① The viscosity of hydraulic oil, volumetric efficiency and working efficiency of hydraulic system all decrease, leakage increases, and even the mechanical equipment can not work normally.
② The parts of the hydraulic system expand due to overheating, destroying the original normal fit clearance of the relative motion parts, resulting in increased friction resistance, hydraulic valve easy to jam, at the same time, the film becomes thinner, mechanical wear increases, resulting in the precision fit surface of the pump, valve, motor and so on due to premature wear and failure or scrap.
(3) Accelerate the aging and deterioration of rubber seals, shorten their life, and even lose their sealing performance, so that the hydraulic system is seriously leaking.
(4) oil vaporization, water evaporation, easy to cavitation hydraulic components; The oil oxidizes to form colloidal deposits, which are easy to block the holes in the oil filter and hydraulic valve, so that the hydraulic system can not work normally.
Therefore, the high temperature of hydraulic oil will seriously affect the normal use of the machine, reduce the service life of hydraulic components, and increase the maintenance cost of construction machinery.
Causes and preventive measures of high oil temperature
1. Improper selection of oil products
The brand, quality and viscosity grade of oil do not meet the requirements, or different brands of hydraulic oil are mixed, resulting in the viscosity index of hydraulic oil is too low or too high. If the oil viscosity is too high, the power loss increases and the oil temperature rises. If the viscosity is too low, the leakage will increase and the oil temperature will rise.
Preventive measures: The selection of oil should be determined by the brand recommended by the manufacturer and the working environment and temperature factors of the machine. For some machines with special requirements, hydraulic oil should be selected; When the hydraulic components and system maintenance is inconvenient, should choose good performance antiwear hydraulic oil.
2 Serious pollution
The construction site environment is harsh, with the increase of machine working time, the oil is easy to mix impurities and dirt, polluted hydraulic oil into the pump, motor and valve clearance, will scratch and destroy the precision and roughness of the surface, so that the leakage increase, oil temperature rise.
Preventive measures: Generally, the oil is changed after more than 1000 hours of accumulated work. When changing the oil, pay attention not only to drain the old oil in the tank, but also to replace the old oil in the entire system pipeline and working loop; It is best to use more than 120 mesh filter when refueling, and add enough oil according to the regulations, so that the oil has enough circulating cooling conditions. In case of sudden failure caused by hydraulic oil pollution, be sure to filter or replace the hydraulic system oil. For example, a YZT14G roller hydraulic oil oil temperature is too high, insufficient vibration power failure; The inspection found that the hydraulic oil was milky white, deteriorated and viscosity decreased. After replacing the hydraulic oil, the roller operation returned to normal.
3 The oil level in the hydraulic tank is too low
If the amount of oil in the hydraulic tank is too small, the hydraulic system will not have enough flow to take away the heat generated, resulting in the oil temperature rise.
Preventive measures: In the actual operation and maintenance process, strictly comply with the operating rules on the oil level of hydraulic oil. For example, a PC2003 hydraulic excavator, hydraulic oil temperature is too high after working for a period of time; Check the hydraulic tank, found that the oil level is much lower than the specified value, because the hydraulic system is too short of oil, so that the hydraulic oil circulation is too fast, not enough static heat dissipation, resulting in higher oil temperature; After adding sufficient hydraulic oil according to the regulations, the temperature of hydraulic oil immediately drops to the normal range.
4 Air is mixed into the hydraulic system
The air mixed with hydraulic oil will escape from the oil and form bubbles in the low pressure area. When it moves to the high pressure area, these bubbles will be crushed by the high pressure oil, and be dramatically compressed and released a lot of heat, causing the oil temperature to rise.
Preventive measures: check the sealing of the inlet pipe interface frequently to prevent air from entering; Also, exhaust the air in the system after each oil change. For example, a PY184 grader hydraulic oil temperature is too high, accompanied by hydraulic noise; The inspection found that the hose connected to the oil inlet of the hydraulic pump was slightly damaged, and the air was inhaled, resulting in high oil temperature. After replacing the hose, the grader ran in good condition.
