Electric Valves
The valve electric actuator is mainly used in the power plant or the nuclear power plant, because a smooth, stable and slow process is required in the high-pressure water system. The main advantage of the electric actuator is the high stability and the constant thrust that the user can apply. The thrust generated by the maximum actuator can be up to 225,000 kgf. Only the liquid actuator can achieve such a large thrust, but the cost of the liquid actuator is much higher than that of the electric actuator. The deviation resistance of the electric actuator is very good, and the output thrust or torque is basically constant, which can overcome the unbalanced force of the medium and achieve the accurate control of the process parameters, so the control accuracy is higher than that of the pneumatic actuator. If the servo amplifier is used, it can easily realize the exchange of positive and reverse effects, or the broken signal valve position state can be easily set (maintain / fully open / close). When the fault occurs, it must stay in the original position, which is not done by the pneumatic actuator, and the pneumatic actuator must use a set of combined protection system to achieve position protection.

Disadvantages of the Electric Actuators
The structure is more complex and more prone to failure, and due to its complexity, the technical requirements for the field maintenance personnel are relatively higher; the motor runs to generate heat, if too frequently, easy to cause the motor to overheat, thermal protection, and also increase the wear of the reduction gear; and output a signal from the regulator in response to the corresponding position, which is inferior to the pneumatic and hydraulic actuator.

Pneumatic Valves
The actuator and regulating mechanism of the valve pneumatic actuator are a unified whole, and the actuator has thin film type and piston type. The piston type stroke is long, suitable for large thrust is required; and the film type stroke is small, can only directly drive the valve stem. Because the pneumatic actuator has the advantages of simple structure, large output thrust, smooth and reliable action, and safe and explosion-proof, it is widely used in power plants, chemical industry, oil refining and other production processes with high safety requirements.
Main advantages of the pneumatic actuator:

Accept continuous gas signal, output linear displacement (after the power / gas conversion device, can also accept continuous electrical signal), some with a rocker arm, can output angular displacement.

Has both positive and negative functions.

The movement speed is large, but the speed is slow when the load increases.

The output force is related to the operating pressure with high reliability, but the valve cannot be maintained after the gas source is interrupted (it can be maintained after adding the position valve).

Inconvenient to achieve segment control and program control.

Simple maintenance, good adaptability to the environment.

The output power is relatively large.

It has the explosion-proof function.