(1) Different energy sources used
The pneumatic components and devices can be used to centrally supply air to the air compressor station, and the working pressure of the respective pressure reducing valves can be adjusted according to the requirements of use and the control points. The hydraulic valves are equipped with a return line for the tank to collect used hydraulic oil. The pneumatic control valve directly discharges compressed air to the atmosphere through the exhaust port.
(2) Different requirements for leakage
The hydraulic valve requires strict leakage to the outside, while a small amount of leakage inside the component is allowed. For pneumatic control valves, internal leakage is not permitted in principle except for gap-sealed valves. Internal leakage of pneumatic valves poses a risk of accidents.
For pneumatic piping, a small amount of leakage is allowed; and leakage of hydraulic piping will cause system pressure drop and environmental pollution.
(3) Different requirements for lubrication
The working medium of the hydraulic system is hydraulic oil. The hydraulic valve does not have the requirement of lubrication. The working medium of the pneumatic system is air and the air is non-lubricating. Therefore, many pneumatic valves require parts of the oil mist lubrication valve to select materials that are not susceptible to water corrosion. Or take the necessary rust prevention measures.
(4) Different pressure ranges
Pneumatic valves have a lower operating pressure range than hydraulic valves. Pneumatic valves typically have a working pressure of less than 10 bar and a few can reach up to 40 bar. However, the working pressure of the hydraulic valve is very high (usually within 50 MPa). If the pneumatic valve is used above the maximum allowable pressure. Serious accidents often occur.
(5) Different use characteristics
Generally, the pneumatic valve is more compact than the hydraulic valve, light in weight, easy to integrate and install, and the valve has a high operating frequency and a long service life. The pneumatic valve is developing in the direction of low power and miniaturization, and a low-power solenoid valve with a power of only 0.5W has appeared. It can be directly connected to the microcomputer and PLC programmable controller, or it can be installed on the printed circuit board together with the electronic device. The gas circuit is connected through the standard board, which saves a lot of wiring. It is suitable for pneumatic industrial manipulators and complicated manufacturing. Assembly line and other occasions.