IEC 60079-18:2014

Explosive atmospheres - Part 18: Equipment protection by encapsulation "m"

IEC 60079-18:2014 gives the specific requirements for the construction, testing and marking of electrical equipment, parts of electrical equipment and Ex components with the type of protection encapsulation "m" intended for use in explosive gas atmospheres or explosive dust atmospheres. This part applies only for encapsulated electrical equipment, encapsulated parts of electrical equipment and encapsulat ed Ex components (hereinafter always referred to as "m" equipment) where the rated voltage does not exceed 11 kV. The application of electrical equipment in atmospheres, which may contain explosive gas as well as combustible dust simultaneously, may require additional protective measures. This standard does not apply to dusts of explosives, which do not require atmospheric oxygen for combustion, or to pyrophoric substances. This standard does not take account of any risk due to an emission of flammable or toxic gas from the dust. This standard supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard takes precedence. This fourth edition cancels and replaces the third edition of IEC 60079-18:2009, and constitutes a technical revision. Please refer to the foreword of the document for a listing of the technical changes with respect to the previous edition. Keywords: encapsulation "m", explosive gas atmospheres, explosive dust atmospheres
This publication is to be read in conjunction with IEC 60079-0:2011.
The contents of the corrigendum of July 2018 have been included in this copy.

Atmosphères explosives - Partie 18: Protection du matériel par encapsulage "m"

IEC 60079-18:2014 définit les exigences spécifiques à la construction, aux essais et au marquage des matériels électriques, des parties de matériels électriques et des composants Ex protégés par encapsulage de type "m" et destinés à une utilisation dans les atmosphères explosives gazeuses ou les atmosphères explosives poussiéreuses. La présente partie ne s'applique qu'aux matériels électriques protégés par encapsulage, aux parties de matériel électrique protégées par encapsulage et aux composants Ex protégés par encapsulage (ci-après toujours dénommés matériel "m") pour lesquels la tension assignée n'excède pas 11 kV. L'utilisation du matériel électrique en atmosphère pouvant contenir simultanément du gaz explosif et des poussières combustibles peut nécessiter des mesures de protection supplémentaires. La présente Norme ne s'applique pas aux poussières d'explosifs qui n'exigent pas d'oxygène de l'air pour leur combustion ni aux substances pyrophoriques. La présente Norme ne tient pas compte des risques, quels qu'ils soient, résultant d'une émission de gaz inflammable ou toxique provenant de la poussière. La présente Norme complète et modifie les exigences générales de l'IEC 60079-0. Si une exigence de la présente Norme est en conflit avec une exigence de l'IEC 60079-0, l'exigence de la présente Norme a préséance. Cette quatrième édition annule et remplace la troisième édition de l'IEC 60079-18:2009. Cette édition constitue une révision technique. Se référer à l'avant-propos du document pour obtenir une liste des modifications techniques par rapport à l'édition précédente. Mots clés: encapsulage de type "m", atmosphères explosives gazeuses, atmosphères explosives poussiéreuses
Cette publication doit être lue conjointement avec la CEI 60079-0:2011.
Le contenu du corrigendum de juillet 2018 a été pris en considération dans cet exemplaire.

General Information

• Status: Published
• Publication Date: 11-Dec-2014
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: TC 31 - Equipment for explosive atmospheres
• Drafting Committee: MT 60079-18 - TC 31/MT 60079-18
• Current Stage: PPUB - Publication issued
• Start Date: 15-Jan-2015
• Completion Date: 12-Dec-2014

Relations

• Amended By: IEC 60079-18:2014/AMD1:2017 - Amendment 1 - Explosive atmospheres - Part 18: Equipment protection by encapsulation "m"
• Effective Date: 05-Sep-2023
• Corrected By: IEC 60079-18:2014/COR1:2018 - Corrigendum 1 - Explosive atmospheres - Part 18: Equipment protection by encapsulation "m"
• Effective Date: 05-Sep-2023
• Revises: IEC 60079-18:2009/COR1:2009 - Corrigendum 1 - Explosive atmospheres - Part 18: Equipment protection by encapsulation "m"
• Effective Date: 05-Sep-2023
• Revises: IEC 60079-18:2009 - Explosive atmospheres - Part 18: Equipment protection by encapsulation "m"
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60079-18 ®
Edition 4.0 2014-12
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 18: Equipment protection by encapsulation “m”

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

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IEC 60079-18 ®
Edition 4.0 2014-12
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 18: Equipment protection by encapsulation “m”

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-2078-8

– 2 – IEC 60079-18:2014 RLV  IEC 2014

CONTENTS
FOREWORD . 5
1  Scope . 8
2  Normative references. 8
3  Terms and definitions . 9
4  General . 11
4.1  Level of protection (equipment protection level (EPL)) . 11
4.2  Additional requirements for levels of protection “ma” and “mb” . 11
4.3  Additional requirements for level of protection “ma” . 11
4.4  Rated voltage and prospective short circuit current . 11
5  Requirements for compounds . 11
5.1  General . 11
5.2  Specification . 12
5.3  Properties of the compound . 12
5.3.1  Water absorption . 12
5.3.2  Dielectric strength . 12
6  Temperatures . 12
6.1  General . 12
6.2  Determination of the limiting temperatures . 13
6.2.1  Maximum surface temperature . 13
6.2.2  Temperature of the compound . 13
6.3  Temperature limitation . 13
7  Constructional requirements . 13
7.1  General . 13
7.2  Determination of faults . 14
7.2.1  Fault examination . 14
7.2.2  Components considered as not subject to fail . 14
7.2.3  Isolating components . 15
7.2.4  Infallible separation distances . 15
7.3  Free space in the encapsulation . 17
7.3.1  Group III “m” equipment . 17
7.3.2  Group I and Group II “m” equipment . 17
7.4  Thickness of the compound . 18
7.4.1  “m” equipment . 18
7.4.2  Windings for electrical machines . 20
7.4.3  Rigid, multi-layer printed wiring boards with through connections . 20
7.5  Switching contacts . 22
7.5.1  General . 22
7.5.2  Level of protection “ma” . 22
7.5.3  Level of protection “mb” . 23
7.5.4  Level of protection “mc” . 23
7.6  External connections . 23
7.6.1  General . 23
7.6.2  Additional requirements for “ma” equipment . 23
7.7  Protection of bare live pa rt s . 23

7.8  Cells and batteries . 24
7.8.1  General . 24
7.8.2  Prevention of gassing . 24
7.8.3  Protection against inadmissible temperatures and damage to the cells
or batteries . 24
7.8.4.  Reverse current . 25
7.8.5  Current limitation . 25
7.8.6  Protection against the polarity inversion and deep discharge of the cells . 25
7.8.7  Charging of cells or batteries . 26
7.8.8  Requirements for control safety devices for cells or batteries . 26
7.9  Protective devices . 26
7.9.1  General . 26
7.9.2  Electrical protective devices . 27
7.9.3  Thermal protec tiv e devices . 28
7.9.4  Built-in protective devices . 28
8  Type tests . 29
8.1  Tests on the compound . 29
8.1.1  Water absorption test . 29
8.1.2  Dielectric strength test . 29
8.2  Tests on the apparatus . 29
8.2.1  Test sequence . 29
8.2.2  Maximum t e mperat ure . 29
8.2.3  Thermal endurance test. 30
8.2.4  Dielectric strength test . 30
8.2.5  Cable pull test . 31
8.2.6  Pressure test for Group I and Group II electrical equipment . 32
8.2.7  Test for resettable thermal protective device . 32
8.2.8  Sealing test for built-in protective devices . 33
9  Routine verifications and tests . 33
9.1  Visual inspections . 33
9.2  Dielectric strength test . 33
10  Marking . 34
Annex A (informative) Basic requirements for compounds for “m” equipment . 35
Annex B (normative informative) Allocation of test samples . 36
Bibliography . . 37

Figure 1 – Dimensional key for thickness through the compound . 19
Figure 2 – Minimum distances for multi-layer printed wiring boards . 22
Figure 3 – Fitting of blocking diodes . 25
Figure A.1  Basic requirements for compounds for “m” equipment . 35

Table 1 – Distances through the compound . 16
Table 2 – Minimum thickness of compound adjacent to free space for Group III “m”
equipment . . 17
Table 3 – Minimum thickness of compound adjacent to free space for Group I and
Group II “m” equipment . 18
Table 4 – Thickness of the compound . 20

– 4 – IEC 60079-18:2014 RLV  IEC 2014

Table 5 – Minimum distances for multi-layer printed wiring boards . 21
Table 6 – Test pressure . 32
Table B.1  Allocation of test samples . 36

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 18: Equipment protection by encapsulation “m”

FOREWORD
1) The International Electrotechnical Commission (IEC) is a w
...

IEC 60079-18 ®
Edition 4.0 2014-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 18: Equipment protection by encapsulation “m”

Atmosphères explosives –
Partie 18: Protection du matériel par encapsulage "m"

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
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The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

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IEC 60079-18 ®
Edition 4.0 2014-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 18: Equipment protection by encapsulation “m”

Atmosphères explosives –
Partie 18: Protection du matériel par encapsulage "m"

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX W
ICS 29.260.20 ISBN 978-2-8322-1994-2

– 2 – IEC 60079-18:2014  IEC 2014
CONTENTS
FOREWORD . 5
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 General . 10
4.1 Level of protection (equipment protection level (EPL)) . 10
4.2 Additional requirements for levels of protection “ma” and “mb” . 10
4.3 Additional requirements for level of protection “ma” . 10
4.4 Rated voltage and prospective short circuit current . 11
5 Requirements for compounds . 11
5.1 General . 11
5.2 Specification . 11
5.3 Properties of the compound . 11
5.3.1 Water absorption . 11
5.3.2 Dielectric strength . 11
6 Temperatures . 12
6.1 General . 12
6.2 Determination of the limiting temperatures . 12
6.2.1 Maximum surface temperature . 12
6.2.2 Temperature of the compound . 12
6.3 Temperature limitation . 12
7 Constructional requirements . 12
7.1 General . 12
7.2 Determination of faults . 13
7.2.1 Fault examination . 13
7.2.2 Components considered as not subject to fail . 13
7.2.3 Isolating components . 14
7.2.4 Infallible separation distances . 14
7.3 Free space in the encapsulation . 15
7.3.1 Group III “m” equipment . 15
7.3.2 Group I and Group II “m” equipment . 16
7.4 Thickness of the compound. 17
7.4.1 “m” equipment . 17
7.4.2 Windings for electrical machines . 19
7.4.3 Rigid, multi-layer printed wiring boards with through connections . 19
7.5 Switching contacts . 20
7.5.1 General . 20
7.5.2 Level of protection “ma” . 21
7.5.3 Level of protection “mb” . 21
7.5.4 Level of protection “mc” . 21
7.6 External connections . 21
7.6.1 General . 21
7.6.2 Additional requirements for “ma” equipment . 21
7.7 Protection of bare live parts . 21
7.8 Cells and batteries . 21
7.8.1 General . 21

7.8.2 Prevention of gassing . 22
7.8.3 Protection against inadmissible temperatures and damage to the cells
or batteries . 22
7.8.4 Reverse current . 22
7.8.5 Current limitation . 23
7.8.6 Protection against the polarity inversion and deep discharge of the cells . 23
7.8.7 Charging of cells or batteries . 23
7.8.8 Requirements for control safety devices for cells or batteries. 24
7.9 Protective devices . 24
7.9.1 General . 24
7.9.2 Electrical protective devices . 25
7.9.3 Thermal protective devices . 25
7.9.4 Built-in protective devices . 26
8 Type tests . 26
8.1 Tests on the compound . 26
8.1.1 Water absorption test . 26
8.1.2 Dielectric strength test . 26
8.2 Tests on the apparatus . 26
8.2.1 Test sequence . 26
8.2.2 Maximum temperature . 27
8.2.3 Thermal endurance test . 27
8.2.4 Dielectric strength test . 28
8.2.5 Cable pull test .
...

IEC 60079-18 ®
Edition 4.1 2017-08
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 18: Equipment protection by encapsulation “m”
Atmosphères explosives –
Partie 18: Protection du matériel par encapsulage "m"
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
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et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
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Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
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variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
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If you wish to give us your feedback on this publication or TC 37, 77, 86 and CISPR.

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Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
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IEC 60079-18 ®
Edition 4.1 2017-08
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 18: Equipment protection by encapsulation “m”

Atmosphères explosives –
Partie 18: Protection du matériel par encapsulage "m"

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-4770-9

IEC 60079-18 ®
Edition 4.1 2017-08
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Explosive atmospheres –
Part 18: Equipment protection by encapsulation “m”

Atmosphères explosives –
Partie 18: Protection du matériel par encapsulage "m"

– 2 – IEC 60079-18:2014+AMD1:2017 CSV
 IEC 2017
CONTENTS
FOREWORD . 5
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 General . 10
4.1 Level of protection (equipment protection level (EPL)) . 10
4.2 Additional requirements for levels of protection “ma” and “mb” . 10
4.3 Additional requirements for level of protection “ma” . 10
4.4 Rated voltage and prospective short circuit current . 11
5 Requirements for compounds . 11
5.1 General . 11
5.2 Specification . 11
5.3 Properties of the compound . 11
5.3.1 Water absorption . 11
5.3.2 Dielectric strength . 11
6 Temperatures . 12
6.1 General . 12
6.2 Determination of the limiting temperatures . 12
6.2.1 Maximum surface temperature . 12
6.2.2 Temperature of the compound . 12
6.3 Temperature limitation . 12
7 Constructional requirements . 12
7.1 General . 12
7.2 Determination of faults . 13
7.2.1 Fault examination . 13
7.2.2 Components considered as not subject to fail . 13
7.2.3 Isolating components . 14
7.2.4 Infallible separation distances . 14
7.3 Free space in the encapsulation . 15
7.3.1 Group III “m” equipment . 15
7.3.2 Group I and Group II “m” equipment . 16
7.4 Thickness of the compound. 17
7.4.1 “m” equipment . 17
7.4.2 Windings for electrical machines . 19
7.4.3 Rigid, multi-layer printed wiring boards with through connections . 19
7.5 Switching contacts . 20
7.5.1 General . 20
7.5.2 Level of protection “ma” . 21
7.5.3 Level of protection “mb” . 21
7.5.4 Level of protection “mc” . 21
7.6 External connections . 21
7.6.1 General . 21
7.6.2 Additional requirements for “ma” equipment . 21
7.7 Protection of bare live parts . 21
7.8 Cells and batteries . 21
7.8.1 General . 21

 IEC 2017
7.8.2 Prevention of gassing . 22
7.8.3 Protection against inadmissible temperatures and damage to the cells
or batteries . 22
7.8.4 Reverse current . 22
7.8.5 Current limitation . 23
7.8.6 Protection against the polarity inversion and deep discharge of the cells . 23
7.8.7 Charging of cells or batteries . 23
7.8.8 Requirements for control safety devices for cells or batteries. 24
7.9 Protective devices . 24
7.9.1 General . 24
7.9.2 Electrical protective devices . 25
7.9.3 Thermal protective devices . 25
7.9.4 Built-in protective devices . 26
8 Type tests . 26
8.1 Tests on the compound . 26
8.1.1 Water absorption test . 26
8.1.2 Dielectric strength test . 26
8.2 Tests on the apparatus . 26
8.2.1 Test sequence . 26
8.2.2 Maximum temperature . 27
8.2.3 Thermal endurance test . 27
8.2.4 Dielectric strength test . 28
8.2.5 Cable pull test . 28
8.2.6 Pressure test for Group I and Group II electrical equipment . 29
8.2.7 Test for resettable therma
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