Maintenance of high oil temperature in the hydraulic system

Maintenance of high oil temperature in the hydraulic system

1, the harm of hydraulic oil temperature is too high ① The viscosity of hydraulic oil, volume efficiency, and hydraulic system efficiency are reduced leakage increases. Even the mechanical equipment can not work usually.

(2) The hydraulic system parts expand because of overheating, destroying the average matching clearance of the relative moving parts, resulting in an increase in friction resistance. The hydraulic valve is easy to stick. At the same time, the lubricating oil film is thin, mechanical wear increases, resulting in the pump, valve, motor, and other precision matching surface due to premature wear and making it invalid or scrapped.

③ Accelerate the aging and deterioration of rubber seals, shorten their life, and even lose their sealing performance so that the hydraulic system leaks seriously.

(4) oil vaporization, water evaporation, easy to make hydraulic components cavitation;

The oil oxidizes to form colloidal deposits, which can easily block the small holes in the oil filter and hydraulic valve so that the hydraulic system can not work usually.

Therefore, the high temperature of hydraulic oil will seriously affect the regular use of the machine, reduce the service life of hydraulic components, and increase the maintenance cost of construction machinery.

2. Reasons for high temperature of hydraulic oil and preventive measures

(1) Improper selection of oil brands, quality and viscosity grade do not meet the requirements, or different grades of hydraulic oil mixed, resulting in too low or too high viscosity index of hydraulic oil.

If the oil viscosity is too high, the power loss increases, and the oil temperature rises.

If the viscosity is too low, the leakage increases, and the oil temperature rises.

Preventive measures: the selection of oil should be recommended by the manufacturer and the machine’s working environment, temperature factors to determine.

For some machines with special requirements, special hydraulic oil should be selected;

When the hydraulic components and system maintenance are inconvenient, choose good performance anti-wear hydraulic oil.

(2) Serious pollution

The construction site environment is terrible, with the increase of the machine working time, the oil is easy to mix with impurities and dirt, the contaminated hydraulic oil into the pump, motor, and valve matching gap, will scratch and damage the precision and roughness of the matching surface, the increase of leakage, oil temperature rise.

Preventive measures are generally in the cumulative work more than 1000 h after the oil change.

When changing oil, pay attention not only to draining the old oil in the tank but also to replace the old oil in the whole system pipeline and working circuit;

When refueling, it is best to use a filter of more than 120 mesh and add enough oil according to the provisions so that the oil has enough circulation cooling conditions.

In case of sudden failure caused by hydraulic oil pollution, it is necessary to filter or replace the hydraulic system oil.

For example, a YZT14G roller hydraulic 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 returned to regular operation.

(3) The oil level in the hydraulic tank is too low

If there is too little oil in the hydraulic tank, the hydraulic system will not have enough flow to remove the heat generated, resulting in high oil temperature.

Preventive measures: in the process of actual operation and maintenance, strictly comply with the provisions of the hydraulic oil level in the operating procedures.

For example, a PC2003 hydraulic excavator, working for some time after the hydraulic oil temperature is too high fault;

Check the hydraulic tank, found that the oil level is much lower than the specified value, due to the excessive lack of oil in the hydraulic system, so that the hydraulic oil circulation is too fast, not fully static heat dissipation, the result of oil temperature rise;

Add enough hydraulic oil according to the provisions. The hydraulic oil temperature will immediately drop to the normal range.

(4) Air is mixed in the hydraulic system

The air in the hydraulic oil will escape from the oil and form bubbles in the low-pressure area. When it moves to the high-pressure zone, these bubbles will be crushed by the high-pressure oil, sharply compressed, and releasing much heat, causing the oil temperature to rise.

Preventive measures: often check the sealing of the inlet pipe interface to prevent air from entering;

At the same time, 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 minor damage to the hose connecting the oil inlet of the hydraulic pump, which caused the oil temperature to be too high. After replacing the hose, the grader ran in good condition.

(5) The oil filter is blocked

When abrasive particles, impurities, and dust pass through the oil filter, they will be absorbed on the filter element of the oil filter, resulting in increased oil absorption resistance and energy consumption, causing the oil temperature to rise.

Preventive measures: clean and replace the oil filter regularly. For the oil filter with a blocked indicator, clean or replace the filter element according to the instructions;

The filter element’s performance, structure, and validity period must meet its use requirements.

For example, a TY220 bulldozer in the operation of the oil temperature alarm continuous alarm, at the same time found that there is a burning smell of oil smoke and oil converter, the oil level is lower in the fuel tank;

The inspection result is that the blockage of the oil suction filter net of the torque converter return pump causes this fault. Because the filter net is covered with sediment, the oil leaked by the torque converter cannot be pumped back to the steering tank in time, which accumulates more and more. The placing resistance of the torque converter increases, the heat generated by friction increases, and finally, the oil temperature rises too fast.

After cleaning the filter, the oil temperature returned to normal.

As another example, a CATD8N crawler bulldozer hydraulic transmission system issued a high-temperature alarm, and transmission parts have abnormal sound;

Disassemble the oil filter and check the filter element, which is found to contain much powdery dirt;

After replacing the filter element, the fault disappeared.

(6) The hydraulic oil cooling circulation system works poorly.

Usually, water-cooled or air-cooled oil coolers are used for mandatory cooling of oil temperature in the hydraulic system.

Water-cooled cooler, because the heat sink is too dirty or water circulation is not smooth, and its heat dissipation coefficient is reduced;

Air-cooled cooler, due to excessive oil pollution and the radiator cap of the cooler being blocked, it is difficult for the fan to heat, resulting in high oil temperature.

Preventive measures: regularly check and maintain the hydraulic oil cooling circulation system, once found fault, must immediately shut down for elimination.

For example, a CPCD60D hydraulic transmission forklift truck, after working for some time, the torque converter driving force is insufficient, the steering wheel is heavy (hydraulic transmission and power steering use a pump together);

After several checks, it was found that the blockage of the ventilation hole of the air-cooled oil cooling device caused the oil temperature to be too high, and the fault was removed after dredging.

Another example is that the cooling machine of a K-702 loader works less than 3h after starting, and the oil temperature alarm indicator light of the torque converter on the instrument panel flashes, indicating that the hydraulic oil temperature is too high.

First, check the amount of oil and oil quality. The result is sufficient oil, good oil quality;

Then check the oil filter, not dirty;

After checking the cooler, it was found that the sludge had blocked part of the more relaxed and oil hole.

After cleaning the cooler, everything is fine.

(7) Parts wear

Gear pump gear and pump body and side plate, piston pump and motor cylinder and valve plate, cylinder hole and plunger, reversing valve stem, and valve body are sealed by the gap. The wear of these components will cause an increase in leakage and oil temperature.

Preventive measures: timely maintenance or replacement of wear and tear parts, according to statistics, under normal circumstances, imported hydraulic pump, motor work after five or six years, domestic products work after two or three years, its wear has been quite severe, must be timely maintenance.

Otherwise, the cooling machine will usually work. Still, after 1-2h, the movement speed of each mechanism of the system will be significantly slower, and it is necessary to stop the machine until the oil temperature is reduced to continue to work.

For example, a WY160 hydraulic excavator in the above fault, after testing the working pressure of the institutions is low, suspected to be caused by the wear of the main safety valve or the main pump.

First, check the main safety valve, no abnormal phenomenon;

After disassembling the main pump, it was found that the spherical surface of the valve plate was seriously worn.

After grinding the valve plate, it is reassembled, its clearance is adjusted, and the machine runs well.

Another example is a ZL50 loader with a slow and weak action. The pressure of the test system is low, and the gear pump feels very hot when touched. It is suspected that the internal wear of the gear pump is caused by internal leakage.

After inspection, it is found that the gap between the gear pump’s side plate and the gear’s end face is out of tolerance.

After replacing the gear pump, the problem was solved.

(8) The ambient temperature is too high

High ambient temperature and a long time of high load use will make the oil temperature too high.

Preventive measures: should avoid a long time continuous heavy load work;

If the oil temperature is too high, the equipment can be turned for about 10min without load and then work after the oil temperature drops.

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