Discussion on the leakage level of valve seats
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This post was last edited by brober on 2023-2-2 11:27. Hello everyone! I have always had a question: there are many standards for the leakage levels of valves, such as API 598, FCI 70-2, etc. Each standard specifies corresponding leakage levels, testing methods, and the maximum acceptable amount of leakage. For example, the test pressure specified in FCI 70-2 is 3.5 bar, and the maximum allowable leakage amount is also based on this 3.5 bar value; however, many valves actually operate at pressures much higher than 3.5 bar, such as 30 bar. Is then the maximum allowable leakage amount for this 3.5 bar test also applicable to the 30 bar case? Based on my practical experience, the leakage rate is acceptable at 3.5 bar, but it exceeds the limit at an operating pressure of 30 bar.
This post was last edited by feng*aosa on 2023-2-4 at 16:48. ● Leak level, leakage volume level, and test pressure are three different concepts. ● Regarding the leakage level categories and their testing methods, national standards as well as commonly used foreign and international standards are largely similar. Note: What is referred to here is the leakage level; that is, leakage levels under different standards may be the same, but due to differences in testing methods (pressure), the actual leakage levels vary. ● Different standards result in varying experimental pressures corresponding to the same leakage level (the same leakage amount level, but different experimental pressures). For example: GB/T 13927-2008 \"Industrial valves – Pressure testing\", GB/T 4213-2008 \"Pneumatic control valves\", FCI 70-2-1998 (ASME B16.104) \"Leakage of control valve seats\". \"Maximum rated pressure difference or 3.5 bar\"; in China, a leakage test pressure of 0.35 MPa is commonly used, primarily due to the experimental requirements specified in national standards for control valves as well as certain construction standards. In fact, most domestic and imported control valves these days use the maximum operating pressure as the pressure for leakage testing. In my opinion, it is generally difficult for the project owners to establish uniform requirements for leakage testing of control valves; at most, they may require that testing be carried out \"in accordance with the valve’s technical specifications\" or something similar. But I’m being lazy and not listing the “valve technical requirements” one by one. The construction party, wanting to avoid hassle, simply uses 3.5 MPa in all cases. In the end, it seems as though the leakage rate corresponds to 3.5 MPa. That’s not really the case. ...