Adjustment Method Of Horizontal Multistage Centrifugal Pump

Adjustment method of horizontal multistage centrifugal pump

What are the adjustment methods of horizontal multistage centrifugal pump? The two most commonly used methods are introduced. 1. The simplest way to change the flow of centrifugal pump by valve throttling is to adjust the opening of the valve at the outlet of the pump, while the speed of horizontal multistage centrifugal pump remains unchanged (generally rated speed), its essence is to change the position of the pipeline characteristic curve. What are the adjustment methods of horizontal multistage centrifugal pump? The two most commonly used methods are introduced.

1. Valve throttling

The simplest way to change the flow of centrifugal pump is to adjust the opening of the valve at the outlet of the pump, while the speed of horizontal multistage centrifugal pump remains unchanged (generally rated speed), which is essentially to change the position of the pipeline characteristic curve to change the operating point of the pump. The intersection of pump characteristic curve Q-H and pipeline characteristic curve Q - ∑ h is the limit operating point of the pump when the valve is fully open. When the valve is closed, the local resistance of the pipeline increases, the working point of the water pump moves to the left, and the corresponding flow decreases. When the valve is fully closed, the resistance is infinite and the flow is zero. At this time, the pipeline characteristic curve coincides with the ordinate. It can be seen that when the flow is controlled by turning down the valve, the water supply capacity of the multi-stage centrifugal pump itself will not change, the head characteristics will not change, and the pipe resistance characteristics will change with the change of the valve opening. This method is easy to operate and has continuous flow. It can be adjusted between a certain maximum flow and zero at will without additional investment. It is widely used. However, throttling regulation is to consume the extra energy of the centrifugal pump (shadow part in the figure) to maintain a certain amount of supply, and the efficiency of the centrifugal pump will decrease accordingly, which is not reasonable economically.

2. Frequency control

The deviation of operating point from high efficiency area is the basic condition of speed regulation of water pump. When the speed of multistage centrifugal pump changes, the valve opening remains unchanged (usually the maximum opening), the pipeline 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 variable frequency speed regulation is smaller than the valve throttle, so the water supply power required by variable frequency speed regulation is smaller than the valve throttle. Obviously, compared with valve throttling, the energy-saving effect of frequency control is outstanding, and the working efficiency of horizontal multistage centrifugal pump is higher. In addition, the adoption of frequency control is not only conducive to reducing the possibility of cavitation of centrifugal pump, but also can extend the start-up / shutdown process by preset the speed up / speed down time, so that the dynamic torque is greatly reduced, so as to largely eliminate the destructive water hammer effect, and greatly extend the life of pump and pipeline system.