American Welding Society Forum
Say you find a rejectable defect "AWS D.1-static loading" in the root area of a B-U4a weld using U.T. Can you repair only the defect area from the backing bar area where the defect is located, leaving the rest of the bar intact or as a inspector is saying, either you have to remove the entire backing bar, repair effected area, then reweld area where the backing bar was located. He also said we could go through the weld area from the front side to make repair. Plate is ASTM 572 GR. 50-1.5" thick.
I would not recommend removing a portion of the backing bar for easier access, and leave the rest of the bar intact. If you opt to proceed with this, obviously the backing would no longer be continuous, thus increasing the possibility of subjecting the freshly cut edges of the remaining backing bar to notch potential, which could eventually spread into the base metal. I would follow the easier of the two inspector's options.
I do agree that the possibilty of the notch acting in a adverse manner is quite distinct, but what I really like to know if there is a code section that states that it can't be done, as the inspector is saying.
I couldn't find anything that said it can't be done, but 5.10.2 does state full length backing. Whether or not this would apply to your "after the fact" situation, could be open for discussion, I guess, but wouldn't it be wiser to eliminate the notch potential by following the inspector's suggestions?
Absent anything to the contrary in the Contract or General Spec. which always takes precedence, I would suggest you follow the Inspector's direction.
Yes, it would be an appropriate repair to gouge through the backing bar into the root area to remove the defect, then weld the cavity flush to repair the weld and restore the backing bar. The other option is to do as suggested by the inspector and remove the entire backing bar, then repair the root as needed. If repairs are not addressed in the contract specs, then determining the repair method is the engineer's responsibilty, not the inspector's. The inspector must perform the required examinations to determine compliance with the contract specs and applicable codes or standards.
However, I'm wondering why a single bevel groove weld was used if you have access to the backing bar. Wouldn't it have been much less welding to use a double bevel groove? You also wouldn't have to worry about the backing bar producing root geometry indications on the UT exams.
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