Hydrogen [H2] is a topic that is receiving a lot of attention. Hydrogen is also very important for sealing technology. As IDT, we were part of the Hzwo:Frame funding project and are a member of HZwo e.V., the Competence Center for Hydrogen in Saxony. Our goal is to accompany the development of this future technology from the very beginning, to open up new sales markets for our products and to support our customers on their way to the energy transition. To this end, we have already built up a considerable network and sound expertise. However, to understand the potential that hydrogen technology holds, it is helpful to distinguish between three areas: hydrogen production, hydrogen transport and storage, hydrogen usage.
Hydrogen is produced by the electrolysis of water, which is broken down into oxygen and hydrogen. One speaks of green hydrogen when electricity from renewable energies is used in its production. This type of production is CO2-free, which is why many experts see green hydrogen as an energy source of the future: for industry, for heat supply and for mobility.
Hydrogen transport and storage
For the transport and storage of hydrogen, natural gas network and storage or liquid organic hydrogen carriers [LOHC] are of interest. For automotive applications, pressurized storage systems between 300 and 700 bar are being tested, and cryogenic systems down to -253°C are being developed for aerospace applications. This area is relevant for sealing technology, since seals are used wherever the escape of substances must be prevented and/or leaks must be minimized - i.e. in the transport and storage of almost all substances and chemicals.
Hydrogen, a lightweight among the chemical elements, is at first glance an unspectacular colorless, tasteless and odorless gas that consists of H2 molecules and is composed of a single proton and one electron. In terms of chemical resistance, hydrogen can initially be classified as an uncritical medium, so that a virtually free choice can be made from the range of sealing materials available on the market. Due to its low "weight" [density 0.0888 kg/m³], it could be assumed that hydrogen behaves more volatile than helium [density 0.1785 kg/m³], which in turn would have an impact on the leakage rates for existing flange connections. However, we were able to refute this assumption.
Flange connections on pipelines, heat exchangers, tanks, etc. are at best subjected to a mathematical strength and tightness test during their design, for example in accordance with DIN EN 1591-1. In this context, sealing parameters according to DIN EN 13555 are required, which refer to the mass with regard to leakage. Based on the molecular flow model, the figure shows the effect of the unit of leakage rate considered. A fictitious helium leakage of 10E-4 mbar * l / s served as a reference point.
The theoretical comparison shows that, assuming molecular flow conditions, hydrogen has a higher volume loss but a lower mass loss than helium. To verify these relationships, practical leakage measurements were carried out on an adhesive-free corrugated metal gasket with metallic inner rim and graphite overlays.
At present, however, only individual tests with hydrogen are available, from which no comprehensive conclusions can yet be drawn. However, it can be assumed that helium will continue to be used as a medium for leakage tests and that the design criteria for tight flange connections, e.g. according to TA Luft 2021, will continue to apply in the future.
Hydrogen can be used as an energy carrier in a variety of ways. It can be used as a fuel for vehicles powered by fuel cells, fed into the natural gas grid to generate electricity or heat, used as a raw material in the chemical industry, or traded worldwide as eFuel in the future like crude oil and natural gas. This area is also relevant for sealing technology.