IEC 60079-31:2008
(Main)Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure "t"
Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure "t"
IEC 60079-31:2008 is applicable to electrical equipment protected by enclosure and surface temperature limitation for use in explosive dust atmospheres. It specifies requirements for design, construction and testing of electrical equipment. This standard supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard shall take precedence. This first edition of IEC 60079-31 has been developed from the first edition of IEC 61241-1 (2004) which it now cancels and supersedes. The significant changes with respect to the previous edition are:
- Title changed to Equipment dust ignition protection by enclosure "t"
- Combination and rationalisation of practice A and B into a single practice, and some constructional requirements that may have applied to only one practice now apply to all enclosures
- Introduction of three levels of protection, "ta", "tb" and "tc"
- Defined test voltage ranges and overload conditions for thermal tests
- Introduction of a pressure test prior to the IP test
- Restrictions on power and voltage levels for level of protection "ta"
- Introduction of a variant of the IP6X test for level of protection "ta"
- Compulsory dust layer thermal test for protection level "ta" by surrounding the enclosure with dust to a depth of at least 500 mm on all available surfaces. The contents of the corrigendum of March 2009 and Interpretation Sheet 1 of February 2022 have been included in this copy.
Atmosphères explosives - Partie 31: Protection du matériel contre l'inflammation des poussières par enveloppe "t"
La CEI 60079-31:2008 est applicable au matériel électrique 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 le matériel électrique. La présente norme complète et modifie les exigences générales de la CEI 60079-0. Lorsqu'une exigence de la présente norme est en conflit avec une exigence de la CEI 60079-0, l'exigence de la présente norme prévaut. Cette première édition de la CEI 60079-31 est issue de la première édition de la CEI 61241-1 (2004) qu'elle annule et remplace. Les modifications importantes par rapport à l'édition précédente sont:
- Titre modifié pour Protection du matériel contre l'inflammation de poussières par enveloppe "t"
- Regroupement et rationalisation des méthodes A et B en une seule méthode, et de certaines exigences de constructions qui n'étaient appliquées qu'à une seule méthode et qui maintenant sont applicables à toutes les enveloppes
- Introduction des trois niveaux de protection, "ta", "tb" et "tc"
- Les gammes de tensions d'essai et les conditions de surcharge pour les essais thermiques ont été définies
- Introduction d'un essai de pression avant l'essai IP
- Réduction des niveaux de puissance et de tension pour le niveau de protection "ta"
- Introduction d'une variante de l'essai IP6X pour le niveau de protection "ta"
- Essai thermique de couche de poussière obligatoire pour le niveau de protection "ta" par enfouissement de l'enveloppe dans de la poussière dont la couche a une épaisseur d'au moins 500 mm sur toutes les surfaces accessibles. Le contenu du corrigendum de mars 2009 a été pris en considération dans cet exemplaire.
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Standards Content (Sample)
IEC 60079-31
Edition 1.0 2008-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 31: Equipment dust ignition protection by enclosure “t”
Atmosphères explosives –
Partie 31: Protection du matériel contre l’inflammation des poussières par
enveloppe «t»
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IEC 60079-31
Edition 1.0 2008-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 31: Equipment dust ignition protection by enclosure “t”
Atmosphères explosives –
Partie 31: Protection du matériel contre l’inflammation des poussières par
enveloppe «t»
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
L
CODE PRIX
ICS 29.260.20 ISBN 978-2-88910-050-7
© IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-31
Edition 1.0 2008-11
EXPLOSIVE ATMOSPHERES –
Part 31: Equipment dust ignition protection by enclosure "t"
INTERPRETATION SHEET 1
This interpretation sheet has been prepared by IEC technical committee 31: Equipment for
explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
DISH Report on voting
31/1605/DISH 31/1616/RVDISH
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.
___________
protection by enclosure "t"
Question 1:
The requirements given in 5.2.2 of IEC 60079-31:2008 (Edition 1) permit threaded entries for
dust protected enclosures to be tapered threads or parallel threads with not less than five
threads, with a minimum tolerance of medium or fine according to ISO 956-1 and ISO 965-3.
Does the description of threads include other thread forms such as ISO 228-1 threads (these
threads are commonly referred to as BSPP or Type G threads and BSPT or Type R threads)?
Answer 1:
No, only metric and NPT threaded entries are permitted for enclosures having equipment dust
ignition protection by enclosure.
NOTE It has been determined that some sizes of Type G and NPT threads will engage but will result in a mismatched
thread engagement. The intention of the restriction to only metric and NPT regarding threaded entries for dust ignition
protection by enclosure is to minimize the risk of mismatch of thread forms in enclosure entries.
ICS 29.260.20
– 2 – IEC 60079-31:2008/ISH1:2022
© IEC 2022
Question 2:
Where a thread adapter is fitted and assessed as a factory-assembled part of the dust protected
enclosure, what are the permitted thread forms?
Answer 2:
A thread adapter may use thread forms other than metric and NPT, whether as an Ex Equipment
thread adapter or as a thread adapter fitted and assessed as a factory-assembled part of the
dust protected enclosure.
Question 3:
Can a blanking element be installed in a thread adapter which is fitted and assessed as a
factory-assembled part of the dust protected enclosure?
Answer 3:
Yes, a blanking element can be installed in a thread adapter which is fitted and assessed as a
factory-assembled part of the dust protected enclosure.
Question 4:
What is the required marking when a thread adapter is fitted and assessed as a factory
assembled part of the dust protected enclosure?
Answer 4:
Clause 16.2 of IEC 60079-0 (Editions 6 and 7) requires identification of the specific thread type
and size of threaded entries. In the case where the thread adapter is fitted and assessed as a
factory-assembled part of the dust protected enclosure, the requirement for identification
applies to the thread form of the adapter for the field wiring connection.
– 2 – 60079-31 © IEC:2008
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Terms and definitions .6
4 Level of protection.6
4.1 General .6
4.2 Additional requirements for level of protection “ta”.6
4.2.1 Thermal protection .6
5 Construction .7
5.1 Joints .7
5.1.1 General .7
5.1.2 Gaskets and seals .7
5.1.3 Cemented joints .8
5.1.4 Operating rods, spindles and shafts.8
5.1.5 Windows.8
5.2 Cable glands and conduit entries.8
5.2.1 Cable glands .8
5.2.2 Conduit entries .8
6 Verification and tests .9
6.1 Type tests .9
6.1.1 Type tests for dust exclusion by enclosures.9
6.1.2 Thermal tests .9
6.1.3 Pressure test .10
6.2 Routine tests .10
7 Marking .10
Bibliography.11
Table 1 – Ingress protection .9
Table 2 – Conditions for the determination of maximum surface temperature.9
60079-31 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
__________
EXPLOSIVE ATMOSPHERES –
Part 31: Equipment dust ignition protection by enclosure "t"
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