Quality Assurance, Inspection, and Codes
Inspection order and scope
Inspection runs in a hierarchy: visual first, then surface NDE (PT or MT), then volumetric NDE (UT or RT). But inspection starts before the arc - verify WPS availability at the point of use, consumable certificates, joint preparation and fit-up, preheat, welder qualification records, and equipment calibration. Use the inspection and test plan to define hold points (work cannot proceed until released) and witness points (notification required). Nonconformances get a written report with a disposition: rework, repair, or accept by engineering concession.
Code versus opinion
Acceptance criteria come from the governing code, not from preference. A discontinuity the code permits is not a defect. Learn the difference between a discontinuity (any interruption in uniformity) and a defect (a discontinuity that fails acceptance).
Traps
- Rejecting a weld for undercut that is within the code limit.
- Running PT or MT on hot, dirty, or painted surfaces, or after the part has been machined - timing matters.
- Performing RT or UT before PWHT when the code requires examination afterward.
- Confusing a CWI (visual and qualification-based inspection) with an ASNT Level II or III examiner.
Worked example
AWS D1.1, statically loaded: undercut shall not exceed 1/32 in. Undercut between 1/32 in and 1/16 in is permitted only if the cumulative length does not exceed 2 in in any 12 in. So a continuous 3-in length of 1/16-in undercut is rejectable, while 1-1/2 in of the same depth spread within a 12-in stretch is acceptable.