EN 60079-31:2014

SLOVENSKI STANDARD
01-september-2014
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SIST EN 60079-31:2010
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Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure
"t" (IEC 60079-31:2013)
Explosionsgefährdete Bereiche - Teil 31: Geräte-Staubexplosionsschutz durch Gehäuse
„t“ (IEC 60079-31:2013)
Atmosphères explosives - Partie 31: Protection du matériel contre l'inflammation des
poussières par enveloppe "t" (CIE 60079-31:2013)
Ta slovenski standard je istoveten z: EN 60079-31:2014
ICS:
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 60079-31

NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2014
ICS 29.260.20 Supersedes EN 60079-31:2009
English Version
Explosive atmospheres - Part 31: Equipment dust ignition
protection by enclosure "t"
(IEC 60079-31:2013)
Atmosphères explosives - Partie 31: Protection contre Explosionsgefährdete Bereiche - Teil 31: Geräte-
l'inflammation de poussières par enveloppe "t" relative au Staubexplosionsschutz durch Gehäuse "t"
matériel (IEC 60079-31:2013)
(CEI 60079-31:2013)
This European Standard was approved by CENELEC on 2014-01-01. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 60079-31:2014 E
Foreword
The text of document 31/1079/FDIS, future edition 2 of IEC 60079-31, prepared by IEC/TC 31 "Equipment
for explosive atmospheres" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC
as EN 60079-31:2014.
The following dates are fixed:
(dop) 2015-01-01
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2017-01-01
• latest date by which the national
standards conflicting with the
document have to be withdrawn
This document supersedes EN 60079-31:2009.

The State of the Art is included in Annex ZY “Significant changes between this European Standard and
EN 60079-31:2009”.
For the significant changes with respect to EN 60079-31:2009, see Annex ZY.

This standard is to be read in conjunction with EN 60079-0.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights.

This document has been prepared under a mandate given to CENELEC by the European Commission and
the European Free Trade Association, and supports essential requirements of EU Directive.

For the relationship with EU Directive see informative Annex ZZ, which is an integral part of this document.

Endorsement notice
The text of the International Standard IEC 60079-31:2013 was approved by CENELEC as a European
Standard without any modification.

- 3 - EN 60079-31:2014
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.

NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here: www.cenelec.eu

Publication Year Title EN/HD Year

IEC 60079-0 - Explosive atmospheres - EN 60079-0 -
Part 0: Equipment - General requirements

IEC 60127 Series Miniature fuses EN 60127 Series

IEC 60691 - Thermal-links - Requirements and application EN 60691 -
guide
ISO 965-1 - ISO general-purpose metric screw threads - - -
Tolerances -
Part 1: Principles and basic data

Annex ZZ
(informative)
Coverage of Essential Requirements of EU Directives

This European Standard has been prepared under a mandate given to CENELEC by the European
Commission and the European Free Trade Association and within its scope the standard covers only the
following essential requirements out of those given in Annex II of the EU Directive 94/9/EC:

– ER 1.0.1, ER 1.0.2 (partly), ER 1.0.4, ER 1.0.5 (partly)
– ER 1.1
– ER 1.2.1 (partly), ER 1.2.2 (partly)
– ER 1.2.4
– ER 1.2.7
– ER 1.2.8 (partly)
– ER 1.3.1
– ER 1.6.4
– ER 2.1
– ER 2.2
– ER 2.3
Compliance with this standard provides one means of conformity with the specified essential requirements of
the Directive concerned.
WARNING: Other requirements and other EU Directives may be applicable to the products falling within the
scope of this standard.
- 5 - EN 60079-31:2014
Annex ZY
(informative)
Significant changes between this European Standard and EN 60079-31:2009
This European Standard supersedes EN 60079-31:2009.
The significant changes with respect to EN 60079-31:2009 are as listed below.
Type
Changes Clause Minor and Extension Major technical
editorial changes
changes
Document has been restructured from the first edition Numerous X

The marked maximum surface temperature shall be 4.3.2 C1

measured on the external surfaces of the enclosure and
the surfaces of the internal components for equipment
with types of protection “ta”
Additional protection for arcing and sparking parts for “ta” 4.3.6 C2

Limiting the internal pressure test to enclosures where 4.4.2 X

the seal is not physically constrained from moving.
Requirements for tapered threaded joints without an 5.1.2 X

additional seal or gasket added.
Requirements for cable gland aligned for all levels and 5.2 X

Groups the only difference is now the required IP
protection
Requirements for plain entries added 5.3.1 X

5 threads for parallel threads only required when no 5.3.2 X

seal is used
Test for internal enclosure for level “ta” added. 6.1.1.2 C 3

Eliminating of the “fault” table and reduction of the dust 6.1.2 X

layer depth for the thermal test for type of protection “ta”.

NOTE  The technical changes referred to include the significance of technical changes in the revised EN standard, but they
do not form an exhaustive list of all modifications from the previous version. More guidance may be found by referring to
the Redline Version of the standard.

Explanations:
A) Definitions
Minor and editorial changes
clarification
decrease of technical requirements
minor technical change
editorial corrections
These are changes which modify requirements in an editorial or a minor technical way. They
include changes of the wording to clarify technical requirements without any technical change,
or a reduction in level of existing requirement.

Extension addition of technical options

These are changes which add new or modify existing technical requirements, in a way that
new options are given, but without increasing requirements for equipment that was fully
compliant with the previous standard. Therefore, these will not have to be considered for
products in conformity with the preceding edition.

Major technical changes
addition of technical requirements
increase of technical requirements

These are changes to technical requirements (addition, increase of the level or removal) made in a
way that a product in conformity with the preceding edition will not always be able to fulfil the
requirements given in the later edition. These changes have to be considered for products in
conformity with the preceding edition. For these changes additional information is provided in
Clause B) below.
NOTE  These changes represent current technological knowledge. However, these changes should not normally have
an influence on equipment already placed on the market.

B) Information about the background of ‘Major Technical Changes’

C1 – A requirement was added for “ta” to require the temperature marking to be based on the
highest of either the temperature produced by the internal components or the external surface
temperature.
C2 – Requirements were added for “ta” equipment that contains a normally arcing part to
require a supplementary internal enclosure around the arcing part.

C3 – Requires an impact test on the supplementary enclosure for “ta” equipment.

IEC 60079-31 ®
Edition 2.0 2013-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 31: Equipment dust ignition protection by enclosure "t"

Atmosphères explosives –
Partie 31: Protection contre l’inflammation de poussières par enveloppe “t”

relative au matériel
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX N
ICS 29.260.20 ISBN 978-2-8322-1185-4

– 2 – 60079-31 © IEC:2013
CONTENTS
FOREWORD . 3
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 General . 7
4.1 Levels of protection . 7
4.2 Equipment groups and ingress protection. 7
4.3 Requirements for electrical equipment with level of protection “ta” . 8
4.3.1 Fault current . 8
4.3.2 Maximum surface temperature . 8
4.3.3 Overpressure . 8
4.3.4 Dust exclusion . 8
4.3.5 Protective devices . 8
4.3.6 Protection for arcing and sparking parts . 9
4.4 Requirements for electrical equipment with Level of Protection “tb” and
“tc” . 9
4.4.1 Maximum surface temperature . 9
4.4.2 Over pressure . 9
4.4.3 Dust exclusion . 9
5 Construction . 9
5.1 Joints . 9
5.1.1 General . 9
5.1.2 Threaded joints . 10
5.1.3 Gaskets and seals . 10
5.1.4 Cemented joints . 10
5.1.5 Operating rods, spindles and shafts . 10
5.1.6 Windows . 10
5.2 Cable glands . 11
5.3 Entries . 11
5.3.1 Plain entries . 11
5.3.2 Threaded entries . 11
6 Verification and tests . 11
6.1 Type tests . 11
6.1.1 Type tests for dust exclusion by enclosures . 11
6.1.2 Thermal tests . 12
6.2 Routine tests . 12
7 Marking . 12
Bibliography . 14

Table 1 – Level of Protection, equipment group and ingress protection (IP) relationship . 7

60079-31 © IEC:2013 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 31: Equipment dust ignition protection by enclosure "t"

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 IEC 60079-31 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This second edition cancels and replaces the first edition published in 2008. This edition
constitutes a technical revision.

– 4 – 60079-31 © IEC:2013
The significance of changes between IEC 60079-31, Edition 2.0 (2012) and IEC 60079-31,
Edition 1.0 (2008) (including Corrigendum) is as listed below:
Type
Changes Clause Minor and Extension Major technical
changes
editorial
changes
Document has been restructured from the first edition Numerous X
The marked maximum surface temperature shall be 4.3.2  C1
measured on the external surfaces of the enclosure and
the surfaces of the internal components for equipment
with types of protection “ta”
Additional protection for arcing and sparking parts for “ta” 4.3.6  C2
Limiting the internal pressure test to enclosures where 4.4.2 X
the seal is not physically constrained from moving.
Requirements for tapered threaded joints without an 5.1.2 X
additional seal or gasket added.

Requirements for cable gland aligned for all levels and 5.2 X
Groups the only difference is now the required IP
protection
Requirements for plain entries added 5.3.1 X
5 threads for parallel threads only required when no 5.3.2 X
seal is used
Test for internal enclosure for level “ta” added. 6.1.1.2  C 3
Eliminating of the “fault” table and reduction of the dust 6.1.2 X
layer depth for the thermal test for type of protection “ta”.

NOTE The technical changes referred to include the significance of technical changes in the revised IEC
Standard, but they do not form an exhaustive list of all modifications from the previous version. More guidance may
be found by referring to the Redline Version of the standard.
Explanations:
A) Definitions
Minor and editorial changes
clarification
decrease of technical requirements
minor technical change
editorial corrections
These are changes which modify requirements in an editorial or a minor technical way. They
include changes of the wording to clarify technical requirements without any technical change,
or a reduction in level of existing requirement.
Extension addition of technical options
These are changes which add new or modify existing technical requirements, in a way that
new options are given, but without increasing requirements
...