Flame arresetor on Mineral Oil tank?

[Bourbon103]

We are going to use a 1500 gal. tank as a mineral oil hold tank; totes of mineral oil will be pumped into the tank and mineral oil will be metered from the tank for various uses. The only "process" in the tank will be to heat it to 100C while sparging N2 to drive off enough entrained water to meet spec.

The mineral oil has a flash point of greater than 370F (NFPA Class IIIB, combustible liquid). We will be using an appropriately sized demister to remove mineral oil mist with a pressure control valve and conservation vent to atmosphere on the vent side.

Is a flame arrestor also needed? Per NFPA 30 (2008), 21.4.3.6 & 7 there is only mention of arrestors needed for IA,B,&C services. Also, I am not sure if what we are doing is technically considered a "process", which would disqualify it from being a "storage tank", per NFPA.

Any ideas?

Thanks again.

 

[psafety]

Flame arrestor for what purpose? You are 158-deg F away from generating a vapor sufficient to support a flame.

 

[EGT01]

Similar to dust explosions, a mist of combustible liquid can also be a concern...

http://dx.doi.org/10.1016/S0304-3894(03)00273-5

Sparging with N2 is an advantage especially if your N2 system along with your conservation vents are setup to prevent air from being pulled in.

There is some opinion that a flame arrester is not needed in conjunction with a pressure vacuum vent. From API 2000...
"A flame arrester is not considered necessary for use in conjunction with a PV valve venting to atmosphere because flame speeds are less than vapor velocities across the seats of PV valves (see API Publication 2210)."
There is additional information in API 2000 you should review.

If mist is a concern, then also consider whether there are any internal sources of ignition (static, etc) that need to be addressed.

 

[Chance17]

Mineral Oil Mists can cause a Fire but I would not install a Flame arrestor to protect against mist fire. The Flame Arrestor on Storage Tank vents is typically associated with "pool fire". In event of an external 'pool fire", the Flame arrestor prevents flames from being pulled inside the tank. If the mineral oil tank has significant containment dykes, a flame arrestor should be considered. If there is only curbs or little containment, then avoid the arrestor. There are generally more negatives than positives associated with Flame arrestors. My advise is to use sparingly.