The large centrifugal pump works by the centrifugal force generated by the water caused by the rotation of the impeller. Before starting the centrifugal pump, the pump casing and the suction pipe must be filled with water, and then the motor is started, so that the pump shaft drives the impeller and the water to rotate at a high speed. The flow channel of the shell flows into the pressurized water line of the pump. At the center of the impeller of the pump, since the water is thrown out under the action of centrifugal force, a vacuum is formed, and the water in the suction pool is pressed into the pump shell under the action of atmospheric pressure, and the impeller rotates continuously, so that the water is in the impeller. Under the action of continuous inflow and outflow, the purpose of transporting water is achieved.

The large centrifugal pump is composed of many parts. According to the working state of each part, it can be roughly divided into three types: rotating parts, fixed parts and transfer parts.
 1. impeller
The impeller is the core component of the pump, which enables the water to gain kinetic energy to generate flow. The impeller consists of blades, cover plate and hub.
 2. pump shaft
The pump shaft is used to rotate the pump impeller. Common materials are carbon steel and stainless steel. The pump shaft shall have sufficient torsional strength and sufficient rigidity, and its deflection shall not exceed the allowable value. The impeller and shaft are keyed together. The key is the connecting piece between the rotating bodies. In large centrifugal pumps, flat keys are generally used. This key can only transmit torque but cannot fix the axial position of the impeller. In large and medium-sized pumps, the axial position of the impeller usually uses a bushing. And tighten the nut of the shaft sleeve to locate.
3. pump casing
The water passing part requires good hydraulic conditions. When the impeller is working in the design and calculation of the pump and pump station, the flow rate increases gradually along the gradually expanding section of the volute. In order to reduce the hydraulic loss, in the design of the large centrifugal pump, the velocity of the water flowing along the gradually expanding section of the volute should be a constant. After the water is discharged from the volute, it flows into the pressure water pipe through the conical diffusion pipe. The function of the conical diffuser on the volute is to reduce the speed of the water flow, so that a part of the flow head is converted into a pressure head. The material selection of the pump casing should not only consider the corrosion and wear of the medium to the overflow part, but also make the casing have sufficient mechanical strength as a pressure-resistant container.
4. pump casing
The pump casing is composed of several parts, and its inner cavity forms an impeller working chamber, a water suction chamber and a pressurized water chamber. The shape and size of the pump casing depends on the structure and size of the impeller and the shape and size of the suction chamber and the pressure water chamber determined by the hydraulic design. There are mainly two types of pump casings: end cover type pump casing and middle open type pump casing. The end cover type pump casing is divided along the radial plane perpendicular to the pump axis to form a pump body and a pump cover, which are mostly used for single-stage pump casings. Pump.
 5. pump seat
There are flange holes on the pump base for fixing with the bottom plate or foundation. The manufacturer of the large centrifugal pump tells you that there is a drain hole at the bottom of the pump casing, so that the pump can be stopped.