The technical performance of hydraulic pump usually refers to the pressure and flow of the pump. Wear in use, oil pollution, etc. will lead to volumetric efficiency, pressure drop and flow reduction. It is manifested that the actuators (hydraulic cylinders and motors) in the system move slowly and work weakly, and at the same time, the hydraulic pump produces noise, leakage and heat until it does not turn (stuck) and other phenomena.
1. The pump is running normally, the execution is weak
Under this condition, measure the pressure value of each actuator with a pressure gauge, check the working condition of the main safety valve, and compare the standard pressure value of the system to quickly determine whether the pump output pressure and flow rate are normal.
2. The pump vibrates with noise
1. Forced vibration caused by power input and fixed connection
(1) Insufficient engine power and unstable operation.
(2) The spline of the pump input shaft is worn, the transmission connection disk and the vibration reduction connection disk are damaged, and the cross joint of the transmission shaft is worn.
(3) The fixing bolt of the pump is loose due to long-term operation, and the bracket is not fixed firmly.
(4) The coaxiality of the pump and the engine is too poor, which increases the additional load caused by the eccentric operation of the pump.
2. Vibration and noise of the pump itself
(1) The oil pump sucks a lot of air and causes vibration and noise due to lack of oil, trachoma at the low-pressure inlet of the pump casing, and poor sealing of the pipeline at the low-pressure suction port.
(2) The oil inlet filter is clogged or the rubber of the oil inlet pipe is aged.
(3) Due to the wear of the pump's valve plate or oil inlet valve, and the decrease in sealing performance, the amount of oil entering the plunger cavity is insufficient, causing the pump flow to be permanent and vibrate.
(4) The oil temperature is low in winter, the viscosity of the oil is too large, and the oil absorption is insufficient to generate noise.
(5) The pump inlet valve seat is loose, the inlet spring is damaged, the outlet valve seat is loose, the outlet valve spring is broken or the elastic force is insufficient, which will make it difficult to seal the high-pressure chamber of the pump, causing some piston oil pumps to be weak and uneven flow. Cause the pump to vibrate.
(6) The screw holes of the high and low pressure valve seats on the valve valve disc are poorly processed or the thread is deformed and the size becomes seven after long-term use, or the iron filings are not cleaned thoroughly, resulting in the valve face after the new valve is loaded. Balanced, causing the valve to vibrate without sealing.
(7) The exhaust hole at the high-pressure outlet valve cannot exhaust the air in the plunger cavity, and the exhaust space is blocked to cause vibration.
(8) The plunger and cylinder are scratched, the cylinder parts are abraded and cracked, etc., causing vibration.
(9) On the crankshaft radial piston pump, the gap between the connecting rod and the crankshaft is excessive, and the gap between the connecting rod and the connecting rod pin seat hole is too large, which will cause shock vibration.
(10 radial piston pump cylinder size and position tolerances are excessively poor and cause vibration.
(11 The poor positioning accuracy of the pump shaft support bearing, the gap between the inner and outer rings of the bearing installation does not meet the design requirements, and the unreasonable axial positioning adjustment will cause the pump to generate vibration and noise.
(12) The index error of the 7 plunger holes on the rotating cylinder of the inclined shaft pump is too large, and the dimensional accuracy of each hole is low, which will cause vibration and noise during high-speed operation.
3. Vibration load caused by load (load), etc. and unreasonable speed regulation of control elements
If the pressure limit valve and the back pressure valve are imbalanced, it will cause system vibration: the speed limit valve or the back pressure valve fails to cause vibration: the pilot system pump failure causes the suction to cause the main pump to vibrate: the oil pipe of the oil pump is too Long and loosely fixed, causing mutual impact.
3. Leakage and fever
1. Low pressure leakage
Also known as external leakage, the fault is intuitive and easy to eliminate.
(1) The oil seal of the shaft end of the pump shaft is damaged and the rubber is aging.
(2) The process of the pump shaft is unreasonable during the assembly process, and the sealing surface of the oil seal is pulled.
(3) The seal ring or gasket at the end cap of the inlet pipe is damaged, and the fixing bolt is loose.
2. High pressure leakage
is also called internal leakage. The reasons are:
(1) In valve-type pumps, the high and low pressure valves are not sealed. In a pump with a valve disc, there is wear or serious strain between the valve disc and the cylinder.
(2) In valve-type pumps, due to improper tightening of the cylinder and valve body studs during manufacturing or repair installation, the valve body is twisted, the O-ring is installed incorrectly, or the quality is poor, which will cause the cylinder and valve body The sealing surface of the leaker. In a pump with a valve plate, the central spring is damaged or the elasticity is reduced, and the axial gap is too large, which will cause the seal between the cylinder and the valve plate to be lost.
(3) The wear gap between the plunger and the cylinder is too large, causing the normal seal oil film layer to break and leak. High-pressure leakage and heat generation are related. Excessive gap will inevitably cause leakage. Through the throttling effect of the gap, changes in pressure and flow rate are converted into heat energy and released. As the service life of the hydraulic pump increases, the internal leakage reduces the volumetric efficiency of the pump and the plunger wears. The increase in mechanical resistance decreases the efficiency, increases the resistance and reduces the pressure, that is, the oil temperature of the hydraulic pump increases and the system is weak. 3. Slow movements, these phenomena mostly occur in the late stage of pump operation. When the natural wear and tear damages the sealing surface, the gap increases sharply, the leakage amount increases greatly, the heat generation is serious, and it cannot operate normally, the excavator must be repaired or the pump assembly must be replaced.
4. The influence of hydraulic oil
Hydraulic oil is a carrier for transmitting pressure energy. With the increase of working time, the impact of the environment and the degree of pollution of normal oil 名媛直播, various performance indicators will decline. The effects of moisture, air, cleaning agent abrasives, acids, oxides, etc., will cause residual sludge in the rubber parts, reducing the lubricating performance of the hydraulic oil and attenuating the viscosity-temperature index. The discoloration and viscosity changes of hydraulic oil have the greatest impact on the pump.
Full hydraulic excavator hydraulic system failure, hydraulic pump failure frequency is the highest, and oil pollution caused by failures accounted for about 70% to 75% of the total number of excavator hydraulic system failures. The contaminated oil must be completely replaced to ensure the normal operation of the hydraulic excavator.
