I have a question regarding the need to provide electrical classification for a building using Class 1A flammable liquids.
For this building, 4 gallons could be out in use (located anywhere in the building). The MAQ is 10 gallons. I have discussed this with NFPA 30 committee, the manufacturer, and the AHJ (who is a knowledgeable FPE). They have all determined that even if the MAQ is not exceeded, electrical classification is required if a flammable/explosive mixture could be present. The NFPA 30 staff directed me to a provision in NFPA 497, Section 5.5, that if the materials will not reach 25% of the lower flammable limit (LFL), this could be utilized to justify not providing classified electrical fixtures. Does anyone know how to do this calculation, or know of firms that can be hired to do this? I am an FPE and do not know how to perform it, and I have spoken with other FPE’s who also are not aware. The gentleman I spoke with at NFPA 30 agreed it would be by an industrial hygienist or a chemical engineer and not an FPE. But does anyone know any that can be hired for a one-off calculation, or have a place where I could learn how to perform it myself (NFPA reference, SFPE article, course, etc.?). Thank you! Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
5 Comments
B
10/29/2020 08:31:27 am
Fortunately, vapor density and LFL are intrinsically related so this is only a two-equation problem.
Reply
FRANK J. HERRICK
10/29/2020 10:18:45 am
Reply
10/29/2020 10:41:51 am
NFPA Fire Protection Handbook, Volume II, 20th Ed.
Reply
Shahpoor
10/29/2020 12:36:13 pm
You can definitely find the calculations in
Reply
SK
10/29/2020 07:40:03 pm
You problem is very straightforward and love to help you out here, The whole Purpose of Electrical Area Classification is to "Avoid Explosion if there is flammable mixture present and caught Ignition sources",. In any facility, Flammable mixture can not be avoided when air is freely available and storage of flammable products is your design intent. So the only option left for engineering to address this risk is to control the ignition sources. So how we do this? Avoid ignition sources as much as you can. However In any facilities either indoor or outdoors, Electrical Equipment/Instrument are unavoidable and poses for risk for sources of Ignition too. So next question is how to avoid ignition? select the Electrical equipment in such a way that it does not create ignition (or withstand-Explosion proof) or even if created, select suitable equipment which fits into that zone where it is to be located and sustained surface temperature lower than Ignition temp (these areas are classified as ZONE 0, Zone 1, Zone 2 or Division 1 & Division 2). Zone 0, No electrical/Instrument allowed.
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