What is flame path and flame gap of the 'Ex-d' flame proof equipment like lighting fixture, motor etc, used in Zone 1 & 2. Also how we can practically measure it.
Hi,
Not sure exactly where your question is leading but, my understanding is as follows.
Ex-d (flameproof or explosion proof, depending on where you are in the world) equipment works like this: the equipment enclosure does not aim to completely exclude flammable vapours but rather, should such vapours build-up into the explosive range and be ignited by the enclosed devices, the resulting combustion products cannot (a) burst open the enclosure or (b) ignite flammable vapours <b>outside</b> the enclosure.
As I understand it, the flame gap allows the pressure generated by the combustion products to be relieved without damage to the enclosure and the flame path is sufficiently long that the combustion products are cooled enough by contact with the sides of the path that they can not ignite vapours outside the enclosure. Others more expert in this field than me can probably explain it much better.
How do you measure this stuff? Well, you don't AFAIK. The agencies the certify equipment to be Ex-d, Ex-e, Ex-n etc. do all the necessary measurement and testing. We simple field engineers just ensure the equipment is certified to the appropriate standards for the application, keep the appropriate records and ensure maintenance is carried out correctly. For ex-d equipment this usually means maintenance is performed only by properly qualified technicians and using only the exact methods and materials specified by the manufacturer and/or certifying agency - particularly with regard to gaskets, sealants, fixings (i.e. number and ratings of bolts etc.)
I’ve been out of this field for some years now - I’m sure others can explain it more clearly.
