I agree on your definition of underfill, and obviously undercut is from improper technique. The effect ringing of welds often has on a finished pipe fabrication is twofold, and I don't believe either neccessarily qualifies as underfill. Ringing most often results in a sharp angle of transition between the weld and parent metal, and digging a groove into the parent metal adjacent to the weld toe. This creates an undesireable notch, not underfill as you say. It doesn't truly create undercut either, by definition, only an undercut-like effect. I do remember Part B. :-)
Blend grinding or filing is allowable, according to the committee's answer to question two in my request for interpretation, as long as Table 341.3.2 requirements are met, as well as pressure thickness requirements in para. 304.
Not working in the piping industry, this "ringing" you are talking about.
They are basically removing by file or grinder some base metal to blend in the transition of the U/C or lack of fill that they had originally to the base metal? That's why they do this?
This is new to me. Even though it may not meet the definition, it sounds like before they "ringed" it, there was a condition that warranted repair/ re-work, and the solution was to "ring" it, but it removes base metal creating a notch, and thus an unacceptable repair method.
How about looking at this from the perspective of base metal thickness, could they have removed a certain percentage via "ringing" that would require it to be reinstalled?
I would agree with the definitions as posted earlier about U/C and lack of fill, that's right on the mark.
Chris
The danger of ringing depends upon just how deep the ringing is. If all you are doing is removing the oxidation to make the weld toe shiney it is harmless (I believe the depth of oxidation is still well within the AWS cyclic service restriction on undercut). I would however say that the very restrictive AWS cyclic service limitations for undercut should be considered though they don't really apply.
As a rule of thumb I would argue that if a depth of undercut is acceptable then a depth of ringing is acceptable.
Don't get me wrong, I do not advocate the practice, mostly on production grounds, but we can get too carried away with consideration of it in most instances and there is no code restriction that I know of to directly justify rejection.