Automatic valves have been proposed for shutting off flows of liquids when abnormally large accelerations occur. These valves could be used, for example, to prevent outflows of flammable, valuable, or toxic liquids from pipelines that have been struck by vehicles or that have become involved in earthquakes or explosions. Actuation of the proposed valves would not depend on sources of electrical or fluid power, which would likely be unavailable during the emergencies in which the valves would be needed. Actuation would not even depend on pressurization of the liquids to be contained. Instead, the valves would operate similarly to spring-actuated rat traps, and like such traps, the valves could also be opened or closed manually.

Acceleration Would Trigger the mechanism by dislodging the ball from between the tips on the lever and the cocking stop. The spring would then act on the lever, turning the shaft to close the valve.

The shaft for opening and closing a typical proposed valve would be connected to a lever, which would be spring-loaded toward the closed position. The lever would be turned against the spring load to open the valve (see figure). At the fully open position, an approximately hemispherical tip on the lever would face a similar tip on a stationary cocking stop. An inertial triggering object (in a ball in the case illustrated) would be placed between the tips to keep the valve open. The ball would be held in place by spring force and associated friction. A sufficiently large acceleration would dislodge the ball, allowing the spring to turn the lever and shaft to the closed position. The triggering sensitivity would vary inversely with the inertial force needed to overcome friction to slide the ball out from between the tips; this force would depend on the choice of the materials, sizes, shapes, and surface finishes of the ball and tips.

This work was done by Andrew D. Morrison of Caltech for NASA's Jet Propulsion Laboratory. NPO-20114


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Emergency-shutoff valves would be triggered by accelerations

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NASA Tech Briefs Magazine

This article first appeared in the July, 1998 issue of NASA Tech Briefs Magazine.

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