The frequent failures of gear pumps are mainly due to small flow, no oil absorption, insufficient pressure, high noise, oil leakage, overheating, abnormal operation of the oil pump or seizure, etc. The causes and solutions for the failure are introduced as follows.
1. Reasons for gear pumps not sucking oil or low flow rate:
(1) The oil suction position is too high or the oil level is insufficient.
(2) The radial clearance between the inner tooth tip circle of the gear pump and the hole in the pump body is too large, and the clearance between the side of the gear and the end faces of the front and rear cover plates is too large.
(3) The gear pump is not tightly sealed.
(4) The oil filter is blocked.
(5) The oil temperature is too high. Solution:
(1) Replenish oil in the oil tank and lower the oil suction position.
(2) Replace the pump body.
(3) Replace the sealing element and tighten the connecting piece.
(4) Clean or replace the filter element of the oil filter.
(5) Add a cooler in the oil tank or adopt air cooling.
2. Causes of insufficient pressure:
(1) The radial clearance and axial clearance of the gear pump are too large, and the impact of the end face clearance is greater.
(2) The tooth body has cracks or leaks.
(3) The oil viscosity is too high or the oil temperature is too high.
(4) The power of the motor does not match the gear pump.
(5) The oil filter is blocked.
(6) The pressure adjustment of the relief valve is too low or malfunctions. Solution:
(1) Replace the pump body.
(2) If there is leakage, add a paper pad between the pump body and the pump cover, and tighten the connecting parts. If the pump body is cracked, the pump body should be replaced.
(3) No. 20 engine oil is suitable for working at a temperature of 10 to 50 degrees. If the temperature is too high, a cooling device should be installed.
(4) Choose matching motors.
(5) Clean the oil filter.
(6) Readjust the pressure or replace the overflow valve.
3. Causes of excessive vibration and noise:
(1) Gear error or two gear axes are not parallel.
(2) The diameter of the oil inlet pipe of the gear pump is too small.
(3) The oil filter is blocked or the speed is too high.
(4) There is no paper pad on both sides of the pump body and the cover, resulting in hard object impact. The pump body and the pump cover are not sealed vertically, and air is sucked in when rotating.
(5) The motor and the oil pump shaft are not concentric. Solution:
(1) Replace the main precision gear to ensure that the axes of the two gears are parallel.
(2) Replace the oil inlet pipe with a larger diameter.
(3) Clean the oil filter or reduce the speed.
(4) A paper pad is added between the pump body and the pump cover, and the parallelism between the grinding pump body and the pump cover does not exceed 0.005mm.
(5) Adjust the coaxiality of the pump body and the motor, and the error should not exceed 0.01mm.
4. Causes of oil leakage:
(1) The pump cover and the sealing ring fit too loosely.
(2) The spring of the oil seal frame falls off.
(3) The sealing surface of the shaft is scratched. Solution:
(1) Adjust the gap between the pump cover and the sealing ring.
(2) Replace the seals.
(3) Re-grind the sealing surface.
5. Causes of abnormal operation or seizure of the oil pump:
(1) The axial clearance and radial clearance of the pump body are too small.
(2) Needle roller rotation is not flexible.
(3) The concentricity between the cover plate and the shaft is not enough.
(4) The pressure valve fails.
(5) The concentricity of the pump and motor coupling is insufficient.
(6) There are impurities in the pump. Solution:
(1) Adjust the axial or radial clearance.
(2) Replace the movable needle roller bearings.
(3) Replace the cover plate to make it concentric with the shaft.
(4) Replace the spring, remove the dirt in the small hole of the valve body or replace the slide valve.
(5) Adjust the concentricity of the pump shaft and the motor coupling so that it does not exceed 0.01mm.
(6) Use fine silk screen to filter engine oil to remove dirt.
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