How to select the pneumatic actuator
Today, Wuxi Xinming automatic control valve industry co., ltd. will give you a detailed introduction of howPneumatic actuatorSelection:
Pneumatic actuatorIt is an actuator that uses air pressure to drive the opening and closing or regulating valves. It is also called a pneumatic actuator or a pneumatic device, but it is generally called a pneumatic head. Pneumatic actuators are sometimes equipped with certain auxiliary devices. Commonly used valve positioner and handwheel organization. The effect of the valve positioner is to use the reaction principle to improve the performance of the actuator, so that the actuator can be controlled by the controller signal to complete the accurate positioning. The effect of the handwheel organization is that when the control system is due to power failure, gas failure, no output of the controller or failure of the execution organization, it can be used to directly control the control valve to maintain the normal production.
Actuators are divided into three categories according to their energy sources: pneumatic, electric and hydraulic. They have their own characteristics and are suitable for different occasions. Pneumatic actuators are a category of actuators. Pneumatic actuators can also be divided into two types: single effect and double effect: the switching action of the actuator is driven by the air source, which is called DOUBLE ACTING (double effect). The switch action of SPRING RETURN (single effect) is driven by air source as long as the on action is opened, and the spring is reset when the off action is closed.
The structural principle of the ball valve is basically based on a polished ball core (including the channel) sandwiched between the two valve seats (upstream and downstream). The rotation of the ball core intercepts or flows through the ball core. The force generated by the pressure difference between the upstream and downstream makes the ball core close to the downstream valve seat (floating ball structure). In this case, the torque to operate the valve is determined by the conflict between the ball core and the valve seat, the valve stem and the packing. As shown in Figure 1, the upper limit of the torque value occurs when a pressure difference occurs and the ball core rotates in the opening direction in the closed position.
Butterfly valve. The structural principle of the butterfly valve is basically based on the butterfly plate fixed on the axis. In the closed position, the butterfly plate is completely sealed with the valve seat. When the butterfly plate rotates (around the valve stem) parallel to the flow direction of the fluid, the valve is in the fully open position. On the contrary, when the butterfly plate is perpendicular to the flow direction of the fluid, the valve is in the closed position. Butterfly valve operation torque is by the butterfly plate and valve seat, valve stem and packing between the resolution of the friction, together with the pressure difference effect on the butterfly plate force also affects the operating torque such as the valve in the closed torque reaches the upper limit, small rotation, torque will be significantly reduced.
The structural principle of the plug valve is basically based on the plug sealed in the conical plug body. There is a channel in one direction of the plug. Follow the plug screw into the seat to complete the opening and closing of the valve. The operating torque is generally not affected by the pressure of the fluid but is determined by the conflict between the valve seat and the plug during opening and closing. When the valve is closed, the torque reaches the upper limit. Because of the influence of pressure, the torque is always kept high for the rest of the operation.
The above is the detailed information on how to select pneumatic actuators, which is introduced by Wuxi Xinming automatic control valve industry co., ltd. if you have any questions, please feel free to come and consult!