Relief Valve on EXP Enclosure

[fifty60]

I have an explosion proof enclosure with a relief valve located on top. Why would this enclosure have a relief valve?

[petersonra]

are you sure it is a relief valve, and not just a vent?

[fifty60]

It looks like a valve, I believe it is called a "drain and breather", the one I am referring to is on top so it is a breather. These do not compromise the ability to contain an explosion?

[petersonra]

It looks like a valve, I believe it is called a "drain and breather", the one I am referring to is on top so it is a breather. These do not compromise the ability to contain an explosion?

not if they are identified for such service.

[rbalex]

This is a typical manufacturer's application diagram.

They do practically guarantee that flammable gases/vapors will enter an explosionproof enclosure. Then again, the flammable gases/vapors will enter through any threaded connection anyway, with or without a drain/breather, which is why I usually avoid them.

That said, a drain/breather identified for Class I does not usually "compromise" the enclosure. The exception is salt-air applications where residue build up may (only may) defeat the spring. Personally, I've never had that happen.