High-pressure stop valve sealing test
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Dear experts in this forum, I’m seeking help. I currently have a DN50 stainless steel bellows globe valve, PN100, which the customer uses in hydrogen pipelines. Now, the customer has detected internal leakage during the sealing test. The test gas is nitrogen, with the pressure increased to 60 kilograms. According to the **standards**, for gas sealing tests (low-pressure sealing), the test pressure is 0.6 Mpa; for water pressure sealing tests (high-pressure sealing), it is 1.1 times the design pressure, which in this case is 110 kilograms. So, this high-pressure stop valve will now be used with hydrogen as the working medium; the customer conducted a sealing test using nitrogen and pressure was applied up to 60 kilograms at which point leakage occurred (although this is very dangerous and would result in issues being detected). Yet **the standards specify that only 0.6 Mpa is required – how can this be explained? On my end, the gas seal can be set to 30 kilograms, and the water seal can be set to 110 kilograms without any problem. Help, please! It’s urgent – experts, please help.
Also, the contact surface shows no wear
I really have no concept of a unit like kilogram
Airtightness is used to detect leaks and the condition of seals. Suppression is a stress test. For special requirements, airtight pressure testing can be used, but it is very dangerous.
So what if hydrogen is used later and the pressure reaches 50 to 60 kilograms? After all, the airtightness test using nitrogen at 6.0 Mpa already showed leaks
Help out, please: @jacques0920 @*nht1 @ylb913 @ValveMingMing @WiseManMing @*lihuagong
What is the leakage rate of the internal leak? I can’t provide a professional answer to this question; let’s talk instead about our hydrogen pipeline with a pressure of 6.0 MPa. We used Samson valves, and there was a slight leakage. Then the technicians in charge along with the manufacturer’s representatives started discussing the issue. The manufacturer’s representatives said that slight leakage is inevitable, as long as it falls within the acceptable limits (different sealing grades correspond to different levels of leakage). They then calculated our current level of leakage and stated that it meets the relevant standards. I’m still arguing with the manufacturer about this issue. . .
First of all, I can’t do this; I’ve never been involved in such high-pressure airtightness tests. I can only use this as an opportunity to suggest that since there are no standards in China, you should look into other standards.
What is the design pressure of the pipeline in which this valve is located? The test pressure for the airtightness test must be the design pressure; any test conducted at a pressure lower than the design pressure is ineffective. The hydrostatic test is only a strength test; a leak test for flammable and explosive gases is necessary. Don’t bother trying to explain – there’s definitely something wrong with these valves; replace them right away. If problems arise during operation, you’ll be in big trouble