Explosion Proof Instrument and Ingress Protection

Explore Norma Reg 10, by the way I do not think that you are accurate of your EX interpretation either....

• Is this enclosure sealed in accordance with its certification document?
• Is the enclosure modified in any way away from its certificated condition?
• Are all the cable gland entries sealed in accordance with its certified condition using certified cable glands and blanks?
• Etc., etc.

Yes standard Ex d boxes have a small gap in the lid to allow hot gases to escape from inside the box and cool enough to not cause an explosion outside the box (that's how they work), however it is possible to get Ex d rated boxes with IP-rated gaskets up to about IP66

Link

The functional operation of the Ex d box remains uneffected because the gasket allows the high pressure release while preventing the ingress of low pressure water or dust.

Thanks..this is what I wanted to know. I didn't know abt Exd having small gap to hot gases to escape. But if what if the enclosure is not pressurized?

Best you read up on how Ex d protection actually works, the pressurisation is created by an explosion of gasses inside an ex d enclosure, the gap is necessary and there to prevent the enclosure turning into a bomb and to allow the gas enough time to cool as it passes from the inside of the enclosure out.

Very basic overview link

Hi , I went thru d link u forwarded..thanks am getting ur point but I am still confused abt certain things. I myself have got JBs installed in refinert Exd ones n I m sure that those were not Pressurized while installing. As u said high pressure may get create d after explosion But my doubt is what if molecules enter thru gaps provided??

It doesn't matter. Ex d boxes are designed to withstand the effects of an internal explosion without transmitting an incendive flame to the surrounding area.

Do not confuse this with Ex p, which is explosion prevention by purging the enclosure with air from a safe area and preventing flammable materials entering.

That is why reading is important, and adequate training is vital.

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Next time, please define abbreviations before using them.

I have read information on given links. Pls. provide if.you have any document. I googled but didn't get any proper info.

http://en.wikipedia.org/wiki/Electrical_Equipment_in_Hazardous_Areas

Please desist from any activities involving the above until appropriate workplace-based training has been completed, for the sake of the facility, its output, the safety of those working there and of those living and working in the neighbourhood.

Down here electrical plant installers or electricians may only have a rudimentary understanding of hazardous area equipment, relying quite a bit on the inspector to ensure correct compliance.

Sadly this does not always happen (a recent cool-store fire, and grain warehouse and mine explosions are evidence of that).

More detailed information can also be found in such standards as BS EN 60079-0 and its companion standards.

On another note, if you are dealing with instrumentation it is common in the drilling industry to have positive pressure enclosures for multiple instrument switchgear.

Tim

...which is Ex p, not Ex d. The original poster seems confused by the difference between them.