For a jacketed vessel with a vacuum inside the inner cylinder and positive pressure outside, why is the test pressure for the inner cylinder taken as only 1.25 times -0.1?
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For a jacketed vessel with a vacuum inside the inner cylinder and positive pressure outside, why is the test pressure for the inner cylinder taken as only 1.25 times -0.1? I’ve been thinking about a problem recently: when performing a pressure test on the inner cylinder using external pressure, why isn’t the risk of instability under positive pressure on the outer cylinder taken into account? Although there are calculations to assess this, instability due to external pressure is after all more likely to occur than failure due to internal pressure strength. So, is it possible that the inner cylinder passes the pressure test without issues, but loses stability when the outer cylinder is pressurized? That would be troublesome, wouldn’t it? Do we need to take it apart again? If pressure holding is involved, the working pressure inside the inner cylinder is negative – how can pressure be maintained in such a situation?
I think it’s not appropriate to conduct internal pressure tests on external pressure vessels; why isn’t a correction factor added?
For the instability under positive pressure in the outer cylinder, verification calculations are carried out, which takes into account instability due to external pressure. What should be done according to your suggestion?
During the jacket test, the inner cylinder can maintain pressure
The inner cylinder is under vacuum while the outer cylinder is at positive pressure; therefore, the pressure acting on the inner cylinder should be the positive pressure of the outer cylinder plus 0.1, and then this value is multiplied by a coefficient. I’m not sure if I understand correctly
The purpose of the hydrostatic test for externally pressurized vessels is not to verify stability, but to check the sealing performance
When the outer shell is under pressure, the inner cylinder must also be kept under pressure; the specific pressure level required depends on the pressure applied to the outer shell, as long as it does not exceed the maximum pressure difference that occurs during normal operation
Later, I read the explanation for 150, which stated that as long as the instability of the inner cylinder is calculated based on external pressure, it will definitely meet the requirements. I think this interpretation is not appropriate; in other words, if it is calculated at 150, it won’t become unstable, so it definitely won’t lose stability. Have all the instability accidents caused by manufacturing, etc., been ruled out? Unless it is the instability condition we calculated, the safety factor is very high.