Regulating valve pneumatic electric actuator

Actuators used by the control valve is nothing more than pneumatic, electric, hydraulic (electro-hydraulic) these three, its performance has its own advantages and disadvantages, described below. 1, Pneumatic Actuators: Actuators used in most industrial control systems today are pneumatic actuators. Because they are powered by gas source, they are more economical than electric and hydraulic motors. They are simple in structure and easy to grasp and maintain. From a maintenance point of view, pneumatic actuators are easier to operate and calibrate than other types of actuators and can be easily reversed in the field. Its biggest advantage is safety, which is ideal for flammable and explosive atmospheres when locators are used, while there is a potential fire hazard for electrical signals that are not explosion-proof or intrinsically safe. Therefore, although the electric control valve is now more and more widely used, but in the chemical industry, pneumatic control valve is still occupying an absolute advantage. The main drawbacks of pneumatic actuators are: slow response, poor control accuracy, and poor resistance to deflection due to the compressibility of the gas, especially when large pneumatic actuators are used, filling the cylinder with air and emptying it time. However, this should not be a problem as many operating conditions do not require a high degree of control accuracy and extremely fast response and resistance to deviation. 2, electric actuator: electric actuator mainly used in power plants or nuclear power plant, because in the high-pressure water system requires a smooth, stable and slow process. The main advantage of the electric actuator is a high degree of stability and the user can apply a constant thrust, the maximum actuator thrust can be as high as 225000kgf, to achieve such a large thrust only hydraulic actuators, hydraulic actuators cost more than electric Much higher. Anti-deviation ability of electric actuator is very good, the output thrust or torque is basically constant, can be very good to overcome the imbalance of media to achieve accurate control of process parameters, so the control accuracy than the pneumatic actuator to high. If equipped with servo amplifier, you can easily achieve the exchange of positive and negative effects, but also can easily set off signal valve state (keep / fully open / close), and failure, we must stay in place, this is Pneumatic actuators can not do that, the pneumatic actuator must rely on a combination of protection systems to achieve Paul bit. The main shortcomings of the electric actuator: the structure is more complex, more prone to failure, and because of its complexity, on-site maintenance personnel technical requirements are relatively higher; motor operation to generate heat, if the adjustment is too frequent, easily lead to Motor overheating, resulting in thermal protection, but also increase the wear on the reduction gear; the other is to run slower, a signal output from the regulator to the control valve to move to that corresponding position, takes a long time, which It is not as aerodynamic, hydraulic actuators place. 3, hydraulic actuators: When the need for abnormal anti-deviation ability and high thrust and rapid formation speed, we often use hydraulic or electro-hydraulic actuator. Because of the fluid's incompressibility, the advantage of using a hydraulic actuator is its superior resistance to deflection, which is important for adjusting conditions because the throttling condition is unstable when the adjusting element is near the valve seat. The more Pressure drop, the more powerful this situation. In addition, the hydraulic actuator is running very smooth, fast response, so can achieve high-precision control. Electro-hydraulic actuator is the motor, pump, electro-hydraulic servo valve integrated into one, as long as the access to power and control signals to work, and hydraulic actuators and cylinders are similar, but higher than the cylinder to withstand higher pressures, it's Work requires an external hydraulic system, the plant needs to be equipped with hydraulic station and pipeline, in contrast, electro-hydraulic actuator or more convenient. The main drawback of hydraulic actuator is the high cost, large physical examination bulky, particularly complex and require specialized engineering, so most are used in some such as power plants, petrochemical and other special occasions.