Area Classification for Sump Outside of a Chemical Refinery
Area Classification for Sump Outside of a Chemical Refinery
(OP)
All: I have to determine what the correct area classification is for a sump near an oily trench area.
From what I have read so far, NFPA 497 suggests that if you have the presence of liquid hydrocarbon detected, you would have Class 1 Division 1, classification. According to what else I found, Figure 5.9.7 of NFPA 497 seems to support Class 1 Division 1 in the sump and Class 1 Division 2 is used above grade- 18 inches above the sump.
Is this analysis correct?
Also, if I decide to use Intrinsically Safe Barriers for any field devices, can I avoid use of seal-off fittings?
Please advise.
From what I have read so far, NFPA 497 suggests that if you have the presence of liquid hydrocarbon detected, you would have Class 1 Division 1, classification. According to what else I found, Figure 5.9.7 of NFPA 497 seems to support Class 1 Division 1 in the sump and Class 1 Division 2 is used above grade- 18 inches above the sump.
Is this analysis correct?
Also, if I decide to use Intrinsically Safe Barriers for any field devices, can I avoid use of seal-off fittings?
Please advise.





RE: Area Classification for Sump Outside of a Chemical Refinery
Although basically your narration/explaination and derived inference all seem OK!
However it may be more useful/pertinent if any image or pictorial dispay of the situation under discussion is shared with forum colleagues.
This may get you very close to your answer I believe.
Best Regards
Qalander(Chem)
RE: Area Classification for Sump Outside of a Chemical Refinery
RE: Area Classification for Sump Outside of a Chemical Refinery
RE: Area Classification for Sump Outside of a Chemical Refinery
Does anyone happen to know if you can use Intrinsically safe wiring in LIEU of say explosion proof junction boxes or seal-off fittings inside a Class 1 Division 1 area?
This was what I was hoping to understand.
Also, does anyone have any information from API RP 500(?) that would either enhance or contradict what I said above about the area around the sump and the like? I was of the understanding that API 500 was written for areas of the petrochem facility that were directly involved with processing of hydrocarbon products where NFPA 497 was more for the areas NOT associated with hydrocarbon products (such as the area where I am doing work currently?)
Is my statement correct?
RE: Area Classification for Sump Outside of a Chemical Refinery
Article 504 is the basic IS installation standard. Beyond what JLSeagull mentioned, an IS installation must conform to a manufacturer's "Control Drawing"(504.10(A)). Proper grounding (504.50) and bonding (504.60) are also commonly overlooked and the requirements are not nearly as relaxed as one might expect. Sealing requirements are in Section 504.70.
RE: Area Classification for Sump Outside of a Chemical Refinery
1st, thanks for your reply.
Do you have to have seal-off fittings IN ADDITION to providing the intrinsically safe barriers?
RE: Area Classification for Sump Outside of a Chemical Refinery
Occasionally, process instrumentation or other equipment with direct interfaces to the process materials may need seals. See 504.70 Exception.