Fire Case - Tank Area
Fire Case - Tank Area
(OP)
For a horizontal tank that is more than 1/2 full (say 2/3), what area should be assumed to be exposed to a fire from below? Only the bottom half? Thanks, bill
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RE: Fire Case - Tank Area
If the level is 25%, the wetted area corresponds to 25%.
One has to ajust for liquid swell.
If the level is 25% AT AMBIENT, the level will expand at actual relief temperature.
Something like hexane can expand alot and can cause problems.
If one starts with 85% level, the swell may expand to 95-100%. Two-phase flow calculations would be triggered.
RE: Fire Case - Tank Area
To bring this to a conclusion then, if I have a vertically mounted cylinder that is completely full, I should count the very top of the tank in the area calculation? For the sake of discussion, forget about swelling and two phase flow.
RE: Fire Case - Tank Area
There is a concept of flame height associated with wetted area.
The exact flame height depends on standard being used.
I believe API uses 25-ft for low hazard process areas and 50-ft for high hazard process areas.
For tank farms 30-ft flame height is used.
Eurpoean folks use 10-meters.
NFPA has something different depending on the situation.
If the bottom of a 10-foot verticle tank was 23-ft above grade, the wetted surface would correspond to 2-ft assuming the 25-ft flame height standard
RE: Fire Case - Tank Area
RE: Fire Case - Tank Area
You said "Eurpoean folks use 10-meters". COuld you please give us your source?
Thanks
"We don't believe things because they are true, things are true because we believe them."
RE: Fire Case - Tank Area
Bill,
If you are a subscriber at Che.com [or receive Chemical Engineering Magazine] there is a great article for calculating wetted areas for partially filled horizontal vessels.
Doane, R.C. "Accurate Wetted Areas for Partially Filled Vessels." Chemical Engineering Magazine, December 2007. pp 56-7.