Research, Experience and Ballot That Justifies Exclusion of Gas-Free, Low-Water Stabilized Crude Pipelines from NACE/ISO Sour Service Cracking Requirements

Abstract The harmonized NACE(1) MR0175/ISO(2) 15156 standard in 2003 overlooked a situation for gas-free, low-water crude (i.e. stabilized crude) pipelines, and by default brought these pipelines into the requirements of this standard. However, these pipelines were originally constructed per Canadian Standards Association and/or American Petroleum Institute standards without the hardness and welding requirements found in NACE MR0175 or the current NACE/ISO version of the standard and they have over 50-years of sulfide cracking-free service. This paper summarizes work undertaken by the Canadian Crude Quality Technical Association(3) (CCQTA) and previous work carried out by another project group to technically understand the risk of SSC in a stabilized crude pipeline. These efforts eventually led to the submission of a NACE MR0175/ISO15156 standard ballot to create a formal exclusion for stabilized crude pipelines from the sour service requirements of the NACE/ISO standard. The research investigation revealed that an approach that utilized partial pressure H2S to evaluate the serviceability of stabilized crude pipelines is fraught with technical challenges going beyond the scope of the NACE/ISO standard or its related standard H2S test methods. This paper focuses on (1) the problem details, (2) the early and later investigative work, (3) documentation of 50+ years of pipeline service experience involving over 40,000 km of North American pipelines, and (4) the development and successful passage of a ballot item for the NACE MR0175/ISO 15156 standard for a formal exclusion of gas-phase free, low-water stabilized crude pipelines.