Maintenance and care methods for the hydraulic system of excavators

The main granular impurities in the hydraulic system come from the normal mechanical wear of the hydraulic system. Dust can also be brought in by the air intake of the oil tank. The "disassembly and assembly contamination" during the major overhaul of the hydraulic system: "Iron filings and impurities crushed by the large hydraulic pump, which are less than 10 microns smaller than the filtration accuracy of the hydraulic oil filter element, all remain in the oil."

During the 2000-hour operation of the hydraulic oil, a small amount of fine air bubbles will be added to the oil as it flows. From then on, the oil will undergo oxidation. The acidic substances produced after the oxidation of the hydraulic oil will change the color of the oil, making it red or black, and increase its corrosiveness to metals. The oil sludge sediment produced after rusting will clog the tiny gaps of various oil circuit valves on the hydraulic oil filter element, hydraulic oil radiator and distributor.

In addition, due to the temperature differences between day and night in various regions and the natural cold and heat during mechanical operation, the hot air in the hydraulic oil tank cools down and turns into water droplets. Therefore, the hydraulic oil inevitably comes into contact with water. Water, air, and acidic substances produced after oxidation can all cause rust and corrosion on metals, affecting the normal operation of the hydraulic system.

3. In the hydraulic oil tank, air bubbles mixed in the oil circulate with the oil, which will cause the system pressure to drop, the lubrication conditions to deteriorate, and abnormal noises to occur. The hydraulic piston rods will turn black, the mechanical speed will slow down, and the movements will be incoherent. This is commonly known as "mechanical cerebral thrombosis".

While sediment clogs the hydraulic oil radiator, the hydraulic oil will heat up to over 70 degrees Celsius. At high temperatures, the hydraulic oil loses its anti-wear and lubricating functions. If the hydraulic oil is exposed to high temperatures for a long time, it will increase mechanical wear and vibration. In addition, bubbles also increase the contact area between the oil and air, accelerating the oxidation of the oil. Since the hydraulic oil radiator is located on the outside of the engine radiator, under the effect of the engine fan's suction at high temperatures, the temperature of the antifreeze inside the hydraulic oil radiator will also increase, causing abnormal engine heat dissipation and high temperature. As a result, the vehicle speed will also slow down significantly. At high temperatures, hydraulic oil can also cause oil pipelines to burst, oil seals to rupture, and piston rods to turn black, causing serious economic losses to car owners.

More attention should be paid when changing the hydraulic oil

According to statistics, the hydraulic oil in the hydraulic oil tanks of most excavators is exactly half of the total oil used in the entire hydraulic system of the machine. The remaining hydraulic oil is stored in the hydraulic pump, motor, multi-way valve, hydraulic cylinder and pipelines of various parts. When changing the oil. If only the hydraulic oil in the fuel tank is replaced instead of all the hydraulic oil in the vehicle's hydraulic system, this method is merely blending old oil with new oil.

Therefore, to fundamentally solve the cleaning problem of the hydraulic system, merely changing the oil in the hydraulic oil tank is not enough. Even if all the oil in the hydraulic system oil tank is drained, there will still be a lot of old oil remaining in the hydraulic system. When new oil is injected, it will inevitably be contaminated by the residual old oil in the system, thereby greatly reducing the cleanliness of the hydraulic oil. Therefore, this oil change method cannot solve the problem of oil cleanliness. Only by circulating and vacuum filtering the old oil in the system while the hydraulic system is operating can the cleanliness of the hydraulic oil be fundamentally improved.

The above conclusion concludes that the high temperature of the hydraulic oil in excavators is directly related to regular maintenance and oil change. Frequent filter element replacement cannot solve any major problems!!

According to the oil standards for construction machinery, the contamination level of general hydraulic oil should be controlled at NAS≤8 grade. When new hydraulic oil is filled in the oil station bucket, the filtration accuracy is required to be 1 to 3 microns.

2. According to the oil pressure design standards for the hydraulic oil circuit of construction machinery, the filtration accuracy of the hydraulic oil filter element can only be limited to a minimum of ≥10 microns. Even for some loaders, the filtration accuracy of the filter element can be even higher. If it is less than 10 microns, it will affect the return oil flow and the working speed of the vehicle, and even cause the filter element to be damaged!

The most commonly used selection of hydraulic oil filter elements for construction machinery: the filtration accuracy is 10μm50%, the pressure range is 1.4 to 3.5 MPa, the rated flow rate is 40 to 400L/min, and the recommended replacement time is 1000 hours.

The service life of hydraulic oil is usually 4,000 to 5,000 hours, which is approximately two years.

During the spring and autumn seasons each year, the temperature difference between day and night is large. After a excavator has been working for a whole day and stops working at night, the oil inside the hydraulic oil tank is at a high temperature, while the air outside the tank is at a low temperature. When the hot air inside the tank meets the cold air outside, it will condense into water droplets at the top of the tank and fall into the hydraulic oil. Over time, water will mix into the hydraulic oil. It then evolves into acidic substances that corrode the metal surface. Under the dual effects of mechanical operation and pipeline pressure impact, metal particles that fall off the metal surface will mix in the hydraulic oil. At this time, if the hydraulic oil is not purified, large metal particles will be filtered out by the filter element, while particles smaller than 10μm cannot be filtered out by the hydraulic filter element. The unfiltered wear particles mixed in the hydraulic oil will further aggravate the re-wear of the metal surface. Therefore, experts suggest that the filtration and purification time for hydraulic oil should be 2,000 to 2,500 hours or once a year, and it should also be purified once when changing to new oil. Purify the old oil in the system to turn it into new oil, and then add new oil. In this way, the remaining old oil will not contaminate the new oil.

The best approach is to regularly filter and purify the oil in the oil tank and oil circuit system with a special vacuum oil purifier for hydraulic oil. This will remove the excess water and mechanical impurities in the oil, keep the cleanliness of the oil and hydraulic system at NAS6-8 level for a long time, and keep the water content within the national standard range. This will prevent the oil from aging easily and prevent the excavation equipment from being damaged. Only in this way can the oil be durable and avoid more loss and waste!