The performance of in-line inspection tools employed for integrity assessments has significant impact on the reliability of assessment results, the extent of required remediation, and justification of inspection intervals. A previous paper by the authors established criteria for determining the number of “successful” measurements for establishing whether a tool’s performance should be accepted or rejected. The previous paper has also identified a “gray area” between these two limits, where it is not possible to either accept or reject the tool’s performance. In practice, the number of “successful” measurements usually falls in this “gray” area. This paper addresses how to assess tool performance in this “gray” area in terms of sizing tolerance, certainty, and confidence level. A sampling scheme related to the gray area is discussed. Examples are given for illustration.

Subject
Test methods, Confidence intervals, Materials performance, Pipeline integrity management, Inline inspection, Thickness measurement, Integrity assessment, Tools, Tolerances, Probability, Mechanical failure, Wall thickness, Samples
© 2008 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2008
Association for Materials Protection and Performance (AMPP)
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