How to verify the stress levels of various stressed components under test conditions prior to the voltage withstand test?
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How should we understand the situation where the pressure value for the pressure resistance test is higher than the specified test pressure? Should the stress levels of all stressed components under the test conditions be checked prior to the pressure resistance test? In item (a) of point 4 on page 47 of the interpretation of standard GB150.1-2011, it is stated that the verification of other types of pressure-bearing components shall be carried out using the corresponding calculation formulas in GB150.3. I have summarized it as follows: 1. The formula for calculating the stress in the cylinder body can be either equation (3-3) or (3-4) on page 94 of GB150.3-2011; the criteria for making such calculations can be found in clause 4.6.3 on page 15 of GB150.1-2011. 2. The formula for calculating the stress on end caps can be found in equation (5-3) on page 117 of GB150.3-2011; the criteria for judgment can be referred to in clause 4.6.3 on page 15 of GB150.1-2011. 3. Other pressure-bearing components: For example, it’s unclear how to calculate pressure-bearing components such as tube sheets and equipment flanges; what formulas should be used? How should one refer to when determining stress?
The standard does not specify this; a case mentioned in the book written by Teacher Faye Wong shows that the solution is to artificially increase the design parameters so that the test pressure required for testing according to the standard is reached (that is, it corresponds to the situation where you need to increase the pressure), and then it’s fine. Although this may waste materials, it is the most practical approach for now.
Thank you. One more question: in version 3.1 of SW6-2011, when entering the main design parameters, can one input the hydrostatic test pressure manually? However, in the heat exchanger calculations, I entered the hydrostatic test values myself, and found that the calculated stress on the tube sheet was still based on the design pressure. Could it be that the tube sheet was not subjected to verification under the test pressure conditions?
SW6 is developed in accordance with standards; if something isn’t covered by those standards, it certainly won’t be included in SW6.
I can go into detail about the advantages.
It is to increase the design pressure so that the specified pressure test value does not exceed the value calculated by the standard formula; in that case, no further verification is required. I’m not sure if this is the original intention.
These are the only options available, yet they do not violate the regulations. The only drawback is the waste of material.
Under normal circumstances, the pressure for the withstand voltage test is determined by the designers; we have never encountered a situation where the test pressure was artificially increased.
Customers can request it, and it is indicated on some drawings, but designers generally do not increase it. When the customer requests it, the designer must verify whether this pressure is appropriate and whether the strength under that pressure is sufficient.
I haven’t encountered any situation where a client specified a test pressure; of course, that doesn’t mean it’s not allowed. What is the user’s purpose? If considered from a system perspective, the design pressure should be increased accordingly.