Leakproof Valve

Ned Davis
Maui Innovation Group Inc.
Kihei, Hawaii

Valves often develop leaks as they age. This is disruptive, wasteful, and can cause damage in residential settings, but can be far more problematic in industrial applications. Factory lines may need to be shutdown to repack or replace valves resulting in lost production. Leaks can cause environmental damage and safety issues. In extreme cases, such as semiconductor manufacturing, even microscopic leaks can be fatal.

Most traditional valves have two moving seals: The seat where the flow of material through the valve is allowed, controlled, and shut off, and the stem seal that keeps the material from leaking out the penetration for the handle. A higher percentage of the leaks encountered in real-world valves are associated with the stem seals than the seat, because the stem seals tend to entrain dirt and grit from the surrounding environment, which erodes the mating surfaces over time — causing the seal to degrade and leak.

Previous seal-less valves often employed bending or flexing components such as bellows or membranes that can degrade or fatigue also causing leaks over the long term if not carefully monitored. Previous generations of magnetic valves operated in a linear solenoid on-off manner, and/or had limitations making high-temperature operation difficult to achieve, precluding hermetic sealing such as brazing or soldering the valve body shut, and often requiring continuous power to maintain their position.

Previous magnetic valves often had torque limitations and lacked effective methods to break free badly corroded valves that hadn’t been actuated for a long time. These limitations curtailed the practicality of previous generations of sealed valves and limited their application to niche markets.

Inventor Ned Davis’s recent work changed all of this. Rather than relying on pairs of opposing magnets facing each other across a sealed interface, his design creates a magnetic flux circuit that is completed thru a magnetically asymmetric core within the sealed valve — magnetic poles outside of the sealed valve interact with each other via a magnetically conductive path traversing the valve — and this magnetic flux path has preferred orientations. This novel approach allows the magnets to be placed outside of the sealed portion of the valve and away from temperature extremes and caustic working fluids.

“We were on the deck of a boat off the coast of Oahu working on a wave energy harvesting project that I was doing for the Office of Naval Research 15 years ago or so, and my technicians were spending more time fixing and draining that machine than it was spending in the water generating any energy,” said Davis. “I said to myself that there must be a better way, and I thought of those little magnetic pellets spinning in laboratory beakers and came up with a magnetic coupling instead of a packing. Then we applied it to magnetic valves and magnetic gears too,” he added.

Because there aren’t any permanent magnets inside the sealed valve, the valve body can be sealed shut, for example, via high heat processes such as welding that would ruin many permanent magnets — especially modern powerful neodymium magnets that tend to have very low Curie temperatures (the temperature at which the magnet would lose its magnetism and need to be re-magnetized). Furthermore, the Curie temperature of modern neodymium magnets is so low that they typically could not even be employed inside steam valves, nevermind welding, hence sacrificing many of the most important applications. These valves suffer no such temperature limitations.

Key technical challenges in bringing this technology to market include the risk of stuck valve conditions, challenges of creating and testing the valves in operational conditions, including material compatibility requirements, torque requirements, and safety requirements imposed on valves in real-world conditions especially handling dangerous substances.

According to Davis, they have six U.S. patents and 13 international patents on this technology as of now. “We have sold a few valves to end users such as big petrochemical companies for evaluation purposes, and we have built prototypes and experiments for big valve manufacturers such as Emerson, Crane, and Flowserve. We hope that one of these companies will license or buy the patents from us in the future — I think that is a much more realistic commercialization plan than trying to manufacture large quantities of valves ourselves,” he said.

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