Self-priming centrifugal pump parts are: inhalation chamber, impeller, pressure chamber three parts. The impeller chamber is the heart of the pump and the heart of the flow component. Pump through the impeller on the liquid work, to increase its energy. Impeller according to the direction of the liquid is divided into three categories: (1) Radial impeller (centrifugal impeller) Liquid is along the axis of the vertical direction out of the impeller. (2) Diagonal impeller (Francis impeller) The liquid flows out of the impeller in a direction inclined to the axis. (3) Axial impeller The direction of liquid flow parallel to the axis. Impeller by inhalation is divided into two categories: (1) single-suction impeller (ie impeller from the side of the inhalation of liquid). (2) double suction impeller (ie impeller suction fluid from both sides). Impeller by cover form is divided into three categories: (1) closed impeller. (2) open impeller. (3) Semi-open impeller. One closed impeller is widely used, the aforementioned single suction impeller double suction impeller belongs to this form.