Chattering of Safety Valve based on oversizing
Chattering of Safety Valve based on oversizing
(OP)
We are procuring PSV from one of reputed vendor where there is a remarkable difference between effective and actual discharge of orifice.
Vendor has selected "R" type orifice as per API520, with effective discharge area as 10322mm2.
However actual discharge area for the same is specified as 12668mm2.
How we can check and ensure that there will be no chattering due to this difference. Vendor is silent on this. Is it not vendor's area of responsibility?
Can anyone provide guidelines about Chattering of valve for above reason.
Vendor has selected "R" type orifice as per API520, with effective discharge area as 10322mm2.
However actual discharge area for the same is specified as 12668mm2.
How we can check and ensure that there will be no chattering due to this difference. Vendor is silent on this. Is it not vendor's area of responsibility?
Can anyone provide guidelines about Chattering of valve for above reason.





RE: Chattering of Safety Valve based on oversizing
RE: Chattering of Safety Valve based on oversizing
RE: Chattering of Safety Valve based on oversizing
Per API 520, the effective orifice area is used for initially sizing the PSVs, However, many
PSVs' certified area are presented in ASME actual orifice area.
There are some correlation between API effective discharge and ASME actual discharge:
A(api)= K(ASME) x A(ASME) / K(API)
A(api): effective orifice
K(ASME): actual discharge coefficient
A(ASME): actual discharge area
K(API): effective discharge coefficient
SO you cant compare effective discharge (R orifice) with actual discharge (12668mm2) in this way. you should ask the PSV manufacturer to provide you their equivalent effective discharge area. Generally the equivalent effective discharge area by PSV manufacturer will be slighter bigger than API calculated result.