Three Methods of Regulating the Centrifugal Pumps Flow
2024-05-09 17:30:22
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Centrifugal pumps are widely employed in the chemical industry, water conservation and other industries, and the selection of operating conditions and the analysis of energy consumption are receiving more and more attention. The working capacity of the centrifugal pump contains actual water output, flow rate, head, efficiency, head and shaft power and other factors at a certain moment. Generally speaking, adjusting the flow rate of the pump plays an indispensable role in changing the centrifugal pump's operating point because of changes in production operations and process requirements. In addition to the correct choice of the centrifugal pump during the engineering design stage, the choice of the working point of the centrifugal pump in practice will also have a direct impact on the user's energy consumption and costs. As a result, it is crucial to understand how to adjust the centrifugal pump's working point sensibly.
The centrifugal pump's operating principle is a process of energy conversion and transmission that converts mechanical energy into kinetic and potential energies of the raised liquid by high-speed motor rotation. This feature states that the centrifugal pump's working point is determined by the equilibrium between the energy supply and demand of the pump and the piping system. Valve Throttle
A centrifugal pump's flow rate can be most easily modified by varying the pump outlet valve's opening while the pump's speed (often the rated speed) stays constant. This approach essentially changes the operating point of the pump by adjusting the position of the pipe characteristic curve. When the valve is closed, the pipeline's local resistance rises and the pump's working point shifts to the left, the associated flow decreases. In contrast, there is no flow rate and infinite resistance when the valve is entirely closed.
The ordinate and the pipeline characteristic curves are in line at this point. When the flow control valve is closed, the pump's head characteristics, water supply capacity and pipe resistance features are unaffected. Nevertheless, these characteristics change when the valve is opened. This way can be adjusted freely between a certain maximum flow rate and zero without additional investment and with the features of convenient operation and continuous flow rate. Meanwhile, it has wide application for a variety of situations. However, the throttling adjustment uses the centrifugal pump's excess energy to maintain a specific supply, which is not economically sensible and will also result in a drop in the centrifugal pump's efficiency. Variable Frequency Speed Conversion
The fundamental requirement of centrifugal pump speed control is making the work point deviation from the high-efficiency zone. The water supply capacity, the pipe system's feature, and the head characterize all changes in proportion to variations in the pump's speed. When the speed of the pump changes, the valve opening remains unchanged during the maximum opening.
The head of the frequency conversion speed regulation is smaller than the valve throttling when the needed flow rate is less than the rated flow rate. Consequently, the water supply power required by the frequency conversion speed regulation is also smaller than the valve throttling.
The energy-saving benefit of frequency conversion speed regulation is evident when compared to valve throttling, and the centrifugal pump's work efficiency is higher. Furthermore, by extending the start or stop process by presetting the speed up or down time, frequency conversion speed regulation not only helps to reduce the likelihood of cavitation in centrifugal pumps but also significantly reduces dynamic torque. At the same time, it essentially eliminates the extremely damaging water hammer effect and significantly prolongs the life of the pump and piping system. Severing Impeller
The impeller's diameter determines the pump's pressure head and flow rate when the speed is constant. And the cutting technique can alter the characteristic curve of the centrifugal pump of the same type. According to the cutting law, the corresponding efficiency of the water pump before and after cutting can be regarded as constant if the cutting amount of the impeller is controlled within a specified limit.
The quick and straightforward method of altering the water pump's performance is cutting the impeller. This technique, known as variable diameter adjustment, somewhat resolves the conflict between the water pump's restricted type and specification and the variety of water supply objects, increasing the water pump's usefulness. As everyone knows, cutting the impeller is an irreversible process, so the user must make precise calculations and assess its economic viability before putting it into practice.
In practical applications, various aspects should be considered, in a variety of flow regulation methods in the synthesis of some reliable programmes to ensure the efficient operation of centrifugal pumps.
