In the presentations of the previous two years, the authors had been focusing i) on issues related to the admixture of hydrogen into the European gas grid and ii) on general design aspects of hydrogen pipelines. In the case of gas pipelines, the engineering companies can reach well-establish and proven standards that set the regulatory and safety basis for its design. This is not yet the case for new hydrogen pipelines in Europe, where there is a lack of standardized frameworks. So what to do when there is no specific baseline to design and construct H₂-Pipelines? American standard ASME B31.12 seems to be one step ahead , defines clear rules, and is broadly used in Europe as well. Other industry-recommended practices, but not formal standards, such as EIGA 121/14 are also referred to as basis. Nonetheless, any design of a new H₂-Pipeline based on ASME B31.12 will still need the endorsement of each country’s regulatory bodies.

This paper includes several aspects of the design of specific hydrogen pipelines in Europe, which had been developed by ILF in the last years. For example, process and safety considerations, material aspects, aspects related to compressor selection, and specifications for main equipment were considered and presented. If there is no clear guidance by standards, an engineering approach was provided, e.g., by using similar approaches as conducted for natural gas and adapting them to the specific parameters and properties of hydrogen.

Furthermore, the welding process for hydrogen pipeline is highlighted as very important due to the material characteristics related to hydrogen embrittlement. Some relevant aspects of a welding specification for the construction of new hydrogen pipeline will be presented in the paper. Finally, conclusions are drawn on what this means for the repurposing of existing pipelines to the medium hydrogen.