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NDT Qualification and Validation - inspection services | TWI

NDT qualification and inspection
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Inspection qualification is the formal process for gaining confidence that your inspection can meet its objectives and will detect the flaws you really need to find, convincing your management and regulators that the component or weld is fit for its purpose. The process covers the entire inspection process by examining individually and in combination the elements of the equipment, the procedure and the personnel.

Qualification increases the basic confidence gained from quality assurance, of using inspectors with general competence certification, and approved procedures conforming to codes and standards. It provides the additional evidence that the required inspection performance can actually be achieved in practice.

Elements of inspection qualification

The process of qualification of inspection consists of compiling theoretical and practical evidence to demonstrate that the inspection can meet its required objectives. This evidence is then presented to a body of experts in inspection qualification, the Qualification Body, to judge and to decide whether the inspection is qualified for its objectives.

One of the key aspects of the qualification process is that it relates the damage or degradation to the inspection outputs. A dossier of input information is assembled that will define:

  • the components and welds to be inspected
  • the types of defects/corrosion to be detected and/or sized and any limits to their location and orientation
  • the inspection performance to be achieved in terms of, for example, reliability targets, minimum flaw sizes to be detected, minimum wall thicknesses to be guaranteed, the accuracy of characterisation and dimensional sizing
  • the full NDT system to be used (procedure, equipment and personnel)

Qualification therefore takes place after the inspection procedure has been defined and approved in accordance with codes and standards; it is not part of the development process.

TWI Resources

TWI can provide advice and information on the whole qualification process, from the most appropriate codes and standards to apply, preparation of the technical justification, manufacture of the qualification trials specimens and provision of suitably qualified personnel for a Qualification Body.


The process of qualification will:

  • Challenge the operator to define the specific objectives of each inspection with regard to fitness-for-purpose of the component in question.
  • Lead to improved inspection procedures and clear reporting criteria by a process of peer review.
  • Verify the functionality and suitability of equipment through the process of practical trials such that fewer problems are experienced on the actual job, thus saving time and money.
  • Provide greater confidence in the inspection personnel, particularly when blind trials have been carried out.

Thus the entire system of inspection procedures, equipment and personnel is validated and a high quality inspection capable of detecting and assessing the defects of concern is assured.


For more information about TWI's NDT consultancy services, please email

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