First, the basic structure of the centrifugal pump There are many types of centrifugal pumps, Figure 1-1 shows the single-stage single-suction centrifugal pump basic structure, including the volute-shaped pump housing, pump shaft, impeller, suction pipe, pressure Water pipe, bottom valve, control valve, irrigation funnel and pump seat. Second, the centrifugal pump works Centrifugal pump is the use of centrifugal impeller rotation to produce water to work. Before starting the pump, the pump housing and suction pipe must be filled with water, and then start the motor so that the pump shaft can drive the impeller and water to do high-speed rotation. Under the centrifugal force, the water is thrown to the outer edge of the impeller, Of the flow into the pump pressure water pipe. Pump impeller center, due to the role of centrifugal force in the water after the formation of a vacuum thrown, the water sucked in the pool under the action of atmospheric pressure is pressed into the pump housing, the impeller by constantly rotating, making water in the impeller Under the action of continuous inflow and outflow, reaching the purpose of transporting water. Third, the main centrifugal pump parts Centrifugal pump is composed of many parts, according to the work of the various parts of the working conditions, can be roughly divided into three types: rotating parts, fixed parts and handover components. 1. Impeller The impeller is the core part of the pump, it allows water to obtain kinetic energy and flow. Impeller by the blade, cover and wheel composition, shown in Figure l-2. Select impeller material, in addition to considering the centrifugal force under the action of mechanical strength, but also consider the material wear and corrosion resistance. Most impellers are made of cast iron, cast steel and bronze. Impeller generally can be divided into single suction impeller and double suction impeller two. Single-suction impeller shown in Figure l-2, it is unilateral water, impeller front cover and rear cover was asymmetric. Double-suction impeller as shown in Figure 1-3 on both sides of the suction, impeller cover is symmetrical, the majority of large-flow centrifugal pumps are mostly double-suction impeller. Figure 1 2 single-suction impeller Figure l-3 double-suction impeller 1 a front cover; 2 a rear cover; 3 a blade; 4 leaf slots; 1 a suction port; Suction port; 6 a hub; a pump shaft 4 a hub; 5 a shaft hole impeller according to its cover can be divided into closed, open and semi-open three, as shown in Figure l-4. Sewage pumps are often closed impeller single channel or dual channel structure to prevent debris clogging; sand pump is often used semi-open and open structure to prevent sand on the impeller wear and clogging. 2. Pump Shaft The pump shaft is used to rotate the pump impeller. Common materials are carbon steel and stainless steel. Pump shaft should have sufficient torsional strength and sufficient rigidity, the deflection does not exceed the allowable value. Impeller and shaft key to link. The key is the connection between the rotating body, the centrifugal pump is generally flat key, this key can only transmit the torque and can not be fixed axial position of the impeller, large and medium-sized pump in the axial position of the impeller is usually used sleeve and And tight sleeve nut to locate. 3. The pump housing part of its water requirements have good hydraulic conditions. Pump and pumping station design calculation Impeller work, along the involute expansion section of the volute, the flow is gradually increased, in order to reduce the hydraulic loss, the pump design should be along the volute along the diverging section of the flow velocity is a constant . After the water is discharged from the volute, it flows into the compressed water pipe through the conical diffuser. The role of the conical diffuser tube on the volute is to reduce the velocity of the water stream and convert a portion of the velocity head to a pressure head. The material of the pump housing should be chosen such that, in addition to corrosion and wear of the medium to the overcurrent portion, the housing should have adequate mechanical strength as a pressure vessel. 4. Pump housing consists of a number of components of the pump casing, which formed the impeller chamber, water chamber and water pressure chamber. The shape and size of the pump housing depend on the structure and size of the impeller as well as the dimensions of the suction and pressure chambers defined by the hydraulic design. There are two main types of pump shell: open-ended pump shell and open-shell pump shell. The end-shell pump shell is divided along the radial plane vertical to the axis of the pump to form a pump body and a pump cover. Pump, as shown in Figure 1-5 (a); open pump casing along the plane through the axis of the pump casing is divided, commonly used in double-support volute pump, such as horizontal axis single suction double suction pump Wait.
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