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Class 1 Div 2 Question 2

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rjw57

Mechanical
Jan 27, 2002
109
Can an enclosure which is z-purged to reach general purpose classification in a class 1 div 2 surrounding environment house any sensors or instruments which contain the offending fluid? I have a box which contains electronics which will be z-purged and I do not believe that it would be correct to house either a mass flow meter (ala Brooks or MKS) and a pressure transducer since they both "contain" the offending fluid. I believe that this would then render the enclosure a class 1 div 2 space, yet several of my colleagues disagree. Any NEC citations available? Go easy on me, I'm an ME.
 
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The NEC doesn’t address this except to refer to NFPA 496 in a Fine Print Note (FPN) for the definition of Purged and Pressurized [Sec 500.2] and other like FPNs throughout Article 501.
Without further details this would be an application of NFPA 496, Chapter 8. It isn’t a particularly long Chapter and Table [NFPA 496] 8.2.3 would probably answer your question after reviewing the rest of the Chapter.

 
@rbalex

Thanks for the reply. Spot on answer. It had been some time since I had reviewed NFPA 496, but the answer is exactly contained there.
 
I am to change out a motor and pump that feeds diesel fuel to an emergancy generator in an enclosed generator room. The scope is to change with the same type of pump and motor. Their is no problem their although i am questioning the flex conduit that is mechanically attached to the motor and rigid plumbing for the electrical connection. should i leave it the same or upgraded to present code? And is their anything better now days for such an aplication since the clasification in this are is unknown how should i treat the mechanical electrical conection from coduit to motor?

Regards,
ampss
 
Post the diesel question in another thread.

If you have a Class I hydrocarbon contained inside an enclosure then the internal rating could be Division 1 instead of Division 2. The rating of the internal piping or tubing would be Division 1, Zone 0. You cannot eliminate the hazard of leaking propane or gasoline inside the enclosure by increasing the differential pressure. The 0.1 inch water pressure is intended to prevent the outside atmosphere from entering the enclosure. Common sense suggests that a type Z purge is not suitable for using general purpose components inside an enclosure that contains hazardous fluids.
 
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