Is stress verification required for ASME hydrotesting?
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GB150.1 4.6.3 states that if a test pressure higher than the specified value is used, the stress levels of all pressure-bearing components under the test conditions shall be checked prior to the pressure resistance test. The maximum overall membrane stress during the hydraulic test shall be less than or equal to 0.9 times the yield strength of the material at room temperature multiplied by the weld joint factor. For ASME, UG-99 does not state that a stress check of the material is required when the hydrostatic test pressure is higher than the specified test pressure. For example, my design pressure is 10 MPa, and the MAWP is also set at 10 MPa. Then, as required by UG-99(b), the pressure for the hydrostatic test should be 13 MPa. However, the project requires a pressure of 1.5 times the normal level to conduct the hydrostatic test. Do I then need to perform a check based on a 90% yield strength for the material? Where are the specific requirements in ASME? Of course, if I use a 1.5 times hydrostatic test, it’s no longer UG-99(b).
According to ASME standards, the pressure for hydrotesting is typically set in accordance with the requirements of UG-99(b), namely 1.3 times the maximum allowable working pressure (MAWP). In your example, the design pressure is 10 MPa, so the test pressure should be 13 MPa. However, you mentioned that the project requires a hydrostatic test pressure of 1.5 times the normal value, That is, 15 MPa. Although this exceeds the standard requirements of ASME, it does not mean that you need to perform a 90% yield strength check on the material. In fact, the ASME standards do not require stress checking in such cases. However, for safety and conservative reasons, you can choose to perform stress checks on the materials and connectors. In this case, you can refer to the requirements of GB150.1 4.6.3 to ensure that the maximum overall film stress during the hydraulic test is less than or equal to 0.9 times the yield strength of the material at room temperature multiplied by the weld joint factor. This ensures that the safety of the equipment is fully guaranteed during the hydrostatic test at 1.5 times the pressure. In summary, although ASME standards do not explicitly require stress checking when the test pressure exceeds the specified value, you can still choose to conduct such checking based on the specific requirements of the project and safety considerations. For specific operations, refer to the relevant provisions in GB150.1 4.6.3. .
So, how is the verification actually carried out? According to ASME VIII, Volume I, verification is not done using a minimum yield strength of 90%; in Volume II, it is done using 95% as the standard.
Is it true that there’s no requirement for verification – it’s simply considered a write-off and that’s that?
Regarding overseas projects, there is no requirement to use national standards in terms of design criteria; in my calculations I use UG-99(c). For PVelite, it’s sufficient as long as the requirements are met. If I want to conduct stress checks, I can refer to national standards or the methods outlined in Volume VIII II for stress assessment of materials, but it is specified that Volume VIII I should be used, and these stress assessment methods can only serve as a reference. That’s the case, right?