The desire to move to a more decarbonized fuel supply coupled with reduced public acceptance for new pipeline projects is driving the oil and gas industry to consider the conversion of existing transmission pipelines, both liquid and natural gas, to gaseous hydrogen service. Introduction of hydrogen into carbon steel pipelines, either as a blend or 100% hydrogen, potentially exacerbates the threat of hydrogen embrittlement with implications to pipeline integrity management. Other interaction concerns such as corrosion/ cathodic protection, cracking, external loading ROW/HCA impacts, and fatigue threats are also impacted as a result introducing hydrogen.
Industry has embraced the need to transport hydrogen, but project teams are operating out in front of consensus standards and regulatory guidance. As such, operators are encountering challenges with simply evaluating the viability of a hydrogen transport project and completing appropriate risk assessment for integrity management purposes. There is no consensus amongst North American and European standards as to what % hydrogen constitutes blended gas; therefore, it is not clear when specific design considerations need to be considered. Additionally, widely accepted pipeline integrity standards and recommended practices are largely silent on the unique impacts of hydrogen.
This paper will review the relevant industry standards for applicability, identify complementary and conflicting guidance, while offering a process roadmap for evaluation of key threats for legacy liquids and natural gas pipeline systems slated for conversion to hydrogen service. Additionally, the paper will provide a risk assessment roadmap for a structured assessment model that summarizes hazards and risks, identifies potential controls, establishes appropriate leading indicators, and describes the mitigation programs that must be in place to ensure safe operation of a hydrogen pipeline