Why Gear Pumps Fail When Handling Fluids with Particles

Generally, gear pumps are suitable for conveying liquid media that do not contain solid particles.

A gear pump is a type of positive displacement pump. It works by using a pair of meshing gears; the rotation of these gears creates volume changes that draw in and discharge liquid. Since the gears rotate, there must be clearances between the gears and the corresponding housing. Precisely because of these clearances, during the operation of the gear pump, a portion of the liquid always leaks back from the high-pressure outlet zone to the low-pressure inlet zone. This is the pump's internal leakage. To minimize this internal leakage, the clearances between the gears and the housing are kept very small. Typically, the lower the viscosity of the conveyed liquid and the greater the pressure difference between the inlet and outlet, the smaller these clearances need to be.

For example, our company's NP series micro gear pumps can achieve a pressure differential of up to 20 Bar (2 MPa) when handling low-viscosity liquids (such as water or other solvents). The minimum internal clearance within the pump is controlled to about 0.02mm. This means particles larger than this size can cause the pump to seize (lock up).

Furthermore, the gears are in meshing contact during operation; that is, the gear tooth surfaces contact each other. Additionally, there is frictional contact movement between the bearings and the shaft. If particles enter these areas, they can cause significant wear, reducing the pump's service life.