Use of oil in hydraulic system of Kobelco excavator
1. Prevent the mixing of moisture
The harm of water mixed in hydraulic oil:
① When the water mixed in the hydraulic oil accounts for more than 1%, the new hydraulic oil will immediately become turbid and the lubricity will decrease;
②The water mixed in the hydraulic oil can accelerate the oxidation and deterioration of the hydraulic oil;
③The water and the fine metal particles in the hydraulic oil generate insoluble components, which increase the source of pollutants in the oil;
④Hydraulic oil vapor pressure increases, which is prone to cavitation;
⑤Moisture forms water vapor, which condenses into water droplets or condensation when the temperature drops, and adheres to the surface of metal components, causing metal corrosion and even perforation. At the same time, the peeling scale also pollutes the hydraulic system.
The main ways that water enters the system are:
① Moist air, rain water and water used to wash the machine enter through the fuel tank filler opening, breathing apparatus and gaps;
②For machines with coolers and heaters, the working medium water or steam seeps into the hydraulic oil;
③Because the hydraulic parts and the pipeline or the pipeline are not tightly sealed, the external moisture enters;
④Because the hydraulic oil is in the process of transportation and storage, or because there is moisture in the refueling equipment when refueling.
In view of the different ways of water entering the hydraulic system, the following measures can be used to prevent:
① Maintain a good seal of the hydraulic system. During each inspection, the damaged or aging sealing material should be replaced. It is best to replace all the old sealing materials.
② Prevent rainwater and humid air from entering the hydraulic system.
③ Regularly take samples from the bottom of the fuel tank to check the moisture and impurities to ensure that the moisture content does not exceed 0.2%. If the moisture content is too much, it must be heated and dehydrated, and then filtered several times with filter paper.
2. Prevent contamination of chemicals
The possible chemical contamination in hydraulic oil includes solvents, hydraulic oil decomposition deposits and surface active substances. The chlorinated solvent will be hydrolyzed into hydrochloric acid in the system, corroding the metal surface of the component.
When the temperature of the hydraulic oil mixed with water and gas rises to a certain level, it will produce violent chemical effects, generating resin particles, acid, etc., increasing the pollution of the hydraulic oil, and the formed acid will affect the metal surface of the system components. Corrosion.
Surface active substances can remove solid dirt and water on the surface of the components, but the cleaned substances will diffuse into the entire hydraulic system, making the system pollution more serious.
3. Prevent the mixing of air
The influence of air mixed in, especially dissolved in hydraulic oil, is negligible under normal working pressure. However, under low pressure conditions, the dissolved air will escape, generate bubbles, and form cavitation, which will have the following effects on the hydraulic system.
① When the bubbles reach the high pressure area, they are crushed by rapid compression, which will not only produce noise and vibration, but also cause the oil to overheat.
②The compressibility of air causes the working device to crawl and affect the stability of work.
③The oil is mixed with or dissolved in a large amount of air and the air escapes to produce bubbles, which will deteriorate the oil and reduce the service life, especially when the oil generates local high temperature due to cavitation, the oil oxidation and deterioration will increase.
④ The hydraulic components are quickly damaged internally due to the impact and cavitation caused by cavitation, which affects the reliability and life of the hydraulic system.
According to the different ways of air entering the system, the following measures should be taken:
①Ensure that the oil level of the fuel tank is at the specified height, the suction pipe and the oil return pipe should be kept below the oil level, and there is a partition in the middle.
② Prevent the phenomenon of low pressure (vacuum) below latm in the system.
③Always check whether the sealing device is damaged and whether the screws at the pipe joints and each joint surface are tightened.
Exhaust valves should be installed at the upper part of the hydraulic cylinder.
1. Prevent the mixing of solid impurities
The consequences of hydraulic oil being contaminated by solid impurities are:
① Destroy the lubricating oil film and increase body wear. About 60% of machine failures are caused by the wear of solid particles in the hydraulic oil on the body, and the degree of such wear increases with the increase of ion concentration, particle hardness and particle size. After the sliding surface of the machine body is worn, the gap will increase, the leakage will increase, the power of the machine will be reduced, the life of the components will be shortened, or even damaged.
② Block the orifice, filter hole, various gaps and passages, so as to make the valve malfunction, make the pump difficult to run, and produce cavitation or noise.
③ Wear the sealing material and increase external leakage.
④ The metal and metal compound particles in the solid impurities can catalyze the oxidation and deterioration of oil. The corrosive substances produced after oil deterioration will increase the corrosion of the machine.
The most common method to prevent solid impurities from entering hydraulic oil is filtration.
The hydraulic oil must be filtered before use, and it must pass through the oil filter when injecting the hydraulic oil. A hydraulic system must be equipped with coarse oil filter (suction pipe end) and fine oil filter (pressure pipe, oil return pipe) at the same time. Filtration accuracy requirements: 7~14 MPa is 50~100/zin, 14~21MPa is 10~50"m.
