Check valve

A non-return valve is a component which permits the flow of a fluid (liquid, gas ) in only one direction.

General

With spring-loaded check valves, the closing element in one direction will be closed by the spring is released from the fluid flowing in the other direction, however. Here, either a ball, a cone, a door or a diaphragm is pressed into the respective seat. Is in the forward direction at a pressure which can overcome the force of the return spring, the sealing element is lifted from the seat and the flow is free.

There are also embodiments without a spring which close only through the flowing fluid and the weight of the sealing element.

Designs

Check valves

• Simple, with two straight olives, all glass in the lab using
• Friedrichs - Antlinger of glass, with replaceable valve disc made of plastic
• Check valve installed in the water jet pump

Ball check valve

The ball check valve comprises a restriction which is closed by a ball. The ball is urged by gravity or by a spring to the narrowing and closing the passage. The medium can not flow through. Such valves are hermetically sealed in the closed direction in general.

When the medium opposite to the force of gravity or the spring presses from above onto the ball and the ball outweighs the power of the medium, the force of the spring, the medium can flow through the valve.

Check valve, pilot operated

This is an advanced version. The valve can be opened by a control signal also in the locked direction and flows through it. The difference / advantage as opposed to a directional control valve is that the valve is in the "locked position" is absolutely sealed and thus loads may be held as eg cylinder. Among the most common applications include the hydraulic jack. The check valve keeps the load safely without the piston slides down.

Plate check valve

A plate check valve consists of a with a spring as a restoring force -providing institution, provided check valve. The return element is in the form of a flat plate or a plate. To guide a bolt or pin is being used. An example of the application of the non-return valve is a bicycle valve or the valve in the tires.

Convection, convection, gravity brake

For solar thermal systems there is a special form of plate check valve, the convection, convection or gravity brake is called, since they in the absence of sunlight, prevents the convection within the solar system and thus a loss of energy. These check valves are usually designed so that they are not completely tight against the flow direction to allow a volume control on cooling and a passing of gas bubbles.

Non-return valve

For liquid media, average nominal sizes (about 80-600 mm) and all pressure levels (up to 600 bar) simple, self- weight-controlled check valves are often used. They are manufactured with flanged or welding ends and are usually made ​​of cast iron, cast steel or forged steel.

The check valve is provided at the connection of a house to the sewer system to prevent dirt ingress of water into the domestic waste water pipes, if the waste water level in the channel increases excessively (eg when a cloudburst ). Swing check valves are installed in the heating flow and in the hot water circulation pipe behind the pump to prevent backflow of hot water.

Applications

• In the suction strainer to prevent a fire department pump check valve that the hose runs empty.
• Watch studs with drop jacket hydrant
• Double check valves in hydraulic linear drives
• Tire valve on vehicle tires
• Venous valves effect the proper flow direction of the blood circulation.