No-leak valve developed for industrial fluid control

An inventor has combined a 17th-century mathematical theory with computer-aided design to create a no-leak valve.

"All valves wear, and eventually they leak," said John Wordin, the valve's inventor, a scientist at the U.S. Department of Energy's (DOE) Idaho National Engineering and Environmental Laboratory, Idaho Falls, Idaho. "But the reason they leak is not because of wear, it's because they wear unevenly and no longer form a tight seal."

The new valve is named after the mathematical curve that inspired its design - a tractrix. Also known as Schiele's Pivot, a tractix is unique in that it is the only shape that fits the physics of uniform wear. When applied to both the valve body and mating surface, the tractrix shape results in a valve that wears evenly along the surface, doesn't leak and forms an ever-tighter seal the more it is used. It also has low torque requirements, comparable to a soft-seated ball valve.

"I first learned of the tractrix curve 35 years ago in college calculus," said Wordin. "Though the theory's been around since 1692, it took the precision of computer-aided machining to put it into practice."

The resulting valve resembles a plug valve with some modifications. Because wear is not a concern, it can be constructed out of any valve material, saving cost and offering better compatibility in many fluid control environments.

While the valve is currently being tested for use in the oil and gas industry, it could have wide application in chemical and hazardous materials processing, the pulp and paper industry, and food processing.

For more information, contact Pio Park, PMC/Tractix Corp., Seattle, at (206) 783-0839 or via e-mail at

This article originally appeared in the November, 1999 issue of Environmental Protection magazine, Vol. 10, Number 11, p. 8.

This article originally appeared in the 11/01/1999 issue of Environmental Protection.

About the Author

Gerald F. Connell, ChE is a consultant, retired after 30 years with Capital Controls Group, Severn Trent Service Inc., Colmar, Pa. Mr. Connell is author of "The Chlorination/Chloramination Handbook," published by the American Water Works, and a forthcoming "Chlorination/Dechlorination Handbook" to be published by WEF.

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