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Actuator, also called final controlling element, is a device used for receiving control information and applied in the controlled object of pneumatic actuators. Actuator control system also is an instrument to control the variables of changes in the system. An actuator consists of the executing agency and the adjustment mechanism. In recent years, pneumatic actuators application is in fall. How these phenomenons appear?
In the process of actuator control system, an actuator consists of two parties, actuators and regulating mechanism. Regulating mechanism changes the parameters of the production process directly through the implementation of components. As a result, it can make the production process to meet the requirement. Another part, the actuator receives control information from the controller and then it will convert it to output of the adjusting mechanism (such as angular displacement or linear displacement output). It uses the proper implementation of components as well, but the requirement is different from the regulatory agencies.
According to the driving energy, actuator can be divided into three kinds, the pneumatic actuator, the electric actuator and the hydraulic one. Next is going to mainly introduce the pneumatic one and the electric one.
Pneumatic actuator is a kind of machine which is known as pneumatic devices, but the most popular name is pneumatic head. Pneumatic actuator and regulatory agencies are a unified whole and there is several types of the regulatory agencies, such as thin film type, piston type, fork type and gear rack type. The stroke of piston type is long so that this type is suitable for a greater thrust required. While the stroke of thin film type is short and it only can directly drive the valve stem. Big torque, small place and torque curve is more proper for the torque curve of the valve all these are the features of a fork type pneumatic actuator. It doesn’t look beautiful that is the only shortage of this type. Therefore, a fork type pneumatic actuator is usually used on the big torque valve. Gear rack type has a simple structure. Stable and reliable operation and safety explosion-proof are the biggest advantage of it. So, this type is widely applied in power plants, chemical factory, refining, etc. some similar industries.
The basic types of electric actuators are rotary part (Part-Turn), multi-turn and linear three driving modes. The basic drive actuator of the valve is used to drive to the fully open or close position. The electric actuator which is used in control valve can make the valve walk to any location precisely. Since more and more factories adopt automatic control in their production, manual operations were replaced by mechanical or automation equipments. People not only require that the executive agencies can play a role as an interface between the actuator control system and the mechanical movement, but also require that the executive agencies can enhance the safety performance and environmental protection performance during the production. In this case, the electric actuator arises at the historic moment. Compared with other types of actuators, like pneumatic actuators, electric actuators have light weight and with compact structure and complete functions such advantages. As for this reason, pneumatic actuators applications are in fall. People nowadays prefer to choose electric actuators rather than pneumatic ones.