Non-Destructive Testing (NDT)

The methods we apply

No single NDT method suits every situation, so the responsible engineer selects the technique to match the material, the geometry and the type of defect being sought. Ferromagnetic welds are typically examined by magnetic particle inspection; internal flaws and wall thickness are interrogated by ultrasonics; surface-breaking cracks in any material by dye penetrant; and surface and near-surface flaws, including through coatings, by eddy current.

Combining methods gives confidence. A weld might be surface-checked by magnetic particle and volumetrically assessed by ultrasonics so that both the surface and the body of the joint are covered.

• Magnetic particle inspection for surface and near-surface cracks in ferromagnetic steel
• Ultrasonic testing for internal flaws and thickness measurement
• Dye penetrant testing for surface-breaking defects in any non-porous material
• Eddy current testing for surface flaws and coating-tolerant inspection

Where NDT is used

NDT is a core part of the five- and ten-year major inspection, where safety-critical welds and members are tested to the acceptance criteria set by the inspection plan. It is equally central to failure investigation, where the extent and origin of cracking must be mapped, and to structural assessment of machines with an uncertain history.

Because the value of NDT lies as much in interpretation as in detection, our technicians are qualified to recognised certification levels and report against stated acceptance criteria.

Reporting and interpretation

Every NDT result is reported with the method, the area examined, the acceptance criteria and the finding. Indications are located precisely on the structure so any subsequent repair or monitoring is unambiguous. Where a finding affects fitness for service, it is escalated into the wider engineering conclusion.