Determining the Number of Excavations Required to Confirm the Presence or Absence of SCC on a Pipeline Following an SCCDA Process

The pipeline industry has been managing the threat of Stress Corrosion Cracking (SCC) for several years using the methods developed by NACE SCCDA [1] (Stress Corrosion Cracking Direct Assessment) and ASME B31.8S [2] standards. SCCDA is a widely accepted tool for assessing the threat of Stress Corrosion Cracking in pipelines. The process utilizes data from direct examinations at excavations to validate the process as well as to address existing SCC anomalies, if found. However, neither the recommended practices nor the literature provide a usable and practical method for determining the number of excavations necessary for the excavation program based on observed results. To address this question, the Pipeline Research Council International (PRCI) sponsored a project to develop a statistically defendable procedure to determine the number of excavations which would be required to validate the SCCDA process and confirm either the presence or absence of SCC.