The centrifugal pump is composed of many parts. According to the working state of each part during operation, it can be roughly divided into three types: rotating parts, fixed parts and junction parts.
1. impeller
The impeller is the core component of the pump, which allows the water to acquire kinetic energy to create flow. The impeller consists of a blade, a cover plate and a hub, see Figure 1-2. When selecting the impeller material, in addition to considering the mechanical strength under the action of centrifugal force, the wear resistance and corrosion resistance of the material should also be considered. Most of the impellers are currently made of cast iron, cast steel and bronze.
The impeller can be generally divided into a single suction impeller and a double suction impeller. The single suction impeller is shown in Figure l-2. It is unilaterally absorbing water, and the front cover and the rear cover of the impeller are asymmetric. The double suction impeller is water-absorbing on both sides as shown in Figure 1-3, and the impeller cover plate is symmetrical. Generally, the large-flow centrifugal pump mostly uses a double suction impeller.
The impeller can be divided into three types according to the cover condition: closed type, open type and half open type, as shown in Figure 1-4. Centrifugal pumps often use a closed impeller single channel or double channel structure to prevent blockage of debris; sand pumps often use a semi-open and open structure to prevent sand particles from impinging and clogging the impeller.
2. Pump shaft
The pump shaft is used to rotate the pump impeller. Common materials are carbon steel and stainless steel. The pump shaft should have sufficient torsional strength and sufficient stiffness that the deflection does not exceed the allowable value. The impeller and the shaft are coupled by a key. The key is the connecting member of the rotating body. The centrifugal pump generally adopts a flat key. The key can only transmit torque and can not fix the axial position of the impeller. In the large and medium-sized pumps, the axial position of the impeller usually adopts the sleeve and And tighten the nut of the bushing to position it.
3. Pump casing
The water-passing part requires good hydraulic conditions. Pump and pump station design When calculating the impeller operation, the flow rate is gradually increased along the divergent section of the volute. In order to reduce the hydraulic loss, the flow velocity of the centrifugal pump should be made to flow along the volute casing. constant. After the water is discharged from the volute, it flows into the pressure pipe through the conical diffuser. The function of the conical diffuser on the volute is to reduce the speed of the water flow and convert a portion of the flow head into a pressure head. The material selection of the pump casing, in addition to considering the corrosion and wear of the medium to the overcurrent portion, should also provide the casing with sufficient mechanical strength as a pressure vessel.
4. Pump casing
The pump casing is composed of several parts, and the inner cavity forms an impeller working chamber, a suction chamber and a pressurized water chamber. The shape and size of the pump casing depend on the form and size of the impeller and the shape of the suction and pressurized chambers as determined by the hydraulic design. The pump casing mainly has two kinds of end cover type pump casing and middle open type pump casing, and the end cover type pump casing is divided along a radial plane perpendicular to the pump shaft core line to form a pump body.
And the pump cover, mostly used for single-stage pumps, as shown in Figure 1-5(a); the pump casing of the open-type pump casing is divided along the plane passing through the pump shaft line, and is often used for double-supported volute type pumps. Such as horizontal axis single suction double suction pump.
