Views: 264 Author: Site Editor Publish Time: 2021-05-26 Origin: Site
The automatic adjustment system of the industrial production process generally consists of detectors, regulators, actuators and adjustment objects. Among them, the actuator is always indispensable, and is generally composed of an actuator and a regulating mechanism (generally called a regulating valve). In addition, accessories such as valve positioners and handwheel mechanisms can also be fitted as required.
According to its energy form, actuators can be divided into three categories: pneumatic, hydraulic and electric. Pneumatic actuators use compressed air as energy source. Its characteristics are simple structure, reliable action, stable operation, large output thrust, convenient maintenance, fire and explosion prevention, and low price. Therefore, the air powered actuator is widely used in the production process of chemical industry, papermaking, oil refining, etc. It can be conveniently used with passive instruments. Even when using electric instruments or computer control, as long as the electric signal is converted into a standard air pressure signal of 20-100kPa by an electric converter or electric valve positioner, pneumatic actuators can still be used. The electric motor actuator has easy access to energy and rapid signal transmission, but its structure is complex and its explosion-proof performance is poor. The hydraulic actuator is basically not used in the production process of chemical industry, oil refining, etc. It is characterized by a large output thrust.
An electric actuator is a driving device that can provide linear or rotary motion. It uses a certain driving energy and works under a certain control signal. According to the driving method, the basic types are part turn actuator, multi turn actuator and electric linear actuator.
The electric cylinder actuator plays a very important role in modern production process automation, and is often referred to as the hand and foot that realizes the automation of the production process. Electric actuators use electric energy as power and receive standard signals (analog or digital) from the regulator. By changing this signal into the corresponding mechanical displacement (angle, straight or multi-turn) to automatically change the operating variables (regulating valve, dampers, baffle opening, etc.) to achieve the adjustment of the parameters (temperature, pressure, flow, liquid level, etc.) for the purpose of automatic adjustment, the production process is carried out as scheduled. Therefore, the high speed electric actuator has a great influence on the safe operation, reliability and adjustment quality of the automatic adjustment system.
The main advantages of electric actuators are high stability and constant thrust that users can apply. The thrust generated by the largest actuator can be as high as 225000kgf. Only hydraulic actuators can achieve such a large thrust, but the cost of hydraulic actuators is much higher than that of fast electric actuators.
The anti-deflection ability of explosion proof electric actuator is very good. The output thrust or torque is basically constant, which can well overcome the unbalanced force of the medium and achieve accurate control of the process parameters, so the control accuracy is higher than that of the pneumatic actuator. If equipped with a servo amplifier, the positive and negative effects can be exchanged easily, and the signal-off valve position state (hold/full open/full close) can be easily set. When it fails, it must stay in place, which is impossible for a pneumatic actuator. The compact pneumatic actuator must rely on a set of combined protection system to achieve position retention.
