Valve electric Actuators are mainly used in power plants or nuclear power plants, because a smooth, stable and slow process is required in high pressure water systems. The main advantages of electric Actuators are high stability and constant Thrust that can be applied by users. The thrust generated by a large actuator can be as high as 225000kgf. Only hydraulic actuator can achieve such a large thrust, but the cost of hydraulic actuators is higher than that of hydraulic actuators. Electric valve is much higher. The anti-deviation ability of the electric Actuator is very good and 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 it is equipped with a servo amplifier, it is easy to realize the exchange of positive and negative effects. And it is also possible to easily set the valve position state of the off signal( Hold/Full open/ Full close), and in the event of a fault, it must stay in the original position, which is Pneumatic actuators can not do it, and pneumatic actuators must be kept in place by means of a set of combined protection systems.

The main disadvantages of electric actuators are :

          Structure is more complex and it is easy prone to failure. Due to its complexity and technical requirements of field maintenance personnel are relatively higher; Motor operation to generate heat. If the adjustment is too frequent, will easy to cause motor overheating and generate thermal protection. It will increase the wear of the reduction gear; In addition, the operation is slow and it takes long time to output a signal from the regulator to the response of the control valve to move to the corresponding position which is not as good as pneumatic and hydraulic Actuators.

Pneumatic Valve

         Actuator and adjustment mechanism of the valve pneumatic actuator are unified whole, and the actuator has two types: Diaphragm type and Piston Type.Piston stroke is long suitable for occasions requiring large Thrust. Thin film stroke is small, can only directly drive the stem. Because the pneumatic actuator has the advantages of simple structure, large output thrust, stable and reliable action, safety and explosion-proof, it is widely used in power plants, chemical industry, oil refining and other production processes with high safety requirements.

The main disadvantages of Pneumatic actuators are:

With Continuous gas signal, output linear displacement, some with rocker Arm can output angular displacement. It has positive and negative functions.
Move fast, but slow down as the load increases. The output force is related to the operating pressure.
High reliability, but the valve can not be maintained after the interruption of air source ( It can be maintained after adding the position-preserving valve). It is inconvenient to realize segmented control and program control.
Simple maintenance,good adaptability to the environment. Large output power and explosion-proof function.