Explosive atmospheres - Part 20-1: Material characteristics for gas and vapour classification - Test methods and data (ISO/IEC 80079-20-1:2017)

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, 100 kPa) so as to permit the selection of an appropriate group of equipment. The standard describes also 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 standard 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.

Explosionsfähige Atmosphären - Stoffliche Eigenschaften zur Klassifizierung von Gasen und Dämpfen - Teil 20-1: Prüfverfahren und Daten (ISO/IEC 80079-20-1:2017)

Dieser Teil von ISO/IEC 80079 dient als Hilfestellung bei der Klassifizierung von Gasen und Dämpfen. Er beschreibt ein Prüfverfahren zur Messung der Normspaltweite (NSW) für Gas  oder Dampf-Luft-Gemische unter Laborbedingungen von Temperatur und Druck (20° C; 101,3 kPa) und ermöglicht somit die Einteilung in die zutreffende Explosionsgruppe. Dieses Dokument beschreibt auch ein Prüfverfahren zur Bestimmung der Zündtemperatur (Tz) eines Dampf-Luft-Gemisches oder Gas-Luft-Gemisches bei Atmosphärendruck, um so Geräte der geeigneten Temperaturklasse auszuwählen.
Daten physikochemischer Eigenschaften von Stoffen werden bereitgestellt als Hilfestellung für die Auswahl der in explosionsgefährdeten Bereichen einzusetzenden Geräte. Weitere Daten, die durch validierte Prüfungen erhalten wurden, dürfen künftig hinzugefügt werden.
Die Stoffe und die in einer Tabelle (siehe Anhang B) aufgeführten Eigenschaften wurden vor allem im Hinblick auf den Einsatz von Geräten in explosionsgefährdeten Bereichen ausgewählt. Die Daten in diesem Dokument wurden verschiedener Quellen entnommen, die in den Literaturhinweisen aufgeführt sind.
Die Verfahren zur Bestimmung der NSW oder der Tz dürfen auch für Gas-Luft-Inertgas-Gemische oder Dampf-Luft-Inertgas-Gemische eingesetzt werden. Daten über Luft-Inertgas-Gemische sind jedoch nicht in der Tabelle aufgeführt

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)

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)

Eksplozivne atmosfere - 20-1. del: Lastnosti materiala in razvrstitev za pline in hlape - Preskusne metode in podatki (ISO/IEC 80079-20-1:2017)

Ta del standarda ISO/IEC 80079 podaja smernice glede razvrstitve plinov in hlapov. Opisuje preskusno metodo, namenjeno merjenju največjih poskusnih varnih vrzeli (MESG) za zmesi plinov in zraka ali zmesi hlapov in zraka v normalnih pogojih temperature in tlaka (20 °C, 100 kPa), da se omogoči izbira ustrezne skupine opreme. Standard opisuje tudi preskusno metodo, ki se uporablja za določanje temperature samovžiga (AIT) zmesi hlapov in zraka ali plinov in zraka pri atmosferskem tlaku, da se omogoči izbira ustreznega temperaturnega razreda opreme. Navedene so vrednosti kemijskih lastnosti materialov, ki so namenjene kot pomoč pri izbiri opreme za uporabo v nevarnih območjih. Ko bodo na voljo rezultati potrjenih testov, se lahko dodajo dodatni podatki.  Materiali in značilnosti, vključene v tabelo (glej dodatek B), so bile izbrane s posebnim poudarkom na uporabi opreme v nevarnih območjih. Podatki v tem standardu so vzeti iz številnih referenc, ki so podane v bibliografiji. Te metode za določanje MESG ali AIT se lahko uporabljajo tudi za zmesi plinov, zraka in inertnih plinov ali zmesi hlapov, zraka in inertnih plinov. Vendar podatki o zmeseh zraka in inertnih plinov niso tabelirani.

General Information

Status
Published
Public Enquiry End Date
28-Feb-2016
Publication Date
12-Jan-2020
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
04-Nov-2019
Due Date
09-Jan-2020
Completion Date
13-Jan-2020

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SLOVENSKI STANDARD
SIST EN ISO/IEC 80079-20-1:2020
01-februar-2020

Eksplozivne atmosfere - 20-1. del: Lastnosti materiala in razvrstitev za pline in

hlape - Preskusne metode in podatki (ISO/IEC 80079-20-1:2017)
Explosive atmospheres - Part 20-1: Material characteristics for gas and vapour
classification - Test methods and data (ISO/IEC 80079-20-1:2017)

Explosionsfähige Atmosphären - Stoffliche Eigenschaften zur Klassifizierung von Gasen

und Dämpfen - Teil 20-1: Prüfverfahren und Daten (ISO/IEC 80079-20-1:2017)

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)
Ta slovenski standard je istoveten z: EN ISO/IEC 80079-20-1:2019
ICS:
29.260.20 Električni aparati za Electrical apparatus for
eksplozivna ozračja explosive atmospheres
SIST EN ISO/IEC 80079-20-1:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO/IEC 80079-20-1:2020
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SIST EN ISO/IEC 80079-20-1:2020
EN ISO/IEC 80079-20-1
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2019
EUROPÄISCHE NORM
ICS 29.260.20 Supersedes EN 60079-20-1:2010
English Version
Explosive atmospheres - Part 20-1: Material
characteristics for gas and vapour classification - Test
methods and data (ISO/IEC 80079-20-1:2017, including
Cor 1:2018)

Atmosphères explosives - Partie 20-1 : Caractéristiques Explosionsfähige Atmosphären - Stoffliche

des produits pour le classement des gaz et des vapeurs Eigenschaften zur Klassifizierung von Gasen und

- Méthodes et données d'essai (ISO/CEI 80079-20- Dämpfen - Teil 20-1: Prüfverfahren und Daten

1:2017, y compris Cor 1:2018) (ISO/IEC 80079-20-1:2017, einschließlich Cor 1:2018)

This European Standard was approved by CEN on 8 January 2018.

This European Standard was corrected and reissued by the CEN-CENELEC Management Centre on 20 November 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATIO N
EUROPÄISCHES KOMITEE FÜR NORMUN G
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO/IEC 80079-20-1:2019 E

worldwide for CEN national Members.
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SIST EN ISO/IEC 80079-20-1:2020
EN ISO/IEC 80079-20-1:2019 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

Annex ZA (informative) Relationship between this European Standard and the essential

requirements of Directive 2014/34/EU aimed to be covered ........................................................ 4

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SIST EN ISO/IEC 80079-20-1:2020
EN ISO/IEC 80079-20-1:2019 (E)
European foreword

This document (EN ISO/IEC 80079-20-1:2019) has been prepared by Technical Committee ISO/TMB

"Technical Management Board - groups" in collaboration with Technical Committee CEN/TC 305

“Potentially explosive atmospheres - Explosion prevention and protection” the secretariat of which is

held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by April 2020, and conflicting national standards shall be

withdrawn at the latest by April 2022.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

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

This document supersedes EN 60079-20-1:2010.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association, and supports essential requirements of EU Directive(s).

For the relationship with EU Directive(s) see informative Annex ZA, which is an integral part of this

document.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO/IEC 80079-20-1:2017, including Cor 1:2018 has been approved by CEN as

EN ISO/IEC 80079-20-1:2019 without any modification.
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SIST EN ISO/IEC 80079-20-1:2020
EN ISO/IEC 80079-20-1:2019 (E)
Annex ZA
(informative)
Relationship between this European Standard and the essential
requirements of Directive 2014/34/EU aimed to be covered

This European Standard has been prepared under a Commission’s standardization request

M/BC/CEN/92/46 to provide one voluntary means of conforming to essential requirements of Directive

2014/34/EU “Directive 2014/34/EU Of The European Parliament And Of The Council of 26 February

2014 on the harmonisation of the laws of the Member States relating to equipment and protective

systems intended for use in potentially explosive atmospheres (recast)”.

Once this standard is cited in the Official Journal of the European Union under that Directive,

compliance with the normative clauses of this standard given in Table ZA.1 confers, within the limits of

the scope of this standard, a presumption of conformity with the corresponding essential requirements

of that Directive, and associated EFTA regulations.

Table ZA.1 — Correspondence between this European Standard and Directive 2014/34/EU

Essential Requirements of Clause(s)/sub-clause(s) of Remarks/Notes
Directive 2014/34/EU this EN
1.0.1 All clauses

WARNING 1 — Presumption of conformity stays valid only as long as a reference to this European

Standard is maintained in the list published in the Official Journal of the European Union. Users of this

standard should consult frequently the latest list published in the Official Journal of the European

Union.

WARNING 2 — Other Union legislation may be applicable to the product(s) falling within the scope of

this standard.
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SIST EN ISO/IEC 80079-20-1:2020
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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SIST EN ISO/IEC 80079-20-1:2020
− 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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SIST EN ISO/IEC 80079-20-1:2020
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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SIST EN ISO/IEC 80079-20-1:2020
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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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SIST EN ISO/IEC 80079-20-1:2020
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

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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SIST EN ISO/IEC 80079-20-1:2020
− 6 − ISO/IEC 80079-20-1:2017 © ISO/IEC 2017
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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SIST EN ISO/IEC 80079-20-1:2020
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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SIST EN ISO/IEC 80079-20-1:2020
− 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 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 vol
...

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