Fabrication, Workmanship, and Procedure and Performance Qualification
Qualification framework
Every weld must be made to a WPS that is either prequalified under the prequalification clause or qualified by testing. Prequalification is limited: joint detail, process, filler classification (F-number), position, thickness range, preheat/interpass, and technique must all fall inside the prequalified envelope. Any change outside it - for example switching from E7018 (F4) to an F6 flux-cored electrode - is an essential-variable change requiring a new PQR.
Procedure and performance testing
Procedure qualification uses a groove test assembly; the PQR is supported by reduced-section tensile specimens and guided bend specimens (two root, two face). Bend specimens must show no discontinuity exceeding 1/8 in in any direction. Welders are qualified separately: groove tests by bend or radiography, fillet tests by visual and fracture examination. Performance qualification carries position and thickness limits and lapses after six months without welding in that process.
Fabrication and workmanship
Cover fit-up and alignment tolerances, preheat and interpass control, cleaning between passes, backgouging to sound metal, tack welds made by qualified welders and either removed or fused, prohibition of arc strikes outside the joint, restricted peening (intermediate passes only), and the ambient-temperature rule: no welding below 0 °F unless the base metal is preheated to at least 70 °F and held there.
Traps
Assuming a prequalified WPS covers a thicker section or a different position; letting unqualified personnel make tack welds; measuring preheat on the wrong thickness.
Rule of thumb
If a variable appears in the essential-variable tables, treat any change as requiring requalification until proven otherwise. That conservative reading answers most exam items.