Check Valve

A check valve allows the flow of the medium to pass through in only one direction. In most applications, the medium is a fluid, hydraulic fluid, or gas.

In spring-loaded check valves, there is a so-called closing element, which is closed by a spring. Meanwhile, the released fluid flows in the other direction of the closing element. This mechanism is triggered by pressing a ball, a flap, a diaphragm, or a cone into the corresponding seat. The respective sealing element is lifted from its seat, thereby opening the flow, when pressure in the flow direction exceeds the counterforce of the return spring.

Ball Check Valve

In a ball check valve, a ball acts as the closing element. The ball closes the valve by pressing it into a constriction. In many cases, the closing element is pressed into the valve’s constriction by gravity or by a spring. When the passage is closed, the medium can no longer flow through. If the medium flows against gravity from below or against the spring onto the ball, and the force exerted on the ball by the medium is greater than the spring’s force, the medium is released again and can flow through the valve. For this mechanism to function, such ball check valves must be hermetically sealed in the blocked direction.

Pilot-Operated Check Valve

This advanced version of a check valve can also be opened in the blocked flow direction with the help of a control signal. This allows the medium to flow through the valve in both directions. The major advantage over a conventional directional control valve is that the pilot-operated check valve is completely sealed in the blocked position. This allows loads, such as hydraulic cylinders, to be held on this side.

This valve is used in every hydraulic jack. In the jack, the pilot-operated check valve holds the applied load without the hydraulic system‘s piston dropping.

Partial Check Valve and Convection Barrier

In a partial check valve, a spring provides the necessary return force. The body that prevents flow is designed as a disc or flat plate. A bolt or pin is used to guide the check body. Simple applications of a partial check valve include bicycle valves or car tire valves.

A convection barrier is also known as a convection brake or gravity brake. These applications are merely a special form of the partial check valve. A convection barrier is used in a thermal solar system. There, it prevents unwanted free convection in the solar system and thus heat losses when there is no sunlight or in parts of the system that are shut down. Check valves are designed not to be completely sealed against the direction of flow. This allows for volume compensation during cooling and gas bubbles can pass through the valve.

Swing Check Valve of a Check Valve:

Simple, self-weight-controlled swing check valves are used for medium nominal diameters, liquid media, and pressure ratings up to 600 bar. They are manufactured with weld-on or flange ends from cast steel, cast iron, or forged steel.

Swing check valves are used, for example, at the connection of a house to the sewage system. This valve prevents sewage from entering the house’s wastewater pipes if the level of wastewater in the sewer rises extremely, for example, due to a cloudburst. Swing check valves are also used in the house, for example, in the heating flow to prevent hot water backflow.