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Test procedure for butt weld end valve

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PAN

Mechanical
Apr 25, 2001
549
SG
I would like to know the shop procedure for hydrostatic test butt weld end valve as per API 598. This procedure should be more difficult than flange end valve. Do the manufacturer weld and cut the spool after pressure testing? Do they carry out PWHT after testing low alloy steel valve body? Anyone who has experience in valve factory please advise me.
 
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I've seen two methods. The first is to put an o-ring seal just inside the bore on each end. The second is to press the valve between two rubber plates. The second method is not prefered since the compression can hide small cracks/porosity in the body.
 
WELL!

This is the information I got from a hectic web search.Hope it helps!




INSPECTION AND TESTING:-
For a individual valve to be pressure tested to API 598/BS 6755 Part 1 requirements are:-

TEST PRESSURES FOR STANDARD VALVES
ASME * Hydrostatic test pressure
CLASS
Shell BackSeat Closure

150 psig 450 315 315 100
kg/cm² 32 22 22 7
300 psig 1125 815 815 100
kg/cm² 79 57 57 7
600 psig 2225 1630 1630 100
kg/cm² 156 115 115 7


The last column values are for pneumatic low pressure closure test.

Low pressure test for Swing Check valves:
In addition to the high pressure closure test, Swing Check valves are subjected to low pressure hydrostatic closure test at a pressure of 25% of the high pressure closure test The duration of the test is the same as for the high pressure closure test.
 
In general a test bung with an 'O' Ring is used and the bungs on both ends of the valves are clamped together before applying pressure. This is very effective and proven methodology.

Also, for buttweld end valve, since radiography is mandatory the standard allows you to offer them as special class valves with higher working pressure. Refer ASME B16.34

Hope this answers your query.

Regards

manian
 
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