Inspection, Acceptance Criteria, and Nondestructive Examination
Inspection stages and personnel
Inspection spans before, during, and after welding: verify joint preparation, fit-up, preheat, WPS compliance, root condition, cleaning between passes, and final weld appearance. All welds receive 100% visual inspection; the inspector must be qualified (typically an AWS CWI or equivalent), and NDE personnel must be qualified to a recognized standard such as ASNT SNT-TC-1A Level II.
Acceptance criteria
Visual acceptance prohibits cracks and overlap, limits undercut by depth, controls weld size and profile, and addresses crater condition and arc strikes. Undercut is depth-limited - 1/32 in for base metal thinner than 1 in - regardless of how long the undercut runs. Volumetric acceptance is set separately for statically and cyclically loaded structures, which is a frequent trap: a weld passing static criteria may be rejectable under cyclic criteria.
NDE selection
Ultrasonic testing is required for complete-joint-penetration groove welds in tension when the structure is cyclically loaded. Radiography suits full-penetration butt welds but is unreliable for lack of fusion in T-joint configurations because of beam orientation. Magnetic particle and penetrant testing find surface and near-surface discontinuities only.
Worked example
An inspector finds 1/16 in deep undercut along a 3/8 in thick plate. Because the base metal is under 1 in thick, the limit is 1/32 in, so the weld is rejectable and must be repaired and re-inspected by the same method.
Documentation
Record NDE method, extent, results, and repairs; rejected work stays rejected until repaired, re-examined, and accepted.