Check valves, also called non-return valves (NRV), are essential components of any industrial or residential piping system. They are used to prevent backflow, ensuring the proper operation of the system and preventing damage from happening.
Check valves work fairly simply. Pressure from the liquid that is flowing through a piping system opens the valve while any flow-reversal will close the valve. It allows the fluid to flow fully unobstructed in one direction and automatically closes as the pressure is reduced. While that is pretty straightforward, there are different types of check valves, with varying operations and applications. How do you know which type of check valve to use for your job or project? To help you make the right choice, here are some details about the most common types of check valves.
Swing check valves utilize a disc inside the valve to allow or stop the flow of the piping system. As the fluid flows through in the correct direction, the pressure forces the disc to open and stay open. As the pressure decreases, the valve disc closes, stopping the flow of the fluid from reversing. Swing Check Valves come in a wide range of material types, including PVC, CPVC, Clear and Industrial.
There are two types of swing check valves we should look at:
• Top-hinged – In this type of swing check valve, the disc is attached to the inner top of the valve with a hinge that allows the disc to open and close.
• Tilting disc – This type of swing check valve is designed in a manner that allows the valve to fully open at lower flow pressure and to close quickly. It does this using a dome-shaped disc that is spring loaded to make the valve close faster than a top-hinged valve. Additionally, the disc in this check valve floats so that the liquid flows on the top and bottom of the disc surfaces.
These types of check valves are most commonly used to prevent flooding in sewage systems and in firefighting applications. They are used in systems that move liquids, gases, and other kinds of media.
Lift check valves most closely resemble globe valves. They utilize a piston or a ball in place of the disc that swing check valves use. Lift check valves are more effective at leak prevention than swing check valves. Here’s a look at these two types of lift check valves:
• Piston – This type of check valve is also known as a plug check valve. It operates by controlling the flow of fluid in a piping system by means of the linear motion of a piston within the valve chamber. Sometimes the piston has a spring attached, which helps it stay in the closed position when not in use.
• Ball – The ball check valve operates simply using gravity. When there is enough pressure in the flow, the ball is lifted upward, and when the pressure is decreased, the ball rolls down and closes the opening. Ball Check Valves come in a wide range of material types and style types: PVC: Clear and Gray, CPVC: True Union and Compact.
Lift check valves are used in many industries for many applications. You will find them in residential and industrial settings. They are used in the food and beverage industry, oil and gas industry, and the marine industry, to name a few.
The butterfly check valve is unique in that its disc actually folds in the middle to allow the flow of liquid. When the flow is reversed, the two halves open back up to seal the valve closed. Also called a dual plate check valve or a folding disc check valve, this type of check valve is good for low-pressure liquid systems as well as gas piping systems.
Stop check valves allow you to start and stop the flow in your piping system. They are different in that they allow you to regulate the flow as well. Stop check valves are basically check valves that have an override control to stop flow regardless of flow direction or pressure. When the pressure is too low, stop check valves will close automatically to prevent backflow. This type of check valve may work using an external control rather than an override control, meaning you can set the valve to the closed position no matter what the flow is doing.
Stop check valves are most commonly used in boiler systems, power plants, petroleum production, and high-pressure safety applications.
When it comes to preventing backflow, there is no other option than check valves. Now that you have some information about the different types of check valves, you should be able to decide which one is best for your application.
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