Pneumatic control valve refers to all kinds of pneumatic elements that control the pressure, flow and flow direction in the pneumatic system and ensure the normal operation of the pneumatic actuator or mechanism. The elements that control and regulate the compressed air pressure are known as pressure control valves. The element that changes and controls the direction of the air flow is called a directional control valve.
Structural characteristics: The structure of the pneumatic control valve can be decomposed into the valve body (including the valve seat and the valve hole) and the valve center, according to the relative position of the two, there are two normally closed type and normally open type. Valves can be divided into three types of valves from the structure: stop type, slide column type and skateboard type.
In addition to the above three types of control valves, there are also logic elements that can realize certain logical functions, including jet elements with unmovable components within the components and pneumatic logic elements with movable components. In the structure principle, the logic element is basically the same as the direction control valve, only the volume and diameter are small, generally used to realize the logic operation function of the signal. In recent years, with the miniaturization of pneumatic components and the large number of application of PLC control in pneumatic systems, the application scope of pneumatic logic components is gradually decreasing. From the control mode,Pneumatic Control Ball Valve can be divided into two categories: intermittent control and continuous control. In the intermittent control system, the pressure control valve, flow Control Valve and direction control valve are usually used to realize the program operation; in the continuous control system, in addition to the pressure and flow control valve, the servo, proportional control valve are also used to continuously control the system.
Comparison of pneumatic Control Valves and hydraulic valves:
1. Different energy sources used: the pneumatic elements and devices can adopt the centralized gas supply method of the air pressure station, and adjust the operating pressure of each pressure reducing valve according to the different use requirements and control points. The hydraulic valves are equipped with return oil lines to facilitate the oil tank to collect the used hydraulic oil. The pneumatic control valve can discharge the compressed air directly into the atmosphere through the exhaust port.
2. Different requirements for leakage: the hydraulic valve has strict requirements for outward leakage, while a small amount of leakage inside the component is allowed. For Pneumatic Diaphragm Valve, no internal leakage is allowed, in principle, except for clearance-sealed valves. The internal leakage of the pneumatic valve is a risk of accident. For pneumatic pipes, little leakage is allowed; the leakage of hydraulic pipe will cause system pressure drop and pollution to the environment.
3. Different requirements for lubrication: the working medium of hydraulic system is hydraulic oil, the hydraulic valve does not require lubrication; the working medium of pneumatic system is air, the air has no lubrication, so many pneumatic valves need oil fog lubrication. Valves should be selected materials that are not susceptible to water corrosion, or necessary rust prevention measures should be taken.
4. Different pressure range: the operating pressure range of pneumatic valve is lower than that of hydraulic valve. The working pressure of the pneumatic valve is usually within 10bar, and a few can reach within 40bar. But the operating pressure of the hydraulic valve is very high (usually within 50Mpa). If the Pneumatic Ball Valve is used above the maximum allowable pressure. Serious accidents can often occur.
5. Different use characteristics: the general pneumatic valve is compact than the hydraulic valve structure, light weight, easy to integrate the installation, the valve working frequency is high, long service life. Pneumatic Valve is developing towards low power and miniaturization, and a low power solenoid valve with a power of only 0.5W has appeared. It can be directly connected with the microcomputer and PLC programmable controller, or can be installed on the printed circuit board together with Electric Valve devices, connecting the gas and electric circuit through the standard board, saving a large number of wiring, suitable for pneumatic industrial manipulator, complex production and manufacturing assembly lines and other occasions.