Technical Challenges and Strategies for the Repurposing of Existing Gas Distribution Pipeline Networks for Hydrogen Transport

Abstract Enbridge aims to assess the transport of hydrogen blends through an existing gas distribution network. Demonstrating suitability of existing pipelines for hydrogen repurposing is a complex task, with limited industry consensus or historic empirical data on hydrogen pipelines adding uncertainty to the process. The 2023 edition of CSA Z662 [1] has provided some clarity through the Engineering Assessment approach introduced for hydrogen repurposing; however, it leaves aspects of the assessment to be further defined. Whilst more prescriptive requirements may be referred to in other standards, such as ASME B31.12 [2], these requirements are liable to change with regular updates and industry research on hydrogen. The subject pipeline network poses particular challenges for Engineering Assessment due to assets being unpiggable, limited availability of integrity data, and the wide range of pipe populations, with construction spanning multiple decades. In the absence of specific data, inspection and testing are essential to reduce the conservatisms and refine risk assessments. Recognizing the challenges in collecting data for an unpiggable and urban distribution system, it is critical to optimize the strategy for testing and inspection. This paper details a project completed between Enbridge and ROSEN to explore the effects of hydrogen on the integrity of the pipeline system in the face of limited data, with an approach centred around an extensive sensitivity study assessing fracture and fatigue. The approach also used an asset ranking model drawing on the findings of the sensitivity study to support effective targeting of inspection and testing to maximize the value from gathered data. In addition to the project findings, this paper provides insights on the implications for hydrogen repurposing of distribution pipelines and systems with limited specific data to support detailed Engineering Assessments.