• SPECIAL TOPIC: HYDROGEN / RENEWABLE ENERGY •
solubility and diffusion rates within sealing materials, accelerating permeation effects.
This combination of pressure, diffusion, and sustained loading gradually alters material properties. Seals may swell or soften. In valve assemblies where tight tolerances are essential for leak-tight performance, even slight changes in material behaviour can compromise sealing integrity.
Hydrogen also introduces additional risks for metallic components. Multiple metals used in conventional energy infrastructure are susceptible to hydrogen embrittlement, where absorbed hydrogen weakens the material structure and increases the risk of cracking or sudden failure. Highstrength alloy steels, commonly used in pressure-containing components, are particularly vulnerable, while certain grades of stainless steel can also experience degradation under hydrogen exposure.
These effects make material selection and qualification particularly important for valves operating in hydrogen-rich environments.
Greene Tweed’ s Arlon 3000XT seals consist of high-performance thermoplastic, developed to enhance durability under extreme industrial conditions.
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 through which 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 dimensional change 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.
Diffusion rates for hydrogen in many polymers can be several times higher than for larger molecules, increasing the likelihood of permeation 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 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
Valve World Americas | June 2026 | www. valve-world-americas. com 19