Categories & EPL

Atex introduced the concept of Categories and Equipment Protection Levels (EPL), partly as an attempt to simplify equipment selection. Categories, although mentions in the EN 60079 standards, are specifically relate to Atex and therefore would not be applicable under the UK certification1 and they would only be required to comply with the Atex certification during the Brexit interim period although, like everything else, that may change.

Atex Category EPL Equipment suitable for
1G Ga Zones 0, 1 & 2
1D Da Zones 20, 21 & 22
2G Gb Zones 1 & 2
2D Db Zones 21 & 22
3G Gc Zone 2
3D Dc Zone 22

The are 6 Atex Categories, designated '1', '2' and '3' representing levels of Risk 'High' 'Medium' and 'Low' respectively each with either 'G' and 'D' for Gas and Dust.

Equipment is allocated a protection Level (EPL) of 'G' and 'D' then 'a', 'b' and 'c' representing the degree of protection dependant on a number of factors, particularly 'fault conditions. This concept2 has been around for a long time with intrinsic safety protection but now has been introduced into other protection techniques In simple terms to have a EPL of 'a' (for use in any zone) safety integrity must be maintained with 2 fault conditions, for EPL 'b' only 1 fault condition and EPL 'c' no fault conditions are considered.

Currently there is always a direct correlation based on each line of the table e.g. An area category 2G will be Zone 1 and equipment inside that area must have an EPL of Gb (or Ga which is a higher level of protection).

Whereas historically equipment was selected by Zone, the correct way is to specify the Category suitability or EPL required as this is more in line with risk assessment techniques.
E.g. for a low risk dust hazard specify an EPL Dc or suitable for Category 3D

The concept of protection levels has been introduced to most protection methods allowing for different degrees of protection with in a single protection method. e.g. Ex e now becomes Ex eb or Ex ec.


Please refer to labels for examples of how these concepts go together.


Notes


  1. As the terms of Brexit are not yet full confirmed this may change, although it is believed to be unlikely. 

  2. The components in a zener barrier are a simple way of demonstrating the concept of protection levels. 

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