Horizontal multi - stage centrifugal pump regulation of what are the most commonly used two ways to introduce.
1. Throttle valve
The simplest way to change the flow of the centrifugal pump is to adjust the opening of the pump outlet valve, while the horizontal multi-stage centrifugal pump speed remains unchanged (generally rated speed), its essence is to change the position of the characteristics of the pipeline curve to change the working point of the pump.The intersection point of pump characteristic curve q-H and pipeline characteristic curve Q-∑ H is the limit working condition point of the pump when the valve is fully open.When the valve is turned off, the local resistance of the pipe increases and the working point of the pump moves to the left, thus reducing the corresponding flow.When the valve is completely closed, it is equivalent to infinite resistance and zero flow. At this time, the pipeline characteristic curve coincides with the vertical coordinate.Thus it can be seen that when the flow is controlled by turning off the small valve, the water supply capacity of the multistage centrifugal pump itself remains unchanged, the lift characteristic remains unchanged, and the pipe resistance characteristic will change with the change of the valve opening.This method is simple to operate, continuous flow, can be adjusted at will between a certain maximum flow and zero, and no additional investment, applicable to a wide range of occasions.But throttling regulation is to consume the excess energy of the centrifugal pump to maintain a certain amount of supply, the efficiency of the centrifugal pump will also decline, economic is not reasonable.
2. Variable frequency speed regulation
The deviation of the working point from the high efficiency zone is the basic condition for the pump to adjust speed.When the speed of the multistage centrifugal pump changes, the valve opening remains unchanged (usually the maximum opening), the piping system characteristics remain unchanged, and the water supply capacity and lift characteristics change accordingly.In the case of the required flow less than the rated flow, the head of variable frequency speed regulation is smaller than the valve throttling, so the need for variable frequency speed regulation of water supply power is smaller than the valve throttling.Obviously, compared with valve throttling, frequency conversion speed saving effect is very prominent, horizontal multi-stage centrifugal pump work efficiency is higher.In addition, using variable frequency speed regulation, is not only beneficial to reduce the risk of deeloping cavitation in centrifugal pump, and can be controlled by the acc/dec time to extend the preset starting/stopping process, thus greatly reducing the dynamic torque, thus eliminated very greatly and destructive water hammer effect, greatly extend the life span of the pump and piping system.