For such faults, the internal analysis of the external hydraulic system should be the first. The internal reason is mainly caused by the unreasonable system design. Such as unreasonable matching between components, too thin pipeline channels, too many elbows, small bending radius, insufficient fuel tank volume and other factors. Such problems should be fully considered in the design stage, otherwise it will lead to congenital deficiencies in the hydraulic system of the excavator, which will be difficult to overcome after the product is made.

(1) Hydraulic system heating caused by external reasons

For example, the engine of Komatsu pc200-5 excavator hydraulic pump is connected through the damping damper in the damping box. When dealing with the heating fault of the hydraulic system of an excavator, it was found that the oil level in the shock absorber box was much higher than that at the observation oil plane screw (generally about 1.5l), and this excessive oil generated a lot of heat and transferred it to the hydraulic pump during the rotation of the shock absorber, causing the system to heat up.

At this time, the fault can be eliminated after the oil in the shock absorber is drained to the standard oil level. There are two reasons for the high oil level of the shock absorber box: one is that the operator refuels blindly; Second, the oil seal at the shaft end of the hydraulic pump is aging, which makes the hydraulic oil leak. The latter should remove the hydraulic pump and replace the oil seal.

(2) Poor heat dissipation performance of radiator causes high oil temperature

The main forms of poor heat dissipation performance of radiator are: deformation or blockage of external heat dissipation fins, poor cooling effect; Insufficient cooling fan; The internal pipes of the hydraulic oil radiator are blocked. In addition to visual judgment, the first two can also be known from the fact that the temperature difference between the upper and lower tubes of the radiator has little change. At this time, the radiator fins should be cleaned and the fan belt should be fastened. To judge the blockage of the internal pipes of the hydraulic oil radiator, a pressure gauge can be installed at the inlet and outlet oil passages of the radiator to check the pressure difference between them. It is normal if the oil temperature is about 45oc and the pressure difference is below 0.12mpa. If it is higher than 0.12mpa, it indicates that the oil pipes are seriously blocked. The upper and lower covers of the radiator should be removed to dredge the pipes.

(3) Hydraulic oil overheating caused by the failure of one-way valve of hydraulic oil return filter element

It can be seen from the schematic diagram of the hydraulic system that the one-way valve of the oil return filter element of the hydraulic system and the hydraulic oil radiator are connected at the outlet of the oil return filter element (refer to the schematic diagram of pc200-5 hydraulic system). Its function is to automatically open when the differential pressure of the oil return radiator is above 0.185 mpa, and short circuit the radiator to form an oil return passage. In actual work, because the valve is installed at the bottom of the oil return filter element, it is difficult to check and maintain. In addition, some operators choose the hydraulic oil improperly, do not change the oil for a long time, and are out of repair for a long time, which causes serious oil pollution, causing the valve to be stuck in the normally open position (others remove the valve without authorization). Therefore, the oil return radiator does not play a role in heat dissipation, which will inevitably lead to high oil temperature. Check whether the valve is stuck every time the hydraulic oil is replaced.

(4) The oil temperature is too high due to improper selection of hydraulic oil brand or poor oil quality

In recent years, there have been many failures caused by the rise of oil temperature in the hydraulic system after the selection of unqualified oil or fake oil. For example, misuse of oil with high viscosity will lead to excessive pressure loss of fluid flow, which will be converted into heat energy and cause excessive temperature rise; Misuse of hydraulic oil with low viscosity will also cause large leakage in the working hydraulic pump and hydraulic components and generate heat; In addition, some low-quality oil, with poor viscosity and temperature performance, is easy to emulsify, produce cavitation, and break bubbles, which will produce local high temperature at the high pressure of hydraulic oil and aggravate the wear of components.

(5) System heating caused by improper adjustment of pressure valve of pump and hydraulic system

As the power source of the hydraulic system, the working condition of the hydraulic pump affects the heating degree of the system. For example, the main pump of the pc200 excavator is a plunger pump. If the matching position between the port plate and the cylinder block, slippers, swashplate and the plunger cylinder block in the pump is severely worn, the hydraulic pump often heats up quickly. This can be judged by observing the characteristics of fast temperature rise and noise of the pump. The repair method is to grind and trim the sealing mating surface or replace the irreparable parts.

Pc200 excavator pilot control pump is a gear pump, whose function is to provide operation control pressure oil for the system and adjust the displacement of the main pump according to the load requirements. If the end face of the internal gear of the pump is severely worn or the tooth clearance is relatively large, and the internal leakage increases, the pump will heat up and affect the normal operation of the main pump.

Too high or too low pressure of the relief valve will also cause heating of the hydraulic system. If the system pressure is adjusted too high, the hydraulic pump will run at a pressure exceeding the rated pressure, overload the pump, and increase the oil temperature; On the contrary, if the system pressure is adjusted too low, the working mechanism will frequently open and unload the relief valve under normal load, resulting in overflow heating of the hydraulic system.