How Hydrogen Could Shape the Future of Fluid Power Applications

By Daniel Hauser, Manager of Lead Group Hydrogen, Trelleborg Sealing Solutions

As the demand for cleaner energy grows, the transition to green hydrogen is gaining momentum. Green hydrogen (see sidebar) is produced through the electrolysis of water using renewable energy sources, such as wind, solar, or hydropower. This eliminates the carbon emissions associated with traditional hydrogen production methods. The shift aligns with global efforts to combat climate change; it also presents significant economic opportunities for developing new technologies and industries surrounding hydrogen production.

To fully realize its potential, investments must be made to advance electrolysis technology, improving energy efficiency and enhancing both storage and transport solutions. Using hydrogen as a fuel for applications like trucks, buses, and cars is an increasing topic of conversation.

The Present

Currently, hydrogen technology as it relates to vehicles is somewhat limited, fuel cells for forklifts and a small number of hydrogen-powered trucks and buses notwithstanding. Hydrogen internal combustion engines (ICEs) are being developed by major original equipment manufacturers (OEMs), and related vehicles are still in the prototype phase with concepts shared at trade shows. For many of these vehicles, it is likely the hydraulic systems responsible for work functions, such as cylinders, will not be in contact with hydrogen. However, any components that are part of the fuel system such as hoses, connectors, valves, and filters will have hydrogen as a medium to deal with rather than diesel or gasoline.

The Future

In the future, any component of the fuel system within the hydrogen engine of a vehicle would require some hydrogen-compatible materials to operate safely across multiple pressure cycles. In a traditional gasoline or diesel ICE, a standard nitrile O-Ring will seal components as intended but hydrogen creates complexities. Fluid power OEMs will need a reliable partner well-versed in which compounds are compatible with hydrogen.

The Challenge

Ensuring a dependable seal for hydrogen requires the use of cutting-edge materials and engineering methods. Doing so helps overcome challenges presented by hydrogen’s tiny molecular size, helping it permeate various substances. Sealing materials must exhibit exceptional compatibility and resistance to permeation to prevent any loss of gas.

Another significant concern is rapid gas decompression (RGD). In high-pressure environments, hydrogen molecules can infiltrate the sealing material. If there is a sudden pressure drop, the trapped gas within the seal can expand to adjust to the new ambient conditions, which may lead to seal blistering or cracking as the gas attempts to escape. Ultimately, seals used in various hydrogen systems must endure exceptionally challenging conditions, such as high pressures reaching up to 100 MPa (14,504 psi); this occurs particularly in high-pressure valves. Extreme low temperatures plummet to -250 °C / -418 °F, which are encountered in the storage and transportation of liquid hydrogen.

Hydrogen is a highly explosive gas that necessitates careful testing protocols, prompting many seal manufacturers to rely on third-party testing facilities.  To ensure safety during these assessments, helium is frequently employed as a proxy with test results adjusted to correspond to hydrogen values. However, helium does not serve as a flawless alternative, leading Trelleborg Sealing Solutions to invest in its facilities for hydrogen testing and proprietary test regimes to prove the performance of materials based on existing and enhanced versions of accepted standards.

Seals undergo rigorous testing according to enhanced proprietary versions of ISO 17268 for hydrogen compatibility and RGD. Regulation EC79 applies to components designed for hydrogen-powered vehicles. SAE J2600 applies to fueling connectors, nozzles, and receptacles for compressed hydrogen surface vehicles (CHSVs), alongside various permeation assessments. Additional evaluations cover a broad spectrum of static sealing cross-sections, including cyclic pressure tests with pressure ranges spanning from 0.7 to 75 MPa (101 to 10,877 psi) and temperature variations from -54 °C to +130 °C /-65 °F to +266 °F.

A partner focused on innovations in hydrogen sealing can provide a comprehensive suite of solutions designed to address future challenges for fluid power applications. Trelleborg’s H2Pro™ portfolio of over 20 materials exemplifies this dedication. These materials have been proven to perform in demanding application settings, offering suitability for high-pressure scenarios and low-temperature conditions while effectively resisting permeation. They are specifically designed to handle RGD and showcase exceptional wear and extrusion properties. The range includes two newly developed materials tailored for hydrogen applications. H2Pro™ EBT25 is an advanced ethylene propylene diene monomer rubber (EPDM) suited for high-pressure use over a broad temperature spectrum. Zurcon® H2Pro™ ZLT is a distinctive thermoplastic polyurethane (TPU) designed for very low-temperature applications.

Conclusion

The future of hydrogen for fluid power applications will continue to evolve. As it does, every participant in the value chain needs to evolve with it. Open communication between customers and suppliers will be critical. Those who choose to invest time and resources into this technology will be the ones who keep pace with the marketplace.