Adjustment method of multistage centrifugal pump for mine
The working principle of the multi-stage centrifugal pump for mining is the same as that of the ground centrifugal pump. When the motor drives the impeller on the shaft to rotate at high speed, the liquid filled in the impeller will be thrown to the impeller from the center of the impeller along the flow path between the blades under the action of centrifugal force. Because the liquid is affected by the blades, the pressure and speed increase at the same time, and it is guided to the next-stage impeller through the flow passage of the guide shell. In this way, it flows through all the impellers and the guide shell one by one to further make the liquid Pressure energy increases. After stacking each impeller step by step, a certain head is obtained and the downhole liquid is lifted to the surface. This is the working principle of the stainless steel multi-stage pump.
What are the adjustment methods of multistage centrifugal pumps used in mines? Two commonly used methods are introduced: 1. Valve throttling
The simple way to change the flow rate of the centrifugal pump is to adjust the opening of the pump outlet valve, while the speed of the multi-stage centrifugal pump remains unchanged (generally the rated speed). The essence is to change the position of the pipeline characteristic curve to change the pump operating point. The intersection of the pump characteristic curve Q-H and the pipeline characteristic curve Q-∑h is the limit operating point of the pump when the valve is fully opened. When the valve is closed, the local resistance of the pipeline increases, the pump operating point moves to the left, and the corresponding flow decreases. When the valve is fully closed, it is equivalent to infinite resistance and zero flow. At this time, the pipeline characteristic curve coincides with the ordinate. It can be seen that when the valve is closed to control the flow, the water supply capacity of the multi-stage centrifugal pump itself is unchanged, the head characteristic is unchanged, and the pipe resistance characteristic will change with the change of the valve opening. This method is easy to operate, continuous in flow, and can be adjusted at will between a certain large flow and zero, and no additional investment is required. It is applicable in a wide range of occasions. But throttling adjustment is to consume the excess energy of the centrifugal pump to maintain a certain supply, and the efficiency of the centrifugal pump will also decrease accordingly, which is not economically reasonable.
2. Frequency conversion speed regulation
The deviation of the operating point from the high-efficiency zone is the basic condition for the pump to adjust the speed. When the rotation speed of the multistage centrifugal pump changes, the valve opening remains the same (usually a large opening), the piping system characteristics remain unchanged, and the water supply capacity and head characteristics change accordingly. In the case that the required flow is less than the rated flow, the head of the frequency conversion speed regulation is smaller than the valve throttling, so the water supply power required for the frequency conversion speed regulation is also smaller than the valve throttling. Obviously, compared with valve throttling, the energy-saving effect of frequency conversion speed regulation is very prominent, and the working efficiency of horizontal multi-stage centrifugal pumps is higher. In addition, the use of frequency conversion speed regulation not only helps to reduce the possibility of cavitation in the centrifugal pump, but also prolongs the start/stop process by presetting the speed-up/speed-down time, so that the dynamic torque is greatly reduced. , Thereby eliminating the destructive water hammer effect to a large extent, greatly extending the life of the pump and piping system.