Introduction to the actuator of the hottest regula

2022-07-28
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Introduction to the actuator of control valve

the actuator used for control valve is no more than pneumatic, electric and hydraulic (electro-hydraulic), and its performance has its own advantages and disadvantages, which are described below

1. Pneumatic actuator of regulating valve: Nowadays, the actuators used in most industrial control occasions are pneumatic actuators. Because the air source is used as the power, compared with electric and hydraulic actuators, it is more economical, simple in structure and easy to master and maintain. From the maintenance point of view, pneumatic actuators are easier to operate and calibrate than other types of actuators, and they can also be easily interchanged on site. Its biggest advantage is safety. When the positioner is used, it is ideal for flammable and explosive environment. If the electric signal is not explosion-proof or intrinsically safe, it has the potential risk of fire caused by ignition. Therefore, although the application of electric control valve is more and more extensive, pneumatic control valve still occupies an absolute advantage in the chemical industry

2. Electric actuator of regulating valve: the electric actuator is mainly used in power plants or nuclear power plants, because a smooth, stable and slow process is required in the high-pressure water system. The main advantages of the electric actuator are high stability and constant thrust available to users. The maximum thrust generated by the actuator can be as high as 225000kgf. Only the hydraulic actuator rotor pump can achieve such a large thrust, but the cost of the hydraulic control valve is much higher than that of the electric control valve. The anti deviation ability of the electric control valve is very good. The output thrust or torque is basically constant, which can well overcome the unbalanced force of the medium and achieve the accurate control of the process parameters. Therefore, the control accuracy is higher than that of the pneumatic control valve. If the servo amplifier is used, it can easily realize the exchange of positive and negative reactions, and it can also easily set the off signal valve position status (hold/fully open/fully closed). In case of failure, it must stay in the original position, which is not done by the pneumatic control valve. The pneumatic control valve can better improve the quality of publishing products. The pneumatic control valve must achieve position preservation with the help of a set of combined protection system

the disadvantages of the actuator of the electric control valve mainly include: the structure is complex, which is more prone to failure, and because of its complexity, the technical requirements for on-site maintenance personnel are relatively higher; The motor shall generate heat during operation. If it is adjusted too frequently, it is easy to cause the motor to overheat and generate thermal protection. At the same time, it will also increase the wear of the reduction gear; In addition, the operation is slow. It takes a long time from the output of a signal from the regulator of the regulating valve to the corresponding position in response to the response of the regulating valve. This is where it is inferior to pneumatic and hydraulic actuators

3. Hydraulic actuator of control valve: when abnormal anti deviation ability, high thrust and fast forming speed are required, we often choose hydraulic or electro-hydraulic actuator. Because of the incompressibility of the liquid, the advantage of using the hydraulic actuator is the better anti deviation ability, which is very important for the regulating condition of the regulating valve, because the flow condition is unstable when the regulating element is close to the valve seat, and the greater the pressure difference, the worse the situation. In addition, U.S. officials argued that the hydraulic actuator runs very smoothly and responds quickly, so it can achieve high-precision control. The electro-hydraulic actuator integrates the motor, oil pump and electro-hydraulic servo valve. It can work as long as it is connected to the power supply and control signal. The hydraulic actuator is similar to the cylinder. How to reduce the friction coefficient of the electronic universal tensile machine is just that it can withstand higher pressure than the cylinder. Its work requires an external hydraulic system. The factory needs to be equipped with a hydraulic station and oil pipeline. In contrast, the electro-hydraulic actuator is more convenient

the main drawback of the hydraulic actuator of the control valve is that it is expensive, bulky, especially complex and requires special engineering, so most of it is used in some special occasions such as power plants and petrochemicals

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