What hydraulic fluid is suitable for lifting machinery

The pollution and improper selection of hydraulic oil is one of the important factors causing the failure of crane hydraulic system operation. Therefore, the correct and reasonable selection of hydraulic oil is of great significance to improve the reliability and economy of crane hydraulic equipment operation, extend the service life of the system and components, ensure the safe operation of equipment and prevent accidents.

Requirements for the use of hydraulic fluids for lifting machines

1, appropriate viscosity: viscosity is one of the main factors to be considered in the hydraulic system of lifting machinery. Viscosity is the oil flow performance index, said the size of the friction resistance between molecules when the oil flow, viscosity is too large to increase the local picture in the pipeline transport resistance, the working process of energy loss increases, the main engine no-load loss increases, temperature rise, in the main pump oil suction end may appear "hole" phenomenon; Too small viscosity can not ensure good lubrication conditions of the mechanical part, aggravate the wear of parts, and the system leakage increases, causing the volume efficiency of the pump to decline.

2. Good viscosity-temperature characteristics: viscosity-temperature refers to the degree of oil viscosity change with temperature rise and fall, usually expressed by viscosity-temperature index. The larger the viscosivity index is, the smaller the oil viscosity decreases with the increase of temperature, so that the internal leakage of the system is not too large.

3. Good oxidation resistance and hydrolysis stability: the working temperature of general hydraulic oil is best between 30℃ and 80℃, because the life of hydraulic oil is closely related to the working temperature. When the oil temperature exceeds 60℃, every increase of 8℃, the service life of the oil will be halved. That is to say, the life of oil at 90℃ is about 10% of that at 60℃, and the reason is oxidation. At atmospheric pressure, each liter of oil contains slightly less than 0.1 liter of air. In fact, oxygen is always present, and it reacts with the hydrocarbons in the oil, causing it to oxidize slowly, turning the oil black and increasing its viscosity. Eventually the oxide is no longer dissolved in the oil, but deposited somewhere in the system as a brown layer of goo. This will cause valve bonding, ball bearing spool and hydraulic pump piston friction increase, at the same time oxidation to produce corrosive acid to destroy the hydraulic components.

4, fire resistance and shear stability: in order to improve the viscosity index of the oil, the oil is often added to polymethacrylate, polyisobutene and other polymer, these substances molecular chain is long, in the flow of hydraulic components of the slit, by great shear action, often make the molecular chain is broken, so that the viscosity temperature characteristics of the oil decline. During the hoisting operation, the frequent reversing of the reversing valve and the throttling elements require the hydraulic oil to have strong shear resistance.

5, and sealing material, environmental compatibility: hydraulic oil will make its contact with the sealing element swelling, softening, hardening, so that the sealing material lose the sealing effect. Hydraulic system due to leakage, seal failure and other reasons, resulting in the flow of hydraulic oil, if the hydraulic oil is incompatible with the environment, it will cause pollution to the environment.

6, good wear resistance and lubrication: the purpose is to reduce mechanical friction, ensure the service life of the main engine.

7. Good fire resistance: hydraulic oil should have higher flash point, ignition point and spontaneous combustion point.