The pneumatic control valve is powered by compressed air and equipped with pneumatic actuator, while the electric control valve is composed of electric actuator and control valve. It is not difficult to see that there are differences in the selection of actuators of pneumatic control valve and electric control valve. The following pneumatic control valve and electric control valve in power, use, maintenance and other aspects of comparison.

Pneumatic control valve:

The actuator and regulating mechanism of the valve pneumatic actuator are a unified whole, and there are two types of actuators: pneumatic diaphragm type and pneumatic piston type. The piston type has a long stroke, which is suitable for the occasion requiring a large thrust; while the pneumatic membrane type has a small stroke, which can only directly drive the valve rod. Because the pneumatic actuator has the advantages of simple structure, large output thrust, stable and reliable action, and safety and explosion-proof, the pneumatic control valve is widely used in power plants, chemical industry, oil refining and other production processes with high safety requirements.

Main advantages of pneumatic control valve:

Receive continuous gas signal and output linear displacement (after power on / gas conversion device, it can also accept continuous electrical signal). Some can output angular displacement when equipped with rocker arm. It has positive and negative functions. The movement speed is large, but the speed will be slower when the load increases. The output force is related to the operating pressure. The reliability is high, but the valve can't be maintained after the air source is interrupted (it can be maintained after adding the retention valve). It is inconvenient to realize subsection control and program control. The maintenance is simple and the adaptability to the environment is good. High output power. It has explosion-proof function.

Electric control valve:

Electric actuator of electric control valve is mainly used in power plant or nuclear power plant, because it needs a smooth, stable and slow process in high-pressure water system. The main advantages of electric actuator are high stability and constant thrust which can be applied by users. The thrust generated by the largest actuator can be as high as 225000kgf. Only the hydraulic actuator can achieve such a large thrust, but the cost of the hydraulic actuator is much higher than that of the electric actuator. The anti deviation ability of electric actuator is very good, and the output thrust or torque is basically constant, which can overcome the unbalanced force of medium and achieve the accurate control of process parameters, so the control accuracy is higher than that of pneumatic actuator. If equipped with servo amplifier, it is easy to realize the exchange of positive and negative effects, and it is also easy to set the position state of the off signal valve (keep / full open / full close). When there is a fault, it must stay in the original position, which is not done by the pneumatic actuator. The pneumatic actuator must use a set of combined protection system to realize the position protection.

The disadvantages of the electric control valve are as follows:

The structure is more complex, more prone to failure, and because of its complexity, the technical requirements for field maintenance personnel are relatively higher; the motor operation to generate heat, if the regulation is too frequent, it is easy to cause motor overheating, generate thermal protection, but also increase the wear of the reduction gear wheel; in addition, the operation is slow, from the regulator output a signal to the control valve response It takes a long time to move to the corresponding position, which is not as good as pneumatic and hydraulic actuators.