Electric valve actuators are primarily used in power plants or nuclear power plants because high-pressure water systems require a smooth, stable, and slow process. The main advantages of electric actuators are their high stability and the constant thrust applicable to the user. The maximum thrust generated by an electric actuator can reach up to 225,000 kgf, a figure only hydraulic actuators can achieve, but hydraulic actuators are significantly more expensive than electric actuators. Electric actuators have excellent anti-deviation capabilities, and the output thrust or torque is essentially constant, effectively overcoming the unbalanced forces of the medium and achieving accurate control of process parameters. Therefore, their control precision is higher than that of pneumatic actuators. When equipped with a servo amplifier, it is easy to achieve interchangeable direct and reverse action, and the valve position status (hold/fully open/fully closed) can be easily set when the signal is interrupted. In case of failure, the valve will remain in its original position, which is impossible for pneumatic actuators, which require a combined protection system to maintain position.
The main disadvantages of electric actuators are:
The structure is more complex, making it more prone to failure. Due to its complexity, the technical requirements for on-site maintenance personnel are relatively higher. The motor generates heat during operation, and if the adjustment is too frequent, it can easily cause the motor to overheat and trigger thermal protection. It will also increase the wear on the reduction gears. In addition, it is slower to operate. It takes a long time for the control valve to respond to a signal output by the controller and move to the corresponding position. This is where it is inferior to pneumatic and hydraulic actuators.
Pneumatic Valves - Shanghai Liangda Valves
The actuator and regulating mechanism of a valve pneumatic actuator are a unified whole. There are two types of actuators: diaphragm and piston. Piston actuators have a long stroke and are suitable for applications requiring large thrust; while diaphragm actuators have a shorter stroke and can only directly drive the valve stem. Due to their advantages such as simple structure, large output thrust, smooth and reliable operation, and explosion-proof safety, pneumatic actuators are widely used in production processes with high safety requirements, such as power plants, chemical plants, and oil refineries.
The main advantages of pneumatic actuators:
It accepts continuous pneumatic signals and outputs linear displacement (after adding an electro-pneumatic conversion device, it can also accept continuous electrical signals). Some models, when equipped with a rocker arm, can output angular displacement.
It has both positive and negative functions.
It has a high movement speed, but the speed will slow down when the load increases.
The output force is related to the operating pressure.
It has high reliability, but the valve cannot maintain its position after the gas supply is interrupted (it can maintain its position after adding a position-holding valve).
It is inconvenient to implement segmented control and program control.
It is easy to inspect and maintain, and has good adaptability to the environment.
It has a large output power.
It has explosion-proof function.
