Adjustment method of pipeline centrifugal pump
The adjustment methods of pipeline centrifugal pumps mainly include the following:
1. Outlet throttling adjustment
Method: Control the flow rate by adjusting the opening of the pump outlet valve. When the valve is closed, the local resistance of the pipeline increases, the operating point of the pump moves to the left, and the corresponding flow rate decreases. When the valve is fully closed, it is equivalent to infinite resistance and zero flow rate.
Advantages: Easy operation, continuous flow rate, can be adjusted between a certain maximum flow rate and zero at will, without additional investment, and wide application.
Disadvantages: Throttling adjustment will cause energy loss and waste, because it is necessary to consume the excess energy of the centrifugal pump to maintain a certain supply, and the efficiency of the centrifugal pump will decrease accordingly.
2. Variable speed adjustment
Method: Keep the valve opening unchanged (usually the maximum opening) and adjust the flow rate by changing the speed of the pump. This can be achieved by changing the speed of the prime mover (usually an electric motor) through frequency conversion technology.
Advantages: Compared with valve throttling, variable frequency speed regulation has outstanding energy-saving effects and higher working efficiency of centrifugal pumps. At the same time, it is also beneficial to reduce the possibility of cavitation in centrifugal pumps and extend the life of water pumps and pipeline systems.
Disadvantages: The principle is complicated, the investment is large, and the flow adjustment range is relatively small.
3. Cutting impeller adjustment
Method: The characteristic curve of the pump is changed by cutting the impeller to achieve the purpose of adjusting the flow. This method is usually used for clean water pumps, and the cutting amount needs to be controlled within a certain limit to ensure that the efficiency remains unchanged.
Advantages: To a certain extent, it solves the contradiction between the limited types and specifications of water pumps and the diversity of water supply object requirements, and expands the scope of use of water pumps.
Disadvantages: Cutting the impeller is an irreversible process, and it changes the structure of the pump and reduces the versatility of the pump. Therefore, users must implement it after precise calculation and weighing the economic rationality.
4. Parallel or series adjustment
Parallel adjustment: When a single centrifugal pump cannot meet the delivery task, two or more pumps can be used in parallel. After parallel connection, the total flow rate increases, but the head does not change much. The total efficiency of the parallel pump is the same as the efficiency of a single pump.
Series adjustment: When the head needs to be increased, two centrifugal pumps can be operated in series. After series connection, the total head increases, but the flow rate does not change much. The total efficiency of the series pump and the single pump is also the same.
Note: When operating in parallel or series, attention must be paid to the performance matching of the pump and the flatness of the pipeline characteristic curve to ensure stable operation of the system.
