Pneumatic Testing for valves in Gas Service
Pneumatic Testing for valves in Gas Service
(OP)
When producing valve data sheets (Ball, Gate & Globe) and specifying that pressure testing should be in accordance with API 598 and BS 6755 Pt1, I believe I should specify whether a pneumatic seat test is required. Is there a standard that recommends what services a pneumatic seat test is indeed required for? For example, why is it that Gas would require a pneumatic test but plant air wouldn't?
Talk To Other Members
RE: Pneumatic Testing for valves in Gas Service
3 types of pneumatic test are used generally. The low pressure seat test, and the 110% seat test, and a high pressure body test.
Low pressure seat tests are used to test seats at low pressure differential, and where seating is obtained by a spring. Some valves will pass a high pressure seat test, as the pressure assists in seating the valve, whereas at low pressure the spring in the dynamic seat arrangment may not be adequate to get a good seal.
High pressure seat tests are usually required in hydrocarbon gas services, as a hydrotest is not really reprensentative of the service fluid the valve will be subjected to. This test can be dangerous, and should be done after all hydrotesting has been successfully performed and in a safe manner.
high pressure body tests are usually performed using a test fluid of 99% Nitrogen, 1% Helium. this is a very searching test, and normally enforced on valves in critical lines.
All tests add cost to the valve. This is an unnecessary expense for a plnt air valve, but essential for an ESDV.