IEC 60079-31 pdf download – Explosive atmospheres – Part 31: Equipment dust ignition protection by enclosure “t”
This part of lEC 60079 is applicable to electrical equipment protected by enclosure andsurface temperature limitation for use in explosive dust’atmospheres. lt specifiesrequirements for design, construction and testing of electrical equipment.
This standard supplements and modifies the general requirements of lEC 60079-0. Where arequirement of this standard conflicts with a requirement of lEC 60079-0, the requirement ofthis standard shall take precedence.
This standard does not apply to dusts of explosives, which do not require atmospheric oxygenfor combustion,or to pyrophoric substances.
This standard does not apply to electrical equipment intended for use in underground parts ofmines as well as those parts of surface installations of such mines endangered by firedampand/or combustible dust.
This standard does not take account of any risk due to an emission of flammable or toxic gasfrom the dust.
NOTE 1 The application of electrical equipment in atmospheres, which may contain combustible dust as well asexplosive gas,whether simultaneously or separately, may require additional protective measures.
NOTE 2 Where the equipment has to meet other environmental conditions，for example，protection againstingress of water and resistance to corrosion,additional methods of protection may be necessary. The method usedshould not adversely affect the integrity of the enclosure.
Normative references
The following referenced documents are indispensable for the application of this document.For dated references, only the edition cited applies. For undated references, the latest editionof the referenced document (including any amendments) applies.
IEC 60034-1，Rotating electrical machines – Part 1: Rating and performance
IEC 60079-0，Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-7,Explosive atmospheres – Part 7: Equipment protection by increased safety “e”
IEC 60127 series，Miniature fuses
IEC 60691，Thermal-links – Requirements and application guide
Iso 965-1,IS0 general-purpose metric screw threads – Tolerances – Part 1 : Principles andbasic data
IsO 965-3,ISO general-purpose metric screw threads – Tolerances – Part 3: Deviation forconstructional screw threads
3Terms and definitions
For the purposes of this document, the terms and definitions given in lEC 60079-0,as well asthe following definitions, apply.
NOTE Additional definitions applicable to explosive atmospheres can be found in lEC 60050-426[1]1.3.1
dust ignition protection by enclosure ” t”
type of protection for explosive dust atmospheres where electrical equipment is provided withan enclosure providing dust ingress protection and a means to limit surface temperatures
3.2
joint
place where the corresponding surfaces of two parts of an enclosure,or the conjunction ofenclosures, come together
3.3
gasket
a compressible element provided in a joint to provide protection against the ingress of dust
4Level of protection
Type of protection “t” is divided into three levels of protection，”ta”,“tb”and “tc”.For eachlevel of protection，an equipment protection level (EPL) has been assigned based on the riskof the equipment becoming an ignition source in a hazardous atmosphere.
4.1 General
Equipment with dust ignition protection by enclosure “t” shall be either.level of protection ta (EPL“Da”), or
-level of protection tb (EPL”Db”).or-level of protection tc(EPL “Dc””).
The requirements of this standard shall apply to all levels of protection”t” unless otherwisestated.
4.2Additional requirements for level of protection ” ta”
For level of protection “ta”,the requirements of lEC 60079-31 shall apply，in addition to thefollowing. The power supply to level of protection“ta”equipment shall be rated for aprospective short circuit current of not more than 10 kA.
4.2.1 Thermal protection
4.2.1.1General
Where the equipment is capable of exceeding the maximum surface temperature as a resultof an abnormal operating condition,a protective device shall be provided either external tothe equipment or directly integrated into the equipment.The protective device shall becapable of interrupting the maximum current of the circuit in which it is installed. Where theequipment contains a cell or battery and a control device is provided to prevent overheating ofthe cell or battery, the control device can also be considered as a protective device,providingit also protects the complete equipment from exceeding the maximum surface temperature,
IEC 60079-31 pdf download – Explosive atmospheres – Part 31: Equipment dust ignition protection by enclosure “t”
