Questions about manual gate valve sealing test and internal leakage
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There are now a batch of 304 stainless steel manual gate valves, including class150 and class600 pressure levels, sizes DN15~DN150, which have been installed on the equipment. Now during the pressure test, it is found that some gate valves are leaking after they are all closed, as shown in the picture below. The test pressure of the class150 gate valve is 1.1Mpa, and the test pressure of the class600 gate valve is 4.2Mpa. When I asked the supplier, he said that the air seal test of their valves is in accordance with API. 598 is 0.6Mpa, which means our working pressure exceeds their test pressure. What I want to ask is, is there any relationship between the leakage of the air seal test pressure and the leakage under the working pressure? According to him, is it possible that internal leakage will occur if the working pressure of my class600 gate valve exceeds 0.6Mpa? I hope professionals can answer this, thank you very much!
Leakage must be the supplier's problem. Needless to say, the 0.6 is just to suppress the safety of workers. No matter what your design pressure is, I only dare to set the air pressure to 0.6. If you perform high-pressure air sealing experiments, you need good protection measures. Generally, 0.6 can ensure the air tightness of the valve. Yours is a bit special, but this is definitely not your responsibility.
Don't let the manufacturer talk nonsense and replace it quickly. 0.6 is the pressure for the low sealing test. If the high sealing test is not done, the manufacturer is responsible for the leak. Such manufacturers will be directly blacklisted.
I really don’t dare to say how well this valve performs. If there is leakage at the lower port of the gate valve, you can try to use the booster rod to close the lower handwheel and check the situation. Although the inspection standard has relevant regulations on low-pressure sealing test 0.6, manufacturers often use 1.6MPA during the sealing test to see if the seal will leak.
The leakage level is a bit low and does not meet factory standards.