Performance comparison between pneumatic control valves and hydraulic valves
(1) The energy used is different.
The pneumatic components and devices can adopt the method of centralized air supply in air compressor station to adjust the working pressure of the respective relief valves according to the different requirements and control points. Hydraulic valves are equipped with return line to facilitate the collection of used hydraulic oil. The pneumatic control valve can directly discharge compressed air into the atmosphere through the exhaust port.
(2) Different requirements for leakage.
Hydraulic valves are strict in leakage to the outside, while a small amount of leakage inside the components is permitted. For pneumatic control valves, internal leakage is not allowed in principle except for the gap sealed valve. Internal leakage of pneumatic valves can cause accidents.
For pneumatic pipeline, a little leakage is allowed, while the leakage of hydraulic pipeline will cause pressure drop and environmental pollution.
(3) Different requirements for lubrication.
The working medium of hydraulic system is hydraulic oil, and there is no requirement of lubrication for hydraulic valves. The working medium of pneumatic system is air, which has no lubrication, so many pneumatic valves need oil mist lubrication. Valve parts should be selected for materials which are not susceptible to water corrosion or take necessary rust preventive measures.
(4) Pressure ranges are different.
The working pressure range of the pneumatic valve is lower than that of the hydraulic valve. The working pressure of pneumatic valve is usually less than 10bar, and a few can reach 40bar. But the working pressure of the hydraulic valve is very high (usually less than 50Mpa). If the pneumatic valve is used above the maximum allowable pressure. There are always serious accidents.
(5) Different usage characteristics
Generally, pneumatic valves have compact structure, light weight, easy integration and installation, high working frequency and long service life. Pneumatic valves are developing in the direction of low power and miniaturization. Low power solenoid valves with a power of only 0.5W have been developed. It can be directly connected with microcomputers and PLC programmable controllers. It can also be installed on printed circuit boards together with electronic devices. It can connect the pneumatic circuit through standard boards, which saves a lot of wiring. It is suitable for pneumatic industrial manipulators, complex production and assembly lines and other occasions.
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