The gear oil pump has failed – how to fix it?

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During installation and use, gear pumps can encounter various problems. Here are 6 such situations summarized, which I will explain to you one by one: 1. No oil output: If it is found that the gear pump does not produce oil during the testing of the main unit, first check whether the rotation direction of the gear pump is correct. Gear pumps come in left-hand and right-hand rotation versions; if the rotation direction is incorrect, the pressure oil generated by the volume difference resulting from the meshing of the internal gears will cause the oil seal to be damaged and lead to oil leakage. Secondly, check whether the filter at the oil inlet end of the gear pump is clogged, as this can cause difficulties in drawing in oil or even prevent any oil from being drawn in, leading to the suction hose becoming flattened. 　 2. Oil seal is ejected: (1) The rotation direction of the gear pump is incorrect. When the rotation direction of the pump is incorrect, high-pressure oil will flow directly to the oil seal. Since a standard low-pressure skeleton oil seal can generally withstand only a pressure of 0.5 MPa, this will cause the oil seal to be pushed out. 　 (2) The gear pump bearings are subjected to axial forces. The generation of axial force is often related to an overly tight fit between the shaft end of the gear pump and the coupling sleeve; that is, during installation, the pump is struck with a hammer or pulled forcefully using mounting screws, which exerts a backward axial force on the pump shaft. As the pump shaft rotates, this backward axial force leads to increased wear inside the pump. Since the internal part of a gear pump is sealed by the contact between the gear end faces and the shaft sleeve end faces, when these axial sealing surfaces become severely worn, a gap will form in the internal axial seal, which in turn allows the high-pressure and low-pressure oil chambers to communicate with each other, causing the oil seal to be pushed out. This situation occurs frequently in the dump truck industry, mainly due to non-standard dimensions of the coupling sleeves on the main engine. (3) The gear pump is subjected to excessive radial force. If the coaxiality of the gear pump is poor during installation, the radial forces acting on the pump can exceed the bearing capacity of the oil seal, resulting in oil leakage from the seal. At the same time, it can also cause damage to the floating bearings inside the pump. 　 3. Inability to generate sufficient pressure or insufficient pressure. This phenomenon is mostly related to the cleanliness of the hydraulic oil; improper selection of the oil or failure to maintain the required level of cleanliness during use can both accelerate wear inside the pump, leading to leakage. Therefore, mineral hydraulic oil containing additives should be used to prevent oxidation and the formation of bubbles in the oil. The viscosity standard for the oil is (16–80)×10-6 m2/s, and the filtration precision is: less than 60 цm for the incoming oil flow. By examining the shaft sleeves and side plates of the faulty gear pump, it was found that poor cleanliness of the oil will cause noticeable grooves on the surfaces of the friction pairs, whereas normal wear on the sealing surfaces of a gear pump results only in uniform surface marks. 4. Flow rate does not meet the standard. (1) The oil inlet filter is too dirty, resulting in insufficient oil absorption. (2) The installation height of the pump is higher than its self-priming height. (3) The suction pipe of the gear pump is too thin, resulting in high suction resistance. Generally, the maximum oil absorption flow rate is 0.5 to 1.5 m/s. (4) Air leakage at the oil suction port connector results in insufficient oil absorption by the oil pump. It is possible to determine whether the system is leaking by checking for bubbles in the fuel tank. 5. Gear pump explosion: The pressure resistance of gear pumps ranges from 0.6 to 2.5 MPa; assuming there are no manufacturing defects, an explosion of the gear pump is definitely caused by sudden high pressure. (1) Foreign objects have blocked the oil outlet pipe, causing the pressure to rise indefinitely. 　 (2) The pressure setting of the safety valve is too high, or the opening and closing characteristics of the safety valve are poor with a delayed response, failing to provide protection for the gear pump. 　 (3) If the system uses multiple directional control valves to regulate direction, some of these valves may have negative openings, which can lead to gear pumps being damaged due to pressure buildup at the dead points. 6. Fever (1) System overload, mainly manifested as excessive pressure or speed. 　 (2) Poor oil cleanliness leads to increased internal wear, which reduces the volumetric efficiency; oil leaks from the internal gaps and undergoes throttling, generating heat. (3) The oil outlet pipe is too narrow, resulting in a high oil flow rate; generally, the oil flow rate is 3–8 m/s.