Hi Zapster, thanks for your interest on the subject.
The applicable Codes in this case are "NFPA 70 (i.e NEC Chapter 5)" and "IP model Code Of Safety Part 15 (latest edition)". This is not a military installation. It is an "Oil Storage Terminal Project".
The Owner demanded to be classified the TankFarm as hazardous area whereby Contractor put up the area classification as "Safe" area. Thus there is a dispute on the subject.
Once the "NFPA 70" is specificed, it also refers back to "NFPA 30". Even API RP 500 is also more or less the same as "NFPA 70".
The argument is that under the normal atm. pressure and temperature, Diesel Oil does not produce flammable gas (NOTE: Diesel Storage is under atm. Pressure). Remember in Diesel Engine, in order to achieve combustion you need a compression stroke. In some Diesel Engine they also provide heater to preheat before engine is started. Thus there is no flammable gas around at atm temp. and pressure, thus no hazardous area (safe area).
Another argument also is the auto ignition temperature is 257 deg.C. Thus as long as there is no naked flame (keep the nake flame away)and heat producing equipment away from the TankFarm, it can be a "Safe Area". It all depends on the Plant Layout Design.
Thus in conclusion the TankFarm can be classified as "safe Area" provided the design met the above arguments.
Anybody who disagree on these arguments??
Welcome all further comments!