3.General Notes on Engineering Hardware - Seals, Gaskets, Valves

7/29/2019 3.General Notes on Engineering Hardware - Seals, Gaskets, Valves

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Part 3 of 6:

SEALS, GASKETS AND VALVES

Table of Contents

1 Definition ........................................................................................................ 22 Functions of Seals ........................................................................................... 2

2.1 Examples of seals ..................................................................................... 42.1.1

Lip seals ............................................................................................. 6

2.1.2 Piston rings ....................................................................................... 92.1.3 Metal-to-metal joints ....................................................................... 112.1.4 Gaskets ............................................................................................. 112.1.5 Sealing washers ................................................................................ 142.1.6 O-rings ............................................................................................. 142.1.7 Further examples ............................................................................ 18

3 Pipes and Pipe Fittings ................................................................................. 183.1 Plastic pipes ........................................................................................... 183.2 Copper pipes ........................................................................................... 193.3 Steel pipes .............................................................................................. 24

4 Valves ............................................................................................................ 264.1 Types of valve ......................................................................................... 27

4.1.1 Gate valves ...................................................................................... 284.1.2 Globe valves .................................................................................... 294.1.3 Poppet valves .................................................................................. 30 4.1.4 Butterfly valves ................................................................................ 314.1.5 Needle valves ................................................................................... 324.1.6 Safety valves .................................................................................... 334.1.7

Pressure relief valves ...................................................................... 34

4.1.8 Pressure regulating valves .............................................................. 35


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Mechanical engineering very often involves the design, construction, use and

maintenance ofMACHINES. A machine implies movement, if any useful task is to be

performed. There are very many different machines, performing very many

different tasks. One example is the petrol engine which drives a car or motor cycle.

The car itself is in fact a more complex machine which incorporates a number of

simpler machines or mechanical systems such as engine, gearbox, differential, etc.

Another example is a refrigerator in which refrigerant is pumped round and round a

series of pipes, radiators, valves etc. to perform its cooling function. The

refrigerator includes a number of sub-systems such as the pump for the refrigerant,the motor to drive the pump, the control valves, etc.

In both examples given above, and in many other common examples, the

machines work (and continue to work satisfactorily) only because of the use of

effective SEALS serving many different functions at many different locations in these

machines.

1 DefinitionSEALS are usually defined as components or assemblies which prevent the passage

of fluids between the m oving parts of a machine. Note that "fluid" may refer to

liquid, vapour or gas.

Where the need arises to prevent the leakage of fluid between two stationary

parts, different sealing components, often called GASKETS, are used. These are

described later in this Project.

2 Functions of SealsSeals have a number of quite distinct functions. Not all seals perform all the

functions listed below. The great diversity of seal types is in fact a result of the wide

variation of seal requirements.

Some of the functions seals may be required to perform are to:

1. Seal working fluid into its desired location.

e.g. In a car engine the piston rings seal the compressed gas in the space above

the piston.


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2. Prevent escape of lubricant.

e.g. In a car engine seals prevent loss of lubricating oil where the ends of the

crankshaft protrude from the engine assembly to drive the flywheel at the rear

and the accessory drive belts at the front.

3. Prevent contamination.

e.g. Seals in a food processing machine prevent grease from the working parts

from contaminating the food product.

4. Prevent the ingress of dirt.

e.g. It is vitally important to "seal out" abrasive dust from the steering joints

and driveshafts on a tractor.

5. Prevent pollution and environmental damage.

e.g. Seals on a CFC-based automotive refrigeration system prevent the

refrigerant escaping to the atmosphere.


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2. 1 Examples of seals

Figu r e 3-1 Figure 3-1 is a very simplified freehand sketch of a single-cylinder

petrol engine. The view shown is a section cut vertically through the centreline of

the cylinder and piston, with all seals and bearings omitted. Can you see any major

fault with the configuration as drawn? 1

1If you look carefully, it is obvious that there is insufficient height to allow the piston to rise as

the crankshaft rotates, nor is there room for the crankshaft webs to clear the crankcase.


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Figu r e 3-2 The sketch in Fig 3-1 with bearings shown in green, piston rings in red,

gaskets in purple, lip type seals on the crankshaft in blue, metal-to-metal joint on

the poppet valve in pink and sealing washers in yellow.

Fig 3-2 shows the use of two different types ofSEALS to prevent the passage of fluid

between m o vin g p a r t s . The ends of the rotating crankshaft must project from theengine so that it can be used to do useful work. The crankshaft runs in BEARINGS


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which must be lubricated with a continuous flow of oil to reduce friction and

prevent the bearings from seizing. The flow of oil also helps to keep the bearings

cool. SEALS must be used to prevent the lubricating oil from escaping from the

outer ends of the crankshaft bearings, otherwise the oil supply soon runs out and

the engine is at risk of major damage.

It is clear that there must be very significant differences between the seals used

on the two ends of the crankshaft. With the crankshaft as sketched, a seal of annular

configuration (a ring) can be slipped over the left-hand end of the shaft. On the

right-hand end, the crankshaft drive flange clearly makes this impossible. For the

remainder of this section, the discussion will be on seals of annular configuration

suitable for use where the seal can be slipped axially over its shaft. The generic

name for seals of this type is LIP SEALS.

2.1.1 Lip seals

The need for this type of seal, between a rotating shaft and a stationary housing,

occurs on many machines. Such seals are often referred to as SH AFT SEALS or OIL

SEALS or LIP SEALS. Leather was used initially as the seal material, but this has

been superseded by synthetic rubber seals, using various polymers for different

applications. Seals of this type perform their sealing function by means of a lip

pressing against the rotating surface of the shaft with effectively line contact. In

some seals, the elasticity of the rubber of the seal provides adequate contact with

the shaft. In more difficult conditions (e.g. where the shaft bearing has some

clearance, allowing the shaft to move radially) the natural elasticity of the rubber

may be supplemented by a GARTER SPR ING . The garter spring sits in a recess

within the body of the seal and outside the lip of the seal, as seen in Fig 3-3.

Figu r e 3-3 An example of a LIP TYPE SE AL which uses a GARTER SPR ING to

increase contact pressure between the stationary seal and the rotating shaft.http://1-800-seal-911.com/pages/TFE/FWS/dk351.html
http://1-800-seal-911.com/pages/TFE/FWS/dk351.htmlhttp://1-800-seal-911.com/pages/TFE/FWS/dk351.htmlhttp://1-800-seal-911.com/pages/TFE/FWS/dk351.html


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In many applications, a lip type seal of the general configuration shown in Fig 3-3

provides an adequate sealing solution. In some applications, the garter spring is not

needed, with the lip of the polymer seal providing sufficient elasticity to hold the

sealing lip in contact with the shaft.

As may be seen from Fig 3-4a below, there is a very wide range of general

purpose lip seals. Much of the variety of configuration lies in the design of the

outer part of the seal, the part which fits into and is located by some sort of recess or

housing.

Figu r e 3 -4a Examples of cross-sections of what are described as general purpose

OIL SEALS. The top row shows SINGLE-LIP SEALS while the lower row shows

DOUBLE-LIP SEALS. http://www.fos-oilseal.com.tw/upload_files/general-purpose-type.pdf
http://www.fos-oilseal.com.tw/upload_files/general-purpose-type.pdfhttp://www.fos-oilseal.com.tw/upload_files/general-purpose-type.pdfhttp://www.fos-oilseal.com.tw/upload_files/general-purpose-type.pdf


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Figu r e 3 -4b Examples of cross-sections of a more extensive range ofDOUBLE-LI P

OIL SEALS. http://www.fos-oilseal.com.tw/upload_files/pdf/dual-lip-type.pdf

As shown in the text in Fig 3-4b, one of the main functions of double lip seals is

to ensure that fluids in adjacent parts of a machine do not mix, e.g. the automatic

transmission fluid in some machines is in a compartment adjacent to the

differential which uses different oil and a double lip seal is used to prevent leakage

and mixing. Note that most of these seals are fitted with two garter springs

If the engine in Fig 3-2 operates in dusty conditions, the crankshaft seals may

be required to perform two distinct functions: seal the oil in the engine; and seal

dust and dirt out of the bearings. This sort of condition occurs frequently on

machines such as tractors and earth-moving machinery. Seals of this type are theDOUBLE-LIP SEALS or DUP LEX SEALS such as those seen in Fig 3-4b. The outer

sealing lip prevents dust from becoming wedged in the tapering gap outside the

inner sealing lip. This dust can rapidly wear the shaft so severely that both the seal

and the shaft need to be replaced.
http://www.fos-oilseal.com.tw/upload_files/pdf/dual-lip-type.pdfhttp://www.fos-oilseal.com.tw/upload_files/pdf/dual-lip-type.pdfhttp://www.fos-oilseal.com.tw/upload_files/pdf/dual-lip-type.pdf


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Figu r e 3-5 An example of how a seal might be mounted to seal one end of a shaft

assembly supported on rolling contact bearings. In this example, the shaft bearing

is a deep-groove ball bearing rather than the sliding contact bearings shown in Fig

3-2, and the seal is mounted in an END P LATE or COVER PLATE rather than directly

into the engine block, but the sealing principle is the same. In the particular seal

shown in the centre assembly of Fig 3-5 ((b) com m ercial seal), the rubber seal is

encased within a steel shell and is generally similar to those in Fig 3-4a. The steelshell is pressed into the end plate with sufficient interference fit to prevent lubricant

leaking between the outside of the seal and the end plate. However, many modern

seals, including some in Fig 3-4a, encase the steel shell in a polymer outer layer

which makes the diameter tolerances less critical. In Fig 3-5, diagram (a) Felt seal

shows the cross section of a typical felt seal while diagram (c) Laby rinth seal

attempts to seal by using a series of steps as a barrier to leakage. Both felt seals and

labyrinth seals were less effective than modern lip seals and are now rarely used.Shigley JE and Mischke CR, Mechanical Engineering Design, McGraw Hill,6E p 728. Diagrams

courtesy of New Departure-Hyatt Division, General Motors Corporation.

2.1.2 Piston rings

The second type of seal between moving parts which has been used in the engine

shown in Fig. 3-2 is between the moving piston and its cylinder. The engine

produces useful power by burning the mixture of petrol and air in the space above

the piston, using the increased pressure resulting from combustion to force the

piston down, thereby turning the crankshaft. In the case of the piston, there is no

rotation about its own axis and the seal is required to slide up and down the

cylinder.

The seals in this particular case are known as PISTON RINGS. They must

operate under very severe conditions of temperature and pressure, with very poor

lubrication. They are very often made of good qualityCAST IRO N which, due to its

high carbon content, possesses good self-lubricating properties.


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Figu r e 3-6 Left : A real-life piston about to be inserted into its cylinder. Three

piston rings are visible, the upper ring being a COMPRESSION RING, the middle ring

a second COMPR ESSION RING and the lower slotted ring an OIL CONTROL RING .

Right: Illustrations of two ways in which the oil control ring returns excess oil tothe engine sump.http://courses.washington.edu/engr100/Section_Wei/engine/UofWindsorManual/Graphics/Piston%20Rings.jpg

Figu r e 3-7 A piston with three ring grooves and the three rings which fit into

those grooves. The lower oil-control ring appears to be of the composite type,

comprising two thin steel rings with a wavy steel segment between the two. The

wavy segment is a commonly used method to ensure the oil-control ring fills the full

width of the ring groove, since sideways clearance is known to cause an engine toburn oil. https://reader009.{domain}/reader009/html5/0410/5acba9a4a5c54/5acba9a9a61e5.jpg
http://courses.washington.edu/engr100/Section_Wei/engine/UofWindsorManual/Graphics/Piston%20Rings.jpghttp://courses.washington.edu/engr100/Section_Wei/engine/UofWindsorManual/Graphics/Piston%20Rings.jpghttp://www.cbperformance.com/catalogimages/1060.jpghttp://www.cbperformance.com/catalogimages/1060.jpghttp://www.cbperformance.com/catalogimages/1060.jpghttp://courses.washington.edu/engr100/Section_Wei/engine/UofWindsorManual/Graphics/Piston%20Rings.jpg


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The piston rings actually serve two purposes: theys ea lthe compressed gas

mixture above the piston; and theys c rape the oil present in the lower part of the

engine from the cylinder wall. Without the second function, the engine would

rapidly burn its lubricating oil. The lower piston rings are sometimes referred to as

OIL CONTROL rings or SCRAPER rings, whilst the top ones are called COMPRESSION

rings. Oil rings are designed with wide slots so that oil scraped from the cylinder

wall has a clear return path to the lower part of the engine (refer to Fig 3-6 right).

As previously mentioned, compression rings are usually made from cast iron. Oil-

control rings also can be made of cast iron, but are sometimes made of heat-treated

and tempered steel segments, several of which are put together to form one oil

control ring, as seen in Fig 3-7.

The design of compression rings is such that gas pressure is admitted to the

space behind the ring. This gas pressure significantly increases the pressure of the

piston ring against the cylinder wall and greatly assists the gas-sealing process. Asimilar feature will be noted when discussing O-rings later in this document.

2.1.3 Metal-to-metal joints

Figure 3-2 also gives an example of another type of sealing function. The inlet

VALVE shown at the top of the engine, usually described as a POP PE T VALVE , is

required to move down at predetermined times in the engine cycle to admit the

petrol-air mixture to the cylinder. For the remainder of the engine cycle, the valve

must prevent the same gas mixture from escaping. To do this, the VALVE FACE is

held in contact with its VALVE SE AT by a spring. The valve face and the seat are

both machined to the same angle of taper, often 45. The resulting METAL-TO -

METAL J OINT is adequately gas-tight.

The valve is caused to open intermittently to admit a fresh petrol-air charge,

using a CAM on a rotating shaft called a CAMSHAFT. Details of the camshaft are not

shown in Fig 3-2.

If carefully and accurately machined, metal-to-metal joints perform quite

satisfactorily in many engineering applications, e.g. the top and bottom sections of

some water and air valve bodies (see gate and globe valves later in this document)

are screwed together and seal with a metal-to-metal joint. Many pipe fittings, asdiscussed later in this document, also use this principle.

2.1.4 Gaskets

Figure 3-2 shows two examples of joints where there is no movement between the

two parts. At the top left of the figure, the fuel/air inlet pipe is joined to the top

section of the engine which is called the CYLINDE R H EAD, with the joint sealed by a

GASKET. The second example in Fig. 3-2 is the larger and more critical joint

between the CYLINDER and the CYLINDE R HE AD. In these joints, a reasonably

compliant piece of flat material, called a GASKET, is placed between the two


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components before they are bolted together. The function of the gasket is to

conform to any surface irregularities or slight misalignment between the two

surfaces and thereby to provide a complete seal.

Gaskets are generally of reasonably complex shape, although they are usually

made from sheet material of uniform thickness. Often the bolts which secure the

joint members pass through holes in the gasket, and the gasket usually covers the

entire surface to be joined.

Figu r e 3-8 Examples of gaskets, cut from flat sheet material.

Those illustrated on the left are probably for applications like joining two lengths of

pipe together by flanges while those on the right are from a number of different

applications, including three rubber seals at lower right. The type of material varies

according to the gasket application. In former days, various forms of asbestos was

frequently used but has been replaced by a number of proprietary materials.http://www.americansealandpacking.com/sheetgasketing.htm

http://www.americansealandpacking.com/cutgaskets&sheet.htm

Gaskets are often made of special paper-like or cardboard-like material of the

general type seen in Fig 3-8, but are sometimes made of soft ductile metals like

copper or aluminium. Cork, used in earlier years, is seldom used now.

COMPOSITE GASKETS were popular for many years for difficult sealing tasks,but are now often superseded by less expensive construction combined with sealing

compounds. One popular composite gasket used two thin sheets of copper with an

asbestos interlayer to seal the cylinder heads of automotive and other engines. The

use of asbestos is, of course, no longer permitted.

In Fig. 3-2, the inlet pipe gasket would probably be made from a thick paper-

like or thin cardboard-like material. In former times, the cylinder head gasket

might have been a copper-asbestos composite gasket. In modern production

engines, it will probably still be of composite construction, such as the gaskets seen

in Fig 3-9, the greater part of which will be made of a special heat resisting

proprietary compound, the composition of which is not made public, reinforced

with metal rings in critical locations.
http://www.americansealandpacking.com/sheetgasketing.htmhttp://www.americansealandpacking.com/sheetgasketing.htmhttp://www.americansealandpacking.com/cutgaskets&sheet.htmhttp://www.americansealandpacking.com/cutgaskets&sheet.htmhttp://www.americansealandpacking.com/cutgaskets&sheet.htmhttp://www.americansealandpacking.com/sheetgasketing.htm


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Figu r e 3-9 Examples of modern composite cylinder-head gaskets using fibrous

material for the bulk of the gasket with metal or other reinforcing rings at critical

locations. http://www.automotive-technology.com/contractors/accessories/rajdhani/

Figur e 3-10 Examples of gaskets for such applications as oil pans (sumps) and

valve covers of motor vehicle engines. Some such gaskets are made from carefully

chosen polymer. http://www.automotive-technology.com/contractors/accessories/rajdhani/

Figur e 3-11 Examples of modern gaskets for inlet and exhaust manifolds of motor

vehicle engines. Steel reinforcing rings are commonly used in critical locations.http://www.automotive-technology.com/contractors/accessories/rajdhani/
http://www.automotive-technology.com/contractors/accessories/rajdhani/http://www.automotive-technology.com/contractors/accessories/rajdhani/http://www.automotive-technology.com/contractors/accessories/rajdhani/http://www.automotive-technology.com/contractors/accessories/rajdhani/http://www.automotive-technology.com/contractors/accessories/rajdhani/http://www.automotive-technology.com/contractors/accessories/rajdhani/http://www.automotive-technology.com/contractors/accessories/rajdhani/http://www.automotive-technology.com/contractors/accessories/rajdhani/http://www.automotive-technology.com/contractors/accessories/rajdhani/


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2.1.5 Sealing washers

The spark plug at the top of the engine in Fig. 3-2 is screwed into the cylinder head

using a standard V thread. It is possible to seal the spark plug by a metal-to-metal

joint (generally using a conical seat), and this is done on many late-model engines,

but the seal has traditionally been made by a gasket of simple annular shape, suchas that seen in Fig 3-12 left, which is then called a SEALING WASH ER . A sealing

washer will also be used on the sump-drain plug in Fig. 3-2, which allows the oil to

be drained when necessary.

Figur e 3-12 Left : A sealing washer made from sheet copper filled with some sort

of fibrous material which compresses when the washer is subjected to loading.

Right: Specialised composite sealing washers made from the various materialsindicated.http://www.google.com.au/search?client=safari&rls=en&q=copper+asbestos+gasket+pictures&ie=

UTF-8&oe=UTF-8&redir_esc=&ei=-v6eS-3rPM6IkAXNmoG5DA

http://www.calchiefs.org/%5Citems%5CEMS_Sealing_Washer.jpg

2.1.6 O-rings

An O-RING is a special sealing component which provides a very effective seal for a

wide range of operating conditions. Its use in industry is now so widespread that it

deserves special mention.O-rings consist of an annulus of solid circular cross-section. They are usually

made from synthetic rubbers of various types, to resist oils, acids, bases, solvents,

etc, and the effects of temperature. Square-section O-rings are made for special

applications, e.g. piston seals in disc-brake calipers on motor cars.
http://www.google.com.au/search?client=safari&rls=en&q=copper+asbestos+gasket+pictures&ie=UTF-8&oe=UTF-8&redir_esc=&ei=-v6eS-3rPM6IkAXNmoG5DAhttp://www.google.com.au/search?client=safari&rls=en&q=copper+asbestos+gasket+pictures&ie=UTF-8&oe=UTF-8&redir_esc=&ei=-v6eS-3rPM6IkAXNmoG5DAhttp://www.google.com.au/search?client=safari&rls=en&q=copper+asbestos+gasket+pictures&ie=UTF-8&oe=UTF-8&redir_esc=&ei=-v6eS-3rPM6IkAXNmoG5DAhttp://www.calchiefs.org/%5Citems%5CEMS_Sealing_Washer.jpghttp://www.calchiefs.org/%5Citems%5CEMS_Sealing_Washer.jpghttp://www.calchiefs.org/%5Citems%5CEMS_Sealing_Washer.jpghttp://www.google.com.au/search?client=safari&rls=en&q=copper+asbestos+gasket+pictures&ie=UTF-8&oe=UTF-8&redir_esc=&ei=-v6eS-3rPM6IkAXNmoG5DAhttp://www.google.com.au/search?client=safari&rls=en&q=copper+asbestos+gasket+pictures&ie=UTF-8&oe=UTF-8&redir_esc=&ei=-v6eS-3rPM6IkAXNmoG5DA


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Figur e 3-13 Top: Examples of some O-rings which are commercially available.

The colour of the material is often used to indicate its composition and therefore its

properties.Low er: The correct use of an O-ring in its machined groove in a shaft or

piston. The O-ring must be deformed from its circular cross-section if it is to be aneffective seal.http://www.americansealandpacking.com/orings.htm

http://www.americansealandpacking.com/O-Rings/Design/2.html

http://commons.wikimedia.org/wiki/File:FloDynamix_O-Rings.jpg

O-rings are often used in static sealing applications (i.e. as gaskets) as well as

the sealing arrangement of Fig 3-14 below. They are often used to seal a

reciprocating piston in a hydraulic machine. O-rings are not usually used where

one of the components rotates.
http://www.americansealandpacking.com/orings.htmhttp://www.americansealandpacking.com/orings.htmhttp://www.americansealandpacking.com/O-Rings/Design/2.htmlhttp://www.americansealandpacking.com/O-Rings/Design/2.htmlhttp://commons.wikimedia.org/wiki/File:FloDynamix_O-Rings.jpghttp://commons.wikimedia.org/wiki/File:FloDynamix_O-Rings.jpghttp://commons.wikimedia.org/wiki/File:FloDynamix_O-Rings.jpghttp://www.americansealandpacking.com/O-Rings/Design/2.htmlhttp://www.americansealandpacking.com/orings.htm


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Figur e 3-14 An illustration of an O-ring groove which has been machined too

large for the chosen size O-ring. Pressure can thereby by-pass the O-ring.http://www.americansealandpacking.com/O-Rings/1.html

Figur e 3-15 Illustration of the behaviour of an O-ring under excessive pressure.

Note how the applied pressure, within the O-rings rated pressure range, assists in

sealing process.http://commons.wikimedia.org/wiki/File:FloDynamix_O-Rings.jpg
http://www.americansealandpacking.com/O-Rings/1.htmlhttp://www.americansealandpacking.com/O-Rings/1.htmlhttp://commons.wikimedia.org/wiki/File:FloDynamix_O-Rings.jpghttp://commons.wikimedia.org/wiki/File:FloDynamix_O-Rings.jpghttp://commons.wikimedia.org/wiki/File:FloDynamix_O-Rings.jpghttp://www.americansealandpacking.com/O-Rings/1.html


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If an O-ring is to be successfully used as a seal, it must be located in a specially

machined recess or groove, which must be machined to quite small tolerances. This

may add to the cost of the component. With O-ring seals, the pressure of the fluid

being sealed helps to press the O-ring against its groove (Fig 3-15), thereby

contributing to its sealing effect. The use of fluid pressure in this way is similar to

that described for piston compression rings. Fig 3-14 illustrates the lack of sealing

which may occur when the groove is not of the correct size.

Figur e 3-16 As seen by referring to Item 5 of the exploded view of a vacuum pump

from a diesel truck, O-rings can be used as gaskets. Note that the two Items 10 of

sealing-washer like construction are also referred to as O-rings, so terminology is

not always precise.Mazda T2600 Workshop Manual, 6/89, page P24.


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2.1.7 Further examples

For more information on gaskets, sealing rings and O-rings, go to

http://www.iqsdirectory.com/gaskets/or other websites.

3 Pipes and Pipe FittingsWhilst dealing with seals in general, it is appropriate to make at least some mention

of a different area of sealing joining pipes in a leakproof fashion.

One point to ponder is the multiplicity of pipe jointing methods which have

been used at various times and for various purposes. Why are there so many

different systems in use? The answer probably lies in the wide range of pipe

applications, from small bore, light duty plastic, through copper and steel pipe in

various sizes up to say 25 mm, on to large, high-pressure steel pipes.

3.1 Plastic pipes

Figur e 3-17 Plastic pipes are now being joined successfully using material-specific

adhesives. PVC rainwater and wastewater pipes are a good example of this type.

The pipes to be joined are simply cut square and to length, treated with primer, then

smeared with PVC adhesive and pushed together. The adhesive grips after just a

few seconds and forms a strong permanent joint.http://www.rd.com/advice-and-know-how/stepbystep-pictures-and-instructions-for-gluing-and-

joining-plastic-pvc-pipe/article118256-3.html#slide
http://www.iqsdirectory.com/gaskets/http://www.iqsdirectory.com/gaskets/http://www.rd.com/advice-and-know-how/stepbystep-pictures-and-instructions-for-gluing-and-joining-plastic-pvc-pipe/article118256-3.html#slidehttp://www.rd.com/advice-and-know-how/stepbystep-pictures-and-instructions-for-gluing-and-joining-plastic-pvc-pipe/article118256-3.html#slidehttp://www.rd.com/advice-and-know-how/stepbystep-pictures-and-instructions-for-gluing-and-joining-plastic-pvc-pipe/article118256-3.html#slidehttp://www.rd.com/advice-and-know-how/stepbystep-pictures-and-instructions-for-gluing-and-joining-plastic-pvc-pipe/article118256-3.html#slidehttp://www.rd.com/advice-and-know-how/stepbystep-pictures-and-instructions-for-gluing-and-joining-plastic-pvc-pipe/article118256-3.html#slidehttp://www.iqsdirectory.com/gaskets/


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3. 2 Copper pipes

Joining of many copper and steel pipes is achieved by variations of metal to metal

joints, in which the surfaces are clamped tightly together (compressed), often taking

advantage of the self-centring and wedging action of opposing conical surfaces.

Figur e 3-18 Left : A joint between a brass T-piece and three copper pipes. This

type of joint is sometimes referred to as a DOUBLE CONE COMPRE SSION fitting. In

the left-hand photograph, sealing of each pipe is achieved by an OLIVE, a ring ofbrass which looks somewhat like a wedding ring, which slips over the pipe and is

compressed when the nut is tightened to seal the joint. Right: The right-hand

diagram indicates the mode of compression between the union and the nut. That

diagram is incorrectly drawn - the bulge in the pipe is actually the separate OLIVE,

as seen in the left-hand photograph, but the principle of compression between the

two conical surfaces is correctly drawn.http://www.diydoctor.org.uk/project_images/copper_compression_joints/Compression%20T%20j

unction.jpg

Nylon tubes are often joined by a fitting similar to that described in Fig 3-18.

The loose piece or OLIVE which is slipped onto the pipe may be made of plastic or

metal, depending on the application. Its function is to clamp tightly onto the

outside diameter of the pipe as it is squeezed between the two screwed fittings.
http://www.diydoctor.org.uk/project_images/copper_compression_joints/Compression%20T%20junction.jpghttp://www.diydoctor.org.uk/project_images/copper_compression_joints/Compression%20T%20junction.jpghttp://www.diydoctor.org.uk/project_images/copper_compression_joints/Compression%20T%20junction.jpghttp://www.diydoctor.org.uk/project_images/copper_compression_joints/Compression%20T%20junction.jpghttp://www.diydoctor.org.uk/project_images/copper_compression_joints/Compression%20T%20junction.jpg


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Figur e 3-19 A further example of a compression fitting using an OLIVE , here

referred to as a FERRULE.http://www.managemylife.com/mmh/articles/authored/using-compression-fittings

Figu r e 3 -20 In this fitting, the end of the pipe, which may be either copper or

steel, is FLARED to a conical shape. The conical section is then clamped between

conical sections of the body and nut.http://machinedesign.com/content/hydraulic-tube-fittings2-0602
http://www.managemylife.com/mmh/articles/authored/using-compression-fittingshttp://www.managemylife.com/mmh/articles/authored/using-compression-fittingshttp://machinedesign.com/content/hydraulic-tube-fittings2-0602http://machinedesign.com/content/hydraulic-tube-fittings2-0602http://machinedesign.com/content/hydraulic-tube-fittings2-0602http://www.managemylife.com/mmh/articles/authored/using-compression-fittings


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Figu r e 3 -21 This connection is a variation on the olive type, using a shaped

FERRULE with a sharp conical section to wedge onto the pipe. Note the black O-ring

on the left-hand end of the connection to seal the thread.http://machinedesign.com/content/hydraulic-tube-fittings3-0602

Figu r e 3 -22 An O-ring in a machined recess in the body of the joint is compressed

to form a FACE SEAL. Note the O-ring on the thread on the right-hand end to

prevent leakage from the thread.http://machinedesign.com/content/hydraulic-tube-fittings4-0602
http://machinedesign.com/content/hydraulic-tube-fittings3-0602http://machinedesign.com/content/hydraulic-tube-fittings3-0602http://machinedesign.com/content/hydraulic-tube-fittings4-0602http://machinedesign.com/content/hydraulic-tube-fittings4-0602http://machinedesign.com/content/hydraulic-tube-fittings4-0602http://machinedesign.com/content/hydraulic-tube-fittings3-0602


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Figu r e 3 -23 The 60 cone fitting again uses a metal to metal seal with the conical

section to centre the components and increase the clamping force.http://machinedesign.com/content/hydraulic-tube-fittings5-0602

Figu r e 3 -24 Using a straight thread, there is a leak path along the helix of the

thread. Sealing is achieved by an O-ring in a machined recess. The recess prevents

the O-ring from being forced out under pressure.http://machinedesign.com/content/hydraulic-tube-fittings6-0602
http://machinedesign.com/content/hydraulic-tube-fittings5-0602http://machinedesign.com/content/hydraulic-tube-fittings5-0602http://machinedesign.com/content/hydraulic-tube-fittings6-0602http://machinedesign.com/content/hydraulic-tube-fittings6-0602http://machinedesign.com/content/hydraulic-tube-fittings6-0602http://machinedesign.com/content/hydraulic-tube-fittings5-0602


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Figu r e 3 -25 In this design, sealing is achieved by the tapered thread on the fitting

wedging into the straight thread in the housing. It is common practice to apply a

small quantity of sealant such as Loctite to ensure complete sealing.http://machinedesign.com/content/hydraulic-tube-fittings7-0602

Figu r e 3 -26 Some of the range of brass fittings available for different applications.http://machinedesign.com/content/hydraulic-tube-fittings-0602

Students interested in learning more about pipe fittings and joints will find

useful information athttp://machinedesign.com/article/hydraulic-tube-fittings-deliver-leak-free-performance-and-long-life-0602.
http://machinedesign.com/content/hydraulic-tube-fittings7-0602http://machinedesign.com/content/hydraulic-tube-fittings7-0602http://machinedesign.com/content/hydraulic-tube-fittings-0602http://machinedesign.com/content/hydraulic-tube-fittings-0602http://machinedesign.com/article/hydraulic-tube-fittings-deliver-leak-free-performance-and-long-life-0602http://machinedesign.com/article/hydraulic-tube-fittings-deliver-leak-free-performance-and-long-life-0602http://machinedesign.com/article/hydraulic-tube-fittings-deliver-leak-free-performance-and-long-life-0602http://machinedesign.com/article/hydraulic-tube-fittings-deliver-leak-free-performance-and-long-life-0602http://machinedesign.com/article/hydraulic-tube-fittings-deliver-leak-free-performance-and-long-life-0602http://machinedesign.com/article/hydraulic-tube-fittings-deliver-leak-free-performance-and-long-life-0602http://machinedesign.com/content/hydraulic-tube-fittings-0602http://machinedesign.com/content/hydraulic-tube-fittings7-0602


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Figu r e 3 -27 Relatively new fittings known as Sharks teeth, in which the pipe to be

joined and sealed is simply pushed into the fitting. The teeth visible inside the

fittings grip the pipe to prevent it slipping out under pressure and the rubber

provides a seal. http://www.copper.com.au/cdc/article.asp?CID=49&AID=288

3.3 Steel pipes

Steel pipes bring jointing problems which are different from copper pipes. Sizes

may be much larger, the material is harder and stronger, hence the pressures to besealed may be much greater. Several different jointing methods are available,

including threaded pipe ends screwed into threaded sleeves, sealed by sealant such

as Loctite or, in past years, red lead. Flanges may be either screwed or welded to

the pipe, and may be sealed by either gaskets or O rings.

Figu r e 3 -28 Some examples of methods of attaching flanges to steel pipes by

welding or threading.

http://www.google.com.au/imgres?imgurlhttp://www.wermac.org/flanges/flanges_general_part3.html
http://www.copper.com.au/cdc/article.asp?CID=49&AID=288http://www.copper.com.au/cdc/article.asp?CID=49&AID=288http://www.google.com.au/imgres?imgurlhttp://www.google.com.au/imgres?imgurlhttp://www.wermac.org/flanges/flanges_general_part3.htmlhttp://www.wermac.org/flanges/flanges_general_part3.htmlhttp://www.wermac.org/flanges/flanges_general_part3.htmlhttp://www.google.com.au/imgres?imgurlhttp://www.copper.com.au/cdc/article.asp?CID=49&AID=288


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Steel pipes frequently have long "runs", i.e. long overall lengths formed by

joining a number of standard lengths of pipe together. This may cause two

problems. First, if the temperature of the pipe changes (due to the fluid flowing

through it, e.g. steam) the pipe length may change significantly and provision must

be made for expansion and contraction. Secondly, it is prudent to design the

pipeline and its fittings so that maintenance can be carried out easily, e.g. can one

leaking joint be repaired without dismantling the whole pipeline?

Figu r e 3 -29 Some years ago, the School of Mechanical and Manufacturing

Engineering updated its fire hose equipment. The new system uses 100 mm

galvanised steel mains. Joints are formed by split clamps which locate into

machined recesses close to the end of each pipe. Standard pipe lengths come on-

site with these recesses already machined. However, where a pipe needs to be cut to

length, a new recess can be machined on-site. Sealing of the joint is achieved by a

special rubber seal, held in place by the split clamps. An example of this type of

fitting, trade marked VICTAULIC, is on view in the Laboratory.

http://www.power-technology.com/contractors/thermal_insulation/victaulic/victaulic1.html
http://www.power-technology.com/contractors/thermal_insulation/victaulic/victaulic1.htmlhttp://www.power-technology.com/contractors/thermal_insulation/victaulic/victaulic1.htmlhttp://www.power-technology.com/contractors/thermal_insulation/victaulic/victaulic1.html


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Note some of the advantages of the Victaulic system for fire hose installation.

1. Pipes have no protrusions and pass readily through 100 mm clearance holes

drilled in concrete floors, etc. (cf. pipes with welded-on flanges).

2. Any individual section of pipe can be removed without disturbing the rest of theline.

3. Pipe lengths can be cut on-site to suit the job in hand.

4. Sealing is simply and effectively achieved by the rubber seals.

5. The pipe lengths do not abut and there is sufficient axial space to cater for

longitudinal expansion and contraction.

Figu r e 3-30 Fittings of a type generally used on steel pipes for very high pressure

applications, e.g. supplying fuel to engine injectors in diesel engines. The ends of

the pipes are SWAGED to form external cones, which make metal-to-metal joints in

internal cones. https://reader009.{domain}/reader009/html5/0410/5acba9a4a5c54/5acba9b84eaf4.jpg

4 ValvesVALVES are used to control the flow of fluids in hydraulic and pneumatic systems.

Many systems which might appear to be purely mechanical actually have hydraulic

or mechanical sub-systems using valves, so that valves are an important group of

mechanical engineering components. For example, the engine sketched in Fig. 3-1

3-2 has a valve to admit the petrol/air mixture to the cylinder at the proper time.

This particular valve is called a POP PE T VALVE . The engine will also have a

carburettor which incorporates a TH ROTTLE VALVE to control engine speed. The
http://news.thomasnet.com/images/large/453/453814.jpghttp://news.thomasnet.com/images/large/453/453814.jpghttp://news.thomasnet.com/images/large/453/453814.jpg


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P3-27

lubrication system on the same engine (not shown in Fig. 3-1) will have an oil pump

and a PRE SSURE R ELIEF VALVE to ensure that the oil pressure cannot exceed a safe

level. As a further example, the automatic transmissions fitted to many cars are

hydraulic devices which use a number of carefully designed valves to change the

drive ratios to suit driving conditions.

4.1 Types of valve

It is perhaps worth summarising the different functions performed by the main

classes of valves which are generally available.

F u n c t i o n E x a m p l e s

1. Off-on Gate valve

Globe valve

Poppet valve

2. Regulating Globe valve

Butterfly valve

Needle valve

3. Non-return Flap valve

Ball valve

4. Safety Spring valve

Deadweight valve

5. Pressure stabilising Pressure relief valve

Pressure regulating valve


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4.1.1 Gate valves

Figu r e 3-31 Gate valves are made in both small and large sizes, up to the size used

on large water mains. A characteristic is that, when the valve is open, the GATE

which is the green component in the right-hand diagram is withdrawn completely

from the flow path, so unobstructed flow is obtained and there is little pressure loss

through the valve. Gate valves are generally intended to be either fully closed orfully open. They are generally not used for flow regulation. Note also the use of

another type of seal, the PACKING on the valve spindle to prevent leakage from the

top of the bonnet. If the packing wears and begins to leak, there is provision to

squeeze it down to renew its sealing effect. Note also that the packing is not

subjected to fluid pressure when the valve is closed.http://www.brassvalve-manufacturers.com/photo/828055e2f390bad6c890604ffe04fb68/Gate-

Valves.jpg
http://www.brassvalve-manufacturers.com/photo/828055e2f390bad6c890604ffe04fb68/Gate-Valves.jpghttp://www.brassvalve-manufacturers.com/photo/828055e2f390bad6c890604ffe04fb68/Gate-Valves.jpghttp://www.brassvalve-manufacturers.com/photo/828055e2f390bad6c890604ffe04fb68/Gate-Valves.jpghttp://www.brassvalve-manufacturers.com/photo/828055e2f390bad6c890604ffe04fb68/Gate-Valves.jpghttp://www.brassvalve-manufacturers.com/photo/828055e2f390bad6c890604ffe04fb68/Gate-Valves.jpg


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4.1.2 Globe valves

Figu r e 3-32 Globe valves take their name from their shape, which is required to

allow the valve disc to be moved into contact with its seat to shut off the flow.

The construction results in some impediment to flow and some pressure loss

through the valve. These valves are often used for flow regulation. A common

example is the garden tap. Note the need for packing on the valve spindle to

prevent leakage from the top of the valve bonnet, and the provision of a means of

squeezing the worn packing to renew the seal.http://www.energy.gov.kw/data/site1/images/doha/Illustrations/globe%20Valve.gif

Figu r e 3 -33 Further examples of globe valves. They are designed for flow only in

the direction shown. Since the disc or plug may be mounted on a ball or spherical

surface so that it can conform to its seat, the flow may become unstable if it is

reversed.http://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/6/1/Fig_6_1_2.gif
http://www.energy.gov.kw/data/site1/images/doha/Illustrations/globe%20Valve.gifhttp://www.energy.gov.kw/data/site1/images/doha/Illustrations/globe%20Valve.gifhttp://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/6/1/Fig_6_1_2.gifhttp://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/6/1/Fig_6_1_2.gifhttp://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/6/1/Fig_6_1_2.gifhttp://www.energy.gov.kw/data/site1/images/doha/Illustrations/globe%20Valve.gif


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4.1.3 Poppet valves

Figu r e 3-34 Left : An example of a valve assembly from an automotive engine.

This is similar to the POP PE T VALVE shown in Fig 3-2. For most of the engine cycle,

the spring holds the valve tightly in metal-to-metal contact with its seat. When the

valve is required to open to admit air and fuel or to discharge exhaust gases, the end

of the valve is pushed downwards by a CAM .

FOR KEEN STUDENTS

Fig 3-34 Right: Two poppet valves showing the cam mechanism used to open the

valves by means of a rotating CAMSHAFT. This illustration is a desmodromic

mechanism used in some high speed engines to positively control both the openingand closing of the valve. If normal engines are driven at too high a speed, valve

springs cannot control the inertia forces quickly enough and the valve does not close

quickly enough. This is called VALVE FLOAT or VALVE BOU NCE .http://www.google.com.au/search?client=safari&rls=en&q=poppet+valve+pictures
http://www.google.com.au/search?client=safari&rls=en&q=poppet+valve+pictureshttp://www.google.com.au/search?client=safari&rls=en&q=poppet+valve+pictureshttp://www.google.com.au/search?client=safari&rls=en&q=poppet+valve+pictures


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4.1.4 Butterfly valves

Figu r e 3-35 Examples of small butterfly valves used in automotive carburettors.

Depressing the accelerator opens the valve and a spring automatically closes the

valve when the accelerator is released. Butterfly valves are usually circular discs,although they can be square with rounded corners.http://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_16.html

http://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_36.htm

http://en.wikipedia.org/wiki/Valve

Figu r e 3-36 Large butterfly valves used on water mains and similar applications.

Used for flow regulation, they cause little pressure drop when fully open.
http://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_16.htmlhttp://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_16.htmlhttp://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_36.htmhttp://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_36.htmhttp://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Valvehttp://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_36.htmhttp://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_16.html


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4.1.5 Needle valves

http://www.sealexcel.com/gifs/needle-v.gif

http://www.tubefittings.in/valve-fittings.html

http://www.google.com.au/imgres?

Figu r e 3 -37 Examples ofNEEDLE VALVES which are usually used for precise

regulation of small flows, usually by screw adjustment of a tapered needle.
http://www.sealexcel.com/gifs/needle-v.gifhttp://www.sealexcel.com/gifs/needle-v.gifhttp://www.tubefittings.in/valve-fittings.htmlhttp://www.tubefittings.in/valve-fittings.htmlhttp://www.google.com.au/imgreshttp://www.google.com.au/imgreshttp://www.google.com.au/imgreshttp://www.tubefittings.in/valve-fittings.htmlhttp://www.sealexcel.com/gifs/needle-v.gif


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4.1.6 Safety valves

http://en.wikipedia.org/wiki/File:Deadweight_safety_valve_section_(Heat_Engines,_1913).jpg

http://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/9/1/fig9_1_2.gif

Figu r e 3-38 Top: ADEAD -W EIGH T SAFETY VALVE in which the force from the

pressure acting over the small inner pipe area must exceed the dead weight for the

valve to open and release pressure. Bottom : SPR ING SAFE TY VALVES in which thedead weights have been replaced by a metal spring.
http://en.wikipedia.org/wiki/File:Deadweight_safety_valve_section_(Heat_Engines,_1913).jpghttp://en.wikipedia.org/wiki/File:Deadweight_safety_valve_section_(Heat_Engines,_1913).jpghttp://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/9/1/fig9_1_2.gifhttp://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/9/1/fig9_1_2.gifhttp://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/9/1/fig9_1_2.gifhttp://en.wikipedia.org/wiki/File:Deadweight_safety_valve_section_(Heat_Engines,_1913).jpg


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Students are sometimes confused over the two quite distinct functions ofSAFETY

VALVES and PRE SSURE R ELIEF VALVES . A safety valve is a precaution against an

unforeseen or unlikely failure. For example, if the pressure in a boiler should ever

rise to a dangerous level, the SAFE TY VALVE will operate automatically and allow the

pressure to drop to a safe level. The safety valve operates only in an emergency and

may never operate within the life of the boiler.

4.1.7 Pressure relief valves

Pressure relief valves are designed to open automatically at a pre-determined level

of system pressure and to regulate system pressure at that level despite changes the

system operating conditions.

Figu r e 3-39 An application of a pressure relief valve used in an automotive

engine. The diagram shows an OIL PUMP , used to provide oil under pressure to

engine bearings of a light truck engine. Oil is drawn into the pump through the

strainer, with the strainer located at the bottom on the ENGINE SUMP , also called

the OIL PAN . If the pressure from the pump exceeds set limits, the SPRING RELIEF

VALVE opens and drops the pressure.Toyota 4YE Engine Repair Manual, August 1985, page LU8

Consider the oil pump shown in Fig 3-39. This pump must provide a flow of oil

to lubricate the engine bearings under all operating conditions. When the oil is very

hot, its viscosity drops, so that it flows very easily through the bearings. The pumpmust therefore be designed to have a large flow rate. When the engine is first

started, the oil is cold, its viscosity is relatively high and it does not flow easily

through the bearings. Since the pump still has a large flow rate, the pressure under

these conditions may rise high enough to damage the pump. This risk is overcome

by providing a PRE SSURE R ELIEF VALVE to open at a pre-set pressure. This is not

an emergency procedure; it is part of the valve's normal function.


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Figu r e 3 -40 Spring loaded pressure relief valves.http://1.bp.blogspot.com/_YOjepBEvjc8/RtFJB1RGcKI/AAAAAAAAAfk/KxnSkQyz5ww/s320/valve101.gif

http://www.google.com.au/imgres?imgurl=http://www.valve-world.net/images/specials/srv/2_fig2.gif

The simplest and most reliable type of pressure relief valve is the spring-loaded

design (Fig 3-40) where a spring force opposes the system pressure acting on the

area of the valve disc. Valves of this type may be used to control the pressure ofsystems using either liquids or gases.

When the system pressure rises sufficiently, it overcomes the spring force and

the valve opens to reduce the pressure by allowing some of the flow to be dumped

through the outlet pipe to a storage tank or, in the case of a compressed air system,

vented to atmosphere.

It is usual to provide a means ofSETTING or adjusting the spring pressure so

that the same valve can be used for a variety of applications.
http://1.bp.blogspot.com/_YOjepBEvjc8/RtFJB1RGcKI/AAAAAAAAAfk/KxnSkQyz5ww/s320/%0bvalve101.gifhttp://1.bp.blogspot.com/_YOjepBEvjc8/RtFJB1RGcKI/AAAAAAAAAfk/KxnSkQyz5ww/s320/%0bvalve101.gifhttp://www.google.com.au/imgres?imgurl=http://www.valve-world.net/images/specials/srv/2_fig2.gifhttp://www.google.com.au/imgres?imgurl=http://www.valve-world.net/images/specials/srv/2_fig2.gifhttp://www.google.com.au/imgres?imgurl=http://www.valve-world.net/images/specials/srv/2_fig2.gifhttp://1.bp.blogspot.com/_YOjepBEvjc8/RtFJB1RGcKI/AAAAAAAAAfk/KxnSkQyz5ww/s320/%0bvalve101.gif


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FOR KEEN STUDENTS

4.1.8 Pressure regulating valves

Figur e 3-41: A schematic diagram 2 of the layout of a p r e s s u r e

r egula t in g va lve used on hydraulic systems.

J. Carvill, The Student Eng ineer's Com pan ion, Butterworths, 1980. page

35.

This type of valve does much more than the simple pressure relief valves of

Figs 3-39 and 3-40. Oil at unregulated pressure enters the inlet port of the

valve. If the pressure is higher than the set pressure, some of the oil can be

discharged back to the storage tank, dropping the outlet pressure.

Dumping oil is achieved by forcing the main piston in the centre of the valve

body to move to the left, off its conical metal-to-metal seat. The desired

outlet pressure is set by adjusting the length of the pilot-valve spring and

hence the force holding the pilot valve onto its seat.

When the valve is working, pressure at the inlet tends to push the main

piston to the left and off its conical seat, but movement is resisted by themain spring tending to push the piston to the right. Inlet pressure is bled

through a small diameter hole in the piston and, if the pressure to the left of

the piston becomes too high, the small pilot valve opens slightly and drops

the pressure in the cavity to the left of the piston. The drop in pressure

causes the main piston to move to the left, causing oil to be discharged to

the tank until the pressure drops to the set pressure. In practice, the system

usually stabilises with a small, slightly varying flow through the pilot valve.

_________________2 This is intended to be a simple diagrammatic illustration of the function of the valve.

You may notice that the valve, as drawn, cannot be assembled because the main piston

cannot be inserted into its bore.


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Figu r e 3 -42 A sectioned view of a commercial pressure regulating valve.

The mode of operation of this valve is less clear than the example in Fig 3-

41. It is based on a diaphragm rather than a pilot valve. The large area ofthe diaphragm means that small pressure variations can easily be detected

and controlled. The set pressure is adjusted by means of the threaded

stem and nut under the top cover.http://www.swagelok.com/regulators/pressure_reducing_regulators.htm
http://www.swagelok.com/regulators/pressure_reducing_regulators.htmhttp://www.swagelok.com/regulators/pressure_reducing_regulators.htmhttp://www.swagelok.com/regulators/pressure_reducing_regulators.htm

Documents

3.General Notes on Engineering Hardware - Seals, Gaskets, Valves