HYDROGEN
These effects make material selection and qualification particularly important for valves operating in hydrogen rich environments.
Seal creep and loss of sealing force
One of the most common failure mechanisms observed in valve systems is creep, or the gradual deformation of a material when it is subjected to constant load over an extended period. In valve assemblies, sealing components are typically compressed to maintain a tight sealing interface. When materials creep under sustained pressure, the contact force between sealing surfaces gradually decreases. Over time, this reduction in sealing force can create micro-gaps throughwhich hydrogen can escape. Hydrogen molecules are extremely small and need higher sealing pressures relative to other gases. These higher pressures can worsen creep or stress relaxation that results in a reduction in sealing force. Thus, leakage can occur through clearances that would remain sealed when managing other gases. In hydrogen service, the acceptable margin for dimensionalchange is therefore much smaller. Temperature can also accelerate this process. Hydrogen compression and storage systems often operate across wide thermal ranges, placing additional stress on sealing materials. For example, in an API 618 compressor, gas may enter the system at or near ambient temperature and reach discharge temperatures of up to 329 ° F under high-pressure conditions. These fluctuations subject materials to repeated thermal expansion and softening cycles. Under elevated temperature conditions, many conventional polymer materials lose stiffness and become more susceptible to deformation and creep. When combined with sustained mechanical loading and hydrogen permeation, this thermal cycling can significantly accelerate the degradation of sealing performance, increasing the risk of leakage over time.
Seat deformation and structural instability
Valve seats also face particularly demanding conditions in hydrogen applications. They must maintain a tight shutoff under high pressure while resisting mechanical wear from repeated actuation cycles. Traditional seat materials can gradually deform under these conditions, particularly when exposed to sustained compression. Over time, this deformation alters the geometry of the sealing interface, reducing the ability of the valve to achieve reliable shutoff. Hydrogen service can also exacerbate material degradation through permeation
Diffusion rates for hydrogen in many polymers can be several times higher than for larger molecules, increasing the likelihood of permeation over time.
and chemical exposure. In systems where valves remain closed for extended periods, the constant mechanical load placed on the seat material increases the likelihood of long-term deformation. Even small dimensional shifts can compromise sealing performance in high-pressure hydrogen systems. Leakage in hydrogen systems presents a serious operational challenge. Hydrogen has a very wide flammability range and an extremely low ignition energy, meaning that even small leaks can pose safety risks in confined environments. Several mechanisms can contribute to hydrogen leakage in valves. Diffusion through sealing materials is one pathway, particularly when polymers with relatively high permeability are used in high-pressure environments. Mechanical relaxation of seals due to creep is another common cause. Pressure cycling can also accelerate leakage. Hydrogen infrastructure frequently experiences fluctuating pressures during compression and distribution, placing additional stress on sealing materials and increasing the risk of fatigue-induced failures. These combined factors mean that materials used in hydrogen valve components must maintain their mechanical properties under conditions that are significantly more demanding than those encountered in conventional gas systems.
Greene Tweed’ s Arlon 3000XT seals consist of high-performance thermoplastic, developed to enhance durability under extreme industrial conditions.
Closing the material performance gap
Many conventional sealing materials were developed for hydrocarbon service, where gas molecules are larger, permeation rates
68 Valve World November 2026 www. valve-world. net