Analysis of various misunderstandings in the use of centrifugal pumps


1. High lift pump for low head pumping For the centrifu […]

1. High lift pump for low head pumping

For the centrifugal pump, when the pump model is determined, the power consumption is proportional to the actual flow of the pump. The flow of the pump will decrease with the increase of the head, so the higher the lift, the smaller the flow and the smaller the power consumption. Conversely, the lower the head, the greater the flow and the greater the power consumed. Therefore, in order to prevent motor overload, it is generally required that the pump's actual pumping head should not be less than 60% of the nominal head. Therefore, when the high head is used for pumping the pump with too low lift, the motor is easily overloaded and generates heat. In severe cases, the motor can be burned. If it is used in emergency, it must be installed on the outlet pipe to adjust the amount of water out of the gate valve (or a small outlet with a small object such as wood) to reduce the flow and prevent the motor from overloading. Pay attention to the temperature rise of the motor. If the motor is found to be overheated, turn off the flow at the outlet or turn off the power immediately. This is also easy to misunderstand. Some operators think that blocking the outlet and forcing a reduction in traffic will increase the motor load. In fact, on the contrary, regular high-power centrifugal pump irrigation units are equipped with gate valves on the outlet pipe. In order to reduce the motor load when the unit is started, the gate valve should be closed first. This is the reason that the valve is gradually opened after the motor is started.

2. Large diameter pump with small water pumping

3. When installing the inlet pipe, the horizontal section is horizontal or upward
This will cause the air in the inlet pipe to collect air, reduce the degree of vacuum in the pipes and the water pump, reduce the pump suction head, and reduce the amount of water output. The correct approach is: The horizontal section should be slightly inclined to the direction of the water source, should not be horizontal, but not upturned.

4. More elbows used in the inlet pipe
If more elbows are used in the inlet pipe, local flow resistance will increase. And the elbow should be turned in the vertical direction, not allowed to turn in the horizontal direction, so as not to gather air.

5. The water pump inlet is directly connected with the elbow
This can cause uneven distribution of water as it enters the impeller through the elbow. When the diameter of the inlet pipe is larger than the inlet of the pump, an eccentric reducer should be installed. Eccentric reducer tube is to be mounted on the flat surface, and the inclined surface is mounted on the bottom. Otherwise, the air will gather, the amount of water will be reduced or the water will not be able to be pumped, and there will be a crash. If the inlet pipe and the water pump inlet diameter are equal, a straight pipe shall be added between the inlet of the pump and the elbow. The length of the straight pipe shall not be less than 2 to 3 times the diameter of the pipe.

6. The bottom section of the inlet pipe with bottom valve is not vertical

7. The inlet of the inlet pipe is not in the right position

8. Outlet nozzle is above normal water level in the outlet basin