MODELLING OF HYDROGEN-ASSISTED FATIGUE AND RISK ASSESSMENT IN STEEL PIPELINES FOR HYDROGEN-NATURAL GAS MIXTURES

Hydrogen plays a significant role in decarbonization systems and the future of global demands on clean energy. Utilizing existing natural gas pipelines to carry hydrogen is more economical than constructing new ones, but it leads to safety concerns regarding the integrity of repurposed pipelines for hydrogen or hydrogen-natural gas mixtures. Pipelines inevitably experience operational pressure fluctuations and other cyclic loads during their service life, resulting from factors such as variations in gas demand, start-up/shutdown sequences, and compressor station operations. Thus, fatigue damage accumulation is the leading mechanism with a potential risk on the long-term integrity and safety of these structures. This threat is heightened in hydrogen or hydrogen-blended natural gas services, where the presence of even small quantities of hydrogen has been shown to increase the growth rates of fatigue cracks in pipeline steels such that hydrogen-assisted fatigue is now considered the most important failure causes, limiting the lifetime and safety margins of this infrastructure.