Diesel generator fuel storage

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ckinney02

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I have been researching details on diesel storage for a back-up generator. The generator will be outside but in an small enclosure. The diesel fuel tank is a sub base tank so the engine will be mounted on top of the tank. I want to better understand the reasons behind not having to classify the diesel fuel. The unit will sit outside on a concrete pad. It isn't usual for the summer ambient temps to reach 115 degrees which could be as high as 125 degrees on the concrete. Depending on the type of diesel fuel, I feel it could reach its flash point or be very close. The forums that I've been reading have people stating that since diesel fuel is only a combustible liquid then classification isn't needed which I don't necessarily agree with or find their understand their justification. I think the installation that I describe above would warrant some considerations of CIDII. What are everyone thoughts/comments?
 

BPoindexter

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MT Vernon, WA
Ckinney- assuming the product you are using does have a flashpoint at or below 125 F then it would be a class II liquid. Per API-RP500 which is used by engineers to determine classification this would not represent enough of a hazard to warrant electrical classification except possibly in the immediate area around a vent.

Combustible (Class II and Class III) liquids, such as kerosene and diesel fuel, are defined as liquids having a closed cup flash point at or above 37.8?C (100?F), as determined by the test procedures and apparatus described in NFPA 30. Class II liquids are combustible liquids having flash points at or above 37.8?C (100?F) and below 60?C (140?F). Class III liquids are combustible liquids having Flash points at or above 60?C (14?F).

You could refer to NFPA 30 or even better use the MSDS for the product to determine flashpoint. Having said all of that however here is what API has to say:

The chance of ignition of vapors of Class II liquids is not as great as ignition of the vapors of Class I liquids. Their vapors normally do not travel as far as the vapors of Class I liquids. Normally, except near points of release, Class II liquids do not produce vapors of sufficient quantity to be considered for electrical classification purposes.

Class III liquids normally do not produce vapors of sufficient quantity to be considered for electrical classification purposes. Class III liquids will release vapor in the flammable range at their surfaces if heated above their flash points, but the extent of the classified location ordinarily will be very small and near the point of release.

I have worked in some very hot locations (Oklahoma) where you can reach temps in the 100's and do not know of any diesel facilities that are classified. In the end a PE should make the determination for any classifications.

Hope this helps.
 
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