Class 1 Div 2 Question
Class 1 Div 2 Question
(OP)
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.






RE: Class 1 Div 2 Question
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.
RE: Class 1 Div 2 Question
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.
RE: Class 1 Div 2 Question
Regards,
ampss
RE: Class 1 Div 2 Question
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.