Regarding valve pressure testing and sealing issues
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According to the standard GBT 26480-2011 \"Inspection and Testing of Valves\", I recall that in previous projects we used water for high-pressure sealing tests; however, the current standard requires low-pressure sealing as well as air leakage testing. Can high-pressure water testing replace low-pressure air testing? Were we all wrong before?
Can we just go with the higher one and not the lower one?
Put simply, as long as the pressure isn’t so high as to cause damage, it can be sealed. Low pressure presents more challenges; API 6D and API 598 specify a maximum pressure of around 5 kilograms for low-pressure applications. In other words, ordinary ball valves do not provide proper sealing at pressures below 5 kilograms
For some valves, during pressure testing, the higher the pressure applied, the better the sealing performance. The pressure of the fluid forces the moving parts to press against the sealing surface at the outlet end; the greater the pressure, the better the seal. At low pressures, this thrust is very small; sealing is primarily achieved through the pre-tightening force of the spring or the valve itself. If the pre-tightening force of the valve is insufficient, leakage will occur even at low pressures. . The most typical example is the check valve: during pressure testing, the higher the pressure applied, the less likely it is to leak, while it will leak almost 100% at low pressures. We specialize in gas valves, and some of our clients require no leakage even at low pressures of 0.2 MPA.
At this point, you need to force-seal the valve. We manufacture forced-sealing valves, and it has nothing to do with the pipeline pressure; they can work under any pressure level