EN IEC 60079-31:2024
(Main)Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure "t"
Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure "t"
IEC 60079-31:2022 is available as IEC 60079-31:2022 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 60079-31:2022 is applicable to equipment protected by enclosure and surface temperature limitation for use in explosive dust atmospheres. It specifies requirements for design, construction and testing of Ex Equipment and Ex Components. 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 document does not apply to dusts of explosives, which do not require atmospheric oxygen for combustion, or to pyrophoric substances. This document does not apply to Ex Equipment or Ex Components intended for use in underground parts of mines as well as those parts of surface installations of such mines endangered by firedamp and/or combustible dust. This document does not take account of any risk due to an emission of flammable or toxic gas from the dust. This third edition cancels and replaces the second edition published in 2013. This edition constitutes a technical revision. Main significant changes from the previous edition are: 1) Document has been restructured from edition 2 2) Fault current rating of interrupting contacts in clauses 4.3.1 and 4.4.1, major change type C1 3) Cells and batteries in clauses 4.3.5.1 and 4.4.5.1, major change type C2 4) Overload or malfunction condition for the determination of temperature class for "tb" converter fed rotating electric machines, major change type C3 5) Additional requirements for entry devices with dust ignition protection by enclosure "t", major change type C4 Information about the background of ‘Major Technical Changes’ C1 – Ex Equipment having Level of Protection "ta" shall be rated for connection to a circuit with a prospective short circuit current of not greater than 1.5 kA. For Ex Equipment having Level of Protection "tb" or "tc" which is intended for mains connection and intended to interrupt fault current above 10kA, the equipment shall have a rated maximum short circuit withstand current, be tested according to 6.1.1.1, and be marked according to Clause 7. C2 – For Ex Equipment having Level of Protection "ta" which contains a cell or battery, only a sealed cell or battery shall be used. For Ex Equipment having Level of Protection "tb" and "tc" where there are sparking contacts or hot surfaces, and which contains a cell or battery, only a sealed cell or battery shall be used. C3 – Table 2 now includes malfunction conditions for temperature class determination of Level of Protection "tb" converter-fed electric machines. C4 – Annex A added for entry devices with Type of Protection "t" including cable transit devices.
Explosionsgefährdete Bereiche - Teil 31: Geräte-Staubexplosionsschutz durch Gehäuse „t“
Atmosphères explosives - Partie 31: Protection contre l’inflammation de poussières par enveloppe "t" relative à l’appareil
IEC 60079-31:2022 est disponible sous forme de IEC 60079-31:2022 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.L'IEC 60079-31:2022 est applicable à l’appareil protégé par enveloppe et limitation de la température de surface, pour une utilisation en atmosphère de poussière explosive. Elle spécifie les exigences de conception, de construction et d'essai pour l’Appareil Ex et les Composants Ex. Le présent document complète et modifie les exigences générales de l’IEC 60079-0. Lorsqu'une exigence du présent document est en contradiction avec une exigence de l’IEC 60079-0, l’exigence du présent document prévaut. Le présent document ne s’applique pas aux poussières d’explosifs dont la combustion n’exige pas l’oxygène de l’air, ni aux substances pyrotechniques. Le présent document ne s’applique ni à l’Appareil Ex ni aux Composants Ex destinés à une utilisation dans les parties souterraines des mines, ni aux parties des installations de surface des mines où il existe des risques de grisou et/ou de poussières combustibles. Le présent document ne prend en compte aucun risque résultant d’une émission de gaz inflammable ou toxique provenant de la poussière.
Eksplozivne atmosfere - 31. del: Zaščita opreme pred vžigom gorljivega prahu z ohišjem "t" (IEC 60079-31:2022 + COR1:2023)
Ta del standarda IEC 60079 se uporablja za opremo, zaščiteno z ohišjem in omejitvijo površinske temperature za uporabo v eksplozivnih prašnih atmosferah. Določa zahteve za načrtovanje, izdelavo in preskušanje opreme ter sestavnih delov s protieksplozijsko zaščito.
Ta dokument dopolnjuje in spreminja splošne zahteve standarda IEC 60079-0. Kadar je zahteva iz tega dokumenta v nasprotju z zahtevo iz standarda IEC 60079-0, ima prednost zahteva iz tega dokumenta.
Ta dokument se ne uporablja za prah eksplozivov, ki za zgorevanje ne potrebujejo atmosferskega kisika, ali za piroforne snovi.
Ta dokument se ne uporablja za opremo ali sestavne dele s protieksplozijsko zaščito, ki so namenjeni uporabi v podzemnih delih rudnikov in delih površinskih instalacij takih rudnikov, ki jih ogroža jamski eksplozivni plin in/ali vnetljiv prah.
Ta dokument ne obravnava nobene nevarnosti zaradi emisije vnetljivega ali strupenega plina iz prahu.
Ta dokument ne vključuje zahtev za opremo s protieksplozijsko zaščito, ki se uporablja v območjih z atmosfero, ki lahko vsebuje vnetljiv prah in eksplozivni plin (hkrati ali ločeno). Zahteve za atmosfere z vnetljivim plinom je mogoče najti v drugih delih skupine standardov IEC 60079. Smernice glede opreme s protieksplozijsko zaščito, ki jo je treba uporabljati v atmosferah, v katerih sta sočasno prisotna vnetljiv prah in eksplozivni plin (»hibridne mešanice«), je mogoče najti v standardu IEC 60079-14.
Če mora oprema s protieksplozijsko zaščito izpolnjevati druge okoljske pogoje, na primer zaščito pred vdorom vode in odpornost proti koroziji, so morda potrebni dodatni ukrepi, ki ne vplivajo negativno na celovitost ohišja.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-junij-2024
Eksplozivne atmosfere - 31. del: Zaščita opreme pred vžigom gorljivega prahu z
ohišjem "t" (IEC 60079-31:2022 + COR1:2023)
Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure "t"
(IEC 60079-31:2022 + COR1:2023)
Explosionsgefährdete Bereiche - Teil 31: Geräte-Staubexplosionsschutz durch Gehäuse
"t" (IEC 60079-31:2022 + COR1:2023)
Atmosphères explosives - Partie 31: Protection contre l’inflammation de poussières par
enveloppe “t” relative au matériel (IEC 60079-31:2022 + COR1:2023)
Ta slovenski standard je istoveten z: EN IEC 60079-31:2024
ICS:
29.260.20 Električni aparati za Electrical apparatus for
eksplozivna ozračja explosive atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN IEC 60079-31
NORME EUROPÉENNE
EUROPÄISCHE NORM March 2024
ICS 29.260.20 Supersedes EN 60079-31:2014
English Version
Explosive atmospheres - Part 31: Equipment dust ignition
protection by enclosure "t"
(IEC 60079-31:2022 + COR1:2023)
Atmosphères explosives - Partie 31: Protection contre Explosionsgefährdete Bereiche - Teil 31: Geräte-
l'inflammation de poussières par enveloppe "t" relative à Staubexplosionsschutz durch Gehäuse "t"
l'appareil (IEC 60079-31:2022 + COR1:2023)
(IEC 60079-31:2022 + COR1:2023)
This European Standard was approved by CENELEC on 2023-12-13. 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60079-31:2024 E
European foreword
The text of document 31/1595/FDIS, future edition 3 of IEC 60079-31+COR1, prepared by IEC/TC 31
"Equipment for explosive atmospheres" was submitted to the IEC-CENELEC parallel vote and
approved by CENELEC as EN IEC 60079-31:2024.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2024-09-13
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2026-12-13
document have to be withdrawn
This document supersedes EN 60079-31:2014 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60079-31:2022+COR1:2023 was approved by CENELEC
as a European Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60079-14 NOTE Approved as EN 60079-14
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1 Where 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.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60079-0 - Explosive atmospheres - Part 0: Equipment - EN IEC 60079-0 -
General requirements
IEC 60127 series Miniature fuses - series
IEC 60269 series Low-voltage fuses EN 60269 series
IEC 60691 - Thermal-links - Requirements and application EN IEC 60691 -
guide
IEC 60529 - Degrees of protection provided by enclosures - -
(IP Code)
IEC 60034-5 - Rotating electrical machines - Part 5: Degrees EN IEC 60034-5 -
of protection provided by the integral design of
rotating electrical machines (IP code) -
Classification
ISO 965-1 - ISO general purpose metric screw threads - - -
Tolerances - Part 1: Principles and basic data
ANSI/ASME - Pipe threads, general purpose (inch) - -
B1.20.1
ANSI/UL 248 series Standard for low-voltage fuses - series
IEC 60079-31 ®
Edition 3.0 2022-01
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 à l’appareil
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-4591-0
– 2 – IEC 60079-31:2022 © IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 General . 10
4.1 Levels of protection. 10
4.2 Equipment groups and ingress protection . 10
4.3 Requirements for Ex Equipment with Level of Protection "ta" . 11
4.3.1 Fault current . 11
4.3.2 Maximum surface temperature . 11
4.3.3 Dust exclusion . 11
4.3.4 Protective Devices . 11
4.3.5 Supplementary internal enclosure . 12
4.3.6 Cells and batteries . 12
4.4 Requirements for Ex Equipment with Level of Protection "tb" and "tc" . 12
4.4.1 Fault current . 12
4.4.2 Maximum surface temperature . 13
4.4.3 Dust exclusion . 13
4.4.4 Thermal protection . 13
4.4.5 Cells and batteries . 13
4.4.6 External plug and socket connections for field wiring connection . 14
5 Construction . 14
5.1 Joints . 14
5.1.1 General . 14
5.1.2 Threaded joints . 14
5.1.3 Gaskets and seals . 14
5.1.4 Cemented joints. 15
5.1.5 Operating rods, spindles and shafts . 15
5.1.6 Windows . 15
5.2 Cable glands, cable transit devices and conduit sealing devices . 15
5.3 Entries . 15
5.3.1 Plain entries . 15
5.3.2 Threaded entries . 15
6 Verification and tests . 16
6.1 Type tests . 16
6.1.1 Type tests for dust exclusion by enclosures . 16
6.1.2 Tests to determine maximum surface temperature . 17
6.2 Routine tests . 18
7 Marking . 18
Annex A (normative) Supplementary requirements for entry devices . 19
A.1 General . 19
A.2 Construction requirements . 19
A.2.1 Cable glands, cable transit devices and conduit sealing devices . 19
A.2.2 Blanking elements and thread adapters . 19
A.3 Type tests . 19
IEC 60079-31:2022 © IEC 2022 – 3 –
A.3.1 Cable glands, cable transit devices and conduit sealing devices . 19
A.3.2 Blanking elements and thread adapters . 19
A.4 Marking . 19
Bibliography . 20
Table 1 – Level of Protection, equipment group and ingress protection (IP) relationship . 11
Table 2 – Overload or malfunction conditions for Level of Protection "tb" . 17
– 4 – IEC 60079-31:2022 © IEC 2022
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 third edition cancels and replaces the second edition published in 2013. This edition
constitutes a technical revision.
IEC 60079-31:2022 © IEC 2022 – 5 –
The significance of changes between IEC Standard, IEC 60079-31, Edition 3.0 and
IEC 60079-31, Edition 2.0, are as listed below:
Type
Changes Clause Minor and Extension Major technical
editorial changes
changes
Document has been restructured from edition 2 Numerous X
Withstand of prospective short-circuit current 4.3.1 X
Fault current rating of interrupting contacts rated 4.4.1 and C1
greater than 10 kA for mains connected circuits 6.1.1.1
Thermal protective device can include a thermal 4.4.4.1 X
protective circuit with an appropriate sensor.
Cells and batteries 4.3.6 and C2
4.4.5
Joints employing parallel threads with an additional 5.1.2 X
seal or gasket are permitted to have less than five
threads.
Gasket joints that interlock (not a butt joint) and are
5.1.3 X
designed such that under the intended compression
no gap between the pieces exist so that an
uninterrupted periphery is formed, these joints do not
need to be permanently joined.
Overload or malfunction condition for the Table 2 C3
determination of temperature class for "tb" converter
fed rotating electric machines
Additional requirements for entry devices with dust Annex A C4
ignition protection by enclosure "t"
Thermal tests are relocated to IEC 60079-0. Formerly A1
6.1.2
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 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.
– 6 – IEC 60079-31:2022 © IEC 2022
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 – For Ex Equipment having Level of Protection "tb" or "tc" which is intended for mains
connection and intended to interrupt fault current above 10kA is tested according to 6.1.1.1,
and is marked according to Clause 7.
C2 – For Ex Equipment having Level of Protection "ta" only sealed primary cells or batteries
shall be used. A control device shall be provided to prevent overheating of the cell or battery
during normal operation, expected malfunctions, or rare malfunctions. The control device may
also be considered as a thermal protective device or overcurrent protective device. For Ex
Equipment having Level of Protection "tb" and "tc" only sealed cells or batteries shall be used.
A control device shall be provided to prevent overheating of the cell or battery during normal
operation or expected malfunctions (“tb”) or during normal operation (“tc”). The control device
may also be considered as a thermal protective device or overcurrent protective device.
C3 – Table 2 now includes malfunction conditions for temperature class determination of Level
of Protection "tb" converter-fed electric machines.
C4 – Annex A added for entry devices with Type of Protection "t" including cable transit devices.
A1 – Thermal tests formerly located in 6.1.2 are relocated to IEC 60079-0 for the 2017 and later
editions.
The text of this International Standard is based on the following documents:
Draft Report on voting
31/1595/FDIS 31/1606/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
IEC 60079-31:2022 © IEC 2022 – 7 –
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.
The contents of the corrigendum 1 (2023-10) have been included in this copy.
– 8 – IEC 60079-31:2022 © IEC 2022
INTRODUCTION
The International Electrotechnical Commission (IEC) draws attention to the fact that it is claimed
that compliance with this document may involve the use of a patent. IEC takes no position
concerning the evidence, validity, and scope of this patent right.
The holder of this patent right has assured IEC that s/he is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world.
In this respect, the statement of the holder of this patent right is registered with IEC. Information
may be obtained from the patent database available at http://patents.iec.ch.
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights other than those in the patent database. IEC shall not be held
responsible for identifying any or all such patent rights.
IEC 60079-31:2022 © IEC 2022 – 9 –
EXPLOSIVE ATMOSPHERES –
Part 31: Equipment dust ignition protection by enclosure "t"
1 Scope
This part of IEC 60079 is applicable to equipment protected by enclosure and surface
temperature limitation for use in explosive dust atmospheres. It specifies requirements for
design, construction and testing of Ex Equipment and Ex Components.
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 document does not apply to dusts of explosives, which do not require atmospheric oxygen
for combustion, or to pyrophoric substances.
This document does not apply to Ex Equipment or Ex Components intended for use in
underground parts of mines as well as those parts of surface installations of such mines
endangered by firedamp and/or combustible dust.
This document does not take account of any hazard due to an emission of flammable or toxic
gas from the dust.
This document does not contain requirements for Ex Equipment used in areas where both
combustible dust and explosive gas atmospheres can occur, whether simultaneously or
separately. Requirements for explosive gas atmospheres can be found in other parts of the
IEC 60079 series. Guidance on Ex Equipment to be used where combustible dust and explosive
gas atmospheres occur simultaneously ("hybrid mixtures") can be found in IEC 60079-14.
Where the Ex Equipment has to meet other environmental conditions, for example, protection
against ingress of water and resistance to corrosion, additional measures which do not
adversely affect the integrity of the enclosure can be necessary.
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 60127 (all parts), Miniature fuses
IEC 60269 (all parts), Low-voltage fuses
IEC 60691, Thermal-links – Requirements and application guide
IEC 60529, Degrees of protection provided by enclosures (IP Code)
– 10 – IEC 60079-31:2022 © IEC 2022
IEC 60034-5, Rotating electrical machines – Part 5: Degrees of protection provided by the
integral design of rotating electrical machines (IP code) – Classification
ISO 965-1, ISO general-purpose metric screw threads – Tolerances – Part 1: Principles and
basic data
ANSI/ASME B1.20.1, Pipe threads, general purpose (inch)
ANSI/UL 248 (all parts), Standard for Low-Voltage Fuses
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
3.1
dust ignition protection by enclosure "t"
Type of Protection for explosive dust atmospheres where equipment is provided with an
enclosure providing dust ingress protection and a means to limit surface temperatures
4 General
4.1 Levels of protection
Type of Protection "t" is divided into three Levels of Protection based on the risk of the Ex
Equipment and Ex Components becoming an ignition source in an explosive dust atmosphere.
Ex Equipment and Ex Components with Type of Protection "t" shall be one of the following:
• Level of Protection "ta" for EPL "Da";
• Level of Protection "tb" for EPL "Db";
• Level of Protection "tc" for EPL "Dc".
The general requirements of Clause 4, the construction requirements of Clause 5, and the
marking requirements of Clause 7, apply to all Ex "t" Equipment and Ex "t" Components.
Failure modes as defined in the industrial standard for particular internal components affecting
the temperatures of the equipment shall be taken into account when considering applicable
malfunctions.
When a resistor is used for current limiting, it shall not be considered to fail as a short circuit if
it is of metal film or of wire wound construction. The resistor shall be r
...
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