Quality requirements for weld joints near openings
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GB150.3 6.1.4 stipulates that when an opening passes through or is adjacent to a vessel weld joint, it is necessary to ensure that there are no defects exceeding the specified limits within a radius of 2dop around the center of the opening; however, no requirements regarding non-destructive testing are specified (GB150 version 98 did require such testing). GB150.410.3.2 specifies non-destructive testing requirements only for joints of nozzles that meet the criteria for not requiring additional reinforcement, within a certain range of openings. According to the standard interpretation of GB150, for weld joints within the specified area around openings that require reinforcement, designers shall decide based on specific circumstances whether additional inspection requirements are necessary. How do you handle such situations?
Welds within the 2dop range are subject to X-ray inspection as specified in the drawings.
Non-destructive testing should be carried out; it is impossible to determine with the naked eye whether there are any defects exceeding the specified limits inside the joint
Welds within the 2dop range are to be X-ray inspected in accordance with the X-ray grading requirements specified in the drawings.
What ensures the quality of welds? It’s not flaw detection yet.
The question is why the new GB150 removes the requirement for partial radiographic or ultrasonic testing of welded joints that, according to the 1998 version, were required to fall within this range; instead, the interpretation states that it is up to the designers to decide based on specific circumstances.
The welds within a range centered on the opening center with a radius of 1 time the opening diameter are subject to radiographic inspection, and the acceptance standard is the same as that for the main structure.
There should be no defects that exceed the specified standards; but of course, testing is still necessary. What is used for testing these days? It’s NB/T47013. Use whichever method you think is better, but if the equipment itself has already undergone complete non-destructive testing, then testing isn’t necessary. If it’s localized, then full non-destructive testing must be carried out within this area!
I also believe that there is no other reliable method besides conducting tests, but the question is: why does GB/T150 take such a complicated approach to this issue? Why not specify it clearly directly?
We follow the principle of taking the higher value rather than the lower one when carrying out the operation