Learning from Multiple Corrosion Growth Rate (Run Comparison) Studies

Corrosion growth can be estimated using many types of run comparisons.  Within the last decade or two run comparison techniques have evolved from box matching of defect samples to signal matching of the total defect populations.  Theoretically some of the methods have been found to be superior. However in practice it is hard to validate the benefits of one method over the others without multiple sets of run comparisons on the same pipeline. Multiple run comparison analyses have been performed on the TransCanada system to establish corrosion growth rates. Comparison of the results from these various analyses gives in-site into the accuracy and uncertainty of each type of estimate.

 In an effective integrity management process the best available corrosion growth data should be used.  To do so it is important to understand the conservatism and the uncertainty involved in each type of estimate.  Learning from multiple corrosion growth studies are explained and discussed in this paper. The relative merits of the different techniques and consequent appropriate use in integrity management programs is also discussed.