O-rings for hydrogen turbines

Where O-rings are used in hydrogen turbines

The most logical applications are found in the cold to warm peripheral zones of the turbine installation. Think of fuel supply, fuel skids, fuel gas valves, filters, pressure regulators, analyzer panels, instrumentation ports, service connections and external purge or vent lines. In these zones, the seal is often static or only slightly dynamic. As a result, an O-ring, possibly with a backup ring, can be a technically and practically good fit.

For valves and control elements, extra nuance is needed. A body seal, stem seal and seat seal are not exposed to the same load. Body seals are usually static. Stem seals may experience slight movement. Seat seals mainly have to limit leakage under pressure. At higher pressure, with movement or a stricter leakage class, a standard elastomer O-ring can be replaced by a PTFE-based or spring-energized seal.

Around injectors and manifolds, the choice strongly depends on the distance to the burner. In cooler upstream manifold sections, an O-ring may still be suitable. Closer to the combustion zone, temperature and safety margin increase quickly. There, welded seals, graphite or metallic seals are often more logical.

Why H2 is different from natural gas

An O-ring that performs well in natural gas is not automatically suitable for H2 or H2/CH4 blends. Hydrogen molecules are small and can diffuse through polymers relatively easily. As a result, not only visible leakage along the sealing line plays a role, but also permeation through the material.

Rapid gas decompression can also occur. At high pressure, hydrogen can dissolve in the elastomer. If the pressure then drops quickly, that gas expands inside the O-ring. This can cause blistering, small cracks, pitting or permanent leakage. This risk increases with start-stop operation, blowdown, maintenance venting and pressure cycles.

The medium around the seal also matters. In turbine fuel systems, methane, traces of oil or grease, condensate, air, nitrogen or maintenance media may occur in addition to H2. That is why “hydrogen-resistant” is never enough as a standalone claim. The compound must match the complete medium, the temperature, the pressure and the way the system is used.

Material selection for O-rings in hydrogen turbines

FKM is often a strong candidate for fuel gas zones, especially when higher temperature, low gas permeation or possible oil and fuel influence play a role. Still, FKM is not an automatic choice. With hydrogen, the compound must also be assessed for permeation, RGD behaviour, temperature and leakage class.

FFKM offers more chemical and thermal margin. This makes it interesting for critical static seals in warm or demanding zones. The higher price makes FFKM especially logical when failure, leakage or maintenance costs weigh more heavily than material costs.

HNBR can be interesting in valve blocks, pressure regulators and mechanically loaded peripheral components. The material often offers a good balance between strength, wear resistance and extrusion resistance. NBR can be a practical option in milder, cooler zones, but has less temperature margin and ageing resistance than FKM or HNBR.

EPDM requires extra attention. The material is strong with water, steam, glycols and many polar media, but is usually not a logical choice in fuel gas paths where oil, grease or fuel contact is possible. For purge, water or auxiliary systems, EPDM can be suitable, provided the medium is correct.

PTFE, PEEK, graphite and metallic seals come into play when elastomers reach their limits. PTFE is interesting with chemical exposure, low friction or dynamic movement, but has less elastic recovery than rubber. PEEK is often used as a backup ring or anti-extrusion element. Graphite and metallic seals are better suited to warm flanges, higher leakage classes and zones where elastomer is not safe enough.

Design criteria for O-rings in H2 service

A good O-ring choice does not start with the material alone. The groove, squeeze, hardness, surface roughness, gap size and installation also determine whether the seal continues to function properly. At higher pressure or with pressure fluctuations, the extrusion gap is especially important. If the gap becomes too large, the edge of the O-ring can become damaged or be pressed into the gap.

Back-up rings help limit extrusion. In hydrogen systems, PTFE or PEEK back-up rings are often useful at higher pressure, with pressure pulses or when the seal is subjected to long-term load. They do not replace the O-ring, but support it mechanically.

System venting also plays a role. Excessively rapid depressurization can still damage a suitable compound. That is why it is wise to include blowdown and maintenance venting in the seal assessment.

For H2 service, compound-specific validations such as AED and NORSOK M710 are relevant. View which certificates are available for the O-rings in our range.

Practical selection per turbine zone

 
Each turbine zone has a different temperature range, from cold upstream manifolds to warm flange zones. View our material temperature resistance guide for an overview per elastomer.

Do you have a sealing question for a hydrogen turbine? Share the application, pressure, temperature, medium and groove size with us. We will be happy to help you think through a suitable O-ring material and indicate where extra validation or a different seal concept is needed.

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