How to deal with insufficient flow of gear oil pump?

As the core power component of the hydraulic system, insufficient flow output of the gear oil pump can directly lead to slow or even failure of the actuator. This type of malfunction is usually accompanied by a decrease in system pressure, abnormal increase in oil temperature, and abnormal noise, and requires a systematic investigation based on equipment operating data and mechanical structural characteristics.

1、 Oil and suction system inspection

Abnormal oil viscosity is the main factor causing flow attenuation. When the viscosity of the oil exceeds the ISOVG46 standard, the oil film thickness of the gear mesh clearance increases, resulting in a decrease in volumetric rate. For example, not replacing winter hydraulic oil when the ambient temperature is below 5 ℃ can cause the viscosity to surge to 2.3 times the normal value. At this point, it is necessary to use a fuel tank with heating function or replace it with low-temperature hydraulic oil, and ensure that the oil cleanliness meets NAS6 level standards.

Oil suction system faults often manifest as oil mixed with air. When there is a leakage point in the oil suction pipeline, air will enter the pump body with the oil to form air pockets. In a typical case, the aging of the O-ring at the oil suction pipe joint of a certain device resulted in an air mixing rate of 12%, causing the actual displacement of the pump to decrease by 37%. When handling, it is necessary to mainly check the degree of blockage of the oil suction filter (if the pressure difference exceeds 0.03MPa, it needs to be cleaned), whether the inner diameter of the oil suction pipe meets the requirements of the pump body (recommended to be 1.5 times the pump diameter), and whether the oil tank level is below the low stability line (should be higher than the pump oil suction port by more than 150mm).

2、 Mechanical clearance and sealing system maintenance

The mechanical clearance deviation of gear pumps is the main cause of flow loss. Under normal working conditions, the axial clearance between the gear end face and the pump cover should be controlled at 0.02-0.05mm, and the radial clearance should not exceed 0.13mm. When used for more than 5000 hours, the wear of the driving gear shaft sleeve may reach 0.08mm, resulting in an increase of 2.1L/min in internal leakage. At this time, a coordinate measuring instrument should be used to detect the parallelism of the gear axis (with an error of less than 0.01mm/100mm), and the worn parts should be repaired: the end face wear should be restored to flatness using grinding technology, and the gear wear should be repaired with chrome plating or replaced with new parts.

Sealing system failure often accompanies oil leakage. After 2000 hours of continuous operation, the rubber skeleton oil seal at the shaft sealing part showed lip wear of up to 0.3mm, resulting in a leakage rate of 0.5L/min. During maintenance, the main checks should be on whether the installation direction of the shaft seal is correct (with the spring side facing the medium), whether the pressure in the sealing chamber exceeds 0.3MPa (high-pressure sealing should be used instead), and whether anaerobic adhesive is applied to the joint surface of the pump cover for sealing. For cast iron pump bodies, it is necessary to detect casting defects such as sand holes and perform infiltration treatment if necessary.

3、 Optimization of Drive System and Regulating Mechanism

Abnormal driving system will directly affect the speed output of the pump. When the actual speed of the motor is 10% lower than the rated value, the theoretical flow rate of the pump will decrease accordingly. It is necessary to use a laser tachometer to detect the motor speed and check: the coaxiality of the coupling (radial deviation should be

Malfunctions in the regulating mechanism often lead to uncontrolled flow output. When the set pressure of the control valve is lower than the system demand, some oil will flow back through the overflow port. In a typical malfunction, a device experienced a 40% decrease in system flow due to the fatigue of the stabilizing valve spring, causing the opening pressure to drop from 25MPa to 18MPa. At this point, it is necessary to conduct dynamic characteristic testing of the control valve (response time should be less than 0.2 seconds), usability verification of the pressure compensator (pressure fluctuation should be less than ± 0.5 MPa), and calibration of the flow control valve opening (linearity error should be less than 3%). For the proportional adjustment system, it is also necessary to test the resistance of the electromagnetic coil (with an error of less than 5%).

4、 System optimization and preventive maintenance

Establishing a traffic monitoring system is the key to preventing potential failures. By installing turbine flow meters at the inlet and outlet of the pump, the rate of flow change can be monitored in real time (normal fluctuations should be less than 2%/h). When the flow rate drops by more than 10%, a three-layer warning mechanism needs to be activated: the first layer warning (checking oil parameters), the second layer warning (detecting mechanical clearances), and the third layer warning (disassembling and repairing the pump body). At the same time, equipment health records should be established to record operating time, maintenance records, replacement parts and other information, providing data support for predictive maintenance.

Standardized procedures need to be developed for preventive maintenance. It is recommended to perform oil sampling and testing (moisture content should be less than 0.1%), filter differential pressure testing (replace when clogged), and seal appearance inspection (no hardening or cracks) every 1000 hours of operation. Implement every 5000 hours of operation: disassembly inspection of the pump body (measuring clearances between various parts), non-destructive testing of the gear pair (magnetic particle inspection for deep cracks), and dynamic balance testing (residual unbalance should be less than 5g · mm). For critical equipment, vibration sensors can be installed to monitor the bearing status (vibration velocity value should be less than 4.5mm/s).

The solution to the problem of insufficient flow in gear oil pumps requires the comprehensive application of knowledge from multiple disciplines such as mechanics, hydraulics, and electrical engineering. By establishing fault tree analysis method, the insufficient flow can be decomposed into sub modules such as oil system, mechanical system, and drive system, which can accurately locate the fault source. In maintenance practice, the following should be followed:; Easy before difficult, external before internal; The principle is to prioritize identifying quickly repairable fault points and then conduct in-depth analysis of complex mechanical problems. At the same time, attention should be paid to spare parts management, and the inventory turnover period of key seals, gear pairs, and other components should not exceed 12 months to avoid a decrease in maintenance quality due to aging spare parts.