Questions regarding the hydrostatic test of the shell
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Why, during the shell hydrostatic test, it is only necessary to verify the maximum overall membrane stress of the shell components. And instead of using the hydrostatic test pressure as the design pressure, and changing the design temperature to the hydrostatic test temperature, should we use the formula for calculating thickness for verification? If the hydrostatic test pressure is artificially increased, how should the reinforcement at the nozzles and openings on the shell be checked? Is it by changing the design pressure to the hydrostatic test pressure and the temperature to the test temperature in order to verify the reinforcement for openings?
A hydrostatic test is used to assess the overall strength of a container by applying a pressure equal to 1.25 times the design pressure at the operating temperature of the equipment, and maintaining this pressure for more than half an hour, with adjustments made to account for the properties of the material. This is an overpressure test that takes into account factors such as safety factors and the material’s yield limit; it is a short-term test under conditions exceeding those of the design. If designed in this way, the equipment will be safer, but the cost will be higher; therefore, there is no need to use a taller design. This is originally a superpressure test, and no additional calculations are required for any structures.
The stress during the withstand voltage test is calculated based on the thickness after deformation; the calculated pressure is changed to PT, and the calculated thickness is changed to the effective thickness
I just reversed-engineered the formula, and it works as you said. The question now is why the calculated film stress is required to be less than 0.9 times the yield strength, multiplied by the welding factor ； Instead of requiring it to be less than the allowable stress?
Another question is regarding the hydrostatic test (including artificially increased hydrostatic pressure): is it necessary to conduct a verification for the reinforcement of the openings in the pipes? How to verify?
No, it’s not necessary, and it hasn’t been verified either.