One effective solution for decarbonisation involves advancing towards a hydrogen economy. This necessitates the establishment of transmission pipelines, which can either be newly constructed pipelines or converted natural gas pipelines. In the Netherlands and neighbouring countries, a significant portion of the hydrogen pipeline network is expected to comprise converted pipelines.

Natural gas transmission system operators are actively exploring the viability of repurposing existing natural gas pipelines for hydrogen use. Gasunie, the Dutch operator overseeing both natural gas and hydrogen, is presently in the process of developing an onshore and offshore hydrogen network, with plans for gradual expansion in the coming years. Approximately 70% of the onshore network is expected to be comprised of converted natural gas pipelines, while the offshore network, responsible for delivering substantial hydrogen quantities ashore, is likely to feature a higher proportion of newly constructed, large-diameter pipelines. Gasunie is currently evaluating various options for the offshore hydrogen network, including the repurposing of existing pipelines. This paper outlines Gasunie’s method, ensuring that converted and new pipelines meet integrity requirements and can be operated safely.

This method is based on preventing the degradation mechanism of hydrogen-enhanced fatigue crack growth. It entails effectively managing pressure variations and other fatigue loads to hinder the growth of pre-existing planar defects in the pipelines. The primary locations susceptible to these defects are the longitudinal and girth welds of the pipelines. The specific defects to evaluate depend on the type of fatigue load involved. Once the service life, fatigue load type, and the types and sizes of defects are established through comprehensive study, the permissible fatigue load can be calculated. The basis for this calculation is a restricted degree of defect growth.