Fabrication, Applications Engineering and Quality Management
This domain tests the documentation chain that proves a weld was made correctly: specification, qualified procedure, qualified welder, calibrated equipment, records.
The documentation chain
A welding procedure specification (WPS) is supported by a procedure qualification record (PQR) produced by testing a pWPS to a standard such as ISO 15614-1. The PQR defines essential variables: process, parent material group, thickness range, consumable, position, preheat and post-weld heat treatment. Welders are qualified separately, for example to ISO 9606-1, by test piece and essential variables. Quality management follows ISO 3834 parts 2–5, scaled to the product.
Traceability and calibration
Consumables should be traceable by batch, with inspection certificates (EN 10204 type 3.1 for many structural jobs). Welding machines, ammeters, voltmeters, flowmeters and NDT equipment require calibration. Records include WPS/PQR, welder certificates, heat input, preheat records and NDT reports.
Worked example
A butt-weld procedure is qualified on 10 mm plate. Under ISO 15614-1 the qualified thickness range is normally 0.5t to 2t, i.e. 5–20 mm, provided other essential variables remain unchanged. Reasoning: the lower bound protects against lack of fusion and excessive dilution in thin sections; the upper bound limits heat input and cooling behaviour. A 25 mm production joint would need a new qualification or a qualified multi-run procedure covering that thickness.
Traps
Treating a welder certificate as a procedure qualification. Assuming a PQR covers unlimited thickness or any position. Ignoring consumable group changes (e.g. rutile to basic). Forgetting that preheat and PWHT are essential variables.