NACE MR0175/ISO15156 Exclusion Re-Established for Stabilized Crude Pipelines

Gas-free, low-water stabilized crude pipelines in Canada have been constructed over the past 50 years without the hardness and welding requirements found in NACE MR0175 or the current NACE/ISO version of the standard. Previously exempted from this sour service standard, the harmonized NACE MR0175/ ISO 15156 standard ratified in 2003 overlooked this situation. This article summarizes the findings of a project to understand the actual risk of sulfide stress cracking (SSC) in stabilized crude pipelines. In this study, standard industry sour service qualification tests (i.e. NACE TM0177) proved inadequate. As a result, an extensive field experience survey was used to develop a successfully affirmed ballot for NACE MR0175/ISO 15156 that finally reestablished a sour service exclusion for these stabilized crude pipelines.