Germany has more than 500,000 kilometres of natural gas pipelines, which provide energy to industry and households. This infrastructure plays a central role in the transition to a hydrogen economy in which natural gas will be gradually replaced with up to 100% hydrogen, fed into the existing distribution pipelines. This network can also serve as a storage facility for the energy carrier. In addition, the construction of new hydrogen pipelines is planned and therefore must be tested.
To achieve these goals, important safety issues must be addressed; pipelines, seals and distribution stations, some of which are decades old, must be tested for suitability for transportation of pure hydrogen.
In principle, hydrogen can be transported in a similar way to natural gas; however, the atoms are particularly small and can be easily absorbed in metals. In the case of steels, for example, the uptake of hydrogen can lead to a degradation of the material properties. Under mechanical stresses, as they occur in every gas network, this can promote the formation of cracks and may lead to dangerous leaks.
To test pipeline steels for degradation, material samples have so far been subjected to exposure to hydrogen in an autoclave and mechanically stressed in the process. “Because of the large amount of hydrogen required, such tests require a high level of safety and are correspondingly expensive,” explains Florian Konert, scientist at the Hydrogen Competence Centre H2Safety@BAM. “This hinders a rapid expansion of testing capacities as they will be needed in the coming years.”
BAM scientists are now working on a testing technique that will make it much easier to show possible damage in the future – at lower cost. In the process, a steel sample is filled with hydrogen from the inside and simultaneously subjected to a mechanical tensile load. The method requires only a fraction of the amount of hydrogen compared to the existing method, which significantly reduces the safety-related issues. “We are convinced that our approach will expand the existing testing possibilities and thus enable a faster market ramp-up of hydrogen,” says Jonathan Nietzke, also a scientist at BAM’s Hydrogen Competence Centre.
With their innovative testing technique, the two researchers want to create a ranking of materials according to their suitability for hydrogen use, including pipeline materials in the natural gas distribution network. The results can provide companies that operate gas networks or manufacture components for the hydrogen economy with an important basis for assessing materials, which could help accelerate the retrofitting of existing plants or the construction of new ones.