With the gradual rise of temperature, many friends reflect that excavators have a headache, that is, the phenomenon of high temperature of hydraulic oil; if the high temperature of hydraulic oil is not handled in time, in the long run, the internal leakage of hydraulic pumps, main control valves and various working devices will be achieved first, and it must be repaired or replaced in serious cases.
How to determine whether the oil temperature is really high? It can be determined by testing:
Testing the temperature of the hydraulic oil tank, the hydraulic oil in the hydraulic oil tank is returned after the radiator, the normal temperature is 45-55 C; the temperature value of the hydraulic oil in the working device is higher than that of the hydraulic oil tank, which can reach 80 C.
PS: There is no hydraulic oil temperature sensor in the excavator below 40 tons, so it can not be seen on the display screen. It is necessary to test the temperature of the hydraulic oil tank with infrared temperature detector.
If the temperature of hydraulic oil is high, the following symptoms will occur:
The decrease of oil viscosity will cause the system to heat up and form a vicious circle.
High oil temperature will accelerate the oxidation of oil, form gelatinous substances, block the small holes of components, make the hydraulic components fail or jam, unable to work;
Rubber seals, hose aging failure;
Accelerate wear and tear of oil pump and hydraulic valve, even scrap.
If the oil temperature is high, the following aspects can be investigated one by one:
If the hydraulic system is heated due to external reasons, the fault can be eliminated when the hydraulic oil of the shock absorber is released to the standard oil level.
There are two reasons for the high oil level of shock absorber:
The first operator blindly refuels;
Hydraulic pump shaft end oil seal aging, so that hydraulic oil leakage, the latter should be removed to replace the hydraulic pump oil seal.
Point this view: hydraulic pump failure difficult to deal with? Learn to repair!
If the radiator has poor heat dissipation performance, the oil temperature is too high.
The main forms of poor radiation performance of radiators are:
The cooling fan is insufficient.
The exterior heat dissipation fins are deformed or blocked, and the cooling effect is poor.
The pipeline inside the hydraulic oil radiator is blocked.
The fan tape is too loose. Loose and slippery fan tape can also lead to lower fan efficiency and poor cooling effect. Every day, check the tape tightness and wear condition, and adjust or replace new tape if necessary.
In addition to the intuitive judgment, the former two can also be seen from the temperature difference between the upper and lower tubes of the radiator. At this time, the radiator should be cleaned up and the fan belt fastened.
If the internal pipeline of the hydraulic oil radiator is blocked, the pressure difference between the two can be checked by installing pressure gauges in the inlet and outlet pipelines of the radiator. The pressure difference below 0.12 MPa is normal when the oil temperature is about 45 degrees. If it is higher than 0.12 mpa, it indicates that the pipeline is seriously blocked. The upper and lower caps of the radiator should be removed to dredge the pipeline.
If the one-way valve of hydraulic oil return filter core fails and causes overheating of hydraulic oil, check whether the one-way valve of hydraulic system oil return filter core fails or not; if the one-way valve of hydraulic oil return is normally open or the one-way valve is closed, the hydraulic oil does not flow directly back to the hydraulic tank through the cooling of hydraulic oil radiator, which will cause the temperature of hydraulic oil to be too high. This is the case.
The oil return one-way valve is a device that the hydraulic oil eventually returns to the hydraulic oil tank from the main control valve to the working device. There are two devices in this device, one is installed between the main control valve and the hydraulic oil tank, the other is installed between the main control valve and the hydraulic oil radiator.
Check this: Three minutes can solve the high temperature of hydraulic oil! No kidding.
The clearance of hydraulic components is too large.
Excessive clearance of hydraulic components, excessive clearance between valve stem and valve hole, excessive clearance between plunger and cylinder block of pump and motor, excessive clearance between valve plate, excessive wear of seal ring of hydraulic cylinder, excessive clearance between gear end face and tooth top of pilot gear pump will cause serious internal leakage. When the pressure oil leaks, its pressure energy will be transformed into heat energy, resulting in the increase of the temperature of hydraulic oil, leading to the high temperature of hydraulic system.
The pressure adjustment is unreasonable.
If the pressure adjustment of hydraulic system pump, relief valve and safety valve is unreasonable, the temperature of hydraulic system will be too high. If the pressure regulation of the system is too high, the pump will run under the rated pressure, resulting in an increase in oil temperature. The low pressure regulation of the system will make the working mechanism open and unload the relief valve frequently under normal load, which will make most of the hydraulic oil flow back to the tank through the safety valve. This will increase the working power of the hydraulic system and cause the overflow and heat of the hydraulic system.
If the pressure of pilot relief valve is too low, the reversing stem of excavator reversing valve is blocked, resulting in slow movement and high temperature of hydraulic oil. Therefore, according to the different load requirements of excavator, the pressure of safety valve should be checked and adjusted frequently to reach the set value.
20-30T excavator, if the main overflow pressure exceeds 39.7 MPa, it is easy to cause high oil temperature and tubing explosion. Suggestions do not arbitrarily adjust high pressure. The following figure shows the maximum relief valve pressure of Shengang's models:
Point this view: excavator traffic jam, slow action, the main relief valve tube can be'really wide'!
The selection of hydraulic oil is unreasonable; the unreasonable selection of hydraulic oil will result in excessive leakage or flow resistance, resulting in excessive power loss and high temperature of hydraulic oil; therefore, appropriate hydraulic oil should be used as far as possible to reduce friction loss; in summer, slightly higher hydraulic oil should be selected to reduce internal leakage; in winter, slightly higher hydraulic oil should be selected to reduce internal leakage; Low hydraulic oil to reduce pressure loss.
The poor quality of oil and the poor cleanliness of hydraulic oil will result in the blockage of the hydraulic system and the increase of friction resistance of the hydraulic system. This will not only increase the fault and shorten the service life of components, but also lead to the increase of the temperature of the hydraulic system. The poor quality of hydraulic oil will cause air to be mixed into the hydraulic system. Air will escape from the oil to form bubbles in the low-pressure area. When the bubbles move to the high-pressure area, local micro-explosion will occur, and the oil will be compressed sharply to release a large amount of heat.