D1.1; 5.24.4 (2004 edition) for butt weld reinforcement. width of cap would be a jubject of included angle and root opening, you may look at Fig. 5.3, 5.22.4.1 and also the prequalified joints. Hope this helps.

The maximum reinforcement is 1/8 for all groove welds under AWS D1.1. The width of the finished weld is not addressed and is influenced by the groove angle and root opening.

You sound concerned that the welder may get carried away with the cover layer or attempt to correct undercut by "capping" the weld with yet another weld layer that is wider than the layer containing the undercut. That situation can be addressed if you formalize the your visual acceptance criteria. Put what is acceptable in writing and have the welder read it. Remember, the criteria in AWS D1.1 or any other welding standard are the minimum requirements. The manufacturer can tighten the criteria.

The third party inspector is bound by the minimums listed by the applicable welding standard unless and alternate (more tightly controlled) criteria is documented as part of a quality control manual or other contract document.

Welder qualification programs should be formalized with published visual acceptance criteria. The VT criteria should be made known to the welder before the test starts. My program includes a listing of the tools that are permitted, personal protection that must be used, what the welder can and can't do during the test, i.e., the test coupon can't be removed from the test position for cleaning, etc., a WPS that must be followed, and the visual acceptance criteria. The welder reviews the documents with the test witness and signs the documents before the test is started. All the "rules and regulations" stay with the welder during the test. As stated in a previous thread, I also include a photograph of the welder on the test report, assuming the welder passes the test. I don't issue a report if the welder fails. I've had an instance where the welder worked for over a year with papers stamped "failed" before anyone read the test report.

Good luck - Al