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Total Quality Inspection - NDT In-Service Inspection | TWI

Total quality inspection
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Total quality inspection (TQI) is a term used to describe a holistic approach to improving in-service inspection (ISI) of engineering critical structures and process plant. TQI is part of an initiative from TWI, driven by its Industrial Members, to improve the performance of non-destructive testing (NDT), particularly in the oil, gas and petrochemical sector, where it is seen to lag behind the performance achieved in aerospace and nuclear industries.

Moreover, the continuing refinement of risk-based inspection (RBI) methodologies to plan inspections and engineering critical assessments (ECAs) to sentence flaws and discontinuities for Fitness-for-service (FFS) is placing greater emphasis on the performance of NDT, with NDT becoming a vital link between RBI and ECA.

Among the problems in ISI that have been identified are:

  • Absence of training courses and certification schemes for personnel specific to the needs of ISI.
  • Lack of specific ISI codes and standards.
  • Improper qualification of NDT procedures.
  • Use of NDT procedures that have not been validated.
  • Wide and increasing range of NDT methods and equipment for which operator certification and procedure qualification is non-existent. 
  • The human factors influencing NDT operator performance under arduous and sometimes hazardous site conditions.

The holistic approach of TQI covers the three factors that influence NDT performance:


  • Operator training and certification.
  • Equipment/technique selection.
  • Procedure qualification.
TQI also encompasses the ‘Total Quality’ concepts of continuous improvement, customer focus and team working and provides a sustainable inspection activity that can evolve to meet future needs. This is accomplished through an implementation cycle.

The cycle begins by appraising current working practices, then conferring with the client to ensure agreement and complete ‘buy-in’ to the goals of the TQI implementation plan, before employing a range of methodologies including NDT procedure qualification, training and mentoring and finally revising progress at an agreed milestone. At this milestone a decision is made as to whether or not a new cycle is needed.

The cycle would be very detailed in the case of organisational change, but may be used in a very simple form to change a particular inspection activity.

TWI works with the client to implement and monitor the ‘implementation cycle’ and will normally document the activity in a TQI ‘Written Practice’. The principal aim is to achieve sustainable improvements to the in-service inspection organisation and operation, agreed by all stakeholders in the inspection activity.

TWI Resources

  • Training resources in all aspects of NDT, RBI and FFS, worldwide.
  • Internationally recognised CSWIP certification scheme for NDT personnel.
  • Knowledge of new NDT methods and techniques from on-going Research and Development.
  • Understanding of factors affecting NDT performance built up from 40 years of NDT consultancy, ECA of flaws and failure investigations.
  • Applications laboratory to help in developing techniques.
  • Wide range of NDT equipment, advanced as well as conventional, covering all aspects of NDT.
  • Team of Level 3 consultants to authorise NDT procedures, conduct qualification and validation exercises, overseeing TQI written practice.
  • Team of Level 2 NDT technicians to act as mentors for on-site operations.


  • Improvement in inspection performance through increased defect detection rates, reduced false calls, greater coverage, etc.
  • Improvement in inspection efficiency through faster inspection rates, reduced reporting times, fewer stand-down periods.
  • More focussed inspection and through improved RBI procedures.
  • Fewer unnecessary repairs through improved FFS assessments.
  • Acceptance of inspection as a benefit and not a cost.
  • Greater use of non-intrusive NDT techniques and therefore shorter plant shutdowns.
  • Move towards continuous structural health monitoring and away from periodic inspection.
  • Better motivation of inspection personnel.


  • Rationalisation of inspection operations to raise confidence in RBI planning processes.
  • Greater use of FFS methodologies in defect sentencing decisions.
  • Integration of inspection with integrity management strategies for ‘ageing’ assets. 
  • For proper cost/benefit analysis of in-service inspection

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

For more information please email: