Reduce Classification within a Protected Enclosure
- Thread starter jaykool
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- Mission Viejo, CA
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- Professional Electrical Engineer
It is fairly straight-forward. From NFPA 496-2003, Standard for Purged and Pressurized Enclosures for Electrical Equipment:
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- Mission Viejo, CA
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- Professional Electrical Engineer
NFPA 496 is the recognized Standard for Purged and Pressurized Enclosures for Electrical Equipment. The link is to the NFPA’s 2008 online edition.
There are several considerations for each “Type.” They are generally outlined in Chapters 4 and 5. “Additional Requirements for Type Y or Z Pressurizing” are reviewed in Section 5.4. “Additional Requirements for Type X Pressurizing” are reviewed in Section 5.5. Chapter 8 contains information where the enclosures have an internal source of flammable gas or vapors.
Nitrogen is a common “protective gas,” although it is not specifically required in any particular application. It is commonly considered to be an inert gas in the few applications that require that property, especially if it is of the "Dry" type. ("Dry" is NOT a requirement in itself though, just generally considered good practice.)
Without specific knowledge of the anticipated installation, it is impossible to say much more.
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There are several considerations for each “Type.” They are generally outlined in Chapters 4 and 5. “Additional Requirements for Type Y or Z Pressurizing” are reviewed in Section 5.4. “Additional Requirements for Type X Pressurizing” are reviewed in Section 5.5. Chapter 8 contains information where the enclosures have an internal source of flammable gas or vapors.
Nitrogen is a common “protective gas,” although it is not specifically required in any particular application. It is commonly considered to be an inert gas in the few applications that require that property, especially if it is of the "Dry" type. ("Dry" is NOT a requirement in itself though, just generally considered good practice.)
Without specific knowledge of the anticipated installation, it is impossible to say much more.
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weressl
Esteemed Member
petersonra
Senior Member
- Location
- Northern illinois
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- engineer
Sometimes nitrogen is specified because it is relatively easy and not outrageously expensive to put a bottle of nitrogen out where the panel is. Its not required for reducing the classification, but might be handy for other reasons.jaykool said:
BTW, has anyone here ever actually used type Y? I never have, and can't even ever recall seeing it.
weressl
Esteemed Member
petersonra said:
Analyzers is one example where you actually carry the flammables inside the analyzer cabinet and need to expose them to be analyzed, so you purge the cabinet to keep it below LFL.
petersonra
Senior Member
- Location
- Northern illinois
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- engineer
weressl said:
what does that have to do with nitrogen purging?
are you saying you purge with N2 so there is no oxygen inside the cabinet that might potentially react with the flammables?
never had to do that although I seem to recall one panel that was purged had the exhaust piped to a non-hazardous area so the solenoid valves could exhaust inside the box and have no path for hazardous gases to enter through the exhaust tubing.
weressl
Esteemed Member
petersonra said:
My response was given to the Y purging.
Nitrogen can be used for purging where inerting may simplify the classification issue. If nitrogen used then the classification would be X, not Y.
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