Integrity and Safety of Repurposed Hydrogen Pipelines in the European Union

The development of a comprehensive hydrogen infrastructure in the European Union is required to bridge the gap between hydrogen supply and demand. The repurposing of part of the existing natural gas infrastructure for the transport of hydrogen, in addition to new constructions, can accelerate the establishment of a hydrogen transmission network in the European Union. Hydrogen exposure is, however, known to notably reduce the ductility and fracture toughness of steel materials and increase fatigue crack growth rates. These changes in material properties may have implications on the behaviour of defects found in the existing natural gas infrastructure and may lead to the need for an update of the pipeline inspection and integrity management practices. From a safety perspective, the safety protocols, emergency response plans, and risk assessment methodologies need to be revised to account for the distinctive properties of hydrogen in comparison to natural gas. Knowledge of past gas pipeline incidents allows a better understanding of the future behaviour of the hydrogen gas grid. The incident history from the natural gas transmission sector in Europe and from hydrogen pipelines worldwide has been compiled using the data available from the European Gas Pipeline Incident Data Group (EGIG) and from the Hydrogen Incidents and Accidents Database (HIAD). Their analysis provides valuable insight on the main threats to pipeline integrity and safety.