The grader is the main machine used in earthwork engineering for shaping and leveling operations, and is widely used in road and airport ground leveling operations on large areas. However, I did not notice that the daily maintenance and maintenance will shorten its life. Let's take a look at it together.
1. Requirements for hydraulic oil performance
In hydraulic transmission, hydraulic oil is both a medium for transmitting power and a lubricant, and it also plays a sealing role in some components. The heat in the system is also diffused through the oil, so it also plays a role in heat dissipation. Therefore, in order to ensure that the hydraulic system works reliably, effectively and economically, the hydraulic oil must ensure the following requirements:
1) Appropriate viscosity. Viscosity is the magnitude of frictional resistance between molecules when oil flows. When the viscosity is too large, the resistance when the oil flows is large, the energy loss is large, and the system efficiency is reduced. In addition, the no-load loss of the main engine increases, the temperature rises fast and the working temperature is high, and the phenomenon of "cavitation" easily occurs at the oil suction end of the main pump. If the viscosity is too small, the good lubrication conditions of the hydraulic components cannot be guaranteed, the wear of the components is increased, the leakage is increased, and the efficiency of the hydraulic system is also reduced.
2) Good viscosity-temperature characteristics. Viscosity-temperature characteristics refer to the degree to which oil viscosity rises and falls with temperature, and is usually expressed by viscosity index. The greater the viscosity index, the smaller the decrease in oil viscosity as the temperature rises during the operation of the hydraulic system, so that the internal leakage of the hydraulic system will not be too large. The viscosity index should not be lower than 90.
3) Good abrasion resistance and lubricity. The purpose is to reduce mechanical friction and ensure sufficient oil film strength under different pressure, speed and temperature conditions.
4) High chemical reaction stability, not easy to oxidize and deteriorate. Practice has proved that for every 10 ° C increase in oil temperature, the chemical reaction rate increases about twice. The hydraulic oil with good anti-oxidation stability is not prone to oxidative deterioration after long-term use, which can ensure the normal circulation of hydraulic oil.
5) The quality should be pure, and the content of mechanical impurities, moisture and dust should be reduced as much as possible.
6) The impact on the seal should be small.
7) The anti-emulsification property is better, and it is not easy to cause foam. Anti-emulsification refers to the ability of oil mixed with water and after stirring, it does not become an emulsion and water is separated from it. Anti-foaming refers to the ability to mix air into the oil and not to form emulsions and bubbles after being stirred out of the oil. After mixing with water or air, the volume modulus of hydraulic oil is reduced, the compressibility is increased, the hydraulic components act slowly, and they are prone to shock and vibration.
8) Good anti-rust performance. The hydraulic oil covers the surface of the parts to prevent them from being corroded by oxidation.
9) Good stability of shear resistance. In order to improve the viscosity index of the oil, polymer polymers such as polymethacrylate and polyisobutylene are often added to the oil. These substances have long molecular chains, and the oil is greatly sheared when it flows through the slit of the hydraulic element. The effect will often break the chain of the molecule and reduce the viscosity and temperature characteristics of the oil.
10) The ignition point and flash point should meet the ambient temperature, and the volatility should be small to ensure the safe use of hydraulic oil.
2. The cause and harm of hydraulic oil pollution
2.1 Source of pollutants
1) Contaminants in new oil. Although hydraulic oil is refined and processed under relatively clean environmental conditions, it is contaminated by pipelines, oil drums and oil storage tanks during transportation and storage. Some dust, sand, rust, Moisture and other liquids.
2) Residual contaminants in components and systems. During the processing, assembly and cleaning of hydraulic components and hydraulic systems, some contaminants will remain due to incomplete cleaning.
3) External intrusion of pollutants. In the process of hydraulic components and mechanical work, due to imperfect sealing of the fuel tank, damage to the component seals and protective devices, some contaminants such as dust, sand, and moisture invade from the outside of the system.
4) Contaminants generated inside the hydraulic system. The hydraulic system itself will generate some solid particulate pollutants in the work, including metal particles or rubber powder produced by the wear and corrosion of hydraulic components, and pollutants produced by the oxidation of oil.
2.2 The hazards of hydraulic oil pollution
1) Contaminants often block the throttle valve and pressure damping hole when they are blocked, or even block the valve core, causing the working pressure and speed of the hydraulic system to change from time to time, affecting its normal work.
2) Accelerate the wear of hydraulic pumps, motors, and valve blocks, causing an increase in internal leakage.
3) The water mixed in the hydraulic oil corrodes the metal and accelerates the aging and deterioration of the hydraulic oil.
4) The air mixed into the hydraulic oil will cause noise, vibration, creeping, cavitation and impact phenomena, thereby deteriorating the working performance of the hydraulic system.
3. Maintenance of hydraulic oil
3.1 Prevent oil pollution
Among the various pump and valve components used in the grader, the matching clearance and working surface between the relative moving parts are small, and there are many damping holes and slit-type control valve ports in the hydraulic component. If the oil is mixed with dirt If there is any object, it will block, even scratch the mating surface, increase leakage, or even catch the valve core, causing the component to malfunction. Therefore, keeping oil clean is the key to hydraulic system maintenance.
1) The hydraulic oil must be strictly filtered. When filling the hydraulic oil tank, it should pass through an oil filter of more than 120 mesh.
2) Regularly check the cleanliness of the oil, and replace it regularly according to the working conditions. When replacing, the 40L of oil in the hydraulic system should be discharged as much as possible. Among them, the method using the outside circulation of the system is more operable. The method is to drain the waste oil from the fuel tank and radiator first, and then add new oil. Remove the oil return pipe into the oil tank, start the engine, and let the waste oil flow out completely from the oil return pipe. Special emphasis is on the timely observation of changes in the oil level in the tank, and the safe height of the oil level should be ensured. When changing to new oil, the filter element of the filter should be replaced at the same time.
3) The hydraulic components should not be easily disassembled. If they must be disassembled, the parts should be cleaned with kerosene or diesel and placed in a clean place to avoid mixing of impurities during reassembly.
