MT 60079-31 - TC 31/MT 60079-31

IEC 60079-31:2013 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 and Ex Components. 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 takes precedence. This standard does not apply to dusts of explosives, which do not require atmospheric oxygen for combustion, or to pyrophoric substances. This standard does not apply to electrical 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 standard does not take account of any risk due to an emission of flammable or toxic gas from the dust. Consideration of additional protective measures is required where the application of electrical equipment is in atmospheres, which can contain combustible dust as well as explosive gas, whether simultaneously or separately. Where the electrical equipment has to meet other environmental conditions, for example, protection against ingress of water and resistance to corrosion, additional measures can be necessary. The measures used should not adversely affect the integrity of the enclosure. This second edition cancels and replaces the first edition published in 2008. This edition constitutes a technical revision. The major technical changes include:
- The marked maximum surface temperature shall be measured on the external surfaces of the enclosure and the surfaces of the internal components for equipment with types of protection "ta";
- Additional protection for arcing and sparking parts for "ta";
- Test for internal enclosure for level "ta" added. Keywords: explosive dust atmospheres
The contents of the Interpretation Sheet 1 of February 2022 have been included in this copy.
This publication is to be read in conjunction with IEC 60079-0:2011.

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.