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What criteria is normally followed to have inspection of in-service welds? Which services are required to be picked up, the frequency, and the risk based application?
Looking forward to have your inputs.

Requirements are mentioned in para 5.14 of ASME B31.3 (5th Ed. 2024) where first it differentiates between an existing weld defect from construction times and the flaw which might have appeared as a result of preferential weld corrosion or cracking. 2nd case is critical to inspect as that has resulted from in-service operation of piping using techniques capable of identifying flaws and their sizing. This should be defined by inspectors, inspection engineers, and RBI engineer that what techniques, and at what frequency are required to be applied. Also, acceptance of these flaws is required to be evaluated using FFS techniques.
Addressing the flaws in the welds from construction times is tricky and not at all times they are required to be inspected and addressed. However, if inspection findings indicate lack of quality control resulting in having welds with unacceptable flaws then there has to be a program in place to actually identify them on criticality basis (service based) and then to address them. While considering to apply inspection techniques and acceptability of welds, care must be taken to the recommendations provided in piping inspection code, "For in-service piping weldments, it may not be appropriate to use the original construction code RT acceptance criteria for weld quality in ASME B31.3. The ASME B31.3 acceptance criteria are intended to apply to new construction on a sampling of welds, not just the welds examined, to assess the probable quality of all welds (or welders) in the system. Some welds may exist that will not meet these criteria but will still perform satisfactorily in-service after being hydrostatically tested."
You may share the specific scenario to support the case related reply.

Looks like unexpected leaks have occurred from the weld joints. This reminds me of a case when in an amine piping, we started having issues with the welds and we knew that trigger is not the process functions. Though, that was the first thing to rule out before starting inspection of the welds to find some inherent flaws. And then that happened. Ended up scanning weld joints for two complete circuits (almost 50 joints), getting 13 or 14 with root flaws, and this then started a debate of what to accept and what not. Root flaws with indication in the filling were picked and those were re-welded. Quality issues during the construction projects sometimes lead us to have all this done before we keep on operating safely.

arcpro wrote: 06 Aug 2025, 09:57 What criteria is normally followed to have inspection of in-service welds? Which services are required to be picked up, the frequency, and the risk based application?
Looking forward to have your inputs.

That provides some good pointers.
Wondering if there have been any processes /services identified to have an inspection plan for in-service welding just like for anhydrous ammonia piping.

API 571 details almost all those services & materials where in-service welding is required to be defined.
Check out your case if it falls with the requirements stipulated and if not, then your failures may have been the result of construction flaws.
This is for sure that a lot many services in petroleum industries call for having a plan for in-service welds.
Take the case of anhydrous ammonia service piping where SCC is required to be eliminated with support of necessary inspection.
Hydrogen service, all in all calls for a plan in place. Moving on to dissimilar welding joints, and other such scenarios.

arcpro wrote: 15 Aug 2025, 17:10 That provides some good pointers.
Wondering if there have been any processes /services identified to have an inspection plan for in-service welding just like for anhydrous ammonia piping.