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Class 1 Division 1 question NEC question

Class 1 Division 1 question NEC question

Class 1 Division 1 question NEC question

(OP)
My guys are installing a diesel fuel filtering system for a tank that is connected to a back up generator.

The system consist of a small 1" gear pump driven by a 1.5HP TEFC motor that is installed inside of an NEMA 4X enclosure with no ventilation, the pump draws fuel into the enclosure through 1" brass pipe fittings through the pump, discharging the fuel through a centrifuge fuel purifier and then through a fuel Mag treating for microbiological bacteria then the fuel is returned to the storage tank.

Additionally inside of this 4X enclosure is a motor start relay, small PLC and a float switch located at the bottom of the enclosure. All of this interconnected with gray plastic liquid tight flexible conduit.

I contacted the Mfg. of this system they could not refer me to a particular code only to say its some ware in the NEC and we been doing this for years we have these systems all over the US in various business and government facilities.

According to NFPA 30 1.7.3.1 any liquid that has a flash point at or above 100 f and below 140 f is considered to be a Class II combustible liquid.

Reviewing the MSDS indicates No1 Low Sulfur Diesel fuel has a flash point of 110 f and No 2 Diesel Fuel has a flash point of 130 f.

What am I missing?? Surely this application should be considered a Class 1 Division 1 environment..

Any thoughts would be appreciated.

RE: Class 1 Division 1 question NEC question

Hi Marco,

Get yourself a copy of the ANSI/ISA TR12.24.01, recommended practice for classifying hazardous locations.  Also NFPA 497 has good guidance.

Typically, we don't classify diesel fuel as hazardous in normal ambient temperatures.  The fuel flowing through your enclosure is all contained in sealed piping, so there should be no hazard during normal operation.  Will there be a hazard in the event of a leak?  Maybe.  You have to assess the probability of the ambient in your box reaching up above the flash point and a leak occurring at the same time.  If highly unlikely, Class I Div 2.  If nearly impossible, no classification.  Each such apparatus needs to be evaluated individually with the application.

Just a little more evidence -- if you're around generator fuel day tanks that are indoors, you'll almost always see an open-type relay on top of the tank that operates the pump -- most often in a NEMA 1 enclosure.

In sum, you should get an engineer who is licensed in your state and experienced with hazardous location classification to make the call if you're unsure.

Good on ya,

Goober Dave

 

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