TY  - CONF
A1  - Grimault de Freitas, Tomás
T1  - Repair Welding on Future Pressurized Hydrogen Pipelines
N2  - Hydrogen is the energy carrier for a sustainable future without fossil fuels. This requires a reliable transport infrastructure. In this context, the conversion of existing natural gas (NG) grids is an essential part of the worldwide hydrogen strategies, in addition to the construction of new pipelines. Given the known effects of hydrogen embrittlement, the compatibility of the materials already in use (typically low alloy steels in a wide range of strengths and thicknesses) must be investigated. Initial comprehensive studies of the hydrogen compatibility of pipeline materials indicate that these materials can be used to a certain extent. However, pipelines require frequent maintenance and repair. In some cases, it is necessary to perform welding on pipelines while they are under pressure,
such as the well-known tapping of natural gas grids. This in-service welding presents additional challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, which can lead to sufficient hydro- gen absorption, and the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity of the respective materials compared to room temperature. In this context, knowledge about hot tapping on hydrogen pipelines is scarce due to the lack of operating experience. Fundamental experimental investigations are required to investigate the possibility of transferring the state-of-the-art concepts from natural gas to hydrogen pipeline grids to ensure that no critical material degradation occurs due to the potentially increased hydrogen uptake. For this reason, the presentation will present the state of the art in hydrogen pipeline hot tapping, including current research projects and their solution strategies in terms of pressurized mock-ups and basic testing scenarios.
T2  - ASTM Conference on Hydrogen Materials
CY  - La Rochelle, France
DA  - 03.06.2025
KW  - Component Test
KW  - Hydrogen
KW  - In-service welding
KW  - Pipeline
PY  - 2025
AN  - OPUS4-63332
LA  - eng
AD  - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER  -