Structural features of the butterfly check valve
The butterfly check valve 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. Very few. This type of valve should generally be installed horizontally in the pipeline.
The check valve can be divided according to its structure and installation method:
1. The valve flap of the butterfly check valve has a disc shape and rotates around the shaft of the valve seat passage. Because the valve passage is streamlined, the flow resistance is smaller than that of the butterfly check valve, which is suitable for low flow rate and flow. Frequently changing large diameter applications, but not suitable for pulsating flow, the sealing performance is not as good as lifting. The butterfly check valve is divided into three types: single-valve, double-valve and multi-valve. These three forms are mainly divided according to the valve diameter. The purpose is to prevent the hydraulic shock from being weakened when the medium stops flowing or reverses.
Second, the butterfly check valve: according to the valve operating form is divided into two types: 1, the valve flap sliding valve along the vertical centerline of the valve body, the butterfly check valve can only be installed on the horizontal pipe, at high pressure The upper flap of the small-diameter check valve can be a ball. The butterfly check valve has the same valve body shape as the shut-off valve (common to the shut-off valve), so its fluid resistance coefficient is large. Its structure is similar to the stop valve, the valve body and the valve flap are the same as the shut-off valve. The upper part of the valve flap and the lower part of the valve cover are machined with a guide sleeve, and the valve guide can be easily lifted and lowered in the valve guide guide. When the medium is downstream, the valve flap is opened by the medium thrust. When the medium stops flowing, the valve flap is self-retained. The drooping falls on the valve seat to prevent the medium from flowing back. The direction of the inlet and outlet passages of the straight-through butterfly check valve is perpendicular to the direction of the valve seat passage; the vertical lift check valve has the same direction of the medium inlet and outlet passages as the valve seat passage, and its flow resistance is smaller than that of the straight-through type; A check valve that rotates around the pin in the valve seat. The butterfly check valve has a simple structure and can only be installed on a horizontal pipe with poor sealing performance.
Third, the pipeline type check valve: the valve sliding along the center line of the valve body. Pipeline check valve is a new type of valve. It is small in size, light in weight and good in processability. It is one of the development directions of check valves. However, the fluid resistance coefficient is slightly larger than the swing check valve.
4. Press-type check valve: This valve is used as a boiler feed water and steam shut-off valve. It has a comprehensive function of a lift check valve and a shut-off valve or an angle valve.
In addition, there are some check valves that are not suitable for pump outlet installation, such as bottom valves, spring type, Y type and other check valves.
Five, use and performance specifications:
This valve is used on industrial piping as a means of preventing backflow of the medium.