1. The pump does not produce oil
If the gear pump does not come to the oil during commissioning, first check that the gear pump is rotating in the correct direction. The gear pump has left and right hand rotation. If the direction of rotation is wrong, the pressure oil formed by the difference in volume generated by the internal gear meshing will cause the oil seal to be damaged and leak oil. Secondly, it is checked whether the oil filter at the oil inlet end of the gear pump is clogged, which may cause difficulty in oil absorption or oil absorption, and the phenomenon that the oil suction hose is sucked up.
2. The oil seal is punched out
(1) The gear pump is not in the correct direction. When the rotation direction of the pump is not correct, the high-pressure oil will directly pass to the oil seal. Since the low-pressure skeleton oil seal can only withstand a pressure of 0.5 MPa at most, the oil seal will be flushed out.
(2) The gear pump bearing is subjected to axial force. The axial force is often related to the over-tightening of the gear pump shaft extension end and the coupling sleeve, that is, the pump is hammered by a hammer or hardened by a mounting screw to receive a backward axial force when the pump is installed. This backward axial force will force the wear in the pump to increase as the shaft rotates. Since the gear pump is internally sealed by the gear end face and the end face of the bushing, when the axial sealing end face is seriously worn, the internal axial seal of the pump will generate a certain gap, resulting in communication between the high and low pressure oil chambers and the oil seal flushing. . This situation has appeared in the dump truck industry, mainly due to the irregular size of the coupling sleeve on the main engine.
(3) The gear pump is subjected to excessive radial force. If the coaxiality of the gear pump is not good, the radial force of the pump will exceed the bearing limit of the oil seal, which will cause the oil seal to leak oil. At the same time, it will also cause damage to the floating bearing inside the pump.
3. Can't build pressure or pressure enough
Most of this phenomenon is related to the cleanliness of the hydraulic oil. If the oil is not selected correctly or the cleanliness of the oil in use does not meet the standard requirements, it will accelerate the internal wear of the pump and cause it to leak. Therefore, mineral hydraulic oil containing additives should be used to prevent oxidation and bubble generation. The viscosity standard of the oil is (16-80)×10-6m2/s. The filtration precision is: the input oil passage is less than 60цm. By observing the bushings and side plates of the faulty gear pump, it is found that if the cleanliness of all the oils will cause obvious groove marks on the surface of the friction pair, only the uniform surface marks will be generated on the sealing surface of the normally worn gear pump.
4. Traffic does not meet the standard
(1) The oil inlet filter is too dirty and the oil absorption is insufficient.
(2) The installation height of the pump is higher than the self-priming height of the pump.
(3) The oil suction pipe of the gear pump is too fine to cause large oil absorption resistance. Generally, the maximum oil absorption flow rate is 0.5 to 1.5 m/s.
(4) Leakage of the suction port joint causes the oil pump to absorb insufficient oil. You can judge whether the system is leaking by observing whether there is air bubble in the fuel tank.
5. Gear pump burst
The pressure resistance of the aluminum alloy gear pump is 38 to 45 MPa. Under the premise of no manufacturing defects, the gear pump explosion is definitely caused by the instantaneous high pressure.
(1) The oil pipeline is blocked by foreign matter, causing the pressure to rise indefinitely.
(2) The pressure of the safety valve is adjusted too high, or the opening and closing characteristics of the safety valve are poor, and the reaction is delayed, so that the gear pump is not protected.
(3) If the system uses multiple directional valves to control the direction, some multi-way valves may be negative openings, which will cause the gear pump to be damaged due to the dead point boost.
6. fever
(1) The system is overloaded, mainly in the case of excessive pressure or speed.
(2) The cleanliness of the oil is poor, the internal wear is intensified, the volumetric efficiency is lowered, and the oil leaks from the internal gap to generate heat.
(3) The oil discharge pipe is too thin, the oil flow rate is too high, and the general oil flow rate is 3-8 m/s.