Type of Enclosure Protection Class


Thread Starter


My project has hazardous area classification as "IIA, IIB - Zone 2 - T3".

I know that just like IIC certified equipment can be used for IIB and IIA. Is there any similar hierarchy for protection.

Actual problem is that our project enclosure rating is Ex'd but one vendor has supplied us Ex'nl enclosure rating. Now i am asked to check if Ex'nl is OK to be installed instead of Ex'd.

I cannot find any basis for such requirement. I think if i can get any hierarchy for Ex rating the problem can be solved.

Please help.

Bruce Durdle

The methods of protection can be used in different zones, with a sort of hierarchy - anything that is good for Zone 0 or Zone 20 can be used in all zones, anything that is good for Zone 1 or 21 can be used in 2 or 22 as well.

Ex n equipment of any type is suitable only for Zone 2. Ex nL is a low-integrity version of Ex i, and is equivalent to Ex ic (safe under normal condition but not necessarily with any faults). I'm not sure what an Ex nL enclosure would look like, as Ex nL, like Ex i, is a system certification rather than certification applicable to an individual piece of apparatus. If the rest of the equipment and circuits are Ex d, then Ex nL is not appropriate (in the same way as you can't use Ex d or e - protected items on an Ex i circuit).

You really need to get expert advice on your specific application (and find out what the local interpretations of the rules are).