Diesel Fuel

[derf48]

Can anyone tell me the flash point of diesel fuel, or where to find that info. Am trying to use NFPA 497 in the classification of an area where the only liquid present is diesel fuel. Thanks for your help!

Fred J. Bender

 

[charlie]

Re: Diesel Fuel

The flash point of Fuel Oil 1 and Kerosene are both 72?C, I don't have a clue about diesel fuel (I assume it is about the same). I got the information from the 2005 NFPA NEC Handbook in the commentary in Section 506 which was extracted from the NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas. The entire table was not extracted.

As far as classifying and area for diesel fuel, it is not required to be classified and that may be why you can't find it.

 

[derf48]

Re: Diesel Fuel

Thanks Charlie.
I went thru the archieves and did a search for diesel fuel, found a comment that the flash point was about 150 degrees F. I am actually looking for where I can find that info so I can document it, want to follow the NEC, especially 500.4 (A).

Fred J. Bender

 

[rbalex]

Re: Diesel Fuel

Diesel, like gasoline, is actually a blend of various combustibles; however unless it is handled above it's flash point it is rarely the basis for electrical area classification. This is one reason it isn't listed in the Handbook, or NFPA 30 (Combustible Liquids Code) for that matter.

I recommend getting a copy of the Material Safety Data Sheet (MSDS) from the supplier. It's an OSHA Process Safety Management requirement anyway and the fire hazard data, including flash-point, is part of the supplied information. Several suppliers have their MSDS on-line.

 

[derf48]

Re: Diesel Fuel

I found the correct answer and am sharing the source. The Material Safety Data Sheet, affectioately called MSDS, had all the info. The company I am working with buys a special diesel fuel with a "low " flash point of 125 degree F. This is well above the upper limit of a flamable liquid defined in NFPA 497 as any liquid that has a close-cup flash point below 100 degree F which makes diesel fuel a combustible liquid. Therefore its presence does not make an area a Class 1 location per definition in 500.5 (B) (1) in the NEC. Normal diesel fuel has a flash point or around 150 degree F. Thanks

Fred J. Bender

 

[coulter]

Re: Diesel Fuel

There are a few gotchas concerning area classification for combustible fluids at less than flash point.

Paraphrase of Osha reg: Heating a combustible fluid to within 30 deg F of it's flash point requires the area be upgraded one rating. So, one would go from unclassified to C1,D2. Yep, it's in there.

1910.106(a)(18)(iii)

When a combustible liquid is heated for use to within 30 deg. F. (16.7 deg. C.) of its flashpoint, it shall be handled in accordance with the requirements for the next lower class of liquids.

carl

 

[rbalex]

Re: Diesel Fuel

My interpretation is that it says a combustible liquid heated to within 30?F of its flashpoint will cause a Class IIIB liquid to be treated as a Class IIIA, a Class IIIA liquid as a Class II, a Class II as a Class IC, a Class IC as a Class IB and a Class IB as a Class IA (using NFPA 30 classifications, which 1910.106 doesn?t)

The fact is that it has no technical merit, which is why NFPA 30 no longer even hints at it and is one reason OSHA often has a problem enforcing its rules.

NFPA 497 says:

2-2.7.1 With Class II liquids, the degree of hazard is lower because the vapor release rate is low at the normal handling and storage temperatures. In general, these liquids will not form ignitable mixtures with air at ambient temperatures unless heated above their flash points. Also, the vapors will not travel as far because they tend to condense as they are cooled by ambient air. Class II liquids should be considered capable of producing an ignitable mixture near the point of release when handled, processed, or stored under conditions where the liquid may exceed its flash point [Note: no mention of 30?F- rbalex]
2-2.7.2 Class IIIA liquids have flash points at or above 140?F (60?C) but below 200?F (93.4?C). These liquids do not form ignitable mixtures with air at ambient temperatures unless heated above their flash points. Furthermore, the vapors cool rapidly in air and condense. Hence, the extent of the area requiring electrical classification will be very small or nonexistent.
2-4.7.3 Class IIIB liquids have flash points at or above 200?F (93.4?C). These liquids seldom evolve enough vapors to form ignitable mixtures even when heated, and they are seldom ignited by properly installed and maintained general purpose electrical equipment. A Class IIIB liquid will cool below its flash point very quickly when released. Therefore, area classification is seldom needed and Class IIIB liquids are not included in Table 2-1 .

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