Introduction of pneumatic control valve

                                   Introduction of pneumatic control valve

Pneumatic control valve refers to various pneumatic components that control the pressure, flow and flow direction of air flow in the pneumatic system and ensure the normal operation of pneumatic actuator or mechanism. The structure of pneumatic control valve can be divided into two parts: valve body (including valve seat and valve hole) and valve core. According to their relative positions, there are normally closed type and normally open type. The valve can be divided into three types: stop valve, sliding column valve and sliding plate valve.

Pneumatic control valve refers to various pneumatic components that control the pressure, flow and flow direction of air flow in the pneumatic system and ensure the normal operation of pneumatic actuator or mechanism. The element that controls and regulates the pressure of compressed air is called pressure control valve. The element that controls and regulates the flow of compressed air is called the flow control valve. The element that changes and controls the flow direction of air flow is called directional control valve. In addition to the above three types of control valves, there are also logic elements that can realize certain logic functions, including jet elements without movable parts and pneumatic logic elements with movable parts. In terms of structural principle, the logic element is basically the same as the directional control valve, but the volume and diameter are small. It is generally used to realize the logic operation function of the signal. In recent years, with the miniaturization of pneumatic components and the large application of PLC control in pneumatic system, the application range of pneumatic logic components is gradually decreasing. From the control mode, pneumatic control can be divided into intermittent control and continuous control. In intermittent control system, pressure control valve, flow control valve and direction control valve are usually used to realize program action; In the continuous control system, in addition to the pressure and flow control valves, servo and proportional control valves are also used to continuously control the system.

Comparison between pneumatic control valve and hydraulic valve

（1） Different energy sources are used

Pneumatic components and devices can adopt the method of centralized air supply from air compression station to adjust the working pressure of their respective pressure reducing valves according to different use requirements and control points. The hydraulic valves are equipped with oil return pipelines to facilitate the oil tank to collect the used hydraulic oil. The pneumatic control valve can directly discharge the compressed air to the atmosphere through the exhaust port.

（2） Different requirements for leakage

The hydraulic valve has strict requirements for external leakage, while a small amount of leakage inside the element is allowed. For pneumatic control valves, except for clearance sealed valves, internal leakage is not allowed in principle. The internal leakage of Pneumatic conrtol valve may cause accidents.

For pneumatic pipes, a little leakage is allowed; The leakage of hydraulic pipeline will cause system pressure drop and environmental pollution.

（3） Different requirements for lubrication

The working medium of the hydraulic system is hydraulic oil, and the hydraulic valve has no requirements for lubrication; The working medium of pneumatic system is air, which has no lubricity, so many Pneumatic conrtol valves need oil mist lubrication. The parts of the valve shall be made of materials that are not easy to be corroded by water, or necessary anti rust measures shall be taken.

（4） Different pressure ranges

The working pressure range of Pneumatic conrtol valve is lower than that of hydraulic valve. The working pressure of Pneumatic conrtol valve is usually less than 10bar, and a few can reach less than 40bar. However, the working pressure of hydraulic valves is very high (usually within 50MPa). If the Pneumatic conrtol valve is used above the maximum allowable pressure. Serious accidents often occur.

（5） Different use characteristics

Compared with hydraulic valves, general pneumatic control valves have compact structure, light weight, easy integration and installation, high working frequency and long service life. Pneumatic conrtol valve is developing towards low power and miniaturization, and a low power solenoid valve with power of only 0.5W has emerged. It can be directly connected with microcomputer and PLC programmable controller, and can also be installed on printed circuit board together with electronic devices. The ventilation circuit is connected through standard board, which saves a lot of wiring. It is suitable for pneumatic industrial manipulator, complex production and assembly line and other occasions.