The hydraulic system of the excavator is a combination of various hydraulic components which are organically connected in accordance with the driving requirements of the excavator's working device and the various mechanisms. It mainly consists of hydraulic oil tank, main pump, multi-channel valve, pipeline and cylinder and motor for each action. Its function is to use the oil as the working medium, use the hydraulic pump to transform the engine's mechanical energy into the hydraulic energy and carry out the transmission, and then turn the hydraulic energy back into the mechanical energy through the hydraulic cylinder and the hydraulic motor, so as to realize the various actions of the excavator.
Under the normal working condition of the excavator, the oil temperature of the hydraulic system should be below 60 C. (the temperature of the oil pump is 5-10 higher than that of the oil pump). If more, it is called the heating of the hydraulic system.
The heating phenomenon of the hydraulic system and its harm
The heating of hydraulic system is a common phenomenon of mining faults, and it also analyzes and deals with a more complex soft fault.
The fault features are that the work of the excavator cold car is, the various movements are more normal, and when the mechanical work is about an hour, with the increase of the hydraulic oil temperature, the power of the excavator is weak and the movement is slow, especially the digging force is not enough, and the walking turn is difficult.
1. If the heating phenomenon occurs in the hydraulic system, if it can not be handled in time, it will have a very negative impact on the system.
(1) the viscosity of the oil decreases and the leakage increases, which causes the system to heat up and form a vicious circle.
(2) accelerating the oxidation of oil, forming colloidal substances, blocking small holes in components, causing failure or clamping of hydraulic components and unable to work.
(3) the rubber seals, hose aging failure;
(4) wear and tear of oil pumps and hydraulic valves are aggravated or even scrapped.
2. Example analysis of heating system failure of excavator hydraulic system
For such faults, the internal analysis of the external parts of the hydraulic system should generally be addressed first.
Internal reasons are mainly caused by unreasonable design of the system. If the matching between components is unreasonable, the pipeline passages are too small, the elbow is large, the bending radius is small, and the volume of the oil tank is not enough.
Such problems should be fully considered in the design stage, otherwise, the excavator hydraulic system will be incongenitally deficient, and it will be hard to overcome after making 名媛直播.
Heat of the hydraulic system caused by external causes:
When dealing with the heating fault of a hydraulic system of a excavator, it is found that the oil level in the shock absorber box is much higher than that of the plane screw (generally about 1.5L), and the excess oil produces a lot of heat and passes to the hydraulic pump during the rotation of the damping damper, which leads to the system heating.
At this time, after the oil in the shock absorber is discharged to the standard oil level, the trouble can be eliminated.
There are two reasons for the high oil level of the shock absorber, one is the operator blindly refueling, the two is the oil seal aging of the hydraulic pump shaft, the leakage of the hydraulic oil, and the latter should replace the hydraulic pump to replace the oil seal.
Improper selection of hydraulic oil grades or poor oil quality cause excessive oil temperature.
In recent years, many faults have occurred due to the increase of oil temperature in the hydraulic system after selecting oil or pseudo inferior oil whose performance is not up to the standard.
For example, the misuse of oil with high viscosity causes excessive loss of fluid pressure and heat energy, which will cause excessive temperature rise. The misuse of hydraulic oil with low viscosity also causes large leakage in hydraulic pumps and hydraulic components and produces heat; in addition, some inferior oil is poor in viscosity temperature performance, easy to emulsify and produce cavitation erosion. Bubbles and so on will cause partial high temperature in hydraulic oil high pressure and aggravate the wear of components.
Hydraulic oil return check valve failed to cause overheating of hydraulic oil.
From the hydraulic system schematic diagram, it can be found that the one-way valve of the hydraulic system and the hydraulic oil radiator are connected to the outlet of the oil back filter core. The function is to automatically open when the pressure difference of the oil radiator is above 0.185MPa, and the short connection radiator forms the oil return path.
In actual work, because the valve is installed at the bottom of the oil back filter core, it is difficult to check and maintain, in addition, the improper selection of hydraulic oil oil and oil oil quality by individual operator, long-term non oil change and disrepair, so that the oil pollution is serious, causing the valve to die in the constant position (and dismantling the valve without authorization), so the oil return radiator can not be scattered. The heat effect is bound to cause high oil temperature.
When changing hydraulic fluid, check whether the valve is stuck.
The heat dissipation of the radiator is too high to cause high oil temperature.
The main forms of heat sink heat dissipation are: external heat dissipation fin deformation or blockage, poor cooling effect, insufficient cooling fan quantity, and internal pipe blocking of hydraulic oil radiator.
In addition to intuitive judgement, the former two can also learn little about 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 obstruction of the inner pipe of the hydraulic oil radiator, we can check the pressure difference between the two people by installing the pressure gauge in the inlet and outlet of the radiator. The pressure difference between the oil temperature is 45 and about C is in the normal condition. If it is higher than 0.12MPa, the oil pipe is blocked seriously. The upper and lower cover of the radiator should be dismantled and the pipe should be dredged.
System heating caused by improper adjustment of pressure valve in 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.
If the pump plate and cylinder block, slipper, swash plate and plunger cylinder body wear greater, often cause the pump to heat faster. This can be judged by observing the pump's temperature rising rapidly and having the characteristics of noise.
The repair method is to grind and trim the sealing surfaces or replace the parts that cannot be repaired.
Excessive pressure or too low pressure of the overflow valve will also cause the heating of the hydraulic system, such as excessive pressure regulation of the system, which will make the hydraulic pump run under the rated pressure, make the pump overloaded and cause the oil temperature to rise. On the contrary, if the system pressure regulation is too low, the working mechanism will frequently appear under the normal load and open and unload the overflow valve frequently. It causes the overflow of the hydraulic system to overflow.
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