In a hydrogen system operating at 10,152 or 14,500 psi, every shut-off component is a safety decision. H2 is the smallest molecule in nature, has flammability limits between 4% and 75% in air, and requires an extremely low ignition energy. A wrong choice of valve or actuation logic does not result in a manageable leak: it results in a structural risk for the entire system. For engineers working in the industrial gas and hydrogen sector — refuelling stations, compression skids, test benches, storage systems — the question to answer is precise: how to shut off hydrogen at these pressures safely, reliably and in ATEX compliance, even when everything else stops working? The answer lies in two complementary technologies: pneumatically operated high-pressure manual and actuated valves from the HIP series and the Seitz HyValve ultra-high-pressure solenoid valves.
The concept is straightforward in theory and demanding in execution: a Normally Closed (NC) valve requires energy — electrical or pneumatic — to open. If energy is lost, the valve closes automatically.
In a hydrogen system, this means that a blackout, a failure of the pilot air compressor, or an ESD emergency signal all produce the same result: H2 lines are isolated instantly.
This logic applies to two product families with very different characteristics, worth analysing separately before comparing them.
High Pressure Equipment Company (HIP) manufactures two series of pneumatic actuators for high-pressure valves up to 20,000 psi (approximately 1,380 bar): the Hipco Diaphragm Air Operators and the Hippo Piston Air Operators.
The structural advantage for hydrogen applications is significant: being driven exclusively by compressed air, they have no electrical component on the valve body. This makes them intrinsically safe for ATEX IIC zones, without the need for explosion-proof enclosures. The electrical control element — the pilot solenoid — can be located remotely, in a safe area.
How they work in fail-safe NC configuration: a robust mechanical spring keeps the valve closed. To open the gas passage, low-pressure compressed air (55–100 psi) is supplied to the actuator, overcoming the spring force. If air is lost for any reason, the spring seals the valve by purely mechanical means, blocking hydrogen at 20,000 psi.
The two actuators address different application requirements:
Hipco Diaphragm uses a large flexible diaphragm (6 7/8" diameter) that generates high thrust forces at low pilot pressures. For an NC valve at 20,000 psi, approximately 60–100 psi is sufficient to begin opening and 90 psi to complete it. It is the preferred solution for heavy-duty service where radial space is not a constraint.
Hippo Piston uses a sliding piston mechanism in a cylinder, with a more vertical profile and a smaller radial footprint. Available in Medium Duty, Heavy Duty and Extra Heavy Duty variants, with Extra Heavy Duty versions capable of handling orifices up to 9/16" at 20,000 psi. It is the ideal choice for gas control panels and manifolds with closely spaced valves, as well as for highly cyclic applications where piston mechanical robustness is critical.
Both series are mounted on 316 stainless steel valve bodies, compatible with H2, and fitted with high-pressure cone-and-thread connections — the only joining technology that guarantees metal-to-metal sealing up to 20,000 psi.
Where direct shut-off is required — without external pneumatic circuits — the Seitz HyValve solenoid valves are the technical reference alternative. The fail-safe NC principle is the same: the solenoid requires current (24 V or 230 V) to keep the plug open. If voltage drops, the valve closes in fractions of a second.
The HyValve range covers operating pressures up to 1,000 bar (14,500 psi), with ATEX II 2G certification (Ex mb IIC T4), 100% duty cycle and a thermal range from -50°C to +65°C. Test pressures reach 1,500 bar in accordance with DIN EN 12516-3.
For refuelling stations and compression skids where space is critical, Seitz has developed the Mosaic system: a modular matrix integrating from 2 to 40 NC 2/2-way solenoid valves in a single compact block. Each valve can be removed individually for in-situ maintenance without shutting down the entire system. Integrated check valves further optimise space management.
The two technologies are not interchangeable: they complement each other. The choice depends primarily on system sizing and on the role the valve is required to perform.
HIP pneumatic valves (Hipco/Hippo) are the most appropriate solution for main process lines, Emergency Shutdown Valves (ESDV) and test benches where hydrogen must be isolated at extreme pressures up to 20,000 psi with a purely mechanical fail-safe logic, without local electrical dependency.
Seitz HyValve solenoid valves are the preferred solution for HRS distribution panels, compact skids and applications requiring very fast response times, high-frequency cycles (100% duty cycle) and the elimination of pneumatic pilot tubing.
In many real-world systems, both technologies coexist: HIP pneumatic valves on the main ultra-high-pressure lines (isolation and safety), Seitz HyValve on distribution and control circuits on board the skid.
During burst or leak tests on tanks and valves, operators are positioned in protected areas. Hipco/Hippo valves allow pressurisation, isolation and discharge of test lines up to 20,000 psi from the remote control room, automating fatigue cycles in complete safety. A concrete application is documented in our article on high-pressure testing experiences.
In cylinder packs where hydrogen is stored at 500–1,000 bar, NC pneumatic valves act as ESDV. The Seitz Mosaic system manages distribution on board the dispenser. For an overview of how the hydrogen supply chain works from production to storage, the dedicated article on how the hydrogen supply chain works is a useful reference.
From the electrolyser (15 bar) to storage at 1,000 bar in ATEX IIC zones, with intermediate isolation at each stage. An application context in which the choice of shut-off technology — pneumatic or electric — directly affects the reliability of the entire production cycle.
These components are manufactured by world-class suppliers — HIP in Erie (Pennsylvania), Seitz in Kemptthal (Switzerland).
As Interfluid HP Division, we operate in full technical partnership with HIP, Seitz, HII and Bürkert — not as simple resellers, but as the local technical reference for Italian H2 system designers.
By contacting us for a hydrogen project, the same level of technical support available through direct contact with the manufacturer is available, with the added advantage of communication in Italian, a local warehouse in Gallarate, and the availability of one of our engineers for support during the design phase.
With over ten years of experience in hydrogen and the design of Italy's first H2 test system at 1,000 bar for a major certification body, the HP Division is able to support engineering from requirements analysis through component selection, including high-pressure rigid tubing, fittings and shut-off systems such as those described in this article. A technical heritage that turns the complexity of high-pressure H2 into a structured design process.