Electric valve is the main accessory electric actuator, namely electric actuator, which is mainly used in power plants or nuclear power plants, because the high-pressure water system requires a smooth, stable and slow process. The main advantages of electric actuators are high stability and constant thrust that users can apply. The maximum thrust generated by the actuator can be as high as 225000kgf. Only hydraulic actuators can achieve such a large thrust, but the cost of hydraulic actuators is higher than that of electric 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 more than that of the pneumatic actuator high. If equipped with a servo amplifier, the positive and negative effects can be exchanged easily, and the signal-off valve position state (hold/full open/full close) can be easily set, and it must stay in the original position when a fault occurs. Pneumatic actuators can't do it, and pneumatic actuators must rely on a set of combined protection system to achieve position retention.
The structure of the electric actuator is more complicated, and it is more prone to failure, and because of 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 heat Protection will also increase the wear on the reduction gear; in addition, it runs slower. It takes a long time from the regulator output a signal to the control valve to move to the corresponding position in response. This is because it is not as good as pneumatic, Place for hydraulic actuator.
Pneumatic valves are mainly equipped with pneumatic actuators, namely pneumatic actuators. The actuator and adjustment mechanism of the pneumatic actuator are a unified whole, and the actuators are divided into two types: membrane type and piston type. The piston type has a long stroke and is suitable for occasions that require greater thrust; while the membrane type has a small stroke 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 protection, it has a wide range of applications in power plants, chemical industries, oil refining and other production processes with high safety requirements.
Pneumatic actuators receive continuous air signals and output linear displacement (after power-on/air conversion device, continuous electrical signals can also be received), and some can output angular displacement when equipped with a rocker arm. There are positive and negative functions. The moving speed is high, but the speed will slow down when the load increases. The output force is related to the operating pressure. The reliability is high, but the valve cannot be maintained after the air supply is interrupted (it can be maintained after adding the retaining valve). It is inconvenient to realize segment control and program control. The maintenance is simple, and the adaptability to the environment is good. The output power is large. With explosion-proof function.