Sealing performance of pipes and joints in pure hydrogen

Abstract The transition toward hydrogen as a clean energy carrier requires reliable infrastructure, particularly for its distribution through pipelines. This study evaluates the sealing performance of various pipe and joints under pure hydrogen, the most challenging condition for leakage. An experimental setup was developed to test four representative pipe samples taken from the Italian gas distribution network, differing in their dimensions and in the constituent material, including galvanized steel, polyethylene PE100, and API 5 LGR B steel. Each sample was pressurized with hydrogen and the pressure was monitored over one week under controlled temperature conditions. Results showed no measurable leakage in steel pipes, confirming their readiness for hydrogen integration. On the other side, the PE100 pipe exhibited a measurable pressure drop attributed to gas permeation, which however resulted to be lower than the predicted value based on average polyethylene permeability, suggesting material-dependent behaviour. Notably, literature suggests that hydrogen permeability in polyethylene may decrease over time as the material crystallinity increases. Since gases cannot diffuse through the crystalline phase, this implies that hydrogen losses due to permeation could diminish rather than intensify, a reassuring insight for long-term pipeline applications. These findings suggest that much of the current steel-based infrastructure may already be compatible with hydrogen, while polymeric components require further study due to their variable permeation behaviour.