Transformer Blast Wall

[TheLinker]

I am currently designing a foundation / blast wall system for an electrical transformer ( greater then 5,000 gal). I have the separation and line of sight requirements to determine the height of the wall but looking at FM Global, IEEE and NFPA, I do not find a way to determine the design blast force to apply to the wall.

Does anyone have experience or references on how to determine the blast force on a wall a certain distance from a fuel source? or are there are code provisions on how to determine the design loads required on a blast wall for a transformer?

 

[7anoter4]

As I remember, once I had to introduce 2 *400 KVA [2*400 l [2*100 gal oil] oil transformers in a dwelling building basement. I consulted then a Civil Engineer and he redesigned the basement roof to withstand 1 kgf/square m blast pressure [I think is 0.14 lbf/inch^2].For 5000 gal oil may be 50*0.14=7 lbf/inch^2[roughly]
The NFPA 850 Standard states the height and the clearance for the Fire Wall. The Fire Wall shall withstand 4 h fire exposure.
No indications about blast pressure, indeed. My opinion is the Fire Wall should resist the local conditions. For instance, in hurricane region for a maximum of 200 mph speed, wind the pressure will be 90 psi [usually is less than 10 psi].
The effort due to earthquake is also a criterion.
The old Code of Federal Regulation [CFR30], based on investigation of underground coal mine stated 20 psi for a seal structure [in case of methane-air mixed explosion]
The new Code could state 130 psi -see the draft:

http://www.cdc.gov/niosh/review/public/MineSeal/pdfs/MineSealDRAFT.pdf

The experiment described in this Draft was conducted in a closed enclosure. In the substation outdoor case it is only a confine area [no roof] so I think 20 psi blast wave pressure will be fair.