Nondestructive Examination Coordination (NDEC)
Plan before you shoot
NDT is planned, not improvised. For each joint the NDT plan/matrix should fix: method (VT, PT, MT, UT, RT and advanced variants), stage (root, final, before/after PWHT, after pressure test), extent (full or percentage/random), technique and standard (e.g. ISO 17636 for radiography), acceptance criteria (e.g. ISO 5817 quality level B, C or D, or ISO 10042 for aluminium), and the responsible personnel and records.
Personnel and procedures
Under ISO 9712, Level 2 performs and interprets testing to a written instruction; Level 3 writes procedures and techniques and carries overall technical responsibility. Certification alone is not enough - the employer must authorise the individual for the specific method and scope.
Method limits that questions exploit
PT is unsuitable on hot, rough or porous surfaces and needs low-halogen consumables on austenitic stainless steel. MT applies only to ferromagnetic material. UT of austenitic welds requires special probes, low frequency and dedicated technique. Radiographic sensitivity is judged by image quality indicators, not by film density alone. Delayed inspection (commonly around 48 h after completion, per specification) is used where hydrogen-assisted cracking is a risk.
Worked example: a specification demands 10% RT on 25 mm carbon steel butt welds but says nothing else. Before any exposure, coordination confirms: technique to ISO 17636 class B, acceptance to ISO 5817 level C, timing after PWHT, Level 2 personnel with employer authorisation, and a report cross-referenced to the weld number.
Traps: letting NDT staff choose acceptance criteria; treating percentage sampling as a guarantee of quality; accepting oral results - no record means no inspection.