HAZARDOUS AREA EQUIPMENT
Classification of Hazardous Areas
- Explosive gas vapours atmospheres
- Combustible Dust
- Specific occupancies
Hazardous area equipment is specified in terms of the types of gases present or where dust is present.
- Group I – Underground mining applications
- Group II – Industries other than mining
- Group III – Industries having dust or fibres
Group I :
Equipment has a representative gas of Methane and all equipment used in underground mining applications fall into this category.
As shown in the below table this Group II is segmented into three different representative gas groups, IIA, IIB and IIC.
Equipment is segmented concerning the thickness of the dust – Practice A and B regarding maximum surface temperatures relating to the ignition temperatures of the material. The Group III dusts are segmented into three different representative dusts IIIA, IIIB and IIIC, with the worst case being IIIC for conductive dusts.
|Group Classification and Representative Gas Data Table|
|Group Classification||Representative Gas|
Equipment Protection Levels EPLs
The introduction of Equipment Protection Levels ( EPLs ) is provided to give further segregation of products and protection techniques for hazardous areas. The EPLs consider assessment of the risk involved with an installation and the suitable equipment protection techniques. These EPLs are generally in line with Zones, however on risk assessment a higher EPL may be used to provide higher protection. Where an EPL is specified on a hazardous document it takes precedence over the Zone classification.
|Group Classification and Zone Data Table|
|Group I||Group II||Group III|
|Zone 0 – EPL Ma||Zone 0 – EPL Ga||Zone 20 – EPL Da|
|Zone 1 – EPL Ma and Mb||Zone 1 – EPL Ga, Gb||Zone 21 – EPL Da, Db|
|Zone 2 – EPL Ga, Gb and Gc||Zone 22 – EPL Da, Db and Dc|