VALVE TESTING
Another designation could be established for life tests , as per the example in the table below :
Category N A B 5000
Life cycles under rated pressure Not done
C 10000 D
Category 0 0 1 1 2-5 2 6-10 3
1000 or less
50000 or more
Number of samples tested
Life test qualification may then be indicated , for example , as N1 , C2 , etc . The N0 designation is included to be comprehensive and used for one-off special valves ; they may , of course , be tested in a production test .
Production tests
1 . Test for body integrity for pressure containment .
Protype tests Seat leakage : Life test : Production tests Fluid pressure holding integrity at 15 bar : Fluid containment integrity at 15 bar : Operation test for FIVE cycles :
Class B Class B2
PASSED
PASSED
PASSED
2 . Test for body integrity for fluid containment .
3 . Test for operational fitness - to identify any rare manufacturing defects that may affect operation . For ( 3 ), a test of , say , five on-off cycles could be set as the norm . The test would involve only operating the valve from open to close five times . This should detect any production defects affecting full closure , if any , that were not detected earlier . In conclusion , manufacturers could ship valves with a compliance certificate and valve tag plate stating , for example , the following : In short , the proposed protocol removes seat leakage testing from production tests in the existing system and adds an operation test , while a life cycle test is added to the prototype testing . Prototype tests should ideally be conducted by the manufacturer with a thirdparty agency witness and certification for credibility . Production tests can be performed by the manufacturer and selfcertified ; witnessing by a user / third-party inspector can be optional . If adopted , a protocol as described in this article would present the user with more useful and relevant data on the valve while also saving time , effort , and money currently spent on seat leakage testing .
About the author S . Vijayakrishnan , Ph . D . in Chemical Engineering , is a retired valve industry veteran with a three-decade career at DeZURIK , VAAS , Habonim and Bray . Post-retirement , he continues contributing to the industry as an author of internationally published articles on valves , particularly knife gate and slurry valves . He lives in Chennai , India and can be reached at vijykrishnan @ gmail . com .
24 Valve World September 2024 www . valve-world . net