The Common Types of Check Valves

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Check valves are different from other types of valves in function, and they pass fluid in solely one direction. This sort of function is essential for a variety of safety applications, as well as for preventing overflow. Operating on a two-port system, check valves have an opening where fluid or gas is drawn into the first port. It is then regulated by a mechanism separating the two ports that allows water to be drawn from the first to the second port and drawn out from an opening without allowing fluids to reenter the first port.

Types of Check Valves

Ball Check Valve: This check valve uses a ball covering a round opening to separate the first and second ports. When fluid is drawn in, the ball is pushed forward. When the fluid is pushed back, the ball is pressed into the round opening, which creates a seal and allows all fluid to flow out from the second port in the intended direction. Ball check valves are mostly used to move liquids, since the ball mechanism is not the best for creating an airtight seal.

Swing Check Valve: As one of the most common types of valves, a swing check valve is used inside household toilet tanks, as well as in many other areas. Instead of a ball controlling flow, this valve uses a small door on hinges that opens when water is drawn in and closes when the flow of water is stopped, thereby not allowing any fluid to drain out of the valve’s entrance. 

Disc Check Valve: It's a more complex check valve that functions with a disc mounted on a spring. Pressure from the inlet opens the disc by stretching the spring. When the flow stops, the spring is compressed, and the disc returns to the closed position. Disc check valves usually cost less than other standard valves since they are usually smaller and lighter. They can be installed in any position, including vertical pipelines.

Dual Plate Check Valve: It also referred to as a split disc check valve that operates with a door that is split down the middle and only folds one way to regulate flow. When fluid enters the valve, the pressure causes the hinges of the door to open. When flow is stopped, the door is shut. Dual plate check valves are advantageous in applications that need large check valves, low pressure drops, lower operating pressures, or for applications that need check valves installed in any position, even vertical pipes.

Diaphragm Check Valve: A flexing rubber mechanism is used to regulate the flow of water on this check valve. It is activated when pressure on the upstream side is greater than that of the downstream side. When the pressure returns to a certain level, the rubber diaphragm flexes back into the closed position. An advantage of this type of check valve is the option to choose the pressure differential that controls the diaphragm for a variety of applications, but rubber and other materials used in a diaphragm check valve do not operate well at extreme temperatures.

Wafer Check Valve: This kind of valves can work with a swing, disc check, split or other mechanisms to regulate flow. The wafer check valve differs in its size that allows it to fit between a set of flanges.