Safety Aspects in H2 Pipeline Design

In the process of decarbonization and transition from fossil fuels to green and renewable sources, a key role has been recognized for hydrogen, however concerns remain regarding its safety, due to hydrogen high reactivity. Hydrogen is characterized by a wide flammability range and a lower ignition energy, and it is also able to self-ignite upon release and to have unconfined explosions and detonation. Furthermore, hydrogen can induce degradation mechanisms in equipment materials that are not induced by natural gas, one of the main energy vectors currently used. As a result, equipment handling hydrogen can have higher failure frequencies compared to those handling natural gas. These factors must be taken into account when considering the establishment of a hydrogen distribution network throughout Europe, where safety distance between parallel pipelines and population shall be granted. This paper provides insight into the safety aspects of H2 pipelines focusing on two of the main constraints in the pipeline design: distance among parallel pipelines and distance from buildings and areas where human activities are present. To establish the above-mentioned safety distances, the quantitative risk analysis (QRA) technique is applied. Analyzing literature data and documentation available, the main uncertainties related to H2 QRA are investigated and solved. This process assesses pipeline failure frequencies, ignition probabilities and consequence modelling. Finally, a case study has been developed to compare the results obtained for a hydrogen pipeline with those obtained for a Natural Gas pipeline with the same route and geometric characteristics.