The purpose of stress verification in the pressure testing of internal pressure vessels
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For pressure vessels, the test pressure is specified, and then a stress check for the pressure test is provided. I would like to ask what the purpose of this stress check is; does it mean that if the value does not satisfy ≤0.9*weld joint factor*yield strength, then a pressure test cannot be carried out? If it doesn’t meet the requirements, does that mean the container manufactured is defective?
When the design temperature of the container is high, the test pressure obtained using the formula for calculating test pressure may be much higher than the design pressure; conducting a pressure test at this pressure could result in the film stress within the shell reaching or approaching the material’s yield limit. The purpose of performing stress verification is to prevent unnecessary accidents during pressure testing due to insufficient strength of the shell. If the stress check is not satisfied, the designer should increase the wall thickness or reduce the test pressure; this has nothing to do with whether the manufacturing is qualified or not.
Reply to 2# nyfdhb: Thank you, but the wall thickness is calculated using formulas. If the stress check does not meet the requirements, can we simply increase the wall thickness without any basis? How is the increase amount calculated?
It is necessary to increase the wall thickness, with the amount of increase determined by the requirements of the pressure test.