Safety and Integrity of Hydrogen Transport Pipelines

The subsea pipeline network on the Norwegian Continental Shelf (NCS) is increasingly being recognized as an opportunity for the large-scale transport of hydrogen from Norway to Europe. Utilizing existing natural gas pipelines for transportation of hydrogen gas brings several challenges, especially the risk of hydrogen embrittlement. Ensuring the safety of hydrogen transport relies on understanding its impact on pipeline materials. Recent findings from the RCN project HyLINE (2019-2023) highlight that while hydrogen adversely affects the mechanical properties of investigated pipeline steels, they may still meet existing design standards. However, the heat-affected zone of welds appears to be more vulnerable. To address this gap, HyLINE II will focus on the material integrity of welded joints in subsea hydrogen pipelines, examining their impact on overall pipeline integrity. Three PhDs and one researcher will be working in the project. The research partners SINTEF, NTNU, and Kyushu University (Japan) will collaborate with national and international industry partners that encompass the whole value chain of the hydrogen economy. These partners include Equinor, Gassco, Total E&P, TechnipFMC, Tenaris Dalmine and AS Norske Shell.

The subsea pipeline network on the Norwegian Continental Shelf is gaining traction as an opportunity for large scale transport of hydrogen from Norway to Europe, supporting a long-term and sustainable development of the energy system and contributing to the transition to a zero-emission society. The safety and integrity of the pipelines exposed to internal pressurized hydrogen gas must however be ensured. Pipeline steel welded joints are generally of higher strength than the adjacent base metal, featuring complex microstructures, potential flaws and residual stresses which in sum renders them more susceptible to being embrittled by hydrogen, so called hydrogen embrittlement. The existing Norwegian pipeline infrastructure consists of approximately 740,000 girth welded joints, all requiring special attention to ensure structural integrity in a hydrogen gas environment. HyLINE II will therefore address the follow key research questions: •How different microstructures, surface oxides and charging conditions affect uptake, diffusion and trapping of hydrogen globally and locally in the welded area? •How hydrogen influence the local mechanical properties of microstructures in the HAZ and what are the critical local damage and fracture mechanisms? •What is the susceptibility of hydrogen induced fracture in welded joints under static and cyclic loading in hydrogen conditions? •How to best represent and simulate hydrogen diffusion and trapping and the interplay between hydrogen, material and mechanical response on a local and global scale using numerical tools for fracture assessment? The project consortium includes the pipeline operator Gassco, the energy companies Equinor, Total E&P and Norske Shell and the technology provider Technip FMC. The research will be performed by SINTEF, NTNU and Kyushu University (JP) in collaboration with Imperial College (UK), Fukuoka University (JP) and Max Planck Institute for Iron Research (GER).