Session: 03-02-01: Integrity and Performance of Welded Joints

Submission Number: 157508

Influence of Hydrogen on Overload-Affected Fatigue Crack Growth in Pipeline Steels 

Transporting high-pressure gaseous hydrogen through the existing pipeline network – both subsea and onshore – is a promising strategy for expanding the hydrogen infrastructure cost-effectively, supporting the transition to sustainable fuels. However, repurposing pipelines to carry high-purity hydrogen poses challenges for material integrity, as hydrogen can accelerate fatigue crack growth (FCG) in pipeline steels, especially under their typical operating conditions characterized by cyclic loads due to daily pressure fluctuations. Additionally, loading peaks, such as those from pressure testing, may further influence crack propagation. However, the effect of hydrogen on overload-affected fatigue behavior remains underexplored. This study examines the impact of hydrogen on FCG in a vintage Norwegian X65 pipeline steel (originally installed in 1982), focusing on how overload conditions modify crack growth in three scenarios: (a) overload in high-pressure hydrogen followed by FCG in hydrogen, (b) overload in air at atmospheric pressure followed by FCG in air, and (c) overload in air at atmospheric pressure followed by FCG in hydrogen. Preliminary results show that hydrogen significantly reduces the crack-retardation effect typically induced by an overload, leading to accelerated crack propagation and potentially compromising pipeline safety. In cases where overloading occurs in air and is followed by FCG in hydrogen – a scenario potentially similar to pressure testing before hydrogen injection in pipelines – a particularly severe hydrogen-induced crack acceleration was observed, underscoring the need for thorough safety considerations in pipeline repurposing.

Presenting Author: Leonardo Giannini NTNU

Presenting Author Biography: Leonardo Giannini holds a Master’s Degree in Energy Engineering, obtained at the University of Bologna (Italy) in 2022. His background includes energy systems, power plants and hydrogen technologies. Concerning the latter, he is enrolled in a Ph.D. program at the Norwegian University of Science and Technology (NTNU), focusing on the development of inspection programs for hydrogen systems (Risk-Based Inspection-RBI), with particular attention paid to metal-hydrogen interactions and the degradation of equipment working in hydrogen environments.