Air-tightness testing issues for pressure pipelines
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I seek guidance from experts! 1. For the airtightness testing of pressure pipelines, **are there any relevant specifications or standards? 2. What is the pressure retention time for the airtightness leak test? Is it related to the pressure rating? 3. When performing a gas-tightness leak test, are proper gaskets being used? 4. The gasket specified in the design is a graphite wound gasket; is it possible to achieve zero leakage during the airtightness test? 5. The actual pressure during testing reached 2.5 MPa, and leaks occurred in several graphite wound gaskets (carbon steel flanges). Was it due to an incorrect selection of gaskets?
The pressure is high; check whether the selected sealing grade is sufficient. As mentioned above, the leakage may be due to a poorly fabricated flange sealing surface, or improper installation of the gasket. The gasket is broken, or the sealing grade of the flange gasket does not meet the requirements
Generally, a hydrostatic test is used to check whether there are leaks in the welds, while a gas test is employed to determine if there are leaks at the flanges. If a leak occurs at a flange, first it is necessary to check whether the sealing surface of the flange has been damaged, which could lead to poor sealing; secondly, it is important to ensure that the bolts are tightened diagonally so that the force is applied evenly
Apply soapy water to all welds and joints for inspection; no leaks are considered acceptable.
First, there’s something that needs to be clarified: airtightness testing checks for leaks, while water pressure is used at 1.15 times the value to test the equipment’s capacity to withstand pressure. You can set your own standard for airtight leakage; it’s not about whether there is one bubble or several bubbles. Rather, what is the pressure drop over what time period