The working principle of the multi-stage centrifugal pump is the same as that of the ground centrifugal pump. When the motor drives the impeller on the shaft to rotate at high speed, the liquid filled in the impeller will be thrown from the center of the impeller along the flow path between the blades to the periphery of the impeller under the action of centrifugal force. Due to the action of the blades, the liquid increases the pressure and speed at the same time, and is guided to the next-stage impeller through the flow passage of the guide shell. In this way, it flows through all the impellers and the guide shell one by one, further increasing the pressure energy of the liquid increase. After stacking each impeller step by step, a certain head is obtained and the downhole liquid is lifted to the ground. This is the working principle of the stainless steel multi-stage pump.
Main features of multistage centrifugal pump:
1. Vertical structure, the inlet and outlet flanges are on the same center line, the structure is compact, the area is small, and the installation is convenient.
2. The vertical structure pump adopts the mechanical seal of the container structure, which makes the installation and maintenance operation safer and more convenient, and ensures the reliability of the seal.
3. The motor shaft of the multi-stage centrifugal pump is directly connected with the pump shaft through a coupling.
4. The horizontal pump is equipped with an extended shaft motor, which has a simple structure and is easy to install and maintain.
5. The flow parts are all made of stainless steel, which does not pollute the medium and ensures long service life and beautiful appearance.
6. Low noise and small vibration. With standardized design, it has good versatility.
What are the adjustment methods of multistage centrifugal pumps? Two commonly used methods are introduced:

1. Valve throttling

The simple way to change the flow rate of the centrifugal pump is to adjust the opening of the pump outlet valve, while the speed of the multi-stage centrifugal pump remains unchanged (generally the rated speed). The essence is to change the position of the pipeline characteristic curve to change the pump operating point. The intersection of the pump characteristic curve Q-H and the pipeline characteristic curve Q-∑h is the limit operating point of the pump when the valve is fully opened. When the valve is closed, the local resistance of the pipeline increases, the pump operating point moves to the left, and the corresponding flow decreases. When the valve is fully closed, it is equivalent to infinite resistance and zero flow. At this time, the pipeline characteristic curve coincides with the ordinate. It can be seen that when the valve is closed to control the flow, the water supply capacity of the multi-stage centrifugal pump itself remains unchanged, the head characteristics remain unchanged, and the pipe resistance characteristics will change with the change of the valve opening. This method is easy to operate, continuous in flow, and can be adjusted at will between a certain large flow and zero, without additional investment, and has a wide range of applications. However, throttling adjustment is to consume the excess energy of the centrifugal pump to maintain a certain supply, and the efficiency of the centrifugal pump will also decrease accordingly, which is not economically reasonable.

2. Frequency conversion speed regulation

The deviation of the operating point from the high-efficiency zone is the basic condition for the speed of the pump. When the speed of the multistage centrifugal pump changes, the valve opening remains unchanged (usually a large opening), the piping system characteristics remain unchanged, and the water supply capacity and head characteristics change accordingly. When the required flow is less than the rated flow, the head of the frequency conversion speed regulation is smaller than the valve throttling, so the water supply power required for the frequency conversion speed regulation is also smaller than the valve throttling. Obviously, compared with valve throttling, the energy-saving effect of frequency conversion speed regulation is very prominent, and the working efficiency of horizontal multi-stage centrifugal pumps is higher. In addition, the use of frequency conversion speed regulation not only helps to reduce the possibility of cavitation in the centrifugal pump, but also prolongs the start/stop process by presetting the speed up/down time, so that the dynamic torque is greatly reduced. , Thereby eliminating the destructive water hammer effect to a large extent, greatly extending the life of the pump and piping system.

The multi-stage centrifugal pump adopts the high-efficiency and energy-saving hydraulic model recommended by the country. It has the advantages of high efficiency and energy saving, wide performance range, safe and stable operation, low noise, long life, convenient installation and maintenance, etc.; by changing the pump material, sealing form and increasing cooling The system can transport hot water, oil, corrosive and abrasive media, etc. Different multi-stage centrifugal pump manufacturers produce different models of multi-stage centrifugal pumps. Multi-stage centrifugal pumps combine two or more pumps with the same function together. The structure of the fluid channel is reflected in the media pressure relief port and the first stage. The inlet of the second stage is connected, and the medium pressure relief port of the second stage is connected to the inlet of the third stage. Such a series-connected mechanism forms a multi-stage centrifugal pump. The significance of the multistage centrifugal pump is to increase the set pressure.