1.What Is Oil Trapping?
Oil trapping occurs when a small volume of hydraulic fluid becomes sealed between meshing gear teeth during rotation.
As the gears continue to rotate, this trapped oil has no direct flow path to the inlet or outlet.
2.How Does Oil Trapping Occur in Gear Pumps?
*Two gear teeth come into full engagement
*The enclosed oil volume becomes isolated
*Continued rotation causes the trapped volume to shrink or expand
This leads to abnormal pressure changes inside the pump chamber.
3.Main Causes of Oil Trapping
1.Complete Tooth Meshing：
When gear teeth mesh fully without a pressure relief path, oil is trapped between them.
2.Fixed Pump Geometry：
Traditional external gear pumps have fixed tooth profiles and chamber volumes, making oil trapping unavoidable.
3.Lack of Relief Grooves：
Without specially designed relief grooves or pressure-equalizing channels, trapped oil cannot escape.
4.Effects of Oil Trapping
①.Pressure Spikes：Rapid compression of trapped oil causes local high pressure.
②.Increased Noise and Vibration：Sudden pressure release generates impact noise and vibration.
③.Accelerated Wear：High internal stress damages gear teeth, bushings, and pump housing.
④.Reduced Efficiency：Energy is lost due to pressure fluctuation and internal friction.