Strength calculation of reused pressure vessels
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Dear forum members, when calculating the strength of used pressure vessels, due to changes in standards, the allowable stresses for materials differ between the old and new standards. So, should we use the allowable stress according to the new standard or the old standard when calculating the strength?
New standard! If the material does not meet the new standards, it is recommended to discontinue its use! Whether to use it or not requires a comprehensive evaluation!
Using the standards adopted at the time of design
Refer to Clause 8.3.11 of TSG 21-2016
When it comes to reused pressure vessels, the first thing to consider should not be merely the strength verification; rather, it’s important to check whether there are any recent inspection reports. The damage that may occur during use is difficult to estimate... For pressure vessels of a certain category, strength verification based on the original design drawings will likely show they meet the requirements. What’s concerning is the possibility that the equipment already has hidden defects when it’s reused, such as material creep or a reduction in effective thickness... Returning to the topic, for reused pressure vessels, strength should be verified using the original design drawings, and in addition, it’s also necessary to conduct calculations according to the latest standards. If they meet those standards, then there’s no problem. If they don’t meet the new standards, further consideration needs to be given as to whether they can still be used. After all, the allowable stress values in the standards generally don’t change; if they do increase, that’s understandable, but if they decrease, it’s likely due to changes in the quality of the materials used in their manufacture
Previously, a colleague repaired an old pressure vessel; it was originally classified as category two, but according to current standards it falls under category three, and it was ultimately treated as such
It can follow the standards used during the original design.
What was said on the third floor is correct. If pressure vessels are being used and strength verification is required, then the original design specifications must be followed ；
How old is it, to what extent? 10 years, 20 years? I’ve seen equipment that came from Japan in the 1970s still in use; when there were problems with the pumps, we asked them to repair them. Due to the long period of use, material creep caused difficulties in diagnosing the issues, so they ended up manufacturing a new one.