IEC 60079-11:2011
(Main)Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"
Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"
IEC 60079-11:2011 is now available as IEC Standards+ 60079-11:2011 which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60079-11:2011 specifies the construction and testing of intrinsically safe apparatus intended for use in an explosive atmosphere and for associated apparatus, which is intended for connection to intrinsically safe circuits which enter such atmospheres. This type of protection is applicable to electrical equipment in which the electrical circuits themselves are incapable of causing an explosion in the surrounding explosive atmospheres. This standard is also applicable to electrical equipment or parts of electrical equipment located outside the explosive atmosphere or protected by another Type of Protection listed in IEC 60079-0, where the intrinsic safety of the electrical circuits in the explosive atmosphere may depend upon the design and construction of such electrical equipment or parts of such electrical equipment. The electrical circuits exposed to the explosive atmosphere are evaluated for use in such an atmosphere by applying this standard. The requirements for intrinsically safe systems are provided in IEC 60079-25. This standard supplements and modifies the general requirements of IEC 60079-0, except as indicated in Table 1. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirements of this standard shall take precedence. This sixth edition cancels and replaces the fifth edition of IEC 60079-11 published in 2006, the first edition of IEC 61241-11 published in 2005, and partially replaces the second edition of IEC 60079-27 published in 2008 and constitutes a full technical revision. The significant changes with respect to the previous edition are listed below:
- Inclusion of non-edition specific references to IEC 60079-0.
- The merging of the apparatus requirements for FISCO from IEC 60079-27.
- The merging of the requirements for combustible dust atmospheres from IEC 61241-11.
- Clarification of the requirements for accessories connected to intrinsically safe apparatus; such as chargers and data loggers.
- Addition of new test requirements for opto-isolators.
- Introduction of Annex H about ignition testing of semiconductor limiting power supply circuits.
The contents of the corrigendum 1 (January 2012), the interpretation sheets 1 (October 2014), 2 (July 2016), 3 (July 2016), 4 (April 2019), 5 (August 2019), 6 (December 2019) and 7 (May 2024) have been included in this copy.
Atmosphères explosives - Partie 11: Protection de l'équipement par sécurité intrinsèque "i"
IEC 60079-11:2011 est disponible sous forme de IEC 60079-11:2011 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
IEC 60079-11:2011 spécifie la construction et les essais pour le matériel électrique de sécurité intrinsèque destiné à être utilisé dans les atmosphères explosives et pour le matériel électrique associé destiné à être relié à des circuits de sécurité intrinsèque qui entrent dans de telles atmosphères. Ce mode de protection s'applique aux équipements électriques dont les circuits sont eux-mêmes incapables de provoquer l'explosion de l'atmosphère environnante. La présente norme s'applique également aux équipements électriques ou aux parties de matériels électriques situés hors de l'atmosphère explosive ou protégés par un autre Mode de Protection cité dans la CEI 60079-0, lorsque la sécurité intrinsèque des circuits électriques situés dans l'atmosphère explosive peut dépendre de la conception et de la construction de ces matériels électriques ou de ces parties de matériels électriques. Les circuits électriques exposés à une atmosphère explosive sont évalués en vue de leur emploi dans une telle atmosphère en appliquant la présente Norme. Les exigences pour les systèmes de sécurité intrinsèque sont données dans la CEI 60079-25. La présente norme complète et modifie les exigences générales de la CEI 60079-0, à l'exception de ce qui est indiqué au Tableau 1. Lorsqu'une exigence de la présente norme entre en conflit avec une exigence de la CEI 60079-0, l'exigence de la présente Norme prévaut. Cette sixième édition annule et remplace la cinquième édition de la CEI 60079-11 publiée en 2006, la première édition de la CEI 61241-11 publiée en 2005, et remplace partiellem ent la seconde édition de la CEI 60079-27 publiée en 2008 dont elle constitue une révision technique complète. Les modifications importantes par rapport à l'édition antérieure sont indiquées ci-dessous:
- Introduction d'une référence à la CEI 60079-0 non spécifique à l'édition;
- L'incorporation des exigences de matériel issues de la CEI 60079-27 relatives au FISCO;
- L'incorporation des exigences issues de la CEI 61241-11 relatives aux atmosphères de poussières combustibles;
- La clarification des exigences relatives aux accessoires reliés à un matériel à sécurité intrinsèque;
- tels que les chargeurs et les collecteurs de données;
- Ajout de nouvelles exigences d'essai relatives aux isolateurs optiques;
- l'introduction d'une Annexe H;
- au sujet des essais d'inflammation des dispositifs de limitation d'alimentation électrique à semi-conducteur.
Les contenus du corrigendum 1 (janvier 2012) et des feuilles d'interprétation 1 (octobre 2014), 2 (juillet 2016), 3 (juillet 2016), 4 (avril 2019), 5 (août 2019, en anglais seulement), 6 (décembre 2019) et 7 (mai 2024, en anglais seulement) ont été pris en considération dans cet exemplaire.
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IEC 60079-11 ®
Edition 6.0 2011-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 11: Equipment protection by intrinsic safety "i"
Atmosphères explosives –
Partie 11: Protection de l’équipement par sécurité intrinsèque «i»
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by
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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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normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.
A propos des publications CEI
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IEC 60079-11 ®
Edition 6.0 2011-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 11: Equipment protection by intrinsic safety "i"
Atmosphères explosives –
Partie 11: Protection de l’équipement par sécurité intrinsèque «i»
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XG
ICS 29.260.20 ISBN 978-2-88912-520-3
SC 31G/IEC 60079-11 (2011), sixth edition/I-SH 01
EXPLOSIVE ATMOSPHERES –
Part 11: Equipment protection by intrinsic safety "i"
INTERPRETATION SHEET 1
This interpretation sheet has been prepared by subcommittee 31G: Equipment for explosive
atmospheres – Equipment protection by intrinsic safety "i", of IEC technical committee 31.
The text of this interpretation sheet is based on the following documents:
ISH Report on voting
31G/235/ISH 31G/238/RVISH
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.
___________
Following decision No 16 of the TC 31 meeting in Melbourne in 2011, the issuing of an
th
Interpretation Sheet for IEC 60079-11:2011 (6 edition ) was requested, in order to clarify the
th
significance of the changes with respect to the 5 edition.
Question
th
What are the minor editorial, extensions, and major technical changes of the 6 edition with
th
respect to the 5 edition?
Answer
The following table shows the significance of the changes.
The significance of the changes between IEC Standard, IEC 60079-11, Edition 5, 2006-07 and
IEC 60079-11, Edition 6, 2011-06 are as listed below
October 2014 ICS 29.260.20
Significance of changes with respect to IEC 60079-11:2006
Type
Significant Changes Clause Minor and Extension Major
editorial technical
changes changes
General: Changes to remove specific clause references to General x
other IEC 60079 standards
Scope: Expansion to include Group III 1 x
Scope: Table 1 updated to include references to both 1 x
IEC 60079-0 Edition 5 and Edition 6
Normative references: Deletion of IEC 60079-27, and addition 2 x
of IEC 61158-2 and IEC 62013-1
Terms and definitions: Commonly used definitions moved to 3 x
IEC 60079-0. Energy limitation definitions moved from
IEC 60079-0.New definitions added
Spark ignition compliance: Group III ignition requirements 5.5 x
added
Temperature for small components for Group I and Group II: 5.6.2 x
Relocated to IEC 60079-0
Intrinsically safe apparatus and component temperature for 5.6.5 x
Group III
Enclosures for Group I or Group II apparatus 6.1.2 x
Apparatus complying with Annex F 6.1.2.3 c) x
Enclosures for Group III apparatus 6.1.3 x
Requirements for connections and accessories for IS 6.2.5 C1
apparatus when located in the non-hazardous area
Separation of conductive parts 6.3.2 x
Encapsulation 6.6.1 x
Encapsulation used for the exclusion of explosive 6.6.2 C2
atmospheres
Primary and secondary cells and batteries 7.4.1 x
Battery construction 7.4.2 x
Level of Protection “ic” 8.1 x
Filter capacitors 8.6.2 x
Wiring, printed circuit board tracks, and connections 8.8 c) x
FISCO apparatus 9.2 x
Handlights and caplights 9.3 x
Circuits with both inductance and capacitance 10.1.5.2 x
Electrolyte leakage test for cells and batteries 10.5.2 x
Spark ignition and surface temperature of cells and batteries 10.5.3 x
Determination of the acceptability of fuses requiring 10.6.2 x
encapsulation
Optical isolators tests 10.11 x
Marking 12.1 x
Encapsulation Annex D C2
Fieldbus intrinsically safe concept (FISCO) – Apparatus Annex G x
requirements
Ignition testing of semiconductor limiting power supply circuits Annex H x
October 2014 ICS 29.260.20
Explanation of the Types of Significant 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.
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 – Requirements for external connections, other than battery charging connections, that are designed for use
only when an explosive gas or dust atmosphere is not present, for example when in a non-hazardous area or when
a gas-free permit is in force, have been added.
C2 – The requirements for encapsulation referenced in 6.6.2 and detailed in Annex D have been changed in terms
of the thickness to the free surface and are extended related to moulding. Annex D is changed from informative to
normative.
October 2014 ICS 29.260.20
IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-11
Edition 6.0 2011-06
EXPLOSIVE ATMOSPHERES –
Part 11: Equipment protection by intrinsic safety "i"
INTERPRETATION SHEET 2
This interpretation sheet has been prepared by subcommittee 31G: Intrinsically-safe
apparatus, of IEC technical committee 31: Equipment for explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
ISH Report on voting
31G/252/ISH 31G/254/RVD
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.
___________
Interpretation of 6.2.5 – Requirements for connections and accessories for IS apparatus
when located in the non-hazardous area
Question:
Does the first NOTE of 6.2.5 imply that equipment which may be connected to non-intrinsically
safe connection facilities of intrinsically safe apparatus restricted to use in non-hazardous
area need to be assessed applying IEC 60079-11, if the value of U is less than 250 V a.c.?
m
Does this furthermore apply to equipment to be connected to non-intrinsically safe connection
facilities of associated apparatus, if the value of U is less than 250 V a.c.?
m
Background:
The first NOTE of 6.2.5 requires in cases were U is specified less than 250 V a.c. that this
m
should not be derived from unassessed equipment. This is sometimes read as if the
requirements of IEC 60079-11 should be applied for voltage limitation to guarantee U .
m
Terminological entry 3.13.13 defines that U is the maximum voltage that can be applied to
m
the non intrinsically safe connection facilities of associated apparatus without invalidating the
ICS 29.260.20
– 2 – IEC 60079-11:2011/ISH2:2016
IEC 2016
type of protection. NOTE 1 of 3.13.13, as an example, explains that this may apply to
connection facilities used for charging batteries.
In IEC 60079-11 there are no measures required for limiting the voltage of non I.S. circuits to
the specified U value, except for the use of a single Zener diode protected by a fuse as an
m
integral measure of an associated apparatus limiting the voltage which can appear at a
transformer (8.3) or a coupler (8.9.2).
IEC 60079-14: 2013, 16.2.1 states:
Where U marked on the associated apparatus is less than 250 V it shall be installed in
m
accordance with one of the following:
a) where U does not exceed 50 V a.c. or 120 V d.c., in an SELV or PELV system, or
m
b) via a safety isolating transformer complying with the requirements of IEC 61558-2-6, or
technically equivalent standard, or
c) directly connected to apparatus complying with the IEC 60950 series, IEC 61010-1, or a
technically equivalent standard, or
d) fed directly from cells or batteries.
Answer
No
IEC 60079-11 does not require measures to limit U where it is specified as 250 V a.c. which
m
is guaranteed by the public power supply using standards other than IEC 60079-11. Similarly,
IEC 60079-14 allows measures not compliant with IEC 60079-11 for limiting U to below
m
250 V a.c.
Therefore no assessment of the voltage supply according to IEC 60079-11 is necessary
where U is specified less than 250 V a.c. provided that one of the measures allowed by
m
IEC 60079-14:2013, 16.2.1 are applied.
rd
NOTE This does not alter the requirement of the 3 paragraph of 6.2.5 to assess, in accordance with IEC 60079-
11, any protective circuitry located in the non-hazardous area accessory.
IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSIO
...
IEC 60079-11 ®
Edition 6.0 2011-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 11: Equipment protection by intrinsic safety "i"
Atmosphères explosives –
Partie 11: Protection de l’équipement par sécurité intrinsèque «i»
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 la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.
IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: inmail@iec.ch
Web: www.iec.ch
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.
Catalogue of IEC publications: www.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
IEC Just Published: www.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
Electropedia: www.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
Customer Service Centre: www.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
Email: csc@iec.ch
Tel.: +41 22 919 02 11
Fax: +41 22 919 03 00
A propos de la CEI
La Commission Electrotechnique Internationale (CEI) 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 CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.
Catalogue des publications de la CEI: www.iec.ch/searchpub/cur_fut-f.htm
Le Catalogue en-ligne de la CEI vous permet d’effectuer des recherches en utilisant différents critères (numéro de référence,
texte, comité d’études,…). Il donne aussi des informations sur les projets et les publications retirées ou remplacées.
Just Published CEI: www.iec.ch/online_news/justpub
Restez informé sur les nouvelles publications de la CEI. Just Published détaille deux fois par mois les nouvelles
publications parues. Disponible en-ligne et aussi par email.
Electropedia: www.electropedia.org
Le premier dictionnaire en ligne au monde de termes électroniques et électriques. Il contient plus de 20 000 termes et
définitions en anglais et en français, ainsi que les termes équivalents dans les langues additionnelles. Egalement appelé
Vocabulaire Electrotechnique International en ligne.
Service Clients: www.iec.ch/webstore/custserv/custserv_entry-f.htm
Si vous désirez nous donner des commentaires sur cette publication ou si vous avez des questions, visitez le FAQ du
Service clients ou contactez-nous:
Email: csc@iec.ch
Tél.: +41 22 919 02 11
Fax: +41 22 919 03 00
IEC 60079-11 ®
Edition 6.0 2011-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 11: Equipment protection by intrinsic safety "i"
Atmosphères explosives –
Partie 11: Protection de l’équipement par sécurité intrinsèque «i»
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-88912-520-3
IEC 60079-11 ®
Edition 6.0 2011-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 11: Equipment protection by intrinsic safety "i"
Atmosphères explosives –
Partie 11: Protection de l’équipement par sécurité intrinsèque «i»
SC 31G/IEC 60079-11 (2011), sixth edition/I-SH 01
EXPLOSIVE ATMOSPHERES –
Part 11: Equipment protection by intrinsic safety "i"
INTERPRETATION SHEET 1
This interpretation sheet has been prepared by subcommittee 31G: Equipment for explosive
atmospheres – Equipment protection by intrinsic safety "i", of IEC technical committee 31.
The text of this interpretation sheet is based on the following documents:
ISH Report on voting
31G/235/ISH 31G/238/RVISH
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.
___________
Following decision No 16 of the TC 31 meeting in Melbourne in 2011, the issuing of an
th
Interpretation Sheet for IEC 60079-11:2011 (6 edition ) was requested, in order to clarify the
th
significance of the changes with respect to the 5 edition.
Question
th
What are the minor editorial, extensions, and major technical changes of the 6 edition with
th
respect to the 5 edition?
Answer
The following table shows the significance of the changes.
The significance of the changes between IEC Standard, IEC 60079-11, Edition 5, 2006-07 and
IEC 60079-11, Edition 6, 2011-06 are as listed below
October 2014 ICS 29.260.20
Significance of changes with respect to IEC 60079-11:2006
Type
Significant Changes Clause Minor and Extension Major
editorial technical
changes changes
General: Changes to remove specific clause references to General x
other IEC 60079 standards
Scope: Expansion to include Group III 1 x
Scope: Table 1 updated to include references to both 1 x
IEC 60079-0 Edition 5 and Edition 6
Normative references: Deletion of IEC 60079-27, and addition 2 x
of IEC 61158-2 and IEC 62013-1
Terms and definitions: Commonly used definitions moved to 3 x
IEC 60079-0. Energy limitation definitions moved from
IEC 60079-0.New definitions added
Spark ignition compliance: Group III ignition requirements 5.5 x
added
Temperature for small components for Group I and Group II: 5.6.2 x
Relocated to IEC 60079-0
Intrinsically safe apparatus and component temperature for 5.6.5 x
Group III
Enclosures for Group I or Group II apparatus 6.1.2 x
Apparatus complying with Annex F 6.1.2.3 c) x
Enclosures for Group III apparatus 6.1.3 x
Requirements for connections and accessories for IS 6.2.5 C1
apparatus when located in the non-hazardous area
Separation of conductive parts 6.3.2 x
Encapsulation 6.6.1 x
Encapsulation used for the exclusion of explosive 6.6.2 C2
atmospheres
Primary and secondary cells and batteries 7.4.1 x
Battery construction 7.4.2 x
Level of Protection “ic” 8.1 x
Filter capacitors 8.6.2 x
Wiring, printed circuit board tracks, and connections 8.8 c) x
FISCO apparatus 9.2 x
Handlights and caplights 9.3 x
Circuits with both inductance and capacitance 10.1.5.2 x
Electrolyte leakage test for cells and batteries 10.5.2 x
Spark ignition and surface temperature of cells and batteries 10.5.3 x
Determination of the acceptability of fuses requiring 10.6.2 x
encapsulation
Optical isolators tests 10.11 x
Marking 12.1 x
Encapsulation Annex D C2
Fieldbus intrinsically safe concept (FISCO) – Apparatus Annex G x
requirements
Ignition testing of semiconductor limiting power supply circuits Annex H x
October 2014 ICS 29.260.20
Explanation of the Types of Significant 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.
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 – Requirements for external connections, other than battery charging connections, that are designed for use
only when an explosive gas or dust atmosphere is not present, for example when in a non-hazardous area or when
a gas-free permit is in force, have been added.
C2 – The requirements for encapsulation referenced in 6.6.2 and detailed in Annex D have been changed in terms
of the thickness to the free surface and are extended related to moulding. Annex D is changed from informative to
normative.
October 2014 ICS 29.260.20
IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-11
Edition 6.0 2011-06
EXPLOSIVE ATMOSPHERES –
Part 11: Equipment protection by intrinsic safety "i"
INTERPRETATION SHEET 2
This interpretation sheet has been prepared by subcommittee 31G: Intrinsically-safe
apparatus, of IEC technical committee 31: Equipment for explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
ISH Report on voting
31G/252/ISH 31G/254/RVD
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.
___________
Interpretation of 6.2.5 – Requirements for connections and accessories for IS apparatus
when located in the non-hazardous area
Question:
Does the first NOTE of 6.2.5 imply that equipment which may be connected to non-intrinsically
safe connection facilities of intrinsically safe apparatus restricted to use in non-hazardous
area need to be assessed applying IEC 60079-11, if the value of U is less than 250 V a.c.?
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Does this furthermore apply to equipment to be connected to non-intrinsically safe connection
facilities of associated apparatus, if the value of U is less than 250 V a.c.?
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Background:
The first NOTE of 6.2.5 requires in cases were U is specified less than 250 V a.c. that this
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should not be derived from unassessed equipment. This is sometimes read as if the
requirements of IEC 60079-11 should be applied for voltage limitation to guarantee U .
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Terminological entry 3.13.13 defines that U is the maximum voltage that can be applied to
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the non intrinsically safe connection facilities of associated apparatus without invalidating the
ICS 29.260.20
– 2 – IEC 60079-11:2011/ISH2:2016
IEC 2016
type of protection. NOTE 1 of 3.13.13, as an example, explains that this may apply to
connection facilities used for charging batteries.
In IEC 60079-11 there are no measures required for limiting the voltage of non I.S. circuits to
the specified U value, except for the use of a single Zener diode protected by a fuse as an
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integral measure of an associated apparatus limiting the voltage which can appear at a
transformer (8.3) or a coupler (8.9.2).
IEC 60079-14: 2013, 16.2.1 states:
Where U marked on the associated apparatus is less than 250 V it shall be installed in
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accordance with one of the following:
a) where U does not exceed 50 V a.c. or 120 V d.c., in an SELV or PELV system, or
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b) via a safety isolating transformer complying with the requirements of IEC 61558-2-6, or
technically equivalent standard, or
c) directly connected to apparatus complying with the IEC 60950 series, IEC 61010-1, or a
technically equivalent standard, or
d) fed directly from cells or batteries.
Answer
No
IEC 60079-11 does not require measures to limit U where it is specified as 250 V a.c. which
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is guaranteed by the public power supply using standards other than IEC 60079-11. Similarly,
IEC 60079-14 allows measures not compliant with IEC 60079-11 for limiting U to below
...
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