Explosive atmospheres - Part 26: Equipment with Separation Elements or combined Levels of Protection

IEC 60079-26:2021 specifies requirements for construction, testing and marking for Ex Equipment that contains parts of the equipment with different Equipment Protection Levels (EPLs) and a separation element. This equipment is mounted across a boundary where different EPLs are required, for example between different gas hazardous areas, dust hazardous areas or gas hazardous areas adjacent to dust hazardous areas.
Separation elements are considered for both electrical and non-electrical equipment. If mechanical energy can be transformed into a potential ignition source, additionally an ignition hazard assessment in accordance with ISO 80079-36 is performed and appropriate measures are undertaken.
This document also specifies requirements for the combination of two Types of Protection, each with EPL Gb, to achieve EPL Ga.
This document supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this document conflicts with a requirement of IEC 60079-0, the requirement of this document takes precedence. This fourth edition cancels and replaces the third edition and constitutes a technical revision.
Please see the IEC 60079-26:2020 foreword for a description of the main changes with respect to the previous edition.

Atmosphères explosives - Partie 26: Appareil avec éléments de séparation ou niveaux de protection combinés

IEC 60079-26:2021 spécifie les exigences de construction, d’essai et de marquage, par exemple, des appareils contenant des parties d’appareils présentant différents niveaux de protection de l’appareil (EPL, Equipment Protection Level) et un élément de séparation. Cet appareil est installé en chevauchement sur des emplacements pour lesquels différents EPL sont exigés, par exemple entre différentes zones gazeuses dangereuses, entre différentes zones poussiéreuses dangereuses ou entre des zones gazeuses dangereuses placées à côté de zones poussiéreuses dangereuses.
EXEMPLE: Appareil installé dans le mur des réservoirs de stockage situés dans la Zone 1 et englobant la Zone 0.
Les éléments de séparation sont pris en considération tant pour les appareils électriques que pour les appareils non électriques. Si l’énergie mécanique peut devenir une source potentielle d’inflammation, une évaluation du danger d’inflammation selon l’ISO 80079-36 est réalisée, et des mesures appropriées sont prises. Les mesures appropriées peuvent être sélectionnées dans l’ISO 80079-37 ou l’IEC TS 60079-42.
Le présent document spécifie également les exigences relatives à la combinaison de deux modes de protection, chacun avec EPL Gb, pour atteindre EPL Ga. Des exemples sont donnés en 4.2.
Le présent document complète et modifie les exigences générales de l’IEC 60079-0. Lorsqu’une exigence du présent document entre en contradiction avec une exigence de l’IEC 60079-0, l’exigence du présent document prévaut.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente.

General Information

Status
Published
Publication Date
24-Feb-2021
Current Stage
PPUB - Publication issued
Completion Date
25-Feb-2021
Ref Project

Buy Standard

Standard
IEC 60079-26:2021 - Explosive atmospheres - Part 26: Equipment with Separation Elements or combined Levels of Protection
English and French language
47 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

IEC 60079-26
Edition 4.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 26: Equipment with Separation Elements or combined Levels of Protection
Atmosphères explosives –
Partie 26: Appareil avec éléments de séparation ou niveaux de protection
combinés
IEC 60079-26:2021-02(en-fr)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2021 IEC, Geneva, Switzerland

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

ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie

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

questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez

les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
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 IEC online collection - oc.iec.ch

The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the

variety of criteria (reference number, text, technical publications previews. With a subscription you will always

committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.

and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary
(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC

La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des

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

plus récente, un corrigendum ou amendement peut avoir été publié.
Recherche de publications IEC - IEC online collection - oc.iec.ch

webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez

La recherche avancée permet de trouver des publications IEC gratuitement tous les aperçus des publications. Avec un

en utilisant différents critères (numéro de référence, texte, abonnement, vous aurez toujours accès à un contenu à jour

comité d’études, …). Elle donne aussi des informations sur adapté à vos besoins.
les projets et les publications remplacées ou retirées.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
Le premier dictionnaire d'électrotechnologie en ligne au
Restez informé sur les nouvelles publications IEC. Just
monde, avec plus de 22 000 articles terminologiques en
Published détaille les nouvelles publications parues.
anglais et en français, ainsi que les termes équivalents dans
Disponible en ligne et une fois par mois par email.
16 langues additionnelles. Egalement appelé Vocabulaire
Electrotechnique International (IEV) en ligne.
Service Clients - webstore.iec.ch/csc
Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
---------------------- Page: 2 ----------------------
IEC 60079-26
Edition 4.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 26: Equipment with Separation Elements or combined Levels of Protection
Atmosphères explosives –
Partie 26: Appareil avec éléments de séparation ou niveaux de protection
combinés
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-9390-4

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.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60079-26:2021 © IEC 2021
CONTENTS

FOREWORD ........................................................................................................................... 4

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

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

3 Terms and definitions ...................................................................................................... 8

4 Ex Equipment with two combined Types of Protection ..................................................... 8

4.1 General ................................................................................................................... 8

4.2 Basic requirements ................................................................................................. 8

4.3 Electrical Connections ............................................................................................ 9

5 Ex Equipment containing parts with different EPLs and a separation element .................. 9

5.1 General ................................................................................................................... 9

5.2 Separation elements ............................................................................................... 9

5.2.1 General ........................................................................................................... 9

5.2.2 Basic requirements ........................................................................................ 10

5.2.3 Mechanical partition walls .............................................................................. 10

5.2.4 Metallic partition walls with gas-tight conductor bushings ............................... 10

5.2.5 Partition wall supplemented with a joint ......................................................... 11

5.2.6 Partition wall for explosive gas atmospheres supplemented with natural

ventilation ...................................................................................................... 11

5.2.7 Requirements depending on the thickness of the partition wall ...................... 12

6 Process connection ....................................................................................................... 13

7 Type tests ..................................................................................................................... 14

7.1 Standardized Types of Protection ......................................................................... 14

7.2 Separation elements ............................................................................................. 14

7.3 Temperature evaluation ........................................................................................ 14

8 Marking ......................................................................................................................... 14

8.1 General ................................................................................................................. 14

8.2 Ex Equipment with two combined Types of Protection ........................................... 14

8.3 Ex Equipment containing parts with different EPLs................................................ 15

8.4 Examples of marking:............................................................................................ 15

9 Instructions .................................................................................................................... 16

9.1 Separation elements ............................................................................................. 16

9.2 Process connection ............................................................................................... 16

9.3 EPL allocation ....................................................................................................... 16

Annex A (normative) Types of construction for separation elements ................................... 17

Bibliography .......................................................................................................................... 23

Figure 1 – Partition wall with a conductor bushing considered as gas diffusion tight.............. 11

Figure 2 – Example of a separation element with a cylindrical shaft joint and ventilation ....... 12

Figure 3 – Example g) of marking of equipment with a separation element............................ 15

Table 1 – Requirements for Ex Equipment containing parts with different EPLs. ..................... 9

Table A.1 – Ex Equipment with separation elements mounted at a boundary of Zone 0......... 17

Table A.2 – Ex Equipment with separation elements mounted at a boundary of Zone 1......... 18

Table A.3 – Ex Equipment with separation elements mounted at a boundary of Zone 20 ....... 19

Table A.4 – Ex Equipment with separation elements mounted at a boundary of Zone 21 ....... 19

---------------------- Page: 4 ----------------------
IEC 60079-26:2021 © IEC 2021 – 3 –

Table A.5 – Ex Equipment with separation elements mounted at a boundary of Zone 0

in Zone 21 or 22 ................................................................................................................... 20

Table A.6 – Ex Equipment with separation elements mounted at a boundary of Zone 1

in Zone 21 or 22 ................................................................................................................... 20

Table A.7 – Ex Equipment with separation elements mounted at a boundary of Zone 20

in Zone 1 or 2 ...................................................................................................................... 21

Table A.8 – Ex Equipment with separation elements mounted at a boundary of Zone 21

in Zone 1 or 2 ...................................................................................................................... 22

---------------------- Page: 5 ----------------------
– 4 – IEC 60079-26:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 26: Equipment with Separation Elements
or combined Levels of Protection
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 60079-26 has been prepared by IEC technical committee 31:

Equipment for explosive atmospheres.

This fourth edition cancels and replaces the third edition published in 2014 and constitutes a

technical revision.
---------------------- Page: 6 ----------------------
IEC 60079-26:2021 © IEC 2021 – 5 –

This edition includes the following significant changes with respect to the previous edition:

Type
Minor and Major
Changes Clause
editorial Extension technical
changes changes
The scope of the standard was extended for separation 5 x
elements between all EPLs for gas and dust hazardous
areas as well as for non-electrical equipment. The title
and the structure of the standard was modified
accordingly.
The requirements for combined Types of Protection 4.1.2 4 x
were restructured and included in Clause 4
The requirements for equipment with moving parts was 4.2 x
removed and transferred to IEC 60079-0 (ed. 3)
For equipment with partition walls other than corrosion 7.2 C1
resistant metals, glass or ceramic the type tests were
detailed and the cycling test acc. to IEC TS 60079-40
specified, if they were exposed to constant vibrational
stress
The marking is extended for equipment to be mounted 8 x
between different Zones
The thickness of the partition wall must be specified in 9 x
the instructions
Additional warnings are included in the instructions for 9 x
equipment with separation elements exposed to abrasive
dust flow
Table 1 "Separation elements" was moved to Annex A as Table A.1 x
Table A.1 and modified for clarification
Table A.2 to table A.8 added for the extended separation
x
elements

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.

Explanation of the types of changes:
A) Definitions
1. 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.
2. 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.
---------------------- Page: 7 ----------------------
– 6 – IEC 60079-26:2021 © IEC 2021
3. 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 to ensure that partition walls consisting of materials other than stainless steel, ceramics or

glass, which are exposed to pressure or vibrational stress, provide a comparable level of

safety, additional endurance tests were included. Reference to tests in IEC TS 60079-40

were considered appropriate.
The text of this International Standard is based on the following documents:
FDIS Report on voting
31/1562/FDIS 31/1564/RVD

Full information on the voting for the approval of this International Standard can be found in the

report on voting indicated in the above table.

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

A list of all parts in the IEC 60079 series, published under the general title Explosive

atmospheres, can be found on the IEC website.

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

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

the specific document. At this date, the document 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.

---------------------- Page: 8 ----------------------
IEC 60079-26:2021 © IEC 2021 – 7 –
EXPLOSIVE ATMOSPHERES –
Part 26: Equipment with Separation Elements
or combined Levels of Protection
1 Scope

This part of IEC 60079 specifies requirements for construction, testing and marking for Ex

Equipment that contains parts of the equipment with different Equipment Protection Levels

(EPLs) and a separation element. This equipment is mounted across a boundary where different

EPLs are required, for example between different gas hazardous areas, dust hazardous areas

or gas hazardous areas adjacent to dust hazardous areas.

EXAMPLE: Equipment installed in the wall of storage tanks located in Zone 1 and containing Zone 0 inside.

Separation elements are considered for both electrical and non-electrical equipment. If

mechanical energy can be transformed into a potential ignition source, additionally an ignition

hazard assessment in accordance with ISO 80079-36 is performed and appropriate measures

are undertaken. Suitable measures can be selected from ISO 80079-37 or IEC TS 60079-42.

This document also specifies requirements for the combination of two Types of Protection, each

with EPL Gb, to achieve EPL Ga. Examples are included in 4.2.

This document supplements and modifies the general requirements of IEC 60079-0. Where a

requirement of this document conflicts with a requirement of IEC 60079-0, the requirement of

this document takes precedence.
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 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements

IEC 60079-1, Explosive atmospheres – Part 1: Equipment protection by flameproof enclosures

"d"

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

IEC 60079-31, Explosive atmospheres – Part 31: Equipment dust ignition protection by

enclosure "t"

IEC TS 60079-40, Explosive atmospheres – Part 40: Requirements for process sealing between

flammable process fluids and electrical systems
IEC 60529, Degrees of protection provided by enclosures (IP Code)

IEC 60695-11-10, Fire hazard testing – Part 11-10: Test flames – 50 W horizontal and vertical

flame test methods
---------------------- Page: 9 ----------------------
– 8 – IEC 60079-26:2021 © IEC 2021

ISO 80079-36, Explosive atmospheres – Part 36: Non-electrical equipment for explosive

atmospheres – Basic method and requirements
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60079-0 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
4 Ex Equipment with two combined Types of Protection
4.1 General

To achieve EPL Ga, electrical equipment may comply with the requirements of two independent

Types of Protection each of EPL Gb. If one Type of Protection fails, the other Type of Protection

shall continue to function. Then even during rare malfunctions, for example two independent

faults, no ignition source can occur.
4.2 Basic requirements

The independent Types of Protection shall not have a common mode of failure, except as

specified below (see a) and b)). Combined Types of Protection of EPL Gb shall depend on

different physical protection principles.

NOTE 1 An example for an unacceptable common mode of failure is an Ex "db" enclosure containing arcing

components installed inside an Ex "eb" enclosure. Should the Ex "db" enclosure be compromised, it would also

compromise the Ex "eb" enclosure.

NOTE 2 The combination of Ex "db" and Ex "q" both depend on the avoidance of flame propagation (same physical

protection principle) and are not suitable in combination. In practice, some combinations are not suitable, for example

the combination of liquid immersion "ob" and powder filling "q".

Both Types of Protection shall be assessed using the most onerous malfunction condition of

the other Type of Protection. When combining intrinsic safety, i.e. Level of Protection "ib", with

another Type of Protection, the second Type of Protection shall be assessed after the

application of faults to the intrinsically safe apparatus which result in the most onerous condition

as specified in IEC 60079-11. Thermal dissipation shall be considered in case of a fault of one

Type of Protection.

When using two Types of Protection, which both rely on the same parameter (for example, the

creepage distance when combining Ex "ib" with Ex "eb"), the most stringent requirement of both

Types of Protection shall be applied.

If two Types of Protection are combined which both rely on the enclosure, one of the following

shall be met:

a) if two enclosures are used (one totally enclosed within the other), each enclosure shall

comply with the requirements of the respective Type of Protection; or

b) if only one enclosure is used, the enclosure and the Cable Glands shall meet the impact

test requirements of IEC 60079-0, using the Group I values.

Examples of relevant combinations of two independent Types of Protection are as follows:

– inductive transmitters (for example proximity switches, electrical position sensors) with

intrinsic safety "ib" enclosed by encapsulation "mb";
---------------------- Page: 10 ----------------------
IEC 60079-26:2021 © IEC 2021 – 9 –

NOTE The connections to intrinsically safe "ib" circuits can be protected by increased safety "eb";

– a luminaire designed as increased safety "eb" included in a flameproof enclosure "db";

– measuring transducers with intrinsic safety "ib" enclosed by a flameproof enclosure "db";

– equipment with electrical circuits of intrinsic safety "ib", additionally protected by powder

filling "q";

– electromagnetic valves with encapsulation "mb", enclosed by a flameproof enclosure "db";

– increased safety "eb", with pressurized equipment "pxb".
4.3 Electrical Connections

Electrical connections and permanently connected cables of the equipment sited within an area

requiring EPL Ga shall comply with EPL Ga.

NOTE Installation requirements for equipment with EPL Ga achieved by combined types of protection are in

IEC 60079-14, Edition 6 .
5 Ex Equipment containing parts with different EPLs and a separation element
5.1 General

Equipment which is mounted through or forms part of the boundary wall between different Zones

may contain different parts which comply with different EPLs. In this case the equipment shall

contain a separation element between the different parts of the equipment (see Table 1).

Table 1 – Requirements for Ex Equipment containing parts with different EPLs.
Part complying with
EPL Ga EPL Gb EPL Da EPL Db
EPL Gb Table A.1 - Table A.7 Table A.8
EPL Gc Table A.1 Table A.2 Table A.7 Table A.8
Part complying
with
EPL Db Table A.5 Table A.6 Table A.3 -
EPL Dc Table A.5 Table A.6 Table A.3 Table A.4
NOTE Boundaries are not considered for hybrid mixtures.

Equipment which fully complies with one EPL, which is suitable for both of the Zones on either

side of the boundary does not require a separation element complying with the requirements of

this document.
5.2 Separation elements
5.2.1 General

A separation element consists of a mechanical partition wall, which may be supplemented with

a flameproof joint, a dust-tight joint, a natural ventilation or a combination of these, as applicable

and detailed in 5.2.2 to 5.2.7 and Annex A.
___________
Under consideration.
---------------------- Page: 11 ----------------------
– 10 – IEC 60079-26:2021 © IEC 2021
5.2.2 Basic requirements
The following basic requirements apply for separation elements:

a) a separation element shall provide a boundary between different areas or parts of the

equipment complying with different EPLs to avoid a migration of flammable gasses, vapours

or dusts from parts of the equipment with higher EPL into parts of the equipment with lower

EPL;

b) if a potential ignition source becomes active in the part of the equipment with the lower EPL,

it shall not act as an ignition source in the part of the equipment with the higher EPL, for

example the permissible surface temperature of the separation element shall not be

exceeded; and

c) if an ignition can occur in the part of the equipment with the lower EPL, flame propagation

into the part with the higher EPL shall be avoided. This consideration is not applicable to

EPL Db or Dc enclosures with dust exclusion according to IP 5X.

NOTE EPL Gc is considered lower than EPL Gb or EPL Ga. EPL Gb is considered lower than EPL Ga. The same

principle applies to EPLs Da, Db and Dc.
5.2.3 Mechanical partition walls
Partition walls shall be constructed of either:
a) corrosion-resistant metal, glass or ceramic;

b) other materials which can be verified as providing the same level of safety. In this case, the

certificate number shall include the "X" suffix in accordance with the marking requirements

of IEC 60079-0, the certificate shall include the Specific Conditions
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.