IEC 60079, Explosive Atmospheres, Hazardous Area Equipment.
IEC 60079 is the international standard series governing electrical equipment for use in explosive atmospheres, Ex equipment. The standard defines hazardous area zone classification, Zone 0, Zone 1, Zone 2 for gas. Zone 20, Zone 21, Zone 22 for dust, the protection methods for electrical equipment, flameproof Ex d, intrinsically safe Ex i, increased safety Ex e, pressurized Ex p, encapsulation Ex m, oil immersion Ex o, powder filling Ex q, type of protection n Ex n, special Ex s, and the marking convention that identifies the protection method, zone, and gas group. The North American equivalent is NEC Class, Division, Group classification.
What IEC 60079, Explosive Atmospheres, Hazardous Area Equipment means.
IEC 60079 is structured as a series of parts. Part 0 covers general requirements. Parts 1, 7, 11, 15, 18, 26 cover specific protection methods. Part 10 covers area classification. Part 14 covers electrical installation in hazardous areas. Part 17 covers inspection and maintenance. Operating companies and EPC contractors typically reference Part 10, area classification report, Part 14, installation, and Part 17, maintenance and inspection as the lifecycle anchor for hazardous-area electrical work. The North American Class, Division, Group system, NEC Article 500 is technically equivalent at the design level but uses different terminology. NEC Article 505 adopts the IEC zone system for new installations.
How does the IEC zone classification work.
Zone 0 is an area where an explosive gas atmosphere is present continuously or for long periods. Equipment must be intrinsically safe Ex ia or specially certified. Zone 1 is an area where an explosive gas atmosphere is likely to occur in normal operation. Equipment in Ex d, Ex e, Ex ib, Ex p, Ex m, Ex o, Ex q is acceptable. Zone 2 is an area where an explosive gas atmosphere is not likely to occur in normal operation and, if it does, will exist only for a short period. Ex n equipment plus all higher zone categories are acceptable. The dust zones, 20, 21, 22 parallel the gas zones for combustible dust environments.
What do the gas groups, IIA, IIB, IIC mean.
Gas group IIA covers propane-class gases, least restrictive. IIB covers ethylene-class gases, more restrictive. IIC covers hydrogen and acetylene, most restrictive. Each higher group requires tighter flame-path gaps in Ex d equipment, lower maximum surface temperatures, and more restrictive intrinsic-safety energy limits. Equipment certified for IIC is acceptable in IIA and IIB areas. Equipment certified for IIA only is not acceptable in IIB or IIC areas. The gas group of the area drives equipment selection.
What is the marking convention.
Ex equipment carries a marking like Ex db IIC T4 Gb. 'Ex' identifies the equipment as explosion-protected. 'd' identifies the protection method, flameproof. The lowercase letter after 'd' identifies the equipment protection level, a, b, c, corresponding to Zone 0, 1, 2 suitability. 'IIC' identifies the gas group. 'T4' identifies the temperature class, maximum surface temperature 135°C. 'Gb' identifies the equipment protection level for gas, a is highest, c is lowest. Equivalent dust marking uses 't' for type of protection 't', enclosure, 'IIIA, B, C' for dust groups, 'T' followed by Celsius temperature, and 'Da, Db, Dc' for dust EPL.
Common questions
What is the difference between IEC zones and NEC Class, Division.
What is intrinsic safety, Ex i.
What is ATEX vs. IECEx.
Does IEC 60079 apply to mechanical equipment.
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