Pneumatic actuators are actuators that use air pressure to drive open, close or adjust valves, also known as pneumatic actuators or pneumatic devices, but they are generally called pneumatic heads. Pneumatic actuators are sometimes equipped with certain auxiliary devices. Commonly used are valve positioners and handwheel mechanisms. The function of the valve positioner is to use the feedback principle to improve the performance of the actuator, so that the actuator can achieve accurate positioning according to the control signal of the controller. The function of the handwheel mechanism is to use it to directly control the control valve to maintain normal production when the control system is powered off, gas out, the controller has no output or the actuator fails.

　　The type and structure of the adjustment mechanism of the pneumatic actuator are roughly the same, mainly because the actuator is different. Therefore, when the pneumatic actuator is introduced, it is divided into two parts: the actuator and the regulating valve. Pneumatic actuator consists of two parts: actuator and regulating valve (regulating mechanism). According to the size of the control signal, the corresponding thrust is generated to push the regulating valve to act. The regulating valve is the regulating part of the pneumatic actuator. Under the action of the thrust of the actuator, the regulating valve produces a certain displacement or rotation angle to directly regulate the flow of the fluid.