Hazardous area

Grouping of electrical apparatus for potentially explosive atmospheres.

Group 1
ELECTRICAL APPARATUS FOR MINING, TYPIFIED BY THE GAS METHANE (FIREDAMP)

Group 2
ELECTRICAL APPARATUS FOR SURFACE INDUSTRY
Group II may be further divided into three gas groups:
IIA - Representative Gas Propane
IIB - Representative Gas Ethylene
IIC - Representative Gas Hydrogen
Gas Group IIC covers the most hazardous gases and as such, apparatus marked IIC may be used in IIA and IIB applications.

Classifications

Zone 0 Gas, 20 Dust
Zone in which an explosive atmosphere is constantly present, or present for long periods. (Rough guide: hazard present for more than 1000 hours/year).

Zone 1 Gas, 21 Dust
Zone in which an explosive atmosphere is likely to occur in normal operation.  (Rough guide: hazard present between 10 & 1000 hours/year).

Zone 2 Gas, 22 Dust
Zone in which an explosive atmosphere is not likely to occur in normal operation and if it occurs it will exist only for a short time. (Rough guide: hazard present for less than 10 hours/year). Guidance in the classification of hazardous areas is given in BS EN 60079-10:1996, IEC79-10.

Protection concepts

See Hazardous Area download sheet (630 KB PDF document).

Temperature class

Explosion protected electrical apparatus must be designed and tested to ensure that the maximum surface temperature of any part(s) of the products are below the ignition temperature of the explosive atmosphere concerned. Group II electrical apparatus is divided into temperature classes according to the maximum permissible surface temperature of the apparatus. The preferable classification of temperatures is given in the following table:-
Unless otherwise specified the maximum ambient temperature is taken to be 400ºC.

 
Datasheet download

The Hazardous Area download sheet is a 630 KB PDF document.