Assessment of Previously Examined Dent Recoated With Two-Part Epoxy and Later Found With Near Neutral Stress Corrosion Cracking - What Was Missed

Abstract The pipeline industry continues to strive for improvements in managing mechanical damage and to learn from case studies. A technical case study will be presented for a rock dent from the original construction of the pipeline that was excavated, constraining rock removed, examined, and recoated with two-part epoxy external coating. The recoated dent was subsequently excavated as part of a later dig program and the field non-destructive testing (NDE) discovered the dent had developed external cracking through near-neutral pH stress corrosion cracking (NNpH SCC) while in service. This paper aims to share the learnings from metallurgical analysis, finite element analysis, and a high-level root cause analysis and will cover the findings and contributing factors that allowed for NNpH SCC to occur on a dent externally coated with two-part epoxy and how a liquid operator is using the findings in its integrity management program when assessing dents.