The normal operation of hydraulic system of construction machinery is a main sign of its good technical condition. Hydraulic oil is the guarantee of reliable operation of the hydraulic system. Hydraulic oil plays the role of transferring pressure, lubricating, cooling and sealing in the hydraulic system. The pollution of hydraulic oil is the main reason of the hydraulic system failure and the decline of durability. 80% of hydraulic system failures are caused by oil pollution in the system. Therefore, correct maintenance of hydraulic system is the basis of reliable operation of hydraulic system. The key to maintain the hydraulic system is to remove the pollution source. Hydraulic system pollution mainly comes from the following factors.
I. causes of hydraulic oil pollution are as follows:
1. Particle impurities: the main granular impurities in the hydraulic system are from normal mechanical wear of the hydraulic system, dust in the air, butter brought by crushing hammer, disassembly pollution in the maintenance of hydraulic system, iron powder crushed by hydraulic big pump, copper powder and rubber particles. All impurities less than 10 microns are in the oil hydraulic (the filter precision of the original hydraulic oil filter core is generally 10 microns).
2. Water and air: due to the temperature difference between morning and evening climate and shutdown, the hot air in the oil tank will become water droplets after cooling. Therefore, the hydraulic oil will inevitably contact with water. As well as the sludge sediment generated after metal corrosion and rust will also clog the hydraulic oil filter core, hydraulic oil radiator and dispenser small valve gaps in each oil way, affecting the normal operation of the hydraulic system.
Therefore, in addition to the particulate impurities and dust directly worn by the system, the pollutants in the hydraulic system, such as water, air and acidic substances formed by oxides, also produce large amounts of contaminated precipitates. The increase of impurity increases mechanical wear and vibration and valve body blockage.
Second, replacing hydraulic oil is old oil blending new oil, can not from the source of system pollution
According to statistics, the hydraulic oil installed in the hydraulic oil tank of most excavators is only part of the total oil consumption of the hydraulic system of the whole machine, which is only 2/3 of the total oil consumption of the system at most. The remaining 1/3 old hydraulic oil is stored in the pipelines of hydraulic pump, motor, multi-way valve, hydraulic oil cylinder and each part. When changing the oil, replace the hydraulic oil in the oil tank instead of replacing all the hydraulic oil in the hydraulic system of the whole vehicle. When the new oil is injected, it will be contaminated by the residual oil in the system, thus greatly reducing the cleanliness of the hydraulic oil. In fact, the oil change of excavator is to use the old oil in the system to mix the new oil, so the oil change method is not able to solve the problem of system pollution. Only when the hydraulic system is operated and the old oil in the circulating filtration system is carried out with the high-precision filter equipment can the cleanliness of the hydraulic oil be improved fundamentally.
Thirdly. Maintenance of hydraulic system of engineering machinery, continuous filtration and purification is the key
1. According to the oil standard of engineering machinery, generally the contamination degree of hydraulic oil should be controlled at level 8 of NAS.
2. According to the hydraulic pressure design standard of hydraulic oil circuit of engineering machinery, the filtration accuracy of hydraulic oil filter core can only be limited to a minimum of 10 microns or more. If it is less than 10 micrometers, it will affect the return oil flow and the working speed of the car, and even hold back the filter core! Therefore, the most commonly used selection of hydraulic oil filter core for construction machinery is that the filter accuracy is 10 micron 50%, the pressure range is 1.4 ~ 3.5mpa, and the rated flow rate is 40 ~ 400L/min. However, the hydraulic oil filter core of the original vehicle cannot be filtered for particles less than 10 microns, which will always exist in the hydraulic system.
3. The temperature difference between day and night after climate change and work stoppage will be condensed into water droplets on the top of the oil tank and fall into the hydraulic oil. It then becomes acidic and corrodes the surface of the metal. Under the dual action of mechanical operation and pipeline pressure impact, metal particles falling off the metal surface will be mixed in the hydraulic oil. In addition, the oil has a large number of particles less than 10 micron in the fluid mixed in the hydraulic oil, will again increase metal surface wear.
Therefore, reducing the water content of hydraulic oil and reducing impurities under 10 microns is the fundamental method to reduce the failure rate of hydraulic system. How to reduce the water content of hydraulic oil and impurities below 10 microns in the hydraulic system of engineering machinery? Please pay attention to the second phase of the project machinery hydraulic oil decontamination secrets.