Relief scenario - mechanical PCV failure
Relief scenario - mechanical PCV failure
(OP)
Hi everyone,
I would appreciate advice on the following:
I am currently producing datasheets for some N2 relief valves. I have analysed the system and decided that the governing case for relief sizing is the scenario where the mechanical PCV (pressure reducing valve) upstream of the relief valve fails.
The Supply to the PCV is 5 barg and is normally reduced to 0.5 barg. The relief valve is to be set at 0.6 barg. This means that when the PCV fails, the governing flow will be that produced in the system by a pressure drop of 4.4 bar (supply pressure - relief valve set pressure).
My query is - how do I simulate the effect of the PCV presence in my pressure drop calcs? Even though the device has failed, it will still have some effect wrt resistence to flow, given it is still present in the line.
Can I assume a K valve, or is it typical to assume it has the same effect as an orifice for example?
Many thanks for any help!
I would appreciate advice on the following:
I am currently producing datasheets for some N2 relief valves. I have analysed the system and decided that the governing case for relief sizing is the scenario where the mechanical PCV (pressure reducing valve) upstream of the relief valve fails.
The Supply to the PCV is 5 barg and is normally reduced to 0.5 barg. The relief valve is to be set at 0.6 barg. This means that when the PCV fails, the governing flow will be that produced in the system by a pressure drop of 4.4 bar (supply pressure - relief valve set pressure).
My query is - how do I simulate the effect of the PCV presence in my pressure drop calcs? Even though the device has failed, it will still have some effect wrt resistence to flow, given it is still present in the line.
Can I assume a K valve, or is it typical to assume it has the same effect as an orifice for example?
Many thanks for any help!





RE: Relief scenario - mechanical PCV failure
I2I
RE: Relief scenario - mechanical PCV failure
Hope this helps
Regards
RE: Relief scenario - mechanical PCV failure
I have managed to find vendor data for the PCV (a Norgren PCV) and so will contact them wrt the Cv value.
The amount of information stored locally seems very scant, so originally I wasnt sure if there would be any vendor info - thought could maybe estimate/approximate the effect as per an orifice or similar.
Thanks again, you have been a great help.
RE: Relief scenario - mechanical PCV failure
JoeWong
Chemical & Process Technology
RE: Relief scenario - mechanical PCV failure
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Thanks Joe - a check for sonic velocity/choking will be included.
Many thanks!