Electric valve

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 users can apply. The maximum thrust generated by the actuator can reach up to 225000kgf, and only hydraulic actuators can achieve such a large thrust. However, the cost of hydraulic actuators is much higher than that of electric actuators. The anti deviation ability of electric actuators is very good, and the output thrust or torque is basically constant, which can effectively overcome the unbalanced force of the medium and achieve accurate control of process parameters. Therefore, the control accuracy is higher than that of pneumatic actuators. If equipped with a servo amplifier, it is easy to achieve the exchange of positive and negative effects, and it is also possible to easily set the cut-off signal valve position state (keep/fully open/fully closed). However, in case of a fault, it must remain in its original position, which cannot be achieved by pneumatic actuators. Pneumatic actuators must rely on a combination protection system to achieve position retention.

The main drawbacks of electric actuators are:

The structure is more complex and prone to failure, and due to its complexity, the technical requirements for on-site maintenance personnel are relatively higher; The operation of the motor needs to generate heat. If adjusted too frequently, it can easily cause the motor to overheat, generate thermal protection, and also increase wear on the reduction gear; In addition, it runs slowly, taking a longer time from the regulator outputting a signal to the regulating valve responding and moving to the corresponding position, which is why it is inferior to pneumatic and hydraulic actuators.

Pneumatic valve

valve

The actuator and adjustment mechanism of pneumatic actuators are a unified whole, and there are two types of actuators: diaphragm type and piston type. The piston type has a long stroke, suitable for situations that require high thrust; The thin film type has a smaller stroke and can only directly drive the valve stem. Due to its simple structure, high output thrust, stable and reliable operation, and safety and explosion-proof features, pneumatic actuators are widely used in production processes with high safety requirements such as power plants, chemical industry, and oil refining.

The main advantages of pneumatic actuators are:

Accepting continuous gas signals, outputting linear displacement (after power/gas conversion device, continuous electrical signals can also be accepted), and some can output angular displacement when equipped with a rocker arm.

It has both positive and negative effects.

The movement speed is high, but the speed will slow down as the load increases.

The output force is related to the operating pressure.

High reliability, but the valve cannot be maintained after the gas source is interrupted (it can be maintained after adding a positioning valve).

It is inconvenient to implement segmented control and program control.

Easy maintenance and repair, with good adaptability to the environment.

The output power is relatively high.

It has explosion-proof function.