Inspection, Testing and Quality Control
Quality framework
Understand the role of the WPS, PQR and welder qualification records. A WPS is supported by a procedure qualification record; welders are qualified to a standard and a range of essential variables. Quality control is planned before welding: fit-up checks, consumable control, preheat and interpass monitoring, and documentation.
Inspection methods
Know visual inspection (the most common and first-line method) and its limits, then the volumetric and surface methods: radiographic testing (RT), ultrasonic testing (UT), magnetic particle testing (MT) for ferromagnetic surfaces, dye penetrant testing (PT) for non-porous surfaces, and pressure/leak testing. Understand what each detects: RT and UT find internal defects; MT and PT find surface and near-surface defects.
Defect recognition
Be able to name and describe porosity, slag inclusion, lack of fusion, lack of penetration, undercut, overlap, spatter, cracks (hot, cold, hydrogen), and lamellar tearing. Link defect to cause: e.g. porosity to gas or moisture; lack of fusion to low heat input or poor angle; cold cracking to hydrogen and restraint.
Traps
- Using PT on rough or porous surfaces.
- Using MT on austenitic stainless (non-ferromagnetic).
- Confusing lack of penetration with lack of fusion.
- Forgetting that visual inspection precedes and informs all other methods.
Rule of thumb
Match method to defect location: surface = visual, PT, MT; internal = RT or UT. Choose PT for non-magnetic materials and MT for ferromagnetic.