Working principle of pneumatic butterfly valve

The pneumatic butterfly valve is composed of the pneumatic actuator and the butterfly valve. Because of the characteristics of the butterfly valve itself, such as light weight, simple structure, easy operation, etc., it is often installed on the large-diameter low-pressure pipeline. Pneumatic butterfly valves can be divided into single acting pneumatic butterfly valves and double acting pneumatic butterfly valves. This article introduces the working principle of pneumatic butterfly valves according to single acting and double acting.

Pneumatic butterfly valve through the compressed air as the power source, drive the valve stem to control the disc disc rotation around the axis, the initial position of the valve according to the actual needs, when the initial position of the valve rotates 90 degrees, it is the end of an action (from open to close, or from close to open), and vice versa for another action (from close to open, or from open to close).

The execution speed of the pneumatic butterfly valve is relatively fast, and it is not easy to be damaged by jamming during the action process, and it does not require workers to do it themselves, which can not only be used as a cut-off valve, but also be equipped with a valve positioner to adjust and control the pipeline medium. The pneumatic butterfly valve actuator is divided into single action and double action forms, and the double action is ventilation open and ventilation close. Among them, the single-acting actuator has the function of spring return, which can be automatically closed or opened in the case of gas and power failure, and the safety factor is high.

Single acting pneumatic butterfly valve working principle:

The gas signal pressure output of the single effect positioner of the single acting pneumatic butterfly valve is input into the air chamber on the spring-free side of the pneumatic actuator, because the gas signal pressure effect on the piston moves in a straight line when there is a difference between the thrust and the spring force. Through the gear and rack transmission, the thrust formed by the pressure of the gas signal is balanced with the spring force, and the movement stops.

In addition, when the spindle of the actuator rotates, the valve stem and spool are driven to rotate, and then the flow area between the spool and the seat is changed to achieve the adjustment intention.

Working principle of double acting pneumatic butterfly valve:

The double acting pneumatic butterfly valve has two air chambers, and the air source signal pressure output by the double effect positioner is separated from the left and right two air chambers of the input actuator piston. Because the pressure of the air source input to the two chambers is different, there is a pressure difference between the two chambers, and then the piston is pushed to move in a straight line. Through the gear and rack drive, the linear movement of the piston is converted into the rotating movement of the main shaft of the actuator. When the pressure of the left and right air chambers is balanced, the movement stops. If the flow rate needs to be adjusted, it is necessary to drive the valve stem and spool to rotate while the actuator is rotating to change the flow area between the spool and the seat to achieve the adjustment intention.