Hi there,

That completely depends on how the ex proof rating of the device was achieved. You are stuck if a purge unit was used to obtain it. Otherwise this would be completely redundant. ■

If the enclosure is exp prf & rated for the area purging is not necessary. However you must use approved sealing fittings where conduit or cable enters the enclosure to maintain the exp prf approval.

I have only seen purge systems used on enclosures which do not meet the requirements for the area. ■

If the original equipment is labelled Ex d (explosion proof), there is no need to purging & pressurizing it. If the equipment is labelled Ex p (pressurized), purging & pressurizing are expected to exist.

Maybe your question raised after you find a non-authorized modification in an Ex d enclosure, where a compressed air tubing was connected to the original Ex d enclosure.

Sometimes Ex d enclosures have electronic cards inside, and due to the lack of ventilation, high temperatures are developed inside the enclosure, what causes electronic cards to fail.

Some technicians "solve" this problem connecting compressed air lines to the enclosure.

Although this practice decreases the internal temperature, it violates the explosion-proof principle as this is considered a modification of the original enclosure.

Estellito ■