Issues related to the testing medium for the tightness of high-pressure urban gas pipelines
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Recently, there was a city gas high-pressure pipeline project with a design pressure of 4.0 MPa. According to the Code for Construction and Acceptance of Urban Gas Systems CJJ33, air should be used as the testing medium for checking airtightness. The construction contractor has proposed that, given the rural areas through which certain sections of the route pass and the high level of activity among the people living there, it is dangerous to use gas for integrity tests; therefore, water pressure is intended to be used instead. According to the construction acceptance specifications for long-distance pipelines, water can be used for the tightness test. Of course, given that higher safety standards are required for city gas compared to long-distance gas transmission, such high requirements are understandable. Experts on the forum, do you think hydraulic pressure can be used as a substitute for air pressure in terms of precision?
Something seems off to me; you must be referring to a strength test. Your parameter strength test is a 1.5P hydrostatic test. The tightness test is carried out after the strength test, as a 1.15P airtightness test. The provisions do not state that a strength test can replace a tightness test; in fact, GB 50235 explicitly requires that flammable media must undergo a leakage test. As for the construction acceptance specifications for long-distance pipelines, you are referring to GB 50369, right? But even in the case of GB 50369, air is used for the integrity tests, although the test pressure is the design pressure. From the perspective of the purpose of tightness testing, I don’t think using water for testing will be effective; water has greater surface tension than air, and the fact that there is no leakage of water does not mean there is no leakage of air. Moreover, if one doesn’t even dare to conduct the tightness tests according to 1.15P of CJJ 33 or 1P of GB 50369, I don’t understand how the owner can afford to put the pipes into operation.
Thank you for your guidance. It’s a tightness test; for pressure testing in long-distance pipeline projects, water can be used as the medium for both strength tests and tightness tests.
It is indeed possible, as the standards use “should” instead. So I feel this isn’t a technical issue, but a communication issue. What you need to ask is whether the owner and the special inspection agency agree to use the water tightness test. It is also necessary to check whether the design specifications provided by the design agency include requirements for integrity tests.
This post was last edited by yujwlhh on 2019-11-8 09:30. Integrity tests and airtightness tests are two different things; after the strength test of gas pipelines, a gas leakage test is still necessary, right?
Yes, the testing contents for each drop are different