ASME FIRE REQUIREMENTS FOR PSV 1

[jrwchem]

ASME VIII states that a 21% overpressure should be used for fire or other unexpected sources of heat. I usually see "fire" interpreted as meaning a pool-fire.

Does anyone have any examples of "unexpected external sources of heat?" Any example specific to refineries that you have designed for in the past?

thanks.
Jonathan

 

[pleckner]

Great question because I've been thinking of this myself.

(a) Perhaps you can consider radiation heating from a fire that is normally outside the API fire zone, or from the atmospher.

(b)Perhaps you have a jacketed vessel normally on cooling fluid but has a cross-over for whatever reason to a steam line. Steam gets into the jacket, that sounds like an unexpected external (to the vessel) heat source to me.

(c) A possible failure in the wall of a fired heater nearby an exposed vessel (maybe streatching this one a bit).

I'd be interested to see what others may come up with.

 

[jrwchem]

Pleckner,

I am glad to hear this question has made other people wonder as well. The only source of external heat that i have ever seen a relief load calculated for is for pool fires. Jet fires are not generally protected against with PSV (per API 521).

Jonathan