Allowable pressure drop for Swing check valve during seat pressure tes

[gafoorkti]

Please can somebody tell me about allowable pressure drop for Swing check valve during seat pressure test.

Descrption and test result: 1" class 150 Swing Check valve (Al-Bronze)has been pressure tested as per data sheet which refers to seat test pressure 20 Bar and acceptance criteria to Api 598.
During the seat test at 20 Bar, minor leak was observed (1 ml/min) and pressure was reduced to 17 Bar and then stabilized.
Since the subject valve is metal seated type, observed leakage (1 ml/min) is acceptable, however issue regarding the pressure drop created ambiguity in us.

Please advise me.

 

[zdas04]

That is something for the engineer who wrote the acceptance criteria to address. There is not a number in the code as far as I've been able to find. You need to determine the impact of a leak and determine how big a leak will still result in acceptable process performance.

David

 

[israelkk]

To my opinion your test fixture should automatically compensate for the pressure drop and raise the pressure before the valve until it stabilized on the 20 Bar if case there is a leak. Then measure the leakage.

 

[gerhardl]

My opinion: Both zdas04 and israelkk has given you the correct answer: the test has to be done with leakage at a steady 20 bar upstream (overpressure?- as given in test description!) as described by israelkk.

If this leak (after measurement at 20 bar) drops the P1 pressure to 17bar and stabilizes (under what flow conditions and reservoir amount before the valve?) this is quite another thing to be considered. (zdas04)