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Required flow capacity for a water storage vessel, fire case

Required flow capacity for a water storage vessel, fire case

Required flow capacity for a water storage vessel, fire case

Hello all,

I am trying to size a relief valve for a water storage vessel for fire case. Normally I would use CGA s1.2 for ammonia and use posted Gi/Gu values. But let's say there is only water in the vessel. I want to size a valve for fire case where water boils and turn into steam and steam needs to get out of the vessel.

surface area = 400 sq.ft
Set pressure 80 psig

I would appreciate any help.


RE: Required flow capacity for a water storage vessel, fire case

I don't know of your design codes or local requirements, but a good place to start for what you're describing is API-521. There is a whole section there of determining a flowing relief rate based on a liquid filled vessel exposed to an external fire. You will need to know the wetted area, latent heat of vapourisation of the contained fluid, the insulation (or not) of the vessel etc., etc. Once you calculate a flow, you would then use that in a pressure relief valve sizing program like API-520 to carry out initial sizing.

Hint: You may want to use a PRV vendors program that will require all inputs to determine flow and then size.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

RE: Required flow capacity for a water storage vessel, fire case

First, need to clarify the type of equipment you have to be protected, i.e. pressure vessel or steam boiler, which may require different regulation for sizing and type of PSV valves.
Then, you may work with a PSV vendor for PSV type and sizing based on the vessel design condition and overpressure cases.
But IMO, it seems that the overpressure of a "water" vessel for a fire case may not the realistic condition.

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