What is the working principle of the plastic pneumatic butterfly valve?

Plastic butterfly valves originated in the United States in the 1930s, and were only widely used in Japan in the 1960s. In the 1970s, my country began to use plastic butterfly valves. With the passage of time, a plastic pneumatic butterfly valve appeared on the market , and this plastic pneumatic butterfly valve has now been used in the market. So what is the working principle of this plastic pneumatic butterfly valve ?

        In fact , the opening degree of the plastic pneumatic butterfly valve is closely related to the total flow. There is usually a linear proportional change between the opening degree of the plastic pneumatic butterfly valve and the total flow. If it is used to control flow, its flow characteristics will be closely related to the flow resistance of the pipe. For example, the specifications and structure of the two pipelines are the same, but the pipeline loss coefficient is different, and the total flow rate of the valve will also be very different. . If the valve is in a condition with a relatively large throttle range, the reverse side of the valve plate is likely to cause cavitation, which may damage the valve, and it is usually used outside 15°.

         When the plastic pneumatic butterfly valve is in the middle opening, the shape of the opening in front of the valve body and the butterfly plate is centered on the valve shaft, and the two sides are different. The butterfly plate on one side moves in the direction of flow, and the other side moves in the direction of counterflow. Therefore, a nozzle-shaped opening is formed on one side of the body and the valve plate and the other side of the valve body plate, and a nozzle-shaped opening similar to a hole-shaped opening is formed on the other side and the other side is formed with a hole-shaped opening. . The flow rate on the nozzle side is much larger than the flow rate on the throttle side, and the valve under the throttle side will generate negative pressure, and the sealant will easily fall off.

         Plastic pneumatic butterfly valves and butterfly rods have no self-locking ability. In order to locate the butterfly plate, the worm gear reducer should be installed on the valve rod. The use of worm gear reducer can not only make the butterfly plate have a self-locking function, and make it stop at any position, but also can improve the working performance of the valve.

The operating torque of the          plastic pneumatic butterfly valve has different values ​​due to the degree of valve opening and the direction of opening and closing. For horizontal butterfly valves, especially large-diameter butterfly valves, the difference between the valve shaft and the water head and the difference between the valve shaft and the water head cannot be ignored due to the water depth.