NEMA spec question - hazardous environments
NEMA spec question - hazardous environments
(OP)
Hello,
I am looking to design a NEMA 8 enclosure and would like to know if anybody has experience with what exactly the spec means. I can't decipher if it means the electronics enclosure will be filled with oil or if it will be submerged in oil. Oil submersion makes more sense to me, but I haven't seen that in practice yet, so I don't know if that is something standard. Any tips?
The spec reads, "Type 8 enclosures and enclosed devices are arranged such that all arcing contacts, connections, and the like are immersed in oil. Arcing is confined under the oil such that it will not ignite an explosive mixture of the specified gases (hydrogen, cyclopropane, gasoline, acetlyene, etc) in internal spaces above the oil or in the atmosphere surrounding the enclosure. Enclosed heat generating devices shall not cause external surfaces t oreach temperatures capable of igniting explosive gas-air mixtures in the surrounding atmosphere. Type 8 enclosures:
a. Provide, by oil immersion, a degree of protection to a hazardous gas environment from operation of internal equipment.
...
c. Withstand a series of operation design tests with oil levels arbitrarily reduced and with flammable gas-air mixtures introduced above the oil.
That's pretty much it. Ideas?
I am looking to design a NEMA 8 enclosure and would like to know if anybody has experience with what exactly the spec means. I can't decipher if it means the electronics enclosure will be filled with oil or if it will be submerged in oil. Oil submersion makes more sense to me, but I haven't seen that in practice yet, so I don't know if that is something standard. Any tips?
The spec reads, "Type 8 enclosures and enclosed devices are arranged such that all arcing contacts, connections, and the like are immersed in oil. Arcing is confined under the oil such that it will not ignite an explosive mixture of the specified gases (hydrogen, cyclopropane, gasoline, acetlyene, etc) in internal spaces above the oil or in the atmosphere surrounding the enclosure. Enclosed heat generating devices shall not cause external surfaces t oreach temperatures capable of igniting explosive gas-air mixtures in the surrounding atmosphere. Type 8 enclosures:
a. Provide, by oil immersion, a degree of protection to a hazardous gas environment from operation of internal equipment.
...
c. Withstand a series of operation design tests with oil levels arbitrarily reduced and with flammable gas-air mixtures introduced above the oil.
That's pretty much it. Ideas?





RE: NEMA spec question - hazardous environments
The sentences "...all arcing contacts, connections, and the like are immersed in oil." and "...in the atmosphere surrounding the enclosure." tell me the explosive gas is surrounding the NEMA 8 enclosure, which encloses arcing contacts immersed in oil.
Of course, part c. muddies the waters a bit... "...with flammable gas-air mixtures introduced above the oil." This would tell me the enclosure itself might be immersed in oil.
Sounds like a poorly written spec (are there any other kind?).
Dan - Owner

http://www.Hi-TecDesigns.com
RE: NEMA spec question - hazardous environments
The rest of the spec does not give any insight. Maybe I should try to find NEMA 8 equipment and see how it is being used. Thanks for the input, mac.
RE: NEMA spec question - hazardous environments
Generally, when you see don't see something done commonly, it's because many others have looked at it, or tried it, and found it to be worse than alternatives.
I would review my need for such a brute force solution before trying much more to understand that confusing text. Bleeeech!
Keith Cress
kcress - http://www.flaminsystems.com
RE: NEMA spec question - hazardous environments
But back to the spec;That seems clear and I don't see anything about immersing the enclosure in oil.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: NEMA spec question - hazardous environments
Dan - Owner

http://www.Hi-TecDesigns.com
RE: NEMA spec question - hazardous environments
The spec is from our customer and believe me, we would like drop that requirement, as I don't think an oil filled enclosure will play nice with RF data trying to transmit and receive. (the plot thickens...)
RE: NEMA spec question - hazardous environments
The only electronics I've seen submerged in oil was computer hardware where the individual was trying to impress friends and others on the internet with their overclocking capabilities.
If you do this, you will likely have to qualify it with some type of testing or approval. I know I would not accept a box from some supplier that is to be installed in a hazardous location and claimed "NEMA 8" but not tested. The insurance company probably wouldn't like it to much either.
RE: NEMA spec question - hazardous environments