The post-weld heat treatment of steel pressure vessels should be carried out before the pressure test
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Why should the post-weld heat treatment of steel pressure vessels be carried out before the pressure test?
The purpose of post-weld heat treatment for pressure vessels is mainly to relieve stress or restore the mechanical properties of the material. The pressure test is a destructive test; if the equipment has high residual stresses or its mechanical properties have declined during manufacturing, it can actually be damaged during this test.
Heat treat first, then conduct the pressure test?
What if the experiment goes wrong first? . . Heat treatment is a manufacturing step, while pressure testing is an inspection step after manufacturing is completed. It needs to be manufactured first before it can be inspected, right?
The pressure test is the final inspection after the manufacture of pressure vessels...
That’s correct; all processes that affect (weaken/reinforce) the pressure-bearing capacity of the container must be completed before the pressure test.
The final inspection (verification) can only be carried out after manufacturing is complete.
For safety reasons, heat treatment is used to eliminate residual stresses, as there are certain risks associated with conducting pressure tests first.
The purpose of post-weld heat treatment is to eliminate welding residual stresses and improve the microstructure and properties of the welded joint. The presence of welding residual stresses accelerates the growth of existing defects as well as the formation of new ones. In such cases, performing pressure tests can easily lead to the destruction of the container; therefore, post-weld heat treatment should be carried out first.
Heat treatment is intended to eliminate residual stresses; what if something breaks during the pressure test if those residual stresses are not removed?
After heat treatment, the container still needs to be cleaned, and the pressure test is the final inspection step after painting.