Electrical apparatus for explosive gas atmospheres – Part 26: Construction, test and marking of Group II Zone 0 electrical apparatus
|Publication Date:||1 March 2004|
|ICS Code (Electrical apparatus for explosive atmospheres):||29.260.20|
This part of IEC 60079 specifies the particular requirements for construction, test and marking for electrical apparatus of Group II intended for use in Zone 0 as defined in IEC 60079-10.
This electrical apparatus, within the operational parameters specified by the manufacturer, ensures a very high level of protection that includes rare faults related to the apparatus or two faults occurring independently of each other.
NOTE 1 A malfunction may result from a failure of the component parts of the electrical apparatus or from anticipated externally applied influences. Two independent malfunctions which may occur more frequently and which, separately, would not create an ignition hazard but which, in combination, could create a potential ignition hazard, should be regarded as occurring together to form a rare fault.
This electrical apparatus is intended for use in Zone 0 hazardous areas, in which explosive gas atmospheres caused by mixtures of air and gases, vapours or mists under normal atmospheric conditions are present continuously, for long periods or frequently.
This standard also applies to apparatus mounted across the boundary between Zone 0 and Zone 1.
EXAMPLE: In the wall of a storage vessel.
This standard also applies to apparatus installed outside Zone 0, but electrically connected to apparatus inside Zone 0 (associated apparatus).
This standard supplements the general requirements in IEC 60079-0 and the requirements of the standardized types of protection, in accordance with the IEC 60079 series, to adapt the level of safety provided by those standards to the very high level of risk in Zone 0.
NOTE 2 In designing apparatus for operation in explosive gas atmospheres under conditions other than the atmospheric conditions given in IEC 60079-0, this standard may be used as a guide. However, additional testing is recommended related specifically to the intended conditions of use. This is particularly important when the types of protection 'Flameproof enclosure' (IEC 60079-1) and 'Intrinsic safety' (IEC 60079-11) are applied.
NOTE 3 The classification of hazardous areas in zones is defined in IEC 60079-10.
NOTE 4 There may be other non-electrical sources of ignition (for example ultrasonic, optical or ionizing radiation) that are not addressed by this standard; these should also be taken into consideration (see, for example, EN 1127-1).