Nonvoting - NFPA · Zone 0, Class I, Zone 1, and Class I, Zone 2 from Section 505-7 in the 1996 NEC into Section 1-3 located after Class I, Division 2 definition to read as follows:

Report of the Committee on

Electrical Equipment in Chemical Atmospheres

R. F. Schwab, Chair Allied-Signal Inc., NJ [U]

Mark C. Ode, Nonvoting Secretary Nat'l Fire Protection Assn., MA

Alonza W. Ballard, Crouse-Hinds, NY [M] Rep. Nat'l Electrical Mfgs. Assn.

Michael K. Baucom, BEBCO Industries, Inc., TX [M] Francis X. Bender, Hazards Research Corp., NJ [SE] Edward M. Briesch, Underwriters Laboratories Inc., IL [RT] Joseph A. Cannatelli, Arco Chemical Co., PA [U]

~ mes DeLuca, Bechtel Corp., CA [SE] illiam T. F'lske, ITS North America, NY [RT]

William G. Lawrence, Jr., Factory Mutual Research Corp., MA [I] Richard C. Masek, Bailey Controls, OH [M] Robert E. McKenney, City of Tacoma, WA [E] John M. Mesina, U.S. Dept. of Labor, WV [E] George W. Moore, Industrial Risk Insurers, CT [I] Richard E. Munson, The DuPont Co., DE [U] Milton H. Ramsey, Chewon U.S.A. Inc., TX [U]

Rep. Inst. of Electrical & Electronics Engr, Inc. Joseph V. Saverino, Air Products and Chemicals, Inc., PA [U] Sukanta Sengupta, FMC Corp., NJ [U] George H. St. Onge, BernardsviUe, NJ [SE] James G. Stallcup, GRAYBOY & Assoc., TX [SE] Ronald J. Strancar, BP Oil Co., OH [U]

Rep. American Petroleum Inst. Dann M. Strube, Lanesville, IN [SE] David Wechsler, Union Carbide Corp., WV [U]

Rep. Chemical Mfrs. Assn. Charles J. Wolf, Teledyne Brown Engr - Energy Systems, MD [SE]

Jack H. Zewe, Electrical Consultants Inc., LA [SE]

Alternates

Jane I. Lataille, Industrial Risk Insurers, CT [I] (Air. to G. W. Moore)

Kerry L. McManama, Underwriters Laboratories Inc., IL [RT] (Alt. to E. M. Briesch)

Robert S. PeUizze, Inchcape Testing Services NA Inc., NY [RT] (Alt. to W. T. Fiske)

James A. Robertson, Dow Chemical Co., TX [U] (Alt. to M. H. Ramsey)

Samuel A. Rodgers, Allied-Signal Inc., VA [U] (Alt. to 1L F. Schwab)

James W. Stallcup, GRAYBOY & Assoc., TX [SE] (Alt. toJ. G. Stallcup)

Nonvoting

Richard Y. LeVine, Stamford, CT (Member Emeritus)

John E. Rogerson, Cedar Lane Farm, OH (Member Emeritus)

Staff Liaison: Mark C. Ode

This list represents the membership at the time the Committee was balloted on the text of this edition. Since that time, changes in the membership may have occurred. A key to classifications is found at the front of the book.

Committee Scope: This Committee shall have primary responsibility for documents on (1) developing data on the properties of chemicals enabling proper selection of electrical eqmpment for use in atmospheres containing flammable gases, vapors or dusts; (2) making recommendations for the prevention of fires and explosions through the use of continuously purged, pressurized, explosion-proof, or dust-ignition-proof electrical equipment where installed in such chemical atmospheres.

This portion of the Technical Committee Report of the Committee on Electrical Equipment in Chemical Atmospheres is presented for adoption in 2 parts.

Part I of this Report on Comments was prepared by the Technical Committee on Electrical Equipment in Chemical Atmospheres, and documents its action on the comments received on its Report on Proposals on NFPA 497A-1992, Recommended Practice for Classification of Class I Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, and incorporates the flammable liquids, gases and vapor information from NFPA 497M-1991, Manual for Classification of Gases, Vapors, and Dusts for Electrical Equipment in Hazardous (Classified) Locations as published in the Report on Proposals for the 1997 Annual Meeting.

This document when adopted will be redesignated, renumbered, and retided to NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas.

Part I of this Report on Comments has been submitted to letter ballot of the Technical Committee on Electrical Equipment in Chemical Atmospheres, which consists of 24 voting members. The results of the balloting, after circulation of any negative votes, can be found in the report~

Part 1I of dais Report on Comments was prepared by the Technical Committee on Electrical Equipment in Chemical Atmospheres, and documents its action on the comments received on its Report on Proposals on NFPA 497B-1991, Recommended Practice for the Classification of Class II Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, and incorporates the combustible dust information from NFPA 497M-1991, Manual for Classification of Gases, Vapors, and Dusts for Electrical Equipment in Hazardous (Classified) Locations, as published in the Report on Proposals for the 1997 Annual Meeting.

This document when adopted will be redesignated, renumbered, and retifled NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas.

part II of this Report on Comments has been submitted to letter ballot of the Technical Committee on Electrical Equipment in Chemical Atmospheres, which consists of 24 voting members. The results of the balloting, after circulation of any negative votes, can be found in the report.

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N F P A 4 9 7 A - - A 9 7 R O C

PART I

(Log #CC3) 497A- 1 - (Entire Documen t ) : Accept SUBMITTER: Technica l Commi t t ee on Electrical E q u i p m e n t in Chemical A tmosphe re s C O M M E N T ON PROPOSAL NO: 497A-15 RECOMMENDATION: (1) Insert the defini t ions for Glass I, Zone 0, Class I, Zone 1, and Class I, Zone 2 f rom Section 505-7 in the 1996 NEC into Section 1-3 located after Class I, Division 2 defini t ion to read as follows:

Class I, Zone 0. A Class I, Zone 0 location is a locat ion (1) in which ignitible concent ra t ions of f l ammable gases or vapors are flpresent continuously;, or (2) in which ignit ible concent ra t ions of

ammab le gases or vapors are p re sen t for long per iods of t ime. Class I, Zone 1. A Class I, Zone 1 location is a location (1) in

which ignitible concent ra t ions of f l ammable gases or vapors are likely to exist u n d e r no rma l opera t ing conditions; or (2) in which ignitible concent ra t ions of f l ammable gases or vapors may exist f requent ly because of repair or m a i n t e n a n c e opera t ions or because of leakage; or (3) in which e q u i p m e n t is opera ted or processes are carried on, of such a na tu re tha t e q u i p m e n t breakdown or faulty opera t ions could result in the release of ignitible concent ra t ions of f l ammable gases or vapors and also cause s imul taneous failure of electrical e q u i p m e n t in a mode to cause the electrical e q u i p m e n t to become a source of ignition; or (4) that is ad jacent to a Class I, Zone 0 location f rom which ignitible concent ra t ions of vapors could be commun ica t ed , unless c o m m u n i c a t i o n is p revented by adequate positive-pressure venti lat ion f rom a source of clean air a n d effective safeguards against venti lat ion failure are provided.

Class I, Zone 2. A Class I, Zone 2 location is a location (1) in which ignitible concent ra t ions of f l ammable gases or vapors are n o t likely to occur in no rma l opera t ion a n d if they do occur will exist only for a shor t period; or (2) in which volatile f l ammable liquids, f l ammable gases, or f l ammable vapors are hand led , processed, or used, bu t in which the liquids, gases, or vapors normal ly are conf ined within closed conta iners or closed systems f rom which they can escape only as a result of accidental rup tu re or breakdown of the conta iners or system, or as the result of the abnorma l opera t ion of the e q u i p m e n t with which the liquids or gases are handled , processed, or used; or (3) in which ignitible concent ra t ions of f l ammable gases or vapors normal ly are prevented by positive mechan ica l venti lat ion, bu t which may become hazardous as the resul t of failure or abnorma l operat ion of the venti lat ion equ ipmen t ; or (4) tha t is ad jacent to a Class I, Zone 1 location, f rom which ignitible concent ra t ions of f l ammable gases or vapors could be commun i ca t ed , unless such c o m m u n i c a t i o n is p reven ted by adequa te positive-pressure venti lat ion f rom a source of clean air, and effective safeguards against venti lat ion failure are provided.

(2) Insert the following Class I, Zone g roup defini t ions into Section 1-3, Definit ions to be located immedia te ly after the Class I Division Groups a n d immedia te ly before the defini t ion of F lammable Liquid to read as follows:

Class I, Zone combust ib le materials are divided into three groups: Group IIC - A tmospheres conta in ing acetylene, hydrogen, or

f l ammable gas, f l ammable l iqu id-produced vapor, or combust ib le l iquid-produced vapor mixed with air tha t may burn or explode having ei ther MESG values less t han or equal to 0.50 m m or MIC ratio less than or equal to 0.45, or gases or vapors of equivalent hazard.

Group I IB-Atmosphe re s conta in ing acetaldehyde, ethylene, or f l ammable gas, f l ammab le l iqu id-produced vapor, or combus t ib le l iquid-produced vapor mixed with air that may bu rn or explode having ei ther MESG values greater than 0.50 m m and less t h e n or equal to 0.90 m m or MIC ratio greater than 0.45 and less than or equal to 0.80.

Group IIA - A tmosphe re s conta in ing acetone, ammon ia , ethyl alcohol, gasoline, me t hane , p ropane , or f l ammable gas, f l ammable l iqu id-produced vapor, or combust ib le l iqu id-produced vapor mixed with air tha t may bu rn or explode having MESG values greater than 0.90 m m or MIC ratio grea ter than 0.80.

These g roups are also ref lected in Table 2-1, as Class I, Zone Groups ."

(3) Insert Class I, Zone 0, 1, a n d 2 text into the l l t h t h r o u g h the 15th line of Section 2-1 o f the rewrite to read as follows:

"The Class I category is fu r the r subdivided into e i ther Class I, Division 1 or Division 2; or Class I, Zone 0, Zone 1, or Zone 2.

(a) Class I, Division 1 in which the combust ib le material is p re sen t normal ly or f requent ly

(b) Class I, Division 2 in which the combust ib le material is p resen t as a resul t of i n f r equen t failure of e q u i p m e n t or conta iners

(c) Class I, Zone 0 in which the combust ib le mater ia l is p resen t cont inuous ly or for long periods.

(d) Class I, Zone 1 in which the combust ib le material is likely to be p resen t normal ly or f requent ly because of repair or ma in tenance opera t ions or because of leakage.

(e) Class I, Zone 2 in which the combust ib le material is no t likely to occur in no rma l opera t ion a n d if it does occur it will exist only fo a shor t period."

(4) Insert "or Class I, Zone 0, Zone 1, or Zone 2," into Section 2-1.3 after "Division 2" and before "are" to read as follows:

2-1.3 For the purpose of this r e c o m m e n d e d practice, areas no t classified e i ther as Class I, Division 1 or Division 2 or Class I, Zone ( Zone 1 or Zone 2, are "unclassified" areas.

(5) Insert "or three Class I, Zone Groups, IIC, IIB, and IIA," into Section 2-4.1" to read as follows:

2-4.1" Combust ible materials are classified into four Class I, Division Groups, A, B, C, and D, or th ree Class I, Zone Groups, IIC lIB, and IIA, d e p e n d i n g u p o n thei r propert ies."

(6) Insert a new co lumn in Table 9-1 between '%rapor Pressure"

and "MIE" with the head ing "Class I Zone Group 8 " with a new note 8 and inc lud ing the following chemical grouping . Aceta ldehyde I IA Acetic Acid I IA Acetone I IA Acetonitr i le I IA Acetylene IIC Acrolein ( Inhibi ted) IIB Acrylonitrile l iB sec-Amyl Acetate IIA A m m o n i a IIA Anil ine IIA Benzene IIA 1,3-Butadiene l iB 1-Butanol I IA 2-Butanol IIA n-Butyl Acetate IIA Carbon Disulfide IIC Carbon Monoxide IIA Crotonaidehyde I I B C u m e n e IIA Cycloh exane I IA Cyclohexanol I IA Cyc lohexanone IIA Cyclopropane IIB p-Cymene I IA o-Dich lorobenzene I IA 1,2-Dichloroethylene I IA Die thylamine I IA Die thy laminoe thano l I IA Diethyl Ether I I B Dime thy iamine I IA 1,4-Dioxane IIB Ethane I IA Ethanol IIA Ethylene IIB Ethylene Oxide IIB Ethyl Acrylate (Inhibi ted) I IA Ethyl Formate I IA n -Hep tane IIA n-H exane I IA Hexano l IIA Hydrogen IIC Hydrogen Cyanide IIB Kerosene 1 IA M e than e I IA Methanol IIA Methyl Acetate I I B Methyl Methacrylate IIA Methylamine I IA M o n e t h a n o l a m i n e I IA Nap tha (Coal Tar) IIA Nap tha (Pet ro leum) IIA Ni t roe thane I IA Ni t rome thane I IA n - N o n a n e IIA Nonyl Alcohol I IA n -Oc tane I IA n-Octyl Alcohol I IA 1-Pentanol IIA Propane IIA 1-Propanol I IA Pyridine IIA Styrene I IA

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N F P A 4 9 7 A ~ A97 R O C

Tet rahydrofuran I I B T o l u e n e IIA Tr ie thylamine IIA Vinyl Acetate IIA Xylene IIA

8 Class I, Zone Groups based upon Electrical appara tus for explosive gas a tmosphe re s - Part 20: Data for f l ammable gases a n d vapors, relating to the use of electrical apparatus , IEC 79-20 (1996) Electrical appara tus for explosive gas a tmosphere .

(7) Insert the Zone 0 area classification informat ion into the paragraph after the title of Chapter 3 to read as follows:

"The decision to classify an area as hazardous is based u p o n the possibility that an ignitible mix ture may occur. Having decided tha t an area shou ld be classified, the nex t step is to de te rmine which classification me thodo logy shou ld be utilized; the US tradit ional NEC Article 500-501, Class, Division, Group; or the NEC Article 505, Class, Zone, Group.

Refer to Sections 3-1 and 3-3 for use with the US traditional Class, Division, criteria to de t e rmine the degree of hazard: Is the area Division 1 or Division 2?

Refer to Sections 3-2 and 3-3 for us ing NEC Article 505 Class, Zone, criteria to de te rmine the degree of hazard: Is the area Zone 0, or Zone 1, or Zone 2?"

(8) Insert an "(a)" before the pa ragraph in Section 3-1.1 and delete the "3-1.2 in the nex t section mad replace with "(b)". Change existing "3-2" into "3-1.2" and replace "3-2.1, 3-2.2, 3-2.3, 3-2.4, and 3-2.5" with "(a), (b), (c), (d), and (e)." Add a new Section 3-2, 3-2.1, 3-2.2, and 3-2.3 with Z one 0, 1, and 2 criteria. The entire revision shou ld read as follows:

3-1 Class, Division Classified Locations. 3-1.1 Division 1 Classified Areas. (a) A condi t ion for Division 1-is whe the r the a rea is likely to have

an ignitible mix ture p resen t u n d e r no rma l conditions. For instance, the presence of a combust ib le material in the immedia te vicinity of an open dip tank is no rma l and requires a Division 1 classification.

(b) Normal does no t necessarily m e a n the s i tuat ion tha t prevails when everything is working properly. For instance, there may be cases in which f r equen t m a i n t e n a n c e and repair are necessary. These are viewed as normal and, if quantif ies of a f lammable liquid, or a combust ib le material are released as a resul t of the ma in tenance , the area is Division 1. However, if repairs are no t usually requ i red between tu rnarounds , the n e e d for repair work is cons idered abnormal . In any event, the classification of the area, as related to e q u i p m e n t ma in tenance , is in f luenced by the ma in t enance p rocedures a n d f requency of ma in tenance .

3-1.2 Division 2 Classified Areas. (a) The cri terion for a Division 2 area is whe the r the area is likely

to have ignitible mixtures p resen t only u n d e r abnormal conditions. The term "abnormal" is used here in a l imited sense and does no t inc lude a major catastrophe.

(b) As an example , consider a vessel conta in ing liquid hydrocarbons ( the source) tha t releases combust ib le material only u n d e r abnorma l condit ions. In dais case, there is no Division 1 area because the vessel is normal ly tight. To release vapor, the vessel would have to leak, and tha t would n o t be normal . Thus , the vessel is s u r r o u n d e d by a Division 2 area.

(c) Chemical process e q u i p m e n t does no t fail often. Fur the rmore , the electrical installation r e q u i r e m e n t of NFPA 70 for Division 2 areas is such tha t an ignition-capable spark or ho t surface will occur only in the event of abnorma l opera t ion or failure of electrical equ ipment . Otherwise, sparks a n d ho t surfaces are no t p resen t or are conta ined in enclosures. O n a realistic basis, the possibility of process e q u i p m e n t a n d electrical e q u i p m e n t failing s imul taneous ly is remote .

(d) The Division 2 classification is also applicable to condi t ions no t involving e q u i p m e n t failure. For example , consider an area classified as Division J because of no rma l p resence of an ignitible mixture . Obviously, one side of the Division 1 boundary canno t be normal ly hazardous a n d the opposi te side never hazardous. W h e n the re is no wall, a s u r r o u n d i n g t ransi t ion Division 2 area separates a Division 1 area f rom a unclassif ied area_

(e) In cases in which an unp ie rced barrier, s uch as a b lank wall, completely prevents the spread of the combust ible material , a rea classtfication does n o t ex tend beyond the barrier.

3-2 Class I, Zone Classified Locations. 3-2.1 Zone 0 Classified Areas. (a) A condi t ion for Zone 0 is whe the r the area has an ignitible

mixture p resen t cont inuously or for long per iods of time. (b) This classification includes locations inside ven ted tanks or

vessels con ta in ing volatile f l ammable liquids; inside inadequate ly ven ted spraying or coat ing enclosures where volatile f l ammable

solvents are used; between the inne r and outer roof sections of a floating roof t ank con ta in ing volatile f l ammable liquids; inside open vessels, tanks, and pits con ta in ing volatile f l ammable liquids; the inter ior of an exhaus t duc t tha t is used to vent ignitible concent ra t ions of gases or vapors; and inside inadequate ly venti lated enclosures con ta in ing normal ly ven t ing ins t ruments utilizing or analyzing f lammable fluids a n d ven t ing to the inside of the enclosures.

( c ) It is no t good practice to install electrical e q u i p m e n t in Zone 0 locations except when the e q u i p m e n t is essential to the process or when o ther locations are n o t feasible.

3-2.2 Zone 1 Classified Areas. (a) The criteria for a Zone 1 area are whether the area (1) is likely to have ignitible mix tures p resen t u n d e r normal

condit ions; or (2) is likely to have ignitible mixtures exist f requent ly because of

repair or m a i n t e n a n c e opera t ions or because of leakage ; or (3) has condi t ions in which e q u i p m e n t is opera ted or processes

are carried on, tha t e q u i p m e n t breakdown or faulty operat ions could result in the release of ignitible concent ra t ions of f lammable gases or vapors a n d also cause s imul taneous failure of electrical e q u i p m e n t in a m o d e to cause the electrical e q u i p m e n t to become a source of ignition; or

(4) is located adjacent to a Class I, Zone 0 location f rom which ! ignitible concent ra t ions of vapors could be communica t ed , unless c o m m u n i c a t i o n is prevented by adequa te positive-pressure

ven t i l a t i on f rom a source of clean air a n d effective safeguards against venti lat ion failure are provided.

(b) This classification usually includes locations where volatile f lammable liquids or l iquefied f l ammable gases are t ransferred f rom one conta iner to another , in areas in the vicinity of spraying and pa in t ing opera t ions where f lammable solvents are used; adequately, venti lated d!r~°ng rooms or compa runen t s for the evaporauon of f l ammable solvents; adequate ly vent i la ted locations conta in ing fat and oil extract ion e q u i p m e n t us ing volatile f l ammable solvents; por t ions of c leaning a n d dyeing plants where volatile f lammable liquids are used; adequate ly venti lated gas genera tor rooms and o ther por t ions of gas manu fac tu r i n g plants where f lammable gas may escape; inade, q~uately ventilated, p u m p rooms for f l ammable gas or for volatile f l ammable liquids; the interiors of refrigerators and freezers in which volatile f lammable materials are s tored in the open, lightly s toppered, or easily r up tu r ed containers; and o ther locat ions where ignitible concent ra t ions of f l ammable vapors or gases are likely to occur in the course of no rma l operat ion, bu t no t classified Zone 0.

3-2.3 Zone 2 Classif iedAreas. (a) The criterion for a Zone 2 area is whe ther (1) ignitible mix tures are no t likely to occur in no rma l operat ion

and if they do occur will exist only for a shor t period; or (2) ignitible mixtures are handled , processed, or used, bu t in

which the liquids, gases, or vapors normal ly are conf ined within closed containers or closed systems f rom which they can escape only as a result of accidental rup tu re or breakdown of the containers or system, or as the resul t of the abnormal operat ion of the e q u i p m e n t with which the liquids or gases are handled, )rocessed, or used; or

(3) ignitible mixtures normally are p revented by positive nechanica l ventilation, bu t which may become hazardous as the

resul t of failure or abnorma l opera t ion of the ventilation equ ipmen t ; or

(4) the a rea is ad jacent to a Class I, Zone 1 location, f r o m which ignitible concent ra t ions of f l ammable gases or vapors could be communica t ed , unless such c o m m u n i c a t i o n is p revented by adequate positive-pressure venti lat ion f rom a source o f clean air, and effective safeguards against venti lat ion failure are provided.

(b) The Zone 2 classification usually includes locations where volatile f l ammable liquids or f l ammable gases or vapors are used, bu t which would become hazardous only in case of an accident or of some unusua l opera t ing condit ion."

(9) In Section 3-4.1, add "; or Zone 0, Zone 1, or Zone 2" to read as follows:

3-4.1 The extent of a Division 1 or Division 2; or Zone 0, Zone 1, or Zone 2 area requires careful considera t ion of the following factors:"

(10) In Sections 3-4.2(c), 3-4.3, 3-4.4 and 34.5 add the Zone 0 in format ion as follows: ....... combust ib le material so that the ex ten t o f the classified area is greatly reduced. Thus , d imens iona l limits r e c o m m e n d e d for ei ther Class I, Division 1 or Division 2; or Class I, Zone 0, Zone 1, or Zone 2 classified areas mus t be based on exper ience ra ther t h an relying solely on the theoretical diffusion of vapors.

3-4.3 The size of a bui ld ing and its des ign may inf luence considerably the classification of the enclosed volume. In the case

2 1 5

N F P A 4 9 7 A - - A 9 7 R O C

of a small inadequately venti lated room, it may be appropr ia te to classify the entire r o o m as Class I, Division 1 or Class I, Zone 1.

3-4.4 W h e n classifying buildings, careful evaluation of pr ior exper ience with the same or similar installations should be made. It is no t e n o u g h to merely identify a potential source of the combust ib le material within the bui ld ing and p roceed immedia te ly to def in ing the ex ten t of ei ther the Class I, Division 1 or Division 2; or Class I, Zone 1 or Zone 2 classified areas. Where exper ience indicates that a part icular des ign concep t is sound, a more hazardous classification for similar installations may n o t be justified. Fur the rmore , it is conceivable tha t an area migh t be reclassified f rom ei ther Class I, Division 1 to Division 2, or f rom Class I, Division 2 to unclassif ied or f rom Class I, Zone 1 to Zone 2, or f rom Class I, Zone 2 to unclassified based on experience.

3-4.5 Correctly evaluated, an installation will be f o u n d to be a multiplicity of Class I, Division 1 areas of very l imited extent. The same will be t rue for Class I, Zone 1 areas. Probably....

(10) In Section 3-5.1, correct the second word in the last sen tence f rom "bases" to "basis" and add Zone 0 informat ion into Section 3-5.3 to read as follows:

3-5.3 An opera t ing un i t may have many in te rconnec ted sources of combustible. . . to establish the boundar ies of e i ther Division 1 and Division 2, or Zone 0, Zone 1, and Zone 2 areas."

(11) In Section 3-8, add a new last sen tence to the end of the first paragraph that reads as follows:

3-8 Classification Diagrams. Most d iagrams in this sect ion. . .diagrams include f igures 3-8.1 t h rough 3-8.34. Class I, Zone Classification d iagrams include f igures 3-9.1 t h rough 3-9.34.

(12) In Table 3-8, in the first column, add (Class I, Zone) and (3-9.1) t h rough (3-9.~4) adjacent to 3-8.1 t h r o u g h 3-8.34.

(13) Insert tides and figures for Zone appl icat ions immedia te ly after 3-8.34.

Figure Source ~ a c l u s

Grade ---~ 18-~m. ~ ~ 18"~ .

Below-grade location such as a sump or ~ench

Material: Flammable liquid Small/low Moderate large/nigh

Process equipment X X

SiZe Pressure X X Flow rate X X

Note: Adapted from NFPA 497A, Figure 3-4,1. Leakage source located outdoors, at grade.

Zone 1 t

Zone 2

Figure 3-9.1 is based upon Figure 3-8.1 and shows a source o f leakage located outdoors , at grade. The material be ing handled is a f l ammab le liquid.

Gr~-- 1 //)X\Xx/'~\\

Source

ts .

3-ft radus

Be~ow grade Ioca~on such as a surnp or ~'ench - - . I

Materiah Flammable I~luid Smalblow Mediate large/nigh

Proce~ equipment X X

size Pressure X X

Flow rate X X

Note: Adapted from NFPA 497A, Figu¢e 3..4.2. Leakage soucce located outdoors, above grade.

Zone 1

Zone 2

Figure 3-9.2 is based upon Figure 3-8.2 and shows a source of leakage located outdoors, above grade. The material being handled is a flammable liquid.

Below-grade location such as a sump or b*ench

Material: Flammable liquid Small/low Moderate Large/high B~CCCR

Process Zone t equipment X X moe~6=

size

Pressure X X Zone 2 Row rate X X Y ~

Note: Adapted (Tom NFPA 497A, Figure 3-4.3. Leakage source located indoors, at floor level. Adequate venlfla~on is provided.

Figure 3-9.3 is based upon Figure 3-8.3 and shows a source o f leakage located indoors , at f loor level. Adequa te ventilation is provided. The material be ing handled is a f l ammable liquid.

"/)X\'~',O~\\

Source

I, 2~-~r,diu, "1 y Below-grade location such as a sump or b'ench

Materiah Flammable IK1uid Small4ow Moderate Large/high

Process Zone f equipment X X iooooo~

size

Pressure X X Zone 2 Flow rate X X

Note: Adapted fi'crn NFPA 497A, Figure 3-4.4. Leakage source located indoors, above flo<~/evel. Adequate ventJJafion is provided.

Figure 3-9.4 is based upon Figure 3-8,4 and shows a source o f leakage located indoors , above f loor level. Adequa te venti lat ion is provided. The material be ing handled is a f l ammable liquid.

Soume

-1 ,i I, " r " l , I Be~ow-gr ado Iocalion such ~ a suf~p or I re,oh J

Mat~kld: Flamma~e liquid SmalVIow Medial# L a r ~

Prooe~ Zone t , , ~ F , ~ x x l aC~oca

size

Pr~sur# X X Zone 2 blow rate X X

Noq#: Adap(ed from NFPA 497A, Figure 3-4.5. Leakage source IooatKI ~cloors, at floor IMI, adjaoent to o p ~ m exl~ior wall. AdqK]uate wnlilation is provided.

Figure 3-9.5 is based upon Figure 3-8.5 and shows a source o f leakage located indoors, at floor level, adjacent to an opening in an exterior wall. Adequate ventilation is provided. The material being handled is a flammable liquid.

216

N F P A 4 9 7 A ~ A 9 7 R O C

Outside wal~ = " ~ i

Below-grade Iooalion such as a sumlp Of Irench ~i~h~t in Zone 1 or Z~ne ;! portion o[ building

Note: If building is small cornoared Io s~ze of equipmenl alxI leakage can lill ~he b~idlng, the er~ir * b~ildi~ in~efiot is d ~*sra~i*d Zany, t.

Malerial: Rammable liquid Small/low Modorale Large/high

Zone t B Prooess *quipmt~t X X

size Pressure X X Zorm 2

Y/Z/Z~ Row rale X X

Note: Adapted t~om NFPA 497A, Fbgu re 3-4.6 Leakage source IocateO indoors, at Iloor level, ac~a~erR to Opening m exterior wall. Adequade ve~ilation is provided.

Figure 3-9.6 is based upon Figure 3-8.6 and shows a source of leakage located indoors, at floor, level, adjacent to an opening in an exterior wall. Ventilation is not adequate. The material being handled is a f lammable liquid.

15-ft radius

/,

Grade

t~ t~ id : ~an,~,'n a~=. liquid, liquetied f i ~a , l~e gas, compressed flarn ma~:le gas, and cryogenic ~ic~ld

Srna~l/Iow Mediate Lalg~high Process Zone i

equipment X X size

Pressure X X Zone :P

ROW rate X X

Note: Ad ap~cl item NFPA 497A, Figure 3-4.7. Leakage source ~ocated outdoors, at grade.

m FTA

Figure 3-9.7 is based upon Figure 3-8.7 and shows a source of leakage located outdoors, at grade. The material being handled may be a f lammable Liquid or a l iquefied or compressed f lammable gas, or a f lammable cryogenic liquid.

Grade - ~

//2X\WT'~\\

Below-grade Ioce~on such as a sump or bench

Sour ce ~ s

Y Material: Rammab~e liquid, liquefied 1amenable gas, compressed

flammable gas, and cryogenic liquid

Small/low Moderate Larg~/hJgh

Process Zone equipment X X

size

Pressure X X Zone 2 Flow rate X X

Nots: Adapted from NFPA 497A, Rgure 3-4.8. Leakage source located outdoors, above grads.

J

Figure 3-9.8 is based upon Figure 3-8.8 and shows a source of leakage located outdoors, above grade. The material being handled may be a f lammable liquid or l iquefied or compressed f lammable gas, or a f lammable cryogenic liquid.

Or'7 "/)"\"~'/;"\\ ~ I. so ~ ~ i T

T I: ;,oo. .I L - - Below-grade Iocalion such as a sum~ or ~'onch

I ~ Zone I

] Zone 2

~ Addil)onal Zccto 2 Iocatx:~n. Use ox~r a ~oca~lion where I~ge relo ass of volalile products may occur

MateriaJ: Rarnrnablo lquid

Smak/Iow Moderato Largo/high process

equipment X SIZe

Pressure X X

ROW rate X

Nole: Adapted from NFPA 497A, Figure 3-4.9. Leakage source located outdoors, at grade.

Figure 3-9.9 is based upon Figure 3-8.9 and shows a source o f leakage located outdoors, at grade. The material be ing handled is a f lammable liquid.

217

N F P A 4 9 7 A - - A 9 7 R O C

ft

S o u r c e ¢ 1 1 1 1 1 ~

I ~ Zone I Balow-~ade location sue

Zo~e 2

i= - ' lOOli '1 ~l

fade location s~¢~ as a sump or linch

[ ] Addilional Zone 2 Iocallon. Use = i s procau~io~ where large release of volatile products may occur.

Material: Flammable liquid

Srnal,tow Moderate Largo/ldgh Proc~

equipm~-lt X size

Pressure X X Flow rate X

Note: Adapted from NFPA 497A, Figure 3-4.10. Leakage source located outdoors, above grade.

Figure 3-9.10 is based upon Figure 3-8.10 and shows a source o f leakage located outdoors, above grade. The material being handled is a f lammable liquid.

10-It radius . ~ . ~ / ~ P i e r c e d wall

Grade

1 Note 1 : "Apply" horizontal dJstsnces of 50 It from the l i c e of vapor or 10 ft beyond the wimets¢ of the t:~iding, whichever 18 greater, except that beyond unplecced vapoftight walla the ai'ea is undaseilted.

Z~e l

] Z~e2

[ ] A~i~ona lZ~e21o~.~eext 'a~ecau~wh~eluge r ~ ofvala~epro~ctsm~occur.

tdats¢lal: Rammal01e li~id

Smallilow Modemil Largegaigh Process

eqUilp~*m x x size

Pm~,ure X Flow rate X X

Note: Adapted from NFPA 497A, Figure 3-4.11. Leakage source located indoors, adjacent to opening in extedor wall. Ad4~iual ve.ila~on IS not provided.

Grade .7 =

///~\'~(/X\\

I- ~///////~///////////~

Material: Rammable liquid

Small/low Moderate Largo/high


size Pressure X

Flow rate X X

Note: Adapted from NFPA 497A, Figure 3-4.12. Leakage source tecated indoors, a~acent to ope~n o in exterior wall. Adequate vantilalon is not provided.

Zone 1 /

Zone 2

Figure 3-9.12 is based upon Figure 3-8.12 and shows a source o f leakage located indoors, adjacent to an opening in an exterior wall. Adequate ventilation i s p r o v i d e d . The material being handled is a f lammable liquid.

Process column process column

Pipoways, p~p~ng w~hout ~ j j / aro~ldvsiw I I valves, meters, or gos.0,a .s .11

1"'11 t ' t l ade n b.,'- I......,...l.... I : -0-0,, ,..

Below-grade 10ce~on such as a sump or trench

Material: Flammable liquid

Small/low Moderate Lalge/high


size Pressure X X

Flow rate X X

Note: Adapted from NFPA 497A, Rgure 3-4.13. Mul~ple leakage sources, bolh at and above grade, in outdoor process area.

zo~ m

Zone 2 ~ ' ~

Figure 3-9.13 is based upon Figure 3-8.13 and shows multiple sources o f leakage, located both at grade and above grade, in an outdoor process area. The material be ing handled is f lammable liquid.

Figure 3-9.11 is based upon Figure 3-8.11 and shows a source o f leakage located indoors, adjacent to an opening in an exter ior wail. Ventilation is no t adequate. The material be ing handled is f lammable liquid.

218

NFPA 4 9 7 A - A97 ROC

~'"7

Process column Prcce~s column

25R ;~ 251t

Source; \ i

) or l e n ~ h ~ B~low~ra~t ~caecfi s u ~ as it sum I

Zone 1

' ~ Zone 2

A ~ i ~ n ~ Z ~ e 2 a r ~ wh~e ~ e a ~ may ~ I~ge

M a ~ ¢ ~ : R ~ m a ~ I q ~ d

S m = ~ Moderate L i ~ h

~ocess KI~F n*nt x x

P r ~ e X X

Flow tare X X

Note: Adapted tom NFPA 497A, Figure 3-4.14, Multiple leakage source, bo(h at and ebove grade, in c~J~loor proems area.

Figure 3-9.14 is based upon Figure 3-8.14 and shows multiple sources of leakage, h)cated both at grade and above grade, in an outdoor process area. The material being handled is a flammable liquid.

2 ' : . . . . . ° " . . . . . " ° ,

341 nl~l~ll am~r~ pumps (~Clil)

BeIow~l~t~ ¢tc8~0~ ~ c f l 8~ ~ Ft~np or Ifef~h.

Mal~Clit: FlammaUo Iw~d

S m ~ ~8fSM Lif~elRll~ll P~OC~

equp~e~l X X s~

~eeet~e X X

Rnw rate X X

Note; Adapted 1tom NFPA 49 TA. Rgum 3-4> 15 Mul~e le4t kag~ nl VU'~, ~ st arid above gt'a~e, ~ outdo0f process anm

Z~r~ 1

F 5 ~ I rad~t tom ~n~ (ty~csl)

~ ~1 radlcm mOUnd ~ m l and i

Gfellng Iloof wllh u n n g b vessel

~;~clt ~4~l~t't column

10in

Z o o 2 [ ]

Figure 3-9.15 is based upon Figure 3-8.15 and shows multiple sources of leakage, located both at and above grade, in an outdoor process area. the material being handled is a flammable liquid.

3-It raOiJ! a r o u ~ at Iocat w shown

SOlid IIO~ Inll - - < i ft ope~ng for veuel ~L

/ / T i , ,o,, , i , ,

t#~enli: R~m=lte I~u(l Sinai/low Modentte L~je/tlgh

Zone I Proce~ equpmem X X

s~e I~essc~e X X

Z~ne 2 Flow mit X X

NoM Adaplad 1 ~ NFPA 49ZA, Fl~Jm 3-4 16 M~p~e le~ t~ ~ . bolh lit l l ~ ~v i i floor le~, I~lod irl~a-s Am(itltle ~e~llail is p ro i ld

~ - ~ ~-~n~n~aJs born "~nts

~ 1 ~ 54l t"~ilu s Ir 01TI ~nla ( iyl~ c~ )

541 radaJs around le~< sources sum "--as martloFee, v~vm, e¢

- ~ s t ~ 9 floor or sold deck wi~ operlng for vessel

e-----Ty pqca uuppcn co~mn Zone 2

~ " - - 5 ~ md~s ¢mund pJmp and rank

[ ] [ ]

Figure 3-9.16 is based upon Figure 3-8.16 and shows multiple sources of leakage, located both at and above floor level, in an adequately ventilated building. The material being handled is a flammable liquid.

• ~ t r°~l ~ ~ Zo.°nR°r ~d uns

~ Vent

I \ / ' - - -

Hot air ~

. Inert gas bl;mket in elevator and bin

Mabdol: Soids w i t w i~ I t ' , m ~ liquid

I Zcft. 1 [ ~ Zone2

Note: AdaptKI from NFPA 497A Figure 3-4.17.Totsly enclosed product dryer located n aoequatdy vonti lald btdkhng.

Figure 3-9.17 is based upon Figure 3-8.17 and shows a product dryer located in an adequately ventilated buUdin~. The product dryer system is totally enclosed. The material being handled is a solid wet with a flammable fiquid.

219

N F P A 4 9 7 A - - A 9 7 R O C

= - 1 I ' - . . . . . . . . . . . . . . . . . . . . . . . .o~_-~.p=i,o~

• ~/,,4

MateriaJ: Solids wet with flammable liquid

I ~ Zon. 1 ~ Zon. 2

Note: Adapted fTom NFPA 497A W~gure 3-4.18. Plate end ~Tame filter press provided wi~ ad~Oate V~t~ a~on.

Figure 3-9.18 is based upon Figure 3-8.18 and shows a plate and frame filter press. Adequate ventilation is provided. The material being handled is a solid wet with a flammable liquid.

Tan~ w~lin dike ~ ~ Tank in open (undiked) area

L ~ , - - - Zone 1

5-ft radius around vent

l 0-ft radius t om vent

L . - Below-grade Iocaton such as a surnp or a'ench

Material: Fl~nm abta tiqutd

SmaMow Moderate Large/nigh Zone 0 Process

equipment X X size Zone 1

Pressure X B88888i Flow rate X X

Zone 2 Note: Adapted from NFPA 497A, Figure 3*4. 99. Storage tanks, outdoors at grade.

Figure 3-9.19 is based upon Figure 3-8.19 and shows a product storage tank located outdoors, at grade. The material being stored is a flammable liquid.

j f ~ ~ / . ~ ' / ~ - - Zft r°nea 2 . . . . . . d valves

,2 -T* //JN~-'W/~\\

M a~,rial: R a m i e liquid

~ Z~e , ~ Zone2

Note: Adapted from NFPA 497A, Figure 3-4.20. Tank car/tank ~'uck loading and unloading via dosed system. Transfer through dome only.

elgure 3-9.20 is based upon Figure 3*8.20 and shows tank car loading and unloading via a closed transfer system. Material is transfern only through the dome. The material being transferred is a flammable liquid.

ugu _

k =. Z N \ L .

3-ft radius

Material: Rarnmable liquid

~ Zone1 ~ Zone2

Note:Adapte¢l from NFPA 497A, Figure 3-4.21(a).Tank car/ta~< ~ud~loading and unloading via dosed system. Bottom product transfer onty

Figure 3-9.21(a) is based upon ~gure 3-8.21(a) and show tank car and tank truck loading and unloading via a closed transfer system. Material is transferredthrough the bottom fittings. The mater~al being transferred is a flammable liquid°

7///~/~. {=%-~ r~

Mal et~a~: Ramma~ ~quiO

I ' - " W z-e' Nole:AOaplod Item NFPA 4g','A, Figure 3-4.2 f[b).Ta~ I~cK loading

and un k~f~g ~ ck~KI sy el*me,

Figure 3-9.21(5) is based upon Figure 3-8.21(b) and show tank car and tank truck loading and unloading via a closed transfer system. Material is transferredthrough the bottom fittings. The material being transferred is a flammable liquid.

"///'~

3-t radius around ~ Zone 2

1 ~ Below-grade Iocalion such as rump or Ir ench

Material: RWT~'n =hie liqt~:l

Note: Adapted t om NFPA 497A, I~ure 3-4 ,?.2. Tank cartta~ II-uck loading end unloading via open system.Top or bottom product t r~$~r ,

Figure 3-9.22 is based upon Figure 3-8.22 and shows tank car (or tank truck) loading and unloading via an open transfer system. Material is transferred only throug ht hedome. The material b elng transferred may be aliquefled or compressed flammable liquid.

220

N F P A 4 9 7 A - - A 9 7 R O C

5-ft radius m'ound v ~ . . . . . . . H H . . . . . . ~ j ~ ~ 15-ft radius

~ ~ ~ ~ > r ~.-

MateriaJ: R ammable Wquid, flammable compressed gas, flammable c~yogenic liquid

I ~ Zone 1 ~ Zone2

Note: Adapted Ir0rn NFPA 497A, Rgure 3-4 23.Tarl~ car/tank ffud~ loading and unloao~g via dosed system.Transfer through dome only.

i Figure 3-9.23 is based upon Figure 3-8.23 and shows tank car (or tank truck) loading and unloading via a closed transfer system. Material is transferred only through the dome. The material being transferred may be a l iquefied or compressed flammable gas or a f lammable cryogenic liquid.

. .~///..._ ~ FIN pipe

~0. ,1 Below-grade Iocalon such as ,sun~ or Iret~q ~ t

M al edsi: Fla,nvnaUt klUl~

I ~ * : A d ~ l ~ , n ~ PA 4#7~, F ~ - 3-4.2 4. O ~ f I l~ sl~l~, o ~ r s or InOoot~, with adequata v*mgal~,

Figure 3-9.24 is based upon Figure 3-8.24 and shows a drum f'dling station located either outdoors or indoors in an adequately ventilated building. The material being handled is a f lammable liquid.

1 8 i n . . . - - L

18in.

! Below-grade location SuCh as svrnp o¢ tret~h

'

Note: This diagram does ~Ot apply Io open pils or op~ vessels, sUCh as dip tanks Of open mixing lanks, thai norma#y ¢ot1~ ItarnK~bl e liquids

Maledal: R ~wm able liq~¢l

B Zor~z ~ Zone2

Note: Adapted ~ccn NFPA 497A, Figure 3-4,25, Emergency impounding basin or oiVwa tet separator (top) and an eme~j~ermy or cka'ma~e ditch o~/wal sr separator (bottom)

tgure 3-9.25 is based upon Figure 3-8.25 and shown an emergency mpoundign basin or oi l /water separator and an emergency

drainage ditch or oi l /water separator. The material being handled is a flammable liquid.

Zone 2 25-R radius

Pdm where ~nection$ I/2%,%,~(,~\~ are regularly made

Liquid ~d.~l~ storage ¢onlalr~r

M= ~=: Liquid hy~og~

mz ., z=.2

Not*: Ad~flsd from NFF~ 497A, U-~UC* 5-4.26. Liquid I'ej(~ ~ slor~e located ot~doots or in an ~qual~y ~ilaled building.

F'~rure 3-9.26 is based upon Figure 3-8.26 and shows a fiquid hydrogen storage located outdoors or indoors in an adequately ventilated building. This diagram appfies to liquid hydrogen only.

Zone 2

Zone 2 16-ii radius

I~_~"/////////A Gracie I r / ~ o u r ( : ~ at 15-. maximl~n

ad~uale ~n hiatioq

Mal~= Gaseous nyc~mge~

Nole Adapl~l frotl~ NFPA 491A. Fig~e 3-42T Gaseous hl/drcgen slofBge I(xzated outdoes ~ ~do[Xs in an adequatsiy ~anWalad bui~ng

F~ure 3-9.27 is based upon Figure 3-8.27 and shows a gaseous hydrogen storage located outdoors or indoors in am adequately ventilated building This diagram applies to gaseous hydrogen only.

221

N F P A 4 9 7 A ~ A97 R O C

15A

Bottom of 1 end~ecl ar*a

..... ..... ~ 15-1 ~'adius

Mat#rial: I ighter*tl~n-a]r gas

~ l Zone 1 [ ~ Zone2

NrA*~: Adapied from NFPA497A, F'llTJre 3-4.28. A~qualeiy ve~llJaled oompr.ssc¢ sheller.

$ouro*

Figure 3-9.28 is based upon Figure 3-8.28 and shows an adecjuately ventilated compressor shelter. The material being handled ts a lighter-than-air gas.

Sou Grade

///N\'~',,~\\

Maleriat: Lift*r-than- air 9as

[ ] ' - Nz-' Note: Adapted kom NFPA 497A, Flgu ro 34.29. Inadequately veNaated compressor dlelter.

Figure 3-9.29 is based upon Figure 3-8.29 and shows an inadequately ventilated compressor shelter. The material being handled is a fighter-than-alr gas.

° " - I ///~\X"/A,\\

Source

[] 1

15-ft radius----~ ~ 15-h radius from relef waive "z~////.~ / e l l around

H ' ~ ~ ~ V- X ~ Container ~ ~ . ~ F Grade

t es~a

t . _ 8,1ow~rade leco~ . . . . h . . . . ~o or ~enoh Dike height less than distance from container to dike (H less than X)

15dr radius ~ 154t radius from raltef waive ~k~//. / ' - ' - a l l around

. r a , o ,

/ / /%\W/~,\ \

Dike height greater than distance from container to dike (H greeter than X)

,~ "m :~%,wa--'~//..... T :,, e~"~'2~" r

/ I Matelial: Liquified natural gas or other cryogenic flammable iquids

U Zone1 [ ~ Zone2

Note: Adapted from NFPA 497A, Figure 3-4.30. Storage tanks for cryogenic liquids.

Figure 3-9.30 is based upon Figure 3-8.30 and shows tanks for the storage of cryogenic and other cold liquefied flammable gases.

15-[t rndus

B

Material: LJquifi~:l natural gas or o~er cryogenic flamrna~e liquid

m ~ Zone t ~ Zon. 2

Note: Adapted fiom NFPA 497A. Figuce 3-4.3t. Leakage source from equipment handling liquified natural gas. Source is located outdoors at o¢ above grade.

Figure 3-9.31 is based upon Figure 3-8.$1 and shows a source of leakage from equipment handling fiquefied natural gas or other cold liquefied flammable gas, and located outdoors, at or above grade.

222

N F P A 4 9 7 A ~ A 9 7 R O C

/ ~ Zone 2 15-

Indoors with adequate ventilation

Material: Liquif~ed naturat gas or other cryogenic flammable liquids

~ Zone1 [ ~ " ~ Zone 2

Note: Adapted from NFPA 497A, Figure 3-4.32. Leakage source from equipment handling liquffie¢l natur~ gas in an adequately ventilated building.

Figure 3-9.32 is based upon Figure 3-8.32 and shows a source o f leak .e from e uipment handl in liquefied, natural, gas or o ther cel iaC'queried ~ a m m a b l e gas an~ located m d o o r s in an adequately venti lated building.

Zone 2 --,--.-- t ~ Zone 1 15-ft r a d i u s ~ 5-ft radius

Sourco ~ ~

Outdoors at or above grade

F - - Z o n e 2 15-(1 radius

Zone 1 - - 5-ft radius

Grade Source - - - Zone 2 15-ft radius from opening

/,f/X\'cf/X\\ Indoors with adequate ventilation

Material: Liquified natural gas or other c'-qogenic flammable liquids

~ Zone1 [ ~ Zone2

Note: Adapted from NFPA 4.9. A, Figure 3-4.33. Leakage source from routinely operating bleeds, equipment handling liouified natur =1 gas in an adequately ventilated building.

Figure 3-9.33 is based upon Figure 3-8.33 and shows the classified zones around liquefied natural gas operating bleeds, drips, vents, and drains both outdoors, at or above grade, and indoors in an adequately ventilated building. This diagram also applies to other cold liquefied flammable gases.

50 h 50 {t

~t'J'J'~t~t~#C1~-""~t -"-- ar(~d allst n gedanpIl'~st t°Peon rj,

E Approacn ~ v)~ rf/~-~j

- - Water level Notes I lho "soulce of vapor" shall be the opiating ~v~ope and stored pouuon el

oulb~d U~tge ccnnect~n ot ¢=a loading arm (or t~ose) 2 The brain area ad acsnt to tank~ and barge cargo tanks Js to be Zc~e 2

to ihe lc~lowing extent (a) 25 It hobzontaJly in all direchons on (t~ i~er ede Imm I~al porqi0o ot the hul contaning cargo tanks (b) From the wala~ level to 25 11 abov~ Ins ~go ~nks at Ihe~r highesl pc~ltiOn

3 Addition~ Iocakons may nave ~o be d as~l~gd as r equimd by Itle or 6sence o( Other sotlca s el flammat~e ~iqu~ls or ~4 COasl Guild or oiler regulations

Malaria Flammfl~e liquids

B Z . . . . ~ Z . . . .

No~ A~i~ted (~or~ NFP~ 49 g~.. Fi~ug~ 3-434 M~ri~e ~erm~al h~g'dt)n~ t~ml~b~ h~ds

F'gure 3-9.34 is based upon Figure 3-8.34 and shows the classified zones at a marine terminal handling flammable liquids and includes the area around the storedposition of loading arms and hoses.

SUBSTANTIATION: The Zone in format ion was incorpora ted into the rewritten text of Proposal 497A-15 to upda te this r e c o m m e n d e d practice to be consis tent with the 1996 National Electrical Code Article 505 informat ion.

"Division" was added after "Class I" to differentiate between Class I, Divisions a n d Class I, Zone applications. COMMITTEE ACTION: Accept . NUMBER OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 23 NEGATIVE: 1

EXPLANATION OF NEGATIVE: ST. ONGE: My vote is affirmative for all of the Zone text of

C o m m e n t 497A-1 except for Section 3-8 "Classification Diagrams." My negative vote is, therefore, based on my d i sagreement with the Commi t t ee Action as appl ied to Section 3-8.

My reasons: 1o Thir ty four addit ional diagrams, Figures 3-9.1 t h roug h 3-9.34

are inserted. Note these f igures are no t "adaptat ions" of Figures 3-4.1 t h rough 3-4.34 of 497A-1992. They show exactly the same Mater ia l /Proper ty /Appl ica t ion . They are the same as Figures 3-8.1 t h rough 3-8.34 of 49qA-A97 ROP. The only difference is the label ing of the classification symbol to show Zone classification. This is no t sufficient reason to add 34 addit ional figures.

T h e same result can be obta ined us ing Figures 3-8.1 t h ro u g h 3- 8.34 of the A97 ROP by add ing "Zone 1" to the left of the Division 1 symbol and "Zone 2" to the left of the Division 2 symbol of each figure.

This sameness or equivalency is acknowledge by the. proposed. act ion on Table 3-8. Each Mate r i a l /P roper ty /Apphca t lon would be re fe renced to two figures, one in the Figure 3-8 series, the second in the Figure 3-9 series. The Figure 3-8 series with correctly labeled classification symbols is all tha t is needed .

2. This s t andard shou ld be he lp ing users u n d e r s t a n d that, except for the very few release condi t ions for which Zone 0 applies, the two classification systems with correct appl icat ion of e q u i p m e n t and wiring provide equivalent levels of protection. I don ' t believe addin 34 fi res hel s tha t unde r s t and in . CO EG N g

MESINA: "I agree with Mr. St. Onge ' s negative vote on C o m m e n t 497A-1, in principle. However, Mr. Onge ' s recipe for chang ing Figures 3-8.34 is incomple te ... s ince there are locations on some of the f igures where "Division 1" or "Division 2" appear in addi t ion to where the Division symbols appear . "Zone 1" or "Zone 2" should be a d d e d to these locations, where applicable - as well as to the symbol locations."

2 2 3

N F P A 4 9 7 A m A 9 7 R O C

(Log #11) 497A- 2 - (1-3): Accept in Principle SUBMITTER: David Wechsler , U n i o n Carbide Corp. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: Make the Groups "def ined terms" by bold type in accordance with the NFPA Style Manual and change these defini t ions of Group A, B, C, a n d D by replacing "combust ible materials" with the def ini t ion for combust ib le materials and el iminate the te rm "gases or vapors of equivalent hazard." This will result in the following:

Group A: Acetylene Group B: F lammable gas, f l ammable l iquid-produced vapor, or

combust ib le l iquid p r o d u c e d vapor mixed with air tha t may burn or explode, having ei ther a m a x i m u m exper imenta l safe gap (MESG) value less t han or equal to 0.45 m m or a m i n i m u m ignition cur ren t (MIC) ra t io less t han 0.40.

Group C: F lammable gas, f l ammable l iquid-produced vapor, or combust ib le l iquid p r o d u c e d vapor mixed with air tha t may bu rn or explode, having ei ther a m a x i m u m exper imenta l safe gap (MESG) value between 0.45 m m and 0.75 m m or a m i n i m u m ignition cur ren t (MIC) ratio between 0.40 and 0.80.

Group D: F lammable gas, f l ammable l iquid-produced vapor° or combust ib le l iquid p r o d u c e d vapor mixed with air tha t may bu rn or explode, having ei ther a m a x i m u m exper imenta l safe gap (MESG) value greater than 0.75 m m or a m i n i m u m ignit ion cur ren t (MIC) ratio greater t h a n 0.80. SUBSTANTIATION: O n e of the major reasons for providing new group defini t ions was to provide specific guidance as to what materials were in the NEC def ined Groups, as directed by the recen t NFPA Standards Council r e commenda t ions . T he tradit ional te rminology "gases or vapors of equivalent hazard" was cons idered to be vague and of little value in de t e rmin ing precisely what at tr ibutes were requi red for materials to be organized into c o m m o n groups. The t rue basis for placing a material into an NEC def ined group ' i s reflected by the materials pe r fo rmance ei ther by testing for the MESG or the MIC ratio values. Since the Group definit ions mus t reside both within the NEC and this documen t , it is impor tan t tha t they be clear a n d definitive. Use of this (NFPA

497) documen t ' s def ined te rm "combust ible material" within the ' g roup defini t ions will no t pe rmi t definitive u n d e r s t a n d i n g within the broader context of Article 500, which addresses f lammable gases a n d vapors, combust ib le dusts a n d ignitable fibers. Thus for correlat ion purposes the g roup defini t ions shou ld be identical in both documen t s .

As a fu r ther clarification, with the c u r r e n t p r o p o s e d definitions, all materials with MESG values less than 0 . 4 5 m m or MIC ratios less than 0.4 become Group B. Group A becomes an historical r e m n a n t referr ing jus t to Acetylene.

It shou ld also be indicated tha t the defini t ion of the NEC Groups A, B, C, and D with MESG and MIC ratio values will provide a technically s o u n d basis upon which Article 505, Groups may be organized as the nex t act ion of the EECA Commit tee . Group IIC will be f o u n d to be equal to Groups A and B. Group lIB will be equal to Group C, and Group IIA will be equal to Group D. In terms of applying this g roup criteria to actual apparatus , based upon cur ren t practice u n d e r IEC and CENELEC procedures , the following special markings are used: For hydrogen, the appara tus applicat ion would be identif ied as I IB+ H2; for carbon disulfide, I IB+ CS2; a n d for ethyl nitrate, I IB+ C 2H5NO 3. The revised

endix material contains no new data or informat ion. TTEE ACTION: Accept in Principle.

Insert th ree Notes after the Group definit ions to read as follows: Group B: F lammable gas ..... (MIC) ratio less t han 0.40. NOTE: A typical Class I, Group B material is hydrogen. Group C: F lammable gas ....... between 0.40 and 0.80. NOTE: A typical Class I, Group C material is ethylene. Group D: F lammable gas ......... ratio greater t han 0.80. NOTE: A typical Class I, Group D material is p ropane .

COMMITTEE STATEMENT: These Notes have been added to provide clarity as to the types of materials covered in the various Group defini t ions.

The Commi t t ee believes tha t the submit ter ' s substant ia t ion shou ld m o r e appropriately use the te rm "equivalent" ra ther than "equal" in the discussion of the Class I, Zone Groups and Class I, Division Groups . NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #12) 497A- 3 - (Table 2-1 ): Accept SUBMITrER: David Wechsler , U n i o n Carbide Corp. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: In table 2-1, for acetylene, un d e r the field "type" change the 'T ' to "GAS". SUBSTANTIATION: Acetylene is a gas at normal ambien t t empera tu re and not an NFPA Class I type of f l ammable liquid per NFPA 325. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #3) 497A- 4 - (3-2.2): Reject SUBMITTER: J o h n Propst , Shell Oil Products Co. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: Change the example "vessel" to "pump." SUBSTANTIATION: Paragraph 3-2.2 presents an example to demons t r a t e the application of a Division 2 location. Unfortunately, the example uses a vessel as the example of a piece of e q u i p m e n t tha t is normal ly t ight bu t it could have an abnormal leak. It is no t an abnormal si tuation in the pe t ro l eum industry to have leaking vessels. A vessel leak would typically fall into the catastrophic failure category for which convent ional area classification techniques do no t apply. This proposal would chan~e the example to a p u m p ra ther than a vessel. It is industry practice to consider a p u m p leak an abnormal s i tuat ion and apply a Division 2 classification. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The t e rm "vessel" covers p u m p s and many o ther types of containers or tanks and m o r e adequately addresses all of the various types of potential leaks. T h e term "pump" is too narrow an example a n d could lead to confusion by the user by implying tha t we are only address ing pumps . A leak in a vessel is no t always a catastrophic event a n d could involve small p inholes and o ther areas of potential leaks. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #4) 497A- 5 - (3-3.3): Reject SUBMITTER: J o h n Propst , Shell Oil Products Co. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: In Section 3-3.3 delete the words "in pumps , valves, etc., or in waste p roduc t a n d fuel feed lines." SUBSTANTIATION: The text of this pa rag raph could lead the reader to consider the listed e q u i p m e n t as be ing sources. This could cause confusion. The d o c u m e n t already provides guidance for the reader to de te rmine which e q u i p m e n t shou ld be cons idered sources. A sugges ted s h o p p i n g list of sources in this paragraph is no t needed . COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: Byprov id ing examples of potential sources of leaks, the informat ion does provide clarity of some e q u i p m e n t tha t could be cons idered as possible sources of leaks. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #5) 497A- 6 - (3-6.1): Accept in Principle in Part SUBMITTER: J o h n Propst , Shell Oil Products Co. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: The correct title for API RP-500 is " R e c o m m e n d e d Practice for

Classification of Locations for Electrical Installations at Pe t ro leum Facilities Classified as Class I, Division I, or Division 2."

Also, change "refinery" to "pe t ro leum facilities" irl the text for

~ aragraph 3-6.1. UBSTANTIATION: Paragraph 3-6.1 does no t have the correct

title for API RP-500. The scope o fAPI RP-500 is no t "refineries," bu t r a the r is "Pet ro leum Facilities," which includes p e t ro l eu m product ion , manufac tu r ing , a n d t ranspor ta t ion facilities.

2 2 4

N F P A 4 9 7 A - - A 9 7 R O C

COMMITTEE ACTION: Accept in Principle in Part. The actual title of flais API d o c u m e n t in Section 3-6.1 shou ld read

as follows and change the word "Refinery" to "pe t ro leum facility" in two places in the paragraph: 3-6.1 The practices of the pe t ro l eum refining industry are publ i shed in the Amer ican Pe t ro leum lnst i tute 's RP 500, " R e c o m m e n d e d Practice for Classification of Locations for Electrical Installat ions at Pe t ro leum Facilities." These practices are based on an analysis of the practices of a large s e g m e n t of the industry, exper imenta l data, and careful weighing of per t inen t factors~ Pe t ro leum facility opera t ions are characterized by the handl ing , processing, and storage of large quanti t ies of materials, often at elevated tempera tures . T h e r e c o m m e n d e d limits of classified areas for pe t ro l eum facility installations may therefore be stricter than are war ran ted for more traditional chemical process ing facilities tha t hand le smal ler quantit ies. COMMITTEE STATEiMENT: T he Commi t tee verified with API in Washington , DC tha t Amer ican Pe t ro leum Institute's RP 500, " R e c o m m e n d e d Practice for Classification of Locations for Electrical Installations at Pe t ro leum Facilities." is the actual t ide a n d no t the title as given by the submitter . The Commi t tee did accept the change f rom "refinery" to "pe t ro leum facilities". NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #6) 497A- 7 - (3-6.3): Accept in Principle SUBMITTER: J o h n Propst , Shell Oil Products Co. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: Delete pa ragraph 3-6.3. SUBSTANTIATION: The s t a t emen t "The vo lume of leakage f rom p u m p ... glands, p iping flanges, and valves increased proport ional ly with the process e q u i p m e n t size and flow rate ..." is teclmically incorrect and canno t be substant ia ted by technical data. In today's world of extensive EPA regulat ions, p u m p a n d valve seal technology has changed dramatically. The leakage rate f rom p u m p s mad valves unde r abnormal condi t ions is more d e p e n d e n t u p o n the seal technology used than the size a n d flow rate. NFPA 497 needs to s top perpe tua t ing the belief tha t big e q u i p m e n t leaks a lot and small e q u i p m e n t doesn ' t . This j u s t isn't the case. Seal manufac tu re r s will provide uses with calculated leakage rates u n d e r abnormal condit ions such as pr imary seal failure if the use will provide the manufac tu re r with the correct applicat ion data. This proposal is to el iminate this pa ragraph in total because it is no t technically correct. COMMITTEE ACTION: Accept in Principle.

Delete the last sen tence in the Section and change the second sen tence in Section 3-6.3 to read as follows:

"Leakage f rom p u m p and agitator s h a f t p a c k i n g glands, p iping flanges, and valves general ly increases with process e q u i p m e n t size. pressure, and flow rate, as does the travel distance and area of d ispers ion f rom the discharge source." COMMITTEE STATEMENT: While small e q u i p m e n t can also p roduce large leaks unde r certain failure conditions, generally, larger e q u i p m e n t and seals do have the potential to leak greater volumes of material than smal ler equ ipmen t , d e p e n d i n g upon the pressure a n d potential failure condit ions. T he change in text addresses the submi t teds concerns and yet still provides the informat ion that large leaks may occur a n d alerts the user to this possibility° NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24 COMMENT ON AFFIRMATIVE:

SAVERINO: Comment : Change second sen tence of 3-6.3 to read: 3-6.3 Con t inuous process plants. . .of the ref ining industry. T h e

potential vo lume of leakage f rom p u m p and agitator shaft packing glands, piping, flanges, and valves general ly increases with process e q u i p m e n t size, pressure, a n d flow rate, as does the travel dis tance a n d area of dispersion f rom the discharge source."

Substantiat ion: T h e Commi t t ee Action to accept in principle by modifying the second sen tence of 3-6.3 is basically correct bu t can be improved. I suggest that the second sentence be modif ied as no ted above to m o r e closely address the submit ter ' s (Mr. Propst 's) concerns while still alert ing the user to the ~ that large leaks may occur.

(Log #8) 497A- 8 - (3-7.4.1): Reject SUBMITTER: J o h n Propst , Shell Oil Products Co. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: Add the following sen tence at the end of existing Section 3-7.4.1:

Objects such as co lumns, valves, and similar process hardware shown in f igures 3-8.1 t h r o u g h 3-8.34 shown to depic t possible sources f o r h y d r o c a r b o n release a n d are no t in t ended to imply that these devices should always or even rout inely be cons idered sources. Sound eng ineer ing j u d g m e n t mus t be appl ied in def in ing potent ia l sources. SUBSTANTIATION: Proposals 497A-13 and 497-14 were submi t ted to address the confus ion in the implied defini t ion of sources within the figures in 497. I do no t feel tha t the commit tee ' s s t a t emen t nor proposed new text has adequately addressed this issue. I continiae to hear people insist tha t valves shou ld be considered sources based solely on the fact that figure 3-8.14 has a source arrow poin t ing to a value° While we can certainly a rgue that if these people wou ld read the words as well as look at the pictures, there would no t be this cont inued confusion. The fact is that the confusion is ou t in industry. An addit ional s t a t emen t as shown above migh t provide coaching to many in industry that a rea classification mus t be based on facts a n d no t ju s t past practice. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: Section 3-7.4 qualifies the application to apply sound eng inee r ing j u d g e m e n t already. Any valve shou ld be looked at as a potential source of leaks and sound eng inee r ing j u d g e m e n t may conclude a specific valve construct ion may no t leak. The text already addresses the submit ter ' s concerns. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #9) 497A- 9 - (3-7.4.3): Reject SUBMITTER: J o h n Propst , Shell Oil Products Co. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: Change the word " m i n i m u m " to "max imum." SUBSTANTIATION: Area classification deals with the m a x i m u m ant icipated extent of the material vapor cloud, no t the m i n i m u m . COMMIT/'EE ACTION: Reject. COMMITTEE STATEMENT: The word "min imum" is based u p o n NFPA 30 and 58 for the requi red boundar ies and thus "m in im u m " is the correct word. T h e s e b o u n d a r i e s may be ex tended to any value beyond these m i n i m u m areas based upon s o u n d engineer ing jl~dg ements .

UMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #CC2) 497A- 10 - (Title Figure 3-8.5): Accept SUBMITTER: Technica l Commi t t ee on Electrical Equ ip m en t in Chemical A tmospheres COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: In the Tide of Figure 3-8.25, change the text to read as follows:

"Emergency i m p o u n d i n g basin or o i l /water separa tor (to~) and emergency dra inage di tch or o i l /water separa tor (bot tom). SUBSTANTIATION: This is strictly an editorial correction of the tide for the figure. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #10) 497A- 11 - (4-1.3): Accept SUBMITTER: J o h n Propst , Shell Oil Products Co. COMMENT ON PROPOSAL NO: 497A-I5 RECOMMENDATION: The correct title for API RP-500 is " R e c o m m e n d e d Practice for Classification of Locations for Electrical Installations at Pe t ro leum Facilities." SUBSTANTIATION: The wrong title is shown for API RP-500. COMMITTEE ACTION: Accept.

225

NFPA 497A~ A97 ROC

NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #2) 497A- 12- (A-3-7.3): Hold SUBMITTER: David Wechsler , U n i o n Carbide Corp. COMMENT O N PROPOSAL NO: 497A-15 RECOMMENDATION: Replace entire A-3-7.3 with the material shown below.

The user may wish to use the me thodo logy discussed here, which is based u p o n the Inst i tute of Pe t ro leum, Area Classification Code for Pe t ro leum Installations, Part 15, March 1990, to fu r ther assess the hydrocarbon ' s volatility as an added measu re of deriving the ex ten t of the classification for ventilated, Class I, Division 2, electrically classified areas. In the event this me t hodo l ogy is employed, the user shou ld fully d o c u m e n t the rational and the considera t ions as par t of the a rea electrical classification process.

The me thodo logy begins by placing the hydrocarbon of interest into one of fou r categories, as shown in Figure A-3-7.3.1 below.

Flammable Liquids ]C~oPmb~'us°~ibble

P r o c e s s o r S t o r a g e T e m p e r a t u r e

Figure A-3-7.3.1 Process or Storage T empera t u r e

Figure A-3-7.3.1 shows a plot of t empera tu re versus vapor pressure with four volatility categories (Note: 750 m m Hg = 1 bar = " 14.5

P°c_~tegory I is cons idered the mos t volatile materials a n d inc luded LPG and f l ammable gases. Category 2 includes NFPA 30 Class 1A Flammable Liquids p l u s all mater ia ls with a vapor pressure exceeding 750 m m Hg. Category 3 includes NFPA 30 Class 1B, 1C, 2 and 3 combust ib le h'quids tha t are above thei r flash points. Category 4 includes NFPA Class 2 a n d 3 combust ib le liquids tha t are below thei r flash points which would fall into a category no t likely requi r ing the use of special electrical equ ipmen t .

Once the source category 1,Z 3, or 4, is selected, the me thodo logy t hen relates the category o f volatility of the hydroca rbon to the flow rate, as shown in Figure A-3-7.3.2, to di f ferent hazard indice, in a m a n n e r similar to tha t def ined in this practice us ing the low, m e d i u m , h i gh criteria.

Hazard Indic-~

Figure A-3-7.3.2.

Figure A-3-7.3.2 Category-flow rate-Hazard Indice: displays how the flow rate is divided into the three categories of low, med ium, and h igh as follows: Low is less than 100 gal lons per minute ; M e d i u m is 100 to 500 gallons per minute ; High is greater than 500 to 1000 gallons per minute .

While the Hazard Indice Matrix has 9 indice shown for the various combina t ions of material category a n d flow rate, it is actually a c o n t i n u u m in which eng inee r ing j u d g m e n t should be applied when ei ther the category or the flow fate is nea r the interface. For example if the material is located near the Category 2-3 interface and the flow rate is on the low to m e d i u m interface, a hazard indice of 5 to 10 may be used.

Figure A-3-7.3.4 a n d its char t (Figure A-3-7.3.3) below demons t r a t e how the Hazard Indice value would be applied to open air (adequately venti lated) sources of heavier t h an air materials .

HAZARD INDICE D 1 D 2 (Fr) ( ~ ) ( ~ ) D 3 H~

(Fr ) (FT) (FT) 3 3 3 0 NA 7 1.5 5 5 5 0 NA 10 1.5

10 10 10 0 NA 10 2 15 15 15 0 NA 10 2 25 2O 2O 5 10 20 2 50 25 25 25 25 25 2

100 25 25 25 25 50 2

F~gure A-3-7.3.3 Char t (above) relat ing the Hazard Indice with the extents of the area electrical classification (Figure A-3-7.3.4)

Fieure A3-7.32J Chart (above} rehtlntt the Hazard Ind ice with t_he ¢xtenL~ off the area e lec t r i ca l ( l : igure A~.7.3.41 COeIOW}

¢,x~0,\x

ZUC3 A~ a * U ~ ax ~-~c~

Figure A-3-7.3.4

Having d e t e r m i n e d the material volatility, a n d assessed the flow rate, specific details of the processing e q u i p m e n t can be evaluated to derive a family of hazard indices. These can t h e n be utilized to develop an overall a rea electrical classification. SUBSTANTIATION: The in format ion sugges ted in Append ix A-3.7.3 conta ins valuable advice and shou ld be par t of this documen t . However, in its p roposed format , it lacks clarity, Pdrovides da ta tha t is conflict ing in some cases, a n d overall does no t

o a good j ob of expand ing on the in format ion conta ined in the body of the documen t . The sugges ted revision provides in clearer language, a s impler "hazardous indice" ra ther t han the more confus ing hazard radius, with a single f igure tha t co m p lem en t s several f igures in the ma in documen t . Confus ing tables an d texts have been removed to focus on the core aspect of be ing able to apply volatility concerns to the extent of the area electrical classification. The revised append ix material conta ins no new data or informat ion .

2 2 6

NFPA 497A-- A97 ROC

COMMITTEE ACTION: Hold. COMMITTEE STATEMENT: See the Commi t tee S ta tement on C o m m e n t 497A-15 (Log #7). NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #7) 497A- 13 - (A-3-7.3): Hold SUBMITTER: J o h n Propst , Shell Oil Products Co. COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: Following is a total r ep lacemen t for A-3-7.3 of proposed new text:

Append ix D Informative A n n e x - An Alternate Me thod for Area Classification

D-1 In t roduc t ion . D-l-1 This section presents an al ternate m e t h o d for classifying adequately venti lated locations in non-enc losed locations for electrical installations at pe t ro leum facilities. D-2 Explanat ion o f "Po i n t Source" concept. D-2-1 Developing area classification boundar ies us ing the concept of "Point Source ' i nvo lves creat ing the classified area boundar ies for all individual potential sources and t h e n supe r impos ing all of the boundar ies created by the individual poin t sources to develop a composi te classified area bounda ry for all sources combined . Usually the composi te bounda ry will be simplif ied and ex t ended beyond that def ined by each individual point. D-2-2 The r e c o m m e n d a t i o n s p resen ted below provide a m e a n s to evaluate the ex ten t of classified areas in non-enc losed adequately venti lated locations based on t he na tu re of po ten t i a l f l ammable releases. These m e a n s are being i n t r o d u c e d t o recognize that as the quant i ty of potential sources is reduced, the ex ten t of classified areas tends also to be reduced. Also, o ther factors such as the volatility of the released materials, the quant i ty of the release, weather, na tu re of the release, and the velocity of the material released can have an inf luence on the boundar ies of classified areas. This alternative m e t h o d will p resen t area classification schemes tha t consider volatility a n d release rates. D-2-3 The concep t of "Hazard Radius" is be ing in t roduced. The concep t of h a z a r d radius is a func t ion of two parameters: the volatility of the material be ing released and the rate of release of the material. For legs volatile materials with low release rates, the hazard radius is qui te small. For more volatile materials with a low release rate, or for less volatile materials with a h igh release rate, the hazard radius will be "midrange." For a highly volatile material released at a h igh rate, the h a z a r d r a d i u s will be large. The velocity of the release will have a significant inf luence on the hazard radius. High velocity releases, normal ly cons idered as releases over 50 f t /sec , will often resul t in mist ing of the material. Misting, coupled with modera te winds, can resul t in relatively large hazard radii. In a similar manne r , low velocity releases, normal ly cons idered as releases less than 10 f t /sec, will no t normally be in f luenced by weather condit ions, arm the hazard radius may be relatively small. As an example, gasoline released t h rough a f ine nozzle at a rate of 5 gallons per minu te in a 3 m p h wind would resul t in a ra ther large vapor cloud. However, gasoline p o u r e d slowly f rom a conta iner at a rate of 5 gallons per m i nu t e would have a very l imited vapor cloud, somewhat i n d e p e n d e n t of the wind velocity. Misting, vapor release rates, velocities of, vapor releases, and volatility are all impor tan t factors to consider when developing area classification boundar ies . The notes following Append ix D, extracted f rom Standard IEC 79-10, provide addi t ional in format ion on the topic of volatility and misting. D-$ De te rmina t ion of Volatility Classification. D-$-I The f lammabil i ty of various liquids, vapors, and gases is well d o c u m e n t e d (e.g., NFPA 321 Basic Classification o f F lammable a n d Combust ib le Liquids). The volatility of a material can have a significant impact on area classification. Figure D-1 is a char t used to de t e rmine the relative volatility of a material based on fluid process t empera tu re a n d fluid vapor pressure. T h e basic concept for this approach is derived f rom the INSTITUTE OF PETROLEUM publ icat ion IP-15, Area Classification Code for Pe t ro leum Installations. T h e data relat ing to the f lammabil i ty of specific materials is based primari ly on various NFPA documen t s . D-3-2 This process g roups all f l ammable liquids, vapors, a n d gases into one of five "Volatility Categories:"

Category G category includes all f l ammable fluids hand l ed or processed as gasses or vapors.

Category 1 category includes all l ight hydrocarbons (p ropane a n d l ighter hydrocarbons) and heavier f l ammable and combust ib le liquids with a vapor pressure above 70 PSIA. These materials,

w h e n released, will a lmost complete ly vaporize in a very short per iod o f t ime. Category 1 materials will a lmost immedia te ly flash to a vapor, even when they are processed in a l iquid form. For example , when liquid p r o p a n e is released, it will immedia te ly flash to a v a p o r . At 90°F a n d 150 psi, one- thi rd of p ropane will f lash immedia te ly and cool the liquid to -44°F, a n d the liquid will con t inue to boil a n d vaporize as it absorbs hea t f rom the ground. A second example would be ho t kerosene. Normally, kerosene at r o o m t empera tu re and low pressures would be cons idered an unclassified material. However, w h e n kerosene is opera ted at 500°F, the vapor pressure will be over 70 PSIA, and this ho t material would be cons idered a Category 1 material. W h e n it is released to the a tmosphere , abou t 4 5 p e r c e n t would flash to a vapor, cooling the l iquid to abou t 410°F. The r ema in ing liquid will "pool" a n d cont inue to evaporate at a r educed rate unti l it cools to ambient . Even an asphalt ic type material, when processed at very h igh tempera tures , will exhibi t similar characteristics when initially released.

Category 2 materials are all Class 1A Flammable Liquids tha t are opera ted at t empera tu res p roduc ing a vapor pressure of 70 PSIA or less and all o the r f l ammable and combust ib le liquids with a vapor pressure between 14.7 PSIA and 70 PSIA. Pen tane is an example of a Class 1A Flammable Liquid. It would be considered a Category 2 material for all cases in which the vapor pressure is less than 70 PSIA, which is a process t empera tu re of approximate ly 190°F. If Category 2 pen t ane at 140°F shou ld be released to the a tmosphere approximate ly 1 /6 would immedia te ly vaporize, and the liquid would pool, and eventually all the pen tane would evaporate. Isopropyl Alcohol would be a Category $ material at r o o m tempera ture , bu t would be a Category 2 material when opera ted above its boil ing po in t of 180°F. It would be a Category 1 material when opera ted above 265°F. As a Category 2 material at 260°F, when released to the a tmosphere , it would act similar to the pen tane example above - i.e., abou t 1 / 4 will initially flash, and the r ema inde r will have a h igh evaporation rate.

Category 3 materials are all Class 1B Flammable Liquids tha t are opera ted at t empera tures p roduc ing a vapor pressure less than 14.7 PSIA; and also all o ther f l ammable combust ib le liquids tha t are opera ted at t empera tures p roduc ing a vapor pressure less than 14.7 PSIA when the process or s torage t empera tu re is above the flash

Oint of the material. An example would be kerosene at 150°F. A ak of this material would flash very little vapor, and the resul t ing

pool would have a modera te evaporat ion rate. Category 4 materials are all Class 1C a n d heavier materials that

are opera ted below their flash point. Examples of Category 4 materials would be kerosene, lubricat ion oil, asphalt , an d diesel fuel h a n d l e d at r o o m tempera ture . These materials will no t p roduce a f lammable fuel-air mix ture w h e n released at opera t ing condit ions. W h e n operated at elevated tempera tures , mos t of these materials are in a h igher hazard category.

Note: The following Standards provide addit ional informat ion on the proper t ies of f l ammable a n d combust ib le liquids, gases, a n d volatile solids:

NFPA 391 Basic Classification of F lammable a n d Combust ib le Liquids

NFPA 325 Fire Hazard Propert ies of F lammable Liquids, Gases, a n d Volatile Solids

NFPA 497 Classification of Class 1 Hazardous (Classified) Locations For Electrical Installations In Chemical Process Areas.

The notes following Append ix D provide addit ional in format ion conce rn ing volatility of sources, as extracted f rom Standard IEC 79- 10.

D ~ Dete rmina t ion o f the Hazard Radius for Area Classification Purposes. If one knows ei ther (a) the opera t ing or storage t empera tu re of a specific material , or (b) bo th the t empera tu re a n d vapor pressure of any f lammable or combust ib le material, they can de te rmine whether the material is a Category 1, 2, 3, or 4 material . For materials in Categories 1, 9, $, a n d 4, the extent of the classified area, or "Hazard Radius," will be a func t ion of the material release rate and the dispersion rate of the gases an d vapors. Section D-5 addresses heavier-than-air sources located in non-enclosed, adequate ly vent i la ted locations. Section D-6 addresses l ighter-than-air sources located in non-enclosed, adequate ly venti lated areas. D-5 Applicat ion to non-enclosed, adequate ly venti lated locations con ta in ing a heavier-than-air gas or vapor source. D-5-1 General . The matr ix in Figure D-2 provides a m e a n s for de t e rmin ing a hazard radius as a func t ion of the volatility category and the release rate. Us ing the matrix, a Category $ fluid with a release rate of less than 10 g p m would result in a Hazard Radius of 3 ft. A Category 1 fluid with a release rate of between 50 an d 100 g p m would result in a hazard radius of 50 to 100 ft. O n e shou ld recognize that both the volatility categories and the p roduc t release rates are actually a c o n t i n u u m rather t han absolute, and one

2 2 7

NFPA 4 9 7 A ~ A97 ROC

shou ld use good eng inee r ing j u d g m e n t in de t e rmin ing hazard radius. This m e t h o d shou ld n o t b e used for classifying locations when the ant icipated release rate f rom a source exceeds 100 gpm. The hazard radii p resen ted are based on sources with some mis t ing or imp ingemen t . As the level o f mis t ing increases one should expect that the hazard radius would also increase. Conversely, sources with extremely low release velocities could have appreciably smaller hazard radii. T h e na tu re of con_figuration of the source of the release can have a significant impact on the hazard radius.

_< ¢.0 ]4. n

ffl

~ 1.- ~

p . . l . ~

0.01 (el IF)

- I00-50 0 50 !00 150 200 250 300 350 -t48 -5B 32 122 212 302 392 482 572 662

Process or Storage Temperature Figure D-t

V~por Pre;£tlrQ - Tgmporatum Vo(atility Chart

Fluid Temperature

f l Category 1' ~ - - ~

q Category3 }..... ~

I category4 I

Hazard Radius

5-25 25-50 50-100

3-5 5-25 26-60

3 3-6 5-25

Mass Release Rate J ll" "ml <Io I I Ioso I gaVmin II geVmin I

Figure D-2 Volatility - Release Rate Matrix for Determining Hazard Radius

With knowledge of the volatility category and the source release rate, one can en te r the matr ix in Figure D-2 and de t e rmine a hazard radius. This hazard radius shou ld be used in conjunc t ion with the r e c o m m e n d a t i o n s below for de t e rmin ing the ex ten t of classified areas.

It often is qui te difficult to de te rmine the hazard radius for s t reams that conta in a mix ture of different c o m p o n e n t s of which some are volatile hydrocarbons . T h e reason for this is twofold. First, du r i ng a release, it is somet imes difficult to know the e x t e n t of dispersion for a hydroca rbon mixture . Second, the majority of techmcal da ta per ta in ing to area classification groups only addresses pure c o m p o n e n t s and does no t address mixtures. (See Section 3.5, which addresses hydrogen sulfide and m e t h a n e mixtures) . The first concern can be addressed to some extent us ing commercia l ly available d ispers ion mode l i ng programs. Using these programs, one can achieve indicat ions of the Lower Flammable Limit (LFL) and 50 pe rcen t LFL for gas mixtures. It shou ld be no ted that dispersion mode l i ng of ten requires special skills a n d knowledge for one to apply the techniques . Beyond the gu idance provided in Section 3.5, testing is current ly the only reliable m e t h o d for de t e rmin ing the group for gas mixtures. The hazard radius matr ix shown in Figure D-2 can be applied to mixtures to de te rmine the extent o f the classified location. In the case of mixtures, one would first de t e rmine the mass release rate for the volatile por t ion of the mixture. Assuming that all of the volatile hydrocarbons are freely dissipated f rom the mixture dur ing the release, one can then de te rmine both the category and rate of release for tha t por t ion and de te rmine a hazard radius. This m e t h o d will result in a conservative hazard radius.

The following sections provide two m e t h o d s for de t e rmin ing the boundar ies of classified locations. The reader is r e m i n d e d that the m e t h o d is valid only for non-enclosed, adequate ly venti lated locations. D-5-2 Point Source Located near or above Grade - Adequately Venti lated Location. The first me thod , us in~ the hazard radius f rom figure 2 applied to a poin t source, results in the envelopes shown in Figure D-3

Extent of Division h Areas that should be classified as Division 1 are negligible for above-grade locations. Most Division 1 locations will be l imited to below-grade locations such as pits, sumps, a n d t renches . Such below grade locations may collect f lammable liquids or gases, which can t hen be t ranspor ted to o ther locations by bur ied condui ts unless prevented by p roper sealing, purg ing water traps, or similar measures .

Extent of Division 2: Use clearances given in Figure D-3.

~¢. (rq (r~ {~ (eq (vq ffq 3 3 3 0 r,~ 7 t.6 5 5 5 0 tL~ 10 1,3 10 10 10 0 r~ tO Z 1: 1: 13 0 ~ 10 2

, Z= 29 20 . 10 20 2 i 2~ ~ 2S 2S 2

100 25 25 25 2s so 2

D,

- - 6 - -

" SOHd-PlOIf~mAbovaC, nde ~ , [ ~ ~ .

• ii

ADIQUATF.J.y VF..NTU.ATIED PROGP.88 AREA WITH If.AVIER-TIIAN-AIR GAS OR VAPOiq SOURCE LOCATED NEAR OR ABOVE GRADE

228

NFPA 4 9 7 A - - A 9 7 R O C

Oftent imes one does no t have specific da ta on the release rate f rom a source, bu t addi t ional in format ion is available abou t the source. As an alternative to us ing the Category/Release R a t e / H a z a r d Radius approach , the following provides gu idance for specific types of sources of ten f o u n d in pe t ro l eum process areas. D-5-3 PUMPS - Adequate ly Venti lated Area. The release rate f rom process p u m p s typically is a func t ion of the type of pump, the type of shaft sealing, the physical size of the p u m p , and the p u m p seal chambe r pressure (the pressure in the cavity internal to the p u m p shaft seal, also referred to as the s tuff ing box pressure) . Most horizontal shaft pumps have a seal chambe r pressure near the p u m p suct ion pressure, whereas mos t vertical p u m p s have seal chambe r pressures near p u m p discharge pressure. A l though p u m p seal d l a m b e r pressure t ends to be the driving force beh ind a release, the p u m p seal technology often creates the restriction that de te rmines the release rare. For some p u m p s typically used a r o u n d very hazardous materials, the seals may be des igned with dual sealing chambers , buffer gases, and o ther detect ion and alarm technology such tha t even u n d e r abnormal c i rcumstances the seal would no t be cons idered a source of release. The matr ix in Figure D-4 provides gu idance in de t e rmin ing tbe hazard radius for various types of pumps .

' - v " u m ' $ i ~ . .F~ . - . * ~ . ~ * . , , F N . t - , . . .p I

{{,J J{Jd,J{Jd _,.,oo,.,. { S/~taartl Pump 2 10 15 25 10 25 50 15 25 ~)

3 3 10 15 5 10 25 1$ 25 t$ t.tmam Radiul

High Techm:k~y , s 10 is S '10 ~ 10 10 ~5 Lttw Seal Emmbmkmtt 2 3 5 10 3 ~ ,u S 10 10 Ft.

Pump 3 3 3 S 3 3 5 5 S tO

f rom these joints , it is likely to be small. D e p e n d i n g u p o n the na tu re of the facility, the level of ma in tenance , a n d past experience, a nomina l hazard radius of 0 to 3 ft f rom the per iphery of the f lange or valve may be a s s u m e d for such jo in t s on well-maintained systems provided there are no factors tha t could increase leakage (for example , pressure or thermal shocks, inc luding the effect of rain, or excessive p ip ing loads on the f langed jo ints) . For certain f langes that offer a h igher probabil i ty of leakage, such as those a round filter manways, vessel manways, a n d hea t exchanger heads that require bund le pulling, one should consider increasing the hazard radius as show in Figure D-7:

Fluid Category

2 o r G

Hazard Radius (ft) 10 10 5

Figure D-7 Flanges and Valves Conta in ing Heavier-Than-Air Gases or Vapors with a Higher Probability of Leakage

Note tha t area classification does no t consider catastrophic or rare failures such as the failure of a gasket due to freezing or over- pressur ing .

D-6 De te rmin ing the Hazard Radius for Sources Hand l ing Lighter- Than-Air Gases and Vapors. The following r e c o m m e n d a t i o n s an d guides apply to sources hand l ing l ighter-than-air gases an d vapors. D-6-1 Point Source Located Above Grade.

Figure D-8 depicts the r e c o m m e n d e d hazard radius for "point" sources conta in ing l ighter-than-air gases or vapors.

FIgulm D-4 P U M P S H A N D L I N G H E A ~ q E R - T H A N J U R GASES OR V A P O R S L O C A T E D IN

N O N - E N C L O S E D A D E Q U A T E L Y V E N T I L A T E D PROCESS AREAS

D-5-4 P u m p s Conta in ing M ed i um and Low Pressure Restrict ions (Orifices, Drains, Etc.).

Figure D-5 applies to any type of potential source in a m e d i u m or low pressure system that has a restrict ion orifice or similar restriction to reduce the rate of release of the source.

Hazard Radius for Restrictions Restrict ion Diamete r (inches)

Catelgory .1 25 .25 .5 1 1 25 50 100 2 or G 10 25 50 100 3 3 5 5 lO

Figure D-5 Dete rmin ing Hazard Radius for Sources with Restrictions for Heavier-Than-Air Gases or Vapors

D-5-5 Compressors . For bo th reciprocat ing and axial flow compressors hand l ing heavier-than-air gases or vapors, the r e c o m m e n d e d Hazard Radius is 50 ft except: • T h e radius may be reduced to 25 ft for pressures below 20 bar(abs) and shaft d iameters of 2 in. or less. • For d i aph ragm compressors , the Hazard Radius may be reduced to 10 ft. Note, however, any vents or drains at the location mus t be cons idered separately. • Advanced seal t echnology may allow a r educed Hazard Radius if so de t e rmined by good eng inee r ing j u d g m e n t . D-5-6 I n s t r u m e n t and Process Vents and Drains to Atmosphere . Figure D-6 applies to a tmospher ic process vents d ischarging a heavier-than-air gas or vapor at a velocity of 500 f t / s ec or less.

Venti lat ion Rate at A mbi en t Condi t ions Hazard Radius (ftS/hr) (it)

Less than 300 10 300 - 3000 25

3000 - 6000 50

Figure D-6 Atmospheric Vents and Drains Hand l ing Heavler-Than- Air Gases or Vapors

D-5-7 Flanges and Valves. Many f langed jo in t s are rarely broken, for example, only du r ing major m a i n t e n a n c e work, and t hen typically at intervals of two or more years, ff there is any leakage

229

. -

I Op~ ~r (rtkm~ I~Ii'W thin U)

Ground or

Figure D-it HAZARD RADIUS FOR PO4NT SOURCES CONTAINING LIGHTER-THAN-AiR GASES OR VAPORS

D-6-2 Compressors . For both reciprocat ing and axial flow compressors , the r e c o m m e n d e d hazard radius for l ighter-than-air releases is 15 ft. D-7 Applicat ion to Inadequate ly Venti lated Areas. For sources located in inadequately venti lated areas, the ex ten t of the classified location no t only is a factor of the volatility of the gas or vapor released, the velocity of the release, and the rate of the release, bu t it also is (perhaps, even more impor tant ) a funct ion of the degree of ventilation, the ability to de tec t hydrocarbon releases, an d the ability to r e spond to hydrocarbon releases. The methodo logy p resen ted in Append ix D of API RP 500 is N O T r e c o m m e n d e d for applicat ions in enclosed or inadequate ly venti lated areas. In addi t ion to API RP 500, o ther sources of informat ion per ta in ing to the classification of enclosed and inadequate ly venti lated areas can be f o u n d in the following references: • NFPA 497, 1997 edition; Guide to Fire Hazard Propert ies of F lammable Liquids, Gases, and Volatile Solids. • IP 15, Insti tute of Pe t ro leum Area Classification Code for Pe t ro leum Installations. • IEC 79-10, Electrical Appara tus for Explosive Gas Atmospheres , Classification of Hazardous Areas.

Appendix D Notes

[The following Extracted f rom the latest Draft of IEC 79-10]

Mists. Mists may form or be p resen t at the same t ime as f lammable vapors. This may affect the way f lammable material disperses a n d the ex ten t of any hazardous areas. T h e strict

NFPA 497A A97 ROC

appl icat ion of a rea classification for gases and vapors may n o t be appropr ia te because the f lammabil i ty characteristics of mists are no t always predictable. Whilst it can be difficult to decide u p o n the type a n d ex ten t of zones, the criteria applicable to gases and vapors will, in mos t cases, give a safe result. However, special considerat ion shou ld always be given to the dange r of ignit ion of f l ammable mists.

The greater the release rate the larger the ex ten t of the [classified location] zone. The release rate d e p e n d s itself on o ther parameters , namely:

(a) Geometry of the source of release This is related to the physical characteristics of the source of

release, for example an open surface, leaking flange, etc. (see a n n e x A).

(b) Release velocity For a given source of release, the release rate increases with the

release velocity. In the case of a p roduc t conta ined within the process equ ipmen t , the release velocity is related to the process pressure and the geomet ry of the source of release. The size of a c loud of f l ammable gas or vapor is de t e rmi ned by the rate of f l ammable . . . . vapor release a n d the rate of dispersion. Gas a n d vapor flowing f rom a leak at h igh velocity will develop a cone-shaped j e t which will en t ra in air a n d be self-diluting. The extent of the explosive a t m o s p h e r e will be a lmost i n d e p e n d e n t of wind velocity. If the release is at low velocity or if its velocity is destroyed by i m p i n g e m e n t on a solid object, it will be carr ied by the wind and its di lut ion and extent will d e p e n d on wind velocity.

(c) Concent ra t ion The release rate increases with the concent ra t ion of f l ammable

vapor or gas in the re leased mixture . (d) Volatility of a f l ammable l iquid This is related principally to tile vapor pressure, and the hea t of

vaporization. If the vapor pressure is no t known, the boi l ing po in t mad f lashpoin t can be used as a guide.

An explosive a tmosphe re canno t exist if tile f lashpoint is above the re levant m a x i m u m t empera tu re of the f lammable liquid. The lower the f lashpoint , the grea ter may be the ex ten t of the zone. If a f l ammable material is re leased in a way that fo rms a mist (for example by spraying) an explosive a t mosphe re may be f o r m e d below the f lashpoint of the material for example.

NOTE 1: Flashpoints of f l ammable liquids are no t precise physical quanti t ies, particularly where mix tures are involved.

NOTE 2: Some liquids (for example certain ha logena t ed hydrocarbons) do no t possess a f lashpoint a l t hough they are capable of p roduc ing an explosive gas a tmosphere . In these cases, the equi l ibr ium liquid t empera tu re which cor responds to the sa tura ted concent ra t ion at the lower explosive l imit shou ld be compared with the relevant m a x i m u m liquid t empera ture .

(e) Liquid t empera tu re The vapor pressure increases with t empera ture , thus increas ing

the release rate due to evaporation. NOTE: The t empera tu re of the l iquid after it has been released

may be increased, for example, by a ho t surface or by a h igh ambien t tempera ture . SUBSTANTIATION: Paragraph A-3-7.3 is original work which I developed dur ing the past 2 years as a working m e m b e r o f the API RP-500 task group responsible for upda t ing API RP-500. T h e d o c u m e n t was based on an app roach developed in IP-15 to try and incorporate volatility into the classification process. Dur ing the deve lopmen t of dais idea, it was ref ined to include a matr ix tha t would combine volatility a n d release rates into a hazard radius. Dur ing the deve lopmen t of this d o c u m e n t , I worked with David Wechsler (a m e m b e r of your working group) to fu r the r ref ine the app roach a n d a t t empt to create a d o c u m e n t tha t was consis tent with bo th API RP-500 and NFPA 497. At the t ime the NFPA 497 task g roup began thei r work, I encouraged Mr. Wechs ler to integrate dais work into NFPA 497. At the same t ime I con t inued work to integrate the concept into RP-500. Over the course of time, several changes were in t roduced into the proposal. The C o m m e n t s which Mr. Wechs le r submi t t ed in his c o m m e n t s to 497A-15 reflected, in part, addit ional changes and concepts which we felt would he lp improve, clarify, a n d improve the approach° While the c o m m e n t s submi t t ed by Mr. Wechs ler to NFPA 497 is a shor t and simplified version of the work that I created for RP-500, the two approaches are technical ly very similar with one exception. The difference is in the 3 by 3 matr ix in which volatility and release rates are comb ined to derive a hazard radius. T he d o c u m e n t which I have developed for and which is current ly be ing inc luded in the revised version of RP-500 as an informative a n n e x combines volatility a n d actual release rates to arrive at a hazard radius. This approach has been correlated with the IP-15 r ecommenda t ions . I have also pe r fo rmed a large n u m b e r of dispersion mode l s for a wide variety of hydrocarbons to fu r the r suppor t the values in the table. T h e 3 by 3 matr ix shown in the p roposed draft for 497

represents the release rates as a func t ion of e q u i p m e n t flow rates. The re is no technical da ta p resen ted tha t correlates the flow rate of e q u i p m e n t with the release rate of equ ipmen t . In fact the text of the original proposal clearly points out tha t release rates are a func t ion o f the e q u i p m e n t design and o ther factors o ther than the hardware rated flow ra tes . Based on the large n u m b e r of dispersion models which I conduc t ed in developing an d ref ining this approach, it is my belief tha t the 3 by 3 matr ix p resen ted in NFPA 497 is technically incorrec t a n d shou ld no t be used. Th e a t tached d o c u m e n t is the cu r ren t proposal tha t I have submi t ted to the API RP 500 task g roup for inclus ion in the revised s tandard. We anticipate tha t revisedRP-500 will be comple ted an d approved du r ing 1997. It is also the proposal I have submi t ted an d tha t is inc luded in Draft 1 of ISA-dRP 12.24.01 t ided " R e c o m m e n d e d Practice for Classification of Locat ions for Electrical Installations Classified as Class 1, Zone 0, Zone 1, Zone 2". This d o c u m e n t is be ing developed by ISA Subcommi t t ee SP12.24 with Mr. Lon Ballard serving as chair a n d in which I arn a member . I p r o p o s e tha t the cu r r en t A-3-7.3 shou ld be replaced in total with the a t tached documen t , which is my original work. The a t tached d o c u m e n t cu r rendy displays the pa rag raph n u m b e r i n g s ch em e used in RP-500 and would need to be r e n u m b e r e d with the appropr ia te pa rag raph n u m b e r i n g s cheme used by NFP/L COMMITTEE ACTION: Hold. COMMITTEE STATEMENT: The substant ia t ion for C o m m e n t 497A-13 (Log #7), states tha t while proposals for C o m m e n t s 497A- 12 (Log #2) and 497A-13 (Log #7) are similar, they differ in the use of the 3 by 3 matr ix in which volatility and release rates are comb ined to derive a hazard radius. The C o m m e n t 497A-13 (Log #7) substant ia t ion fu r the r indicates tha t the 3 by 3 matr ix shown in the p roposed draft for NFPA 497 represents release rates as a func t ion of e q u i p m e n t flow rates and tha t this is no t suppor ted by any technical data. The Commi t t ee notes tha t C o m m e n t 497A-13 (Log #7) which, aside f rom the references to the possible inclusion of dais material in o ther documen t s , conta ins no support ive evidence or technical support ive material to indicate tha t this app roach is technically correct, ei ther.

In evaluating the c o m m o n a n d appa rendy "agreed-upon" entry po in t for bo th these comments , i.e. the adop ted "Insti tute of Pe t ro leum, Area Classification Code for Pe t ro leum Installations", IP-15, da ted March 1990; vapor p res su re /ca tegory figure, the commit tee f inds tha t the results f rom utilizing the f igure result in in format ion tha t conflicts with the proven a n d accepted guidance

rovided within the text of the documen t . For example, owtherm®, a Class IIIB material normal ly used at elevated

t empera tu res would no t requi re the area to be classified as indicated by this figure. Fur ther , the defini t ions for Category 1, 2, 3, and 4 represen t the range of gases to Class IlI combust ib le liquids in C o m m e n t 497A-12 (Log #2), bu t only Class I f l ammable liquids and a Category G, no t shown in the figure, are addressed in C o m m e n t 497A-13 (Log #7).

The Commit tee , while no t ing these condit ions, the submit ters commen t s a n d especially the fact tha t bo th submit ters r e c o m m e n d against use o f the cur ren t append ix text, recognize tha t this work effort may p roduce worthwhile beneficial in format ion that may aid in the use o f this document . However, fu r ther work and technical suppor t is requi red and, as such, the commi t tee r e c o m m e n d s that append ix A-3-7.3 be removed, and C o m m e n t s 497A-12 (Logs #2) and 497A-13 (Log #7) be he ld for fu r ther study. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #CC1) 497A- 14 - (A-3-7.3): Accept SUBMITTER: Technica l Commi t tee on Electrical E q u i p m e n t in Chemica l A t m o s p h e r e s COMMENT ON PROPOSAL NO: 497A-15 RECOMMENDATION: Remove A-3-7.3 f rom draft for Proposal 497A-15 (Log #CP1). SUBSTANTIATION: The substant ia t ion for C o m m e n t 497A-13 (Log #7), states tha t while proposals for C o m m e n t s 497A-12 (Log #2) a n d 497A-13 (Log #7) are similar, they differ in the use of the 3 by 3 matr ix in which volatility a n d release rates are combined to derive a hazard radius. The C o m m e n t 497A-13 (Log #7) substant iat ion fu r ther indicates that the 3 by 3 matr ix shown in the p roposed draft for NFPA 497 represents release rates as a funct ion of e q u i p m e n t flow rates and tha t this is n o t suppor t ed by any technical data. The Commi t t ee notes tha t C o m m e n t 497A-13 (Log #7) which, aside f rom the references to the possible inc lus ion of this material in o ther documen t s , contains no support ive evidence

2 3 0

N F P A 4 9 7 A / 4 9 7 B ~ A 9 7 R O C

or technical support ive material to indicate that this app roach is technically correct.

In evaluat ing the c o m m o n and apparent ly "agreed-upon" entry poin t for both these comments , i.e. the adop ted "Insti tute of Pet ro leum, Area Classification Code for Pe t ro leum Installations", IP-15, da ted March 1990; vapor p ressure /ca tegory figure, the commit tee finds tha t the results f rom utilizing the f igure result in in format ion that conflicts with the proven and accepted guidance provided within the text of the document . For example, Dowtherm A®, a Class IIIB material, normal ly used at elevated tempera tures , would indicate tile a rea mus t be classified by this figure. This has no t been normal practice a n d is no t r e c o m m e n d e d based u p o n the text of the p resen t documen t . Further , the defini t ions for Category 1, 9, 3, and 4 represent the range of gases to Class III combust ible liquids. . in C o m m e n t 497A-12. (Log #2), bu t only Class I f l ammable h q m d s and a Category G, no t shown in the figure, are addressed in C o m m e n t 497A-13 (Log #7).

The Commit tee , while no t ing these condit ions, the submit te rs c o m m e n t s and especially the fact tha t both submit ters r e c o m m e n d against use of the cu r ren t append ix text, recognizes that this work effort may p roduce worthwhile beneficial informat ion that may aid in the use of this documen t . However, fu r the r work and technical suppor t is requi red and, as such, the commi t tee r e c o m m e n d s tha t tha t append ix A-3-7.3 be removed, and C o m m e n t s 497A-12 (Log #2) and497A-13 (Log #7) be held for fu r the r study. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

(Log #1) 497A- 15 - (Appendix D): Accept in Part SUBMITTER: David Wechsler , U n i o n Carbide Corp: COMMENT O N PROPOSAL NO: 497A-15 RECOMMENDATION: U n d e r Appendix D; Revise the section as shown below by the addi t ion of the def ined terms used in the formula, correct ion of the mafia pe r fo rmed for the specific example, and the correct ion of the resul t in the nex t sentence.

One m e t h o d to estimate the NEC Group is to de te rmine the MESG of the mix ture by applying a form of Le Chatielier re la t ionship shown below:.

1 M E S G M I X -

Where:

MESG mix Xi

MESG i

1 ,MESG i )

= M a x i m u m Exper imenta l Safe Gap of the mixture = volume, expressed as a decimal, of the individual

c o m p o n e n t = M a x i m u m Exper imenta l Safe Gap of the individual

c o m p o n e n t

Applying the vo lume pe rcen t and property informat ion above, results in the following equat ion:

1 0.45 0.12 0.20 0.03 0.175 0.025 = 0 .9442 - - + - - + - - + - - + - - + - - 0.65 0.97 oo 1.12 0.94 0.83

Solving the equat ion above results in an MESG mixture value of 0.94. From the defini t ions in NFPA 497 for Groups A, B, C and D, this calculated MESG value would fall u n d e r Group D. Thus this mixture may be cons idered a Group D material. SUBSTANTIATION: T he calculation pe r fo rmed produces a different result t han that reflected in the text. Additionally, iner t materials, like ni t rogen, be ing n o n combust ib le materials, shou ld be considered as having an infinite m a x i m u m exper imenta l safe gap (MESG). Thus iner t materials canno t be factored into the equat ion and shou ld be ignored by the p roposed methodology. Modifiers have been added to the equat ion to benefi t the user in

l~M~TTthe methodology. EE ACTION: Accept in Part.

Add "NFPA" before "497" in the first sen tence below the calculation. The "0.02" in the n u m e r a t o r of the last t e rm in the d e n o m i n a t o r of the calculat ion shou ld be changed to "0.025". COMMITTEE STATEMENT: The Commi t t ee disagrees with the substant ia t ion tha t iner t materials canno t be factored into the equation. These iner t materials have an effect on the end results and increase the MESG of the final mix ture thus indicating that the mixture is less hazardous. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE:. 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 24

PART II

(Log #1) 497B- 1 - (Table 2-5): Accept SUBMITTER: J o h n M. Mesina, U.S. Depa r tmen t of Labor COMMENT O N PROPOSAL NO: 497B-1 (499) RECOMMENDATION: Revise Table as toUows:

Chemical Layer or Cloud Name Cas # NEC Group Code Igni t ion T e m p °C

Lycopodium G ~1~ 190 SUBSTANTIATION: The Commi t tee S ta tement u n d e r Log No. 4 on page 363 of the ROP indicates the text in Proposal 497B-1 (Log No. CP1) has been revised in accordance with the Commi t tee Action u n d e r Log No. 4, bu t the text was in fact no t revised. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 23 N O T RETURNED: 1 Woff

(Log #2) 497B- 2 - (Table 2-5 ): Accept SUBMITTER: David Wechsler, U n i o n Carbide Corp. COMMENT ON PROPOSAL NO: 497B-1 (499) RECOMMENDATION: Change layer t empera tu re for "Lycopodium" to 190°C. SUBSTANTIATION: Commi t t ee Action on Log No. 4 for 497M-5 (3-6, Table 3-6) was to "accept in principle" which inc luded chang ing of the listed layer ignit ion t empera tu re of Lycopodium to 190°C. COMMITTEE ACTION: Accept . NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 23 N O T RETURNED: 1 Wolf

(Log #3) 497B- 3 - (3-6): Accept in Principle SUBMITTER: Richard C. Masek, Bailey Controls Comp an y COMMENT O N PROPOSAL NO: 497B-1 (499) RECOMMENDATION: Delete all of p resen t 3-6 and replace it with the following:

3-6 Procedure for Classifying Areas. The following p rocedure shou ld be used for each room, section,

or a rea be ing classified: 3-6.1 Step one - Need for Classification: The area shou ld be

classified if a combust ib le material is processed, handled , or stored.

3-6.2 Step Two - Gather ing Informat ion: 3-6.2.1 Proposed Facility Informat ion. For a p roposed facility

that exists on drawings, only a prel iminary area classification can be done so that suitable electrical e q u i p m e n t and ins t rumenta t ion can be purchased. Plants are rarely built exactly as the drawings portray and the area classification shou ld be later modi f ied based u p o n the actual facility.

3-6.2.2 Existing Facility History. For an existing facility, the individual p lant exper ience is extremely impor tan t in classifying areas within the plant. Both opera t ion and ma in t enanc e personnel in the actual p lan t shou ld be asked the following questions:

(a) Is a dus t likely to be in suspens ion in air continuously, periodically, or in termit tent ly u n d e r normal condi t ions in quanti t ies sufficient to p roduce an ignitable mixture?

231

NFPA 497B - - A 9 7 ROC

(b) Are there dus t layers or accumula t ions on surfaces deeper that 1 /8 in. (3 mm)?

(c) Are there dus t layers or accumula t ions on surfaces that makes the colors of floor or e q u i p m e n t surfaces indiscernible?

(d) What is the 24 h o u r dus t accumula t ion? (e) Is the e q u i p m e n t in good condit ion, quest ionable , or in

need of repair? Are e q u i p m e n t enclosures in good repair and prevent ing the en t rance of dust.

(f) Do ma in t enance practices result in the format ion of ignitable mixtures?

(g) Wha t e q u i p m e n t is used for dus t collection? %6.2.3 Material Density. De te rmine if the specific particle densi ty

of the dus t is at least 40 lb s / cu ft. %6.2.4 P i t t Plan. A plot plata (or similar drawing) is needed

showing all vessels, tanks, bui ld ing structures, partit ions, and similar i tems tha t would affect dispersion or p romote accumula t ion of the dust.

%6.2.5* Fire Hazard Propert ies of Combust ib le Material. The NEC group and the AIT are shown in Table 2-5 for many materials.

Note: A material may be listed in Table 2-5 u n d e r a chemical name different than the chemical n a m e used at your facility. Table 2-5.1 is provided to cross reference the CAS n u m b e r of the material to the chemical n a m e used in Table 2-5.

If materials be ing used are no t listed in Table 2-5 or in o ther reputable chemical references, the need to classify the area may be obta ined by the following:

(a) Contact the material supplier to de t e rmine if the material has been g roup classified, oF

(b) Have the material tested to de te rmine if the ignit ion sensitivity is less than 0.2 and the explosion severity is less than 0.5. Area classification is no t cons idered necessary for dusts tha t mee t both criteria.

3-6.3* Step Three - Selecting the Appropr ia te Classification Diagram. Select the appropr ia te d iagrams based upon the following:

(a) whe the r the process e q u i p m e n t is open or enclosed, (b) whe ther the dus t is Group E, F, or G (c) whe ther the area is for storage 3-6.4 Step Four - De te rmin ing the Extent of the Classified Area:

The extent of the classified area may be de t e rmi ned by applying, with s o u n d eng inee r ing j u d g m e n t , the m e t h o d s d iscussed in 3-4 and the diagrams conta ined in dais chapter .

3-6.4.1 Locate the potential sources of leaks on the p lan drawing or at the actual location. These sources may include rotat ing or reciprocat ing shafts, doors a n d covers on process equ ipmen t , etc.

3-6.4.2 For each leakage source, find an equivalent example on the selected classification d iagram to de te rmine the m i n i m u m exten t of classification a r o u n d the leakage source. The ex ten t may be modif ied by cons ider ing the following: (a) An IGNITABLE MIXTURE is likely to occur f requent ly due to repair, ma in t enance or leakage.

(b) Where condi t ions of m a i n t e n a n c e and supervision are such tha t leaks are likely to occur in process equ ipmen t , s torage vessels and p ip ing systems con ta in ing combust ib le material.

(c) Ventilat ion or prevailing wind in the specific area and the dispersion rates of the combust ib le materials.

3-6.4.3 Once the m i n i m u m ex ten t is de te rmined , for practical reasons, utilize dist inct l andmarks (such as curbs, dikes, walls, s t ructural supports , edges of roads, etc.), for the actual boundar ies of the area classification. These l andmarks pe rmi t easy identification of the boundar ies of the hazardous areas for electricians, i n s t r u m e n t technicians, operators , and o ther personnel . SUBSTANTIATION: The EECA commi t tee spen t considerable t ime revising the p roposed 497-1997 to upda te the text explaining the use of the classification diagrams. The previous text m 497A was primarily a rei terat ion of text in previous chapters, ra ther than an explanat ion of the diagrams. T he proposed 497-1997 text in 3-7, now revolves a r o u n d the d iagrams and in addi t ion adds " c o m m o n sense" guidel ines based on experience. Unfor tunate ly , the similar text crea ted by the EECA ad hoc g roup was finalized after the mee t ing and did no t appear in the proposal . It would be very embarrass ing to have 497-1997 reflect the latest th ink ing of the EECA, but t hen leave the old, undesi rable text in 499-1997 simply because we ran out of time. If the p roposed 497-1997 text is accepted without negative comments , t hen it s tands to reason that the similar rewrite crea ted by the ad hoc g roup shou ld also be acceptable. In dais sense, it is an editorial change, i.e. the text accepted for 497-1997 was acceptable so it shou ld also be acceptable in 499-1997. COMMITTEE ACTION: Accept in Principle.

I In Section 3-6.2.2(e) of the text in the proposal, add a ques t ion mark at the end o f the second sentence .

In Section 3-6.2.5 of the text in the proposal, change "AIT" to "layer or c loud ignition tempera ture" to read as follows:

"3-6.2.5* Fire Hazard Propert ies of Combust ible Material. Th e NEC group and the layer or c loud igni t ion t empera tu re are shown in Table 2-5 for m a n y materials."

The r ema inde r of the section in the proposal is to remain the sallle. COMMITTEE STATEMENT: The first change is strictly editorial. The second change was made to more closely follow the Table in format ion and terminology. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 24 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 23 NOT RETURNED: 1 Woff

Editorial Correct ions

The Teclmical Commi t t ee on Electrical E q u i p m e n t in a Chemical A tmosphe re notes the following editorial correct ions to Proposal 497A-15 (Log #CP1).

1. In Section 1-3, change the defini t ions to the following: (under l ined text is editorially corrected text).

Group B - F lammable ~as. f l ammable liouid n r o d u c e d vapor, or combust ib le liquid p roduced vaoor, mi~;ed-with air tha t may burn or exnlode having ei ther a m a x i m u m exper imenta l safe gap (MESG) value less t han or equal to 0.45 m m or a m i n i m u m ignit ing cur ren t ratio (MIC ratio) less than or equal to 0.40.

Group C - Flar0mable gas, f l ammable l iuuid o r o d u c e d v a n o r , or combust ible liouid o roduced vanor m i x e d ' w i t h a i r tha t m a y burn or exolode having ei ther a m a x i m u m exper imenta l safe gap (MESG) value greater than 0.45 m m and less than or eaual_ to 0.75 ram, or a m i n i m u m igni t ing cur ren t ratio (MIC ratio) greater than 0.40 and less tllan or eaual to 0.80

Group D - F lammable gas. f l ammable l iauid o r o d u c e d vapor, or combust ib le l iauid o roduced vanor mixed-with-air tha t may burn or exolode having ei ther a m a x i m u m exper imenta l safe gap (MESG) value greater t han 0.75 m m or a m i n i m u m igniting cur rent ratio (MIC ratio) greater than 0.80.

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Documents

Nonvoting - NFPA · Zone 0, Class I, Zone 1, and Class I, Zone 2 from Section 505-7 in the 1996 NEC into Section 1-3 located after Class I, Division 2 definition to read as follows: