Author:Site Editor Publish Time: 2019-01-18 Origin:Site
Check valve is a valve in which the opening and closing member is a circular valve flap and acts on its own weight and medium pressure to block the reverse flow of the medium. It is an automatic valve, also known as a check valve, non return valve or isolation valve.
l What Is Check valve definition?
l The Function and Characteristics of Check Valve
The flap motion mode is divided into lift type and swing type. The lift check valve is similar in construction to the shut-off valve and lacks only the valve stem that drives the flap. The medium flows in from the inlet end (lower side) and flows out from the outlet end (upper side). When the inlet pressure is greater than the sum of the valve disc weight and its flow resistance, the valve is opened. Conversely, the valve closes when the media is reversed. The swing check valve has a valve flap that is inclined and rotatable about the shaft, and operates in a similar manner to the lift check valve. Check valves are often used as bottom valves for pumping devices to prevent back flow of water. The combination of the globe valve and the shut-off valve provides a safe isolation.
The check valve can also be used to supply a line in which the pressure may rise to an auxiliary system that exceeds the system pressure. The check valve can be mainly divided into a swing type check valve (rotation according to the center of gravity) and a lift check valve (moving along the axis).
The function of this type of valve is to allow only the medium to flow in one direction and to prevent flow in the opposite direction. Usually, the valve is automatically operated, and the valve flap is opened by the fluid pressure flowing in one direction; when the fluid flows in the opposite direction, the fluid pressure and the self-reclosing valve flap of the valve disc act on the valve seat to cut off the flow.Among them, the check valve belongs to this type of valve, which includes a swing check valve and a lift check valve. The swing check valve has a hinge mechanism and a door-like flap that rests freely against the inclined seat surface. In order to ensure that the valve flap can reach the proper position of the valve seat surface each time, the valve flap is designed in the hinge mechanism, so that the valve flap has enough swinging space and the valve flap is truly and comprehensively in contact with the valve seat.
The discs can all be made of metal, or they can be inlaid with leather, rubber, or synthetic coverings depending on the performance requirements. In the fully open condition of the swing check valve, the fluid pressure is almost unimpeded, so the pressure drop across the valve is relatively small. The valve flap of the lift check valve is located on the valve seat sealing surface of the valve body. In addition to the valve flap being free to lift and lower, the valve is like a shut-off valve. The fluid pressure causes the valve flap to lift from the valve seat sealing surface. The return of the medium causes the valve flap to fall back to the valve seat and shut off the flow. Depending on the conditions of use, the flap may be of an all-metal construction or may be in the form of a rubber or rubber ring on the valve disc holder. Like the shut-off valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow rate of the swing check valve is limited.
Check valve is a kind of valve that automatically opens and closes by the force of medium itself.
Check valves are mainly used to prevent backflow of media. Once the water flows backwards, the
check valve closes. Check valves are generally divided into lifting check valves and swing check valves.
Lift Check Valve (Globe Check Valve): The disc of lift Check Valve generally moves along the vertical center line of the check valve body. Lifting check valves can be divided into horizontal and vertical models. The lift check valve is composed of body, bonnet, stem, seat and spool.
Swing check valve (pivotal check valve): The disc of swing check valve generally revolves around the pin outside the seat. Swing check valves can be divided into single-valve, double-valve and multi-valve. The pivotal check valve is composed of a body, a cover, a rotating shaft and a flapping plate.
The working principle of the check valve is to start and close according to the pressure change of the mink fluid itself to prevent the medium from flowing back. It is mostly used in water supply pipelines.
The suction bottom valve is a kind of check valve. Lifting suction bottom valve has good sealing performance and low noise. It is generally used in horizontal pipelines with nominal diameter less than 200 mm. Swing suction bottom valves are usually used in vertical or large diameter pipelines because of their poor sealing and high noise. The suction bottom valve is installed at the end of the suction pipe of the pump, and is connected with the pipeline by inner ribs or flanges.
The disc of disc check valve revolves around the pin axis in the seat. Its structure is simple and its sealing is poor. It can only be installed in horizontal pipeline.
The disc of the pipeline check valve slides along the center line of the valve body. The volume and quality of the pipeline check valve are small.
The disc of the lift check valve slides along the center line of the valve body and can only be installed in the horizontal pipeline with a larger fluid resistance coefficient.
The disc of the swing check valve revolves around the pin outside the seat.
Check valve refers to the valve that automatically opens and closes the disc depending on the flow of the medium itself to prevent medium backflow, also known as check valve, one-way valve, counterflow valve, and back pressure valve. Check valve is an automatic valve. Its main function is to prevent medium backflow, reverse pump and drive motor, and release of container medium.
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