Common problems and causes analysis of gear pumps

As a core component in hydraulic systems, the operational stability of gear pumps directly affects equipment performance. In practical applications, gear pumps often encounter problems such as abnormal flow, pressure fluctuations, leaks, noise, and overheating, which conceal complex fault mechanisms.

1、 Abnormal traffic issue

Insufficient or no oil output from the gear pump is a typical fault. Insufficient flow may be caused by blockage of the oil inlet filter, resulting in increased oil suction resistance, or pressure loss caused by a too small diameter of the oil suction pipe. For example, when the inner diameter of the oil suction pipe is smaller than the requirements of the pump body, the decrease in oil flow rate will directly lead to insufficient oil suction. In addition, the installation height of the pump body exceeding the self-priming capacity range, the sealing failure of the suction port joint causing air leakage, and the high viscosity of the oil resulting in poor fluidity will all exacerbate flow attenuation. If the pump body does not discharge any oil, it is necessary to first check whether the motor rotation direction is consistent with the direction indicated on the pump body, and at the same time confirm whether the oil tank level is below the low stability line.

2、 Pressure system malfunction

The failure or fluctuation of pressure establishment is another common problem of gear pumps. When the cleanliness of hydraulic oil does not meet the standard, the particles in the oil will accelerate the wear of the gear pair, causing the end face clearance to expand and leading to internal leakage. For example, when the filtering accuracy of the input oil circuit is less than 60 μ m, metal debris may scratch the gear end face and pump cover sealing surface. Abnormal pressure setting of the control valve is also an important cause. If the opening pressure of the control valve is too high or the opening and closing are delayed, the system pressure will exceed the pressure limit of the pump body. In a certain case, the aluminum alloy gear pump was not afraid of pressure threshold at 38MPa. However, due to the failure of the stabilizing valve, the pressure suddenly rose to 45MPa, which later caused the pump body to explode.

3、 Leakage and seal failure

Oil leakage is a stubborn fault of gear pumps, mainly occurring at the joint surfaces of shaft seals and pump covers. The failure of the shaft seal may be caused by aging of the seal, detachment of the skeleton spring, or scratches on the sealing surface during installation. When the clearance between the pump cover and the sealing ring is too large, high-pressure oil will leak out along the clearance. A maintenance record shows that when the gap between the pump cover and the sealing ring exceeds 0.05mm, the leakage rate will increase exponentially. In addition, structural damages such as pump body cracks and casting defects can also cause oil leakage, and such faults require non-destructive testing to confirm the degree of damage.

4、 Abnormal vibration and noise

Abnormal noise is often accompanied by severe vibrations, and its root cause can be traced back to multiple mechanical components. When the pump body and pump cover are not equipped with paper pads, direct metal contact will produce high-frequency impact sound. When the gear meshing accuracy is insufficient or the axis is not parallel, the meshing impact force will cause low-frequency buzzing. A certain test data shows that when the gear axis deviates by 0.1mm, the vibration acceleration can reach 5g or more. In addition, coupling misalignment exceeding 0.01mm, small inlet pipe diameter leading to cavitation, and foreign objects entering the pump body can all exacerbate the noise level.

5、 Overheating and rate decay

Overheating of the pump body is usually related to system overload, oil contamination, and flow channel defects. When the system pressure exceeds 20% of the rated value, the shear heat generated by oil leakage will cause the oil temperature to rise by more than 15 ℃. When the diameter of the oil outlet pipe is too small and the flow velocity exceeds 8m/s, the pressure loss along the way will be converted into thermal energy. In a certain case, after the outlet pipe diameter was reduced to 80% of the standard value, the pump body temperature increased from 60 ℃ to 90 ℃ within 30 minutes. In addition, mechanical failures such as insufficient bearing lubrication and failure of gear end face clearance compensation can also exacerbate temperature rise through frictional heating.

The fault diagnosis of gear pumps requires the establishment of systematic thinking, which not only focuses on external factors such as oil quality and installation parameters, but also deeply analyzes internal mechanisms such as gear meshing characteristics and sealing structures. By regularly checking the cleanliness of the oil, monitoring the operating temperature, calibrating the control valve pressure and other preventive maintenance measures, the occurrence rate of failures can be significantly reduced. For equipment that has already malfunctioned, it is necessary to combine vibration spectrum analysis, ferrography detection, and other methods to accurately locate the source of the fault and develop a repair plan.