How a Gate Valve Works

The Nature of a Gate Valve

Gate valves are meant to be fully open or fully closed.

A gate valve consists of an actuator---such as a lever, a hand wheel or an electric motor---a housing, which holds the valve mechanism, and a gate---a rectangular or circular piece of metal that acts like the gate on a fence. When the gate is raised, liquids or gases can pass through the gate. When the gate is closed, the flow stops.

The best-known example of a gate valve is a household faucet: when you turn the handle, you raise or lower the gate and the water flows or stops.

Opening the Gate Valve

Most gate valves are operated by a handle, whether the handle is a lever or a hand wheel, like the knob on a faucet. If you turn the handle counterclockwise, the gate raises. If you turn the handle clockwise, the gate drops.

Gate valves are used in many industrial settings and, in such a setting, the valve may be controlled by an electric motor operated either on command from a human or computer, or automatically, perhaps by a timer.

Gate valves should not be used to restrict flow; that is, they should not be partially opened. Using a gate valve to restrict flow puts unnecessary strain on the gate and the supporting structures, particularly in a high-pressure setting. This strain will eventually cause the mechanical failure of the valve.

Ideally, when you open a gate valve using a hand wheel, you should open the valve all the way by turning the hand wheel counterclockwise until it stops, then turn the hand wheel 1/4 turn clockwise. This will prevent the gate from being jammed by the pressure from the flow of the liquid.

Closing the Gate Valve

Closing a gate valve is slightly more than a matter of turning the hand wheel clockwise until you can't turn it anymore, then leaning into it with a crowbar and your full weight. Instead, you should close the gate valve only until the flow of liquid stops---whether you can see it or a flow gauge indicates the flow has ceased.

Applying excessive pressure to a gate valve to make it close "all the way" has the effect of bending the gate, its seat or seal and doing permanent damage. If a gate valve drips or leaks, the correct course of action is to put the valve out of service until it can be repaired or replaced.

About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.