Centrifugal pump flow control of several major ways: the export valve regulation, pump variable speed control and pump string, parallel adjustment. The energy consumption loss of the outlet valve and the pump speed regulation are analyzed by the characteristic curve diagram. The comparison shows that the flow rate of the centrifugal pump is better than that of the outlet valve to regulate the flow rate, and the energy saving efficiency And the size of traffic changes. In the practical application should pay attention to the scope of variable speed adjustment, in order to better use centrifugal pump speed adjustment. Centrifugal pumps are a versatile fluid machinery widely used in chemical industrial systems. It has a wide range of performance to adapt to (including flow, pressure head and the nature of the transport medium adaptability), small size, simple structure, easy operation, low operating costs and many other advantages. Usually, the selected centrifugal pump flow, head pressure may be inconsistent with the requirements of the pipeline, or due to production tasks, process requirements change, this time require the pump flow control, in essence, to change the operating point of the centrifugal pump. Centrifugal pump operating point is determined by the pump characteristic curve and piping system characteristic curve, therefore, to change any of the characteristic curve can achieve the purpose of flow adjustment. At present, the centrifugal pump flow control methods are the main control valve, variable speed control and the pump and the series adjustment. Due to the different principles of various adjustment methods, in addition to their own advantages and disadvantages, the resulting energy loss is not the same, in order to find the best, minimum energy consumption, the most energy-efficient flow regulation, you must fully understand the centrifugal pump flow adjustment The relationship between mode and energy consumption. The main method of pump flow control a, change the pipeline characteristic curve The most simple way to change the centrifugal pump flow is to use the pump outlet valve opening to control, its essence is to change the position of the pipeline characteristic curve to change the pump operating point. b, change the centrifugal pump characteristic curve According to the law of proportionality and cutting law, changing the pump speed, change the pump structure (such as cutting impeller diameter method, etc.) can change the centrifugal pump characteristic curve, so as to adjust the flow (while changing Indenter) the purpose. However, it is less convenient to change the pump structure for an already working pump and to reduce the versatility of the pump by changing the pump configuration, although it is economically convenient to regulate the flow at some point and is rarely used in production. Here only analyze the change of centrifugal pump speed regulation method. When the pump speed is changed to adjust the flow rate from Q1 to Q2, the pump speed (or motor speed) drops from n1 to n2, and the pump speed curve nH is equal to n2 and the pipeline characteristic curve He = H0 + G1Qe2 Curve does not change) to point A3 (Q2, H3), A3 is the new operating point after adjusting the flow through the speed. The adjustment method has the advantages of obvious regulation effect, quickness and safety. The utility model can prolong the service life of the pump and save electric energy. In addition, the operation of reducing the rotational speed can effectively reduce the NPSHr of the centrifugal pump and keep the pump away from the cavitation area and reduce the centrifugal The possibility of pump cavitation [2]. The disadvantage is the need to change the pump speed through the variable frequency technology to change the prime mover (usually the motor) speed, the principle of complex, large investment, and the flow adjustment range. c, the pump string, and even the adjustment mode When a single centrifugal pump can not meet the delivery tasks, you can use the centrifugal pump in parallel or series operation. In parallel with two centrifugal pumps of the same type, although the pressure head changes little, but increases the total delivery flow, the total efficiency of the parallel pump is the same with the efficiency of a single pump; when the centrifugal pump is connected in series, the total pressure head increases, Little change in flow, the total efficiency of tandem pumps with a single pump the same efficiency. Although these methods from the energy analysis point of view is more reasonable, but the operation is very inconvenient, in fact rarely used. Therefore, the actual production or to adjust the valve opening to adjust the flow rate is more common.
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