Root Cause Analysis of an Above-Ground Pipeline With Stress Corrosion Cracking

A comprehensive metallurgical investigation of multiple, externally-initiated, in-service leaks on an above-ground, oil emulsion (multiphase) pipeline concluded that the crack-initiating mechanism was stress corrosion cracking (SCC). A technical root cause analysis (RCA) was performed, utilizing faults trees, to evaluate the potential contributors to the SCC from the time of construction through the identification of the first in-service leak. This paper outlines the RCA findings and current understating of the primary contributors given that SCC on above-ground, insulated carbon steel pipelines has not previously been reported.