ISO/IEC 80079-20-1:2017

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)

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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













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.

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− 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

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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

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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

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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
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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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
Publications.
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. No significant changes were made with respect to
IEC 60079-20-1:2010.
It is published as a double logo standard.

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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.

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.

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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

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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 ignition 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

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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, which is sub-divided into groups IIIA, IIIB and IIIC − equipment for all places with an explosive dust
atmosphere other than mines susceptible to fire damp.
3.8
flash point
FP
lowest liquid temperature at which, under specified test conditions, a liquid gives off vapours
in quantity such as to be capable of forming an ignitable vapour-air mixture
3.9
gas
gaseous phase of a substance that cannot reach equilibrium with its liquid or solid state in the
temperature and pressure range of interest
Note 1 to entry: This is a simplification of the scientific definition, and merely requires that the substance is above
its boiling point or sublimation point at the ambient temperature and pressure.
3.10
vapour
gaseous phase of a substance that can reach equilibrium wi
...