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The Main Way Of Multi-stage Centrifugal Pump Flow Regulation

Released on Sep. 01, 2018

Multi-stage Centrifugal Pump are widely used in mining, water conservancy, chemical and other industries, and their selection of working conditions and analysis of energy consumption are also receiving increasing attention. The so-called operating point refers to the actual water output, head, shaft power, efficiency, and vacuum height of the pump unit at a certain moment. It indicates the working capacity of the pump.

The working principle of the multistage centrifugal pump is to convert the mechanical energy of the high speed rotation of the motor into the kinetic energy and potential energy of the lifted liquid, which is a process of energy transfer and conversion. According to this feature, the operating point of the centrifugal pump is based on the balance between the energy supply and demand of the pump and the pipeline system. As long as one of the conditions changes, the operating point will shift.

Here are some ways to analyze and compare:

1 valve throttling

The easiest way to change the flow rate of a multistage centrifugal pump is to adjust the opening of the pump outlet valve, while the pump speed remains the same. The essence is to change the position of the pipeline characteristic curve to change the operating point of the pump. When the valve is closed, the local resistance of the pipe increases, the pump operating point moves to the left, and the corresponding flow rate decreases. When the valve is fully closed, it is equivalent to an infinite resistance and the flow rate is zero. At this time, the pipeline characteristic curve coincides with the ordinate. This method is easy to operate, continuous flow, and can be adjusted freely between a certain maximum flow rate and zero, and no additional investment is required. However, the throttling adjustment is to consume the excess energy of the multi-stage centrifugal pump to maintain a certain supply amount, and the efficiency of the centrifugal pump will also decrease, which is not economically reasonable.

2 frequency control

When the required flow rate is less than the rated flow rate, the head of the variable frequency speed regulation is smaller than the throttle of the valve, so the water supply power required for the frequency conversion speed regulation is also smaller than the throttle of the valve. Obviously, compared with valve throttling, the energy-saving effect of frequency conversion speed regulation is very prominent, and the Horizontal Multi-stage Centrifugal Pump works more efficiently. In fact, the frequency conversion speed regulation also has limitations. In addition to the large investment and high maintenance cost, when the pump speed is too large, the efficiency will drop, which exceeds the pump proportional law range, and it is impossible to adjust the speed without limit.

3 cutting impeller

When the speed is constant, the pressure head and flow rate of the pump are related to the diameter of the impeller. For the same type of pump, the cutting curve can be used to change the characteristic curve of the pump. The cutting law is based on a large number of inductive test data. It is considered that if the cutting amount of the impeller is controlled within a certain limit, the corresponding efficiency of the pump before and after cutting can be regarded as constant. Cutting the impeller is a simple and easy way to change the performance of the pump. It solves the contradiction between the limitation of the type and specification of the pump and the diversity of the requirements of the water supply object to a certain extent, and expands the scope of use of the pump. Of course, the cutting impeller is an irreversible process and the user must perform accurate calculations and measure economic rationality before implementation.

4 Conclusion

Although the valve throttling will cause energy loss and waste, it is still a fast and easy flow regulation method in some simple occasions; the frequency conversion speed regulation is more and more favored by users because of its good energy saving effect and high degree of automation; Cutting impellers are generally used for clean water pumps. Due to changes in the structure of the pump, the versatility is poor. The series and parallel connection of pumps are only suitable for the case where a single pump cannot meet the transportation task, and the number of series or parallel is too uneconomical. In practical applications, it should be considered from many aspects, and the best solution is integrated among various flow regulation methods to ensure efficient operation of the centrifugal pump.

Horizontal Multi-stage Centrifugal Pump

Boye Dinghe Road Urban Sector,Baoding,Hebei 071300, China
+86 312 8306 113
hbtdby@aliyun.com
+86 312 8327 015
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