Explosive atmospheres - Equipment. General requirements

Explosive atmospheres - Equipment. General requirements

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1   Scope

This part of IEC 60079 specifies the general requirements for construction, testing and marking of electrical equipment and Ex Components intended for use in explosive atmospheres.
The standard atmospheric conditions (relating to the explosion characteristics of the atmosphere) under which it may be assumed that electrical equipment can be operated are:
  • • temperature −20 °C to +60 °C;
  • • pressure 80 kPa (0,8 bar) to 110 kPa (1,1 bar); and
  • • air with normal oxygen content, typically 21 % v/v.
This standard and other standards supplementing this standard specify additional test requirements for equipment operating outside the standard temperature range, but further additional consideration and additional testing may be required for equipment operating outside the standard atmospheric pressure range and standard oxygen content, particularly with respect to types of protection that depend on quenching of a flame such as ‘flameproof enclosure “d”’ (IEC 60079‑1) or limitation of energy, ‘intrinsic safety “i”’ (IEC 60079‑11).

NOTE 1 Although the standard atmospheric conditions above give a temperature range for the atmosphere of - 20 °C to +60 °C, the normal ambient temperature range for the equipment is −20 °C to +40 °C, unless otherwise specified and marked. See 5.1.1. It is considered that −20 °C to +40 °C is appropriate for most equipment and that to manufacture all equipment to be suitable for a standard atmosphere upper ambient temperature of +60 °C would place unnecessary design constraints.

NOTE 2 Requirements given in this standard result from an ignition hazard assessment made on electrical equipment. The ignition sources taken into account are those found associated with this type of equipment, such as hot surfaces, mechanically generated sparks, mechanical impacts resulting in thermite reactions, electrical arcing and static electric discharge in normal industrial environments.

NOTE 3 It is acknowledged that, with developments in technology, it may be possible to achieve the objectives of the IEC 60079 series of standards in respect of explosion prevention by methods that are not yet fully defined. Where a manufacturer wishes to take advantage of such developments, this International Standard, as well as other standards in the IEC 60079 series, may be applied in part. It is intended that the manufacturer prepare documentation that clearly defines how the IEC 60079 series of standards has been applied, together with a full explanation of the additional techniques employed. The designation “Ex s” has been reserved to indicate special protection. A standard for special protection “s”, IEC 60079‑33, is in preparation.

NOTE 4 Where an explosive gas atmosphere and a combustible dust atmosphere are, or may be, present at the same time, the simultaneous presence of both should be considered and may require additional protective measures.

This standard does not specify requirements for safety, other than those directly related to the explosion risk. Ignition sources like adiabatic compression, shock waves, exothermic chemical reaction, self ignition of dust, naked flames and hot gases/liquids, are not addressed by this standard.

NOTE 5 Such equipment should be subjected to a hazard analysis that identifies and lists all of the potential sources of ignition by the electrical equipment and the measures to be applied to prevent them becoming effective.

This standard is supplemented or modified by the following standards concerning specific types of protection:
  • — IEC 60079‑1: Gas – Flameproof enclosures "d";
  • — IEC 60079‑2: Gas – Pressurized enclosures "p";
  • — IEC 60079‑5: Gas – Powder filling "q";
  • — IEC 60079‑6: Gas – Oil immersion "o";
  • — IEC 60079‑7: Gas – Increased safety "e";
  • — IEC 60079‑11: Gas – Intrinsic safety "i";
  • — IEC 60079‑15: Gas – Type of protection “n”;
  • — IEC 60079‑18: Gas and dust – Encapsulation "m";
  • — IEC 60079‑31: Dust – Protection by enclosure “t”
  • — IEC 61241‑4: Dust – Pressurization “pD”.

NOTE 6 Additional information on types of protection for non-electrical equipment can be found in ISO/IEC 80079‑36 (to be published).

This standard is supplemented or modified by the following equipment standards:
IEC 60079‑13: Explosive atmospheres – Part 13: Equipment protection by pressurized room“p”
IEC 60079‑25: Explosive atmospheres – Part 25: Intrinsically safe electrical systems
IEC 60079‑26: Explosive atmospheres – Part 26: Equipment with equipment protection level (EPL) Ga
IEC 60079‑28: Explosive atmospheres – Part 28: Protection of equipment and transmission systems using optical radiation
IEC 62013‑1: Caplights for use in mines susceptible to firedamp – Part 1: General requirements – Construction and testing in relation to the risk of explosion
IEC 60079‑30‑1: Explosive atmospheres – Part 30-1: Electrical resistance trace heating – General and testing requirements.
This standard with the additional standards mentioned above, are not applicable to the construction of
  • • electromedical apparatus,
  • • shot-firing exploders,
  • • test devices for exploders, and
  • • shot-firing circuits.