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hazardous area classification for diesel oil storage tankfarm

giraffetall (Electrical) (OP)
27 Jan 06 3:17
As the flash point of diesel oil (or even fuel oil) is above 65 deg.C most of the people consider the diesel oil storage tank farm as non-hazardous area when preparing the Hazardous Area Classification drawing. Another argument also is: as the auto ignition temperature is very high, 257 deg.C, most of the time the storage tank farms are classified as non-hazardous area. Recently there are some arguments on this subject.
Any one who could contribute on this subject?
Would appreciate very much for your valuable comments urgently.
quark (Mechanical)
27 Jan 06 11:39
I am not sure about the flash point. Two types of diesel available in India, High Speed Diesel(used for vehicles) and Light Diesel Oil(for furnaces) fall under Class B petroleum, which means the flash point is between 25 and 650C. The statute requires us not to go more than 999 liters(as if 1 liter can do all the devastation) for the day tank. Special licencing required if the main capacity goes beyond 15kL. In any case, we have to go for flame proof area with containment.

Zapster (Electrical)
27 Jan 06 15:30
Have you done a code study of NFPA 30, NEC Chapter 5, and API RP 500?  What are the applicable codes that the regulatory agencies required for your area?  Is this a millitary instalation?
giraffetall (Electrical) (OP)
27 Jan 06 20:50
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!
Zapster (Electrical)
28 Jan 06 1:16
If I recall correctly, there is one sentence in NEC chapter 5 that makes heating oil a Class D fluid that results in the area classification problem for tank farms.  I do not have my copy here at the house.
kchayfie (Chemical)
30 Jan 06 8:06
Its my understanding that if the area is "safe" it is OK to take naked flames and/or heat producing equipment in there, so if you need to ensure they are kept out of the area you need to designate it as some kind of hazardous area. The latest thinking where I'm working is that the inside of tanks should be zone 2 due to the possibility of mist formation during splash-filling of the tanks.

Hope this helps

jsummerfield (Electrical)
7 Feb 06 13:24
From API RP 500
“Refer to NFPA 325 for properties of specific flammable liquids, flammable gases, and volatile solids.  Flammable and combustible liquids vary in volatility and are defined in NFPA 30.” …  … “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 373°C (100"F), as determined by the test procedures and apparatus described in NFPA 30.”

NFPA 497 does not list Diesel but lists fuel oil.  Diesel may be called number 2 fuel oil where kerosine is number 1 fuel oil.

Diesel is generally unclassified.  However, fuel oil will burn easily if agitated or otherwise atomized.  Use good sense.

John

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