Created on:2022-04-09 09:33

Causes and preventive measures of high hydraulic oil temperature in mechanical equipment

Causes and preventive measures of high hydraulic oil temperature in mechanical equipment

1. 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.

2. Air is mixed in the 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 parts 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.

3. Serious pollution

The environment of the construction site is bad. 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 gap 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 1000h. 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.

4. Improper selection of oil products

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.

5. The oil filter is 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 oil smoke and burning smell of oil at the torque converter, and the oil level in the steering oil tank is low; The inspection results showed that the fault was caused by the blockage of the oil suction screen of the transformer return oil pump. Because the filter screen was full of sediment, the oil leaked from the torque converter could not be pumped back to the steering oil tank in time. The more it accumulated, the greater the placement resistance of the transformer, the more heat generated by friction, and finally the oil temperature rose too fast; After cleaning the filter screen, the oil temperature returns to normal.

6. 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 rotate without load for about 10min. Wait until the oil temperature drops down before working.

7. Parts are seriously worn

The gear, pump body and side plate of gear pump, cylinder block and port plate of 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, after five or six years of operation of imported hydraulic pumps and motors and two or three years of operation of domestic products, their wear and tear have been quite serious, which 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, and it is necessary to stop the machine and continue to work after the oil temperature is reduced.

For example, after the above failure of a wyl60 hydraulic excavator, the working pressure of each mechanism is obviously low, 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 the hand feels very hot. 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 hydraulic oil cooling and circulating system works poorly

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.

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