1. The prime mover is the engine, not the motor. Therefore, the rotating speed varies greatly, generally from 600 to 2,500rpm, and even higher.The hydraulic pump connected with the requirement must be adapted and ensure normal operation.
2. Bad working conditions.Construction machinery is generally outdoor work, therefore, the wind, rain, sun exposure, environmental pollution can be said to be serious.For the hydraulic medium, it requires good tightness of the oil tank and strict prevention of hydraulic medium pollution.For hydraulic parts, not only the friction pairs of moving parts are required to have good abrasion resistance, but even their corrosion resistance should be considered.It is also necessary to consider appropriate and effective protective measures for the sports component;To improve the reliability and life of hydraulic valve.
3. Small fuel tank and high oil temperature.The high temperature of the medium of the hydraulic system is harmful to the hydraulic system and its components.For example, high temperature can accelerate the deterioration of hydraulic medium to form carbon deposition, which will aggravate the wear of hydraulic parts and endanger the service life and reliability of hydraulic parts.The high temperature makes the hydraulic seal aging faster and lose its sealing performance.High temperature reduces the viscosity of the hydraulic medium and increases leakage, etc.
4. Drastic pressure changes and large hydraulic impact.The pressure of ordinary hydraulic system is relatively stable, therefore, the hydraulic impact is relatively small.When working with engineering machinery, the pressure of hydraulic system is variable due to the variable external load, which often forms a large hydraulic impact.This has a serious impact on the life and reliability of hydraulic parts.For example, for a hydraulic valve, the hydraulic valve body can crack;Bend the hydraulic valve core;Make pipe burst or joint thread vibration loose even seal is sheared and so on.
5. Large partial load.In general, there is relatively large radial off-load of the construction machinery actuator. For example, the hydraulic cylinder will produce serious problems such as leakage, jitter and strain under off-load.
6. Small volume, large flow and light weight are required for hydraulic parts.As construction machinery is generally walking machinery, so the space is very limited, so it is particularly important to save the occupied area, convenient installation and so on.This is also the reason that engineering machinery should be more multi-way valve.Therefore, we must consider casting channel to ensure maximum flow.The hydraulic parts with thin wall and sufficient strength, minimum volume and lightest weight must be designed according to the pressure level to meet the special requirements of engineering machinery.If conditions permit, consider using lightweight materials such as aluminum body, aluminum alloy or engineering plastic spools.
7. Good control performance.That is to require hydraulic parts to be stable, accurate, and fast implementation of effective control.
8. Life and reliability of hydraulic valve.Due to the above reasons, engineering machinery has relatively high requirements for its hydraulic parts, such as impact resistance, wear resistance, corrosion resistance, high temperature resistance, small and lightweight, etc.