Detailed explanation of the working principle and switching action of butterfly valve

1. Basic structure of butterfly valve
The butterfly valve is mainly composed of valve body, butterfly plate, valve stem, sealing pair, operating mechanism and other components. The valve body is the main part of the butterfly valve, usually cylindrical, with a fluid channel inside; the butterfly plate is the key component to control the on and off of the fluid, it is disc-shaped and can rotate around its own axis; the valve stem connects the butterfly plate and the operating mechanism, responsible for transmitting the rotational torque; the sealing pair includes the sealing surface on the valve seat and the butterfly plate to ensure the sealing performance when the valve is closed; the operating mechanism can be a manual device, an electric device, a pneumatic device, etc. according to actual needs, which is used to drive the rotation of the valve stem.

2. The switching action principle of butterfly valve
The switching action of the butterfly valve is mainly completed by the valve stem driving the butterfly plate. This process reflects the high efficiency and precision of mechanical transmission.

Opening process:

When the butterfly valve needs to be opened, the operating mechanism receives the command and starts working. For manual devices, the operator directly rotates the handle; for electric or pneumatic devices, the rotational power is generated by the motor or pneumatic actuator.
The rotational power is transmitted to the butterfly plate through the valve stem, driving the butterfly plate to rotate around its axis. As the butterfly plate rotates, the part that was originally close to the valve seat sealing surface gradually separates, forming a gradually increasing flow channel.
In this process, the medium begins to converge from both sides of the valve to the center, and then flows smoothly through the gap between the butterfly plate and the valve body. As the rotation angle of the butterfly plate increases, the flow area of ​​the medium gradually expands, and the flow resistance decreases accordingly.
When the butterfly plate rotates to 90° (or close to 90°, depending on the design), the butterfly valve reaches a fully open state. At this time, the butterfly plate is almost parallel to the fluid channel, the medium flow area reaches the maximum, the flow resistance is minimized, and efficient fluid transmission is achieved.
Closing process:

The process of closing the butterfly valve is opposite to opening. The operating mechanism rotates the valve stem in the opposite direction, and the valve stem drives the butterfly plate to rotate counterclockwise (or clockwise, depending on the installation method).
The butterfly plate gradually approaches the valve seat sealing surface. As the rotation angle decreases, the medium flow area gradually decreases and the flow resistance increases.
When the butterfly plate is completely in contact with the valve seat sealing surface, the butterfly valve is closed and the fluid is effectively cut off. At this time, the close fit of the sealing pair ensures the sealing performance of the valve and prevents the leakage of the medium.
3. Performance characteristics of butterfly valves
The reason why butterfly valves stand out among many valve types is due to their unique performance characteristics:

Compact structure and light weight: The butterfly valve is relatively small in size and easy to install and maintain.
Low fluid resistance: In the fully open state, the butterfly plate hardly hinders the flow of fluid and has a low flow resistance coefficient.
Fast opening and closing: The butterfly valve opens and closes quickly and is suitable for occasions that require frequent operation.
Good adjustment performance: By adjusting the rotation angle of the butterfly plate, the flow and pressure of the medium can be controlled.
Reliable sealing performance: High-quality sealing materials are used to ensure the sealing of the valve under various working conditions.