Solenoid Valves for Hydrogen Gas: Materials, Certification and Selection
Hydrogen is fast becoming a mainstream industrial and energy gas, driven by electrolysers, fuel cells, hydrogen refuelling and the blending of hydrogen into the natural gas grid. But hydrogen is not simply "another gas" from a valve engineer's point of view. Its very small molecule, wide flammability range and low ignition energy mean that a solenoid valve specified for natural gas or compressed air is not automatically suitable for hydrogen service. This guide explains what actually changes when you switch media to hydrogen, and how to specify a solenoid valve you can rely on.
Why Hydrogen Is Different
Hydrogen (H2) is the smallest and lightest molecule there is, and that single fact drives most of the engineering. Because the molecule is so small, it finds leak paths that would comfortably hold back air, nitrogen or even natural gas, so external leak-tightness becomes the dominant design concern rather than an afterthought. Hydrogen also permeates through many elastomers over time and can, under the right conditions, diffuse into the crystal structure of certain metals.
On the safety side, hydrogen has an exceptionally wide flammability range in air (roughly 4% to 75% by volume) and a very low minimum ignition energy, so even a small static discharge can ignite a leaked mixture. Its flame is almost invisible in daylight and it burns with little radiant heat, which makes leaks harder to detect. For the valve engineer this means two priorities: keep the gas contained, and assume that any hazardous-area classification will be strict.
Body and Wetted Metal Selection
The main pitfall to avoid is hydrogen embrittlement. High-strength steels and some hardened components can lose ductility when exposed to hydrogen, particularly at elevated pressure, which is why they are generally avoided in hydrogen wetted parts. Austenitic stainless steels such as 316/316L are widely regarded as resistant to hydrogen embrittlement and are the default choice for higher-pressure and safety-critical hydrogen duties. Brass is commonly accepted for lower-pressure hydrogen applications and remains a cost-effective option where pressures are modest, but the higher the pressure and the more critical the duty, the stronger the case for stainless steel. Because material behaviour is pressure and grade dependent, confirm the specific alloy and pressure rating with your supplier rather than assuming a body material is "hydrogen-safe" in all cases.
Seals, Diaphragms and Soft Parts
Elastomer choice matters for two reasons with hydrogen: chemical compatibility and gas permeation. Hydrogen is chemically compatible with most common seal materials, so the more subtle issue is permeation and the phenomenon of explosive (rapid gas) decompression, where absorbed gas expands when pressure is released quickly and can blister or tear a seal. EPDM, FKM (Viton) and PTFE are frequently used in hydrogen service, with the best choice depending on the pressure, temperature range and cycling regime. For rapidly cycling or high-pressure duties, a seal specifically rated for gas decompression resistance is worth specifying. If you are unsure which elastomer suits your conditions, our seal materials guide explains the trade-offs.
Material Suitability at a Glance
| Component | Generally suitable | Use with caution | Key reason |
|---|---|---|---|
| Body – higher pressure / critical | 316 / 316L stainless steel | High-strength steels | Resistance to hydrogen embrittlement |
| Body – lower pressure | Brass, 316 stainless | — | Cost vs. duty balance |
| Seals / diaphragm | EPDM, FKM (Viton), PTFE | Fast-cycling seals not rated for decompression | Permeation & explosive decompression |
| Electrical / coil | ATEX/IECEx certified coil for zoned areas | Standard coils in hazardous zones | Ignition risk in flammable atmospheres |
Certification and Hazardous Areas
Most hydrogen installations create at least a localised explosive atmosphere, so the valve's electrical parts usually need to be certified for the relevant zone. In the UK and Europe that means ATEX (and internationally IECEx) approval for the coil and, where required, the whole assembly. Our overview of ATEX solenoid valves explains the zone and gas-group concepts, and it is worth confirming that any certification explicitly covers gas group IIC, which includes hydrogen, rather than only the more common IIA/IIB groups. For gas-train and burner duties, look additionally for the safety-shut-off approvals that apply to combustion gas valves. Because hydrogen-specific product standards are still maturing, treat manufacturer test evidence and third-party certification as essential documentation, and ask for it up front.
Valve Type and Fail-Safe Behaviour
For hydrogen shut-off the overwhelming default is a normally closed (NC) valve, so that loss of power fails the system to a safe, closed state. Whether you choose a direct-acting or a pilot-operated (servo-assisted) valve depends on flow and pressure: direct-acting valves work down to zero differential pressure and suit small, safety-critical lines, while pilot-operated valves handle higher flows but need a minimum pressure differential to stay open. Fast, reliable closing is valuable in a hydrogen safety circuit, and many gas-safety designs are engineered to close in under a second. If you are weighing these options, our guide on how to choose a solenoid valve walks through the wider selection logic.
Sizing and Leak-Tightness
Hydrogen's very low density means that, for a given valve orifice and pressure drop, the achievable mass flow behaves quite differently from air or natural gas; a valve sized purely on a compressed-air flow figure can be mis-sized for hydrogen. Where you have a defined flow requirement, size against manufacturer data expressed for the actual medium rather than reusing an air rating. Just as important is internal and external leak-tightness: for hydrogen it is good practice to specify a bubble-tight (or better) seat and to expect the manufacturer to have leak-tested the assembly, ideally with helium or hydrogen. Ancillary items such as fittings, gaskets and connectors deserve the same scrutiny as the valve itself, because a hydrogen system is only as tight as its weakest joint.
Typical Hydrogen Applications
Solenoid valves appear throughout the hydrogen chain: isolating and dosing gas in electrolysers, controlling supply to fuel cells, sequencing and shutting off gas in refuelling equipment, managing hydrogen blends entering existing gas networks, and handling hydrogen in laboratory, heat-treatment and metallurgical furnace atmospheres. Many of these overlap with the requirements for other fuel and specialty gases, so if your process also involves other media it is worth reviewing our related range of natural gas solenoid valves, which share much of the same safety philosophy.
Getting the Specification Right
Hydrogen rewards careful specification: choose an embrittlement-resistant body for the pressure involved, a seal rated for the cycling and decompression regime, ATEX/IECEx electrics suited to a IIC atmosphere, and a fail-safe normally closed action with proven leak-tightness. Because so much depends on the exact pressure, temperature and duty of your system, hydrogen is one application where it genuinely pays to confirm the details before you order. Try our Valve Search Wizard to narrow down suitable options, or contact our technical team with your operating conditions and we will help you specify a valve that keeps your hydrogen safely under control.