Heating of hydraulic system is not only a common fault phenomenon of excavator, but also a complex fault to analyze and deal with. Under normal working conditions of excavator, the oil temperature of hydraulic system shall be below the specified temperature. If it exceeds more, it is called hydraulic system heating. The following will roughly describe several reasons for the heating of the hydraulic system.
1. The oil temperature is too high due to poor heat dissipation performance of radiator
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 pipe of hydraulic oil radiator is blocked.
In addition to visual judgment, the first two can also be known from the small change in the temperature difference between the upper and lower tubes of the radiator. 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, install a pressure gauge at the inlet and outlet of the radiator to check the pressure difference between them. It is normal that the pressure difference is below the error range under the specified oil temperature. If it is higher than the error range, it indicates that the oil pipe is seriously blocked. Remove the upper and lower covers of the radiator and dredge the pipeline.
2. Hydraulic oil overheating caused by failure of check valve of hydraulic oil return filter element
The check valve of the return oil filter element of the hydraulic system is connected with the hydraulic oil radiator and is connected to the outlet of the return oil filter element. Its function is to automatically open when the pressure difference of the oil return radiator is above the specified value, and short-circuit the radiator to form an oil return path.
In actual work, because the valve is installed at the bottom of the oil return filter element, it is difficult to check and maintain, coupled with the improper selection of hydraulic oil quality by individual operators, long-term non oil change and disrepair, the oil pollution is serious, resulting in the valve stuck in the normally open position, or the valve is removed without authorization, so the oil return radiator does not play the role of heat dissipation, which is bound to cause the oil temperature to be too high. Check whether the valve is stuck every time you change the hydraulic oil.
3. 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 oil with non-conforming performance or fake and shoddy oil. For example, misuse of oil with high viscosity will cause excessive loss of fluid flow pressure and convert it into heat energy, which will cause too high 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 inferior oils have poor viscosity temperature performance, are easy to emulsify and produce cavitation, break bubbles, etc., which will produce local high temperature under high pressure of hydraulic oil and aggravate the wear of components.
4. System heating caused by improper adjustment of pump and hydraulic system pressure valve
As the power source of the hydraulic system, the working condition of the hydraulic pump affects the heating degree of the system. If the main pump is a plunger pump, if the matching position between the port plate in the pump and the cylinder block, sliding shoes, swashplate and plunger cylinder block is worn greatly, it often causes the hydraulic pump to heat quickly. This can be judged by observing the fast temperature rise of the pump and the characteristics of noise. The repair method is to grind and trim the relevant sealing mating surface or replace the parts that cannot be repaired.
Too high or too low pressure of the overflow valve will also cause heating of the hydraulic system. If the system pressure is adjusted too high, the hydraulic pump will run under the rated pressure, overload the pump and increase the oil temperature; On the contrary, if the system pressure is adjusted too low, the overflow valve will be opened and unloaded frequently under normal load, resulting in overflow heating of the hydraulic system.
