NDTnet 1998 Aug, Vol.3 No.8

Abstract

Non-destructive examination (NDE) reliability information is gradually being taken into more extensive use. This ranges from mere recognition of the limitations, which are inherent in many NDE techniques, to use in structural integrity assessment. Further applications are for appreciation of the outcome of NDE audits, comparison and replacement of NDE techniques, NDE technique sensitivity setting for cost-effectiveness, definition of NDE acceptance criteria, and optimisation of in-service inspection intervals and risk based inspection (RBI).

NDE is commonly used first to reveal defects in a construction, and then determine the size, position and other characteristics of the defects. NDE reliability description of is thus firstly related to probability of detection (POD) and secondly to defect characterisation abilities. In addition, the probability of false calls is important, especially for cost considerations.

To determine NDE reliability data, experimental trials are required, or modelling with experimental verification. For the application case in question a number of specimens including a realistic selection of defects have to be investigated under realistic working condition. For statistical confidence the number of defects must be sufficiently high.

During the last twenty years there has been a number of investigations for determination of the performance of various NDE techniques for different applications within aerospace, nuclear, offshore and other industrial branches. These different studies have, in principle, given results, which should be useful for assessments where NDE reliability is involved. Practices for performing trials have, however, been different, and analysis and presentation of results have varied, so they are not always suitable for an intended practical use.

In order to overcome these difficulties, to have trials performed in realistic and more uniform ways, and have results described in a realistic and consistent manner suited for their use, some sort of guidelines is required. This led in 1994 to initiation of Nordtest projects to work out Guidelines for Validation of NDE Techniques and Guidelines for Description of NDE Performance Data, which are scheduled for publication late 1997. These guidelines reflect the above considerations, and also contain requirements on 'normal' confidence in results.

In addition, to meet more specific needs, Guidelines for Replacing NDE Techniques with One Another was published 1995, whereas Guidelines for Development of NDE Acceptance Criteria is being planned. Both documents involve the use of NDE reliability considerations.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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