Centrifugal pump is an extremely widely used pump in industrial production. It has many advantages over other types of pumps:
1. Uniform flow, stable operation, low vibration and high speed
2. Low equipment installation and maintenance costs
3. Wide range of application (including flow rate, head and adaptability to medium properties)
The structure and working principle of centrifugal pump
The centrifugal pump is driven by an electric motor or diesel engine. Before starting the pump, the pump body and the suction line are filled with liquid. When the impeller rotates at high speed, the impeller drives the liquid between the blades to rotate. Due to the centrifugal force, the liquid is thrown from the center of the impeller to the outer edge of the impeller (the flow rate can be increased to 15-25m / s), and the kinetic energy is also increased. When the liquid enters the pump casing, due to the gradual expansion of the flow path in the volute casing, the flow rate of the liquid gradually decreases, and part of the kinetic energy is converted into static pressure energy, so the liquid flows out along the discharge port with a higher pressure. At the same time, a certain vacuum is formed at the center of the impeller because the liquid is thrown out, and the pressure Pa at the liquid level is higher than the center of the impeller. Therefore, the liquid in the suction line enters the pump under the effect of the pressure difference. The impeller rotates continuously, and the liquid is continuously sucked in and out. Because the centrifugal pump can transport liquids, it mainly depends on the action of centrifugal force, so it is called a centrifugal pump
Classification of centrifugal pumps
Classified by the number of working impellers
1. Single-stage pump: there is only one impeller on the pump shaft.
2. Multi-stage pump: there are two or more impellers on the pump shaft.
Classified by working pressure
1. Low pressure pump
2. Medium pressure pump
3. High-pressure pump
According to the impeller water inlet method
1. Single-side water inlet pump: also called single suction pump, that is, there is only one water inlet on the impeller;
2. Double-side water inlet pump: also called double suction pump, that is, there is a water inlet on both sides of the impeller.
Classified by pump shaft position
1. Horizontal pump: The pump shaft is in a horizontal position.
2. Vertical pump: the pump shaft is in a vertical position.
The single-stage single-suction centrifugal pump is reliable, simple in structure, easy to manufacture and process, easy to maintain and maintain, and strong in adaptability. It is a widely used centrifugal pump. One end of the pump is supported by a bearing in the bracket, and the other end of the impeller mounted cantilever extends out of the bracket.
According to the different split positions of the pump body and the pump cover, it can be divided into two structures: front opening type and rear opening type. The advantage of the rear-open pump is that the bracket and the impeller can be taken out as long as the nut of the bracket is loosened during maintenance, and there is no need to disassemble the pump inlet and discharge pipes.
Structural characteristics of double suction centrifugal pump:
1. Beautiful appearance, good stability and easy installation. The motor can be on the left or right as needed. The double-suction centrifugal pump has an open structure of the pump casing. During maintenance, only the pump cover needs to be lifted, and the rotor parts can be removed for maintenance, without disassembling the pipeline, which is very convenient.
2. The shaft seal adopts mechanical seal or packing seal. Can guarantee no leakage for a long time. The impeller seal ring can be replaced after being worn, reducing the operation and maintenance costs.
3. The double suction impeller with optimized design reduces the axial force to the minimum, hydraulic symmetry, no axial force (in theory). Because the double suction impeller has two suction ports, each inlet only needs to take half of the flow, so the flow rate is relatively low, and the impeller is not easy to cavitation.
4. High efficiency, large flow and high head. However, it is bulky and bulky, and is generally not suitable for mobile operations. Mostly used in factories, mines, urban water supply and drainage, etc.
Structural characteristics of multistage centrifugal pump:
The multistage pump uses several impellers to work in series, so the head is high. It is divided into two types: segmented multi-stage centrifugal pump and split-open multi-stage centrifugal pump.
The segmented multistage centrifugal pump has good working performance, large flow and head range, and is widely used in petrochemical production. The pump body is a vertically divided multi-stage structure, which is composed of a first stage, a tail stage and several middle stages, and is connected as a whole with four bolts. A multi-stage impeller is installed in the middle of the pump shaft, and each impeller is equipped with a guide wheel for drainage. Both ends of the shaft are supported by bearings and placed in the bearing body. The shaft sealing device is symmetrically arranged in the first and the last sections of the pump shaft extension. Because the impellers are arranged on the shaft in one direction, each impeller has an axial force, so the total axial force is very large after adding the stages, and the balancing disk must be installed behind the final impeller to parallel the axial force . The segmented multistage centrifugal pump is easy to manufacture, and each section of the pump body can be processed separately, but the structure is more complicated and it is difficult to assemble and disassemble.