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है”ह”ह

IS 9570 (1980): Classification of flammable gases orvapours with air according to their maximum experimentalsafe gaps and minimum igniting currents [ETD 22: ElectricalApparatus for Explosive Atmosphere]

IS : 9570 - 1980 ( Reaffirmed 1996 )

Indian Standard

CLASSIFICATION OF FLAMMABLE GASES OR VAPOURS WITH AIR ACCORDING TO THEIR MAXIMUM EXPERIMENTAL SAFE GAPS AND

MINIMUM IGNITING CURRENTS

( First Reprint DECEMBER 1997 )

LJDC 621.31-213.34 : 614.87

0 Copyright 1980

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Gr 4 December 1980

IS : 9570 - 1980

hdian Standard CLASSIFICATION OF FLAMMABLE GASES

OR VAPOURS WITH AIR ACCORDING TO THEIR

MAXIMUM EXPERIMENTAL SAFE GAPS AND

MINIMUM IGNITING CURRENTS

Electrical Xpparatus for Explosive Atmospheres Sectional Committee, ETDC 22

Choirman DR G. S. B.IDAYI

Members

Representing Central Building Research Institute, Roorkee

SI~RI MAHESH CHANDRA (Alternute to Dr G. N. Badami)

S1IRI.J. H. BIIOJWANI Bharat Heavy Elcctricals Ltd, Hyderabad SHRI S. B. c. ibAR1VAL ($ltendP)

SIiRI s. C. GOELLA (Al&,&) SHRI S. K. BIS~VAS (GUPTA)

SIIRI 9. K. SEN (.~kentate) SHRI B. .\. C:IETTY SHRI S. G. DESHYUKII

SHRI P. N.~ASZ~TKAR (Alternate) DIRECTOR (COMMERCIAL)

Directorate General of Mines Safety, Dhanbad

Electronics Commission, New Delhi Bharat Bijlee Ltd, Bombay

Central Electricity Authority, Ministry of Energy (Department of Power)

DEPUTY DIRECTOR (Alternate) SHKI S. N. GHOSH

SHRI S. N. GHOSH SHRI D. P. GUPTA

SFIRI P. K. CIIAKRABORTY

SHRI S. KANUNGO (Alternate) SHRI PI. K. HALDER

SHRI K. B. GUGLANI (Alternate) DR HARIHAR SINGH

SHRI S.KRISHNAMURTIIY

The Association of Mining, Electrical & Mecha- nical Engineers, UK, Indian Sub-branch, Calcutta

Siemens India Ltd, Bombay Directorate General of Technical Development,

New Delhi Indian Oil Corporation Ltd (Refineries Division),

New Delhi

Indian Drugs and Pharmaceuticals Ltd, New Delhi

Directorate of Standardization, Ministry of Defence (DGI)

Food Corporation of India, New Delhi

(Continued on page 2)

Q Copyright 1980

BUREAU OF INDIAN STANDARDS

This publication is protected under the Indian Copyright Act (XIV of 1957) and reproduction in whole or in part by any means except with written permission of the nublisher shall be deemed to be an infringement of cooyrkht under the said Act.

Is : 9570 - 1980

(Continwdfrom jmge 1)

Members Representing

SHRI T. R. A. KR[SHNAN Tariff Advisory Committee, Bombay SHRI I. M. KHUSHU (Alternate)

SHRI P. V. S. KR~~HNAN The Fertilizer (Planning & Development) India Ltd, Sindri

SHRI SURE~H KUMAR (Alternate) SHRI T. S. KUMAR Central Mining Research Station (CSIR), Dhanbad

SHRI S. K. RAY (Alternate) SHRI H. N. GUPTA Directorate General Factory Advice Service and

Labour Institutes. Bombay SHRI G. VAWYANATHAN (Alternates

SHRI I. N. MURT~ Chief Controllerate of Explosives, Nagpur SHR~ CHARANJIT LAL (Alternate)

SHRI T. NITYANANDA S. DR M. S. PADBWRI

SHRI Y. D. DO~AJ (Alternate) SHRI M. A. J. PARTHASARATHY

mu T. R. GULATI (Alternate) S~nr S. G. RAMACHANDRA

Loss Prevention Association of India Ltd, Bombay Hindustan Brown Boveri Ltd, Bombay

Directorate of Standardization, Department of Defence Production, Ministry of Defence (Engineer-in-Chief)

Kiloskar Electric Co Ltd, Bangalore Sssm T. V. VIDYARATHNA RAJ (Alternate)

SHRI B. RAMACHANDRAN Larsen & Toubro Ltd, Bombay SW I. C. JOSEPH (Alternate)

SHRI K. K. RAY Macneill & Magor Ltd, Calcutta SHRI s. cHANDIu (Alternate)

SHRI. A. N. SIWATHSA NGEF Ltd. Bangalore SHRI S. L. SRJDELU~AMURTHY (Alternate)

SHRI M. B. TAWADEY Coal India Ltd, Ranchi SHIU A. S. R. MURTHY (Alternate)

SHRI G. N. THADANI ’ Engineers India Ltd, New Delhi Ssnu S. I<AsTNuRIRANCAN (Altcmate)

DR K. S. UPPAL Explosives Safety Group, Directorate of Armaments, Ministry of Defence (R&D)

SHRI R. SRINIVASAN (Alternate) SW S. P. SACHDEV, Director General, IS1 (Ex-ofiio Member)

Director (Elec tech)

Secretary

SHY R. K. MONGA Deputy Director (Elec tech), IS1

2

IS : 9570 - 1980

Indian Standard CLASSIFICATION OF FLAMMABLE GASES

OR VAPOURS WITH AIR ACCORDING TO THEIR MAXIMUM EXPERIMENTAL SAFE GAPS AND

MINIMUM IGNITING CURRENTS

0. FOREWORD

0.1 This Indian Standard was adopted by the Indian Standards Institution on 30 July 1980, after the draft finalized by the Electrical Apparatus for Explosive Atmospheres Sectional Committee had been approved by the Electrotechnical Division Council.

0.2 Electrical apparatus may have to be used in areas or enclosed spaces where, depending on local and operational conditions, gases, vapours OF

dusts forming an explosive mixture with air, are likely to occur in sufficient quantity to constitute a hazard. Th e precautions to be taken against explosion are prescribed by the appropriate authority responsible for safety. The authority may specify constructional requirements for the apparatus and make regulations for its installation and operation.

0.3 Flammable gases and vapours may cause a fire or explosion when the following three basic conditions are satisfied:

a) Presence of sufficient quantity of a flammable gas or vapour, b) Mixing of flammable gas or vapour with air or oxygen in the pro-

portions required to produce an explosive or ignitable mixture, and c) Occurrence of ignition.

0.4 An electric spark or arc may ignite the explosive mixture. However, a limiting value of minimum ignition energy (MIE) is required before the ignition can take place. t Since no apparatus has so far been specified for the determination of MIE, it cannot be accepted at present as a means of determining the grouping of explosive mixtures of gases and vapours in air.’

On the other hand, it has been possible to correlate the maximum safe gaps (in the case of flameproof apparatus) and minimum igniting currents (in the case of intrinsically safe circuits), and to group the flammable gases and vapours on the basis of maximum experimental safe gap (MESG) and minimum igniting current (MIC).

0.4.1 Small variations in test apparatus for determining MIC may result in appreciable variation in the value of MIC. Therefore, MIC is specified

3

IS : 9570 - 1980

as its ratio against the MIC of laboratory grade methane, and it has been referred to as MIC ratio in this standard.

0.5 For the purpose of flameproof enclosures and intrinsic safety, flammable gases and vapours have been classified into groups and subgroups on the basis of their LMESG and MIC ratio.

0.6 While classifying the gases and vapours, into groups and sub-groups, care has been taken that the resulting classification does not deviate more than is necessary from the currently accepted practices for flameproof en- closures (see IS: 2148-1968*) and intrinsic safety (see IS: 5780-1980$).

0.7 An attempt has been made to avoid, as far as possible, the necessity for determining values of both MESG and MIC before a gas or vapour can be allocated to a group or sub-group.

0.8 Besides the danger of explosion caused by an electric spark or arc, there is also a danger of ignition by hot surfaces exposed to a flammable atmosphere. According to their ignition temperatures, gases and vapours fall into fairly well-defined groups. A classification of the preferred limiting temperatures of the surface of electrical apparatus has been laid down in IS: 8239-1976:.

0.9 In the preparation of this standard, assistance has been derived from IEC Pub 79-12 (1978) ‘Electrical apparatus for explosive gas mixture, Part 12 - Classification of mixtures of gases or vapours in air according to their maximum experimental safe gaps and minimum igniting currents’, issued by the International Electrotechnical Commission (IEC).

1. SCOPE

1.1 This standard classifies the flammable gases and vapours into various groups and sub-groups on the basis of their maximum experimental safe gaps (MESG) and minimum igniting currents (MIC).

2. CLASSIFICATION OF GASES AND VAPOURS

2.1 For the purpose of flameproof enclosures and intrinsic safety, gases and vapours have been classified according to the groups or subgroups of appara- tus required for use in the particular gas or vapour atmosphere.

The general principles used to establish the lists of gases and vapours in the tables are given in 2.2, 2.3, 2.4, 3 and 4.

2.2 Classification According to the Maximum Experimental Safe Gaps (MESG)

*Specification for flameproof enclosures of electrical apparatus (first revision). -&wxification for intrinsically safe electrical apparatus and circuits. ~Classitkation of maximum surface temperatures of electrical equipment for use in explo-

sive atmospheres.

4

IS : 9570 - 1980

2.2.1 For flameproof enclosures, gases and vapours are classified according to their maximum experimental safe gaps (MESG). The standard method for determining MESG shall be the vessel described in Appendix C of IS : 1248-1968* but where determinations have been undertaken only in an 8-litre spherical vessel with ignition close to the flange gap; these can be accepted provisionally.

The groups of apparatus are: Group I : for mining applications (methane) ; Group II: for applications in other industries.

2.2.2 Group II apparatus is subdivided and, for the purpose of classifica- tion of gases and vapours, the MESG limits are :

Group IIA : MESG above or equal to O-9 mm; Group IIB : MESG greater than O-5 and less than 0.9 mm; Group IIC : MESG less’than or equal to O-5 mm.

NOTE - MESG is determined at, or corrected to, 20°C.

2.3 Classification According to the Mipimum Igniting Currents

WC)

2.3.1 For intrinsic safety, gases and vapours are classified according to the ratio of their minimum igniting currents with that of laboratory methane. The standard method of determining MIC ratio shall be with the apparatus described in IS : 9166-1979?, but where determinations have been under- :aken in other apparatus these can be accepted provisionally.

The groups of the apparatus are: Group I : for mining applications, (methane); Group II: applications in other industries.

2.3.2 Group II apparatus is subdivided as follows and, for the purpose of classification of gases and vapours, the MIC ratios are:

Group IIA : MIC ratio above 0.8; Group IIB : MIC ratio between 0.45 and 0.8; Group IIC : MIC ratio below 0.45.

2.4 Classification According to MESG and MIC

2.4.1 For most gases and vapours it is sufficient to make only one deter- mination of either MESG or MIC to classifjr the gas or vapow.

2.4.2 One determination is adequate when: Group IIA : the MESG exceeds O-9 mm; or the MIC ratio exceeds

Group IIB : Lz’ Ml%SG is between 0.55 and Q9 mm or the MIG ratio is between O-5 and 0.8;

*Specification for flameproof enclosures of electrical apparatus. tSpecification for spark test apparatus for intrinsically safe circuits.

5

IS : 9570 - 1980

Group IIC : the MESG is less than O-5 mm or the MIC ratio. less than O-45.

2.4.3 Determination of both the MESG and MIC ratio is required when :

a) The MIC ratio determination only has been made, and the ratio is between O-8 and 0.9; when an MESG determination will be required to classify the gas or vapour.

b) The MIC ratio determination only has been made? and the ratio is between 0.45 ‘and 0.5; when an MESG determination will be required to classify the gas or vapour.

c) The MESG only had been found, and is between 0.5 and 0.55 mm, when an MI? ratio determination will be required to classify the gag or vapour.

3. CLA!%IFICATION ACCORDING TO THE SIMILARITY OF CHEMICAL STRUCTUBE

3.1 When a gas or vapour is a member of the homologous series of com- pounds the classification of the gas or vapour can provisionally be infertid from the results of determinations of the other members of the series w’ith lower molecular masses. Care should be taken when such inferences are used in allocating the compound to a group.

4. CLASSIFICATION OF MIXTUBES OF GASES

4.1 Mixtures of gases should generally be allocated to a group only after a special deteymination of MESG or MICratio.

5. TABLES OF GASES AND VAPOURS

5.1 The classification in this standard provides guidance on the group of electrical apparatus to be used in a particular gas/air mixture to avoid the danger of an explosion from an electrical source. It should be noted that some materials listed, for example ethyl nitrate, are relatively un- stable and may be prone to spontaneous decomposition.

5.2 The list of gases and vapours in Tables 1,2 and 3 may not be considered to be comprehensive.

5.3 All isomeric forms of the cornpoundS listed are included.

5.4 The significance of the letter against each gas is as follows: a = classified according to MESG determination. b = classified according to MIC ratio. c = both MESG and MIC ratio have been determined. d = classified according to similarity of chemical structure (provisional

classification).

6

IS : 9570 - 1980

TABLE 1 CLASSIFTCATION OF FLAMMAB LE GASES OR ~VAPOURS FOR WHICH GROUP IIA APPARATUS IS REQUIRED

GASORVAPOUR

(1)

i) Hydrocarbons

Alkanes Methane* Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane Cyclobutane

Cyclopentane

Cyclohexane

Cycloheptane

Methylcyclobutane

Methylcyclopentane

Methylcyclohexane

Ethylcyclobutane

Ethylcyclopentane

Ethylcyclohexane

Decahydronaphthalene (dekalin)

(Clause 5)

CHEMICAL FORMULA

(2)

GH,~H(WI~HI

yH,(CH,),CH CH(CH,),CH, I

I I

Alkenes Propene (propylene) C,H, = CH,

*Methane (CH,) refers to a gas with negligible impurities.

METHOD OF CLASSIFICATION

(3)

a

C

d

d

d

d

d

d

d

d

a

(Continued)

7

IS : 9570 - 1980

TABLE 1 CLASSIFICATION OF FLAMMABLE GASES OR VAPOURS FOR WHICH GROUP IIA APPARATUS IS REQUIRED - Conk?

GASORVAPOUR

(1)

Aromatic Hydrocarbons Styrene Isopropcnylbenzene (methylstyrene)

Benzoids Benzene Toluene Xylene Ethylebenzene Trimethylbenzene Naphthalene Cumene Cymene

Mixed Hydrocarbons Methane (industrial)*

Turpentine Petroleum naphtha Coal tar naphtha Petroleum (including motor spirit) Solvent or cleaning petroleum Heating oil Kcrokne Diesel oil Motor benzole

ii) Compounds Contaiahg Oxygen Oxides (Including Ethers)

Carbon monoxidet Dipropyl ether

Alcohols and Phenols Methanol Ethanol Propanol Butanol Pentanol

CHEMICALFORMULA

(2)

C,H,CH = CH, C,H,C(CH,) = CH,

$&H, $ACJ*

(1 5 0 6 2HA(CHs)s

10 * CsHsCH(CH,), (CHACHC,H,CH,

co (GHI,),O

CH,OH C,H,OH C,H,OH C,H,OH C,HnOH

METHOD OF CLASSIFICATION

(3)

b a

a (calculated)

2

:

:

: a

C a

*‘Methane’ (CH,) refers to the gas with negligible impurities. ‘Methane (industrial)’ includes methane mixtures containing up to 15 percent by volume of hydrogen.

t‘Carbon monoxide’ may include a moisture content sufficient to saturate a carbon mono- xide-air mixture at normal ambient temperature.

(Continued)

8

Is: 9570-1980

TABLE 1 CLA!ZIFICATION OF FLAMMABLE GASES OR VAPOURS FOR WHICH GROUP ILA APPARATUS IS REQUIRFD - Contd

GAS OR VAPOUR

(1) Hexanol geg$

N&an01 Cyclohexanol

Methylcyclohexanols

Phenol CL-es01 4hydroxy-4-methylpentan-2-one

(diacetone alcohol)

Aldehydes Acetaldehyde Metaldehyde

Ketones Acetone Butanone (ethyl methyl ketone) Pentan-2-one (propyl methyl ketone) Hexan-Z-one (butyl methyl ketone) Amy1 methyl ketone Pentane-2, 4dione (acetylacetone) Cyclohexanone

ESlerS Methyl formate Ethyl formate Methyl acetate Ethyl acetate Propyl acetate Butyl acetate Amy1 acetate Methyl methacrylate Ethyl methacrylate Vinyl acetate Ethyl acetoacetate

Acids Acetic acid

CHEMICALFORMULA

CH,yH(CHs),yH OH

CsHsOH CHsC,H40H

(CH,),C(OH) CHsCO CHs

CHsCHO (CH,CHO)n

(C&)&O CzH,CO CH, C,H,CO CH, 2gBw& g3)

5 11 CHsCOCH, $0 CH, CH&Hs)&O

H COO CH, H COO CzHs CH,COO CH, CHXOO C,H< CH;COO C;H; CH,COO CIH, CH,COOC,HII , CHB = C(CH),COOCH, CHp = C(CH),COOC,H, CHsCOOCH = CH, CH,COCH&OOC,H,

CH,COOH

iii) Compounds Contaiaiag Halogens

Compounds without Oxygen Chloromethane CH,Cl Chloroethane CaH5Cl

METHODOF CLASSIFICATION

(3)

2 d

:

d

d d

d

b

9

Is : 9570 - 1980

TABLE 1 CLASSIFICATION OF FLAMMABLE GASES OR VAPOURS FOR WHICH GROUP IIA APPARATUS IS REQUIRED - Cbntd

GASORVAPOUR

(1)

Bromoethane Chloropropane Chlorobutane Bromobutane Dichloroethane Dichloropropane Chlorobenzene Benzyl chloride Dichlorobenzene Ally1 chloride Dichloroethylene Chloroethylene d, d, d,-Trifluorotoluene

(benzotrifluoride) Dichloromethane (methylene chloride)

CompOunn!s with Oxygen Acetyl chloride Chloroethanol

iv) Compounds Containing Sulphur Ethanethiol (ethyl mercaptan) Propane-1-thiol (propyl-mercaptan)

Thiophene

Tetrahydrothiophene

v) Compounds Containing Nitrogen Ammonia Acetonitrile Ethyl nitrite Nitromethane Nitroethane

Amines Methylamine Dimethylamine Trimethylamine Diethylamine Trietbylamine Propylamine Butylamine Cyclohexylamine

CHEMICAL FORM

(2)

CnH,Br C,H,CI C&H&l C,H,,Br C,H&l, C,H&l, C,H,Cl C,H,CH,Cl WWl, CH, = CHCH,Cl CHCl = CH Cl CH, = Cl3 Cl

C,H,CF, CH,Cl,

CH,COCl CH,CL CH,OH

C,H,SH C,H,SH

CH=CH=CHS I I CHZ(CH,),CH,S I

NH, CH,CN CH&H?ONO CH,NO, W-&NO,

CH,NH,

C,H,NH, C,H,NHz CH,(CH,),CH NH,

:LA METHOD OF CLASSIFICATION

(3)

d a

z

ti

ii!

t

a

C

C a

(calculated) a

a

a a

: d

(Cuntimud)

10

IS : 9570 - 1980

TABLE 1 CLASSIFICATION OF FLAMMABLE GASES OR VAPOURS FOR WHICH GROUP IIA APPARATUS IS REQUIRED - Cord

GASOR VAPOUR CHEMICAL FORMULA METHOD OP CLASSIPICL~TION

2-Aminoethanol (ethanolamine) (mono-ethanolamine)

Z-Diethylaminoethanol Diaminoethane Aniline NN-dimethylaniline Amphetamine Toluidine Pyridine

NH,CH,CH,OH (C,H,),NCH,CH,OH NH,CH,CH,NH, GH,NH, GH,N(CH,), C.H,CH.CHcNH.JCH.

(3)

Is : 9570 - 1980

TABLE 2 CLMWFICATION OF GASES OR VAPOURS FOR WHICH GROUP W APPARATUS IS REQUIRED

(cnuse 5)

GAS OR V-OUR

(1) i) Iiydroearbons

Propyne Ethylene Cyclopropane

1, 3-Butadiene

ii) Compounds Containing Nitrogen Acrylonitrile Isopropyl nitrate Hydrogen cyanide

iii) Compounds Containing *ygm Dimethyl ether Ethyl methyl ether Diethyl ether Dibutyl ether Oxione (ethylene oxide)

1, 2-Epoxypropane

1, 3-Dioxolane

1, 4-Dioxane

1, 3, 5-Trioxane

Butyl glycolate. (hydroxyacetic acid, butyl ester)

Tetrahydrofurfuryl alcohol

Methyl acrylate Ethyl acrylate Furan

Crotonaldehyde Acrylaldehyde (acrolein)

Tetrahydrofuran

iv) Mttpres Coke oven gas

v) Compmads Containing W0ge11s

Tetrafluoroethylene I-Chloro-2, 3-epoxypropane

(epichlorohydrin)

CHEMICALFORMULA

(2)

CH,C = CH

CH, = CH CH = CH,

CH, = CHCN (CH,),CHONO, HCN

(CH,),O CH,OC,H, (GH,),O (GH,),O

:HaCH80 -

CHaYHCHsP ~H,cH,ocH~~

~H,CH,OCH,CHI~

CH,OCH,OCH,O I I

HOCH,COOC,H, CH,CH,CHIOCH CH,OH

CH, = CHCOOCH, CH, = CHCOOC,HS yH=CHCH=CHy

CH&H = CHCHO CH, = CHCHO

~Hs(CH,), CHzy

(2,

OCHxCiHCHaC1 1

R~ETHODOF ~L.AWFICAl'lON

(3)

b

:

C

C b a

C d c C C

C

d

a

b

a d

a a a

a a

(calculated) a

d

a

a

12

IS : 9570 - 1980

TABLE 3 CLASSIFICATION OF FLAMMABLE GASES OR VAPOURS FOR WHICH GROUP IIC APPARATUS IS REQUIRED

GASORVAPOUR CHEMICAL FORMULA METHODOF

CLASSIFICATION

(1’) (2) (3)

Hydrogen HZ c Acetylene C*H, c Carbqn disulphide CS, c Ethyl nitrate C,H,ONO,

13

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