Understanding Emergency-Shut-Down Valves in Electrolyzer Systems

In the world today, energy usage is hitting the limits of traditional technologies. At PCS, we continue to see a significant increase of our customers’ focus and attention for electrolysis applications. With the current interest for Hydrogen related technologies, emergency shutdown is a particularly relevant topic.  

The precision and stability of pressure control is crucial to ensure process safety and efficiency in hydrogen electrolyser systems. Emergency shutdown valves (or “ESD”, in short) are a key element in this. The team of Pressure Control Solutions is regularly consulted about the technical details and benefits of Equilibar ESD valves and application thereof in electrolyzers.

Challenges of Emergency Shutdown procedures

Emergency shutdown valves are critical and necessary for a safe electrolyzer design and necessary for effective safety procedures. They are instrumental to safely depressurize the electrolyzer system in the event of emergency or initiation of the depressurization procedure. Such emergency can come from power failure or other disruptions in the electrolysis process. The depressurization procedure can be triggered also for other reasons.

ESD valves are meant to help prevent damage to the electrolyzer membranes and avoid cross-flow through the diaphragm during depressurization. As stated above, precise and stable pressure control are of vital importance to ensure safety during this depressurization:

• The mass flow rates of oxygen and hydrogen will show significant differences, and the pressure differential between both sides must kept within limits to avoid rupture of the electrolyser membranes. This requires very precise and accurate control of  the differential pressure.
• Mixture and contamination of gases must be avoided during depressurization, especially when working with explosive and flammable gases and fluids, like H2 and O2.

Factors like high pressure at the start of depressurization, condensation and presence of explosion risk can present process engineers with complex challenges and makes the effectiveness and robustness of the emergency shutdown design all the more relevant.

Details & Benefits of Equilibar ESD valves

• Equilibar ESD valves are designed with a large diaphragm and work in combination with an external pilot gas system (not supplied by PCS). These valves use a unique center inlet design and a specifically for this purpose designed orifice pattern.
• The pilot gas can come from a reservoir or be sourced from the oxygen side of the system. This design allows for precise control of the pressure differential during an emergency shutdown , by maintaining a small pressure difference during the shutdown process.
• Equilibar valves are fully mechanical, ensuring precise and reliable operation without using an electronic controller. This simplicity enhances the system’s robustness and reduces potential points of failure.
• Maintaining a small pressure difference is essential to avoid damaging the membranes in the electrolyser. Equilibar ESD valves help prevent such damage, minimizing friction and overpressure. This design ensures a better and ultra-precise agreement between pilot pressure and process pressure, and that is of crucial importance for electrolyzer systems.
• During an emergency shutdown, Equilibar ESD valves ensure a slow decay of pilot pressure yet with a smooth logarithmic ramp, allowing the system to depressurize gradually. This controlled depressurization helps maintain the pressure differential within acceptable limits, typically below 50 millibars over a range from 50.000 mbar down to atmospheric pressure.
• Another important benefit is that Equilibar ESD valves prevent cross-overflow of process media. This is obviously crucial when using explosive mixtures that should not get in contact with each other.

Customer Feedback about the use of Equilibar ESD Valves

Customers who use the Equilibar ESD valve have confirmed with their feedback that this solutions works well for them, which demonstrates the effectiveness of Equilibar ESD valves.

For example, a lead engineer with a European alkaline electrolyzer manufacturer proved that with the Equilibar ESD valve, he was capable of reaching differential pressure of only 17 millibars during a blow-off from 13 bar. This result showcases the ability of our ESD valve to maintain precise control.

Want to know more?

We are looking forward to help you with any questions you may have about Equilibar ESD valves. More information can also be found on the website Equilibar in this blog about Shutdown Valves or ESD Overview Page.

Or watch this video demonstrating the use of Equilibar ESD valves.