NDT coordination: the right method, extent and evaluation

We do not perform NDT ourselves and sell no testing hours. Precisely because of that, we can advise objectively on what should be examined, by whom, and what the findings actually mean for your product and your client.

Why independent NDT coordination

NDT companies are good at performing examinations, but the surrounding decisions rest with you as the manufacturer: which method, what percentage, at what point in production and against which acceptance criteria. Leave those decisions to the testing house and you soon pay for examinations that add nothing, or miss testing the standard actually requires.

As an independent party, DEHAAS translates the requirements of standards and contracts into a practical inspection and test plan. We make sure the testing does what it should: demonstrating that your welds comply, at reasonable cost and without surprises at final acceptance.

Choosing the right method

Each NDT method has its own field of application. Visual testing (VT) to ISO 17637 is always the basis. Penetrant testing (PT) and magnetic particle testing (MT) reveal surface defects, MT only on ferromagnetic material. Ultrasonic testing (UT) and radiographic testing (RT) examine the weld volume and find internal defects such as lack of fusion and inclusions.

The choice depends on material, thickness, joint type, access and the defects you expect. Our knowledge centre article on choosing an NDT method sets out the considerations. We record the choice per weld, so there is no room for debate later.

Determining extent and timing

How much testing is required follows from the standard and the risk. EN 1090-2 links the extent of supplementary NDT to the execution class and joint type, while for pressure equipment the PED category and the harmonised standards define the regime. Clients frequently add requirements of their own on top.

Timing matters too. Higher strength steels require a holding time between welding and testing because of hydrogen cracking, and examinations must take place before welds become inaccessible through coating or assembly. We capture extent, timing and hold points in an inspection and test plan that fits your production schedule.

Managing NDT contractors

We subcontract the actual testing on your behalf to qualified NDT companies, with personnel certified to ISO 9712 in the relevant method and sector. We obtain quotations, compare them on substance and agree clearly on procedures, acceptance criteria, report format and schedule.

During execution we act as the single point of contact. We ensure the examiner receives the right information, that testing happens at the agreed moment and that reportable findings reach the right people immediately. Your production loses no time waiting, and no examination has to be repeated.

Evaluating results in context

An NDT report full of indications means little by itself. An indication only becomes a defect when it falls outside the acceptance criteria, for instance ISO 5817 level B, C or D, and a defect only becomes a problem when it affects the function of the joint. That judgement requires welding knowledge, not a checklist.

DEHAAS evaluates results against the standard, the drawing and the loading, as part of our wider welding inspection and QA/QC services. We advise whether an indication can be accepted, must be repaired or needs further examination, and substantiate that position in writing towards your client.

From finding to solution

Our work does not stop at a rejection. We trace the cause of the defect, from incorrect parameters to damp consumables, and draw up a repair procedure that solves the problem without introducing new damage. After repair we define the required re-examination and whether testing should be extended to other welds.

Recurring findings are translated into structural improvements in your welding process. Our article on recognising weld defects covers the common types and causes. Rejection rates fall, and with them your testing costs.