1. The hazards of high oil temperature in hydraulic systems
The hydraulic system also loses a certain amount of energy during the process of transmitting energy, which leads to an increase in the system's oil temperature. Generally speaking, the ideal hydraulic system oil temperature is between 30 degrees Celsius and 55 degrees Celsius. This is because the oil within this range is in a perfect state in terms of viscosity, lubricity, and wear resistance, with high system transmission efficiency and quality. Once the oil temperature exceeds the range that the system can withstand, it will lead to a series of related failures.
Excessive oil temperature can reduce the viscosity of the oil. Taking the L-AN32 full loss system oil as an example, when the oil temperature is 20 degrees Celsius, its viscosity is 100mm2/s, when the oil temperature rises to 50 degrees Celsius, it is 20mm/s, and when the oil temperature rises to 70 degrees Celsius, the viscosity is only 9mm2/s. As a result, it leads to an annual decline, increased oil leakage, and reduced system efficiency. In addition, a decrease in viscosity can damage the oil film, increase friction and resistance, lead to severe wear and system heating, and further increase temperature.
2. Analysis of the causes of high oil temperature in hydraulic systems
2.1 Small fuel tank area, poor heat dissipation, and malfunction of the heat dissipation system
The area of the fuel tank should be selected based on the usage and heat dissipation conditions of the system. If the design is not reasonable enough or the installation is not in place, it will cause poor heat dissipation function of the system, thereby causing the oil to heat up.
As a cooling device for hydraulic oil, the radiator plays an important role, and the structure usually used for radiators is a cold structure. If there are too many oil stains or surface deposits on the heat sink, it will affect the normal function and use of the radiator, leading to high oil temperature. Once the thermostat in the cooling system loses its function, it will also cause the system's oil temperature to become too high. When the liquid level in the fuel tank is too low, it causes the system to not have enough oil for normal circulation, which can also lead to high oil temperature [3].
2.2 Improper pressure adjustment
If the pressure inside the system is too high, it will cause the overflow and pressure reduction functions of the relief valve to fail to function correctly, resulting in increased internal leakage and thus raising the system oil temperature. For hydraulic systems with back pressure valves on the return oil circuit, if the pressure regulation of the back pressure valve is too high, it will cause a large return oil resistance, thereby increasing the oil temperature. If there is a blockage in the return oil filter or aging and delamination of the return oil pipeline, it will also increase the back pressure, increase the pressure loss during oil flow, and cause the oil temperature to be too high.
2.3 Improper selection of hydraulic oil grades
As an important measure of oil viscosity, the selection of marking oil grades is crucial. The working condition of the system is directly affected by the viscosity of the oil. Once the viscosity is too high, it will increase the loss of oil flow, reduce the efficiency of oil transmission, and lead to an increase in oil temperature; If the viscosity is too low, it will increase leakage, reduce system volumetric efficiency, and also increase oil temperature. On the contrary, the viscosity of oil is also affected by temperature. The higher the temperature, the lower the viscosity of the oil. If an inappropriate oil grade, especially an inappropriate oil viscosity, is selected, it will pose a serious threat to the normal operation of the hydraulic system.
2.4 Transmission shifting brake pad synovium causes overheating of oil temperature
Another important reason for the heating of hydraulic system oil temperature is the heat generated by the sliding film of the transmission shift brake pad. At the moment when the transmission shifts and the brake pads start to engage and disengage, a brief sliding film is generated, which is inevitable and mechanical that cannot be overcome. At this point, the hydraulic transmission oil will have a lubricating and cooling effect, which means that the heat generated by the sliding film will be transferred to the hydraulic transmission oil. Once the synovial membrane lasts too long, it will cause a rapid increase in the working temperature of the hydraulic transmission oil. The main reasons for the longer sliding time of the brake pads during gear shifting in a single gearbox are threefold:
(1) The friction brake pads are severely damaged, reducing the friction force of the synovium and preventing complete engagement under high torque conditions.
(2) The pressure of the shifting hydraulic cylinder did not reach a fixed value, resulting in weak clamping of the brake pads. The failure of internal seals in the system is the main reason for the decrease in working cylinder pressure. Due to the failure of internal seals in the system, it can lead to internal leakage or severe wear of hydraulic pumps, insufficient oil supply pressure, or pressure regulating valves being stuck or springs failing.
(3) The transmission oil filter is blocked, causing the oil circuit to be blocked, the flow rate to be insufficient, and the pressure to be established slowly.
3. Improvement measures for high oil temperature in hydraulic system
3.1 Reasonable design of fuel tank
The function of the fuel tank is not only to store oil, but also to dissipate heat. Due to the small volume of the fuel tank, if the emission conditions are poor, the temperature inside the tank will increase. Therefore, improving the heat dissipation of the fuel tank, fully utilizing the heat dissipation effect of the tank wall, and appropriately expanding the capacity of the fuel tank are effective means to suppress the problem of hydraulic system overheating.
3.2 Reasonable selection of hydraulic oil
The reasonable selection of hydraulic oil is an important factor affecting oil temperature. For a certain hydraulic system, only specific hydraulic oil can be selected. If the viscosity of the hydraulic oil is high, it should be replaced with hydraulic oil with lower viscosity. Due to the different accuracies of hydraulic equipment, the selection of hydraulic oil should also comply with the grade and quality of the hydraulic equipment, and try to choose a liquid with a small change in viscosity stability characteristic curve? Oil. If there are special circumstances, similar grades of oil can be used instead, but different grades of oil cannot be mixed together, otherwise it will cause the oil to deteriorate and increase its temperature.
At the same time, the state of the oil often changes during the use of working oil, so it is necessary for the market to observe the state of the oil to prevent it from deteriorating. Special attention should be paid to the mixture of bubbles and water oil. The quality of cleaning work directly affects the service life of working oil, which is closely related to machine operating conditions, working oil quality, oil temperature, and filtration accuracy. When the oil temperature exceeds the specified value? Immediately uninstall for spatiotemporal operation, and resume operation when the oil temperature returns to normal.
3.3 Selecting energy-saving hydraulic pumps
The hydraulic pump is the main cause of heat loss and oil temperature rise in the system, so the selection of energy-saving pressure pumps is particularly important. The pressure limiting variable blade hydraulic pump is more suitable for machine tool actuators with fast travel. When the machine tool moves forward rapidly, the pump flow rate is high under the oil supply pressure of the hydraulic pump; Compared with the use of high-pressure and high flow quantitative pumps, this has less power loss and reduces the probability of oil heating, enabling control of temperature rise.
Conclusion
This article analyzes the hazards and causes of high oil temperature in the hydraulic station of mining hoists from three aspects, as well as prevention and control measures. The main reasons for high oil temperature in the hydraulic station of mining hoists include four aspects: small oil tank area, heat dissipation difference and system failure, improper pressure adjustment, improper selection of hydraulic oil grade, and overheating caused by transmission shift brake pad sliding film. At the same time, specific improvement measures were proposed based on the above situation, including three aspects: reasonable design of the oil tank, reasonable selection of hydraulic oil, and selection of energy-saving hydraulic pumps.
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2025-03-27