Explosive atmospheres - Part 20-1: Material characteristics for gas and vapour classification - Test methods and data

ISO/IEC 80079-20-1: 2017 is published as a dual log standard and provides guidance on classification of gases and vapours. It describes a test method intended for the measurement of the maximum experimental safe gaps (MESG) for gas-air mixtures or vapour-air mixtures under normal conditions of temperature and pressure (20 °C, 101,3 kPa) so as to permit the selection of an appropriate group of equipment. This document also describes a test method intended for use in the determination of the auto-ignition temperature (AIT) of a vapour-air mixture or gas-air mixture at atmospheric pressure, so as to permit the selection of an appropriate temperature class of equipment. Values of chemical properties of materials are provided to assist in the selection of equipment to be used in hazardous areas. Further data may be added as the results of validated tests become available. The materials and the characteristics included in a table (see Annex B) have been selected with particular reference to the use of equipment in hazardous areas. The data in this document have been taken from a number of references which are given in the bibliography. These methods for determining the MESG or the AIT may also be used for gas-air-inert mixtures or vapour-air-inert mixtures. However, data on air-inert mixtures are not tabulated.
Keywords: classification of gases and vapours, measurement of the maximum experimental safe gaps (MESG)
The contents of the corrigendum of July 2018 have been included in this copy.

Atmosphères explosives - Partie 20-1: Caractéristiques des produits pour le classement des gaz et des vapeurs - Méthodes et données d'essai

ISO/IEC 80079-20-1:2017 est publiée en tant que norme sous double logo et donne des recommandations pour le classement des gaz et des vapeurs. Elle décrit une méthode d'essai destinée à mesurer les interstices expérimentaux maximaux de sécurité (IEMS ou MESG – maximum experimental safe gaps) des mélanges gaz-air ou vapeur-air dans des conditions normales de température et de pression (20 °C, 101,3 kPa) afin de pouvoir choisir un groupe approprié d'appareils. Le présent document décrit également une méthode d'essai qui permet d'établir la température d’auto-inflammation (TAI ou AIT – auto-ignition temperature) d'un mélange vapeur-air ou gaz-air à la pression atmosphérique, afin de pouvoir choisir une classe de température appropriée des appareils. Les valeurs des propriétés chimiques des produits sont fournies pour faciliter le choix des appareils à utiliser dans les emplacements dangereux. Des données supplémentaires peuvent être ajoutées au fur et à mesure de l’obtention de résultats d’essai validés. Les produits et les caractéristiques indiqués dans un tableau (voir l’Annexe B) ont été choisis tout particulièrement pour l'utilisation d'appareils dans des emplacements dangereux. Les données fournies dans le présent document sont extraites d’un certain nombre de documents de référence qui sont cités dans la bibliographie. Ces méthodes de détermination de l’IEMS ou d’établissement de la TAI peuvent être également appliquées pour les mélanges gaz-air-matière inerte ou les mélanges vapeur-air-matière inerte. Les données relatives aux mélanges air-matière inerte ne sont toutefois pas fournies.
Mots clés: classement des gaz et des vapeurs, mesurer les interstices expérimentaux maximaux de sécurité (IEMS ou MESG)
Le contenu du corrigendum de juillet 2018 a été pris en considération dans cet exemplaire.

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Publication Date
13-Dec-2017
Current Stage
PPUB - Publication issued
Completion Date
14-Dec-2017
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ISO/IEC 80079-20-1
Edition 1.0 2017-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 20-1: Material characteristics for gas and vapour classification – Test
methods and data
Atmosphères explosives –
Partie 20-1: Caractéristiques des produits pour le classement des gaz et des
vapeurs – Méthodes et données d'essai
ISO/IEC 80079-20-1:2017-12(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
ISO/IEC 80079-20-1
Edition 1.0 2017-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 20-1: Material characteristics for gas and vapour classification – Test
methods and data
Atmosphères explosives –
Partie 20-1: Caractéristiques des produits pour le classement des gaz et des
vapeurs – Méthodes et données d'essai
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.230; 29.260.20 ISBN 978-2-8322-5164-5

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

---------------------- Page: 3 ----------------------
− 2 − ISO/IEC 80079-20-1:2017 © ISO/IEC 2017
CONTENTS

FOREWORD ........................................................................................................................... 5

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 7

4 Classification of gases and vapours ................................................................................. 9

4.1 General ................................................................................................................... 9

4.2 Classification according to the maximum experimental safe gap (MESG) ................ 9

4.3 Classification according to the minimum igniting current ratio (MIC ratio) .............. 10

4.4 Classification according to the similarity of chemical structure .............................. 10

4.5 Classification of mixtures of gases ........................................................................ 10

5 Data for flammable gases and vapours, relating to the use of equipment ....................... 11

5.1 Determination of the properties ............................................................................. 11

5.1.1 General ......................................................................................................... 11

5.1.2 Equipment group ........................................................................................... 11

5.1.3 Flammable limits ............................................................................................ 11

5.1.4 Flash point (FP) ............................................................................................. 11

5.1.5 Temperature class ......................................................................................... 12

5.1.6 Minimum igniting current (MIC) ...................................................................... 12

5.1.7 Auto-ignition temperature (AIT) ...................................................................... 12

5.2 Properties of particular gases and vapours ........................................................... 12

5.2.1 Coke oven gas ............................................................................................... 12

5.2.2 Ethyl nitrite .................................................................................................... 12

5.2.3 MESG of carbon monoxide ............................................................................ 12

5.2.4 Methane, Equipment Group IIA ...................................................................... 13

6 Method of test for the maximum experimental safe gap (MESG) .................................... 13

6.1 Outline of method ................................................................................................. 13

6.2 Test apparatus ...................................................................................................... 13

6.2.1 General ......................................................................................................... 13

6.2.2 Material and mechanical strength .................................................................. 14

6.2.3 Exterior chamber ........................................................................................... 14

6.2.4 Interior chamber ............................................................................................ 14

6.2.5 Gap adjustment ............................................................................................. 14

6.2.6 Injection of mixture ........................................................................................ 14

6.2.7 Position of ignition source .............................................................................. 14

6.3 Procedure ............................................................................................................. 14

6.3.1 Preparation of gas mixtures ........................................................................... 14

6.3.2 Temperature and pressure ............................................................................. 14

6.3.3 Gap adjustment ............................................................................................. 15

6.3.4 Ignition .......................................................................................................... 15

6.3.5 Observation of the ignition process ................................................................ 15

6.4 Determination of maximum experimental safe gap (MESG) ................................... 15

6.4.1 General ......................................................................................................... 15

6.4.2 Preliminary tests ............................................................................................ 15

6.4.3 Confirmatory tests ......................................................................................... 15

6.4.4 Reproducibility of maximum experimental safe gaps (MESG) ......................... 15

6.4.5 Tabulated values ........................................................................................... 16

---------------------- Page: 4 ----------------------
ISO/IEC 80079-20-1:2017 © ISO/IEC 2017 − 3 −

6.5 Verification of the MESG determination method .................................................... 16

7 Method of test for auto-ignition temperature (AIT) .......................................................... 16

7.1 Outline of method ................................................................................................. 16

7.2 Apparatus ............................................................................................................. 16

7.2.1 General ......................................................................................................... 16

7.2.2 Test vessel and support ................................................................................. 17

7.2.3 Thermocouples .............................................................................................. 17

7.2.4 Oven ............................................................................................................. 17

7.2.5 Metering devices ........................................................................................... 18

7.2.6 Mirror ............................................................................................................ 18

7.2.7 Timer ............................................................................................................. 18

7.2.8 Equipment for purging the test vessel with air ................................................ 18

7.2.9 Automated apparatus ..................................................................................... 18

7.3 Sampling, preparation and preservation of test samples ....................................... 19

7.3.1 Sampling ....................................................................................................... 19

7.3.2 Preparation and preservation ......................................................................... 19

7.4 Procedure ............................................................................................................. 19

7.4.1 General ......................................................................................................... 19

7.4.2 Sample injection ............................................................................................ 20

7.4.3 Determination of the auto-ignition temperature (AIT) ...................................... 20

7.5 Auto-ignition temperature (AIT) ............................................................................. 21

7.6 Validity of results .................................................................................................. 21

7.6.1 Repeatability ................................................................................................. 21

7.6.2 Reproducibility ............................................................................................... 21

7.7 Data ...................................................................................................................... 22

7.8 Verification of the auto-ignition temperature determination method ....................... 22

Annex A (normative) Ovens of test apparatus for the tests of auto-ignition temperature ....... 23

A.1 General ................................................................................................................. 23

A.2 “IEC oven” ............................................................................................................ 23

A.3 “DIN oven” ............................................................................................................ 23

Annex B (informative) Tabulated values ............................................................................... 30

Annex C (informative) Determination of cool flames ............................................................. 84

Annex D (informative) Volume dependence of auto-ignition temperature .............................. 86

Bibliography .......................................................................................................................... 87

Figure 1 − Test apparatus ..................................................................................................... 13

Figure A.1 − Test apparatus: assembly ................................................................................. 24

Figure A.2 − Section A-A (flask omitted) ............................................................................... 25

Figure A.3 − Base heater (board made of refractory material) ............................................... 25

Figure A.4 − Flask guide ring (board made of refractory material) ......................................... 26

Figure A.5 − Neck heater (board made of refractory material) ............................................... 26

Figure A.6 − Oven ................................................................................................................. 27

Figure A.7 − Lid of steel cylinder ........................................................................................... 28

Figure A.8 − Lid of steel cylinder ........................................................................................... 29

Figure A.9 − Injection of gaseous sample.............................................................................. 29

Figure C.1 − Additional thermocouple to detect cool flames .................................................. 84

---------------------- Page: 5 ----------------------
− 4 − ISO/IEC 80079-20-1:2017 © ISO/IEC 2017

Figure C.2 − ‘Negative temperature coefficient’ shown for butyl butyrate as an example ....... 85

Figure D.1 − Volume dependence of auto-ignition temperature ............................................. 86

Table 1 − Classification of temperature class and range of auto-ignition temperatures ......... 12

Table 2 − Values for verification of the apparatus ................................................................. 16

Table 3 − Values for verification of the apparatus ................................................................. 22

Table B.1 − Material data ...................................................................................................... 32

---------------------- Page: 6 ----------------------
ISO/IEC 80079-20-1:2017 © ISO/IEC 2017 − 5 −
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 20-1: Material characteristics for gas and vapour classification –
Test methods and data
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard ISO/IEC 80079-20-1 has been prepared by subcommittee 31M: Non-

electrical equipment and protective systems for explosive atmospheres, of IEC technical

committee 31: Equipment for explosive atmospheres.

This first edition of ISO/IEC 80079-20-1 cancels and replaces IEC 60079-20-1:2010. It

constitutes a technical revision. This edition includes the following significant technical changes with

respect to the previous edition:

The classifications for the temperature class or equipment group were changed in the informative

Annex B for the following materials: CAS-No. 64-17-5; 78-93-3; 107-31-3:

 For dry Ethanol (CAS-No. 64-17-5), equipment group remains IIB, but for Ethanol in air with

≥4% water vapour, as in common atmospheres, a second line has been added to indicate IIA;

---------------------- Page: 7 ----------------------
− 6 − ISO/IEC 80079-20-1:2017 © ISO/IEC 2017

 For 2-Butanone (CAS-No. 78-93-3), re-measurement indicated change from IIB to IIA was

needed; and

 For Formic Acid Methyl Ester (CAS-No. 107-31-3), re-measurement indicated change from T2

to T1 was justified.

No significant changes were made with respect to the normative text of IEC 60079-20-1:2010.

It is published as a double logo standard.
The text of this standard is based on the following documents:
FDIS Report on voting
31M/122/FDIS 31M/126/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60079 series, under the general title: Explosive atmospheres, as

well as the International Standard 80079 series, can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
 reconfirmed,
 withdrawn,
 replaced by a revised edition, or
 amended.
The contents of the corrigendum of July 2018 have been included in this copy.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 8 ----------------------
ISO/IEC 80079-20-1:2017 © ISO/IEC 2017 − 7 −
EXPLOSIVE ATMOSPHERES –
Part 20-1: Material characteristics for gas and vapour classification –
Test methods and data
1 Scope

This part of ISO/IEC 80079 provides guidance on classification of gases and vapours. It

describes a test method intended for the measurement of the maximum experimental safe

gaps (MESG) for gas-air mixtures or vapour-air mixtures under normal conditions of

temperature and pressure (20 °C, 101,3 kPa) so as to permit the selection of an appropriate

group of equipment. This document also describes a test method intended for use in the

determination of the auto-ignition temperature (AIT) of a vapour-air mixture or gas-air mixture

at atmospheric pressure, so as to permit the selection of an appropriate temperature class of

equipment.

Values of chemical properties of materials are provided to assist in the selection of equipment

to be used in hazardous areas. Further data may be added as the results of validated tests

become available.

The materials and the characteristics included in a table (see Annex B) have been selected

with particular reference to the use of equipment in hazardous areas. The data in this

document have been taken from a number of references which are given in the bibliography.

These methods for determining the MESG or the AIT may also be used for gas-air-inert

mixtures or vapour-air-inert mixtures. However, data on air-inert mixtures are not tabulated.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.

IEC 60050-426, International Electrotechnical Vocabulary − Part 426: Electrical apparatus for

explosive atmospheres (available at http://www.electropedia.org/)

IEC 60079-11, Explosive atmospheres − Part 11: Equipment protection by intrinsic safety "i"

IEC 60079-14, Explosive atmospheres − Part 14: Electrical installations design, selection and

erection
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-426 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
 IEC Electropedia: available at http://www.electropedia.org/
 ISO Online browsing platform: available at http://www.iso.org/obp
---------------------- Page: 9 ----------------------
− 8 − ISO/IEC 80079-20-1:2017 © ISO/IEC 2017
3.1
auto-ignition

reaction which is evidenced by a clearly perceptible flame and/or explosion, and for which the

ignition delay time does not exceed 5 min
Note 1 to entry: See 7.2.2 for a test method.
3.2
ignition delay time
time between the completed injection of the flammable material and the ignition
3.3
auto-ignition temperature
AIT

lowest temperature (of a surface) at which under specified test conditions an ignition of a

flammable gas or vapour in mixture with air or air-inert gas occurs
Note 1 to entry: See Clause 7 for a test method.
3.4
maximum experimental safe gap
MESG

maximum gap of a joint of 25 mm in width which prevents any transmission of an explosion

during tests made under the conditions specified in this document
Note 1 to entry: See Clause 6 for a test method.
3.5
minimum igniting current
MIC

minimum current in a specified test circuit that causes the ignition of the explosive test

mixture in the spark test apparatus according to IEC 60079-11
Note 1 to entry: See 5.1.6 for the test circuit.
3.6
flammable limits

lower flammable limit (LFL) and upper flammable limit (UFL) of gas in a gas-air mixture,

between which a flammable mixture is formed

Note 1 to entry: The term “explosive limits” is used especially in European standardization and regulations

interchangeably to describe these limits.

Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.

3.6.1
lower flammable limit
LFL

concentration of flammable gas or vapour in air, below which an explosive gas atmosphere

does not form

Note 1 to entry: For the purposes of Ex Equipment, this was previously referred to as the lower explosive limit

(LEL).

Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.

3.6.2
upper flammable limit
UFL

concentration of flammable gas or vapour in air, above which an explosive gas atmosphere

does not form
---------------------- Page: 10 ----------------------
ISO/IEC 80079-20-1:2017 © ISO/IEC 2017 − 9 −

Note 1 to entry: For the purposes of Ex Equipment, this was previously referred to as the upper explosive limit

(UEL).

Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.

3.7
equipment grouping

classification system of equipment related to the explosive atmosphere for which they are

intended to be used
Note 1 to entry: IEC 60079-0 identifies three equipment groups:
Group I − equipment for mines susceptible to fire damp;

Group II, which is sub-divided into groups IIA, IIB and IIC − equipment for all places with an explosive gas

atmosphere other than mines susceptible to fire damp;
Group III, whic
...

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