Non-destructive testing of tube sheet butt welds
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This has been mentioned many times before; according to clause 4.6.4 of GB/T151-2014, for the circumferential weld joints of the shell side cylinder in fixed-plate heat exchangers where non-destructive testing is not possible, TIG welding should be used as a backing process, or gaskets that fit tightly against the base metal should be used along the entire length of the weld root. The weld joint coefficient φ is set at 0.6. When the design pressure on the shell side is greater than 4.0, according to Appendix I of GB/T151-2014, the joint between the plate and the cylinder should be designed using the defg method. In the case of using the def3 method, TIG welding as a backing process is applied, with a weld coefficient of 0.6. Can the welds at the plate-cylinder junction be exempted from non-destructive testing? Does this provision in the standard refer specifically to these welds? Now, many boiler inspection agencies do not accept such inspections; they believe that it is possible to perform non-destructive testing on this weld, reject the design, and refuse to inspect such equipment. However, the cost of forgings in format g as specified in Appendix I is too high. There is one piece of equipment currently in use in the workshop; it has already been processed, but the boiler inspection agency will not approve the inspection for some reason. I really feel like cursing.
I wonder if any of you sea friends have encountered this situation and how you solved it
The standards are clear: they refer specifically to the butt welds of the shell-side cylinders; your tube sheet butt welds and the welds between the tube sheet and the cylinder body are not included in this category. There is also another non-destructive testing method based on thermal shadowing, which you might want to consider.
Is thermal imaging forming without calculation detection now recognized by the boiler inspection agency?
Now I know that phase resonance can be detected, but it isn’t included in the standards, so it’s not recognized by the boiler inspection agencies
This weld is not acceptable for RT testing, but it can be approved through UT+PT testing; that’s what we’ll do
I’m curious that, for fixed-tube-sheet heat exchangers, if the joints between the tube sheet and the shell can be inspected, are there then any joints in the shell that cannot be inspected?
Ultrasound testing showed 100% compliance. It’s not possible to conduct 100% radiographic testing; instead, as much radiographic inspection as can be done should be carried out.
Due to structural reasons, the final circumferential weld cannot be inspected by RT
Designed at 0.6, with the addition of ut+mt or pt testing.
Under normal circumstances, shouldn’t the ring weld between the tube sheet and the shell be the last ring weld? I’ve never seen the middle seam used as the final seam before