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Blog posts of '2022' 'October'

All About Shut-Off Valves

At JMI Pump Systems, we have an assortment of shut-off valves for your pumping applications. You'll find ball, gate, and globe types and other options available, plus valves are available in different materials, including bronze, brass, and PVC plastic. It is important keep in mind that it’s imperative to choose materials appropriate to the application of the pump system.

Ball Valves

Ball valves control water flow by using a rotational ball with a hollow core through its center. Attached to the top of the ball valve is a lever whose range of movement is a short quarter turn. When the handle is parallel to the water supply pipe, the valve is open as the ball aligns with the water flow. When the lever is perpendicular, the valve is closed. The solid section of the ball rotates 90 degrees and blocks the water flow.

Advantages to ball valves is they can be turned off quickly, they have longevity, and they are not prone to leaks or premature failure. However, closing the valve too quickly can cause water hammer. Clogging can occur when it’s handling water with a large amount of sediment, in which case a sediment filter should be installed to eliminate dirt and debris.

A ball valve should not be used for throttling because the seat of the ball valve will erode, and the valve will fail.

Gate Valves

Gate valves are designed to be either fully open or fully closed. As the name suggests, gate valves are equipped with a wedge-shaped metal gate that can be lowered to halt water flow and raised to allow flow to continue. The gate is controlled by a circular handle or wheel-shaped knob located at the top of the valve. Turning the knob gradually lowers the gate into the valve. Because they open and close slowly, water hammer is avoided.

A disadvantage to gate valves is they are prone to corrosion resulting in failure. Also, gate valves should not be used in application where the water needs to be turned on and off regularly. In this case, a ball valve is the better choice. As with ball valves, gate valves should not be used for throttle pressure.

Globe Valves

Globe valves, used to regulate or throttle the water flow, are spherically shaped, although with a bulge. Inside the globe is a stopper at the end of a valve stem, called a disc or plug. The stem is operated by turning a handwheel knob. It can be opened all the way up, sealed closed or partially open to reduce flow or increase head pressure.

Also, inside the globe housing is a “seat,” a metal frame that divides the body into two chambers and has a hole to allow fluid to pass. Turning the valve stem until the disc is into the seat closes the valve preventing fluid from flowing through. When the valve is open, the fluid flows through the space between the edge of the disc and the seat. Besides being closed or open, they can also be partially open to adjust flow without stopping it.

A disadvantage to globe valves is a higher pressure drop because when fluids change direction, it results in greater resistance against the flow. Unless of course the intention is to increase back pressure.

Some options include combination valves with an elbow, check valves with a gate valve, or a combination of the three. Additional information is addressed in our Szuster Ball Check Valves blog from December 2021.

For more information on shut-off valves available from JMI Pump Systems and for assistance on any pumping application, contact us at 262-253-1353 or sales@jmipumps.com.