The actuator is an indispensable part of the industrial process control automatic regulation system. The actuator used depends entirely on the valve, and the actuator is only the drive.
The actuators configured by the regulating valve are nothing more than the pneumatic actuator, the electric actuator, and the hydraulic actuator (electro-hydraulic actuator). Accordingly, the regulating valve is also divided into an electric regulating valve, a pneumatic regulating valve, and a hydraulic actuator. Regulating valve. Its performance has its own advantages and disadvantages.
Advantages of pneumatic actuators:
Most of the actuators used in the chemical industry today are pneumatic actuators that use air sources for power. Pneumatic actuators are easier to operate and calibrate than other types of actuators, and interchangeable front and back can be easily implemented on site. Its greatest advantage is its safety and explosion-proof function. When using the positioner, it is ideal for flammable and explosive environments. If the electric signal is not explosion-proof or intrinsically safe, there is a potential risk of fire caused by fire. . In comparison, it is more economical than electric and hydraulic, and its structure is simple, easy to grasp and maintain.
The main disadvantages of pneumatic actuators are:
That is: the response is slow, the control accuracy is low, and the anti-deviation ability is poor. The pneumatic actuator is the best choice in the condition that does not require high control precision, extremely fast response and anti-deviation capability.
Pneumatic actuators, ie “cylinders”, are single-acting and double-acting, double-acting cylinders, which cannot return to the preset position after the gas source is shut off. Single-acting pneumatic actuators can be returned to a preset position by means of a spring after breaking the air supply.
Advantages of electric actuators:
The electric actuator is a drive that controls the linear or angular motion of the valve body. AC or DC power is used as the driving energy source, and the control signal of the industrial automation control system is accepted to control the opening of the valve. Electric actuators, instead of manual operations, increase the efficiency and reliability of industrial automation production. Save a lot of labor costs and operating costs, saving trouble and convenience. Electric actuators have higher control accuracy than pneumatic actuators. If a servo amplifier is used, the interchange of positive and negative effects can be easily realized, and the status of the off-signal valve position can be easily set (hold/fully open/closed).
Disadvantages of electric actuators:
Mainly: the structure is more complicated, it is more prone to failure, and due to its complexity, the technical requirements for on-site maintenance personnel are relatively higher; the motor runs to generate heat, if the adjustment is too frequent, it is easy to cause the motor to overheat and generate heat. Protection, at the same time, will increase the wear on the reduction gear; in addition, it will run slower, it will take a longer time to output a signal from the regulator and move to the corresponding position in response to the valve response. This is not as pneumatic as it is. The place of the hydraulic actuator.
Advantages of hydraulic actuators:
The ability to resist deviation is very good, which is not possible with electric actuators. The output thrust or torque is basically constant, which can well overcome the imbalance force of the medium and achieve accurate control of the process parameters. The maximum actuator can generate up to 225,000 kgf of thrust, and only liquid actuators can achieve such a large thrust, but hydraulic actuators are much more expensive than electric. It is ideal for remote areas where air supply pressure is not available but precise control of the spool position is required.
Different valves use different drive devices, and the appropriate drive should be selected according to the type of valve.

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