Pneumatic actuator selection and composition!

1, the pneumatic device is mainly composed of cylinder, piston, gear shaft, end cover, seals, screws and so on; Complete sets of pneumatic devices should also include opening indication, travel limit, solenoid valve, positioner, pneumatic components, manual mechanism, signal feedback and other components.

2. The connection size of pneumatic device and valve shall comply with ISO5211 (bottom), GB/T12222 and GB/T12223.

3. The pneumatic device with manual mechanism should be able to open and close the pneumatic ball valve with its manual mechanism when the air source is interrupted. When facing the handwheel, the handwheel or handle should be rotated counterclockwise for the valve to open and clockwise for the valve to close.

4. When the end of the piston rod is internal and external thread, there should be a wrench mouth suitable for a standard wrench.

5, the piston seal ring should be easy to replace and repair.

6. Pneumatic device with buffer mechanism, the travel length of buffer mechanism can refer to the regulations.

7, with adjustable buffer mechanism pneumatic device, there should be external cylinder body to adjust its buffer mechanism.

8. The screw size of cylinder inlet and outlet shall conform to MANUR NORM (accessory standard) sypv, GB/T7306.1, GB/T7306.2 and GB/T7307.

Pneumatic actuator selection

Pneumatic actuator is an actuator that uses gas pressure to drive the opening and closing or regulating valves. It is also known as a pneumatic actuator or pneumatic device, but it is commonly known as a pneumatic head. Pneumatic actuators are sometimes equipped with certain auxiliary devices. Commonly used valve positioner and hand wheel mechanism. The role of the valve positioner is to improve the performance of the actuator by using the feedback principle, so that the actuator can be controlled by the controller signal, to achieve accurate positioning. The function of the handwheel mechanism is that when the control system is due to power failure, gas shutdown, no output of the controller or the actuator failure, it can be used to directly manipulate the control valve to maintain the normal production.

According to its energy form, the actuator is divided into three categories: pneumatic, electric and hydraulic. They have their own characteristics and are suitable for different occasions. Pneumatic actuator is a class of actuators. Pneumatic actuators can also be divided into single ACTING and DOUBLE ACTING types: the switching action of the actuator is driven by the air source, which is called double acting. The only switching action of SPRING RETURN is the on action, which is air driven, and the off action, which is spring returned.

Ball valves are basically based on a polished ball core (including channels) sandwiched between two seats (upstream and downstream). The rotation of the ball center intercepts or flows through the ball core. The pressure difference between the upstream and downstream forces the ball core against the downstream seat (floating ball structure). The torque to operate the valve in this case is determined by the friction between the ball core and the seat and the stem and the packing. The maximum torque occurs when there is a differential pressure and the ball core rotates in the closed position towards the open direction.

Butterfly valve. The structure of the butterfly valve is basically based on the butterfly plate fixed in the axis. The disc is fully sealed with the seat in the closed position, and the valve is in the fully open position when the disc is rotated (around the stem) parallel to the flow of the fluid. Conversely, when the disc is perpendicular to the flow direction, the valve is in the closed position. The torque to operate the butterfly valve is determined by the friction between the butterfly plate and the seat, the stem and the packing. At the same time, the force of the pressure difference acting on the butterfly plate also affects the operating torque, such as the maximum torque when the valve is closed, and the torque will be significantly reduced after a small rotation.

The type and structure of the pneumatic actuator are roughly the same, mainly the actuator is different. Therefore, when the pneumatic actuator is introduced, it is divided into two parts: actuator and regulating valve. The pneumatic actuator consists of two parts: the actuator and the regulating valve (regulating mechanism). According to the size of the control signal, the corresponding thrust is generated to promote the operation of the regulating valve. The regulating valve is the regulating part of the pneumatic actuator. Under the action of the actuator thrust, the regulating valve produces a certain displacement or Angle, which directly regulates the flow of fluid.