When we actually think about it , a lot of valves are stemless , for example the ubiquitous solenoid valve , which imparts force electromagnetically through the wall of the valve to operate . However , like all stemless valves , there are compromises . For solenoid valves there is a limit to the size / pressure this solution can handle , and / or a reliance on pilot pressure to operate . For larger valves , replacing the dynamic stem seals with a metallic flexible bellows presents a solution . However , bellows are large and cycle fatigue life limited ( particularly at higher pressures ). In addition , they are predominantly applied to linear operating valves , designs that have just a fraction of the flow capacity of other equivalently sized valves . π www . valve-world . net Valve World December 2024
Actuation Lab has developed an innovative stemless valve that Uses a magnetic coupling and torque amplification to eliminate emissions while maintaining high performance . This breakthrough could prevent millions of tons of greenhouse gas emissions and is ideal for hydrogen , toxic chemical and cryogenic applications .
Dr Michael Dicker , CEng – CTO and Co-founder , Actuation Lab
Zero-Leak Valve Design
Zero emissions stemless valve : A leak-free solution
Figure
1 : Simulation showing the volume of a containerised hydrogen system that would fall into the explosive limit ( all colours ) should a maximum DSEAR sized stem seal failure occur . This is after just 5 seconds , for a system at 400 bar , with standard 1000 m 3 / hr mechanical ventilation of the container .
A
stemless valve is one which has no operating shaft passing through the valve body . This means stemless valves do not contain dynamic seals to atmosphere ( e . g . packing ), which are prone to wear and / or damage from eroded or corroded shafts , leading to fugitive emissions .
Why do we care about stem leakage ?
Stemless valves are key to the safe operation of valves handling very aggressive or toxic fluids ( e . g . chlorine ), and are also used extensively for cryogenic applications where extremely low temperatures present a challenge to the effectiveness of stem seals . Increasingly , stemless Valves are also being employed to provide a zero-emission solution where stem leakage has a global warming impact . Methane , the main component in natural gas , has 28 times the planet warming impact of carbon dioxide when it escapes to atmosphere . Even hydrogen , a clean burning fuel of the future , has an indirect impact 11 times worse than the equivalent amount of carbon dioxide . With hydrogen ’ s small molecular size resulting in it leaking much faster than natural gas , the climate impact of leaking valve stems will remain even if we phase out natural gas . Actuation Lab has performed studies that indicate around 93 million tons of carbon dioxide equivalent warming gas ( methane ) is emitted from leaking valve stems every year . Solving this stem leakage problem would have the same climate impact as removing all the cars and trucks from UK roads ! Leakage of gases like hydrogen , with its wide explosive limits ( 4-75 %) is also a great motivator for the use of inherently leak free stemless valves . With many developers of hydrogen systems exploring containerised solutions , it takes only a small leak to trigger gas alarms in these confined spaces , leading to costly shutdowns ( Figure 1 ). Additional financial benefits to adopting stemless valves include eliminating or reducing the cost of lost product , leakage detection and repair . With these benefits , we might ask the question …
Why aren ’ t all valves stemless ?
When we actually think about it , a lot of valves are stemless , for example the ubiquitous solenoid valve , which imparts force electromagnetically through the wall of the valve to operate . However , like all stemless valves , there are compromises . For solenoid valves there is a limit to the size / pressure this solution can handle , and / or a reliance on pilot pressure to operate . For larger valves , replacing the dynamic stem seals with a metallic flexible bellows presents a solution . However , bellows are large and cycle fatigue life limited ( particularly at higher pressures ). In addition , they are predominantly applied to linear operating valves , designs that have just a fraction of the flow capacity of other equivalently sized valves . π www . valve-world . net Valve World December 2024
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