“Gear pump oil leakage” means that the hydraulic oil breaks down the skeleton oil seal and overflows. This phenomenon is common. Oil leakage in gear pumps seriously affects the normal operation of the loader, the reliability of the gear pump and environmental pollution. In order to facilitate the solution of the problem, the causes and control methods of oil leakage failure of the gear pump oil seal are analyzed.
1. Influence of parts manufacturing quality
(1) Oil seal quality. For example, if the geometry of the oil seal lip is unqualified, the tightening spring is too loose, etc., it will cause air leakage in the air tightness test and oil leakage after the gear pump is installed in the main engine. At this time, the oil seal should be replaced and the material and geometry should be inspected (the quality gap between domestic oil seals and foreign advanced oil seals is large).
(2) Processing and assembly of gear pumps. If there are problems with the gear pump processing and assembly, causing the gear shaft rotation center to be out of concentricity with the front cover stop, it will cause the oil seal to wear eccentrically. At this time, the symmetry and displacement of the front cover bearing hole to the pin hole should be checked, and the coaxiality of the skeleton oil seal to the bearing hole should be checked.
(3)Sealing ring material and processing quality. If this problem exists, the sealing ring will be cracked and scratched, causing the secondary seal to be loose or even ineffective. Pressure oil will enter the skeleton oil seal (low pressure channel), causing oil leakage in the oil seal. At this time, the sealing ring material and processing quality should be checked.
(4) Processing quality of variable speed pump. Feedback from the OEM shows that the gear pump oil seal assembled with the variable speed pump has a serious oil leakage problem. Therefore, the processing quality of the variable speed pump also has a greater impact on oil leakage. The transmission pump is installed on the output shaft of the gearbox, and the gear pump is installed on the output shaft of the transmission through the positioning of the transmission pump stop. If the runout (verticality) of the transmission pump stop end facing the gear rotation center is out of tolerance (verticality), it will also The rotation center of the gear shaft and the center of the oil seal do not coincide, which affects the sealing. During the processing and trial production of the variable speed pump, the coaxiality of the rotation center to the stop and the runout of the stop end face should be checked.
(5) The oil return channel of the front cover between the skeleton oil seal and the sealing ring of the CBG gear pump is not smooth, causing the pressure here to increase, thereby breaking down the skeleton oil seal. After improvements here, the oil leakage phenomenon of the pump has been significantly improved.
2. Influence of the installation quality of gear pump and main engine
(1) The installation requirement of the gear pump and the main engine requires that the coaxiality is less than 0.05. Usually the working pump is installed on the variable speed pump, and the variable speed pump is installed on the gearbox. If the runout of the end face of the gearbox or speed pump at the center of rotation of the spline shaft is out of tolerance, a cumulative error will be formed, causing the gear pump to bear radial force under high-speed rotation, causing oil leakage in the oil seal.
(2) Whether the installation clearance between components is reasonable. The external stop of the gear pump and the internal stop of the transmission pump, as well as the external splines of the gear pump and the internal splines of the gearbox spline shaft. Whether the clearance between the two is reasonable will have an impact on the oil leakage of the gear pump. Because the inner and outer splines belong to the positioning part, the fitting clearance should not be too large; the inner and outer splines belong to the transmission part, and the fitting clearance should not be too small to eliminate interference.
(3) Oil leakage in the gear pump is also related to its spline roller key. Since the effective contact length between the gear pump shaft’s extended splines and the gearbox output shaft’s internal splines is short, and the gear pump transmits a large torque when working, its splines bear high torque and may suffer from extrusion wear or even rolling, generating huge heat. , resulting in burns and aging of the rubber lip of the skeleton oil seal, resulting in oil leakage. It is recommended that the main engine manufacturer should check the strength of the gear pump shaft’s extended splines when selecting a gear pump to ensure sufficient effective contact length.
3. Influence of hydraulic oil
(1) The cleanliness of hydraulic oil is extremely poor, and the pollution particles are large. Sand and welding slag in various hydraulic control valves and pipelines are also one of the causes of pollution. Because the gap between the shaft diameter of the gear shaft and the inner hole of the seal ring is very small, larger solid particles in the oil enter the gap, causing wear and scratching of the inner hole of the seal ring or rotating with the shaft, causing the pressure oil of the secondary seal to enter the low pressure area ( Skeleton oil seal), causing oil seal breakdown. At this time, the anti-wear hydraulic oil should be filtered or replaced with new one.
(2) After the viscosity of the hydraulic oil decreases and deteriorates, the oil becomes thinner. Under the high-pressure state of the gear pump, the leakage through the secondary seal gap increases. Since there is no time to return the oil, the pressure in the low-pressure area increases and the oil seal is broken down. It is recommended to test the oil regularly and use anti-wear hydraulic oil.
(3) When the main engine works under heavy load for too long and the oil level in the fuel tank is low, the oil temperature can rise to 100°C, causing the oil to become thinner and the skeleton oil seal lip to age, thus causing oil leakage; the fuel tank fluid should be checked regularly surface height to avoid excessive oil temperature.
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Post time: Apr-16-2024