The impeller of water pump is an important working part of water pump. Its shape, size and processing technology have a decisive impact on the pump performance. The function of the pump impeller is to transfer the energy input by the prime mover to the liquid. Impellers of single-stage single suction centrifugal pump and double suction centrifugal pump are shown in Fig. 1-4 and Fig. 1-5 respectively.

The pump impeller mainly has three structural forms: closed impeller with front and rear cover plates; The impeller with only the rear cover plate is called semi open impeller; The impeller without front and rear cover plates is called open impeller. In addition, the structure of blades can also be divided into cylindrical blades and twisted blades. The structure of pump impeller and blade is shown in Figure 1-6.

Generally, the impeller of closed water pump has 2 to 12 backward curved blades, which has high operating efficiency. For example, the aforementioned single suction and double suction centrifugal pumps use this impeller. The impeller of single-stage single suction centrifugal pump has axial force, so some impellers have balance holes at the root of the blade.

The number of semi open and open impeller blades is small, usually 2~5, and they are mostly used for pumping slurry granular liquid or sewage, such as the impeller of sewage pump.

In the field of sewage discharge, in order to ensure that the medium containing solid particles, fibers and other entanglements is blocked in time, the runner impeller is often used.

The pump impeller material shall have sufficient mechanical strength and certain wear resistance and corrosion resistance. According to the requirements of transmission medium, at present, cast iron, cast steel, stainless steel or bronze impellers are usually used to transport flammable and explosive oils such as oil pump products.