Purpose of Explosion proof seals and enclosures
Purpose of Explosion proof seals and enclosures
(OP)
I understand how to use explosion proof seals and enclosures, I`ve installed them many times. What I can`t find an answer to [even after reading the NEC and searching several websites] is what exactly is the purpose. Is it to prevent an explosion from entering electrical systems or is it to CONTAIN an explosion and keep it from exiting an explosion proof enclosure.
My thought is that it is to contain an explosion. Simply because it is near imposible to prevent vapors from entering sparking areas and why else would there be a hundred bolts on an enclosure? To keep it from blowing in? I think not. To keep the explosion from blowing out makes more sense.
Any clarification would be appreciated.
My thought is that it is to contain an explosion. Simply because it is near imposible to prevent vapors from entering sparking areas and why else would there be a hundred bolts on an enclosure? To keep it from blowing in? I think not. To keep the explosion from blowing out makes more sense.
Any clarification would be appreciated.





RE: Purpose of Explosion proof seals and enclosures
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Appelton has a similar book, but I don't think it's on line.
RE: Purpose of Explosion proof seals and enclosures
When explosion proof enclosures are tested for approvals they put explosive gas in the enclosure and ignite it and make sure explosive vapors outside the enclosure are NOT ignited. Other things that are taken into account within the testing is the air volume within the enclosure. If this volume is explosive, and ignited, you must contain it. Less volume means less potential explosive energy.
Once you have an explosion at a facility, what happens to the equipment is a very minor concern to the potential injuries and death that may occur.
RE: Purpose of Explosion proof seals and enclosures
RE: Purpose of Explosion proof seals and enclosures
2 The number of bolts are provided to ensure that enclosure do not break due to the pressure/force generated by the explosion within the enclosure.
R.Thiyagarajan
RE: Purpose of Explosion proof seals and enclosures
It also explains why the group and fuel type is important. The enclosure design has to take into account the molecule size and the flash point of the fuel to design the seal of labyrinth.
It also explains why an explosion proof enclosure may not have a high enough watertight integrity rating for the application. For instance a Class 1 Div 1 Group D motor may not have an IP rating of 67, and could fail due to water ingress.
RE: Purpose of Explosion proof seals and enclosures
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Purpose of Explosion proof seals and enclosures
JRaef.com
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RE: Purpose of Explosion proof seals and enclosures
Not so sure about the seals. The ones that I am familiar with may allow cooled gases to escape, but prevent the passage of hot gases into the conduit. The casting compound is pretty tough and impervious. I think that to pass any gases the potting or casting compound would have to rupture, at which time there would be no controlled cooling. Any chance of ignition of gases in a conduit is to be avoided because of "Pressure Piling". As an explosion propagates down a pipe, the pressure generated by the combustion/explosion increases both the strength of the explosion and the speed of propagation.
There may be some leakage past the threads of the filling plug which will provide the required cooling, but no passage past the potting compound into the conduit.
RE: Purpose of Explosion proof seals and enclosures
respectfully
RE: Purpose of Explosion proof seals and enclosures
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RE: Purpose of Explosion proof seals and enclosures
Its also interesting that as the volume of the enclosure increases the potential explosion pressure increases and the enclosure walls have to be made much thicker. It was much less expensive for me once to use two small enclosures once than one larger one for that reason.
The Europeans have the best idea in all this: Intrinsic Safey design.
RE: Purpose of Explosion proof seals and enclosures
RE: Purpose of Explosion proof seals and enclosures
RE: Purpose of Explosion proof seals and enclosures
Fire protected equipment is for stopping flammable gaseous to go inside of electrical equipment. What ever happen inside must stay inside. What ever is outside must stay outside.
Depending on type of hazardous area you have different types of protection.
RE: Purpose of Explosion proof seals and enclosures
Where is this principle applied? This is not the basis of explosion proof (US) or flameproof (European) protection. Flammable gases may enter the enclosure, but if ignited the flame is not allowed to propagate to the outside of the enclosure. See my earlier post regarding the function of flameproof equipment.
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Sometimes I only open my mouth to swap feet...
RE: Purpose of Explosion proof seals and enclosures
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Purpose of Explosion proof seals and enclosures
It is the name 'fire protected equipment' that has me puzzled. Maybe it is how the phrase translates into English. I agree: it sounds like a pressurised enclosure, Ex 'P' in Europe.
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Sometimes I only open my mouth to swap feet...