Advantages and disadvantages of electric valves and pneumatic valves

Advantages and disadvantages of electric valves and pneumatic valves

Pneumatic valves

The actuator and adjustment mechanism of the pneumatic actuator are unified and the actuators are of the diaphragm type and the piston type. The long piston stroke is suitable for applications requiring a large thrust; the diaphragm stroke is small and can only directly drive the valve stem. Because the pneumatic actuator has the advantages of simple structure, large output thrust, stable and reliable action, and 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 advantages of pneumatic actuators:

1. Accept continuous gas signal and output linear displacement (continuous electrical signal can be received after power/gas conversion device). Some can be equipped with angular arm displacement after outputting the rocker arm.

2. There are positive and negative functions.

3. The moving speed is large, but the speed will be slower when the load increases.

4. The output force is related to the operating pressure.

5, high reliability, but the valve can not be maintained after the gas source is interrupted (can be maintained after the retaining valve).

6. Inconvenient to implement segmentation control and program control.

7, easy maintenance and adaptability to the environment.

8, the output power is large.

9, with an explosion-proof function.

Electric valve

Electric actuators are mainly used in power plants or nuclear power plants because of the need for a smooth, stable and slow process in high pressure water systems. The main advantages of the electric actuator are the high stability and the constant thrust that the user can apply. The thrust generated by the larger 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 higher than that. The electric is much higher. The anti-deviation ability of the electric actuator is very good. The thrust or torque of the output is basically constant, which can overcome the imbalance force of the medium and achieve accurate control of the process parameters. Therefore, the control accuracy is better than that of the pneumatic actuator. high. If a servo amplifier is used, it is easy to achieve the exchange of positive and negative effects, and it is also easy to set the state of the off-signal valve position (hold/full-open/full-off), and when it is faulty, it must stay in place, this is Pneumatic actuators do not, pneumatic actuators must be secured by means of a combined protection system.

The main disadvantages of electric actuators are:

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 thermal protection. It will also increase the wear on the reduction gear; in addition, it will run slowly, and it will take a long time to output a signal from the regulator and move to the corresponding position in response to the valve response. This is not as good as pneumatic or hydraulic actuation. The place of the device.