Reasons for high hydraulic oil temperature and cooling measures
June 06, 2023
The temperature of hydraulic oil in construction machinery is often controlled between 30~55 ℃. At this point, the viscosity, lubricity, and wear resistance of the oil are all in a good state, and the system transmission efficiency is high. When the oil temperature exceeds 65 ℃, the viscosity of the oil will significantly decrease, leakage will increase, and the oil film at each sliding part will be damaged, exacerbating the wear of hydraulic components and accelerating the rate of oil temperature rise. When the oil temperature reaches above 80 ℃, the clearance between relative moving components and the operating state will change abnormally due to the different coefficient of thermal expansion of hydraulic components. The gap increases, the oil leakage worsens, and the gap decreases. The phenomenon of "jamming" between components may occur, making them unable to move, and it can also cause thermal deformation of the machine, damaging the original accuracy.
Reasons for high hydraulic oil temperature 01 Poor heat dissipation The accumulation of thick dirt on the surface of the radiator will cause poor heat dissipation and ventilation, resulting in high oil temperature. The low liquid level in the hydraulic oil tank will cause insufficient oil circulation in the system, and it will also cause high oil temperature in the system. 02 Improper selection of hydraulic oil grade Improper selection of hydraulic oil grades, especially viscosity indicators, will directly threaten the normal operation of the hydraulic system. So only hydraulic oil with a specific viscosity range and minimal viscosity change can be selected. When selecting hydraulic oil, specific construction areas and seasons should also be considered. In winter construction in northern regions, hydraulic oil with lower viscosity should be selected, while in summer, hydraulic oil with higher viscosity should be selected. For machines with clear oil standards, hydraulic oil should be strictly added according to regulations. 03 Improper pressure adjustment When the system pressure is adjusted too high, the overflow valve cannot overflow and depressurize normally, resulting in an increase in internal leakage and an increase in system oil temperature. For hydraulic systems with back pressure valves on the return oil circuit, if the back pressure valve is adjusted too high, it can also cause excessive oil temperature due to excessive return oil resistance. When the return oil filter is blocked or the return oil pipeline is aged and delaminated, it will also cause high back pressure, increase the pressure loss during oil flow, and cause high oil temperature. 04 Hydraulic pump suction The hydraulic pump suction causes excessive air to mix in the oil, resulting in cavitation and hydraulic impact under high pressure, accompanied by strong vibration and noise, resulting in a rapid increase in system oil temperature. The reason for hydraulic pump suction is mostly due to blockage of the oil inlet filter element or oil inlet pipe. If the oil pipe connection is loose or the oil seal of the pilot pump and main hydraulic pump transmission shaft is damaged, it can also cause the hydraulic pump to suck empty. 05 internal leakage If there is severe internal leakage during the energy transfer process, it will increase the volume loss of the system, and the lost energy will be converted into heat energy, causing the system oil temperature to be too high. If the gap between components is too small, friction will occur between the relative moving parts, which can also increase the oil temperature. If the gap is too large, it will cause serious leakage. 06 Component wear Severe wear and tear of components in the hydraulic system can cause excessive oil temperature in the system. Many parts of the components in the system are sealed by gaps. If these hydraulic components are worn, they will cause an increase in internal leakage, leading to an increase in oil temperature, a decrease in viscosity of the oil, and further increase in internal leakage, causing further increase in oil temperature and forming a vicious cycle.
