As of today, hydrogen can play a significant role in decarbonizing the world's energy supply to mitigate climate change and a suitable pipeline infrastructure will play a key role as well. However, for steel pipelines, it is well recognized that hydrogen may promote hydrogen embrittlement phenomena affecting pipeline integrity properties such as ductility, fracture toughness and fatigue performance. This paper summarizes the type of tests and the results of a testing campaign started in 2021 with the scope to verify and qualify a typical steel material with seam welds and fabricated girth welds for high pressure hydrogen transport offshore.
The combination of embrittlement with severe loads as for an offshore pipeline calls for a comprehensive awareness of material performance under such conditions. To achieve that, the first step has been the classification of failure modes by type of installation condition and selection of the tests required to characterize materials against them. Consequently, Saipem as pipeline construction contractor funded a test campaign to start filling the gaps initiating a comprehensive testing campaign to assess the behavior of base material, seam weld and girth welds under different hydrogen environments, to establish the limiting criteria for their resistance to H2 embrittlement, to contribute to the reduction of any over-conservatism in ASME B31.12 and bring solutions for the development of an achievable and affordable hydrogen pipeline network.
This paper summarizes the type of tests defined and the results of the testing campaign started in 2021 and to be completed in 2024. The testing campaign conducted in cooperation with RINA-CSM laboratories in Rome and Cosenza (Italy), systematically tested the base material, the seam weld and the girth welds fabricated according to Saipem welding procedure specifications for a X65 steel grade pipe. The final design of the test campaign included the minimum number of key tests necessary to assess the effect of atomic hydrogen inside the steel matrix and the related changes in mechanical properties, including the evaluation of tensile behavior and ductility, impact properties, fracture toughness (determination of KIH through static load and rising load tests). The tests were performed in different concentrations of hydrogen (i.e., different blending scenarios) at a given pressure which was considered potentially representative of the future main operating conditions in offshore hydrogen transportation systems.
