Bayesian reassessment of the number of flaws in a pipeline

A practical method for correcting an estimate of the true number of defects in a pipeline after performing in-tube flaw detection and subsequent verification of measurement results by a second independent verifying instrument is presented. A direct correction method was initially proposed by one of the authors [1]. A more precise method, which is based on the Bayesian procedure, is considered in this study. The problem of predicting the most probable number of true flaws in each interval of changes in the flaw parameters (hereinafter, the flaw depth is considered) is solved on the basis of data from the inspection of detected and actual flaws in a pipeline. These results can be used for the evaluation of the quality of a performed in-tube inspection and the quality of in-tube and verifying instruments, when solving appropriate problems of pipeline reliability (as the input data), and when planning inspections on the basis of risk assessment.