For such failures, in general, the head should start with internal analysis outside the hydraulic system. The internal reason is mainly caused by unreasonable system design. Such as unreasonable matching between components, excessively narrow pipeline channels, many elbows, small bending radius, insufficient fuel tank capacity and other factors.
<1) Hydraulic system heating caused by external reasons
For example, the engine of Volvo EC210B excavator hydraulic pump is connected through the shock absorber in the shock absorber box. When dealing with the heat failure of the hydraulic system of an excavator, it was found that the oil level in the shock absorber box greatly exceeded the observation oil level screw (generally about 1.5L), and these excessive oils accompanied the rotation process of the shock absorber damper In the process, a large amount of heat is generated and transferred to the hydraulic pump, causing the system to generate heat.
At this time, after draining the shock tank oil to the standard oil level, the fault can be eliminated. There are two reasons for the excessively high oil level in the shock absorber box. One is that the operator blindly refuels. The other is the aging of the oil seal at the shaft end of the hydraulic pump, which causes the hydraulic oil to leak. The latter should remove the bolt to replace the oil seal.
<2) Poor heat dissipation performance of radiator causes excessive oil temperature
The main forms of poor heat dissipation performance of the radiator are: deformation or clogging of the external heat dissipation fins, poor cooling effect; insufficient cooling fan volume, and blockage of the internal pipeline of the hydraulic oil radiator. In addition to the intuitive judgment of the first two, it can also be seen from the fact that the temperature difference between the upper and lower tubes of the radiator does not change much. At this time, the heat sink should be cleaned and the fan belt should be fastened. To judge the blockage of the internal pipeline of the hydraulic oil radiator, you can check the pressure difference between the two by installing a pressure gauge at the inlet and outlet of the radiator. The oil temperature is about 450C. The pressure difference is below 0.12MPa, which is normal. At 0.12MPa, it indicates that the oil pipe is seriously blocked, and the upper and lower covers of the radiator should be removed to clear the pipeline.
<3) Hydraulic oil return filter element check valve failure causes hydraulic oil to overheat
It can be known from the hydraulic system schematic diagram that the hydraulic system return oil filter check valve and the hydraulic oil radiator are connected to the return oil filter outlet (see Volvo EC210B hydraulic system schematic diagram). Its function is to automatically open when the pressure difference of the oil return radiator is above 0.185MPa, 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, and individual operators improper selection of hydraulic oil quality, long-term non-oil replacement and long-term disrepair, etc., causing serious oil pollution, resulting in the valve card He died in the normally open position (and some dismantled the valve without authorization), so the oil return radiator could not dissipate heat, which inevitably caused the oil temperature to be too high. Every time the hydraulic oil is changed, check whether the valve is stuck.
