Common Faults of Gear Oil Pumps in Customized Hydraulic Systems And Several Main Methods for Their Elimination

Common Faults of Gear Oil Pumps in Customized Hydraulic Systems and Several Main Methods for Their Elimination

The common faults and troubleshooting methods of hydraulic gear oil pumps during the operation of the hydraulic system mainly consist of the following 6 points:

1.The gear pump is not pumping out any oil?

If during the host debugging process it is found that the gear pump is not delivering oil, first check whether the rotation direction of the gear pump is correct. Gear pumps come in left and right rotation types. If the rotation direction is incorrect, the pressure oil generated by the meshing of the internal gears will cause the oil seal to be damaged and result in oil leakage. Secondly, check whether the oil filter at the inlet end of the gear pump is clogged. This can cause difficulties in oil intake or failure to intake oil, and result in the oil suction hose being flattened.

2. Has the oil seal of the gear pump been blown out?

(1) The rotation direction of the gear pump is incorrect. When the rotation direction of the pump is not correct, the high-pressure oil will directly flow to the oil seal. Since most low-pressure rubber oil seals can only withstand a pressure of 0.5 MPa, this will cause the oil seal to be pushed out.

(2) The bearings of the gear pump are subjected to axial forces. The generation of axial forces is often related to the overly tight fit between the shaft extension end of the gear pump and the coupling sleeve. That is, when installing the pump, it is hammered with a hammer or pulled hard through the installation screws to force the pump shaft to receive a backward axial force. When the pump shaft rotates, this backward axial force will force the wear in the pump to intensify. Since the internal sealing of the gear pump is achieved by the contact between the gear end face and the shaft sleeve end face, when the axial sealing end face is severely worn, an axial gap will occur in the internal axial sealing of the pump. As a result, the high and low pressure oil chambers will communicate, causing the oil seal to be pushed out. This situation occurs frequently in the dump truck industry, mainly due to the non-standard size of the coupling sleeve on the main unit.

(3) The gear pump is subjected to excessive radial force. If the coaxiality during the installation of the gear pump is poor, the radial force exerted on the pump will exceed the limit that the oil seal can withstand, resulting in oil leakage from the oil seal. At the same time, it will also cause damage to the floating bearings inside the pump.

This phenomenon is mostly related to the cleanliness of the hydraulic oil. If the oil is not selected correctly or if the cleanliness of the oil during use fails to meet the standard requirements, it will accelerate the wear inside the pump and cause leakage. Therefore, mineral hydraulic oil containing additives should be selected. This can prevent the oil from oxidizing and generating bubbles. The viscosity standard of the oil is (16~80) × 10-6 m2/s, and the filtration accuracy is: the input oil path is less than 60 Lm. By observing the shaft sleeve and side plate of the faulty gear pump, it was found that if the cleanliness of all the oil is poor, it will cause obvious grooves on the friction surface, while the sealing surface of a normally worn gear pump will only have uniform scratches.

4. The flow does not meet the standard.

The oil filter is too dirty, resulting in insufficient oil intake.

(2) The installation height of the pump is higher than the self-priming height of the pump.

(3) The intake pipe of the gear pump is too thin, resulting in high intake resistance. Generally, the maximum intake flow velocity of the pump is 0.5 to 1.5 meters per second.

(4) Leakage at the oil suction port connector causes insufficient oil intake by the oil pump. By observing whether there are bubbles in the oil tank, one can determine whether the system is leaking.

5. Has the appearance of the gear pump been cracked?

The pressure resistance capacity of the aluminum alloy material gear pump is 38 to 45 MPa. Under the condition that there are no manufacturing defects, the fracture of the gear pump must be caused by the sudden high pressure.

The oil outlet pipeline is blocked by an object, resulting in an unlimited increase in pressure.

(2) The pressure setting of the safety valve is too high, or the opening and closing characteristics of the safety valve are poor and have a lagging response, thus failing to protect the gear pump.

(3) If the system uses multiple directional control valves to regulate the direction, some of these valves may have a negative opening. In such cases, there is a risk of damaging the gear pump due to the pressure build-up at the dead point.

6. Is the hydraulic gear pump overheating?

The system is overloaded, mainly manifested by excessive pressure or rotational speed.

(2) The oil has poor cleanliness, leading to increased internal wear, which results in a decrease in volumetric efficiency. The oil leaks through internal gaps and undergoes throttling, thereby generating heat.

(3) The outlet pipe is too thin and the oil flow rate is too high. The normal oil flow rate is usually between 3 and 8 meters per second.