The impeller of the centrifugal pump is to transfer the energy of the original motivation through centrifugal force to the liquid in the pump, which increases the speed and pressure of the liquid. This causes the pump to drain out and the liquid in the inlet pipe is sucked in. The materials used in impeller are: cast iron HT20~ 40, HT25~ 47, cast steel ZG15, ZG25, cast copper ZGCuR, stainless steel 1Cr13, 2Cr13, 1Cr18Ni9Ti, and aluminum cast iron.

Closed impeller of centrifugal pump consists of wheel disk, blade and front and rear cover plate. This impeller is good for the flow of gas, and the wheel cover is equipped with a gas seal to reduce the leakage loss, so the efficiency is higher than the previous two rounds. In addition, the impeller and the side clearance of the enclosure are not as strict as the semi-open impeller, which can be properly enlarged and easy to remove and assemble when overhauling.

The closed impeller centrifugal pump is more efficient but difficult to manufacture. It is widely used in pipeline pumps. It is suitable for conveying water, solution and other non-granulated clean liquids. The closed impeller with a cover plate can improve the flow of liquid and improve the efficiency of the pump. It is suitable for conveying clear liquid, and the general centrifugal cleaning water pump adopts this kind. But the impeller clearance is narrow to go through impurities, especially the impeller of small centrifugal pump, it requires that the medium is clear and viscosity cannot be large, and it cannot contain fibrous material.