Engineering Assessment of Hydrogen Embrittlement Susceptibility at Defects in Hydrogen Pipelines by Numerical Modeling

Abstract Conversion of existing natural gas pipelines to transport hydrogen and hydrogen blending gas is increasingly recognized as an effective method to decarbonize the energy system and accelerate the achievement of the net-zero emission goal in 2050. However, aged pipelines typically exhibit various defects such as corrosion, cracking, and mechanical damage. These defects can lead to uneven stress and strain distribution, and plastic deformation, which can serve as hydrogen traps to accumulate hydrogen atoms, thereby increasing hydrogen embrittlement (HE) risk at defects during hydrogen services. Extensive research has been conducted globally, aiming to understand the degradation of the mechanical properties of pipeline steel and assess existing pipelines’ compatibility through theoretical and experimental methodologies and techniques, however, there are few studies on hydrogen atoms diffusion and accumulation behavior and the influence on the local degradation of material properties of steel at the defects. This deficiency in current research and industry standards underscores the urgent need for in-depth research and the development of reliable methodologies to assess the integrity of defects in hydrogen pipelines. This paper demonstrates an advanced multiphysics field finite element analysis (FEA) approach to study the time-dependent atomic hydrogen diffusion, accumulation, and hydrogen-induced fracture toughness degradation at pipeline defects and evaluate the locally enhanced hydrogen embrittlement risk at the defect sites. It is expected that this research contributes to the further development of defect engineering assessment methodologies for hydrogen pipelines.