What is the difference between double-acting and single-acting pneumatic butterfly valve actuators?

Pneumatic butterfly valve consists of pneumatic actuator and butterfly valve. Because Weidun VTON butterfly valve has the characteristics of light weight, simple structure, fast response, high cost performance and convenient operation, it is often installed and used in large-diameter low-pressure pipelines. Pneumatic butterfly valves can be divided into double-acting pneumatic butterfly valves and single-acting pneumatic butterfly valves according to pneumatic actuators. Since the actuator of butterfly valve can distinguish between single action and double action, that is his characteristic and difference. Knowing their characteristics helps to choose the right products. This paper mainly introduces the difference between double-acting pneumatic butterfly valve and single-acting pneumatic butterfly valve.

Weidun VTON double-acting butterfly valve has left and right air chambers, and the air signal pressure output by the pneumatic butterfly valve double-acting positioner is respectively input into the left and right air chambers of the actuator piston. Because of the different air pressures in the air chambers on both sides of the input, a pressure difference will be formed between the two air chambers, thus pushing the piston to move linearly. Through the rack and pinion transmission, the linear motion of the piston is converted into the rotary motion of the main shaft of the actuator, and the motion stops when the pressure of the left and right air chambers is balanced. If it is necessary to adjust the flow, it is necessary to drive the valve stem, the valve core and the actuator to rotate at the same time, and change the flow area between the valve core and the valve seat to achieve the purpose of adjustment.

Working principle of imported single-acting pneumatic butterfly valve;

The air signal pressure output by the single-acting positioner of the Witton VTON single-acting butterfly valve is input to the air chamber on the spring-free side of the pneumatic actuator. Because the air signal pressure on the piston is different between the thrust and the spring force, the cylinder piston will move linearly. Through the rack and pinion transmission, the thrust formed by the air signal pressure is balanced with the spring force, and the movement stops. In addition, the spindle of the actuator drives the valve stem and the valve core to rotate at the same time, thus changing the flow area between the valve core and the valve seat and achieving the purpose of adjustment.

What is the difference between single function and double function of pneumatic butterfly valve? How to choose the type?

Simply put, the opening and closing actions of double-acting cylinders are all driven by air source; Turn on ventilation, turn off ventilation, stop breathing and stay in place; ? Only the opening or closing action of single-acting cylinder is driven by air source, and the corresponding closing action or opening action is used as spring reset; Therefore, single-acting butterfly valves can be divided into normally open type (ventilation closed, gas cutting open) and normally closed type (ventilation open, gas cutting closed).

The stroke of single-acting cylinder and double-acting cylinder is the same, which is mainly selected according to the specific requirements of users. Single action is generally used in the case of power failure and gas failure, and the valve needs to be opened or closed. Single acting cylinders are more expensive. Engineers of Weidun VTON will confirm the parameters before the user selects the type to see whether the imported pneumatic butterfly valve is single-acting or double-acting. Generally, Weidun VTON chooses a double-acting pneumatic butterfly valve when the customer does not specify it.