1. The harm of high hydraulic oil temperature ① the viscosity, volumetric efficiency and working efficiency of hydraulic system are reduced, the leakage is increased, and even the mechanical equipment can not work normally.
② The parts of the hydraulic system expand due to overheating, which destroys the original normal fit clearance of the relative moving parts, resulting in increased friction resistance and easy jamming of the hydraulic valve. At the same time, it thins the lubricating oil film and increases mechanical wear. As a result, the precision fit surfaces of pumps, valves and motors become invalid or scrapped due to premature wear.
③ Accelerate the aging and deterioration of rubber seals, shorten the service life, and even lose its sealing performance, resulting in serious leakage of the hydraulic system.
④ Oil vaporization and water evaporation are easy to cause cavitation corrosion of hydraulic components; The oil oxidizes to form colloidal deposits, which is easy to block the small holes in the oil filter and hydraulic valve, so that the hydraulic system can not work normally.
Therefore, high hydraulic oil temperature will seriously affect the normal use of the machine, reduce the service life of hydraulic components, and increase the maintenance cost of construction machinery. 2. Causes and preventive measures of high hydraulic oil temperature
(1) Improper selection of oil 名媛直播
The brand, quality and viscosity grade of the oil do not meet the requirements, or the hydraulic oil of different brands is mixed, resulting in low or high viscosity index of the hydraulic oil. If the oil viscosity is too high, the power loss increases and the oil temperature increases; If the viscosity is too low, the leakage increases and the oil temperature increases.
Preventive measures: the selection of oil shall be determined according to the brand recommended by the manufacturer, the working environment of the machine, temperature factors, etc. For some machines with special requirements, special hydraulic oil shall be selected; When the maintenance of hydraulic components and systems is inconvenient, anti-wear hydraulic oil with good performance shall be selected.
(2) Serious pollution
The environment of the construction site is harsh. With the increase of the working time of the machine, impurities and dirt are easy to be mixed in the oil. The polluted hydraulic oil will enter the matching clearance of the pump, motor and valve, which will scratch and damage the accuracy and roughness of the matching surface, increase the leakage and increase the oil temperature.
Preventive measures: generally change the oil after working for more than 1000 hours. When changing the oil, pay attention not only to drain the old oil in the oil tank, but also to replace the old oil in the whole system pipeline and working circuit; When refueling, it is best to use more than 120 mesh filter screen, and add enough oil according to the regulations to make the oil have sufficient circulating cooling conditions. In case of sudden failure caused by hydraulic oil pollution, be sure to filter or replace the oil used in the hydraulic system. For example, a yzt14g roller has the fault of high hydraulic oil temperature and insufficient vibration force; The inspection found that the hydraulic oil was milky white, deteriorated and the viscosity decreased. After replacing the hydraulic oil, the roller returned to normal operation.
(3) The oil level in the hydraulic oil tank is too low
If there is too little oil in the hydraulic oil tank, the hydraulic system will not have enough flow to take away the heat generated, resulting in the rise of oil temperature.
Preventive measures: during the actual operation and maintenance, strictly abide by the provisions on the hydraulic oil level in the operating procedures. For example, a PC2003 hydraulic excavator has the fault of high hydraulic oil temperature after working for a period of time; Check the hydraulic oil tank and find that the oil level is much lower than the specified value. Due to the excessive lack of oil in the hydraulic system, the hydraulic oil circulates too fast and fails to stand for heat dissipation, resulting in the rise of oil temperature; After adding enough hydraulic oil as required, the hydraulic oil temperature will immediately drop to the normal range.
(4) Air mixed in hydraulic system
The air mixed into the 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 broken by the high-pressure oil, compressed sharply and release a lot of heat, causing the oil temperature to rise.
Preventive measures: regularly check the tightness of sealing places such as oil inlet pipe interface to prevent air from entering; At the same time, exhaust the air in the system after each oil change. For example, the hydraulic oil temperature of a py184 grader is too high, accompanied by hydraulic noise; The inspection found that the connecting hose at the oil inlet of the hydraulic pump was slightly damaged and inhaled air, resulting in excessive oil temperature. After replacing the hose, the grader operated in good condition.
(5) Oil filter blocked
When passing through the oil filter, abrasive particles, impurities and dust will be adsorbed on the filter element of the oil filter, resulting in an increase in oil absorption resistance and energy consumption, resulting in an increase in oil temperature.
Preventive measures: clean and replace the oil filter regularly. For the oil filter with blockage indicator, clean or replace the filter element according to the instructions; The performance, structure and validity period of the filter element must meet its use requirements. For example, when a TY220 bulldozer is operating, the oil temperature alarm alarms continuously, and it is found that there is a burning smell of oil smoke and oil at the torque converter, and the oil level in the steering oil tank is low; The inspection result is that the fault is caused by the blockage of the oil suction screen of the torque converter return pump. Because the filter screen is full of deposits, the oil leaked from the torque converter cannot be pumped back to the steering oil tank in time. The more it accumulates, the greater the placing resistance of the torque converter, the more heat generated by friction, and finally the oil temperature rises too fast; After cleaning the filter screen, the oil temperature returns to normal. As another example, the hydraulic transmission system of a CATD8N crawler bulldozer sends out a high temperature alarm, and there is abnormal noise at the transmission part; Disassemble the oil filter and check the filter element. It is found that it contains a large amount of powdery dirt; After replacing the filter element, the fault disappears.
(6) The hydraulic oil cooling circulation system is not working properly.
Generally, water-cooled or air-cooled oil coolers are used to forcibly cool the oil temperature of the hydraulic system. The cooling coefficient of water-cooled cooler will be reduced due to dirty fins or poor water circulation; The air-cooled cooler will block the gap of the cooling fin of the cooler due to excessive oil contamination, which is difficult to be dissipated by the fan, resulting in the increase of oil temperature.
Preventive measures: regularly check and maintain the hydraulic oil cooling circulation system. Once a fault is found, it must be shut down immediately for troubleshooting. For example, after a cpcd60d hydraulic drive forklift works for a period of time, the driving force of the torque converter is insufficient and the steering wheel turns heavily (one pump is used for hydraulic transmission and power steering); After several inspections, it was found that the oil temperature was too high due to the blockage of the ventilation hole of the air-cooled oil cooler. After dredging, the fault was eliminated. As another example, when a k-702 loader cooler works for less than 3h after starting, the torque converter oil temperature alarm indicator on the instrument panel flashes, indicating that the hydraulic oil temperature is too high. First check the oil quantity and oil quality, and the result is that the oil quantity is sufficient and the oil quality is good; Check the oil filter again to ensure it is not dirty; After checking the cooler, it is found that the oil sludge has blocked part of the cooler and oil holes. After cleaning the cooler, everything is normal.
(7) Serious wear of parts
The gear, pump body and side plate of gear pump, cylinder block and port plate of plunger pump and motor, cylinder block hole and plunger, valve rod and valve body of directional valve are sealed by clearance. The wear of these components will cause the increase of internal leakage and the increase of oil temperature.
Preventive measures: repair or replace the parts with excessive wear in time. According to statistics, under normal circumstances, the wear of imported hydraulic pumps and motors has been quite serious after five or six years of operation and domestic 名媛直播 have been working for two or three years, so they must be repaired in time. Otherwise, it will work normally when the machine is cold, but after working for 1-2h, the movement speed of each mechanism of the system will obviously slow down. It needs to stop the machine and continue to work after the oil temperature is reduced. For example, after the above failure of a wy160 hydraulic excavator, the working pressure of each mechanism is obviously low after testing, which is suspected to be caused by the wear of the main safety valve or main pump. Dismantle and inspect the main safety valve first, and there is no abnormality; After disassembling and inspecting the main pump, it was found that the spherical surface of the valve plate was seriously worn. After grinding the valve plate, reassemble and adjust its clearance, and the installed operation is in good condition. As another example, a ZL50 loader moves slowly and weakly. After testing, the pressure of the system is low, and it feels very hot when touching the gear pump. It is suspected that it is caused by internal leakage due to internal wear of the gear pump; After disassembly and inspection, it was found that the clearance between the gear pump side plate and the gear end face was out of tolerance. After replacing the gear pump, the problem was solved.
(8) The ambient temperature is too high
If the ambient temperature is too high and the high load is used for a long time, the oil temperature will be too high.
Preventive measures: avoid working under heavy load for a long time; If the oil temperature is too high, the equipment can run without load for about 10min, and then work after the oil temperature drops down.
