IEC 60079-31:2013

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.

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. The contents of the corrigendum of October 2023 have been included in this copy.