressure controls.

2. Compressor starters. 5. Oil failure controls.3. Fan cycle controls. 6. Solid-state staging thermostat.

Figure 7-29.—Packaged air-cooled chiller controls.

cooling unit. The temperature-sensitive element maybe a bimetallic strip or a confined, vaporized liquid.

The thermostats used with refrigerative airconditioners are similar to those used with heatingequipment, except their action is reversed. Theoperating circuit is closed when the room temperaturerises to the thermostat control point and remains closeduntil the cooling unit decreases the temperatureenough. Also, cooling thermostats are not equippedwith heat-anticipating coils.

Wall type of thermostats most common for heatingand air conditioning in the home and on somecommercial units use a bimetallic strip and a set ofcontacts, as shown in figure 7-30. This type ofthermostat operates on the principle that when twodissimilar metals, such as brass and steel, are bondedtogether, one tends to expand faster than the other doeswhen heat is applied. This causes the strip to bend andclose the controls.

Figure 7-30.—Bimetallic thermostat.

As a Utilitiesman, you may be required to make anadjustment that sets the temperature difference between thecut-in and cutout temperatures. For example, if the system isset to cut in at 76°F and cut out at 84°F, then the differentialis 8°F. This condition prevents the unit from cyclingcontinually as it would if there were no differential.

Humidistats

A room "humidistat" may be defined as ahumidity-sensitive device controlling the equipmentthat maintains a predetermined humidity of the spacewhere it is installed. The contact of the humidistat isopened and closed by the expansion or contraction ofnatural blonde hairs from human beings, which is oneof the major elements of this control. It has been foundthat these types of hairs are most sensitive to themoisture content of the air surrounding them.

Pressure-Flow Controllers

Pressure-flow controllers are discussed in chapter 6. Thepurpose of these controllers in air conditioning is to act assafety switches for the system, so if either the head pressure istoo high or suction pressure too low, the system will besecured regardless of the position of the operating switches.

Refrigerant-Flow Controllers

The refrigerant-flow controllers used with airconditioners are also similar to the ones discussed inchapter 6. These controllers are either of the capillarytype or externally equalized expansion valve type and

7-30

are usually of larger tonnage than those used forrefrigerators.

Motor Overload Protectors

When the compressor is powered by an electricmotor, either belt driven or as an integral part of thecompressor assembly, the motor is usually protectedby a heat-actuated overload device. This is in additionto the line power fuses. The heat to actuate theoverload device is supplied by the electrical energy tothe motor, as well as the heat generated by the motor

Figure 7-31.—Thermal overload relay.

itself. Either source of heat or a combination of thetwo, if too much, causes the overload device to openand remove the motor from the line.

Figure 7-31 shows a thermal-element type ofoverload cutout relay. It is housed in the magneticstarter box. On current overload, the relay contactsopen, allowing the holding coil to release the startingmechanism, thereby stopping the motor.

An oil failure cutout switch is provided on manysystems to protect the compressor against oil failure.The switch is connected to register pressuredifferential between the oil pump and the suction line.Figure 7-32 shows a typical oil failure cutout switch.The switch contains two bellows, which work againsteach other, and springs for adjusting. Tubing from theoil pump is connected to the bottom bellows of theswitch. Tubing from the suction line is connected tothe upper bellows. When a predetermined pressuredifferential is not maintained, a pair of contacts in theswitch is opened and breaks the circuit to thecompressor motor. A heating element with a built-indelay is in the switch to provide for starting thecompressor when oil pressure is low.

The water-regulating valve used with a water-cooled condenser responds to a predeterminedcondensing pressure. A connection from the dischargeside of the compressor to the valve transmitscondensing pressure directly to a bellows inside the

Figure 7-32.—Oil failure cutout switch.

7-31

valve. High pressure opens the valve, allowing agreater flow of water; low pressure throttles the flow.Use of such a valve provides for a more economical useof water for condensing. Figure 7-33 shows a typicalwater-regulating valve. When condenser water issupplied by a cooling tower, water-regulating valvesare not customarily used because the cooling tower fan

Figure 7-33.—Water-regulating valve.

and circulating pump are wired into the compressormotor control circuit.

Step Controller

The step controller contains a shaft upon which ismounted a series of cams. Rotation of the cams, inturn, operates electrical switches. Through adjustmentof the cams on the shaft, the temperature at which eachswitch is to close and open (differential) is established.In addition, the switches may be adjusted to operate inalmost any sequence (fig. 7-34).

TROUBLESHOOTING

Table Z of appendix II is a troubleshooting chartgenerally applicable to all types of air conditioners.Most manufacturers include more detailed and specificinformation in publications pertaining to their units. Ifyou find that there is no manual with the unit when it isunpacked, write to the manufacturer and request one assoon as possible.

Q21. How are cooling towers classified?

Q22. A wind velocity of 8 mph is generally used todesign natural draft cooling towers. True /False

Q23. Counter flow, parallel flow, and cross flow aretypes of what class of cooling tower?

Figure 7-34.—Step controller and pressure-sensor configuration. (A) Step controller with modulating motor, single-poledouble-throw mini switches, and mouse trap relay assembly; (B) Pressure sensor that controls the step controller.

7-32

Q24.

Q25.

Q26.

Q27.

Q28.

Q29.

Q30.

Q31.

Q32.

What type of cooling tower is installed indoors?

Forced draft underflow towers retain the

advantages of what other type of cooling tower?

Air intake louvers and fill are made of what

material?

Cooling towers evaporate approximately how

much water every hour for each ton of

refrigeration?

Rotary compressors are used in what type of

units?

Semisealed and sealed compressors have

reduced service requirements because of the

elimination of what part?

What control is temperature sensitive and

controls the operation of the cooling unit?

What dev ice main ta ins humid i t y a t a

predetermined point?

What causes a motor to shut down when a motor

is too hot?

AUTOMOTIVE AIR CONDITIONING

Learning Objective: Understand the basic principlesof operation, maintenance, and repair of automotive airconditioning.

Veh ic l e a i r cond i t ion ing i s t he coo l ing(refrigeration) of air within a passenger compartment.Refrigeration is accomplished by making practical useof three laws of nature—heat transfer, latent heat ofvaporization, and the effects of pressure on boiling orcondensation. The first two laws are discussed inchapter 6 of this TRAMAN; the practical applicationof the third is outlined below.

EFFECT OF PRESSURE ON BOILING ORCONDENSATION

The saturation temperature (the temperaturewhere boiling or condensation occurs) of a liquid orvapor increases or decreases according to the pressureexerted on it.

In the fixed orifice tube refrigerant system, liquidrefrigerant is stored in the condenser under highpressure (fig. 7-35). When the liquid refrigerant isreleased into the evaporator by the fixed orifice tube,

Figure 7-35.—Air-conditioning refrigeration system-fixed orifice.

7-33

the resulting decrease in pressure and partial boilinglowers its temperature to its new boiling point. As therefrigerant flows through the evaporator, passengercompartment air passes over the outside surface of theevaporator coils. As it boils, the refrigerant absorbsheat from the air and thus cools the passengercompartment. The heat from the passengercompartment is absorbed by the boiling refrigerant andhidden in the vapor. The refrigeration cycle is nowunder way. The following functions must be done tocomplete the refrigeration cycle:

1. Disposing of the heat in the vapor

2. Converting the vapor back to liquid for reuse

3. Returning of the liquid to the starting point in therefrigeration cycle

The compressor and condenser (fig. 7-35) performthese functions. The compressor pumps the refrigerantvapor (containing the hidden heat) out of theevaporator and suction accumulator drier, then forcesit under high pressure into the condenser which islocated in the outside air stream at the front of thevehicle. The increased pressure in the condenser raisesthe refrigerant condensation or saturation temperatureto a point higher than that of the outside air. As the heattransfers from the hot vapor to the cooler air, therefrigerant condenses back to a liquid. The liquidunder high pressure now returns through the liquid lineto the fixed orifice tube for reuse.

It may seem difficult to understand how heat canbe transferred from a comparatively cooler vehiclepassenger compartment to the hot outside air. Theanswer lies in the difference between the refrigerantpressure that exists in the evaporator and the pressurethat exists in the condenser. In the evaporator, thecompressor suction reduces the pressure and theboiling point below the temperature of the passengercompartment. Thus heat transfers from the passengercompartment to the boiling refrigerant. In thecondenser, the compressor raises the condensationpoint above the temperature of the outside air. Thusthe heat transfers from the condensing refrigerant tothe outside air. The fixed orifice tube and thecompressor simply create pressure conditions thatpermit the laws of nature to function.

AUTOMOTIVE COMPRESSORS

There are three basic types of air-conditioningcompressors in general use in automotive applications.Each of these uses a reciprocating (back-and-forthmot ion) p i s ton a r rangement—two-cy l inde r

reciprocating, swash plate, and scotch yoke. Mostautomotive compressors are semihermetic.

Two-cylinder compressors (fig. 7-36) usuallycontain two pistons in a parallel V-type configuration.The pistons are attached to a connecting rod, which isdriven by the crankshaft. The crankshaft is connectedto the compressor clutch assembly, which is driven byan engine belt. Reed valves generally are used tocontrol the intake and exhaust of the refrigerant gasduring the pumping operation. These compressors areusually constructed of die cast aluminum.

In the swash plate or "wobble plate" compressor(fig. 7-37), the piston motion is parallel to the

Figure 7-36.—Two-cylinder reciprocating compressor.

Figure 7-37.—Five-cylinder swash plate compressor.

7-34

crankshaft. The pistons are connected to an angledswash plate using ball joints. Swash plate compressorsare of three types—five-cylinder, six-cylinder, andfive-cylinder variable.

The five- and six-cylinder swash compressorhas, in effect, three cylinders at each end of itsinner assembly. A swash plate of diagonal designis mounted on the compressor shaft. It actuates thepistons, forcing them to move back and forth in thecylinders as the shaft is rotated. Reed valvescontrol suction and discharge; crossover passagesfeed refrigerant to both high- and low-servicefittings at the rear end of the compressor. A geartype of oil pump in the rear head provides forcompressor lubrication.

The five-cylinder variable swash plate compressoris different from the other swash plate compressors. Ituses a plate connected to a hinge pin that permits theswash plate to change its angle. The angle of the swashplate is controlled by a bellows valve that sensessuction pressure. During high load conditions theswash plate angle is large, and during low loadcondit ions, the swash plate is smaller . Thedisplacement of the compressor is high at a large angleand low at a small angle.

A scotch-yoke compressor changes rotary motioninto reciprocating motion. The basic mechanism of thescotch yoke contains four pistons mounted 90 degreesfrom each other. Opposed pistons are pressed into ayoke that rides on a slide block located on the shafteccentric (fig. 7-38). Rotation of the shaft provides areciprocating motion with no connecting rods.Refrigerant flows into the crankcase through the rearand is drained through the reeds attached to the pistontops during the suction stroke. Refrigerant is thendischarged through the valve plate out the connectorblock at the rear. These compressors are shorter inlength and larger in diameter than other compressors.

Compressor Service Valves

Compressor service valves are built into somesystems. They serve as a point of attachment for testgauges or servicing hoses. The service valves havethree position controls—front seated, back seated, andmidposition (fig. 7-39).

The position of this double-faced valve iscontrolled by rotating the valve stem with a servicevalve wrench. Clockwise rotation seats the front faceof the valve and shuts off all refrigerant flow in thesystem. This position isolates the compressor from therest of the system.

Figure 7-39.—Three-way service valve positions.

Figure 7-38.—Four-cylinder scotch-yoke mechanism.

7-35

Counterclockwise rotation unseats the valve andopens the system to refrigerant flow (midposition).Systematic checks are performed with a manifoldgauge set with the service valve in midposition.Further counterclockwise rotation of the valve stemseats the rear face of the valve. This position opens thesystem to the flow of refrigerant but shuts offrefrigerant to the test connector. The service valves areused for observing of operating pressures; isolating thecompressor for repair or replacement; and discharging,evacuating, and charging the system.

Compressors used in automotive air-conditionings y s t e m s g e n e r a l l y a r e e q u i p p e d w i t h a nelectromagnetic clutch that energizes and de-energizesto engage and disengage the compressor. Two types ofclutches are in general use-the rotating coil and thestationary coil.

The rotating coil clutch has a magnetic coilmounted in the pulley that rotates with the pulley. Itoperates electrically through connections to astationary brush assembly and rotating slip rings. Theclutch permits the compressor to engage or disengageas required for adequate air conditioning. Thestationary coil clutch has the magnetic coil mounted onthe end of the compressor. Electrical connections aremade directly to the coil leads.

The belt-driven pulley is always in rotation whilethe engine is running. The compressor is in rotationand operation only when the clutch engages it to thepulley.

Air-conditioning and refrigeration systems usevarious control devices, including those for therefrigerant, the capillary tube usually found onwindow units, the automatic expansion valves alsofound on window units and small package units, thethermal expansion valve, and various types of suctionpressure-regulating valves and devices. A briefdescription of a suction pressure-regulating valve isgiven below. A suction pressure-regulating valve isused on automotive air conditioning because thevarying rpm of the compressor unit must maintain aconstant pressure in the evaporator.

Suction Pressure-Regulating Valves

Suction pressure-regulating valves may beinstalled in the suction line at the outlet of theevaporator when a minimum temperature must bemaintained. Suction pressure-regulating valvesdecrease the temperature difference, which wouldotherwise exist between the compartment temperature

and the surface of the cooling coils. The amount ofheat that can be transferred into the evaporatingrefrigerant is directly proportional to the temperaturedifference. Figure 7-40 shows an exploded view of atypical suction pressure-regulating valve, sometimescalled a suction throttling valve in automotive airconditioners.

Three types of suction pressure-regulating valvesare used—suction throttling valve (STV), evaporatorpressure regulators (EPR), or pilot-operated absolutevalve (POA), developed by General MotorsCorporation. These valves, in most cases, areadjustable.

The POA valve uses a sealed pressure element thatmaintains a constant pressure independent of thealtitude of the vehicle. There are two basic types ofmetering devices built into a single container—theVIR (Valves-In-Receiver) and the EEVIR (EvaporatorEqualized Valves-In-Receiver). These units combinethe POA valve, receiver-drier, thermostatic expansionvalve, and sight glass into a single unit.

The VIR assembly is mounted next to theevaporator, which eliminates the need for an externalequalizer line between the thermostatic expansionvalve and the outlet of the POA valve. The equalizerfunction is carried out by a drilled hole (equalizer port)between the two-valve cavities in the VIR housing.

The thermostatic expansion valve is alsoeliminated. The diaphragm of the VIR expansion valveis exposed to the refrigerant vapor entering the VIRunit from the outlet of the evaporator. The sight glassis in the valve housing at the inlet end of thethermostatic valve cavity where it gives a liquidindication of the refrigerant level.

Figure 7-40.—A typical suction pressure-regulating valve.

7-36

The VIR thermostatic expansion valve controls theflow of refrigerant to the evaporator by sensing thetemperature and pressure of the refrigerant gas, as itpasses through the VIR unit on its way to thecompressor. The POA valve controls the flow ofrefrigerant from the evaporator to maintain a constantevaporator pressure of 30 psi. The VIR and the POAvalves are capsule type of valves. When found to bedefective, you must replace the complete valvecapsule.

The drier desiccant is in a bag in the receiver shell.It is replaceable by removing the shell and removingthe old bag and installing a new bag of desiccant.

Service procedures for the VIR system differ insome respect from the service procedures performedon conventional automotive air-conditioning systems.

SERVICE PRECAUTIONS

Observe the following precautions whenever youare tasked to service air-conditioning equipment:

A system that has been opened to replace acomponent or one which has discharged throughleakage must be evacuated before charging.

Never open or loosen a connection beforedischarging the system.

Immediately after disconnecting a componentfrom the system, seal the open fittings with a capor plug.

Before disconnecting a component from thesystem, clean the outside of the fittingsthoroughly.

Do not remove the sealing caps from areplacement component until you are ready toinstall it.

Refrigerant oil absorbs moisture from theatmosphere if it is left uncapped. Do not open anoil container until it is ready to use, and installthe cap immediately after using. Store the oilonly in a clean, moisture-free container.

Before connecting to an open fitting, alwaysinstall a new seal ring. Coat the fitting and sealwith the refrigerant oil before connecting.

When installing a refrigerant line, avoid sharpbends. Position the line away from the exhaustor any sharp edges that may chafe the line.

Tighten the fittings only to specified torque. Thecopper and aluminum fittings that are used in

refrigerant systems will not tolerate over-tightening.

When disconnecting a fitting, use a wrench onboth halves of the fitting to prevent twisting ofrefrigerant lines or tubes.

Do not open a refrigerant system or uncap areplacement component unless it is as close aspossible to room temperature. This preventscondensation from forming inside a componentthat is cooler than the surrounding air.

Keep the service tools and work area clean.Contamination of a refrigerant system throughcareless work habits must be avoided.

DIAGNOSIS, TESTING, AND SERVICING

Diagnosis is more than just following a series ofinterrelated steps to find the solution to a specificcondition. It is a way of looking at systems that are notfunctioning the way they should and finding out why.Also, it is knowing how the system should work andwhether i t is working correctly. All gooddiagnosticians use the same basic procedures.

There are basic rules for diagnosis. If these rulesare followed, the cause of the condition will usually befound the first time through the system.

1. Know the system; know how the parts gotogether. Also, know how the system operates and itslimits, and what happens when something goes wrong.Sometimes this means comparing a system that isworking properly with the one you are servicing.

2. Know the history of the system. How old or newis the system? What kind oftreatment has it had? Has itbeen serviced in the past in such a manner that mightrelate to the present condition? What is the servicehistory? A clue in any of these areas might save a lot ofdiagnosis time.

3. Know the probability of certain conditionsdeveloping. It is true that most conditions are caused bysimple things, rather than by complex ones, and theyoccur in a fairly predictable pattern. Electrical problemconditions, for instance, usually occur at connections,rather than in components. An engine "no-start" ismore likely to be caused by a loose wire or somecomponent out of adjustment than a sheared offcamshaft. Know the difference between impossible andimprobable. Many good technicians have spent hoursdiagnosing a system because they thought certainfailures were "impossible," only to find out the failures

7-37

eventually were just "improbable" and actually hadhappened. Remember, new parts are just that—new. Itdoes not mean they are good functioning parts.

4. Don’t cure the symptom and leave the cause.Recharging a refrigerant system may correct thecondition of insufficient cooling, but it does not correctthe original problem unless a cause is found. A properlyworking system does not lose refrigerant over time.

5. Be sure the cause is found; do not be fooled intothinking the cause of the problem has been found.Perform the proper tests; then double-check the results.The system should have been checked for refrigerantleaks. If no leaks were found, perform a leak test withthe system under extremely high pressure. If the systemperformed properly when new, it had to have a leak to below in charge.

6. No matter what form charts may take, they aresimply a way of expressing the relationship between thebasic logic and a physical system of components. It is away of determining the cause of a condition in theshortest possible amount of time. Diagnosis chartscombine many areas of diagnosis into one visual displaythat allows you to determine the following:

The probability of certain things occurring in asystem

The speed of checking certain components, orfunctions, before others

The simplicity of performing certain tests beforeothers

The elimination of checking huge sections of asystem by performing simple tests

The certainties of narrowing down the search toa small area before performing in-depth testing

The fastest way to find a condition is to work withthe tools that are available, which means working withproven diagnosis charts and the proper special tools forthe system being worked on.

S e r v i c i n g p r o c e d u r e s f o r a u t o m o t i v eair-conditioning units are similar to those used toservice conventional air-conditioning systems.Discharging, evacuating, charging procedures,connections, and positions of valves on the gaugemanifold set are shown in figure 7-41.

Servicing procedures for the VIR system are alsosimilar to those used when servicing conventionalair-conditioning systems. However, the hookup of themanifold gauge set is to the VIR unit. The

high-pressure fitting is located in the VIR inlet line.The low-pressure fitting is located in the VIR unit.

SYSTEM VISUAL INSPECTION

It is often possible to detect a problem caused by acareful visual inspection of the air-conditioningrefrigerant system. This includes broken belts,obstructed condenser air passages, a loose clutch,loose or broken mounting brackets, disconnected orbroken wires, and refrigerant leaks.

A refrigerant leak usually appears as an oilyresidue at the leakage point in the system. The oilyresidue soon picks up dust or dirt particles from thesurrounding air and appears greasy. Through time, thisbuilds up and appears to be heavy, dirt-impregnatedgrease.

Most common leaks are caused by damaged ormissing O-ring seals at various hose and componentconnections. When these O rings are replaced, the newO rings should be lubricated with refrigerant oil. Careshould be taken to keep lint from shop towels or clothsfrom contaminating the internal surfaces of theconnection. Leakage may occur at a spring lockcoupling if the wrong O rings are used at the coupling.

Another type of leak may appear at the internalSchrader type of air-conditioning charging valve corein the service gauge port valve fittings. If tighteningthe valve core does not stop the leak, it should bereplaced with a new air-conditioning charging valvecore.

Missing service gauge port valve caps can alsocause a refrigerant leak. If this important primary seal(the valve cap) is missing, dirt enters the area of theair-conditioning charging valve core. When theservice hose is attached, the valve depressor in the endof the service hose forces the dirt into the valve seatarea, and it destroys the sealing surface of theair-conditioning charging valve core. When a servicegauge port valve cap is missing, the protected area ofthe air-conditioning charging valve core should becleaned and a new service gauge port valve cap shouldbe installed.

CAUTION

The service gauge port valve cap must beinstalled finger tight. If tightened withpliers, the sealing surface of the servicegauge port valve may be damaged.

7-38

Figure 7-41.—Procedures for observing operating pressures, charging, purging, and evacuating a unit.

CLEANING A BADLY CONTAMINATED The system may have been operated for a timeREFRIGERANT SYSTEM with water or moisture in it.

A refrigerant system can become badly contami-nated for a number of reasons.

A badly contaminated system contains water,carbon, and other decomposition products. When such

The compressor may have been run for sometime with a severe leak or an opening in thesystem.

The compressor may have failed due to damagea condition exists, the system must be flushed with a

or wear.special flushing agent, using equipment designedespecially for this purpose. Follow the suggestionsand procedures outlined for proper cleaning.

Flushing Agents

The system may have been damaged by acollision and left open for some time.

The system may not have been cleaned properlyafter a previous failure.

A refrigerant to be suitable as a flushing agentmust remain in the liquid state during the flushingoperation to wash the inside surfaces of the systemcomponents. Refrigerant vapor will not remove

7-39

contaminant particles. They must be flushed with aliquid. Some refrigerants are better suited for thispurpose than others.

R-11 and R-113 are suited for use with specialf lushing equipment. Both have rather highvaporization points—74.7°F for R-11 and 117.6°F forR-l 13. Both refrigerants also have low closedcontainer pressures. This reduces the danger of anaccidental system discharge to a ruptured hose orfitting. R-113 will do the best job and is recommendedas a flushing refrigerant. Both R-11 and R-113 requirea propellant or a pump type of flushing equipment dueto their low closed container pressures. R-11 isavailable in pressurized containers. Although notrecommended for regular use, it may becomenecessary to use R-11 if special flushing equipment isnot available. It is more toxic than other refrigerants,and it should be handled with extra care. Currently newrefrigerants are being developed to replace R-11 andR-113 because these refrigerants will be phased out bythe year 2000.

CAUTION

Use extreme care and adhere to all safetyprecautions related to the use ofrefrigerants when flushing a system.

System Cleaning and Flushing

When it is necessary to flush a refrigerant system,the suction accumulator/drier must be removed andreplaced, as it is impossible to clean. Remove the fixedorifice tube. If a new tube is available, replace thecontaminated one; otherwise, wash it carefully influshing refrigerant or mineral spirits and blow it dry.If it does not show signs of damage or deterioration, itmay be reused. Install new O rings.

Any moisture in the evaporator will be removedduring leak testing and system evacuation followingthe cleaning job. Perform each step of the cleaningprocedure carefully as outlined below.

1. Check the hose connections at the flushingcylinder outlet and flushing nozzle to ensure they aresecure.

2. Ensure the flushing cylinder is filled withapproximately 1 pint of R-113 and that the valveassembly on top of the cylinder is tightened securely.

3. Connect a can of R-12 or R-134a to theSchrader valve at the top of the charging cylinder. A

refrigerant hose and a special, safety type of refrigerantdispensing valve are required for connecting the smallcan to the cylinder. Ensure all connections are secure.

5. Remove and discard the suction accumulator/drier. Install a new accumulator/drier and connect it tothe evaporator. Do not connect it to the suction linefrom the compressor. Ensure a protective cap is in placeon the suction line connection.

4. Connect a gauge manifold and a dischargesystem. Disconnect the gauge manifold.

6. Replace the fixed orifice tube. Install aprotective cap on the evaporator inlet tube as soon as thenew orifice tube is in place. The liquid line will beconnected later.

7. Remove the compressor from the vehicle forcleaning and servicing or replacement, whichever isrequired. If the compressor is cleaned and serviced, addthe specified amount of refrigerant oil before installingit on the mounting brackets in the vehicle. Install theshipping caps on the compressor connections. Install anew compressor on the mounting brackets in thevehicle.

8. Back flush the condenser and the liquid line asfollows:

a. Remove two O rings from the condenserinlet tube spring lock coupling.

b. Remove the discharge hose from thecondenser and clamp a piece of (1/2-inch ID) heaterhose to the condenser inlet line. Ensure the hose is longenough to insert the free end into a suitable wastecontainer to catch the flushing refrigerant.

c. Move the flushing equipment into positionand open the valve on the can of R-12 or R-134a (fullycounterclockwise).

d. Back flush the condenser and the liquid lineby introducing flushing refrigerant into the supportedend of the liquid line with the flushing nozzle. Hold thenozzle firmly against the open end of the liquid line.

e. After the liquid line and condenser havebeen flushed, lay the charging cylinder on its side soR-12 or R-134a will not force more of the flushingrefrigerant into the liquid line. Press the nozzle firmly tothe liquid line and admit the R-12 or R-134a to force allof the flushing refrigerant from the liquid line andcondenser.

f. Remove the 1/2-inch hose and clamp fromthe condenser inlet connection.

7-40

g. Stand the flushing cylinder upright and flushthe compressor discharge hose. Secure it so the flushingrefrigerant goes into the waste container.

h. Close the dispensing valve of the R-12 orR-134a can (fully clockwise). If there is any flushingrefrigerant in the cylinder, it may be left there until thenext flushing job. Put the flushing kit and R-12 or

R-134a can in a suitable storage location.

i. Install the new lubricated O rings on thespring lock coupling male fittings on both the condenserinlet and the liquid lines. Assemble the couplings.

9. Connect all refrigerant lines. All connectionsshould be cleaned and new O rings should be used.Lubricate new O rings with clean refrigerant oil.

10. Connect a charging station or manifold gaugeset and charge the system with 1 pound of R-12 orR-134a. (Do not evacuate the system until after it hasbeen leak tested.)

11. Leak test all connections and components with aflame type of leak detector or an electronic leakdetector. If no leaks are found, go to Step 12. If leaksare found, service as necessary; check the system andthen go to Step 12.

12. Evacuate and charge the system with a specifiedamount of R-12 or R-134a. Operate the system toensure it is cooling properly.

SAFETY PRECAUTIONS

The use of safety when handling or usingrefrigerants can never be stressed enough. Asdiscussed in chapter 6 of this TRAMAN, routinelythink of safety for yourself and coworkers.

Extreme care must be taken to prevent any liquidrefrigerant from coming in contact with the skin andespecially the eyes. A bottle of sterile mineral oil and aquantity of weak boric acid solution must always bekept nearby when servicing the air-conditioningsystem. Should any liquid refrigerant get into youreyes, immediately use a few drops of mineral oil towash them out; then wash the eyes clean with the weakboric acid solution. Seek a doctor’s aid immediatelyeven though irritation may have ceased. Always wearsafety goggles when servicing any part of therefrigerant system.

To avoid a dangerous explosion, never weld,solder, steam clean, bake body finishes, or use anyexcessive amount of heat on or in the immediate area of

any part of the refrigerant system or refrigerant supplytank, while they are closed to the atmosphere whetherfilled with refrigerant or not.

The liquid refrigerant evaporates so rapidly thatthe resulting refrigerant gas displaces the airsurrounding the area where the refrigerant is released.To prevent possible suffocation in enclosed areas,always discharge the refrigerant into recycling/reclaiming equipment. Always maintain goodventilation surrounding the work area.

Although R-12 gas, under normal conditions, isnonpoisonous, the discharge of refrigerant gas near anopen flame can produce a very poisonous gas. This gasalso attacks all bright metal surfaces. This poisonousgas is generated when the flame type of leak detector isused. Avoid inhaling the fumes from the leak detector.Ensure that R-12 is both stored and installed accordingto all federal, state and local ordinances.

When admitting R-12 or R-134a gas into thecooling unit, always keep the tank in an uprightposition. lf the tank is on its side or upside down, liquidR-12 or R-134 enters the system and may damage thecompressor.

TRUCK AND BUS AIR CONDITIONING

The cabs of many truck-tractors and long distanceh a u l i n g t r u c k s a n d e a r t h m o v e r c a b s a r eair-conditioned. Most of this equipment is of the "hangon" type and is installed after the cab has been made.

Some truck air-conditioning units have twoevaporators—one for the cab and one for the reliefdriver's quarters in back of the driver. Some systemsuse a remote condenser, mounted on the roof of thecab. This type of installation removes the condenserfrom in front of the radiator, so the radiator can operateat full efficiency. This is especially important duringlong pulls in low gear.

The system is similar to the automobile airconditioner and is installed and serviced in the samegeneral way.

The air conditioning of buses has progressedrapidly. Because of the large size of the unit, most busair-conditioning systems use a separate gasolineengine with an automatic starting device to drive thecompressor. The system is standard in constructionexcept for the condensing unit. It is made as compactas possible and generally is installed in the bus, so itcan be easily reached for servicing.

7-41

Condensing units are often mounted on rails withflexible suction and liquid lines to permit sliding thecondensing unit out of the bus body to aid in servicing.

Air-cooled condensers are used. Thermostaticexpansion valve refrigerant controls are standard.Finned blower evaporators are also used.

The duct system usually runs between a falseceiling and the roof of the bus. The ducts, usually oneon each side of the bus, have grilles at the passengerseats. The passengers may control the grille by openingand closing.

CERTIFICATION

The Environmental Protection Agency (EPA) hasestablished as per the Clean Air Act (CAA) that alltechnicians who maintain or repair air-conditioning orrefrigeration equipment or technicians who operaterecycling, reclaiming, and recovery equipment mustbe certified. Certification is administered byorganizations with certification programs that areapproved by the EPA. It is important to understand,that as a Utilitiesman, if you are not certified, youcannot do any HVAC/R service that requires use orremoval of refrigerants. Certification requirements aredivided into two different areas—automotiveair-conditioning and HVAC/R.

Automotive Air-Conditioning Certification

Automotive air conditioning is serviced orr e p a i r e d m o r e o f t e n t h a n o t h e r t y p e s o fair-condit ioning systems. In today's world,automotive air-conditioning systems are heavily usedas our society spends more and more time in theirvehicles. Industry experts say that 25 percent of theR-12 purchased in the United States is used inautomotive air conditioning. The fittings and hosesused in automotive air conditioning allow leakage tooccur. Automotive air-conditioning service facilitiesor technicians are now changing (retrofitting) systemsin vehicles to use refrigerant R-134a and removingCFC R-12 to meet new standards. From the EPA’sstandpoint, technicians must be meet the followingrequirements to be certified:

Be aware that venting refrigerant is illegal.

Understand why all the regulations are beingcreated. Understand what is happening to theenvironment.

Have a working knowledge of SAE standardsJ-1989, J-1990, and J-1991.

Perform service in a safe manner withoutinjuring personnel or damaging equipment.Areas that must be understood include venting,handling, transporting, and disposing ofrefrigerant.

Once these requirements are met through testing ofthe individual applicant, a certification card is issued.

Heating, Ventilating, Air Conditioning, andRefrigeration Certification

Certification requirements to service standardtypes of air-conditioning systems are the same as forautomotive air-conditioning certification. Unlike theautomotive cert if icat ion program, standardair-conditioning certification is divided into levelscorresponding to the type of service the technicianperforms. There are four types of certification:

Type I – Servicing small appliances

Type II – Servicing high or very high-pressureappliances

Type I I I – Se rv ic ing o r d i spos ing o flow-pressure appliances

Type IV (Universal) – Servicing all types ofequipment

Individuals will be required to take a proctored,closed book test. These tests are offered byorganizations approved by the EPA for the specifictype of certification that the individual technicianr e q u i r e s . T e c h n i c i a n s c a n o n l y w o r k o nair-conditioning systems that they have been certifiedfor service.

Q33.

Q34.

Q35.

Q36.

Q37.

Q38.

The saturation temperature increases ordecreases depending upon what factor?

What are the three basic types of automotivecompressors?

A scotch-yoke compressor changes rotarymotion into what type of motion?

Refrigerant can be put into a system when theservice valve is back-seated. True /False

The POA valve, receiver-drier, expansion valve,and sight glass are combined in what type ofdevice?

Service procedures for VIR systems are differentthan conventional automotive air-conditioningsystems. True/False

7-42

Q39.

Q40.

Q41.

Q42.

Q43.

Q44.

Q45.

What is the most important thing you shouldknow before you perform a diagnosis on a systemproblem?

A refrigerant leak appears in what way at thepoint of the leak?

What is the most common cause of leaks onautomotive air-conditioning systems?

For a refrigerant to be a suitable flushing agent,it must remain in what state during flushingoperations?

Which part of an automotive air-conditioningsystem is replaced because it is impossible to

clean?

A type IV certification is also known as what typeof certification?

Who approves organizations to certifytechnicians?

DUCTWORK

Learning Objective: Understand the basic typesof ductwork systems and the components of thosesystems for distribution of conditioned air.

Distributed air must be clean, provide the properamount of ventilation, and absorb enough heat to coolthe conditioned spaces. To deliver air to theconditioned space, air carriers are required, which arecalled ducts. Ducts work on the principle of airpressure difference. If a pressure difference exists, airwill flow from an area of high pressure to an area of lowpressure. The larger this difference, the faster the airwill flow to the low-pressure area.

CLASSIFICATION OF DUCTS

There are three common classifications ofducts—conditioned air ducts, recirculating-air ducts,and fresh-air ducts. Conditioned air ducts carryconditioned air from the air conditioner and distributeit to the conditioned area. Recirculating air ducts takeair from the conditioned space and distribute it backinto the air conditioner system. Fresh air ducts bringfresh air into the air-conditioning system from outsidethe conditioned space.

Ducts commonly used for carrying air are of around, square, or rectangular shape. The most efficient

duct is a round duct, based on the volume of air handledper perimeter distance. In other words, less material isneeded for the same capacity as a square or rectangular

duct.

Square or rectangular duct fits better to buildingconstruction. It fits above ceilings and into walls and is

much easier to install between joists and studs.

TYPES OF DUCT SYSTEMS

There are several types of supply duct systems (fig.7-42) that deliver air to room(s) and then return the airfrom the room(s) to the cooling (evaporator) system.

These supply systems can be grouped into four types:

1. Individual round pipe system

2. Extended plenum system

3. Reducing trunk system

4. Combination (of two or more systems)

Return air systems are normally of threetypes—single return, multiple return (fig. 7-42), or

combination of the two systems.

CONSTRUCTION

Ducts may be made of metal, wood, ceramic, andplastic. Most commonly used is sheet steel coated withzinc (galvanized steel). Sheet metal brakes andforming machines are used in fabricating ducts.Elbows and other connections, such as branches, aredesigned using geometric principles. Some types ofduct connections used in constructing duct systems are

shown in figure 7-43.

Sheet metal ducts expand and contract as they heatand cool. Fabric joints are often used to absorb thismovement. Fabric joints should also be used where theduct connects to the air conditioner. Many ducts areinsulated to lower noise and reduce heat transfer. Theinsulation can be on the inside or the outside of theduct. Adhesives or metal clips are commonly used tofasten the insulation to the duct. As we are only brieflydiscussing construction here, you can find construc-tion and fabrication methods in the Steelworker,volume 2. It details design and fabrication of steel

ductwork.

7-43

Figure 7-42.—Supply duct systems: A. Individual round pipe; B. Extended plenum; C. Reducing trunk; D. Multiple return air

system.

COMPONENTS

Figure 7-43.—Typical duct connections: A. Elbow; B. Tee: C.Reducing tee; D. Cross: E. Lateral.

To enable a duct system to circulate air at the

proper velocity and volume to the proper conditioned

areas, you can use different components within the

duct system, such as diffusers, grilles, and dampers.

Diffusers, Grilles, and Registers

Room openings to ducts have several devices that

control the airflow and keep large objects out of the

duct. These devices are called diffusers, grilles, and

registers. Diffusers deliver fan-shaped airflow into aroom. Duct air mixes with some room air in certain

types of diffusers.

Grilles control the distance, height, spread of

air-throw, and amount of air. Grilles cause some

resistance to airflow. Grille cross-section pieces block

about 30 percent of the air. Because of this reason and

to reduce noise, cross sections are usually enlarged at

the grille. Grilles have many different designs, such as

fixed vanes which force air in one direction, or

adjustable to force air in different directions.

Registers are used to deliver a concentrated air

stream into a room, and many have one-way or

two-way adjustable air stream deflectors.

7-44

Dampers

One way of getting even air distribution is throughthe use of duct dampers. Dampers balance airflow orcan shut off or open certain ducts for zone control.Some are located in the grille, and some are in the ductitself. There are three types of dampers used inair-conditioning ductwork—butterfly, multiple blade,and split damper (fig. 7-44). When installing a damper,always draw a line on temperature control.

Fire Dampers

Automatic fire dampers should be installed in allvertical ducts. Ducts, especially vertical ducts, willcarry fumes and flames from fires. Fire dampers mustbe inspected and tested at least once a year to be surethey are in proper working order. There are two typesof f ire dampers, which are fai l-safe units—spring-loaded to close and weight-loaded to close. Firedampers are usually held open by a fusible link. Heat

will melt the link and the damper will close by eithergravity, weights, or springs (fig. 7-45).

Fans

Air movement is usually produced by some type offorced airflow. Fans are normally located in the inlet ofthe air conditioner. Air is moved by creating either apositive pressure or negative pressure in the ductwork.The two most popular types of fans are the axial flow(propeller) or radial flow (squirrel cage) (fig. 7-46).

Figure 7-45.—Fire damper in OPEN position.

Figure 7-44.—Three types of duct dampers.

Figure 7-46.—Principal types of fans: A. Radial flow; B. Axial

flow.

7-45

The axial-flow fan is usually direct-driven bymounting the fan blades on the motor shaft. Theradial-flow fan is normally belt-driven but can also bedirect-driven.

BALANCING THE SYSTEM

Balancing a system basically means sizing theducts and adjusting the dampers to ensure each roomreceives the correct amount of air. To balance asystem, follow these steps:

1. Inspect the complete system; locate all ducts,openings, and dampers.

2. Open all dampers in the ducts and at the grilles.

3. Check the velocities at each outlet.

4. Measure the "free" grille area.

5. Calculate the volume at each outlet. Velocity xArea = Volume

6. Area in square inches divided by 144 multipliedby feet per minute equals cubic feet/minute.

7. Total the cubic feet/minute.

8. Determine the floor areas of each room. Add todetermine total area.

9. Determine the cfm for each room. The area ofthe room divided by the total floor area multiplied by thetotal cfm equals cfm for the room.

10. Adjust duct dampers and grille dampers toobtain these values.

11. Recheck all outlet grilles.

In some cases, it may be necessary to overcomeexcess duct resistance by installing an air duct booster.These are fans used to increase airflow when a duct istoo small, too long, or has too many elbows.

Q46.

Q47.

Q48.

Q49.

Q50.

What are the three common types of ducts?

What are the three types of return air systems?

Sheet metal ducts expand and contract as theyheat and cool. True /False

What are the three types of dampers?

Once you have checked the velocities at eachoutlet, what is the next step when balancing the

duct system?

7-46

APPENDIX I

GLOSSARY

ABSOLUTE ZERO —The point where all molecularmotion ceases, -460°F.

AC — Alternating current.

AEROBIC DECOMPOSITION — Bacte r ia ldecomposition that occurs in the presence of oxygen.

AFTERCOOLER — Device which cools the finaldischarge from a compressor.

ANGLE VALVE — A stop valve that is actually acombination valve and elbow since its outlet branchis at right angles to its inlet branch.

ASME — American Society of Mechanical Engineers.

BILL OF MATERIAL — A list of all materials requiredto complete an installation based on takeoffs andestimates.

BOILER — An enclosed vessel that converts water tosteam of proper temperature and pressure for anintended purpose.

BOILER SETTING — The structure that encloses aboiler and forms a furnace.

BREECHING — Connects a boiler to the stack.

BUSHING — A plumbing fitting used to reduce the pipefrom one size to another size.

BUTTERFLY VALVE — A two-position valve with avertical or horizontal disk.

CAP — A plumbing fitting used to close off a length of

pipe.

CATHODIC PROTECTION — The use of materialand liquid to cause electricity to flow to avoidcorrosion.

CBMU — Construction Battalion Maintenance Unit.

CBR — Chemical, Biological, and Radiological.

CBU — Construction Battalion Unit.

CEC — Civil Engineer Corps.

CENTRIFUGAL FORCE — The force that impels asubstance to move outward from the center ofrotation.

CENTIGRADE — A thermometric scale in which 0degrees represents the freezing point and 100degrees represents the boiling point of water at apressure of 1 atmosphere. Generally used with metricunits of measure. Equal to the internationalthermometric scale of Celsius.

CHECK VALVE — An automatic non-return valve or avalve which permits a fluid to pass in one directionbut automatically closes if the fluid begins to pass inthe opposite direction.

CLARIFICATION OF WATER — The removal ofsuspended materials to produce a clear, clean liquid.

COLIFORM — The coliform groups of organisms are abacterial indicator of contamination. This group hasas one of its primary habitats, the intestinal tract ofhuman beings. Coliforms also may be found in theintestinal tract of warm-blooded animals and inplants, soil, air, and the aquatic environment.

COMSECONDNCB — Commander, Second NavalConstruction Brigade.

COMTHIRDNCB — Commander, Third NavalConstruction Brigade.

COMPRESSOR — Pump of a refrigerating mechanismwhich draws a low pressure on the cooling side of therefrigerant cycle and squeezes or compresses the gasinto the high pressure or condensing side of the cycle.

CONDENSATION — The process of changing a vaporto a liquid.

CONDENSER — Component in a refrigeration systemthat removes and dissipates heat from a compressedrefrigerant.

CONDUCTION — The transmitting of heat from onesubstance or part to another substance or part that arein direct contact with each other.

CONVECTION — The transfer of heat by means of amedium, such as water, air, and steam.

COUPLING — A plumbing fitting used to join twolengths of pipe in a straight run.

DEGREE OF TEMPERATURE — Measurement ofheat intensity.

AI-1

DEHYDRATOR — Device used to remove moisture JOINING — All the procedures used to connect pipesfrom a refrigerant system. together.

DEW POINT — Temperature at which vapor (at 100percent humidity) begins to condense and deposit asa liquid.

DIATOMACEOUS EARTH — A porous mineralpowder, used as a filtering medium for the removal ofsuspended materials.

ELBOW — A plumbing fitting used to change thedirection of a length of pipe at 90° and 45° angles.

EVAPORATOR — Component of a refrigerationsystem that permits the absorption of heat from adesired medium or space.

EVAPORATION — A process of converting a liquid,by heat, into a vapor or gas.

FILTER-DRIER — Device for removing small foreignparticles and moisture from refrigerant fluid.

FITTINGS — Devices which when placed in a pipesystem make branch connections or changes in adirection of a line.

GATE VALVE — A sluice with two inclined seatsbetween which the valve wedges down in closing.The passage through the valve is in an uninterruptedline, and when the valve is opened, the sluice isdrawn up into a dome or recess, leaving anunobstructed passage the full diameter of the pipe.

GLOBE VALVE — A valve with a round, ball-like shellthat is used for regulating or controlling the flow ofgases or steam.

GPD — Gallons per day.

GPH — Gallons per hour.

GPM — Gallons per minute.

HEAT — The energy that is measured in British thermalunits.

HERMETICALLY SEALED — Caused to be airtight.

HUMIDITY — The amount of water vapor in a givenvolume of air.

HYDROLOGIC CYCLE — Process by which water iscirculated from ocean to atmosphere to earth’ssurface.

ID — Inside diameter.

INFLUENT — Water flow into a sewage or watertreatment plant or equipment.

LATENT HEAT — Amount of heat required to changethe state of a substance without a measurable change

in temperature.

MATERIAL TAKEOFF — The estimate of materials

required for a job based on plans and specifications.

METERING DEVICE — Valve or device used to

regulate amount and state of refrigerant as it passes

through the system.

NAVFAC — Naval Facilities Engineering Command.

NCR — Naval Construction Regiment.

NCTC — Naval Construction Training Center.

NMCB — Naval Mobile Construction Battalion.

OD — Outside diameter.

PACKING — Materials used to seal moving machineryjoints against leakage.

P H — A value used to measure the acidity or alkalinity(basic) of a substance. A pH scale is from 0 to 14,

with 7.0 as neutral. Below 7.0 on the scale is acid, and

above 7.0 on the scale is alkaline or basic. Used in

water treatment and purification.

PLUG — A plumbing fitting used to close off a fitting or

a length of pipe by screwing into the fitting or pipe.

PPM — Parts per million.

PSI — Pounds per square inch.

PSIG — Pounds per square inch gauge.

PUMP — A mechanical device which applies a force tomove any substance that flows or can be made toflow.

RADIATION — The transfer of heat through space by

heat waves.

RECEIVER — Device in a refrigeration system to storerefrigerant used by the system.

REDUCING VALVE — A spring-loaded or

lever-loaded valve similar to a safety valve, designed

to maintain a lower end constant pressure beyond the

valve.

RELATIVE HUMIDITY — The percentage of water

vapor in the air when compared to the amount it doeshold as to the amount it could hold.

AI-2

REVERSE OSMOSIS — A process whereby a solutionflows through a semipermeable membrane into anarea of lower solute concentration.

CARBON DIOXIDE — CO2, a liquid, is used to lowerpH of softened and settled potable water.

ROICC — Resident Officer- in-Charge of Construction.

ROUGHING IN — The installation of all parts of aplumbing system; completed before installation offixtures.

SENSIBLE HEAT — Heat that can be measured indegrees of temperature with a thermometer.

SPECIFIC HEAT — The quantity of heat expressed inBtu required to raise 1 pound of any substance 1°F intemperature.

SUPERHEAT — The amount of heat expressed in Btuadded to a substance above its boiling temperature.

TOTAL HEAT — Sensible heat plus latent heatexpressed in Btu.

CHLORINE — C12, a natural chemical element (Cl). Apowerful disinfectant, used extensively in watertreatment. As a gas, it’s color is greenish yellow, andit is 2 1/2 times heavier than air. As a liquid, it’s coloris amber, and it is about 1 1/2 times heavier thanwater. It is an oxidizer, and is toxic to all organismsand corrosive (in the presence of water) to mostmetals.

DIAMINETETRACETATE — (EDTA), Reagent, usedin solution with Sodium Ethylene to detect mineralswhich cause hardness in water.

FERRIC CHLORIDE — FeC13, a dark salt that hydratesto a yellow-orange form. A coagulant, used toflocculate dissolved solids in a strong acid waterenvironment.

TRAMAN — Training manual.

VALVE — A device for regulating, stopping, or startingflow in a system and for controlling direction of flow.

VACUUM — Pressure lower than atmospheric pressure.

VAPORAZATION — The process of changing a liquidto a vapor.

VELOCIMETER — Instrument that measures airspeeds using a direct-reading air speed indicatingscales.

FERRIC SULFATE — FeS3, a coagulant, used toflocculate dissolved solids in a strong acid waterenvironment.

FERROUS SULFATE — FeSO4, a coagulant, used toflocculate dissolved solids in a strong base(alkaline), water environment.

HYDRATED LIME — (Caustic Lime) CaOH2, a drywhite powder, a strong base (alkaline), consists ofcalcium hydroxide made by treating caustic limewith water. Used to balance water pH and absorbchlorine.

GLOSSARY OF METHYL ORANGE — Reagent, used in solution todetermine the alkalinity of water.

CHEMICALS USED IN WATERTREATMENT

METHYL PURPLE — Reagent, used in solution todetermine the alkalinity of water

ALUMINUM HYDROXIDE — AIOH, Reagent, used todecolorize water samples when preforming chloridetests on water.

PHENOLPHTHALEIN — C20H 14O4, Reagent, used asan pH indicator for water testing. Red color in bases(alkalines) or decolorized in an acid.

ALUMINUM SULFATE — (Alum), A13(SO4)3, a whitesalt, a coagulant, used to flocculate dissolved solidsin a weak acid water environment.

POTASSIUM CHROMATE — KC1, Reagent, used intesting for chlorine levels in water.

AMMONIA — NH3, an alkaline colorless gas, used insolution to detect leaks in chlorine equipment andsystems.

POTASSIUM HYDROXIDE-(Caustic Potash)K2CrO7, a white powder, strongly basic (alkaline),when dissolved in water produces heat. Used tobalance water pH and absorb chlorine. Also used as areagent to test water salinity.

BARIUM CHLORIDE — BaC12, Reagent, used to test SILVER NITRATE — AgNO3, Reagent, used tofor sulfates in water. determine amount of salinity and chloride in water.

CALCIUM HYPOCHLORITE — CaC12O2, a granularwhite powder used to disinfect water.

SODIUM CARBONATE — (Soda ash), Na2CO3, salt ofcarbonic acid, strongly basic (alkaline). Used in

AI-3

water soften ing, and balancing water pH to aidcoagulation.

SODIUM ETHYLENE — (EDTA), Na2CH3CH2,Reagent, used in solution with Diaminetetracetate,detect minerals which cause hardness in water.

to

SODIUM HYDROXIDE — (Caustic Soda) NaOH, astrong base (alkaline), white powder used to balancepH in water to aid coagulation, and absorb chlorine.

SODIUM HYPOCHLORITE — NaOC1, a saltusually furnished in solution, used for disinfectionof water.

SULFURIC ACID — (Standard), H2SO4, strongacid, used to balance water pH and aid in coa-gulation.

THIOSULFATE — A salt, used to neutralize chlorinewater. Used to sterilize water sample containers.

AI-4

APPENDIX II

TABLES FOR MAINTENANCE PROCEDURES

Table A.—Permissible Enlargement and Ellipticity of Holes in Tube Sheets

Table B.—Preoperation Checks for Boilers

Table C.—Additional Preoperating Checks for Gas-Fired Boilers

Table D.—Additional Preoperating Checks for Oil-Fired Boilers

Table E.—Operational Checks for Boilers

Table F.—Boiler Emergencies

Table G.—Fuel Gases

Table H.—A Comparison of Fuel Oils

Table I.—Troubleshooting Chart for Pot and Sleeve Oil Burners

Table J.—Troubleshooting Chart for Gas-Fired Space Heaters

Table K.—Oil Burner Troubleshooting

Table L.—Common Operation Difficulties for Oil Burners

Table M.—Oil Pump Troubleshooting

Table N.—Troubleshooting Chart for Thermostats

Table O.—Troubleshooting Hot-Water System Boilers

Table P.—Inspection and Maintenance of Coppers and other Steam-Heated Equipment

Table Q.—Troubleshooting for Dishwashing Machines

Table R.—Troubleshooting Chart for Ovens, Ranges, & Boilers

Table S.—Troubleshooting Chart for Clayton Steam Generator

Table T.—Troubleshooting Chart for Residential Washers

Table U.—Troubleshooting Chart for Residential Dryers

Table V.—Troubleshooting Refrigeration Systems

Table W.—Troubleshooting Industrial Refrigeration

Table X.—Troubleshooting Laundry Equipment

Table Y.—Troubleshooting Checklist Domestic Refrigerators and Freezers

Table Z.—Troubleshooting Chart for Air Conditioners

AII-1

Table A

Permissible Enlargement and Ellipticity of Holes in Tube Sheets

Outside diameter of tube Maximum tube hole diameter(inches) (Inches)

Maximum ellipticity(inches)

1 1 1/16 1/32

1 1/4 1 5/16 1/32

1 1/2 1 37/64 3/64

1 3/4 1 53/64 3/64

2 2 3/32 1/16

2 1/4 2 11/32 1/16

2 1/2 2 5/8 5/64

3 3 1/8 5/64

3 1/4 3 13/32 3/32

3 1/2 3 21/32 3/32

4 4 3/16 1/8

4 1/2 4 11/16 1/8

AII-2

Table B

Preoperating Checks for Boilers

Equipment

Boiler room

Furnace/gas passages

Valves

Piping

Electrical systems

Guards

Water-gauge glass

Check/Action

Remove rags, paint cans, oil spots from deck

Stow tools and equipment

Must be clean and clear and all doors must fit tight

Must be in good repair

No oil/tools in combustion chamber

Must be purged

Good operating condition

Bent stems

Missing/broken handwheels

Inspect piping for leaks

Check for proper support

Oil-soaked or frayed wiring

Damaged or loose conduit

Improperly secured control boxes

Tight and in proper position

Well lighted

Not stained

AII-3

Table C

Additional Preoperating Checks for Gas-fired Boilers

Equipment Checks

Pilot & main gas cock Operate smoothly

Copper tubing No restrictions, such as kinks or flat spots

Air shutters

Burner & main gas valve

Boiler Room

Operate freely

Linkage must not have too much lost motion

Must be firmly supported

No free gas. Ventilate if present and test all piping withsoap solution

Table D

Additional Preoperating Checks for Oil-fired Boilers

Equipment

Strainers Inspect & clean

Checks

BurnersMust be clean

Nozzle must be clean

Inspect and set electrodes

Check all fittings for leaks

Check operation of burner safety switch

Oil system Inspect for leaks, and repair

AII-4

Table E

Operational Checks for Boilers

EQUIPMENT ACTION/CHECK

Water Level

Main steam stop bypass (ifinstalled)

–Check frequently as water expands during the heating up period.

–Open if the boiler is to be cut in on a cold line;

–Main steam stop can be opened when there is no other boiler on thesame steam line.

Air cock

Steam pressure

–Close after steam has formed and has blown all air from boiler.

–Raise slowly, usually 1/2 to 2 1/2 hours, depending upon type, sizeand condition of boiler.

Safety valve

–Temperature of water should be raised at a rate of 100°F per hour.

– Manually lifts when pressure is at least 75% of the valve setting

–Make sure valves reseat properly; if valves fail to reseat, lift them asecond time.

Boiler feedwater –Commence feeding boiler, it probably will be automaticallycontrolled.

Firing –Gas; Maintain ignition; maintain air-fuel ratio; there should be nosoot formation.

Water level

–Oil; Maintain ignition, observe flame and adjust dampers; checkaccuracy by flue-gas analysis.

–Blow down gauge glass and water column (observe promptness ofreturn of water in glass).

–Keep at proper level.

Boiler blowdown

Cutting in boiler

–Frequently, determine true level of water with different methods.

–Watch and monitor gauge glass.

–Frequency depends on water tests.

–If closed, open main steam stop valve slowly.

AII-5

Table F

Boiler Emergencies

EMERGENCY TASK KEY POINTS

EMERGENCY ONE: Low Secure the boiler, secure electrical DO NOT ADD WATER TO THEwater condition indicated by switches, steam stop, and feedwater BOILER to raise the water level in theno water level in the gauge stop. Prove water level by opening try gauge glass column. STAY AWAYglass. cocks. Cool the boiler slowly until the from the discharge. DON’T FORCE

water temperature is 200°F. Secure all COOL.sources of draft. Check controls. Findout the cause for low water level.Correct the trouble. After correctionhas been made, add water to obtain thecorrect water level.

EMERGENCY TWO: High Prove water level by opening the try STAY AWAY from discharge. Checkwater condition indicated by cocks. Blowdown the boiler by blowdown pit. Watch the gauge glassgauge glass full of water. opening the blowdown valves. Find until normal level is reached. If control

out the cause of high water condition. operates properly, continue to operateCheck feedwater pump controls. the boiler.Correct the trouble. Secure the boiler ifpump controls operate improperly.

EMERGENCY THREE: Secure the boiler by securing the For large boilers: Water should be fedSerious tube failure making it electrical steam and fired systems. to the boiler until properly cooled.impossible to maintain water Add water to the boiler until the Mark the gauge glass if within itslevel. ruptured tube level is reached and the range. Observe level by whatever

boiler is cooled to a temperature of means available.200°F. Open the boiler to replace thetube.

EMERGENCY F O U R : Secure the boiler. Find the cause of Ensure that a slug of water did notF la reback caused by an flareback and correct the trouble. interrupt flame with a refire beforeexplosion within the combus- Check for sufficient fuel and type of prepurge.tion chamber. fuel contamination. Check the burner.

EMERGENCY FIVE: Secure the boiler if it is possible to If unable to secure boiler because ofMinor tube failure indicated by remove it from the line for sufficient steaming requirements and you cantrouble maintaining water time to make necessary repairs. Secure maintain the water level, continue tolevel under normal steam electrical switches. Open the steam operate. If unable to maintain the waterdemand. stop and feed stop if additional water is level and/or supply, secure the boiler.

not needed to protect remaining tubes.

Securetop and bottomvalves. Replace Boiler may be kept on l ine, i fEMERGENCY SIX: Broken gauge glass Use chains or whatever necessary. Check the boiler watergauge glass on water column. method available to prevent injury to level by using the try cocks.

personnel.

AII-6

Table G

Fuel Gases

Fuel Source Heating valueMaximum

(Btu per cuft)

Remarks

Natural gas

Manufactured Gas

Gas wells700–1,300average 1,000

Ideal fuel. It is pumped topoint of use

Carbureted Water Gas Manufactured from coal 520–540 A costly good fuel that isenriched with oil vapors part of most city gas

Oil Gas Manufactured from petroleum 520–540 Used on U.S. west coast; isoften mixed with coke oven

gasManufactured from coal, coke,

Producer Gas wood, etc. 135–165 Requires cleaning

Liquefied Petroleum Gas

Propane By-product of gasoline 2,500 Boiling point: -44°F. Lique-fies under slight pressure

Butane By-product of gasoline 3,200–3,260Boiling point 32°F. Lique-fies under slight pressure

AII-7

Table H

A Comparison of Fuel Oils

Grade Number

1

Approximateweight/gallon

6.92

Heating value

(Btu per gallon)

136,000

Type Fuel

A volatile distillate oil for use in burnersthat prepare fuel for burning solely byvaporization.

2 7.08 138,500 A moderately volatile distillate oil for usein burners which prepare fuel for burningby a combination of vaporization andatomization

4 7.58 145,000 A residual oil for burner installations notequipped with preheaters

5 (Light) 7.83 148,500 A residual oil of intermediate viscosityfor use in burners equipped withpreheaters; however, preheating may ormay not be required depending on climateand equipment

5 (Heavy) Greater than 5 light Greater than 5 light A residual oil of greater viscosity than 5light. Preheating may be required beforeburning this oil; and in cold climates,preheating may be required beforehandling as well

6 8.16 152,000 A residual oil of high viscosity for whichpreheating is always required

AII-8

Table I

Troubleshooting Chart for Pot and Sleeve Oil Burners

Problem Probable Cause Possible Remedy

Burner Smokes

Burner goes out

Burner Flooded

Low oil flow

Improper fuel Use recommended fuel

Insufficient oil flow Troubleshoot for low flowExcessive chimney draft Check draft regulatorPilot casing is poorly fitted Remove and install correctlyDirty burner Clean the burner

Low oil supply Add oil if necessaryPlugged vent on the out supply line Clean the ventInsufficient oil flow Troubleshoot for low oil flowImproper fuel Use recommended fuelFuel inlet plugged with carbon CleanDirt in the oil control valve Clean the valveOil valve is not level Level the valveFilter cartridge plugged Clean the filterExcessive chimney draft Check draft regulatorExcessive flue downdraft Install downdraft hood

Dirty float valve Remove and clean the float valveImproper operation Instruct operating personnel on

proper proceduresNeedle valve stuck Clean or replace the valve

Dirty burner Clean the burner

Excessive flue downdraft Install downdraft hood

Air trapped in oil supply line Eliminate high points in the pipingand bleed air out

Oil control valve not level

Oil may be too heavy

Level the valve

Only use manufacturer's recom-mended grade of oil

Dirt in the supply line or in the Clean the line and componentsmetering mechanism

C logged oil strainer Clean the strainer

High fuel consumption

Flue inlet clogged with carbon

Improper fuel

Heat loss

Excessive chimney draft

Heat exchanger caked with slag

Remove the carbon

Use manufacturer's recommendedgrade of oil

Reduce air supply to the burner

Check the draft regulator

Clean the affected areas

AII-9

Table J

Troubleshooting Chart for Gas-fired Space Heaters

Problem Probable Cause Possible Remedy

Motor does not run Incorrect current Check and correct

Faulty wiring Rewire properly

Defective wiring Replace and lubricate

Motor runs intermittently Thermal overload protectors If no external cause, such as improper current,cutting out can be found, replace the motor

Excessive fan and motor Bent fan blade Straighten by hand or replace if seriousnoise Excessive end play in shaft If end play exceeds 1/32 inch, repair or replace

Solenoid valve hums or Installed backwards Check arrow on valve body and correct ifflutters Poor electrical connection or

required

faulty solenoid Check, correct, or replace

Burner does not ignite Faulty pilot burner, thermo- Check, correct, or replacecouple, or thermal bulb

Inoperable solenoid valveImpart current across the leads of the valve. Aclick indicates satisfactory operation. Replacesolenoid if necessary

Delay in main burner Malfunctioning limit switchoperations (2 to 3 min) afterfan starts

Replace limit switch

Improper burning of main Primary air incorrectly setburner

Adjust primary air after the unit has beenburning for 10 to 15 minutes. Adjust the shutterdown until a yellow tip appears on the flame, andthen open the shutter until the yellow tipdisappears.

Incorrect orifice size

Incorrect gas pressure

Check manufacturer's specifications for thecorrect size and replace.

Check manufacturer's specifications regardingcorrect pressure for the gas being used. Measurepressure and adjust pressure regulator to correctcondition.

Pilot fails to light or will not Stopped pilot line Clean line or replace, if requiredstay lit Excessive draft Eliminate draft

Low gas pressure Check pressure regulator or tank level, if LPG

AII-10

Table K

Oil Burner Troubleshooting

Burner fails to start

Source

Thermostat control

Procedure Causes Correction

Check thermostat settings Thermostat is in OFF or Switch to HEATCOOL position

Safety overloads

Thermostat is set too low Turn to higher

Check burner motor, Burner motor overload Push motor overload resetprimary safety control, and tripped buttonauxiliary limit switch

Primary control tripped on Reset safety switch leversafety

Push auxiliary limit switchAuxiliary limit switch reset buttontripped on safety

Power

Thermostat unit

Cad Cell

Check furnace disconnect Switch open Close switchswitch and main discon- Blown fuse or tripped Replace fuse or resetnect switch breaker breaker

Touch jumper wire across Loose thermostat screw Tighten connectionthermostat terminals on connectionsprimary control. If burner Dirty contacts Clean contactsstarts, then fault is in Thermostat not level Level thermostatthermostat circuit Faulty thermostat Replace thermostat

Disconnect flame detector Flame detector leads Separate leadswires at primary control. shortedIf burner starts, fault is in Flame detector exposed to Seal off false source ofthe detector circuit light light

Short circuit in flame Replace detectordetector

AII-11

Table K

Oil Burner Troubleshooting (Continued)

Burner fails to start

Source Procedure Causes Correction

Primary Control Place trouble light between Primary or auxiliary control Check dial adjustment. Set

(1) the black and white leads. switch open to maximum stop settingNo light indicates there is no Jumper terminals; if burnerpower to the control. start switch is faulty, replace

control.

Open c i rcu i t be tween Trace wiring and repair ordisconnect switch and limit replacecontrolLow line voltage or power Call power companyfailure

Primary Control Place trouble light between Defective internal control Replace control

(2) the orange and black leads. circuitNo l ight indicates thecontrol is faulty.

Burner

(1)

Place trouble light between Blown fusethe black and white leads toburner motor. No lightindicates no power to theburner motor.

Replace fuse

Burner

(2)

Place trouble light between Binding burner blower Turn off power and rotatethe black and white leads to wheel blower wheel by hand.b u r n e r m o t o r . L i g h tindicates power to the motor Seized fuel pump If seized, free wheel fromand a burner fault. binding or replace fuel

pump.

Defective burner motorReplace motor

AII-12

Table K

Oil Burner Troubleshooting (Continued)

Burner starts but no flame is established

Source

Oil supply

Procedure Causes Correction

Check tank gauge or use dip stick No oil in tank Fill tankCoat dipstick with litmus paperand insert to bottom of the tank. Water in oil tank Pump or drain the water out ifListen for pump whine greater than 1 inch in depth

Open valveTank shutoff valve closed

Oil filters and oil Listen for pump whine Oil line filter plugged Replace filter cartridgeline Kinks or restriction in oil line Repair or replace oil line

Plugged fuel pump strainer Clean strainer or replace pumpOpen bleed valve or gauge port.Start burner. No oil or milky oil Air leak in oil supply line Locate and correct leak andindicates loss of prime tighten all connections

Oil Pump Install pressure gauge on pump Pump partially or corn- pletely Replace pumpand read pressure. Pressure frozen – No pressure and motorshould not be less than 100 psig locks out on overload

Coupling disengaged or broken – Reengage or replace couplingno pressure.

Nozzle

Fuel pressure too low.

Disconnect ignition leads. Nozzle orifice pluggedObserve oil spray (gun assembly Nozzle strainer pluggedmust be removed form the unit) Poor or off center sprayInspect nozzle for pluggedorifice or carbon buildup aroundorifice

Adjust pressure to 100 psig

Replace nozzle with same size,spray angle, and spray type

Ignition electrodes Remove gun assembly and Fouled or shorted electrodes and Clean electrodes and leadsinspect electrodes and leads. leads; Eroded electrode tips Dress up electrode tips and reset

Improper position of electrode gap to 1/8 inch and correctlytips position the tips

Bad buss bar connection Retension and alignCracked or chipped insulators Replace electrodeCracked or burned lead Replace electrode leadsinsulators

Ignition Trans- Connect ignition leads to Low line voltage Check voltage at power source.former transformer. Start burner and Correct cause of voltage drop or

observe spark. Check line call power company.voltage to transformer primary Burned out transformer windings Replace transformer

No spark or weak sparkProperly ground transformercase

Burner Motor Motor does not come up to speed Low line voltage Check voltage at power source.and trips out on overload. Turn Correct cause of voltage drop oroff power and rotate blower call power companywheel by hand to check for Pump or blower overloading Correct cause of overloading orbinding or excessive drag motor replace motor

Faulty motor Replace motor

AII-13

Table K

Oil Burner Troubleshooting (Continued)

Burner starts and fires but locks out on safety

Source Procedure (1) Procedure (2) Cause Correction

Poor fire After burner fires, If burner continues to Unbalanced fire Replace nozzleimmediately place run, fault may be due Too much air – lean Reduce combustionjumper across flame to poor fire. Inspect short fire air – check combus-detector terminals at fire. tionprimary control Too little fire – long Increase combustion

dirty fire air – check combus-tion

Excessive draft Adjust barometricdamper for correctdraft

Too little draft or C o r r e c t d r a f t o rRestriction remove restriction

Flame detector

Dirty cad cell face Clean cad cell faceFaulty cad cel l – Replacecadcellexceeds 1,500 ohmsLoose or defective Secure connectionscad cell wires Or replace cad cell

If fire is good, fault is holder and wire leadsin flame detector.Check detectorcircuit. P r imary control R e p l a c e p r i m a r y

circuit defective control

Primary control If burner locks out onsafety, fault is inprimary control.

AII-14

Table K

Oil Burner Troubleshooting (Continued)

Burner starts and fires but locks out on safety

Source Procedure (1) Procedure (2) Cause Correction

Poor fire After burner fires, If burner continues to Unbalanced fire Replace nozzleimmediately place run (does not lock Too much air – lean Reduce combustionjumper across flame out on safety), fault short fire air – check combus-detector terminals at may be due to poor tionprimary control fire. Inspect fire. Too little fire – long Increase combustion

dirty fire air – check combus-tion

Excessive draft Adjust barometricdamper for correctdraft

Too little draft or Correct draft orrestriction remove restriction

Flame detector If fire is good, fault Dirty cad cell faceis in flame detector.Check detector Faulty cad cellcircuit. –exceeds 1,500

ohms

Clean cad cell face

Replace cad cell

Loose or defective Secure connectionscad cell wires Or replace cad cell

holder and wire leads

Oil supply(Listen for pumpwhine) If burner looses Air slug or leak in Check supply line

flame (does not lock supply line and oil tankout on safety), faultis in fuel system. Restriction or Remove restriction

plugged strainers or replace pump

AII-15

Table K

Oil Burner Troubleshooting (Continued)

Burner runs continuously (too little heat)

Source Procedure (1) Procedure (1) Cause Correction

Combustion Check burner com- If burner continues to Unbalanced fire Replace nozzlebustion for CO2 stack run (does not lock out Too much air – lean Reduce combustiontemperature and on safety), fault may short fire air – check combus-smoke be due to poor fire tion

Inspect fire. Too little fire – long Increase combustiondirty fire air – check combus-

tionExcessive draft Adjust barometric

damper for correctdraft

Too little draft or C o r r e c t d r a f t o rrestriction remove restriction

Flame detectorIf fire is good, fault is Dirty cad cell face Clean cad cell facein flame detector.Check detector Faulty cad cell – Replacecadcellcircuit. exceeds 1,500 ohms

Loose or defective Secure connectionscad cell wires Or replace cad cell

holder and wire leads

Oil supply( L i s t e n f o rpump whine)

If burner looses flame Air slug or leak in Check supply line and(does not lock out on supply line oil tanksafety), fault is in fuelsystem. Restriction or plugged Remove restriction or

strainers replace pump

AII-16

Table K

Oil Burner Troubleshooting (Continued)

Burner starts and fires but short cycles (too little heat)

Source Procedure Causes Correction

Thermostat

Limit Control

Power

Check thermosta Heat anticipator set too Correct heat anticipatorlow setting

Vibration in thermostat Correct source of vibrationThermostat in warm-air Shield thermostat from draftdraft or relocate thermostat

Connect voltmeter Dirty air filters (furnace) Clean or replace filterbetween l ine voltageconnections to primary Blower running too slow Speed up blower for 85 tocontrol (black and 95 temperature riseWhite leads). If burnercyc les due to powerinterruption, it is cycling Blower motor seized or Replace motoroff limit. b u r n e d o u t

Blower bearings seized Replace bearings and shaft

Blower wheel dirty Clean blower wheel

Blower wheel in back- Reverse blower wheelwards

If voltage fluctuates, thenfault is in power source. Wrong motor rotation Replace with motor ofRecheck voltage at power correct rotationsource

Disconnect thermostat Restrictions in return air or Correct cause of restric-wires at primary control. supply air system tion

1. If burner turns off, Adjustable limit control Reset limit to maximumfault is in thermostat set too low stop settingcircuit2. If burner does not turnoff, fault is in the primary Loose wiring connection Locate and securecontrol.. connec- tion

Low or fluctuating line Call power companyvoltage

AII-17

Table K

Oil Burner Troubleshooting (Continued)

Burner starts and fires but locks out on safety

Source Procedure (1) Procedure (2) Cause Correction

Poor fire After burner fires, If burner continues to Unbalanced fire Replace nozzleimmediately place run, fault may be due Too much air – lean Reduce combustionjumper across flame to poor fire. Inspect short fire air – checkdetector terminals at fire. combustionprimary control Too little fire – long Increase combustion

dirty fire air – checkcombustion

Excessive draft Adjust barometricdamper for correctdraft

Too little draft or C o r r e c t d r a f t o rRestriction remove restriction

Flame detector

Dirty cad cell face Clean cad cell faceF a u l t y c a d c e l l Replace cad cell–exceeds 1,500 ohmsLoose or defective Secure connectionscad cell wires Or replace cad cell

If fire is good, fault is holder and wire leadsin flame detector.Check detectorcircuit. Primary control R e p l a c e p r i m a r y

circuit defective control

Primary control If burner locks out onsafety, fault is inprimary control.

AII-18

Source

Thermostat

Table K

Oil Burner Troubleshooting (Continued)

Burner runs continuously (too much heat)

Procedure

Disconnect thermostat wiresat primary control

1. If burner turns off, fault isin the thermostat circuit.

2. If burner does not turn off,the fault is in the primarycontrol.

Cause

Shorted or welded thermostatcontacts

Stuck thermostat bimetal

Thermostat not level

Shorted thermostat wires

Thermostat out of calibration

Thermostat in cold draft

Defective primary control

Correction

Repair or replace thermostat

Clear obstruction or replacethermostatLevel thermostat

Repair short or replace wires

Replace thermostat

Correct cause of draft orrelocate thermostat

Replace primary control

AII-19

Table L

Common Operating Difficulties for Oil Burners

Condition Check for

Furnace pulsates on starting, stopping, or during Proper adjustment of the nozzle electrode assembly landoperation. blast tube in relation to each other and firebox.

Improper draft. Ensure no downdraft. Leaks in chimney.Defective nozzle.Air in the line, between fuel unit and nozzle.

Flame is raw and stingy. Too large an opening in the air adjustment.Partly plugged nozzle.Air in the pump.

Ignition points collect carbon. Ignition points too close to nozzle.Nozzle loose in holder.Improper oil cutoff when burner is shutdown.

Oil pump is noisy. Air in oil line.Leaks in suction line.Plugged strainer.

Burner starts and stops too frequently. Thermostat is improperly wired.Thermostat is improperly adjusted.Drive arm adjustment is incorrect.Limit control is set too low.Plugged air filters.Nozzle is too large for unit.

Burner failsafe is activated. Low voltage occurring at night.Incorrect polarity of wiring.Primary control or stack switch improperly adjusted.

No oil at the nozzle Fuel too low in the supply tank.Plugged nozzle.Leak in the suction line.Leak in the vacuum-gauge port.Pump failing to turn.Leaking strainer gasket.Leaking pump-shaft seal.Fuel unit not operating.

AII-20

Table M

CONDITION

NO OIL FLOW ATNOZZLE

Oil Pump Troubleshooting

CAUSE REMEDY

Oil level below intake line in supply tank Fill tank with oil.

Clogged strainer or filter

Clogged nozzle

Air leak in intake line

Restricted intake line (High-vacuum reading)

Remove and clean strainer. Replace filter element.

Replace nozzle.

Tighten all fittings in intake line. Tighten unusedintake port plug. Check filter cover and gasket.

Replace any kinked tubing and check any valves inintake line

A two-pipe system that becomes air bound Check for and insert bypass plug. Make sure returnline is below oil level in tank.

A single-pipe system that becomes air bound Loosen gauge port plug or easy flow valve andbleed oil for 15 seconds after foam is gone in bleedhose. Check intake line fitting for tightness. Checkall pump plugs for tightness.

OIL LEAK

Slipping or broken coupling

Frozen pump shaft

Loose plugs or fittings

Leak at pressure adj. Screw or nozzle plug

Blown seal (single-pipe system)

Tighten or replace coupling.

Replace pump.

Dope with good quality thread sealer. Retighten.

Washer may be damaged. Replace the washer orO-ring.

Check to see if bypass plug has been left in unit.Replace oil pump.

Blown seal (two-pipe system) Check for kinked tubing or other obstructions inreturn line. Replace oil pump.

NOISY OPERATION

Seal leaking

Cover

Bad coupling alignment

Replace oil pump.

Tighten cover screws or replace damaged gasket.

Loosen fuel unit mounting screws slightly and shiftfuel unit in different positions until noise iseliminated. Retighten mounting screws.

Air in inlet line Check all connections. Use only good flare fittings.

Tank hum on two-pipe system and inside tank Install return line hum eliminator in return line.

PULSATING PRESSURE Partially clogged strainer or filter Remove and clean strainer. Replace filter element.

Air leak in intake line Tighten all fittings.

Air leaking around cover Be sue strainer cover screws are tightenedsecurely. Check for damaged cover gasket.

IMPROPER NOZZLE To determine the cause of improper cutoff, insert a pressure gauge in the nozzle port of the fuel unit.CUT-OFF After a minute of operation, shut burner down. If the pressure drops from normal operating pressure and

stabilizes, the fuel unit is operating properly and air is the cause of improper cutoff. If, however, thepressure drops below 80 psig, oil pump should be replaced.

Filter leaks Check face of cover and gasket for damage.

Strainer cover loose Tighten four screws on cover.

Air pocket between cutoff valve and nozzle Run burner, stopping and starting unit, until smokeand after-fire disappears

Air leak in intake line Tighten intake fittings. Tighten unused intake portand return plug.

Partially clogged nozzle strainer Clean strainer or change nozzle.

Leak at nozzle adapter Change nozzle and adapter.

AII-21

Table N

Troubleshooting Chart for Thermostats

PROBLEM PROBABLE CAUSE POSSIBLE REMEDY

Thermostat fails to energize heating Setting too low Check and increase setting.system

Wired incorrectly Correct wiring.

Loose or broken wiring Replace or repair wiring

Loose unit or mounting plate

Dirty contacts

Level and tighten mounting screws

Clean contacts

Affected by warm draft Relocate.

Mercury tube broken Replace thermostat.

Improper type for job

Thermostat fails to de-energize Setting too highheating system

Replace with proper type.

Check and decrease setting

Affected by cool draft

Improper type for job

Relocate.

Replace with proper type

Wired incorrectly Correct wiring.

Contacts fused together Replace unit.

Not level (mercury switch type) Level and tighten mounting screws.

Wiring shorted Locate short and repair.

Room temperature does not reach Defective dialthermostat setting or else exceedsthe setting

Calibrate or replace unit.

Improper type for job

Thermometer reading incorrect

Defective components

Replace with proper type

Replace unit.

Replace unit

Heating components too small or Check and correct if feasible.too large for area

System short-cycles Improper type for job Replace with proper type.

Dirty contacts

Incorrectly set thermostat heater

Clean contacts.

Adjust or replace.

Heating components too large for Decrease output.area

AII-22

Table O

Troubleshooting Hot-Water Heating Systems

SYSPTOMS REMEDY

Boiler smokes through the feed doors Clean the boiler flues and the flue pipes. Repair any chimneyleaks.

Boiler heats slowly Increase the draft. Check on the type of fuel. Clean the boilerof scale. Blowdown the boiler.

Radiator produces insufficient heat Clean the boiler of scale. Change to a larger boiler. Blowdownthe boiler. Increase the draft, and check on the type of fuel.

Radiators do not heat Insufficient water in the system. Bleed the air from the system.Open the radiator valves, and check the operation of thecirculation.

Distribution piping does not transfer hot water to the radiators Insufficient water in the system. Bleed the air from the highpoints in the distribution piping. Check the operation of thecirculation pump. Check for corrosion stoppage in thedistribution piping.

AII-23

Table P

Inspection and Maintenance of Coppers and Other Steam-Related Equipment

INSPECTIONPOINT

SYMPTOMS TIME POSSIBLETROUBLE/CAUSES

POSSIBLECORRECTIONS

Steam jacket Not heating When noted No steam; valve stuckclosed; trapmalfunctioning

Check steam supply; freestuck valve

Steam jacket Stays hot When noted Valve partly open or Repair or replace valvescored seat

Steam jacket Leaks Monthly Rapid changes intemperature causingcracks; faulty weld

R a i s e h e a t s l o w e r ;re-weld bust or crack

Pipe joints

Pipe joints

Leaks

Corrosion

Monthly

Monthly

Joint made incorrectly; Unscrew; clean and repairnot tight joint

Leaks or condensation Repair and/or clean

Control valves Stuck open or closed When noted No steam or too muchsteam; packing too tightor valve frozen

Loosen packing gland orfree frozen valve steam

Control valves Leaks at stem Weekly Packing not tight enough Tighten packing

Condensate strainer No flow When noted Restricted strainer Clean strainer

Steam trap Malfunctioning Every 6 months Parts worn or dirty Disassemble, clean, andrepair

Lagging Broken or crushed Quarterly Water soaked; stepped Replace defectiveon sections

Reducing valve Incorrect pressure When noted Parts worn or dirty Disassemble, clean, andrepair; clean and adjustpressure every 6 months

Leaks or corrosion Replace or repair valveWhen notedSafety valve Stuck open or liftingunder pressure

Clean and lubr ica tehinges

When noted Hinges dirtyCovers Tight operation

Resurface or replace. DONOT REPLACE WITHREGULAR GATEVALVE

When notedDrawoff valve Leaks Scored

AII-24

Table Q

Troubleshooting for Dishwashing Machine

TROUBLE PROBABLE CAUSE POSSIBLE REMEDY

Dish racks slide off chain Change of tension of either chainconveyor

Reset idler sprockets to proper tensionon each chain.

Water pressure too low Spray nozzles or slot plugged. Strainer Dismantle spray assembly. Wash outbaskets plugged. Slipped belts on all piping and clean parts. Disassemblepumps. and clean strainer. If belts are frayed or

torn, replace them. Adjust tension byresetting idler pulley or by movingmotor on sliding base

Water splashing on floor or Leaks around doors; torn curtains or Realign door. Repair or replace gasket.into wrong compartment curtains not in proper position Repair or realign curtain. Readjust

spray to keep it within limits of tank.

Rinse water temperature is Insufficient heat from booster heater Remove scale from steam coil. Correctless than 180°F leaking fittings. Adjust gas burners.

Calibrate or replace thermostat.

Spot or film on eating utensils Wash water saturated with grease. S t o p o p e r a t i o n a n d c l e a n a l lafter final rinse Dirty tank. Weak sprays in wrong equipment. Adjust speed of conveyor.

direction. Improper detergent mixture Examine spray equipment. Cleannozzles, spray pipes, scrap trays, andstrainers. Check piping for leaks.Check to see if valves are operatingproperly. Examine pump. Cleanimpellor if necessary

AII-25

Table R

Troubleshooting Chart for Ovens, Ranges, and Boilers

Trouble Check

OIL-FIRED OVENS

Cause

MOTOR:Will not start -

Runs, but fails to light oven -

COMBUSTION FLAME:Disorganized & smoky -

UNEVEN COOKING:

IGNITION:Difficult -

BURNER:Starts, functions properly, but fails

after short intervals -

Puffs when started -

Runs, but flame pulsates -

COMBUSTION CHAMBER:Smoke in chamber or in chimney-

Carbon forms in chamber -

– Fuse.

– Thermostat.

– Solenoid valve.

– Fuel tank.

– Ignition.

– Transformer.

– Fuel nozzle.

– Damper.

– Flue pipes.

– Secondary air damper door.

– Oil supply.

– Burner openings.

– Suction line.

– Strainers.

– Oil tank vent.

– Controls.

– Ignition.

– Draft.

– Draft.

– Chimney.

– Air.

– Nozzle.

– Oil burning rate.

– Nozzle (oil spray on walls)

Blown.S e t b e l o w b a k i n g c h a m b e rtemperature. Reset.Activated. Or foreign particles invalve.

Empty.Carbon on electrodes.Damaged, bad. Replace.Clogged. Clean.

Closed.Heavy soot deposits.

Too far open or too near shut.Adjust.

Too low. Open valve.Shut off by solenoid valve.

Dirty. Clean.Air leak. Repair.Clogged. Clean.Obstructed. Clean.Out of order or improperly adjusted.Poor or delayed. Clean nozzle.

Insufficient.Insufficient.A downdraft.

– Insufficient

– Clogged or defectiveReplace

– Excessive. Reduce.– Dirty or incorrect model.– Clean/Replace.

AII-26

Table R

Troubleshooting Chart for Ovens, Ranges, and Boilers (Continued)

Trouble Check Cause

OIL-FIRED OVENS–Continued

FIRE:On one side -

OIL CONSUMPTION:High -

SOLENOID VALVE:Fails to function -

PILOT FLAME:Inoperative or too low -

OVEN:Overheats -

Underheats -

OVEN OR RANGE:Fails to ignite –

Does not heat fast enough –

Cooks unevenly –

No gas –

– Nozzle.

– Air

– Heat-absorbing surfaces.

– Oil storage tank.

– Valve itself.

– Thermostat.

– Connections.

– Emergency bypass valve.

– Fuel passage.

– Solenoid valve.

– Thermostat.

– Solenoid valve.

– Fuel line.

– Fuel shutoff valve.

– Vaporizing parts.

– Pilot flame.

– Main gas or shutoff valve.

– Air shutter.–

– Gas input.

– Cooling damper.–

– Flue.

– Doors.

– Bypass Flame.

– Main service valve.

– Solenoid valve.

Dirty or damaged. Clean/replace.

Too little. Increase.Dirty. Clean ducts.Leaks. Repair.

Dirty or defective. ReplaceDamaged. Replace.Defective. Replace.Open.

Clogged. Clean.Adjust setscrew to increase fuel topilot flame.

Damaged. Replace.Stuck plunger, Dirty.Clean.Clogged. Clean/replace.

– Not fully open.

– Full of carbon. Clean.

– Insufficient or none.

– Closed. (adjacent to unit)

– Completely closed.

– Too Low or out of adjust-ment.

– Open.

– Too much draft. (pulls heatthrough flue).

– Don’t close tightly. Clean,

– Adjust.

– Closed.

– Clogged, dirty or defec-tive. Clean/replace.

AII-27

Table R

Troubleshooting Chart for Ovens, Ranges, and Boilers (Continued)

OVEN OR RANGE:Constant "burning"–

Temperature rises, when not in use –

– Draft.

– Thermostat.

– Low flame setting.

– Too much. Remove Draft.

– Faulty. Replace.

– Is too high. (Cut low flame to aminimum.)

Fumes in room – – Chimney – Faulty, backdraft or impropergas adjustment.

– Fans in room. – Runn ing wi th door s andwindows closed.

Flare back on turndown – – Bypass flame.

FIELD RANGES

– Too low, adjust.

FUEL SYSTEM;Fails to maintain pressure –

PREHEATER:Fails to ignite –

BURNER:Fails to ignite –

Flame too low –

BURNER FLAME:Yellow –

– Fuel filter.

– Air valve.

– Fuel tank.

– Safety valve.

– Fuel feed tube assembly.

– Preheater generator.

– Preheater generator.

– Generator.

– Feed tube assembly.

– Generator.

– Generator flame valve.

– Leaks. Replace gasket.

– Defective. Replace.

– Defective. Replace.

– Does not reseat. Replace.

– Damaged or missing. Replace.

– Defective. Replace.

– Defective. Replace.

– Defective. Replace.

– Missing, clogged or dented.Clean/Replace.

– Defective.

– Defective. Repack/replace.

GENERATOR OR PREHEATERVALVE:

Fuel leaks –

– Generator flame valve.

– Generator.

– Defective. Repack/replace.

– Defective. Replace

AIR PRESSURE GAUGE:Pressure rises above safe limit - – Valves. – Defective. Repack or replace.

– Fuel tank. – Too full. Only 8 quarts.

– Gauge. – Defective. Replace

AII-28

Table S

Troubleshooting Chart for Clayton Steam Generator

Trouble Possible Cause Remedy

Feedwater pump failing to maintain Accumulator blowdown valve open Inspect accumulator blowdownproper water level in accumulator or leaking. valve.gauge glass.

Feedwater pump not primed. Prime pump.

Insufficient water to feedwater Check water supply to pump.pump. Ensure intake valve is open.

.Feedwater strainer clogged. Clean strainer.

Feedwater pump check valves not Clean and inspect check valves.operating properly

Water pump solenoid not releasing. Remove water level electrodes andclean off rust and dirt.Check wate r pump solenoidarmature and linkage for binding.

Circulating pump failing to maintain Low oil level in water pump causing Ensure oil is maintained at properproper feed volume to heating coil, reduced pump capacity. level.causing thermostat interruption.

Priming valve not operating Clean and inspect priming valve.properly.

Circulating pump check valves not Clean and inspect check valves.operating properly.

Vapor lock of circulating pump due On installations where there areto abrupt steam demand causing low sudden heavy steam demands, apressure in accumulator. back pressure valve should be

installed to retain a normal steampressure in the accumulator duringthese periods.

Circulating pump not primed. Prime circulating pump.

AII-29

Table S

Troubleshooting Chart for Clayton Steam Generator (Continued)

Water System

Too much water (unit operating with Water pump solenoid not operating. 1. Check for burned out solenoid coilhigh water level in gauge glass). or open circuit to solenoid.

2. Remove and clean water levelelectrodes. Corrosion on electrodesmay cause insulating effect andprevent operation of solenoid.3. Check for defective water levelrelay.

Noisy water pump operation.

Stream trap plugged. Remove and clean steam trap.

Flexible coupling loose between Tighten setscrews in f lexiblemotor and pump. coupling.

Pump intake surge chamber fouled. Check and clean intake surgechamber.

Water pump cycles rapidly.

Restricting heating coil causing Check feed pressure for coilexcessive feed pressure. restriction.

Leads to water level electrodes Check wiring to electrodes (seereversed. wiring diagram).

AII-30

Table S

Troubleshooting Chart for Clayton Steam Generator (Continued)

Fuel System

Trouble Possible Cause Remedy

Low or no fuel pressure. Fuel supply exhausted or supply Check fuel supply. Ensure all valvesCAUTION: Stop plant immediately lines restricted. in the supply line are open.to avoid damage to the fuel pump.

Burner fails to ignite.

Fuel bypassing through burner Burner control valve must be airtightcontrol valve. and all air pockets eliminated.

Fuel pressure not adjusted properly. Adjust fuel pressure.

Air leak in supply line causing loss Suction line must be airtight and allof prime. air pockets eliminated.

Fuel pump failure. Replace fuel pump

Faulty ignition. Check and adjust ignition electrodes.Check ignition transformer andcable.Check for low voltage conditionwhich may a weak spark from thetransformer.

Safety switch in combustion control Actuate reset on control. Also checklocked out. for continuity of circuit between

combustion control and flamedetector (under burner manifold).

Fuel pressure switch failure. Check and adjust fuel pressureswitch.

Burner nozzles not replaced in Ensure nozzles are replaced afterburner. cleaning burner manifold.

Insufficient fuel pressure. Check causes and remedies under"Low or No Fuel Pressure."

Oil valve failing to open. Check for burned out solenoid.

AII-31

Table S

Troubleshooting Chart for Clayton Steam Generator (Continued)

Fuel System

Trouble Possible Cause Remedy

Partial or improper burner operation Low fuel pressure. Check causes and remedies undercausing low steam pressure at "Low or No Fuel Pressure."normal load.

Burner shuts off before maximum Thermostat control interruption due Correct cause of low water conditionsteam pressure is reached. to low water condition. immediately. Test thermostat for

proper control.

Smoke from flue outlet. To prevent Improper air supply to burner.sooting of the heating coil andburner, correct this conditionimmediately.

Check air adjustment/

Fuel pressure not adjusted properly. Adjust fuel pressure.

Carboned, loose, or worn burner Clean and tighten burner nozzles.nozzles. Replace if worn.

Heating coil sooted. Remove soot from heating coil.

Dirt or sludge in fuel oil or incorrect Ensure fuel is clean and is the propergrade of fuel used. grade.

Fluttering burner shuts off during Oil valve not seating properly.automatic operation.

Oil drip from burner. Oil valve not seating properly.

Check and clean solenoid valve.

Check and clean solenoid valve.

Dead or fluttering fire. Heating coil sooted. Remove soot.

Improper air adjustment. Check air adjustment.

Motor fails to start, or stops during Power failure or tripped circuit Check power lines. Reset circuitoperation breaker. breaker.

Safety shutdown caused by overload Wait 2 or 3 minutes for overloads torelays cool; then press reset on magnetic

controller and restart unit. Check forcause of overload

Motor noisy or running hot. Motor running single phase Check for blown fuse or trippedcircuit breaker in feeder lines.

Magnetic controller fails to contact. Operating coil failure. Replace coil.

AII-32

Table T

Problem

Troubleshooting Chart for Washers

Check Cause

Motor will not run.

Machine will not shut off.

Power to machine.Door switchWater level controlMotorTimer

TimerWiring

None, check outletDefective, check all controlsFaulty, replaceFaulty, repair or replaceFaulty, replace

Defective, replaceBreak, repairFaulty, replace

Timer will not advance to next cycle. Timer motor Defective, replaceTimer Bound shaft or knob, clear

NOTE: Timer does not advance during Water level control Faulty, replacewater fill period until the water level switchhas been satisfied.

Incorrect fill or temperature Water level control Faulty water level control.Thermal element Faulty, repair or replaceHot-water supply Inadequate, adjust temperatureHoses Reversed, correct

No water Water valvesHosesFill hose screenFill solenoidWater level controlMachine

Closed, Turn on valves.Unkink hoses.Clean dut screen.Replace solenoid.Replace control.Check controls and power atoutlet.

Water will not shut off. TimerWater level controlMix and fill valveValve

Defective, replaceDefective, replaceForeign particles, cleanDefective, replace

AII-33

Table T

Troubleshooting Chart for Washers (Continued)

Problem Check Cause

Water will not drain from washer

No spray rinse

Drain hosePumpSudsTransfer valveTimerBelt

Water supplyTimer

Kinked/clogged, unkink/clearDoes not run, readjust and tightenLock, remove suds, add cold waterFaulty, replaceDefective, replaceLoose, adjust

None, same as no waterDefective, replace

Slow spin

Excessive vibration

No agitation

Water leakage.

Belt/clutch

WasherFlooringLoadWasher feetSnubber or suspension bolts

MotorTimer contacts.Faulty transmission.Defective control solenoid.LinkageWater level switch

Inlet hoseDrain hosesHoseGasketHousing

Slips, adjust

Not level, adjust legsWeak, reinforce floorUnbalanced, redistributeNo rubber cups, install themDamaged, replace

Failure, repair or replace.Faulty, replace timer.Faulty, repair or replaceDefective, replace solenoids.Broken, repair or replace.Faulty, replace switch

Loosely connected, tightenLoosely connected, tightenBroken, repair or replaceLeaky, replaceCracked, replace parts

No recirculation of water during Pumpagitation Pump drive

HoseDistribution valve

Jammed, cleanDefective, replace coupling ortightenClogged, cleanDefective, clean out, replace valveor solenoid

Torn clothing BleachAgitatorBasket

Improper usageBroken, replaceDefective, replace

AII-34

Table U

Troubleshooting Chart for Residential Dryers

Problem What to check for

Motor does not start Service cord disconnected

Circuit breaker tripped or a blown fuse

Wiring loose or broken

Loading door open

Door switch defective

Motor defective

Dryer does not shut off Timer motor jammed

Clock spring broken

Stop pin in improper positioning

Timer contact points are closed

Motor grounded or windings shorted out

Dryer dries slowly Clothes are too wetLint box is cloggedThermostat is set too lowVoltage is lowDryer is overloaded

Dryer is noisy Suction fan alignment is incorrectLoose fan or loose fan pulleyLoose or dry fan beltThere are loose items between the drum and the cylinderLoose screws

AII-35

Table V

Troubleshooting Checklist for Refrigeration Systems

TROUBLE POSSIBLE CAUSE CORRECTIVE MEASURE

High condensing pressure. Air or non-condensable gas insystem.

Inlet water warm.

Purge air from condenser.

Increase quantity of condensingwater.

Insufficient water flowing through Increase quantity of water.condenser

Low condensing pressure.

Condenser tubes clogged or scaled Clean condenser water tubes.

Too much liquid in receiver, Draw off liquid into servicecondenser tubes submerged in cylinder.liquid refrigerant.--

Insufficient cooling of air-cooled Check fan operation, cleanliness ofcondenser condenser, and for adequate source

of air flow

Too much water flowing through Reduce quantity of watercondenser

Water too cold. Reduce quantity of water

Liquid refrigerant flooding back Change expansion valvefrom evaporator. adjustment, examine fastening of

thermal bulb.

Leaky discharge valve Remove head, examine valves.Replace anv found defective.

High auction pressure. Overfeeding of expansion valve.

Leaky suction valve.

Low suction pressure. Restricted liquid line and expansion Pump down, remove, examineandvalve or suction screens. clean screens.

Regulate expansion valve, .checkbulb attachment.

Remove head, examine valve andreplace if worn.

Insufficient refrigerant in system.- - Check for refrigerant storage.

Too much oil circulating in system. Check for too much oil incirculation.Remove oil.

Improper adjustment of expansion Adjust valve to give more flow.valves.

Expansion valve power elementdead or weak.

Low refrigerant charge.

Replace expansion valve powerelement

Locate and repair leaks. Chargerefrigerant.

AII-36

Table V

Troubleshooting Checklist for Refrigeration Systems (Continued)

TROUBLE POSSIBLE CAUSE CORRECTIVE MEASURE

Compressor short cycles on Thermal expansion valve not Adjust, repair, or replace thermallow-pressure control. feeding properly. expansion valve.

1. Dirty strainers. 1. Clean strainers.2. Moisture frozen in orifice or 2. Remove moisture or dirt (Useorifice plugged with dirt. system dehydrator).3. Power element dead or weak. 3. Replace power element.

Compressor short cycles on Water flow through evaporators Remove restriction. Check waterlow-pressure control (continued).. restricted or stopped. Evaporator flow. Clean coils or tubes.

coils plugged, dirty, or cloggedwith frost

Compressor runs continuously.

Compressor short cycles onhigh-pressure control switch.

Defective low-pressure control Repair or replace low-pressureswitch. control switch.

Shortage of refrigerant. Repair leak and recharge system.

Leaking discharge valves. Replace discharge valves.

Insufficient water flowing through Determine if water has been turnedcondenser, clogged condenser. off.

Check for scaled or fouledcondenser.

Defective high-pressure controlswitch.

Repair or replace high-pressurecontrol switch.

AII-37

Table V

Troubleshooting Checklist for Refrigeration Systems (Continued)

TROUBLE POSSIBLE CAUSE CORRECTIVE MEASURE

Compressor will not run. Seized compressor. Repair or replace compressor.

Cut-in point of low-pressure control Set L.P. control switch to cut-in atswitch too high. correct pressure.High-pressure control switch does not Check discharge pressure and resetcut-in. H.P. control switch.

1. Defective switch.1. Repair or replace switch.

2. Electric power cut off.2. Check power supply.

3. Service or disconnect switch open.4. Fuses blown. 3. Close switches.

4. Test fuses and renew if necessary.5. Overload relays tripped.

5. Reset relays and find cause of6. Low voltage. overload.

6. Check voltage (should be within 107. Electrical motor in trouble. percent of nameplate rating).

8. Trouble in starting switch or control 7. Repair or replace motor.circuit.

9. Compressor motor stopped byoil-pressure differential switch.

8. Close switch manually to testpower supply. If OK check controlcircuit including temperature andpressure controls.

9. Check oil levels in crankcase. Checkoil pressure.

Sudden loss of oil from Liquid refrigerant slugging back tocrankcase.

Adjust or replace expansion valve.compressor crankcase.

AII-38

Table V

Troubleshooting Checklist for Refrigeration Systems (Continued)

TROUBLE

Capacity reduction systemfails

POSSIBLE CAUSE CORRECTIVE MEASURE

Hand-operating stem of capacity Set hand-operating stem to automaticcontrol valve not turned to automatic position.position.

Compressor continues to Pressure-regulating valve not Adjust or repair pressure-regulatingoperate at full or partial load. opening. valve.

Capacity reduction system Broken or leaking oil tube between Repair leak.fails to load cylinders. pump and power element.

Compressor continues tooperate unloaded.

Pressure regulating valve not Adjust or repair pressure regulatingclossing. valve.

AII-39

Table W

Troubleshooting Industrial Refrigeration

PROBLEM POSSIBLE CAUSE REMEDY

Compressor will not start No power to motor Check power to and from fuses; replace fuses if necessaryCheck starter contacts, connections, overloads, and timer (ifpart winding start). Reset or repair as necessary.Check power at motor terminals.Repair wiring, if damaged.

Control circuit is open Safety switches are holding circuit open. Check highpressure, oil failure, and low-pressure switches. Also checkoil filter pressure differential switch is supplied.Thermostat is satisfied.Check control circuit fuses if blown; replace.Check wiring for open circuit.

Motor "hums" but does not start Low voltage to motor Check incoming power for correct voltage. Call powercompany or inspect/repair power wiring.Check at motor terminals. Repair or replace as necessary.

Motor shorted Check at motor terminals. Repair or replace as necessary

Single-phase failure in the three-phase Check power wiring circuit for component or fuse failure.power supply

Compressor is seized due to damage Remove belts or coupling. Manually turn crankshaft to checkor liquid compressor.

Compressor is not unloaded Check unloader system.

Compressor starts but motor Compressor has liquid or oil in Check compressor crankcase temperature.cycles off on overloads cylinders Throttle suction stop valve on compressor to clear cylinders

and act to prevent recurrence of liquid accumulation.

Suction pressure is too high Unload compressor when starting. Use internal unloaders ifpresent.

Motor control

Install external bypass unloader.

Motor control located in hot ambient.Low voltage.Motor overloads may be defective or weak.Check motor control relay.Adjust circuit breaker setting to full load amps.

Bearings are "tight" Check motor and compressor bearings for temperature.Lubricate motor bearings.

Motor is running on single-phase Check power lines, fuses, starter, motor, etc., to determinepower where open circuit has occurred.

Compressor starts but short cycles Low refrigerant charge Check and add if necessary.automatically

Driers plugged or saturated with Replace cores.moisture

AII-40

Table W

Troubleshooting Industrial Refrigeration (Continued)

PROBLEM POSSIBLE CAUSE REMEDY OR COMMENT

Compressor starts but short cycles Refrigerant feed control is defectiveautomatically (continued).

No load

Unit is too large for load

Repair or replace

To prevent short cycling, if objectionable,install pump-down circuit, anti-recycle timeror false load system.

Reduce compressor speed.Install false load system.

Suction strainer blocked or restricted Check and clean or replace as necessary.

Motor is noisy or erratic Motor bearing failure or winding failure Check and repair as needed.

If electric starter, check calibration on Adjust as necessarycontrol elements

Compressor runs continuously but does not Load is too high Speed up compressor or add compressorkeep up with the load capacity.

Reduce load.

Refrigerant metering device is underfeeding, Check and repair liquid feed problems.causing compressor to run at too low a Check discharge pressure and increase ifsuction pressure low.

Faulty control circuit, may be low pressure Check and repair.control or capacity controls

Compressor may have broken valve plates. Check compressor for condition of parts.This condition can usually be detected bychecking compressor discharge temperature.

Thermostat control is defective and keeps Check temperatures of product or space andunit running compare with thermostat control. Replace or

readjust thermostat.

Defrost system on evaporator not working Check and repair as needed.properly

Suction bags in strainers are dirty and restrict Clean or remove.gas flow

Hot gas bypass or false load valve stuck Check and repair or replace.

Compressor loses excessive amount of oil High suction superheat causes oil to vaporize Insulate suction lines.Adjust expansion valves to proper superheat.Install liquid injection (suction linedesuperheating).

Too low of an operating level in chiller will Raise liquid level in flooded evaporatorkeep oil in vessel (R-12 systems only).

Oil not returning from compressor Make sure all valves are openCheck float mechanism and clean orifice.Checka nd clean return line.

AII-41

Table W

Troubleshooting Industrial Refrigeration (Continued)

PROBLEM POSSIBLE CAUSE REMEDY OR COMMENT

Compressor loses excessive amount of oil Oil separator is too small Check selection.(continued).

Broken valves cause excessive heat in Repair compressor.compressor and vaporization of oil.

"Slugging" of compressor with liquid "Dry up" suction gas to compressor byrefrigerant that causes excessive foam in the repairing evaporator.crankcase Refrigerant feed controls are overfeeding.

Check suction trap level controls.Install a refrigerant liquid transfer system toreturn liquid to high side.

Noisy compressor operation Loose flywheel or coupling

Coupling not properly aligned

Loose belts

Tighten.

Check and align if required.

Align and tighten per specs.Check sheave grooves.

Poor foundation or mounting Tighten mounting bolts, grout base, or installheavier foundation.

Check compressor with stethoscope if noise Open, inspect, and repair as necessary.is internal

Check for liquid or oil slugging Eliminate liquid from suction mains.Check crankcase oil level.

Low evaporator capacity Inadequate refrigerant feed to evaporators Clean strainers and driers.Check expansion valve superheat setting.Check for excessive pressure drop due tochange in elevation, too small of lines(suction and liquid lines). A heat exchangermay correct this.Check expansion valve size.

Expansion valve bulb in a trap

Oil in evaporator

Change piping or bulb location to correct.

Warm the evaporator, drain oil, and install anoil trap to collect oil.

Evaporator surface fouled

Air or product velocity is too low

Clean.

Increase to rated velocity.Coil not properly defrosting.Check defrost time.Check method of defrost.

Brine flow through evaporator may be Chiller may be fouled or plugged.restricted Check recirculating pumps.

Check process piping for restriction.

Discharge pressure too high Air in condenser

Condenser tubes fouled

Water flow is inadequate

Purge noncondensibles.

Clean.

Check water supply and pump.

AII-42

Table W

Troubleshooting Industrial Refrigeration (Continued)

PROBLEM POSSIBLE CAUSE REMEDY OR COMMENT

Discharge pressure too high (continued). Water flow is inadequate (continued). Check control valve.Check water temperature.

Airflow is restricted

Liquid refrigerant backed up in condenser

Check and clean:Coils.Eliminators.Dampers.

Find source of restriction and clear.If system is overcharged, remove refrigerantas required.Check to make sure equalizer (vent) line isproperly installed and sized.

Discharge pressure too low

Spray nozzles on condensers plugged Clean.

Ambient air is too cold Install a fan cycling control system.

Water quantity not being regulated properly Install or repair water regulating valve.through condenser

Refrigerant level low Check for liquid seal, add refrigerant ifnecessary

Evap condenser fan and water switches are Reset condenser controls.improperly set

Suction pressure too low Light load condition Shut off some compressors.Unload compressors.Slow down RPM of compressor.Check process flows.

Short of refrigerant Add if necessary

Evaporators not getting enough refrigerant Discharge pressure too low. Increase tomaintain adequate refrigerant flow.Check liquid feed lines for adequaterefrigerant supply.Check liquid line driers.

Refrigerant metering controls are too small Check superheat or liquid level and correct asindicated.

Suction pressure too high Low compressor capacity Check compressors for possible internaldamageCheck system load.Add more compressor capacity.

AII-43

Table X

Troubleshooting Laundry Equipment

WASHERS

TROUBLE

DRAIN VALVE FAILURE:Drain fails to close -

CHECK

– Master switch.– Drain switch.– Drain finger.

– Interior light not lit.

PROBLEM

– Turned OFF.– At OPEN.– Not touching the timer cylinder or

touching at a dirty spot.– Drain relay not working, or contacts

are dirty.

Drain fails to open -

– Pilot solenoid valve not working.– Low air or water pressure.– Piston cup.

– Exhaust line from pilot valve tosoap chute.

– No voltage, or valve piston stuck.– Adjust pressure regulator.– Needs replacement.

– Clogged.

WATER VALVE FAILURE:Valve fails to open –

– Drain valve. – Rusted or broken spring.

– Drain valve cylinder. – Dented.

– Pressure regulator. – Faulty.

– Master switch.– Appropriate water switch.– Water finger.

– Turned OFF.– Turned OFF.– Not touching the timer cylinder or

touching at a dirty spot.

– Drain valve.– Valve itself.

– Pilot orifice in inlet of valve.– Valve piston.– Water pressure.– Water level control.

– Is OPEN.– Shorted coil or broken wire to inlet

valves.– Clogged.– Binding.– Too high.– Not operating due to float binding.

Valve fails to close -– Level control switches (inside).– Water pressure.– Strainers, water inlet line.

– Not operating.– Extremely low.– Dirty or clogged.

– Water valve coil.– Water pressure.– Piston return spring (valve).– Piston or pilot orifice.– Level control float chamber.– Level control float.– Float rod adjusting collars.

– Short or ground.– Extremely low.– Broken.– Clogged.– Clogged.– Cracked or faulty.– Set too close together.

AII-44

Table X

TROUBLE

Troubleshooting Laundry Equipment (Continued)

WASHER

CHECK PROBLEM

TIMER CYLINDER:Does not turn –

AUTOMATIC CONTROLS:(washer cylinder running)

Do not operate –

– Master switch.– Water level.– Zero level starching.– Clutch (joins the timer motor shaft

to the time cylinder).– Timer motor.– Timer cylinder motor.

– Transformer.– Signals operate.

– Drain switch.

– Not at formula.– Not attained.– Improper switch position.– Loose setscrew.

– No voltage.– Bad. Replace motor and gear case.

– Defective.– Faulty drain relay or drain finger

does not touch the drain cylinderscreen.

– At OPEN.

MILTROL:Operates but does not run, or runs in – Faulty.one direction – – Reversing control timer motor. – Burned out.

– Reversing control contactor coil.– Microswitch (on reversing control – Faulty.

cam mechanism).– Voltage. – Low.– Wiring. – Broken or shorted.– Signal relay or contacts. – Faulty or dirty contacts.

AII-45

Table X

Troubleshooting Laundry Equipment (Continued)

WASHER

TROUBLE CHECK PROBLEM

MOTOR:Fails to start – – Power.

(20, 26 inch models & 30 inch manual– Failure.

brake machines)– Line fuses.

– Overload relay.– Blown.

– Tripped.– Wiring. – Loose or broken connections.– Microswitch.

Fails to start –– Not actuating properly.

(26 & 30 inch automatic brake – Interlock switch.machines)

– Faulty.– Brake air cylinder. – Piston cup binding.

MOTOR RUNS:– Brake "VN". – Locked manually.

Machine fails to come up to speed- –

– Load.

– Voltage.– Not properly balanced.

– Connections in switches or wiring.– Low or frequency low.

– Fuses.– Loose or broken in switch or wiring.

– Blown.– Commutator brushes.

– Interlock or brake shoes.– Dirty or worn.

BRAKE NOT RELEASING:Extractor turned on: – Curb in basket.

– Dragging.

(20 inch)– Jammed by foreign materials.

Extractor turned on –(26 & 30 inch)

– Brake mechanism.

– Voltage.

– Brake pressure spring.

– Solenoid wiring.

– Solenoid plunger binding.

– Low or low frequency.

– Too much tension.

– Loose connection.

– Exhaust port or pilot solenoid valve.– Clogged.

EXTRACTOR RUNNING:Makes knocking noise –

E X T R A C T O R N O R M A LOUT-OF-BALANCE LOAD:Fails to carry –

– Microswitch.

– Pilot solenoid valve.

– Floor mounting.

– Packing nut.

– Spindle pulley.

– Rubbers.

– Basket.

– Bearings.

– Motor pulley.

– Bad.

– Jammed open.

– Not properly bolted.

– Loose.

– Loose on spindle.

– Worn.

– Loose on spindle.

– Bad.

– Loose on shaft.

– Rubbers.

– Motor.

– Brake.

– Too loose or too tight.

– Not developing full power.

– Not fully releasing when motor is turnedon.

– Floor mounting. – Not fully bolted down.

AII-46

Table Y

Troubleshooting Checklist for Domestic Refrigerators and Freezers

Trouble Possible Causes

1. Unit fails to start Wiring

What to look for and what to do

Loose connections, broken wires, grounded leads, open contacts,blown fuses, poor plug contacts, poorly soldered connections.Correct defects found.

Low voltage Rated voltage should be ± 10 percent. Overloaded circuits; read thevoltage across the compressor-motor terminals; if it reads 100 voltsor under, the circuit is overloaded. Check the voltage at the fusepanel; if this voltage is low, the power supply voltage needscorrection. Provide a separate circuit for the unit.

Compressor motor Remove leads from the compressor motor. Apply 115 volts to themotor running winding terminals on the terminal plate from aseparate two-conductor cable. Then, touch a jumper wire across boththe starting and the running winding terminals. If the motor startsand runs, the trouble is isolated in the control or in the compressormotor thermostat. If the unit does not start, replace it.

Motor thermostat Connect a jumper to shunt the thermostat from the line-side terminalof the thermostat across to the common terminal of the compressormotor. If the compressor starts, the thermostat is open and should bereplaced. Do not attempt to correct calibration of the thermostat.Replace the thermostat.

2. Unit runs normally but tempera- Temperature selector control Reset the dial to its normal position.ture is too high set too high

Temperature control out of Readjust in accordance with the manufacturer’s instructions.adjustment

Poor air circulation in the Paper on shelves; too much food in storage; other obstructions tocabinet proper air circulation. Maintain sufficient space in the cabinet for

proper air’ circulation.

Damper control faulty On models with this type of control it is best to replace the control orto follow the manufacturer’s instructions.

3. Unit runs normally but tempera- Temperature selector control Reset the control to a higher position.ture is too low out of adjustment

Temperature control out of Readjust the control in accordance with the manufacturer’sadjustment instructions

4. Unit runs too long and tempera- Temperature bulb improperly Replace or relocate the bulb in accordance with the manufacturer’sture is too low located or defective instructions. Be sure the bulb is securely attached to the evaporator.

Replace defective bulbs.

Compressor Refer to item 7.

AII-47

Table Y

Troubleshooting Checklist for Domestic Refrigerators and Freezers (Continued)

Trouble Possible Causes What to look for and what to do

5. Unit does not run and tempera- No power at outlet Check the fuses, and replace burned-out ones.ture is too high

Poor plug contact Spread the plug contacts.

Control in "Off" position Turn to the "Coldest" position, then back to the “Normal” position

Temperature control Examine the control main contacts; clean them with a magneto file orinoperative with fine sandpaper; replace them if they are badly burned or pitted.

Do not use emery cloth. Check and replace the relay assembly, ifnecessary. If the temperature control main contacts are found open,try warming the temperature control bulb by hand. If this does notclose the control contacts, the control bellows has lost its charge, andthe control should be replaced.

Pressures in sys tem not Wait for a period of about 5 minutes before trying to restart the unit.equalized See item 3.

Open circuit in wiring Make voltmeter or test-lamp checks to determine whether any part ofthe electrical wiring system is open, or any controls are inoperative.Correct defective connections, and replace worn or damaged controls

Compressor thermostat open See item 1.

Open motor windings See item 1.

6. Unit runs for short periods; Defrosting heater On a unit equipped with a defrosting heater, check the defrostingtemperature too high cycle in accordance with the manufacturer’s instructions. Ascertain

whether the defrosting heater is turned off by making sure that nocurrent flows through it during the refrigerating cycle.

Unit operates onthermostat

See item 9.

7. Unit runs continuously; tempera- Moisture, obstruction, or Before checking for moisture, be certain that the symptoms observedture too high restriction in liquid line are not caused by improper operation of the defrosting heater, if so

equipped. These heaters are wired into the cabinet wiring so that thecontrol contacts short out the heaters when the contacts are closed.Thus the heaters are on only when the machine is off, when thecontrol contacts open, and when the evaporator is on the defrostcycle. Check the control contacts to see that the defrosting heaters areoff when the machine is running. At high ambient temperature, theunit will cycle on its thermostat. The evaporator will warm up over itsentire surface is the liquid circulation is completely obstructed. If it isonly partly obstructed, a part of the frost on the evaporator will melt.Under these conditions, the unit will probably operate noisily, and themotor will tend to draw a heavy current. If the liquid line is obstructedby ice, this ice will melt after the unit has warmed up. The unit willthen refrigerate normally. If this obstruction occurs too frequentlyand spare units are available, replace the unit.

Broken valves Exceedingly high current to the motor. No cooling in the evaporatorand no heating in the condenser. Excessive compressor noise.Replace the hermetic compressor or replace the valves in anopen-type compressor.

Clogged tubing Check the tubing for damage, sharp bends, kinks, pinches, etc.Straighten the tubing, if possible, or replace the unit.

AII-48

Table Y

Troubleshooting Checklist for Domestic Refrigerators and Freezers (Continued)

Trouble Possible Causes What to look for and what to do

7. Unit runs continuously; tempera- Refrigerant leaks or under- The unit may tend to run normally but more frequently. Theture too high (Continued) charged evaporator becomes only partly covered with frost. The frost will

tend to build up nearest to the capillary tube while the section nearestto the suction line will be free from frost. As leakage continues, thefrostline will move back across the evaporator. When the refrigerantis entirely gone, no refrigeration will occur. Units with largeevaporators will not frost up unless the evaporator is mounted insideof the box. Test for leaks with a halide leak detector. Recharge theunit, if necessary.

Cabinet light Check the operation of the light switch, see that the light goes out asthe door is closed.

Air circulation See that sufficient space is allowed for air circulation. Relocate orreposition the unit, if possible.

Evaporator needs defrosting

Gasket seals

Ambient temperature

Advise the user on defrosting instructions.

Give them a thorough cleaning. If worn they should be replaced.

Relocated the unit tin a location where the ambient temperatureranges from 55 degrees to 95 degrees

Defroster heater On units so equipped, check the defroster heater circuit. See item 6.

Compressor suction valves Ascertain whether the condenser gets warm, and check the currentsticks open or is obstructed by drawn by the motor. If the condenser does not get warm and thecorrosion or dirt current drawn is low, disassemble the compressor (open type) and

check the action of the suction valve

Compressor discharge valve Connect the test gauge assembly, run the unit until the low-sidesticks open or is obstructed pressure is normal. With an ear in close proximity to the compressor,

listen for a hissing sound of escaping gas past the discharge valve.The low-side pressure gauge will rise, and the high side will dropequally until both are the same. Clean out obstructions.

8. Unit runs too long; temperature Condensertoo high

Fan

Check for any obstruction in the path of air circulation around thecondenser. Clean any dust accumulation.

On units so equipped, check to see that the fan blades are free to turnand that the fan motor operates.

Door seal Clean seals around the door. Check closure of the door with a strip ofpaper between the gasket and the cabinet at all points around the door.The gasket should grip the paper tightly at all points.

Refrigerant

User

Check for leakage and undercharge of the refrigerant. See item 7.

Warn the user against too frequent opening of the door, storage of hotfoods, heavy freezing loads, and other improper usage.

9. Unit operates on thermostat; Voltagetemperature too high

Check voltage ± 10 percent of rating.

Defrosting heater

Starting relay

See that the defrosting heater is turned off.

Determine that the starting relay does not stick closed. Follow themanufacturer's instructions on methods of checking.

AII-49

Table Y

Troubleshooting Checklist for Domestic Refrigerators and Freezers (Continued)

Trouble Possible Causes

9. Unit operates on thermostat; Condensertemperature too high (Continued)

Pressures not equalized

What to look for and what to do

Check the air circulation around the condenser; also check theoperation of the fan.

Wait 5 minutes after stopping, then restart; turn to the coldestposition, then to the normal position

10. Noisy operation

Restrictions in liquid line

Thermostat

Fan blades

See item 7.

Thermostat may be out of calibration. Replace the thermostat.

If the blades are bent, realign them, and remove any obstructions. Ifthe blades are so badly bent or warped that they cannot be realigned,they should be replaced.

Fan motor

Tube rattling

Food shelves

Compressor

Check the motor mounting and tighten the connections.

Adjust the tubes so that they do not rub together.

Adjust them to fit tightly.

Malfunctioning valves; loose bolted connections; improperalignment of open-type compressor. Replace the hermeticcompressor tighten the connections; realign the open-typecompressor

Floor or walls Check to see that the floor is rigid, and whether the walls vibrate.Locate and correct any such sources of noise. Make corrections bybolting or nailing loose portions to structural members.

Belt Check the condition of the motor belt. Replace it when it becomesworn or frayed.

11. Unit uses too much electricity Door

Usage

Check the door seal. See item 7.

Instruct the user on proper usage of the motor. See item 8. Check theoverload.

Ambient temperature too high See item 7. The unit will operate more frequently and over longerperiods of time in a high-temperature atmosphere. Correct, ifpossible, by changing the location of the unit.

Defrost control Check the defrost circuit according to the manufacturer'sinstructions

Temperature control Selector control dial set too low. Advise the user. Operate it as near tothe "Normal" setting as possible.

12. Stained ice trays Poor cleaning procedures Use soap and warm water to wash trays. Rinse them thoroughly. Donot use metal sponges, steel wool, or course cleaning powders.

AII-50

Table Z

Troubleshooting Chart for Air Conditioners

Type of Unit Complaint

With open-type compressor Electric motor will notstart

Cause

Power failure

Compressor stuck

Belt too tight

Manual reset in starter open

Thermostat setting too high

Low voltage

Burned-out motor

Frozen compressor caused bylocked or damaged mechanism

Intermittent power interruptionUnit cycles on and off

High-pressure cutout defective

High-pressure cutout set too low.Overload opens after having beenreset

Leaky liquid-line solenoid valve

Dirty or iced evaporator

Lack or refrigerant

Restricted liquid-line strainer

Overcharge or refrigerant ornon-condensable gas

Lack or refrigerant

Restricted liquid-line strainer

Faulty motor

Filters dirty

Faulty motor

Coil frosts Filters dirty

Not enough air over coilNot enough air over coil

Defective expansion valveDefective expansion valve

Possible Remedy

Check circuit for power source

Locate cause and repair

Adjust belt tension

Determine cause of overload and repair.Reset overload cutout

Lower thermostat setting

Check with voltmeter, then call powercompany

Repair or replace

Remove and repair compressor

Tighten connections or replace defectivepower supply parts

Replace high-pressure cutout

Raise cutout pressure. Check voltage andcurrent drawn

Repair or replace

Clean or defrost evaporator. Check filtersand fan drive

Remove excess refrigerant or purgenon-condensable gas

Repair refrigerant leak and recharge

Clean strainer

Repair or replace faulty motor

Clean filters

Clean or remove restriction from supplyor return ducts or grilles

Replace valve

AII-51

Table Z

Troubleshooting Chart for Air Conditioners (Continued)

Type of Unit Complaint Cause Possible Remedy

With open-type compressor Unit runs but will not Unit not fully charged Recharge slightly, then check for leaks in(continued) cool the refrigerant circuit, then fully charge

Leaky suction valve Remove compressor cylinder head andclean or replace valve plate

Expansion valve not set correctly Adjust expansion valve

Strainer clogged Remove, clean, and replace valve

Air in refrigerant circuit. Moisture Purge unit of air. Clean orifice and installin expansion-valve orifice silica gel dryer

Flash gas in liquid line Add refrigerant

No air blows from Ice or dirt on evaporator Clean coil or defrostsupply grille

Blower belt broken or loose

Blower bearing frozen

Adjust belt tension, or replace belt

Repair or replace bearing and lubricate asdirected

Discharge pressure too Improper operation of condenser Correct airflow. Clean coil surfacehigh

Air in system

Overcharge of refrigerant

Discharge pressure too Lack of refrigerantlow

Purge

Remove excess or purge

Repair leak and charge

Broken or leaky compressor Remove head, examine valves and replacedischarge valves those found to be operating improperly

Suction pressure too Overfeeding of expansion valve Regulate superheat setting expansion valvehigh and check to see that remove bulb is

properly attached to suction line

Expansion valve stuck in open Repair or replace valveposition

Broken suction valves in Remove head, examine valves and replacecompressor those found to be inoperative

Suction pressure too low Lack of refrigerant Repair leak and charge

Clogged liquid line strainer Clean strainer

Expansion-valve power assembly Replace expansion-valve power assemblyhas lost charge

Obstructed expansion valve Clean valve and replace if necessary

Contacts on control thermostat Repair thermostat or replace if necessarystuck on closed position

AII-52

Type of Unit

With hermet ic motor-compressor combination(continued)

Table Z

Troubleshooting Chart for Air Conditioners (Continued)

Complaint

Compressor runs contin-uously; good refrigerationeffect

Compressor runs contin-uously; unit is too cold

Compressor runs contin-uously; little refrigerationeffect

Compressor runs contin-uously; no refrigeration

Compressor short cycles,poor refrigeration effect

Cause

Air over condenser restricted

Thermostatic switch contactsbadly burned

Thermostatic switch bulb hasbecome loose

Thermostatic switch improperlyadjusted

Extremely dirty condenser

No air circulating over condenser

Ambient temperature too high

Load too great

A restriction that prevents therefrigerant from entering theevaporator. A restriction isusually indicated by a slightrefrigeration effect at the point ofrestriction

Compressor not pumping. A coold i s c h a r g e l i n e a n d a h o tcompressor housing wouldindicate this. The wattage isgenerally low.

Short of refrigerant

Loose electrical connections

Defective thermostatic switch

Defective motor starter

Air restriction at evaporator

Possible Remedy

Remove restriction or provide for more aircirculation over the condenser

Replace thermostatic switch

Secure bulb in place

Readjust thermostatic switch

Clean condenser

Provide air circulation

Provide ventilation or move to a coolerlocation

Analyze load

Locate the possible points of restriction, andtry jarring it with a plastic hammer, orheating to a temperature of about 110degrees F. If the restriction does not open,replace the unit.

Replace the unit

See manufacturer's instructions

Locate loose connections and make themsecure

Replace thermostatic switch

Replace defective motor starter or relay

Remove air restriction

AII-53

Table Z

Troubleshooting Chart for Air Conditioners (Continued)

Type of Unit Complaint Cause

With hermetic motor- Compressor short cycles, Dirty condensercompressor combination no refrigeration(continued)

Possible Remedy

Clean the condenser

Ambient temperature too high Provide ventilation or move to a coolerlocation

Defective wiring Repair or replace defective wiring

Thermostatic switch operating Replace thermostatic switcherratically

Relay erratic Replace relay

Compressor runs too Poor air circulation around the Increase the air circulation around thefrequently condenser or too high ambient condenser . In some local i t ies the

temperature temperature is extremely high, and nothingcan be done to correct this

Load too great. Worn compressor. Analyze end use. Replace unit or bring it toGenerally accompanied by rattles the shop for repairsand knocks

Compressor does not run Motor is not operating If the trouble is outside the sealed unit, itshould be corrected; for example, wiresshould be repai red or replace andthermostatic switches or relays should bereplaced. If the trouble is inside the sealedunit, the sealed unit should be replaced.

Compressor will not run If the cabinet has been moved, Wait an hour or so, and then attempt to start(Assume that the some oil may be on top of the the motor by turning the current on and offthermostatic switch and piston many times. On some compressors, it mayrelay, and the electric be necessary to wait 6 or 8 hourwiring and current supplyare in good condition andoperating normally)

Compressor may be stuck, or some Replace the unitparts may be broken

Connections may be broken on the Replace the unit. Sometimes after sealedinside of the unit, or the motor units have been standing idle for a long time,winding may be open the piston may be stuck in the cylinder wall.

It is sometimes possible to start thecompressor by turning on the current andbumping the outer housing with a rubbermallet.

Compressor is unusually Condenser is dirty, or there is a Clean the condenser; increase the airhot lack of air circulation circulation

AII-54

Table Z

Troubleshooting Chart for Air Conditioners (Continued)

Type of Unit

With hermetic motor-compressor combination(continued)

Complaint Cause

Unusually heavy service or load

Possible Remedy

If possible, decrease load. Perhaps anotherunit is required

Low voltage Too small feed wires could cause this. Ifthe wires feeding the refrigerating unitbecomes warm, it is an indication that theyare too small and should be replaced withlarger wires

A shortage of oil Add oil if possible; if this is not possible,the unit must be replaced. A shortage ofrefrigerant will cause a shortage of oil inthe crankcase of the compressor

No refrigeration after Generally, during a long shutdown, Allow the compressor to operate until itsstarting up after a long an amount of liquid refrigerant will internal heat drivers the liquid refrigerantshutdown or on delivery get into the crankcase of the from the crankcase . Under some

compressor. When this happens, the conditions, this may take as long as 24compressor operation will cause no hours. This time can be shortened bynoticeable refrigeration effect until turning an e lec t r ic heater on thethe entire liquid refrigerant has compressor and raising the compressorevaporated from the crankcase. temperature, not exceeding 110 degrees F.

Compressor is noisy Mountings have become worn or Replace the rubber mountings. Place adeteriorated. The walls against piece of sound-absorbing material on thewhich the unit is placed may be of wall against which the unit is placed, oran extremely hard surface and may move the unit to a new location.resound and amplify the slight noisefrom the compressor into the room

Shortage of oil and/or refrigerant Add oil and refrigerant if possible. If it isimpossible, the unit must be replaced.

The sealed unit mechanism has Replace the unitbecome worn

After each defrosting Slight shortage of refrigerantthere is a long on cyclebefore refrigeration isagain normal

Add refrigerant if possible; if not, replacethe unit

Condenser is dirty Clean the condenser

Thermostatic switch bulb is loose Secure the bulb in place

There is a restriction between the Attempt to remove the restriction byreceiver or condenser and/or the jarring with a plastic hammer or by heatingevaporator the possible points of restriction to about

110 degrees F. If this does not correct thetrouble, the unit must be replaced orbrought to the shop for repairs

AII-55

APPENDIX III

MATH TABLES

CONVERSIONS, EQUIVALENTS AND USEFUL FORMULAS

TABLE A

EQUIVALENTS

1 inch = 25 millimeters1 foot = 0.3 meter1 yard = 0.9 meter

1 square inch= 6.5 sq. centimeters1 square foot= 0.09 square meter1 square yard= 0.8 square meter

1 cubic inch= 16 cubic centimeters1 cubic foot= 0.03 cubic meter1 cubic yard= 0.8 cubic meter

1 ounce = 30 grams16 ounces = 1 pound1 pound = 450 grams1 liter = 1 quart (lq)1 teaspoon = 5 ml1 tablespoon = 15 ml1 cup = 250 ml4 cups = 1 quart1 gram = 0.035 ounces (avdp)1 kilogram = 2.2 pounds (avdp)1 ounce (avdp)= 28 grams1 pound (avdp)= 0.45 kilogram

1 pound per square inch =0.07 kilograms per square centimeter

1 mile = 1.6 kilometers 1 kilogram per square centimeter =1 kilometer = 0.6 mile 14.2 pounds per square inch1 inch = 2.5 cm1 millimeter = 0.04 inch1 cubic centimeter = 0.06 cubic inch 1 Kilowatt= 1.3 horsepower

1 meter = 3.3 feet1 meter = 1.1 yards1 square meter = 11 square feet1 square meter = 1.2 square yards1 cubic meter = 35 cubic feet1 cubic meter = 1.3 cubic yards

1 cubic meter = 250 gallons1 quart (lq.)= 1 liter1 gallon= 0.004 cubic meter

1 horsepower = 0.75 kilowatt

AIII-1

TABLE B

CONVERSION OF ENGLISH MEASURE TO METRIC/ENGLISHMEASURE

MULTIPLY

Cubic feetCubic feetCubic feetCubic feetCubic feetCubic feetCubic feetCubic feetCubic inchesCubic inchesCubic inchesCubic inchesCubic inchesCubic inchesCubic inchesCubic inchesCubic yardsCubic yardsCubic yardsCubic yardsCubic yardsCubic yardsCubic yardsCubic yardsFeetFeetFeetFeetFeet of waterFeet of waterFeet of waterFeet of waterFeet of waterGallonsGallonsGallonsGallonsGallonsGallons

BY

2.832 x 106

17280.028320.037047.48128.3259.8429.9216.395.787 x 10-4

1.639 x 10-5

2.143 x 10-5

4.329 x 10-2

1.639 x 10-2

0.034630.017327.636 x 105

2746.6560.7646202.0764.61616807.930.480.3048.361/30.029500.8826304.862.430.433537850.13372313.785 x 10-3

4.951 x 10-3

3.785

TO OBTAIN

Cubic cmscubic inchescubic meterscubic yardsgallonsliterspints (liq)quarts (liq)cubic centimeterscubic feetcubic meterscubic yardsgallonsliterspints (liq)quarts (liq)cubic centimeterscubic feetcubic inchescubic metersgallonsliterspints (liq)quarts (liq)centimetersmetersyardsyardsatmosphereinches of mercurykgs per sq meterpounds per sq ftpounds per sq inchcubic centimeterscubic feetcubic inchescubic meterscubic yardsliters

AIII-2

TABLE B (Continued)

CONVERSION OF ENGLISH MEASURE TO METRIC/ENGLISHMEASURE

MULTIPLY

InchesInchesInchesInches of mercuryInches of mercuryInches of mercuryInches of mercuryInches of mercuryInches of waterInches of waterInches of waterInches of waterInches of waterInches of waterOuncesOuncesOuncesOuncesOunces (fluid)Ounces (fluid)PoundsPoundsPoundsPoundsPoundsPounds of waterPounds of waterPounds of water

BY

2.540104

.030.033421.133345.370.730.49120.0024580.0735525.400.57815.2040.036138437.528.350.06251.8050.029577000453.61632.170.82290.0160227.680.1198

TO OBTAIN

centimetersmilsyardsatmospherefeet of waterkgs per sq meterpounds per sq ftpounds per sq inchatmospheresinches of mercurykgs per sq meterounces per sq inpounds per sq ftpounds per sq inchdramsgrainsgramspoundscubic incheslitersgramsgramsouncespoundalspounds (av)cubic feetcubic inchesgallons

AIII-3

TABLE C

CONVERSION OF METRIC/ENGLISH TOENGLISH MEASURE

LitersLitersLitersLitersMetersMetersMetersMetersMetersMetersMillimeters

MULTIPLY

CentilitersCentimetersCentimetersCentimetersCentimetersCubic centimetersCubic centimetersCubic centimetersCubic centimetersCubic centimetersCubiccentimeters CubiccentimetersCubic centimetersCubic metersCubic metersCubic metersCubic metersCubic metersCubic metersCubic metersCubic metersKilogramsKilogramsKilogramsKilogramsKilometersKilometersKilometersLitersLitersLitersLiters

BY

0.010.39370.01393.7103.531 x 10-3

6.102 x 10-2

10-61.306 x 10-6

2.642 x 10-4

10-22.113 x 10-3

1.057 x 10-3

104

35.3181.0231.303264.21 0 2

211310571 0 2

70.932.20461.102 x 10-2

3281107

1093.6102

0.0353161.02103

1.308 x 10-2

0.26422.1131.0571003.280839.3710- 3

103

1.093625

TO OBTAIN

Litersinchesmetersmilsmillimeterscubic feetcubic inchescubic meterscubic yardsgallonsliterspints (liq)quarts (liq)cubic centimeterscubic feetcubic inchescubic yardsgallonsliterspints (liq)quarts (liq)gramspoundalspoundstons (short)feetmetersyardscubic centimeterscubic feetcubic inchescubic meterscubic yardsgallonspints (liq)quarts (liq)centimetersfeetincheskilometersmillimetersyardsinches

AIII-4

TABLE D

USEFUL FORMULAS

AIII-5

APPENDIX IV

ANSWER KEY

CHAPTER 1 — BOILERS

STEAM GENERATION THEORY

Q1.

Q2.

Q3.

Temperature increases and the volume expands.

Heat intensity.

Temperature of steam and boiling water.

BOILER DESIGN REQUIREMENTS

Q4. 1) Safe to operate; 2) Able to generate steam at desired rate andpressure; and 3) Economical.

Q5. American Society of Mechanical Engineers (ASME).

TYPES OF BOILERS

Q6.

Q7.

Water-tube and fire-tube.

1) Scotch Marine; 2) Vertical-tube; 3) Horizontal return; and 4)Firebox.

Q8. They require no setting.

BOILER FITTINGS AND ACCESSORIES

Q9.

Q10.

Q11.

Q12.

Lowest point of the boiler spaces.

Annually.

At the steam drum above the water level and 6 inches below thewater level.

1) Float operated; 2) Float and mercury switch; and 3) Electrodeprobe.

Q13.

Q14.

Q15.

Three.

Safety valve.

Backup to main steam stop.

AUTOMATIC CONTROLS

Q16.

Q17.

Q18.

Q19.

Pressure regulating.

Combustion control.

The air damper.

Manual reset.

AIV-1

INSTRUMENTS AND METERS

Q20. Indicating rate and indicating the total.

Q21. Pressure difference producing the flow.

BOILER WATER TREATMENT AND CLEANING

Q22.

Q23.

Q24.

Q25.

Q26.

Precipitates of hardness.

External and internal.

30 ppm and 60 ppm.

Causticity exists.

70°F.

CLEANING BOILERS FIRESIDES AND WATERSIDES

Q27.

Q28.

Q29.

Q30.

1) Wire brush and scraper; 2) Hot-water washing; 3) Wet-steamlancing; and 4) Sweating.

70 to 150 psig.

Pitting and general corrosion.

1) Hydrochloric acid; 2) Phosphoric acid; 3) Sulfamic acid; 4)Citric acid; and 4) Sulfuric acid.

Q31. Circulation and fill and soak.

CHAPTER 2 — BOILER MAINTENANCE

MAINTENANCE OF AUXILIARY EQUIPMENT

Q1.

Q2.

Q3.

Q4.

Low water.

Plug valve opening on gauge glass.

1) Controlling high water; 2) Removing sludge and sediment;

3) Controlling chemical concentrations; and 4) Dumping a boiler forcleaning or inspection.

Tightness of all the parts and strength of the drum.

BOILER TUBES

Q5.

Q6.

Q7.

Q8.

Q9.

1) Name or trademark of manufacturer; 2) Heat number; 3) Classletter; 4) Specification number; and 5) Outside diameter, wallthickness, and length.

Arc welding equipment.

3/16" to 5/16".

1/8" to 3/16".

Drill a hole in the tube.

REPAIRING BOILER REFRACTORIES

Q10. Escape of steam created from moisture in the brick.

AIV-2

Q11. 2900° to 3000°F.

Q12. Improperly sealed doors.

BOILER OPERATIQNS

Q13.

Q14.

Q15.

Q16.

Q17.

Q18.

Q19.

To ensure equipment and the boiler are in sound operatingcondition and functioning properly.

Line-up boiler systems.

Open all drain valves between the boiler, the header, and the twostop valves.

1) Maintain proper water level and 2) present loss of ignition.

150°F.

25 psig.

Record continuous data of plant performance.

SAFETY

Q20.

Q21.

Q22.

Q23.

Hard hat, goggles, and safety toed shoes.

Green.

Safety valve.

Keys can be controlled easier than combination locks.

CHAPTER 3 — STEAM DISTRIBUTION SYSTEMS

EXTERIOR STEAM DISTRIBUTION SYSTEMS

Q1.

Q2.

Q3.

Underground and aboveground.

Their high cost of installation.

High cost of maintenance.

INTERIOR STEAM DISTRIBUTION SYSTEMS

Q4.

Q5.

Q6.

Q7.

Hydrostatic head.

Inhibits emission of heat from the heating system.

A return trap system has a gravity return and a condensate pumpsystem has a forced return.

Withdraws air and water from the system, separates them, expelsthe air, and pumps the water back to the boiler.

STEAM DISTRIBUTION SYSTEM COMPONENTS

Q8.

Q9.

Q10.

Q11.

Fin-tube and cast iron.

10°F or lower than that of the water.

Upright or standard, and inverted.

The bellows develops holes.

AIV-3

Q17.

Q12. Emvar and copper.

Q13. Pyrometric crayon test.

Q14. Storage and instantaneous.

Q15. Temperature regulator.

Q16. 1) Slip, 2) bellows, 3) swing, 4) expansion loop, and 5) ball.

Annually.

CHAPTER 4 — HEATING SYSTEMS

PRINCIPLES OF HEATING

Q1.

Q2.

Q3.

Q4.

Q5..

Combustion, friction, and chemical action or resistance to flow ofelectricity.

Temperature and pressure.

Heat intensity in degrees Fahrenheit or Celsius.

27.8°C.

Conduction, convection, and radiation.

COMBUSTIBLE FUELS

Q6.

Q7.

Natural gas, manufactured gas, and liquefied petroleum gas.

Hydrogen and carbon (hydrocarbons).

WARM-AIR HEATING EQUIPMENT

Q8.

Q9.

Q10.

Q11.

Q12.

Q13.

Q14.

Suspended vertical discharge, suspended horizontal discharge,and floor mounted.

In Kw.

Safety.

Condensation.

Atmospheric vaporizing burners.

Fuel level control valve.

Draft regulator.

WARM-AIR HEATING SYSTEMS

Q15.

Q16.

Q17.

Q18.

Q19.

Rate of delivery and temperature of the air delivered.

Vertical counter-flow, up-flow, highboy, lowboy, and horizontalunit.

Thermocouple control relay.

The limit control.

Burner compartment combustion, radiating compartment, andblower compartment.

AIV-4

Q20. The thermostat.

Q21. Spiral-bimetallic and mercury bulb.

Q22. 75 to 150 psi.

Q23. Manufacturer's instruction manual.

Q24. Flue gas analyzer.

DOMESTIC HOT-WATER HEATING AND HOT-WATER BOILERS

Q25.

Q26.

Increase the pressure of the boiler to operate the valve monthly.

"Sailswitch."

HOT-WATER HEATING DISTRIBUTION SYSTEM

Q27.

Q28.

Q29.

It is difficult to get enough circulation to avoid large temperaturedrops from one end of the system to the other.

Pneumatic compression tank.

Circulation of water, thus reducing heating capacity.

HIGH-TEMPERATURE HOT WATER SYSTEMS

Q30.

Q31.

Q32.

Q33.

350°F to 450°F.

Hot-water boilers or generators and cascade or direct contactheaters.

20 to 40 ppm.

True.

CHAPTER 5 — GALLEY AND LAUNDRY EQUIPMENT

GALLEY EQUIPMENT

Q1.

Q2.

Q3.

Q4.

Medical Department.

Self-contained.

True.

As needed.

Q5. 5°F

Q6. 138°F to 145°F.

Q7. Small particles could become embedded in food.

Q8. Blue.

Q9. Weekly.

Q10. Concrete or brick.

Q11. Quarterly.

LAUNDRY EQUIPMENT

Q12.

Q13.

88 minutes.

Five.

AIV-5

Q14.

Q15.

Q16.

Q17.

Q18.

Q19.

Q20.

Q21.

Q22.

Q23.

Q24.

Q25.

Q26.

25 psi.

30 psi.

Every 2 months.

True.

Ensure the proper power is being connected.

4 square feet.

True.

5 minutes.

Manufacturer's instructions.

Blower rotor blades.

Fill, agitate, drain, and spin.

Main drive motor.

Electric and gas.

CHAPTER 6 — REFRIGERATION

HEAT AND REFRIGERATION PRINCIPLES

Q1.

Q2.

Q3.

False.

A quantity of heat required to change the temperature of 1 poundof any substance 1°F compared to water.

Sensible heat is the increase of temperature, and latent heat is thechange of state.

Q4.. 12.7 psia.

Q5. Decreases its volume in proportion to the increase of pressure.

Q6. Condense into a liquid.

MECHANICAL REFRIGERATION SYSTEMS

Q7. Reciprocating, rotary, and centrifugal.

Q8. The external is positioned on the outside of the crankcase.

Q9. The inaccessibility or repair and low capacity.

Q10. Dry or flooded.

Q11. Refrigerators and window air conditioners.

Q12. To determine the presence and amount of vapor in the refrigerant.

REFRIGERANTS

Q13.

Q14.

Chloroflorocarbons and hydrochloroflorocarbons.

Reduced efficiency, mechanical problems, and dangerousconditions.

AIV-6

Q15.

Q16.

CFCs and HCFCs.

R-134a.

REFRIGERANT SAFETY

Q17.

Q18.

Q19.

False.

Anytime a refrigerant is discharged.

To avoid confusion.

REFRIGERATION EQUIPMENT

Q20. Remote equipment has a condenser at a remote location from themain unit.

Q21.

Q22.

Q23.

Q24.

Q25.

Q26.

Q27.

Between 30°F and 45°F.

A unit cooler type.

Ease of assembly and ease of relocation.

Single door and multi-door.

Hot gas and/or electric heater.

Heat exchanger.

The type of evaporator installed.

INSTALLATION OF REFRIGERATION EQUIPMENT

Q28.

Q29.

Q30.

Q31.

Q32.

Q33.

Hydrochloric acid.

To permit unrestricted airflow.

Vibration strain.

A neutral atmosphere within the tube or pipe.

Ten feet.

True.

MAINTENANCE, SERVICE, AND REPAIR OF REFRIGERATIONEQUIPMENT

Q34.

Q35.

Q36.

Q37.

Q38.

Q39.

Q40.

Q41.

To get its pressure lower than the storagecylinder.

Manifold gauge set and vacuum pump.

To remove moisture and air from the system.

Until a deep vacuum has been obtained.

Low-side charging.

Halide, electronic, or soap and water.

Condenser/receiver.

Vapor and liquid.

AIV-7

Q42. Single or multiple pass method.

MAINTENANCE OF COMPRESSORS

Q43.

Q44.

Q45.

Shaft bellows seals.

Weak refrigerant charge.

Leaks, high temperatures, or vibrations.

MAINTENANCE OF MOTORS

Q46.

Q47.

Q48.

Q49.

Q50.

Q51.

Q52.

Q53.

LOGS

Q54.

Mechanical and electrical.

After every repair or replacement.

A dehydrator.

35°F or below.

Across the component.

Ohmmeter on lowest setting.

A short.

True.

True.

Q55. False.

CHAPTER 7 — AIR CONDITIONING

PRINCIPLES OF AIR CONDITIONING

Q1.

Q2.

Q3.

Q4.

Q5.

Q6.

Q7.

Q8.

Effective temperature.

True.

Humidity.

Sling psychrometer.

True.

Air becomes saturated.

Permanent and throwaway types.

Velocity of the air.

AIR-CONDITIONING SYSTEMS

Q9.

Q10.

Q11.

Q12.

Q13.

Window-mounted and floor-mounted units.

User.

Package units.

Heat pumps.

Condenser to the evaporator.

AIV-8

Q14. Accumulate frost or ice.

Q15. Balance point.

Q16. Flooded shell and tube and dry-expansion.

Q17. Thermostatic.

Q18. Easy to make.

Q19. Mechanically or chemically.

Q20. Annually.

MAJOR SYSTEM COMPONENTS AND CONTROLS

Q21.

Q22.

Q23.

Q24.

Q25.

Q26.

Q27.

Q28.

Q29.

Q30.

Q31.

Q32.

By the method of moving air through the tower.

False.

Induced draft.

Counter flow or cross-flow.

Parallel flow.

Redwood.

2 gallons.

Domestic refrigerators and small water coolers.

Belt drive and crankshaft seal.

Thermostat.

Humidistat.

Motor overload protector.

AUTOMOTIVE AIR CONDITIONING

Q33.

Q34.

Q35.

Q36.

Q37.

Q38.

Q39.

Q40.

Q41.

Q42.

Q43.

Q44.

Q45.

According to the pressure exerted on the liquid or vapor.

Two-cylinder reciprocating, swash plate, and scotch yoke.

Reciprocating motion.

True.

VIR (valves-in-receiver).

True.

Know the system.

As a oily residue at the point of leakage.

Damaged or missing O-rings.

Liquid.

The suction accumulator/drier.

Universal type.

Environmental Protection Agency.

AIV-9

DUCTWORK

Q46. Conditioned air ducts, recirculating air ducts, and fresh air ducts.

Q47. Single return, multiple return, and a combination of the systems.

Q48. True.

Q49. Butterfly, multiple blade, and split damper.

Q50. Measure the "free" grille area.

AIV-10

APPENDIX V

REFERENCES USED TO DEVELOPTHE TRAMAN

NOTE: Although the following references were current when thisTRAMAN was published, their continued currency cannot be assured.Therefore, you need to be sure that you are studying the latest revision.

Air Handling Units, NFGS – 15720, Department of the Navy, Naval FacilitiesEngineering Command, Alexandria, VA, 1995.

Althouse, Andrew D., Alfred F. Bracciano, and Carl H. Turnquist, ModernRefrigeration and Air Conditioning, Goodheart-Willcox Co., Inc., 1992.

Boiler Care Handbook, Cleaver-Brooks Division of Aqua-Chem Inc., Milwaukee,WI, 1985.

Central Refrigeration Equipment for Air Conditioning, NFGS – 15601, Departmentof the Navy, Naval Facilities Engineering Command, Alexandria, VA, 1997.

Cleaver-Brooks Operation, Service and Parts Manual, Nos. 750-90 and 750-91,Cleaver-Brooks Division of Aqua-Chem Inc., Milwaukee, WI, 1983.

Extractor M3OEXTR1AE User Manual, Pellerin Milnor Corp., Kenner, LA, 1987.

Food Service Equipment, MIL-HDBK - 1119, Department of the Navy, NavalFacilities Engineering Command, Alexandria, VA., 1991.

Heating, Ventilating, Air Conditioning, and Dehumidifying Systems, NAVFACDesign Manual 3.3, Department of the Navy, Naval Facilities EngineeringCommand, Alexandria VA, 1987.

Heating, Ventilating, Air Conditioning, and Sheet Metal Work, TM 5-745,Department of the Army, Washington, DC, 1968.

Jazwin, Richard, The Four R's, Recovery, Recycling, Reclaiming, and Regulation,Business News Publishing Co., Troy, MI, 1992.

Laundry Dryer, 50 Lb., Model L34SMS30, Owner’s Manual, Cissell ManufacturingCompany, Louisville, KY, 1990.

Maintenance and Operation of Heating Systems, MIL-HDBK 1114/2, NavalFacilities Engineering Command, Alexandria, VA, 1964.

Navy Electricity and Electronics Training Series (NEETS), Introduction to CircuitProtection, Control, and Measurement, Module 3, NAVEDTRAB72-03-00-93, Naval Education, and Training and Professional DevelopmentTechnology Center, Pensacola, FL, 1993.

Open End Washer MT36OEW1DE Technical Manual, Pellerin Milnor Corp.,

Kenner, LA, 1987.

Steingness, Frederick M., Low-Pressure Boilers, American Technical

Publishers, Inc., Alsip, IL, 1981.

AV-1

INDEX

A Boiler maintenance—Continuedsteam injector, 2-4steam traps, 2-4testing, hydrostatic, 2-6valves, 2-3

Boiler operating logs, 2-23Boiler operations, 2-19

checks, 2-19, 2-22procedures, 2-21securing, 2-23

Boiler refractories, 2-14cementing brick, 2-14furnace liner, 2-17repairing, 2-14

Boiler tubes, 2-7belling, 2-12cleaning, 2-9composition, 2-7plugging, 2-12preparing tube ends, 2-10preparing tube sheets,removing, 2-8renewing, 2-8

Boiler water testing and treatment, 1-24laboratory equipment, 1-27methods of, 1-26scale, 1-25tests for chemicals, 1-29tests for solids, 1-34water impurities, 1-24

Acids, 1-39Accumulator and oil separator, 6-19Air, 7-4

circulation of, 7-4purity of, 7-4Air cock, 1-8

Air-conditioning maintenance, 7-16Air-conditioning principles, 7-1Air-conditioning units, 7-6

floor-mounted air-conditioning unit, 7-6window- mounted air-conditioning unit, 7-6heat pumps, 7-8

Air-conditioning systems, 7-5Air diffuser, 4-14Air distribution, 4-13Automotive air conditioning, 7-33Automotive compressors, 7-34

B

Belling tubes, 2-12Blowdown valves, 1-8Boilers, 1-1

accessories and equipment, 1-15automatic controls, 1-14circuit, 1-11CO2 meter (analyzer), 1-24combustion control, 1-19draft gauges, 1-21fittings and accessories, 1-7flame failure and operational controls, 1-20fuel oil pump, 1-21instruments and meters, 1-20safety valve, 1-12steam and air flowmeters, 1-21steam gauge, 1-18steam injector feed system, 1-13steam gauge, 1-18types of, 1-2

Boiler cleaning, 1-35acid cleaning, 1-40mechanical cleaning, 1-37

Boiler emergencies, 2-23Boiler maintenance, 2-1

feedwater regulator, 2-3gauge glass replacement, 2-3manhole gaskets, 2-5

C

Certification, technician, 7-42Chilled water systems, 7-10Chimneys, draft fans, and breechings, 1-8Cleaning of refrigerant system, 7-39Cleaning of boiler firesides and watersides, 1-35Condensate return pump, 3-15Cooling towers, 7-20Controls, 7-29Compressors,

air conditioner, 7-24automotive, 7-35multiple, 6-32

Comfort zones and lines, 7-1Controls, automatic boiler, 1-14Comfort zone chart, 7-3Condensers, 7-12

INDEX-1

D H

Dew point, 7-2Diagnosis and servicing air conditioning, 7-37Discharge pressure gauge and thermometer,

6-16Dryers, clothes, 5-30Ductwork, 7-43

E

Electrical defects, 6-48Evaporation, 6-8Extractor, 5-13

installation, 5-13maintenance and repair, 5-13troubleshooting, 5-14

F

Fans, 2-5Firebox boiler, 1-7Fire-tube boiler, 1-4Forced-air system, 4-12Fuels, combustible, 4-3Fuel pump, 4-37Furnace, 4-15

components, 4-17design, 4-16installation, 4-31maintenance, 4-33

Furnaces, gas fired, 4-15Furnaces, oil fired, 4-22, 4-24

maintenance, 4-35Fusible plugs, 1-9

G

Galley equipment, 5-1bakery ovens, 5-7dishwashers, 5-4field range, 5-7interceptorsranges, 5-6

and grease traps, 5-8

steam kettles, 5-1steam chests, 5-2steam tables, 5-3

Gas burner control system, 4-20Gases, 4-4Gravity system, 4-12Gauge glass, 1-12Gauges and thermometer, 6-19Gravity system, 4-12

Heat and refrigeration principles, 6-1atmospheric pressure, 6-4condensation, 6-6day-ton of refrigeration, 6-4effects of pressure on gases, 6-5latent heat, 6-3measurements of heat,nature of heat, 6-1

6-2

pressure, 6-4scale relationships, 6-5sensible heat, 6-3specific heat, 6-3total heat, 6-4transfer of heat, 6-2units of heat, 6-2vaporization, 6-6

Heaters, 4-6Heating, principles of, 4-1Heat pumps, 7-8Heat transfer, 4-3Heating systems, 4-1Hermetic compressor, 7-27High-temperature hot-water systems,

4-47types, 4-48piping, 4-51pressurization, 4-48

Hot-water heating, 4-38Hot-water heating systems, 4-47

maintaining and troubleshooting,Hot-water heating distribution, 4-41

gravity system, 4-42forced circulation system, 4-44

Hot-water boilers, 4-39Horizontal-return tubular boiler, 1-6

operation, 4-40fittings and accessories, 4-40

Humidity, 7-2Humidifier, 4-23Humidistats, 7-30Hydrostatic testing of boilers, 2-6

I

4-47

Inspection of refrigeration compressors,6-46

Inspection of air conditioning, 7-38

J

Joints, 3-16

INDEX-2

L

Laundry equipment, 5-9extractor, 5-13residential washers, 5-24steam generator, 5-16tumbler, 5-14washer, 5-10

Liquid line filter-drier or dehydrator, 6-18Lockout devices, 2-28Lockout procedures, 2-30Logs, boiler operating, 2-23Logs, refrigeration, 6-51

M

Maintenance of air conditioning, 7-16Maintenance of compressors, 6-45Maintenance of motors, 6-47Mechanical refrigeration, 6-8

O

Oil burner controls, 4-26Ozone protection and the Clean Air Act, 6-21

P

Plugs, 2-13Precautions, air conditioning servicing, 7-37Pressure temperature chart, 6-7Psychrometer, 7-2Pump, condensate return, 3-15

R

R e f r i g e r a n t s , 6 - 2 0R-12 Dichlorodifluoromethane, 6-20R-22 Monochlorodifluoromethane, 6-21R-502 Refrigerant 502, 6-21R-134a Tetrafluoroethane, 6-21R-717 Ammonia, 6-21R-125 Pentafluoroethane, 6-21Refrigerant leaks, 6-38Refrigeration cycle, 6-9Refrigeration principles of, 6-1

atmospheric pressure, 6-4condensation, 6-6day-ton of Refrigeration, 6-4effects of pressure on gases, 6-5latent heat, 6-3measurements of heat, 6-2nature of heat, 6-1

Refrigeration principles of—Continuedpressure, 6-4scale relationships, 6-5specific heat, 6-3sensible heat, 6-3total heat, 6-4transfer of heat, 6-2units of heat, 6-2vaporization, 6-6

Refrigeration systems, accessory devices, 6-16Refrigeration systems, control devices, 6-14

automatic expansion valve, 6-14capillary tube, 6-16compressor motor control, 6-16high-side float valve, 6-15low-side float valve, 6-15thermostatic expansion valve, 6-14

Refrigeration systems, corn ponents. of, 6-10condensers, 6-11compressors, 6-10diagram of, 6-16evaporators, 6-13liquid receiver, 6-13metering devices, 6-14

Refrigerant system evacuating, 6-37Refrigerant system, pumping down, 6-40Refrigerant, piping, 6-29Refrigerant transfer, 6-36Refrigerant, recovery, reclaiming, and recycling, 6-40Refrigerant safety, 6-22

handling and storage of refrigerant cylinders, 6-22personal protection, 6-22

Refrigeration equipment, 6-23reach-in refrigerators, 6-23walk-in refrigerators, 6-24

Refrigerators, domestic, 6-25single door fresh food refrigerator, 6-25two-door refrigerator-freezer combination, 6-26

Refrigeration equipment, installation of, 6-28Refrigeration system, component removal or

replacement, 6-43Refrigeration equipment, maintenance, servicing and

repair, 6-35Relief valve, 6-16Rotary screw compressor, 7-11

S

Safety, boiler, 2-25Safety valve, boiler, 1-12Safety precautions, 1-39, 2-26, 7-41Scotch marine boiler, 1-4

INDEX-3

Solenoid gas valve, 4-19Solenoid stop valve, 6-17Space heaters, 4-7Steam chests, 5-2Steam distribution, 3-1

conduit type, 3-1utilidor type, 3-2

Steam distribution systems, components of, 3-8air vent, radiator, 3-9radiators, 3-8steam traps, 3-9, 3-12

Steam distribution systems,aboveground, 3-2overhead, 3-2surface, 3-2underground, 3-1

Steam distribution systems, maintenance, 3-2Steam distribution systems, interior, 3-3Steam generation theory, 1-1Steam kettles, 5-1Steam tables, 5-3Suction line, 6-18Suction line filter-drier, 6-18

T

Temperature regulators, 3-15Thermocouple control relay, 4-21Thermostat switch, 6-17Thermostat control, 5-23Timer assembly, 5-26Traps, 3-9Traps, testing of, 3-13

ear, 3-14freeze protection, 3-14glove, 3-13pyrometer, 3-13

lpyrometer crayon, 3-13Troubleshooting refrigeration equipment, 6-50Troubleshooting air-conditioning equipment, 7-32

Two-pipe vapor system with a return trap, 3-4installation, 3-5maintenance, 3-5operation, 3-5

Two-pipe vapor system with a condensate pump,

3-6Two-pipe vapor system with a vacuum pump and a

condensate return, 3-7Trucks and bus air conditioning, 7-41

U

Unit heater, 4-5maintenance of, 4-11

V

Vapor method of refrigerant recovery, 6-41Vertical tube boiler, 1-5

W

Warnings against unsafe practices, 2-27Warm-air heating equipment, 4-4Washer, 5-10

operation, 5-10installation, 5-11maintenance and repair, 5-12troubleshooting, 5-12

Water cooled compressors, 7-14Water coolers and ice machines, 6-26Water column, 1-9Water heaters, 3-14Water level switch, 5-28Water pump, 5-27Water-tube boilers, 1-3

bent tube, 1-3sraight tube, 1-3

Water valves, 5-28Wire bristle brush, 1-38

INDEX-4

Assignment Questions

Information: The text pages that you are to study areprovided at the beginning of the assignment questions.

ASSIGNMENT 1

Textbook Assignment: "Boilers," chapter 1, pages 1-1 through 1-42.

1-1. A boiler may be defined as a closedvessel in which steam is produced as aresult of the burning of fuel.

1. True2. False

1-2. You are boiling water in an opencontainer at sea level. What is thehighest temperature the boiling watercan reach when the burner is set for400°F?

1. 612°F2. 400°F3. 212°F4. 200°F

1-3. What value must increase when youwant to increase the boiling point ofwater?

1. Pressure2. Heat3. Volume4. Evaporation rate

1-4. You are boiling water in a closedcontainer while maintaining a constantpressure on the steam and waterwithin it. What is the temperaturerelationship between the steam and theboiling water?

1. The steam temperature is higherthan the boiling water temperature

2. The temperature of the steam isinversely proportional to thetemperature of the boiling water

3. The temperature of the boilingwater is higher than thetemperature of the steam

4. The temperatures of the steam andboiling water are the same

1-5. Superheated steam is steam at atemperature higher than the saturationtemperature corresponding topressure.

1. True2. False

1-6. Which of the following is NOT arequired criteria for a boiler to beconsidered satisfactory for operation?

1. It must be safe to operate2. It must be able to generate steam

at the desired rate and pressure3. It must be economical to operate4. It must have a steel floor

1

1-7. What authority establishes designrules for boilers?

1.

2.3.

4.

Society of American MilitaryEngineers (SAME)American Welding Society (AWS)American Society of MechanicalEngineers (ASME)Department of OccupationalSafety and Health (OSHA)

1-8. The headers in a sectional-headercross drum boiler are made of whattype of material?

1. Forged steel2. Polished brass3. Aluminum4. Cast iron

1-9. Gases are directed across the tubes ofthe sectional-header cross drum boilera total of how many times beforebeing discharged from the boiler?

1. One2. Two3. Three4. Four

1-10. What number of plates go into themakeup of the box-header cross drumboiler?

1. Five2. Two3. Three4. Four

1-11. What types of drums are used in thebox-header longitudinal drum boiler?

1. Horizontal or inclined2. Vertical or inclined3. Vertical or horizontal4. Longitudinal or vertical

1-12. What types of drums are used in thebent-tube boiler?

1. Steam, water, and tube2. Tube, crosshead, and water3. Crosshead, tube, and steam4. Mud, steam, and water

1-13. Which of the following factors is adisadvantage of water-tube boilers?

1. Little flexibility in starting-up2. Low productive capacity3. Considerable danger of disastrous

explosion4. High construction costs

1-14. The Scotch marine boiler is classifiedas what type of boiler?

1. Water tube2. Firebox3. Fire tube4. Bent tube

1-15. What advantage does the Scotchmarine boiler have over other boilersfor Seabee use?

1. Its shell does not requirereinforcing

2. Its furnace is fired from theoutside

3. It is portable4. It is easy to clean the surfaces of

the section below the combustionchamber

2

1-16. What condition is present when afusible plug in a Scotch marine boilerblows?

1. The water level in the boiler ishigh

2. The water level in the boiler is low3. The plug's tin is intact4. The plug is covered with water

1-17. Which of the following factors is adisadvantage of the vertical fire-tubeboiler?

1. It is not portable2. It is not self-contained3. It has a limited capacity4. It requires too much floor space

1-18. A vertical fire-tube boiler is similar toa

1. Scotch marine boiler2. horizontal fire-tube boiler3. straight-tube boiler4. bent-tube boiler

1-19. The blowdown pipe of a vertical fire-tube boiler is attached to the

1. top of the shell2. bottom tube sheet3. lowest part of the water leg4. outside row of tubes

1-20. When a stationary fire-tube boiler isrequired, the horizontal-return-tubetype is popular for which of thefollowing reasons?

1. It has a relatively low initial cost2. It is adaptable to a variety of fuels3. Its replacement tubes are of

uniform, size, length, and diameter4. Each of the above

1-21. What amount of pitch must ahorizontal return tubular boiler have toallow sediment to settle towards therear near the bottom blowdown?

1. 1 to 2 inches2. 2 to 3 inches3. 3 to 4 inches4. 4 to 5 inches

1-22. What means are used in boileroperation to ensure that enough air isavailable for proper combustion?

1. Chimneys2. Vents3. Breechings4. Draft fans

1-23. What boiler part must have a cross-sectional area 20 percent greater thanthat of the stack?

1. Breeching2. Settling3. Damper4. Combustion chamber

1-24. What are the two types of fusibleplugs?

1.

2.

3.4.

Steam-actuated and temperature-actuatedFire-actuated and temperature-actuatedSteam-actuated and water-actuatedFire-actuated and steam-actuated

1-25. What type of fusible plug can bereplaced without taking the boiler outof service?

1. Temperature-actuated2. Fire-actuated3. Steam-actuated4. Water-actuated

3

1-26. At what interval should fusible plugsbe replaced?

1. Monthly2. Quarterly3. Semiannually4. Annually

1-27. A water column is connected at least 6inches below the lowest permissiblewater level and at the top of the steamdrum for what purpose?

1. To bypass the gauge glass2. To indicate steam generation3. To control the high-water level4. To steady the gauge glass water

level

1-28. A boiler equipped with a float-operated feedwater control isprotected against damage resultingfrom what condition?

4.

1. Low-water level2. High-water level3. Closed fuel supply valve

Constantly operating feedwaterpump

1-29. Other than the low-water cutoff, whatoperation(s) is/are controlled by thefloat-operated feedwater control?

1. Operation of the feedwater pump2. Operation of the alarm bell3. Securing the burners4. All of the above

1-30. How many electrodes are contained inan electrode probe type of feedwatercontrol?

1. Five2. T w o3. Three4. Four

1-31. What device allows the boiler operatorto determine the water level in theboiler?

1. Gauge cocks2. Gauge glass3. Try cocks4. Site glass

1-32. What boiler fitting is considered themost important?

1. Air cock2. Feedwater regulator3. Safety valve4. Surface blow valve

1-33. What is the minimum number ofsafety valves required when a boilerhas more than 500 square feet ofheating surface?

1. Five2. T w o3. Three4. Four

4

1-34. What design feature is common in allboiler safety valves?

1. They must be suitable for any typeof installation

2. They must open and closeconstantly for long periods of time

3. They must open at a specifiedpressure and then close when thepressure drops slightly

4. They must open completely at aspecified pressure and close onlyafter a specified pressure drop

1-35. When should the lifting lever on asafety valve be used to check the valveaction and clear the seat?

1. As soon as steam pressure starts tobuild up within the boiler

2. When the pressure has reached 25psi within the boiler

3. When the pressure is at least equalto the safety valve setting

4. When the pressure within theboiler is at least 75 percent of thesafety valve setting

1-36. The injector feed system uses aninjector that serves both as a boilerfeeder and a

1. standby feed unit2. cooler sprinkler3. main steam stop valve4. system flusher

1-37. When a steam injector is started, thewater supply valve should be turned

1. a quarter of a turn2. a half a turn3. a full turn4. all the way open

1-38. For a steam injector to operateproperly, the water supply should notbe hotter than

1 .2 .

3 .4 .

120°140°160°180°

1-39. The root valve in the main steam lineserves what function?

1. To blow down a boiler2. To shut off steam in an emergency3. To connect a boiler to the auxiliary

steam line4. To allow air to enter and escape

the boiler

1-40. Floats are used in boiler instruments tocontrol the

1. pressure between inlet and outletpoints

2. incoming and outgoing flow ofwater

3. mixed flow of air and fuel4. mixed flow of water and steam

1-41. Of the following functions, which oneis NOT a function of a pressurecontrol?

1. To control the pressure in theboiler

2. To secure the fuel-burningequipment when pressure reaches apredetermined cutout

3. To control the flow of mixed waterand steam

4. To start the fuel-burningequipment when pressure drops tothe cut-in point

5

1-42. A modulating motor controls theoperation of the oil valve and the airshutters on a boiler to regulate the rateof firing. What factors causes themodulating motor to operate?

1.2.3.4.

Fuel oil pressureFeedwater regulatorPressure-regulating valveElectrical imbalance created bypressure change signals to thepressuretrol

1-43. The rate at which combustion air isdelivered can be changed by throttlingthe intake to the blower by opening orclosing the air damper.

1. True2. False

1-44.Normal atomizing pressures aregenerally within what range?

1. 75 to 85 psi2. 95 to 105 psi3. 95 to 120 psi4. 105t o120 psi

1-45. When the pilot flame is notestablished and confirmed, the flamefailure control must create a safetyshutdown within how many secondsafter lighting?

1. 15 seconds2. 10 seconds3. 7 seconds4. 4 seconds

1-46. What meter is used in controlling therelationship between air required andair actually supplied to bum the fuel ina boiler?

1. Draft meter2. Steam and air flowmeter3. Air analyzer4. Air pressure meter

1-47. A draft gauge is essential to boileroperation safety.

1. True2. False

for internally treating boiler water?1-48. What is the most widely used method

1 .2 .3 .4 .

Alkaloid-chlorine-tanninBenzene-hexcloride-tanninBorax-sulfate-tanninAlkaline-phosphate-tannin

1-49. Which of the following tests is NOTused to test boiler water?

1. Tannin2. Caustic alkalinity3. Sodium sulfide4. Phosphate

1-50. When performing a phosphate test,you should not use concentratedstannous chloride that is more than

1. 1 month old2. 2 months old3. 3 months old4. 6 months old

6

1-51.

1-52.

1-53.

When a phosphate test is beingperformed, which of the followingreadings would indicate a high level ofphosphate?

1. 70 ppm2. 60 ppm3. 50 ppm4. 40 ppm

You are collecting a boiler watersample for a caustic alkalinity testwithout tannin. The water temperatureshould be

1. 160°F or above2. 120°F or below3. 80°F or above4. 70°F or below

What test is run to determine thedegree of acidity in a boiler watersample?

1. Caustic alkalinity test with tannin2. Caustic alkalinity test without

tannin3. Sodium sulfite test4. pH test

1-54. The condensate pH normal acceptablerange is between

1. 6 and 6.52. 7 and 7.53. 8 and 8.54. 9 and 9.5

1-55. Of the following cleaning methods,which one is NOT a method ofcleaning boiler firesides?

1. Wet-steam lancing2. Sweating3. Cold-water washing4. Wire brush and scraper cleaning

1-56. The method used most often to cleansuperheaters and economizers is byhot-water washing.

1. True2. False

1-57. When performing wet-steam lancing,you should ensure the steam pressureis maintained between

1. 50 to 100 psig2. 60 to 120 psig3. 80 to 170 psig4. 70 to 150 psig

1-58. What cleaning method is used toremove fireside slag from theconvection superheaters?

1. Wet-steam lancing2. Sweating3. Hot-water washing4. Wire brush and scraper cleaning

1-59. What is the most common type of tubecleaner used to clean the watersides ofthe generating tubes?

1. Hydraulic turbine-driven2. Pneumatic turbine-driven3. Electric turbine-driven4. Hydropneumatic turbine-driven

1-60. Before cleaning boiler tubes, youshould ensure that there is

1.

2.

3.4.

7

varying size brushes for varyingsize tubesa checklist of all tubes requiringcleaningadequate ventilation and lightingno damage to the safety valves

1-61. Which of the following factors is NOTan advantage of using acid to clean aboiler?

1. Less outage time is required2. Less dismantling of the unit3. Performs a more through job4. Less safety equipment required

1-62. Which of the following types of acidis frequently used for cleaning boilers?

1. Citric2. Hydrochloric3. Sulfuric4. Phosphoric

1-63. What type of acid is used to removeboiler waterside deposits?

1. Citric2. Hydrochloric3. Phosphoric4. Sulfamic

1-64. When inhibitors are not added, acidsolutions attack boiler metal as readilyas they attack the deposits.

1. True2. False

1-65. Of the following chemical solutions,which one is NOT a neutralizingsolution?

1.2.3.4.

Soda ashTrisodium phosphateSulfite phosphateSodium tripolyphosphate

8

ASSIGNMENT 2

Textbook Assignment: "Boiler Maintenance," chapter 2, pages 2-1 through 2-30.

2-1. On a steam boiler, the headmechanism of the low water cutoffdevices should be removed from thebowl for cleaning at least once a

1. week2. month3. quarter4. year

2-2. When replacing a broken glass gauge 2-5. Which of the following types ofon a boiler, you should take what valves is NOT serviced andaction first? maintained by a Utilitiesman?

1.

2.

3.

4.

Close the upper and lower gaugeglass valvesRemove the packing nuts andpackingRemove all pieces of the brokenglassPreheat the replacement glass

2-3. What action should you take whenreplacing the gauge glass while theboiler is in service?

1.

2.

3.

4.

Heat the gauge glass to theoperating temperature of the boilerbefore installationClose the blowdown valve andgauge valves to prevent any loss ofsteam from the boilerCrack the gauge valves slightlyand slowly bring the glass tooperating temperatureClose the blowdown valve andopen the gauge valves quickly tobring the glass to operatingtemperature

2-4. The steam and water connections of afeedwater regulator should be blowndown separately at which of thefollowing intervals?

1. Weekly2. Monthly3. Quarterly4. Yearly

1. Gate type of stop valve2. Globe type of stop valve3. Stop-and-check valve4. Double-acting valve

2-6. In the care of valves, you shouldloosen and lift the packing at least

1 . quarterly2. monthly3. weekly4. daily

2-7. At what interval should you open theblowdown valves?

1. Daily2. Weekly3. Biweekly4. Monthly

9

2-8. At what interval should you test safetyvalves by raising steam pressure topopping pressure?

1. Semiannually2. Annually3. Monthly4. Quarterly

2-9. Lime deposits from a steam injectorcan be removed by placing the injectorinto a

1. tube of sulfuric acid for a minute2. tube with a mixture of baking soda

and water overnight3. tube of hot, soapy water overnight4. tube of muriatic acid for several

hours

2-10. At what interval should steam traps bedismantled and cleaned?

1. Monthly2. Quarterly3. Semiannually4. Annually

2-11. At what interval should you check theforced-draft fan to prevent dust fromaccumulating in or around the fan?

1. Monthly2. Every 2 weeks3. Weekly4. Daily

2-12. A new gasket should be installed in ahandhole fitting

2-13. Before installing a new gasket, youshould water-soak the gasket for whatperiod of time?

1. 24 hours2. 12 hours3. 6 hours4. 4 hours

2-14. When correctly centered, the clearancebetween the shoulder of the manholeplate and the manhole must not exceed

1. one-sixteenth of an inch2. one-eighth of an inch3. three-sixteenth of an inch4. one-quarter of an inch

2-15. What action should you take when theclearance between the manhole plateand the manhole exceeds therecommended clearance?

1. Use a different size gasket2. Replace the manhole plate3. Build up the manhole plate by

welding at the inner edge of theshoulder

4. Grind the manhole until therecommended clearance isachieved

2-16. The tension on a manhole gasket isrelieved by using

1. a wrench provided by the gasketmanufacturer

2. water pressure from a fire hose3. air pressure from a hose4. a hammer

4. once a month

1. each time the boiler is overhauled2. each time the handhole is opened3. when deposits on the seating

surface cause leaks

10

2-17. What precaution should you takebefore making a hydrostatic test of aboiler?

1. Close the air cocks2. Close the water gauges3. Gag the safety valves4. Close the pressure valves

2-18. You have filled a boiler with wateruntil the water discharges from the aircock. You then close the air cock andturn on the building water servicevalve. What minimum watertemperature must you maintain?

1. 50°F2. 60°F3. 70°F4. 80°F

2-19. You are hydrostatically testing aboiler with a maximum allowableworking pressure of 80 psi. Whatamount of pressure should you applyat each of the ten increments?

1. 12 psi2. 16 psi3. 80 psi4. 120 psi

2-20. What is the most pressure you shouldapply above the maximum workingpressure on a low-pressure boiler?

1. 5 pounds2. 2 pounds3. 10 pounds4. 15 pounds

2-21. What is the maximum allowablepressure drop during a hydrostatic testof a boiler over a 4-hour period?

1. 0.5%2. 1.0%3. 1.5%4. 2.0%

2-22. Which of the following methodsshould you use to test the safety valvesafter completing a hydrostatic test on aboiler?

1. Air pressure2. Steam pressure3. Water pressure4. Manual pressure

2-23. Of the following properties, which oneis NOT a property of a metal?

1. Porous2. Malleability3. Hardness4. Conductivity

2-24. Which of the following chemicalcompounds is an example of a metal?

1. Hydrogen sulfide2. Any alloy of steel3. Sodium chloride4. Carbon tetrachloride

2-25. Of the following dimensions, whichone is NOT a boiler tube identificationmarking?

1. Outside diameter2. Inside diameter3. Wall thickness4. Length

11

2-26. When a safety-ripping chisel is notavailable, you should take what actionto prepare the tube for removal?

1. Using a round nose chisel, split thetube through and beyond the sheet

2. Using a diamond nose chisel, splitthe end of the tube to the tubesheet

3. Using a square nose chisel, splitthe end tube and drive out the stub

4. Using a flat chisel, make two splitsabout three-fourths of an inchapart from the end of the tube tothe header

2-27. Before installing a new boiler tube, 2-31. When belling tubes that are 2 incheshow should you prepare the outside OD or larger, you should ensure theysurface of the tube end that will be are belled a minimum of 1/8 inch andexpanded in the tube sheet? a maximum of

1. Polish the tube end with abrasivepaper and then round off the tubeends with a file

2. Remove mill scale with a file andfile marks with an emery cloth

3. Polish the tube end with abrasivepaper and wipe with a kerosene-soaked rag

4. Square off the tube ends with atuning cutter and polish the tubewith a mild abrasive

2-28. Tubes that are 2 inches OD or largershould project into the drum or headerwhat distance?

1. Between 3/32 to 3/16 inch2. Between 5/16 to 7/16 inch3. Between 3/8 to 7/16 inch4. Between 7/16 to 15/32 inch

2-29. "Boilerman's feet" are used to expandtubes that measure

1. smaller than 1 inch2. from 1 to 2 inches3. from 2 to 3 inches4. from 3 to 4 inches

2-30. In expanding tubes, you should selectexpanders for the tube size and

1. thickness of the tubes2. type of tube sheet3. thickness of the seat4. the expansion factor

1. 1/2 inch2. 5/16 inch3. 1/4 inch4. 3/16 inch

2-32. When boiler tubes are leaking, youshould use which of the followingmethods to accomplish an emergencyrepair?

1. Re-expand the tube2. Remove the tube ends and weld

the tube sheet closed3. Weld the end closed4. Plug the tube ends

12

2-33. When plugging sidewall tubes, youshould never plug more than whattotal number of tubes next to eachother?

1. 52. 23. 34. 4

2-34. What material should you use to plug

2-37. What is the maximum thicknessallowed for joints between firebricksin a boiler?

1. 1/8 inch2. 5/16 inch3. 1/16 inch4. 3/16 inch

2-38. The joints between firebricks arebeaded with mortar for which of the

up a case opening? following reasons?

1. Asbestos packing2. Plastic refractory3. Firebrick mortar4. Navy-approved sealing compound

2-35. When an economizer elementdevelops a leak, you should insert aplug at what location?

1. To prevent turbulence in theburner flame

2. To compensate for shrinkage ofthe mortar as it dries

3. To protect the comers of thefirebrick

4. To bond the mortar to the adjacentbrickwork

1. At the superheater tube bank and 2-39. What material should you use to makethe superheater screen emergency repairs to the cracks in the

2. At the sidewall heater and the furnace lining?steam drum

3. At the tube sheet and the rear wall 1. Plastic firebricktubes 2. Plastic chrome ore

4. At the inlet header and the outlet 3. Grade A firebrickheader 4. Fire clay

2-36. You are replacing refractory brick in a 2-40. You are repairing a refractory brickfurnace. To prevent air bubbles from wall and have rammed a piece offorming, you should place the mortar plastic into place so it fits tightly.on the wet brick in what manner? What action do you take next?

1. By using an edgewise motion todip one end and a side of the brickinto the mortar

2. By using a trowel to place themortar on the wet brick surface

3. By placing the mortar in the spaceto be occupied by the brick beforethe brick is set in

4. By dipping both ends and a side ofthe brick into the mortar

1. Trowel the surface2. Apply anchor bolts to hold the

plastic in place3. Vent the plastic section with 3/16-

inch holes, 2 inches apart4. Build a small fire to bake out the

plastic

13

2-41. What temperature is required to bakeout plastic refractory?

1. 1000°F to 1200°F2. 1500°F to 1700°F3. 2000°F to 2200°F4. 2900°F to 3000°F

2-42. You should NOT use high-temperature bonding and an air-drytype of mortar, diluted with water tothe consistency of light cream, forpatching when bricks fall out.

1. True2. False

2-43. After removing all the old refractoryand foreign material, you shouldinspect the furnace metal for which ofthe following conditions?

1. Soundness2. Tightness3. Corrugation4. Heat cracks

2-44. Before installing tiles, you should takewhat action?

1. Preheat the tiles2. Wash the tiles3. Dry fit and match mark the tiles4. Coat the sealing area with an

insulating pulp cement

2-45. It is normal for refractories exposed tohot gases to develop thin, hairlinecracks. What size does a crack have tobe before you clean and fill it withhigh-temperature bonding mortar?

1. Between 1/16 to 1/8 inch2. Between 1/8 to 1/4 inch3. Between 1/4 to 3/8 inch4. Between 3/8 to 1/2 inch

2-46. After inspecting the door head gasket,you should coat the gasket with whichof the following types of mixtures?

1. Gasket cement mix2. Vee block mixture3. Wash coat mixture4. Oil and graphite mixture

2-47. When replacing the door gasket, youshould use what size rope gasket?

1. 1 1/4 inches2. 1 1/2 inches3. 1 3/4 inches4. 2 1/4 inches

2-48. There are seven major phases in theoperation of a boiler.

1. True2. False

2-49. Which of the following actions isNOT required by a oncoming watchstander?

1. Test the water columns and gauges2. Inspect the fans, damper, and

damper drives3. Test fire the furnace4. Visually inspect the setting and

casting

14

2-50.

2-51.

2-52.

Immediately after accepting theoperational responsibility for a boiler,you should make a completeinspection of all auxiliary equipment.

1. True2. False

Which of the following tasks shouldyou complete before lining up aboiler?

1. Remove excess water from the gastank

2. Check for fuel leaks3. Measure the amount of fuel oil

with a stick or gauge4. Check the fuel oil pressure

Which of the following tasks is NOTperformed when lining up a gas-firedunit?

1. Open the main gas cock2. Check the draft devices3. Purge air out of the gas lines by

external vents4. Close the control valves and safety

shutouts

2-53. Before a boiler is lighted off, which ofthe following valves must be opened?

1. Feedwater drain2. Feedwater stop and check3. Burner fuel4. Main steam stop

2-54.

2-55.

2-56.

You are filling a newly repaired boilerwith treated water and the temperatureof the pressure parts is 40°F. What isthe maximum allowable temperaturefor the fill water?

1. 50°F2. 60°F3. 7 5 ° F4. 90°F

You have just fired off a newlyrepaired boiler. The temperatureshould be raised what number ofdegrees per hour until operatingpressure is reached?

1 50°F2. 100°F3. 150°F4. 200°F

Before cutting in the boiler, youshould open all drain lines between theboiler and the header.

1. True2. False

15

2-57. What are the major duties of a boileroperator during normal boileroperation?

1. To ensure the water level is nottoo high or too low

2. To maintain a safe and efficientcombustion condition in thefurnace and to correct fuel-airratios

3. To keep the correct water leveland prevent the loss of ignition

4. To see and interpret prevailingoperating conditions and takeaction to control, modify, orcorrect them

2-58. When securing a boiler, you shouldrelieve the boiler pressure at the

1.2.

3.4.

safety valvessuperheater drain and nonreturnvalvesbottom blowdown valvesmain steam stop bypass valves

2-59. Before water can be drained, the watermust be below what temperature?

1. 250°F2. 225°F3. 212°F4. 200°F

2-60. Of the following situations, which oneis NOT an emergency during boileroperations?

1. Broken gauge glass on the watercolumn

2. Flarebacks caused by an explosionin the combustion chamber

3. Tube failure making it impossibleto maintain water level

4. Flue-gas temperature above 150degrees higher than thetemperature of the steam produced

2-61. At what time intervals should entriesbe made in the boiler room operatinglog?

1. Hourly2. Every 8 hours3. Every 12 hours4. Every 24 hours

2-62. While on boiler watch, you notice thatthe last-pass draft reading hasincreased with each log entry. This isan indication of the

2-63.

1. amount of air being supplied isincorrect

2. gas passages becoming clogged3. baffles leaking4. draft fan not operating at the

correct speed

Abnormally high flue gas temperaturecan be caused by dirty heating surfacesor by leaking baffles.

1. True2. False

16

2-64. You should record the outsidetemperature in the boiler roomoperating log for a comparison with

1. steam generated and fuel used2. water pressure and makeup water3. fuel used and makeup water4. steam generated and water

pressure

2-65. The economy in a steam flowmeter isobtained by

1.

2.

3.

4.

dividing fuel burned by steamgenerateddividing cost of steam by cost offueldividing steam generated by fuelburned

1 .2 .3 .4 .

1.5 to 3.03.5 to 9.5

10.0 to 14.515.5 to 30.0

dividing cost of fuel by steamgenerated

2-66. At what time intervals should youcheck the boiler settings for externalair leaks?

1. Every 8 hours2. Every 12 hours3. Every 18 hours4. Every 24 hours

2-67. Before entering a boiler to makerepairs, you should attach a sign thatreads

1. DANGER2. KEEP OUT3. CAUTION-MAN WORKING

INSIDE4. CLOSED DOOR

2-68.

2-69.

2-70.

2-71.

Fuel-oil suction and dischargestrainers should be cleaned at whattime interval?

1. Every 8 hours2. Every 12 hours3. Every 16 hours4. Every 24 hours

When checking flame conditions onan operating boiler, you should usewhat shade of colored lens in yoursafety goggles?

If the water goes out of sight in thebottom of the gauge glass, you shouldNOT take which of the followingactions?

1.

2.

3.

4.

Drain the boiler completely andopen it for inspectionClose the steam stop valveimmediatelyFeed cold water to the boiler withlow water until it has cooledKill the fire the quickest waypossible

Handles on pull chains to boiler water-gauge cocks and water gate valves forthe top gauge cock should be paintedwhat color at shore installations?

1. Green2. Blue3. Yellow4. Whi te

17

2-72. A valve must be fitted with a newspring and restamped by themanufacturer for changes that exceedswhat percentage?

1. 20%2. 15%3. 10%4. 5%

2-73. A lockout device is a mechanism orarrangement that allows the use of akey or combination locks to hold aswitch lever or valve handle in eitherthe ON or OFF position.

1. True2. False

2-74. The use of what lockout deviceenables more than one person toaccomplish hazardous work on a pieceof equipment at the same time?

1. Multiple lock adapter2. Master combination lock3. Multiple keyed padlock4. Duplicate key

2-75. Locks should identify the user by

1. name, rank, and serial number2. color code of rating, name, and

serial number3. name, rate, and shop4. color code of rating, name, and

shop

18

ASSIGNMENT 3

Textbook Assignment: "Steam Distribution Systems" and "Heating Systems," chapters 3 and 4,pages 3-1 through 4-4.

3-1. What are the two types of steamdistribution systems?

1. Interior and exterior2. Automatic and manual3. Electric and hydraulic4. Pneumatic and manual

3-2. What are the two types of majorunderground steam distributionsystems?

1. Conduit and interior2. Utilidor and conduit3. Interior and utilidor4. Network and conduit

3-3. The conduit of a conduit type of steamdistribution system is constructed ofwhat type of material?

1. Galvanized steel2. Masonry cement3. Br ick4. Cast iron

3-4. What factors determine the size andshape of a utilidor?

1. Number of manholes and the typeof pipe hangers to be used

2. Type of insulation and theimposed loads

3. Number of distribution pipes andthe depth into the ground

4. Materials to be used inconstruction and the provision forpipe expansion

3-5. What is the primary disadvantage ofusing an overhead steam distributionsystem?

1. It has a high maintenance cost2. It requires an expansion joint3. The type of material required for

the steam return piping4. Water collects and seeps through

the sealer at the openings

3-6. Of the following factors, which one isNOT considered when classifyinginterior steam distribution systems?

1. Pipe arrangement2. Accessories used3. Type of controls used4. Size and type of boiler

3-7. What is the function of the air valve ina gravity, one-pipe, air-vent system?

1. It vents air from the radiators2. It shuts off the radiators3. It turns on the radiators4. It vents condensate from the

radiators

3-8. Water hammer and slow heating arecharacteristics of a gravity, one-pipe,air-vent system when the pipe sizing,pitch, and general design areinadequate.

1. True2. False

19

3-9. Water hammer in a gravity, one-pipe,air-vent system can be controlled by

1. venting air from the radiators2. ensuring that condensate and

steam flow in the same direction3. providing enough hydrostatic head

above the entrance to the boiler4. ensuring condensate is properly

drained from the lines

3-10. To obtain the necessary internaldrainage when installing a gravity,one-pipe, air-vent system, you shouldslope the lines down at least

1. one-fourth of an inch for every 10 1. Airfeet of pipe 2. Condensate

2. one-fourth of an inch for every 20 3. Thermostaticfeet of pipe 4. Boiler pressure return

3. one-eighth of an inch for every 20feet of pipe

4. one-eighth of an inch for every 10feet of pipe

3-11. What is the purpose of the main steamstop valve in most steam systems?

1. To hold condensate in the boileruntil it is released

2. To hold steam in the boiler until itis released

3. To ensure the proper water level ismaintained

4. To drain water from the radiator

3-12. When opening the main steam stopvalve, you should

1. crack the valve open2. open the valve one-quarter of a

turn3. open the valve one-half of a turn4. open the valve one full turn

3-13. When a radiator fails to heat ordevelops water hammer, which of thefollowing malfunctions is NOT aprobable cause?

1. Failure of the air vents to operate2. Radiator valves not fully opened3. Radiator and line incorrectly

pitched4. Excessive pressure drop in the

supply lines

3-14. In a two-pipe vapor system, what trappermits the flow of condensate and airfrom the radiator?

3-15. In the two-pipe vapor system, thebottom of the trap should be installedhow many inches above the boilerwaterline?

3-16.

1. 122. 183. 244. 3 6

In a two-pipe vapor system with acondensate pump and the wholesystem fails to heat, which of thefollowing malfunctions may NOT bethe cause of the trouble?

1. Clogged receiver vents2. Flooded return line3. Air binding the system4. Inoperative steam trap

20

3-17. In the two-pipe vapor distributionsystem, what component returns thecondensate to the boiler and maintainsthe vacuum or subatmosphericpressure in the return system?

1. Thermostatic trap2. Float switch3. Vacuum pump4. Condensate pump unit

3-18. You should only use the float switchin which of the following situations?

1. To remove excess condensatefrom the thermostatic trap

2. When the vacuum switch isdefective

3. To eliminate air leakage4. When the system fails to heat

3-19. What are the two categories of steamradiators?

1. Wall and floor2. Fin tube and cast iron3. One tube and two tube4. Sectional and integral

3-20. What are the two types of radiator airvents?

1. Wall and floor2. Sectional and integral3. Automatic and manual4. Electrical and hydraulic

3-21. The hermetically sealed bellows of anair vent contains a volatile liquid thathas a boiling point that is how muchlower than that of water?

1. 20°F2. 15°F3. 10°F4. 5°F

reasons?

3-22. A steam trap is installed in a steamline for which of the following

1.

2.

3.

4.

To allow steam to escape from thelineTo prevent the escape of steamfrom a using deviceTo keep foreign particles frompassing through the lineTo drain condensate from the drainline without allowing steam topass through it

3-23. Of the following types of traps, whichone is NOT a steam trap?

1. Float2. Ball-float3. Thermodynamic4. Thermostatic impulse

depends on what condition?3-24. The operation of a bucket trap

1. Difference in temperature betweenthe steam and the condensate

2. Difference in the density betweenthe steam and the condensate

3. Buoyancy of the bucket4. Mixture of air and condensate in

the trap

3-25. What type of steam trap is often usedon radiators and is commonly knownas a "radiator trap"?

1. Bucket2. Thermostatic3. Float4. Impulse

21

3-26. What component of the floatthermostatic trap activates thedischarge valve?

1. Thermostatic vent2. Cooling leg3. Ball float4. Bellows

3-27. The design of what type of steam trapis based on the principle that a volumeof hot water that is under pressure willflash into steam when the pressure isreduced?

1.I m p u l s e2.Thermodynamic3.Throttl ing4.Bimetallic-element

3-28. The pressure on the discharge side ofthe trap should NOT exceed whatpercentage of the inlet pressure toensure that an impulse trap operatesproperly?

1. 5 percent2. 1 0 percent3. 20 percent4. 25 percent

3-29. A thermodynamic trap is usuallyconstructed from what type ofmaterial?

1. Cast iron2. Stainless steel3. Malleable steel4. Aluminum

3-30. The bimetallic-element trap worksbasically the same as what other typeof trap?

1. Float2. Thermostatic3. Impulse4. Thermodynamic

3-31. When a test plug is not available onthe top of the trap, you can prime aninverted bucket trap by

1. blowing down the trap2. allowing the discharge from

another trap to backup into the trap3. closing the discharge valve and

opening the steam supply valveslowly until the trap is filled withcondensate

4. opening the discharge and steamsupply valves until the trap isfilled with condensate

3-32. When the test valve method for testingsteam traps is used, a continuoussteam blow indicates which of thefollowing malfunctions?

1. Loss of prime2. No condensate is passing3. Considerable rattling4. Slight temperature difference

3-33. You test a steam trap by listening withan engineer's stethoscope held incontact with the body of the trap.What should you hear if the trap isworking properly?

1. Faint hissing sound2. Regular opening and closing of the

trap valve3. Continuous flow of steam4. Rattling sound

22

3-34. What type of tank helps to eliminatedisturbances caused in piping systemsby violent steam formation?

1. Flash2. Storage3. Surge4. Supply

3-35. What are the two general types ofwater heaters?

1. Flash and surge2. Floor and instantaneous3. Surge and storage4. Storage and instantaneous

3-36.According to safety regulations, thewater inside a storage type of hot-water heater should not exceed

1. 212°F2. 195°F3. 180°F4. 165°F

3-37. To ensure that steam is not leakinginto the water, you inspect the coil

1. every 2 years2. annually3. semiannually4. quarterly

3-38. The operation of the instantaneoustype heater and the storage type ofheater are basically the same.

1. True2. False

3-39.

3-40.

3-41.

3-42.

Of the following types, which one isNOT a type of expansion joint?

1. Bellows joint2. Slip joint3. Ball loop4. Expansion loop

What type of expansion joint is mostoften used to allow expansion to occurnaturally in a system that has screwedjoints?

1. S l i p2. S w i n g3. Bellow4. B a l l

You should lubricate slip joints atwhat interval?

1. Monthly2. Quarterly3. Semiannually4. Annually

You should inspect slip joints forsigns of erosion, corrosion, wear,deposits, and binding at what interval?

1. Monthly2. Quarterly3. Semiannually4. Annually

3-43. The measurement of heat intensity indegrees Fahrenheit (F) or Celsius (C)is know by what term?

1. Sensible heat2. Temperature3. Latent heat4. Total heat

23

3-44. What type of heat does thethermometer measure?

1. Sensible2. Latent3. Specific4. Tota l

3-45. On the Fahrenheit thermometer whatis the range between freezing andboiling?

1. 100°2. 128°3. 150°4. 180°

3-46. On the Celsius thermometer, what isthe range from freezing to boiling?

1. 100°2. 128°3. 150°4. 180°

3-47. When the temperature is 95°F, what isthe Celsius equivalent?

1. 25°C2. 3 0 ° C3. 3 3 ° C4. 3 5 ° C

3-48. When the temperature is 25°C what isthe Fahrenheit equivalent?

1. 20°F2. 32°F3. 44°F4. 77°F

3-49. A British thermal unit is the amount ofheat required to change thetemperature of 1 pound of pure water1°F at sea level.

1. True2. False

3-50. A block of ice at 32°F melts into waterat the same temperature. What form ofheat was required to produce thischange of state?

1. Latent2. Intense3. Specific4. Thermal

3-51. The amount of heat added to asubstance above its boiling point is thedefinition of what term?

1. Superheat2. Sensible heat3. Specific heat4. Latent heat

3-52. Sensible heat plus latent heat equalswhat type of heat?

1. Measurable2. Intense3. Total4. Superheat

3-53. Absolute zero is what temperature onthe Celsius scale?

1. -10°C2 . -32°C3. -238°C4. -320°C

24

3-54. In what direction does heat flow?

1. Clockwise2. Counterclockwise3. From a warmer to a cooler

substance4. From a cooler to a warmer

substance

3-55. What condition must be present forheat to flow?

1. Space to heat2. Substance to heat3. Difference in pressure4. Difference in temperature

3-56. When one end of a stove poker is heldin a flame, the other end soonbecomes too hot to handle. Whatmethod of heating has been used?

1. Convection2. Conduction3. Radiation4. Diffusion

3-57. The transfer of heat by means ofmedia, such as water, air, and steam,defines

1. convection2. conduction3. radiation4. diffusion

3-59. What type of material is the bestknown reflector?

1. Black clothing2. White clothing3. Dull metal4. Polished metal

3-60. Gaseous fuels are usually classifiedaccording to what factor?

1. Abundance2. Use3. Source4. Cost

3-61. Natural gas has which of the followingcharacteristics?

1. It is odorless and colorless2. It has a distinctive odor3. It has a distinctive color4. It is replete with ash

3-62. Of the following types of gas, whichone is NOT a type of manufacturedgas?

1. Methane2. Carbureted water3. Oil4. Producer

3-63. What is the major element inmanufactured gases?

3-58. A hand held in front of a stove is 1. Methanewarmed by what means?

1. Convection2. Conduction3 . Radiation4. Diffusion

2. Ethane3. Hydrogen4. Oxygen

25

3-64. Propane boils at what temperature?

1. -44°F2. -54°F3. -62°F4. -70°F

3-65. Butane vaporizes at what temperature?

1. 60°F2. 54°F3. 32°F4. 25°F

26

ASSIGNMENT 4

Textbook Assignment: "Heating Systems" (continued), chapter 4, pages 4-4 through 4-36.

4-1. An installed equipment item and acomponent of a system, consisting ofan extended or finned heat transfersurface, and a propeller or blower fanto create an airflow through it isknown as what type of heating unit?

1. Central heater2. Central heating system3. Unit heating system4. Unit heater

4-2. What type of direct-fired unitgenerates heat directly by an electricalcoil or by a combustible fuel?

1. Space heater2. Central heater3. Space distribution heater4. Unit heating system

4-3. Of the following types of heaters,which one is NOT a type of unitheater?

4-5. One kilowatt equals a total of howmany Btu per hour?

1. 3,4152. 2,7753. 2,2254. 1,775

4-6. Electric space heaters are operatedmanually with an ON-OFF switch orautomatically with a

1. humidstat2. thermostat3. rheostat4. flurostat

4-7. What are the two types of gas heaters?

1. Butane and propane2. Manual and automatic3. Direct fired and indirect fired4. Vented and unvented

1. Suspended horizontal discharge2. Suspended vertical discharge

Vertical forced warm-air4. Horizontal type of blower unit3.

4-4. Space heaters are desirable as a meansof providing heat to a small spacebecause of their simplicity ofconstruction, low initial cost, andreasonable fuel consumption.

4-8. A vented gas heater is preferred overan unvented heater because

1.

2.

3.

4.

the flame burns in a opencombustion chamberthe flame bums in the lowerportion of the burnerthere is less danger of carbonmonoxide poisoningthere is less danger of explosion

1. True2. False

27

4-9. Unvented gas heaters should be used 4-14. What is the only safety device on anin well-ventilated areas to oil-fired space heater?

1. remove sulfur deposits2. remove carbon monoxide

produced by the gas flame3. comply with the American Gas

Association (AGA) requirements4. comply with the NAVFAC DM3

4-10. Approximately how many gallons ofwater is produced when 1,000 cubicfeet of natural gas is burned?

1. 423. 124.

8

16

4-11. Horizontal flue pipes for vented gasheaters should have an upward pitchof at least how many inches per foot?

1. 12. 23. 34. 4

4-12. Oil is fed to a natural draft pot 4-17. Which of the following conditionsdistillate burner that is located at the may result in poorly working burners?

1. top of the burner, at the center2. bottom of the burner, either at the

center or on the sides3. end of the perforated sleeves4. middle of the left side of the

burner

4-13. The flame in a perforated sleeveburner should be what color?

1. Atmospheric vaporizing type ofburner

2.Safetronic diffuser3.Fuel level control valve4.Draft diverter

4-15. The draft produced by a chimneydepends upon the height of thechimney and what other factor?

1. Width of the chimney2. Temperature of the flue gas3. Temperature of the outside air4. Difference between the flue gas

and the outside air

4-16. On what two factors does theoperation of the draft regulatordepend?

1. Balance and free action2. Balance and counterbalance3. Downdraft and updraft4. Updraft and free action

1. Chimney that is too high above theroof lineChimney that is not high enough2.above the roof line

3. Face of the damper is not plumb4. Counterweight placed on the

damper

1. Blue2. Yellow3. Green4. R e d

28

4-18. What is the major advantage of usingcopper tubing with heat installations?

1. It is not affected by heat2. It is maintenance free3. It requires fewer fittings4. It eliminates the need for a tubing

bender

4-19. The burner goes out on a perforatedsleeve burner. Which of the followingconditions is NOT a probable cause?

1. Insufficient oil flow2. Struck needle valve3. Oil valve not level4. Improper fuel

4-20. A gas-fired space heater has ahumming sound in the solenoid. Whatcondition is the most probable cause?

1. Incorrect gas pressure2. Malfunctioning limit switch3. Incorrect current4. Solenoid installed backwards

4-21. What are the two types of warm-airheating systems?

1. Gravity and forced-air2. Positive and negative3. Automatic and semiautomatic4. Central and dispersed

4-22. What is the most common problemwith a gravity type of warm-air systemwhen installed at floor level?

1.

2.

3.4.

Heat insulation needed above thefurnace topReturn-air opening is too small atthe floorLack of a positive-pressure fanUndersized jacket at the floor

4-23. What component installed in theforced warm-air system allows forsmaller ducts?

1. Return-air jacket2. Humidifier3. Positive pressure fan4. Negative pressure fan

4-24. What component of a forced warm-airsystem joins the main truck duct?

1. Duct extension2. Sloping duct3. Blower4. Plenum

4-25. An objectionable noise will result atsupply diffusers when room airvelocities exceed 25 to 35 feet perminute (fpm).

1. True2. False

4-26. What type of distribution is providedby a diffuser that discharges through awall?

1. Horizontal2. Vertical3. Lateral4. Cross wind

4-27. What are the two types of duct layout?

1. Warm air and cold air2. Plenum and full3. Individual or trunk and branch4. Vertical and horizontal

29

4-28. Warm-air pipes are called "leaders."

1. True2. False

what register temperature range?4-29. Forced warm-air svstems usuallv have

4. 180°F to 210°F

1. 100°F to2. 125°F to3. 150°F to

125°F150°F180°F

4-30. Outlet velocities of forced warm-airsystems at registers may be as high as

1. 350 fpm2. 400 fpm3. 450 fpm4. 500 fpm

4-31. What are the three compartments in agas-fired furnace?

1. Return air, combustion enclosure,and fuel compartments

2. Blower, filter, and warm-aircompartments

3. Return air, warm-air, and thecombustion and fuel compartments

4. Blower, heat exchanger radiator,and combustion air compartments

4-32. The compartments and assemblies of agas-fired furnace may be broken downinto a total of how many units?

4-33. What assembly includes the gasvalves, pressure regulator, and thoseparts that automatically control theflow of gas to the pilot and mainburner?

1. Blower2. Furnace casing3. Burner4. Gas manifold

4-34. What type of burner is usually usedwith a gas-fired furnace?

1. Hillary2. Thompson3. Bunsen4. Taylor

4-35. What gas burner control should beinstalled first?

1. Gas pressure regulator2. Manual gas cock or valve3. Pilot light4. Thermocouple relay

4-36. What type of gas pressure regulator isgenerally used in a domestic gas-heating system?

1. Spring controlled2. Diaphragm3. Solenoid4. Vacuum

1. Five2. S i x3. Three4. Four

30

4-37. What condition causes the pressureregulator to close?

1. Burner pressure falls below thedesired amount

2. Supply pressure is set above thedesired amount

3. Burner pressure is set above thedesired amount

4. Supply pressure falls below thedesired amount

4-38. The adjusting screw for setting thepressure regulator is at what location?

1. On the bottom of the regulator2. On the side of the regulator3. On the top of the regulator4. On the lead-in to the regulator

4-39. What design feature distinguishes therecycling solenoid gas valve from astandard solenoid gas valve?

1.2.3.4.

Manual recycling switchRecycling diverterRecycling valveAutomatic recycling device

4-40. The primary feature of the diaphragmvalve is the extreme valve noise madewhen opening or closing.

1. True2. False

4-41. What component of a gas-firedfurnace produces an electric currentwhen it is hot?

4-42. In the automatic gas burner system,the thermocouple is installed next tothe

1. diaphragm valve2. pressure regulator3. pilot light4. conversion burner

4-43. What unit shuts off the gas when thetemperature inside the heating unitbecomes excessive?

1. Thermocouple control relay2. Thermocouple3. Diaphragm valve4. Limit control

4-44. What unit reduces downdrafts andupdrafts that interfere with pilot andburner operation?

1. Draft diverter2. Draft subverter3. Draft converter4. Draft inverter

4-45. What are the three compartments of anoil-fired furnace?

1.

2.

3.

4.

Burner, combustion and radiating,and blowerCombustion, radiating and burner,and blowerBlower, combustion and burner,and radiatingRadiating, blower and burner, andcombustion

1. Thermocouple2. Resistor3. Rheostat4. Conductor

31

4-46.

4-47.

4-48.

4-49.

What type of pressure is used toatomize the oil in a gun type ofdomestic oil-burner?

1. Electrical2. Differential3. Pneumatic4. Fuel oil

What is the usual oil pressure for thedomestic oil burner?

1. 75 psi2. 100 psi3. 125 psi4. 150 psi

What is the most common type of fuelunit used for oil burners?

1. Y-type, two stage2. W-type, two stage3. T-type, two stage4. L-type, two stage

An electric transformer is required tostep up line voltage to approximately10,000 volts to cause a spark to jumpbetween the ignition electrodes.

1. True2. False

4-50. What is the speed of the atomizingcup in the horizontal rotary type ofburner?

1. 2,350 rpm2. 3,450 rpm3. 4,530 rpm4. 5,430 rpm

4-51. What is the purpose of the oil burnercontrol system?

3. To start the burner as needed4. To provide an electrical

connection between the thermostatand the burner

2. To maintain the desired roomtemperature

1. To provide automatic, safe, andconvenient operation

4-52. Of the following controls, which onecontrols the operation of the fire so thetemperature and pressure of theheating plant never exceed safeoperating limits?

1. Primary2. Limit3. Fan4. Thermostat

4-53. The human hairs in a humidity-responsive device reacts to differencesin

4. ambient temperature

1. pressure2. heat3. humidity

4-54. What action in the snap-action switchprevents excessive arcing across thepoints?

1. Closing only2. Opening only3. Slow opening and closing4. Fast opening and closing

32

4-55. Every electric switch is designed so ithas a specific rated capacity in

1. ohms and coulombs2. coulombs and amperes3. amperes and volts4. volts and coulombs

4-56. The standard controls furnished forautomatic fuel-burning equipmentcome in sets designed for warm-air,hot-water, and steam-heating systems.

1. True2. False

4-57. What is the nerve center of the heatingcontrol system?

1. Humidstat2. Thermostat3. Essostat4. Ergostat

4-58. What types of thermostats are usedmost often in heating control systems?

1. Mercury bulb and electric clock2. Electric clock and spiral bimetallic3. Programmable and electric clock4. Spiral bimetallic and mercury bulb

4-59. The best location for a thermostat ison an inside wall and approximatelyhow many feet from floor level?

1. 1 1/22. 2 1/23. 3 1/24. 4 1/2

4-60. To check the calibration of athermostat, you should allow whatamount of time for the thermostat anda test thermometer to adjustthemselves to room temperature?

4-61.

1. 5 to 10 minutes2. 10 to 15 minutes3. 15 to 30 minutes4. 30 to 45 minutes

You do not have to recalibrate athermostat if its closing point does notexceed that of the test thermometer by1°F.

1. True2. False

4-62. When installing a furnace, you shoulduse what tool to ensure that it is level?

1. Float level2. Spirit level3. Dumpy level4. Locke level

4-63. Gas-fired and oil-fired forced air unitswith the blower below the heatingelement should be setting on masonryat least 3 inches thick and extendingwhat minimum distance beyond thecasing wall?

1. 6 inches23.

9 inches12 inches

4. 18 inches

33

4-64. When ventilating the furnace room tosupply air for combustion, you shouldallow what size opening for each1,000 Btu per hour of furnace inputrating?

1. 1 square inch2. 2 square inches3. 3 square inches4. 4 square inches

4-65. To ventilate a furnace roomadequately, you should install whattotal number of louvered openings?

1. One2. Two3. Three4. Four

4-66. You should use what size and type oftubing from the oil tank or valve to theburner?

1. 1/8-inch copper2. 1/4-inch copper3. 3/8-inch seamless steel4. 1/2-inch seamless steel

4-67. The suction and return lines for anunderground fuel tank should beconstructed of

1. black iron2. P V C3. copper tubing4. seamless steel

4-68. Which of the following physicalconditions does NOT have to beattained to ensure complete andefficient combustion of fuel-oilsystems?

1. The mist must be thoroughlymixed with sufficient combustionair

2. The liquid must be thoroughlyvaporized

3. Flame propagation temperaturemust be maintained

4. Primary combustion air must beadmitted to the furnace through thecasing surrounding the burner

4-69. Atomization of fuel oil is notaccomplished by

1.

2.

3.

4.

using steam to break the oil intodropletsforcing oil under pressure througha suitable nozzlepassing an oil film through anannular groove and into a nozzlespray tiptearing an oil film into tiny dropsthrough centrifugal force

4-70. Steam-atomizing and air-atomizingburner nozzles are both classified aswhat type of nozzle?

1. Internal or external mixing2. Centrifugal or centripetal3. Static or dynamic4. Open or closed

34

4-71.

4-72.

What is the required pressure rangefor the steam in a steam-atomizingburner?

4-74. Which of the following types ofburners atomizes fuel by tearing it intotiny droplets?

1. 75 to 150 psi 1. Steam atomizing2. 65 to 90 psi 2. Air atomizing3. 55 to 80 psi 3. Mechanical atomizing4. 45 to 70 psi 4. Horizontal rotary-cup

What amount of air pressure isrequired to carry light oil to the burnertip of an air-atomizing burner?

4-75. What is the speed of a motor-drivenconical or cylindrical cup in ahorizontal rotary-cup burner?

1. 10 psi2. 15 psi3. 20 psi4. 25 psi

1. 2,450 rpm2. 3,450 rpm3. 4,450 rpm4. 4,850 rpm

4-73. In a mechanical atomizing burner,good atomizing results at whatpressure?

1. 100 psi2. 200 psi3. 300 psi4. 400 psi

35

ASSIGNMENT 5

Textbook Assignment: "Heating Systems," chapter 4, pages 4-36 through 4-51.

5-1. Before trying to start or service oilburners, you should take what action?

1. Obtain a pressure gauge2. Locate a full set of Allen setscrew

wrenches3. Order a complete set of socket

wrenches4. Ensure the correct maintenance

equipment is available

5-2. When performing oil burnermaintenance, you should use whattype of pipe dope?

1. Oil line2. Graphite3. Graphite cord4. SAE 10

5-3. Which of the following materialsshould you use to clean the grease andgum out of an oil burner nozzle?

1. Diesel2. Gasoline3. Kerosene4. Warm soapy water

5-4. When installing an oil burner nozzleafter cleaning, you should set theelectrodes

1. 5/8 inch apart, 1/8 inch ahead ofthe nozzle, and 1/2 inch above thenozzle center line

2. 1/2 inch apart, 1/4 inch ahead ofthe nozzle, and 5/8 inch above thenozzle center line

3. 1/8 inch apart, 5/8 inch ahead ofthe nozzle, and 3/8 inch above thenozzle center line

4. According to the specific settingsin the manufacturer's manual

5-5. After reinstalling an oil burner pump,you should take what action whenthere is evidence of end pressure?

1. Loosen the coupling and move itaway from the pump

2. Loosen the coupling and move itcloser to the pump

3. Loosen the pump and move itcloser to the coupling

4. Loosen the pump and move itaway from the coupling

5-6. After visually adjusting the burner,you should allow it to run for whatlength of time?

1. 10 minutes2. 20 minutes3. 30 minutes4. 40 minutes

36

5-7. Which of the following faults is NOT 5-12. What device should you use tolikely to be caused by too little draft in determine the percentage of CO2

an oil burner? produced by combustion?

1. Firebox pressure2. Odors in the building3. Smoke4. Flame flare-up

5-8. When the burner and draft areadjusted correctly, a flue-gas analysisshould indicate what percentage ofCO2?

1. 10 percent2. 15 percent3. 20 percent4. 30 percent

should be the maximum stacktemperature?

5-9. When the furnace is large enough andthe burner is set for correct oil flowwith minimum amount of air, what

1. 500°F2. 600°F3. 700°F4. 800°F

5-10. What type of gauge measures suctionin the smoke pipe of an oil burner?

1. Suction2. Draft3. Vacuum4. Barometric

5-11. Suction in the smoke pipe orcombustion chamber of an oil burneris measured in

1. inches of mercury2. centimeters of mercury3. inches of water4. cubic centimeters of water

1. Flue-gas analyzer2. Draft analyzer3. Stack analyzer4. Gas-burner analyzer

5-13. To test fuel pump valve operation,remove the nozzle line at the pumpconnection, start and stop the pump,and observe whether the valve cuts offsharp and clean.

1. True2. False

5-14. When the pressure regulator of thefuel pump requires adjustment, youshould use which of the followingtools?

1. Phillips head screwdriver2. Allen wrench3. Inch-pound torque wrench4. Tack hammer

5-15. Refer to appendix II, table M. Whenyou troubleshoot an oil pump, what isthe most likely cause of noisyoperation?

1. Restricted intake line2. Broken coupling3. Air in the inlet pipe4. Loose plugs or fittings

5-16. A cast-iron hot-water boiler is capableof developing what maximumhorsepower?

1. 302. 5 53. 8 04. 9 8

37

5-17. What term is used to identify a boilerthat has water in its base?

1. Wet-bottom2. Water-laden3. Wet-boiler4. Soaked-boiler

5-18. What is the primary disadvantage ofcast-iron hot-water heating boilers?

1. They are subject to corrosion2. They are constructed in two

sections3. They crack or break when handled

improperly4. They require special equipment to

lift them

5-19. Most steel hot-water boilers areconstructed in a total of how manysections?

1. O ne2. Two3. Three4. Four

5-20. The major disadvantage of a one-piecesteel hot-water boiler is that it is heavyand requires special lifting equipment.

1. True2. False

5-21. A boiler foundation should extendwhat distance above the finishedfloor?

1. 5 inches2. 2 inches3. 3 inches4. 4 inches

5-22. What design feature in a boiler holdsthe hot gases as long as possible sothey give maximum heat beforepassing into the chimney?

1. Baffles2. Accumulators3. Retainers4. Reservoirs

5-23. As a minimum, pressure-relief valvesshould be operated at what intervals toprevent corrosion or sticking?

1. Weekly2. Biweekly3. Monthly4. Bimonthly

5-24. What action should you take when therelief pressure on the gauge exceedsthe setting of the nressure-relief valve?

1.

2.

3.

4.

Check the valve pressure with aspring scale and adjust it to therequired amountCheck the valve pressure with anaccurate gauge and replace thedefective pressure gaugeCheck the valve pressure with anaccurate gauge and adjust it to therequired amountReplace the valve

5-25. To calibrate a pressure gaugecorrectly, you should use a

1. spring scale2. deadweight tester3. screed unit4. master stage gauge

38

5-26.

5-27.

5-28.

What device shuts down the firingequipment in case of an induced orforced draft failure?

1. Pressure gauge2. Pressure-relief valve3. Water-level control valve4. Airflow switch

The distribution systems and pipingfor hot-water heating systems aresimpler in design than those for steam.

1. True2. False

The use of a one-pipe, open-tankgravity system is NOT recommendedfor which of the following reasons?

1. It is too expensive2. It is difficult3. It is hard to get enough circulation

by gravity4. It requires too much maintenance

5-29. The water temperatures are lowest inthe two-pipe, open-tank gravity systemin what part of the circuit?

1. Top2. Bottom3. Beginning4. End

5-30.

5-31.

5-32.

When the water in a one-pipe, closedtank distribution system is heated, thewater expands into the pneumaticexpansion tank.

1. True2. False

A gravity closed-tank system with anaverage boiler water temperature of190°F has a radiator emission rate of

1. 180 Btu per square foot2. 170 Btu per square foot3. 160 Btu per square foot4. 150 Btu per square foot

What factor allows the temperature ina closed hot-water system to exceed212°F?

1. Increased pressure prevents thewater from boiling

2. Decreased pressure prevents thewater from boiling

3. Steam is required for maximumheating

4. Average radiator output exceeds150 Btu psf

5-33. In a hot-water system, the water beingdistributed is within what temperaturerange?

1. 130°F to 220°F2. 140°F to 212°F3. 150°F to 250°F4. 160°F to 270°F

39

5-34. Of the following advantages, whichone does NOT apply to a forced-circulation, hot-water distributionsvstem?

1.2.

3.

4.

Smaller diameter pipe can be usedRadiators can be placed in thesame level as the boilerA positive flow of water is assuredthroughout the systemThe friction and temperaturelosses for all radiators are nearlyequal

5-35. What component is used on a one-pipe, closed-tank, forced-circulationsystem that is not required on a one-pipe, gravity system?

1. Pressure-relief valve2. Circulating pump3. Water-level control4. Airflow switch

5-36. What is the minimum pitch per 10 feetfor main and branches, so air in thesystem may be discharged throughradiators and relief valves?

1. 1 inch2. 1 1/2 inches3. 2 inches4. 2 1/2 inches

5-37. Which of the following componentsallows trapped air in the distributionlines of a hot-water distributionsystem to be released from thesystem?

1. Air shutoff vent2. Air pressure release valve3. Manually operated key type of air

vent4. Quick-release valve

5-38. You should take what action toprevent water from leaking around thevalve stem of a radiator shutoff valve?

1. Replace the packing2. Tighten the packing nut3. Install a valve stem4. Install a new shutoff valve

5-39. You should inspect unit heaters atwhat intervals?

1. Weekly2. Monthly3. Quarterly4. Yearly

5-40. A circulating pump does not requirewhich of the following devices?

1. Shaft packing glands and valves2. Valves and float elements3. Shaft packing glands and seals4. Float control elements and traps

5-41. What is the purpose of the reducingvalve?

1.

2.

3.

4.

To keep the closed systemsupplied with water at apredetermined pressureTo keep the open system suppliedwith water at a predeterminedpressureTo reduce differences in waterpressure to a safe system pressureTo maintain differences in watertemperature and safe systempressure

40

5-42. You should check the flow controlvalve for correct down-free movementat what intervals?

1. Monthly2. Biweekly3. Weekly4. Daily

5-43. Which of the following is not amaintenance action required on a hot-water heating system?

1.

2.

3.

4.

Ensure that all of the air is out ofthe systemEnsure that the radiators are full ofwaterEnsure that the circulating pumpsare oiled regularlyEnsure that the pressure-reducingvalves are checked periodically

5-44. Operator maintenance on anelectrically driven feed pump consistsmostly of

1. oiling the pump and motor2. repacking the stuffing box3. cleaning the pump and motor4. tightening the packing gland nuts

5-45. Which of the following actions is nota maintenance requirement for feed-water heaters and economizers?

1. Removing solid matter from theunits

2. Lubricating the pump motor3. Repairing inoperative valve and

pumps4. Stopping steam and water leaks

5-46. Which of the following is not anadvantage of a high-temperature hot-water (HTHW) system?

1. Minimum maintenance2. High thermal efficiency3. Easy operation4. Light weight design

5-47. What happens to the heat in a high-temperature hot-water system that isNOT used by heat-consumingequipment or lost through piperadiation?

1. It is vented to the atmosphere2. It is returned to the boiler plant3. It is stored in a reservoir4. It is recirculated through the

system

5-48. What is the high-temperature range formost military and federal heatingplants?

1. 300°F to 400°F2. 325°F to 425°F3. 350°F to 450°F4. 375°F to 475°F

5-49.What factor determines the maximumwater temperature used in a high-temperature hot-water system?

1. Thermal efficiency2. Cost3. Method of circulating the water4. Operating pressure

41

5-50. What type of pump is used in a onepump high-temperature hot-watercirculation system?

1. Rotary2. Diaphragm3. Reciprocal4. Centrifugal

5-51. The two common ways of heatingwater in an HTHW system are to usehot-water boilers and a/an

1. cascade or direct contact heater2. matched set of generators3. indirect contact heater4. drum installation

5-52. What are the basic designs forpressurizing HTHW systems?

1 .

2 .

3 .

4 .

Mechanical gas cushion andautomatic gas cushionSaturated steam cushion andmechanical gas cushionAutomatic gas cushion andhydraulic gas cushionAutomatic gas cushion andsaturated gas cushion

5-53. The water in a HTHW heating systemis drawn from the lower part of theexpansion tank, mixed with the systemreturn water, and circulated throughthe system. Mixing is required forwhich of the following reasons?

1.

2.

3.

4.

To prevent cavitation at the pumpsuctionTo prevent cavitation at the pumpdischargeTo decrease saturation temperaturein the system flashing at the pumpdischargeTo maintain saturationtemperature in the system

5-54. Load variations in a HTHW systemwill cause supply pressure changes,create flashing of saturated liquid inthe system, and produce

1. cavitation2. corrosion3. water hammer4. air locks

5-55. What type of gas is used as the sourceof pressure in a mechanical gascushion?

1. Oxygen2. Nitrogen3. Methane4. Carbon dioxide

5-56. What is the weakest link in amechanical gas cushion?

1.2.

3.4.

Generator tubesSteam drum

Reservoir for stagnant waterNitrogen space in the expansiontank

5-57. To prevent oxygen corrosion in aHTHW system, you should add whatchemical to the system?

1.2.3.4.

Aluminum sulfiteSodium phosphateSoda ashSodium sulfite

5-58. To rid the system of oxygen, youshould allow the expansion drum ventin a steam-pressurized system to blowfor what length of time?

1. 1 hour2. 2 hours3. 3 hours4. 4 hours

42

5-59.

5-60.

When operating an HTHW system,you should ensure the water is withinwhat pH range?

1. 6.3 to 6.92. 7.3 to 7.93. 8.3 to 8.94. 9.3 to 9.9

After installing an HTHW system, youshould test the system at 450 psi forwhat minimum amount of time?

1. 4 hours2. 8 hours3. 12 hours4. 24 hours

5-61. The generator tubes of an HTHWsystem are subjected to an ASME testof 900 psi.

1. True2. False

5-62. All valves and accessories in a HTHWsystem are rated at working pressuresof 540 to 1,075 psi at

1. 475°F2. 450°F3. 425°F4. 400°F

43

ASSIGNMENT 6

Textbook Assignment: "Galley and Laundry Equipment," chapter 5, pages 5-1 through 5-32.

6-1. When supervising personnel, youshould perform what duties other thanjust paying attention to operatinginstructions?

6-5. What equipment is designed to cookfood through a steaming process?

1. Conduct periodic safety lectures2. Conduct periodic preventive

maintenance inspections3. Adapt instructions to local

requirements4. File periodic maintenance

inspection reports

1. Steam table2. Steam kettle3. Steam chest4. Steam pot

6-6. When replacing the gaskets on a full-floating door, you must remove thedoor from the unit. This action allowsfor easier removal of the gasket andcleaning of the gasket channel.

6-2. What department is responsible forconducting sanitary inspections of thegalley?

1.T r u e2.F a l s e

1. Public works 6-7. You should place paper along the edge2. Camp maintenance of the door opening when replacing3. Supply gaskets on a steam chest door for4. Medical which of the following reasons?

6-3. What are the two types of steam kettle"coppers"?

1. Direct-steam and indirect-steam2. Indirect-steam and self-contained3. Self-contained and direct-steam4. Fixed-steam and field-steam

4. To prevent steam from escaping

1. To prevent excess cement fromadhering to the mating surfaces

2. To detect any gasket leaks3. To check for a binding door

6-4. The maintenance schedules forcoppers require inspections to beconducted at what time intervals?

6-8. When the door of a steam chest isadjusted with hexagon-head bolts, thedoor should touch the steamer evenlywithout binding at the corners.

1. Weekly and monthly2. Weekly and quarterly3. Monthly and biannually4. Monthly and annually

1. True2. False

44

6-9.

6-10.

6-11.

6-12.

Which of the following checks is notincluded in the monthly inspection ofa steam table?

1. Check for leaks and corrosion2. Check the thermostat with a

mercury thermometer3. Check the temperature control4. Check the steam pressure on the

gauge

When the thermostat of a steam tableis checked with a mercurythermometer, the thermostat must beaccurate to within plus or minus

1. 6°F2. 7°F3. 5 ° F4. 4 ° F

After filling a domestic dishwasherwith hot water and an approvedcleaning solution, you should thenoperate the machine at hightemperature for what length of time?

1. 10 minutes2. 20 minutes3. 30 minutes4. 40 minutes

After the first descaling and drainingoperation, you should rinse a domesticdishwasher several times for whatlength of time, in minutes?

1. 52. 63. 34. 4

6-13. When selecting the grade andviscosity of the lubrication for adishwasher, you should use whatreference?

1.

2.

3.4.

Fundamentals of Petroleum(NAVEDTRA 10883)Defense Standardization Manual(DOD 4120.3)Annual Book of ASTM StandardsManufacturer's instruction manual

6-14. Before lubricating a domesticdishwasher, you should take whatprecaution?

1.2.3.4.

Obtain the correct lubricateTurn off the powerTurn off the indicator dialClean each component that is to belubricated

6-15. The correct temperature for the washwater of a domestic dishwasher fallswithin what temperature range?

1. 115°F to 118°F2. 125°F to 128°F3. 138°F to 145°F4. 148°F to 155°F

6-16. You should use what type of solventto remove rust from a domesticdishwasher?

1. Air-inhibited sulfuric acid2. Air-inhibited sulfamic acid3. Moisture-proof sulfuric acid4. Moisture-proof sulfamic acid

45

6-17. When cleaning the interior surfaces ofa dishwasher, you should NEVER use

1. air-inhibited sulfamic acids2. steel wool3. abrasive cleaners4. a wire brush

6-18. Which of the following dishwasherinspections is NOT required monthly?

1. Checking the piping system forfaults

2. Checking electrical componentsfor proper operation

3. Checking the pumps and impellersfor corrosion or extreme wear

4. Checking the drive V-belt tensionand alignment

6-19. What is the last step in the annualinspection and maintenance of adishwasher?

1.

2.

3.

4. Record the inspection data on aDD 1348

Disassemble, repair, and replacebad componentsOperate the machine through allsettingsTag the machine with inspectiondata

6-20. When the air-oil mixture of a range iscorrect, the flame should be whatcolor?

1. Orange2. Blue3. R e d4. Yellow

6-21. You should perform what test todetermine the proper fuel-air mixture?

1. Carbon dioxide test2. Hydrostatic test3. Air flow analysis4. Flue-gas analysis

6-22. Range equipment should be entirelyrepainted when bare spots account formore than what percentage of the totalsurface area?

1. 10%2. 1 2 %3. 15%4. 20%

6-23. A range thermostat should be preciseto within how many degreesFahrenheit?

1. 1°F2. 2°F3. 3 ° F4. 5 ° F

6-24.You should service or performpreventive maintenance on a fieldrange quarterly or after what totalnumber of operating hours?

1. 1502. 2 0 03. 2 5 04. 3 0 0

6-25. You should perform which of thefollowing tasks each week on bakeryovens?

1. Clean the pilot2. Adjust loose chains3. Lubricate gearboxes4. Repair cracked walls

46

6-26. You should conduct electrical checkson bakery ovens at what timeintervals?

1. Annually 1. 3502. Quarterly 2. 2253. Monthly 3. 1 5 04. Weekly 4. 1 0 0

6-27. Grease traps should be cleaned at whattime intervals?

1. Daily2. Weekly3. Biweekly4. Monthly

6-28. Accumulated odor-forming solids ingrease traps soon cause what type ofaction?

1. Aseptic2. Organic3. Septic4. Inorganic

6-29. Liquids should be removed fromgrease traps at what interval?

1. Monthly2. Quarterly3. Semiannually4. Annually

6-30. A total of how many units make up acomplete laundry unit?

1. O n e2. Two3. Three4. F o u r

6-31. What is the washing and dryingcapacity, in pounds (dry weight) perhour, of a skid-mounted laundry unit?

6-32. The washer is controlled through acomplete cycle by what means?

3. By a cycling timer4. By an electronic modem

1. By a timer with a formula chart2. By the operator selecting each

segment of the cycle

6-33. Laundry supplies are added to awasher before and during the completecycle in which of the following ways?

1. By injection into the water as it issupplied

2. By an automatic injector3. By an operator manually, a the

beginning of the cycle only4. By an operator manually, as

required

6-34. Washing machines equipped withautomatic supply injection may beoperated manually by making whatadjustment?

1. By rewiring the timer2. By changing the formula chart3. By removing the formula chart4. By turning the formula chart to an

uncut position

47

6-35. When a Milnor washer is installed, themachine should be bolted down toprevent vibration.

1. True2. False

6-36. On a Milnor washer equipped with"steam boil," you should connect thesteam line to what valve?

1. Steam distribution2. Steam solenoid3. Steam control4. Steam injection

6-37. To eliminate water hammer when theinlet valves are closed, you connectthe inlet valves to the water main witha short piece of rubber hose. Thisconnection is made between theupstream side of the strainers and the

1. downstream side of the strainers2. outlet valves3. water main4. steam valve

6-38. The water inlet valve of the washer israted to handle what maximumamount of pressure?

1. 80 psi2. 90 psi3. 100 psi4. 110 psi

6-39. What type of switch is installed so anywasher can be turned off for repairswithout affecting the operation of theothers?

1. Quick disconnect2. Line disconnect3. Power divider4. Power line

6-40. What total number of solenoid valvesare within the supply injector?

1. Five2. Two3. Three4. Four

6-41. You should drain and refill thegearbox of the washer at whatinterval?

3. Semiannually4. Annually

1. Every 2 months2. Quarterly

6-42. Which of the following actions areperformed during the annualinspection of the washer?

1. Adjusting chains and V-belts2. Cleaning the motor clutch

assembly3. Examining the top and walls for

cracks4. Checking the frame for adequacy

of support

6-43. By what method is water removedfrom the material in an extractor?

1. By compression at low speed2. By use of a wringer only3. By centrifugal force to propel the

water to the outer surface of thematerial and then to the drain

4. By a combination of centrifugalforce and wringer

48

6-44.

6-45.

6-46.

6-47.

6-48.

Extractors will operate withoutexcessive vibration if properly leveledand bolted down to a solid foundation.

1. True2. False

When an extractor is installed, whatpercentage of the area of the hold-down pads and rear angle shouldcontact the grout?

1. 50%2. 75%3. 90%4. 100%

The extractor should be lubricated atwhat time intervals?

1. Daily2. Weekly3. Monthly4. Quarterly

What is the hourly capacity of a 42-inch tumbler?

1. 100 pounds2. 125 pounds3. 150 pounds4. 225 pounds

What size opening to the atmospheremust be provided for a 3,000-cfmtumbler?

1. 6 square feet2. 2 square feet3. 3 square feet4. 4 square feet

6-49. On steam-heated tumblers, you shouldmaintain what minimum pressure forefficient performance?

1. 100 psi2. 110 psi3. 125 psi4. 150 psi

6-50. What is the recommended procedurefor exhausting the air discharge fromthe tumbler to the atmosphere?

1. Individually ducted by any route2. Individually ducted by the shortest

route3. Connect each tumbler to the

exhaust manifold4. Connect each tumbler to a central

exhaust blower

6-51. You should check and tighten wireconnections to the electrical controlbox of a laundry tumbler at what timeintervals?

1. Daily2. Weekly3. Monthly4. Annually

6-52. You should remove and clean thecylinder motor and fan motor of alaundry tumbler at what timeintervals?

1. Annually2. Semiannually3. Quarterly4. Monthly

49

6-53. What amount of time is required for asteam generator to develop its full-rated pressure from a cold start?

1. 5 minutes2. 2 minutes3. 3 minutes4. 4 minutes

6-54. What feature on a steam generatorensures a wet tube in the generator-heating unit at all times?

1. Feedwater regulator2. Low-water cutoff3. Constant capacity pump4. Hot-well feedwater tank

6-55. The pump diaphragms of a steamgenerator are operated in whatmanner?

1. Pneumatically2. Electrically3. Hydraulically4. Electra-hydraulically

6-56. The boiler of a steam generator isequipped to bum

1. No. 1 diesel fuel2. No. 2 diesel fuel3. kerosene4. blended fuel oil

6-57. You should install what device next tothe boiler connection of a steamgenerator to allow easy removal ofparts for inspection and cleaning?

1. Rubber hose2. Flexible metal-clad hose3. Flexible hose with quick

disconnects4. Pipe union

6-58. What is the minimum allowable sizeof flue pipe to be used on a steamgenerator?

1. 10 inches2. 11 inches3. 12 inches4. 18 inches

6-59. What amount of gravity feed isrequired with temperatures above200°F in the hot-well tank?

1. 72 inches2. 76 inches3. 80 inches4. 84 inches

6-60. A thermostat control test should beconducted on a steam generator atwhat interval?

1. Every 140 hours2. Every 130 hours3. Every 110 hours4. Every 100 hours

6-61. If a heating coil is restricted, thecondition will be shown by which ofthe following readings?

1. 5 to 10 psi above normal2. 10 to 15 psi above normal3. 20 to 25 psi above normal4. 30 psi or greater above normal

6-62. On a steam generator equipped withoil-wick lubrication, you should addoil to the reservoirs of the motors atwhat interval?

1. Every 180 days2. Every 90 days3. Every 45 days4. Every 30 days

50

6-63. The water pump crankcase in a steamgenerator should be changed

1. annually2. semiannually3. quarterly4. monthly

6-64. When the water pump relief valve on asteam generator is adjusted correctly,it should open at what pressure?

1. 400 psi2. 450 psi3. 500 psi4. 550 psi

6-65. Before adjusting the thermostat on asteam generator, the generator must be

1. operated with steam at minimumpressure

2. thoroughly heated and shut down3. thoroughly heated and operating4. shut down and drained

6-66. What are the four basic operations thatmake up a washing cycle?

1. Spin, drain, agitate, and fill2. Agitate, rinse, drain, and spin3. Fill, agitate, rinse, and spin4. Fill, agitate, drain, and rinse

6-67. The timer starts running immediatelyonce the washer is started.

1. True2. False

6-68. What basic component in the washeris known as the brain?

1. Main drive motor2. Transmission3. Water pump4. Timer

6-69. The timer motor is geared down to runat a speed of how many revolutionsper hour?

1. 7/82. 3 /43. 1 /24. 1/4

6-70. The average main drive motor in anautomatic washer is what size, inhorsepower?

1. 1/32. 1/23. 1 1/24. 1 1/3

6-71. The hot- and cold-water lines of theautomatic washer operate by whatmeans?

1. By a solenoid2. By a pneumatic control3. By a hydraulic control4. By a hydro-pneumatic control

6-72. What component acts as a safetydevice on an automatic washer?

1. Timer2. Water-level switch3. Door interlock switch4. Temperature selector switch

51

6-73. When the timer of an automatic dryeris set, the drum begins to rotate atapproximately how many revolutionsper minute?

1 . 502. 6 03. 7 04. 80

6-74. A dryer should NOT be exhausted intoa convenient chimney.

1 . True2. False

6-75. The dryer vent should not exceed whatmaximum length?

1. 6 feet2. 5 feet3. 3 feet4. 4 feet

52

ASSIGNMENT 7

Textbook Assignment: "Refrigeration," chapter 6, pages 6-1 through 6-22.

7-1. Refrigeration is defined as the processo f

1. removing heat from a substance orarea

2. replacing heat drawn from ansubstance

3. replacing cold drawn from an areaor substance

4. producing cold in substance orarea

7-2. Heat is a product of molecular motionthat is known as kinetic energy.

1. True2. False

7-3. What happens to molecular motionand the state of substance whenenough heat is added to a substance?

1. The motion stops and thesubstance becomes a solid

2. The motion decreases and, if thesubstance was originally liquid, itbecomes solid

3. The motion decreases and, if thesubstance was originally a gas, itbecomes a liquid

4. The motion increases and thesubstance may change state

7-4. Molecular action in a substance isleast when the substance is in whatstate?

1. Vapor2. Liquid3. Solid4. Gas

7-5. When a person says a substance is"cold," what meaning is inferred?

1. It contains no heat2. It cannot transfer heat3. It is at absolute zero4. It has less heat than a comparable

warmer body

7-6. What characteristic of heat is shownby the speed of molecules within asubstance?

1. Quality2. Quantity3. Intensity4. Conductivity

7-7. When you have a pint of water in acontainer and a gallon of water inanother and both are at the sametemperature, what is required to raisethe temperature of each container thesame amount?

1. Different intensities of heat2. Different temperatures of heat3. Different qualities of heat4. Different quantities of heat

7-8. A British thermal unit (Btu) is theamount of heat required to raise thetemperature of 1 pound of water in anystate 1°F at sea level.

1. True2. False

53

7-9. A total of how many Btu is required toraise 5 pounds of water from 40°F to165°F?

1. 1252. 2503. 6254. 650

7-10. Which of the following formulas canFahrenheit tobe used to convert

Celsius?

1. C = (F - 32)18

2. C = (F X 1.8) + 3218

3. C = (F + 32)18

4. C = (F X 1.8) – 3218

7-11. Convert 90° Celsius to degrees inFahrenheit.

1. 180°F2. 194°F3. 212°F4. 232°F

7-12. When you place an ice cube in a glassof water, what reaction developsalmost immediately?

1. The ice melts because it is a solid2. The water gets colder because it is

a liquid3. Heat is transferred from the water

to the ice4. Heat is given up by the ice to the

w a t e r

7-13. What type of heat is equal to thenumber of Btu required to raise thetemperature of 1 pound of anysubstance 1°F?

1. Sensible2. Latent3. Specific4. T o t a l

7-14. A total of how many Btu is required toraise the temperature of 1 pound ofwater 1o?

1. 12. 23. 34. 4

7-15. A total of how many Btu is required toraise the temperature of 10 pounds ofmilk 1o?

1. 6.002. 7.923. 8.294. 9.20

7-16. Sensible heat is heat added to orsubtracted from a substance thatchanges its temperature but not itsphysical state.

1. True2. False

7-17. What type of heat is absorbed or givenoff when the physical state of asubstance is changing?

1. Latent2. Specific3. Effective4. Sensible

54

7-18. Latent heat of fusion is the amount ofheat required to change the state of asubstance without affecting itstemperature.

1. True2. False

7-19. Total heat equates to the sum of whattwo types of heat?

1. Sensible and specific2. Latent and sensible3. Effective and latent4. Sensible and effective

7-20. A day-ton of refrigeration is theamount of refrigeration produced bymelting 1 ton of ice at 32°F in 24hours.

1. True2. False

7-21. What total number of Btu equals aday-ton of refrigeration?

1. 288,0002. 144,0003. 24,0004. 12,000

7-22. An air conditioner rated at 24,000 Btuequals a total of how many day-tons?

1. 12. 1 1/23. 24. 2 1/2

7-23. Atmospheric pressure at sea level is

1. 17.4 psia2. 15.7 psia3. 14.7 psia4. 13.5 psia

7-24. In refrigeration work, pressures aboveatmospheric pressure are measured inpounds per square inch. In whatmanner are pressures belowatmospheric pressure measured?

1. Inches of water2. Inches of vacuum3. Inches of mercury4. Inches of vapor

7-25. Refrigeration is made possible byaltering the environment to allow whatcondition to occur?

1.

2.

3.

4.

Increased pressure on the makeupof a substanceReduced pressure on the volumeof a substanceIncreased pressure on the volumeof a substanceReduced pressure on the boilingtemperature of a substance

7-26. Vaporization is the process ofchanging a

1. liquid into a gas by increasing itspressure

2. gas into a liquid3. liquid into a gas by adding latent

heat of fusion4. liquid into a gas by evaporization

or boiling

7-27. What is meant by the termcondensation?

1. To change vapor into a liquid2. To change a liquid into a vapor3. To change a solid into a liquid4. To change a liquid into a solid

55

7-28. A refrigeration compressor increasesthe pressure on the gas and thecondenser cools the gas. These twofactors are critical to whatrefrigeration process?

1. Adding latent heat of fusion2. Adding of latent heat of

vaporization3. Accelerating evaporation4. Producing condensation

7-29. A refrigeration compressor withdrawsthe heat-laden refrigerant vapor fromthe evaporator and compresses the gasto a pressure that will liquefy in thecondenser.

1. T rue2. False

7-30. The crankshaft seal on a refrigerationcompressor must prevent refrigerantand oil from leaking out and preventair and moisture from entering thecompressor.

1. True2. False

7-31. What are the two types of compressorcrankshaft seals?

1. Quad-ring and U-cup2. O-ring and V-ring3. Stationary bellows and rotating

bellows4. T-seal and flange packing

7-32. The term "hermetic" means airtightand refers to the

1.

2.

3.

4.

seal between the crankshaft andthe crankcasetype of tubing connections used atthe input and output of thecompressorcase in which the motor andcompressor are locatedleakproofing of the bellows seal

7-33. The electrical motor and compressorof a hermetically sealed unit are sealedin the same case. By which of thefollowing means are the motor andcompressor cooled?

1. By water circulation2. By oil circulation only3. By the refrigerant vapor moving

through the case only4. By oil circulation and moving

refrigerant through the case

7-34. Which of the following factors is notan advantage of a hermetically sealedcompressor?

1. Elimination of a source of oil leaks2. Elimination of pulleys3. Elimination of coupling methods4. Increased working capacity

7-35. Which of the following is not a type ofcondenser?

1. Air-cooled2. Water-cooled3. Evaporative4. Pressurized

56

7-36. What type of condenser is used wherelow-quality water and its disposalmake the use of circulating water-cooled types impractical?

1. Air-cooled2. Evaporative3. Pressurized4. Constant pressure

7-37. What type of condensers uses severallayers of small tubing formed into flatcoils?

1. Water-cooled2. Evaporative3. Air-cooled4. Constant pressure

7-38. What device is installed in the waterboxes of water-cooled condensers toreduce electrolytic corrosion?

1. Anodes2. Cathodes3. Zinc wasting bars4. Anticorrosion screens

7-39. The capacity of the water-cooledcondenser will NOT be affected bywhich of the following factors?

1. Temperature of the water2. Temperature of the refrigerant3. Quality of the water4. Quantity of the water

7-40. What is the function of the receiver?

1. To provide a reserve of gaseousrefrigerant that is fed to thecondenser as needed

2. To store liquid refrigerantavailable from the condenserduring off-peak operation

3. To trap liquid refrigerant as itleaves the evaporator to preventslugs of liquid refrigerant fromentering the compressor

4. To trap oil that leaves thecompressor and prevents it fromentering the condenser orevaporator

7-41. What factor causes the refrigerant inthe evaporator to boil?

1. The suction action of thecompressor

2. The absorption of heat3. The high-saturation action of the

condenser4. The conversion from a liquid state

to a gaseous state

7-42. What are the two types of evaporators?

1. Dry and flooded2. Wet and flooded3. Dry and saturated4. Dry and unsaturated

7-43. What type of evaporator uses therefrigerant in the evaporator to cool asecondary medium other than air?

1. Direct expanding2. Indirect expanding3. Forced-air4. Natural convection

57

7-44. What is superheat?

1. The heat absorbed in theevaporator required to change theliquid to a gas

2. The difference in degrees betweenthe saturation temperature and theincreased temperature of the gas

3. The heat left in the liquidrefrigerant as it leaves theexpansion valve

4. The latent heat of vaporization

7-45. What is the purpose of the low-sidefloat valve used with a floodedevaporator?

1. To control the flow of liquidrefrigerant

2. To maintain a constant evaporatorpressure

3. To increase the level of liquidrefrigerant in the receiver

4. To ensure that only gaseousrefrigerant enters the evaporator

7-46. The float valve of a high-side floatexpansion valve is located in the

1. liquid receiver2. evaporator3. capillary tube4. compressor

7-47. What happens to refrigerant flowwhen the compressor shuts off in asystem with capillary tubes?

1. The flow stops immediately2. The flow continues until the

remote bulb shuts off3. The flow continues until the

pressures in the evaporator andcondenser are equal

4. The flow stops immediately if theevaporator is cool

7-48. In what location of a refrigerationsystem is a spring-loaded relief valveinstalled?

1. Between the compressor dischargeconnection and the discharge linestop valve

2. In the suction side of thecompressor

3. Just beyond the compressorstrainer

4. Next to the compressor shutoffvalve

7-49. Solenoid stop valves are often used tocontrol liquid flow to which of thefollowing components?

1. Condenser2. Receiver3. Strainer4. Expansion valve

7-50. What is the function of thedehydrator?

1. To offer resistance to the flow ofthe refrigerant

2. To change the gaseous refrigerantto a liquid

3. To remove compressor oil fromthe refrigerant

4. To remove moisture from therefrigerant

58

7-51. Bubbles appearing in the sight-flowindicator of a refrigeration systemnormally indicates the existence ofwhat condition?

1. The proper amount of refrigerantgas is flowing to the evaporator

2. The proper amount of liquidrefrigerant is flowing to theevaporator

3. The system is low on refrigerant4. The dehydrator is not removing

moisture from the system

7-52. A pressure regulator is installedbetween the outlet of the evaporatorand the compressor to prevent

1. the evaporator pressure from beingtoo high

2. the evaporator pressure from beingtoo low

3. a restriction in the refrigerant flowwhen pressure is too low

4. a restriction in the suction linewhen pressure is too high

7-53. What is the function of the suction linefilter-drier?

1. To remove dirt, scale, andmoisture from the refrigerant afterit leaves the compressor

2. To remove dirt, scale, andmoisture from the refrigerant afterit leaves the evaporator

3. To remove dirt, scale, andmoisture from the refrigerantbefore it enters the compressor

4. To remove dirt, scale, andmoisture from the refrigerantbefore it enters the evaporator

7-54. What is the function of theaccumulator?

1. To trap oil out of the system2. To provide a reservoir of liquid

refrigerant for the thermostaticexpansion valve

3. To prevent liquid from reachingthe compressor suction inlet

4. To provide a reservoir of liquidrefrigerant for the capillary tube

7-55. To prevent the accumulation of oil invarious sections of the refrigerationsystem, you should install an oilseparator between what twocomponents?

1. Evaporator and compressor2. Compressor and condenser3. Condenser and receiver4. Receiver and thermostatic

expansion valve

7-56. Which of the following refrigerants isNOT considered a primary refrigerant?

1. Diclorodifluorohethane2. Hydrofluorcarbon3. Monchlorodifluoromethane4. Refrigerant 502

7-57. A secondary refrigerant is cooled by

1. releasing its latent heat ofvaporization into the space to becooled

2. releasing its heat load to theprimary refrigerant

3. expanding in an evaporator andvaporizing

4. being compressed and condensedin a refrigeration system

59

7-58. Refrigerants are classified into groups.Which of the following groups isconsidered the safest?

1. I2. I I3. III4. IV

7-59. What is the primary risk of R-12 topersonnel?

2. Poisonous fumes from the liquidwaste it produces

1. Freezing effect it has on both skinand eyes

3. Strong smell it produces4. Tendency it has to decompose into

deadly phosgene gas

7-60. The cylinder color code for R-502 is

1. silver2. green3. whi te4. orchid

7-61. R-717 is commonly used in whatsystems?

1. Residential2. Commercial3. Industrial4. Medical

7-62. Which of the following refrigerants isa blend component used in low- andmedium-temperature applications?

1. R-1252. R-134a3. R-5024. R-717

7-63.

7-64.

R-12 refrigerant that was used inautomotive air conditioning is beingreplaced by which of the followingrefrigerants?

1. R-5022. R-1253. R-134a4. R-114

When refrigerant contacts the eyes,rather then flood the eyes with water,your first step for first aid should be toirrigate the eyes with drops of a

1. weak boric acid solution2. 2 percent saltwater solution3. sterile mineral oil4. weak solution of baking soda

7-65. You should take what action, if any,when refrigerant has been dischargedfrom a cylinder?

1.

2.

3.

4.

Weight the cylinder and record theweight of the refrigerant remainingon the cylinderWrite the letters "MT" on thecylinder to designate that thecylinder is emptySeparate the cylinder from the fullcylinders, so it can be used firstNo action is required

60

ASSIGNMENT 8

Textbook Assignment: "Refrigeration and Air Conditioning" chapter 6, pages 6-23 through 6-52and chapter 7, pages 7-1 through 7-46.

8-1. The condenser in a self-containedrefrigeration system is installed inwhat general location?

1. An uninsulated compartment2. An insulated compartment3. A hermetically sealed compressor

unit4. An outside area for increased

cooling

8-2. Reach-in refrigerators have a storagecapacity of

1. 10 cubic feet or greater2. 15 cubic feet or greater3. 20 cubic feet or less4. 25 cubic feet or less

8-3. In a typical self-contained reach-inrefrigerator, the evaporator is mountedat what location?

1.

2.

3.

4.

On the side of the upper portion ofthe food compartmentOn the side of the lower portion ofthe food compartmentIn the center of the upper portionof the food compartmentIn the center of the lower portionof the food compartment

8-4. Which of the following types ofrefrigerants can be used in smallcapacity, reach-in refrigerators?

8-5. What factor distinguishes the twotypes of walk-in refrigerators?

1. Location of the compressor2. Location of the condenser3. Type of evaporator4. Inside temperature

8-6. What type of refrigerant is used inmost domestic refrigerators?

1. R-122. R-223. R-134a4. R-717

8-7. What type of compressor is used on asingle door domestic refrigerator?

1. External drive2. Open3. Rotary4. Hermetic

8-8. What type of automatic defrostingsystem uses the heat in the vapor fromthe compressor discharge line and thecondenser to defrost the evaporator?

1. Forced air2. Hot gas3. Direct evaporation4. Instantaneous

1. R-222. R-1253. R-5024. R-717

61

8-9. In a frost-free refrigerator-freezer, theevaporator is at what location?

1 .

2 .

3 .

4 .

At the bottom, inside therefrigeration compartmentAt the top, inside the refrigerationcompartmentOn the side, inside the freezercompartmentOutside the refrigerationcompartment

8-10. What type of water cooler only coolswater when it is being drawn?

1. Instantaneous2. Storage3. Dispenser4. Bottle

8-11. What component of a water coolerprecools the fresh water line to theevaporator?

1. The condenser2. The storage tank3. The heat exchanger4. The cold water dispenser

8-12. Many manufacturers of ice machineshave switched from using R-22 to

1. R-404a2. R-134a3. R-5024. R-717

8-13. When installing a refrigerationsystem, you must not allow dirt, scale,or moisture to enter any part of thesystem.

8-14. You should take what action if there isa question about the cleanliness of thepiping to be used in the installation ofa refrigeration svstem?

1.

2.

3.

4.

Rod out each length of pipe with acloth swabUse a strong blast of air to blastout each length of pipeFlush each length of pipe withfresh waterDiscard the piping and replacewith new pipe

8-15. The corrosion in a refrigeration systemresults from hydrochloric acid whichis formed by

1. R-12 coming in contact with air2. R- 12 coming in contact with

compressor oil3. R-12 coming in contact with scale4. R-12 coming in contact with water

8-16. Water-cooled condensers requires afree area equal to the

1. length of the evaporator2. width of the evaporator3. length of the condenser4. width of the condenser

8-17.

1. 6 inches2. 12 inches3. 18 inches4. 24 inches

Service openings and inspectionpanels on unitary equipment requirewhat minimum distance?

1. True2. False

62

8-18. What malfunction can occur if there is 8-22. When installing two compressors ofinadequate ventilation around an air- different sizes, you should take whatcooled condenser? action to ensure proper operation?

1. The condenser overheats2. The motor overloads3. Ice forms in the expansion valve4. Sludge builds up in the condenser

8-19. On a closed-coupled installation, boththe suction and liquid lines are to beran overhead. This type of installationwill assist in the elimination of

1. vibration strains2. relief valves3. cooling coil traps4. siphoning of liquid from the

receiver

8-20. When preparing a pipe fitting formaking silver solder joints, you.should use what type of material tobrighten up the ends?

1. Emery cloth2. Steel wool3. Crocus cloth4. Sandpaper

8-21. Parallel operation of two or morereciprocating compressors should beavoided unless there is a strong andvalid reason for not using a singlecompressor.

1. True2. False

1. Change pulleys to two differentsizes

2. Adjust the height of the bases sothey are the same level

3. Change the drive belts so they runat the same speed

4. Install a check valve in theequalizer line so pressure remainsconstant in each compressor

8-23. You should NEVER use a singleequalizer line on compressors havingtwo equalizer tappings.

1. True2. False

8-24. When using two compressors and thecondensers are more than 10 feetabove the compressors, you shouldinstall what additional component inthe horizontal discharge line?

1. V-trap2. Oil filter3. Oil separator4. Water separator

8-25. If an oil separator is used at thebottom of a discharge riser, whatcomponent is eliminated?

1. Double riser2. Suction line3. Liquid line4. Hot gas discharge riser

63

8-26. When refrigerants are beingtransferred,. the amount of refrigerantthat may be placed in a cylinder is

1. 65 percent of the tare weight2. 75 percent of the tare weight3. 85 percent of the tare weight4. 95 percent of the tare weight

8-27. When transferring refrigerants, youshould place what device in thecharging line to the service cylinder?

1. One-way check valve2. Pressure relief valve3. Poppet valve4. Shutoff valve

8-28. When a refrigeration system isexcavated, which of the followingvalves is NOT required to be open toallow the vacuum pump to draw backthrough the receiver and condenser tothe compressor?

1. Discharge service valve2. Expansion valve3. Receiver service valve4. Condenser service valve

8-29. When evacuating a refrigerationsystem, you should allow the vacuumpump to draw a vacuum of at least

1. 10 inches2. 15 inches3. 20 inches4. 25 inches

8-30. In most small refrigerating systems,high-side charging is recommendedfor adding refrigerant after repairshave been made.

1. True2. False

8-31. A halide leak detector is NOT used todetect which of the followingrefrigerants?

1. R-122. R-223. R-1704. R-502

8-32. When you are performing a halideleak test, what color does the flameturn when the halogen refrigerantcontacts the reactor plate?

1. Yellow2. Blue3. Orange4. Green

8-33. What term is used to describe theprocess of cleaning refrigerant forreuse by oil separation?

1. Recovery2. Reclaiming3. Recycling4. Refresh

8-34. When you are reclaiming refrigerant,the liquid refrigerant is stored in astorage chamber where it is cooled.What component is responsible forcooling the refrigerant?

1. The evaporator assembly2. The receiver and purge unit3. The recycle solenoid4. The oil separator accumulator

64

8-35. Which of the following actions isNOT to be performed when removinga compressor from a refrigerationsystem?

1.

2.

3.4.

Remove the drive belt ordisconnect the drive couplingPlug all openings through whichrefrigerant flowsPump down the systemRemove the suction and dischargelines from the compressor servicevalves

8-36. What component is installed in theliquid line to absorb moisture in therefrigeration system?

1. Separator2. Water filter3. Dehydrator4. Evaporator

8-37. You should defrost plate-typeevaporators in below-freezingrefrigerators when ice has built up towhat thickness?

1. 1/8 inch 1. Atmospheric2. 1/4 inch 2. Temperature conversion3. 1/2 inch 3. Hygrometric4. 3/4 inch 4. Psychrometric

8-38. Operation and maintenance logs assistyou in spotting trouble in theequipment.

1. True2. False

8-39. Which of the following is a type ofmaintenance log entry?

temperature

1. Ambient temperature2. Operating hours3. Material used4. Condenser pressure and

8-40. Maintenance logs can be used todetermine future budgetrequirements.

1. T rue2. False

8-41. Air conditioning is the process ofconditioning the air in a space tomaintain a predetermined temperature-humidity relationship to meet comfortor technical requirements.

1. True2. False

8-42. What type of chart is used to calculateeffective temperature?

8-43. The specific effective temperaturewithin the zone at which most peoplefeel comfortable is identified as the

1. comfort line2. optimum line3. psychrometric line4. hygrometric line

65

8-44. What instrument is used to determinerelative humidity?

1. Modified wet-bulb thermometer2. Hygrometer3. Sling psychrometer4. Humidistat gauge

8-45. When air becomes saturated withmoisture, the wet-bulb, dry-bulb, anddew point temperatures are all thesame and the relative humidity is whatpercent?

1. 70%2. 80%3. 90%4. 100%

8-46. What control device in an airconditioner is sensitive to variousdegrees of humidity?

1. Hygromistat2. Humidistat3. Thermostat4. Hydromostat

8-47. What method of air cleaning is by farthe most effective; however, it is alsothe most expensive?

1. Magnetic2. Electrical3. Air washing4. Fiber filter

8-48. Air is circulated by either an axial fanor radial fan mounted in an enclosure.These enclosed fans are known as

1. excavators2. eliminators3. blowers4. movers

8-49. The velocity of air is the primaryfactor that determines whattemperature and humidity arerequired to produce comfort.

1. True2. False

8-50. Window mounted air-conditioningunits range in size from 4,000 to36,000 Btu and floor-mounted unitsrange from 24,000 to 360,000 Btu perhour.

1. True2. False

8-51. What type of air-conditioning systemis used for central refrigeration plants?

1. Heat pump2. Chilled-water3. Floor mounted4. Window mounted

8-52. The two types of water coolers mostoften used for chilled water airconditioning are the flooded-shell-and-tube cooler and the

1. pneumatic cooler2. chilled-water cooler3. dry-expansion cooler4. air-cooled cooler

8-53. What two chemicals form a hard scaleon the walls of water tubes that reducetheir efficiency?

1. Mercury and oxides2. Carbon and salt3. Potassium and hydroxides4. Lime and iron

66

8-54. Never add water to acid because itmay result in an explosion that couldseverely injure you.

1. True2. False

8-55. The oil level in the compressor of anair-conditioning system should bechecked

1. daily2. monthly3. weekly4. annually

8-56. If liquid refrigerant contacts a person'seyes, that person must be taken to adoctor immediately.

1. True2. False

8-57. Cooling towers are classified asnatural draft, induced draft, or

1. partial draft2. closed draft3. open draft4. forced draft

8-58. What type of wood is the standardconstruction material for coolingtowers?

1. Knotted pine2. Oak3. Redwood4. Walnut

8-59. A compressor is a pump thatcompresses refrigerant gas.

8-60. Which of the following is NOT a typeof compressor?

1. Rotary2. Centrifugal3. Cyclical4. Reciprocating

8-61. The term "hermetic unit" means thatthe motor rotor and compressorcrankshaft of a refrigeration systemare in a gas-tight housing that hasbeen welded shut.

1. True2. False

8-62. The humidity-sensitive device thatcontrols the equipment that maintainsa predetermined humidity in the spacein which it is installed is a

1. thermostat2. hydrometer3. humidifier4. humidistat

8-63. For troubleshooting an air-conditioning system, your bestreference is the manufacturer'smanual.

1. True2. False

8-64. The saturation temperature of a liquidor vapor increases according to thepressure exerted on it.

1. True2. False

1. True2. False

67

8-65. The three types of air-conditioning 8-69. What federal agency has establishedcompressors in general use in that all technicians who maintain air-automobiles are the two-cylinder conditioning systems must bereciprocating, swash plate, and certified?

1. universal2. ten-cylinder3. scotch yoke4. electromatic

8-66. The three types of suction pressure-regulating valves used are the suctionthrottling valve (STV), evaporatorpressure regulator (EPR), and the

1. pressure control valve (PCV)2. suction depression valve (SDV)3. pilot-operated absolute valve

(POA)4. temperature equalizer valve (TEV)

8-67. The fastest way to find a condition isto work with the proven diagnosticcharts and the proper special tools forthe air-conditioning system you areworking on.

8-68.

1. True2. False

You must always wear safety glasseswhen servicing any part of an air-conditioning system.

1. Department of the Navy2. Defense Department3. Environmental Protection Agency

(EPA)4. Department of Labor

8-70. Standard air-conditioning certificationis divided into levels corresponding tothe type of service a technicianperforms. How many types oftechnician certification are there?

1. One2. Two3. Three4. Four

8-71. The function of what component of aduct system is designed to deliver aconcentrated air stream into a room?

1. Diffuser2. Grill3. Register4. Damper

8-72. A radial-flow fan is normally belt-driven.

1. True2. False

1. T rue2. Fa l s e

68