Permeation and RGD resistance for high pressure gaseous hydrogen applications
Cryogenic sealing capability for liquid hydrogen storage applications
Chemical resistance for sealing hydrogen carriers such methanol and ammonia
Rubber-metal and rubber-plastic seals for high volume components in fuel cells and electrolysers
Depending on the exact application hydrogen can be sealed as both a gas and a liquid. Different conditions must be considered for both, but generally chemical compatibility is not an issue and most seal materials are suitable. For hydrogen seal applications with no particular challenging demands in any one area, EPDM elastomer based solutions are often the most cost effective.
When hydrogen is in liquid form the main application consideration is very cold/cryogenic temperatures of -253°C. Elastomers are not suitable for these low temperatures so PTFE seals are often the compatible choice.
The application challenges when sealing hydrogen as a gas centre around high pressure conditions (700 bar +), permeation through the seal material and the potential for rapid gas decompression. For permeation resistance, we can offer chlorobutyl elastomer or polyurethane seals. For high pressure applications, elastomers or polyurethanes with high extrusion resistance and resistance to rapid gas decompression (or PTFE which is not affected by RGD) can be used.
It's not easy to store, transport, or use hydrogen in large amounts in its liquid or gas form, so it's popular to store and transport it as either methanol or ammonia. The hydrogen is then separated out at the point of use when required (for use in the fuel cell or for simply burning it). When sealing these liquids often temperatures and pressures are not challenging, but chemical compatibility needs consideration as FKM is not compatible. Generally EPDM seals are the best choice.
In electrolysers and fuel cells, the purity and cleanliness requirements can be met with materials and treatments we frequently use within the semiconductor market. For applications below -60°C, elastomers become hard and brittle, but PTFE, PCTFE and metal sealing solutions can be used down to cryogenic temperatures. For high temperature applications, some FKM or even FFKM elastomers can be used up to 220°C or even 300°C but the normal preference here would be PTFE sealing solutions.
Metal seals are capable of even higher temperatures up to around 870°C. Metal seals can also have soft coatings such as tin or indium to achieve gas tight sealing, or gold or silver to reduce the risk of hydrogen embrittlement.