The valve actuator nothing more than pneumatic, electrical, fluid movement (electric hydraulic) these three, its use performance each have advantages and disadvantages, the points of Assyria.

1, pneumatic actuator

Most of today's industrial control occasions the actuators are pneumatic actuator, as do with air power, in contrast, than electric and hydraulic to economical and practical, and simple structure, easy to control and maintenance. By maintaining perspective, pneumatic actuators than other types of actuators is easy to operation and calibration, at the scene also can easily realize about positive and negative swap. Its biggest advantage is safety, when using a locator, for inflammable and explosive environment is ideal, and electric signal if not explosion-proof or essence safe have potential for flint and cause danger of fire. So, although now electric control valve application more and more widely, but in the chemical field, pneumatic control valve is occupying the absolute superiority.

Pneumatic actuators is the main shortcomings: response is slow, poor control accuracy, resistance to deviation ability is bad, this is because gas compressibility, especially using large pneumatic actuators, the air filled cylinder and emptying need time. But it should be no problem, because many conditions do not request high control accuracy and extremely fast response and resistance to deviation ability.

2, electric actuators

Electric actuators is mainly used in power plant or nuclear power plant, because in high pressure water system requires a smooth, stability and slow process. Electric actuators is the main advantage of high stability and the user can be applied in constant thrust, and the thrust produced by the largest actuators can be as high as 225000 KGF, can achieve so big thrust only hydraulic actuator, but hydraulic actuator cost than electric high many. Electric actuators from resistance ability is very good, the output of the thrust and torque is basically constant, can very good overcome medium unbalanced force, achieve the process parameters of accurate control, so the control accuracy higher than the pneumatic actuators. If with servo amplifier, can easily achieve positive and negative effect of interchange, also can easily set off signal valve position state (keep/open/seated), and failure, be sure to stay in situ, this is pneumatic actuators for less than, pneumatic actuator must use a combination protection system to realize the bit.

Electric actuator faults mainly include: structure more complicated, more likely to malfunction, and because of its complexity, the field maintenance personnel's technical requirements is relative to a few taller; The motor running to produce hot, if the adjusted too frequent, easy to cause the motor overheating, produce thermal protection, at the same time will also strengthen the reduction gear wear and tear, The other is the operation is relatively slow, from the regulator output a signal to control valve response and movement to the corresponding position, it takes a long time, this is it as pneumatic, hydraulic actuator place.

3, hydraulic actuators

When need to abnormal anti deviation ability and high thrust and the formation of fast speed, we often choose hydraulic or electric hydraulic actuator. Because the liquid incompressibility, using hydraulic actuators is the advantage of the better resistance to deviation ability, this to control working condition is very important, because when the control element close to the seat when the throttle working condition is unstable, the more pressure difference is big, this kind of situation is severe. In addition, hydraulic actuators are running very smooth, fast response, so can achieve high precision control. Electro-hydraulic actuators is the motor, oil pump, the electro-hydraulic servo valve integrated into an organic whole, as long as the access power supply and control signal can work, and hydraulic actuators and cylinder close, just than cylinder ability higher pressure, its work need external hydraulic system, the factory equipped with hydraulic station and need in pipeline road, by contrast, or electro-hydraulic actuator some more convenient. Hydraulic actuator major defect is high cost, large heavy physical examination, especially complex and need special engineering, so most of them are used in some such as power plants, petrochemical, and other comparative special occasions.