This part of IEC 60079 specifies the general requirements for construction, testing and marking of Ex 413 Equipment and Ex Components intended for use in or associated with explosive atmospheres. 414
The standard atmospheric conditions (relating to the explosion characteristics of the atmosphere) under which it may be assumed that Ex 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 a volume fraction of 21 %.
This part of IEC 60079 and other documents supplementing this document specify additional test requirements for Ex Equipment operating outside the standard temperature range, but in some cases, further additional consideration and additional testing is required for Ex Equipment operating outside the standard atmospheric pressure range and standard oxygen content. Such additional testing is particularly relevant with respect to Types of Protection that depend on quenching of a flame such as âflameproof enclosures âdââ (IEC 60079-1) or limitation of energy, âintrinsic safety âiââ (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 Ex 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 many items of Ex Equipment and that to manufacture all Ex 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 document result from an ignition hazard assessment made on equipment. The ignition sources taken into account are those found associated with this type of equipment, such as hot surfaces, electromagnetic radiation, mechanically generated sparks, mechanical impacts resulting in thermite reactions, electrical arcing and static electric discharge in normal industrial environments.
NOTE 3 Where an explosive gas atmosphere and a combustible dust atmosphere are, or can be, present at the same time, the simultaneous presence of both often warrants additional protective measures. Additional guidance on the use of Ex Equipment in hybrid mixtures (mixture of a flammable gas or vapour with a combustible dust or combustible flyings) is given in IEC 60079-14.
NOTE 4 Any short term thermal excursions that occur as a result of electrical current excursions above normal rated currents, such as those that occur during the starting of motors, are not considered to create a significant risk of ignition of an explosive atmosphere due to the relatively short duration of the event and the convection that occurs during the event.
IEC 60079 does not specify requirements for safety, other than those directly related to the reduction (mitigation) of ignition hazards.
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 document.
NOTE 5 Although outside the scope of this document, such equipment would typically be subjected to a ignition hazard assessment that identifies and lists all of the potential sources of ignition by the equipment and the measures to be applied to prevent them becoming effective. See ISO/IEC 80079-36.
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