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Analysis of Common Problems of Axial Flow Pump and Mixed Flow Pump

Sep. 25, 2020

Axial flow pumps and mixed flow pumps are relatively simple in structure, easy to operate, and reliable in operation. However, if the manufacturing quality is not high, the installation is improper, the operation and maintenance are not good, the repair is not timely, etc., some failures sometimes occur.

1. Insufficient or no water.

The reasons for the axial flow pump may be: blade wear, fracture or insufficient submergence depth, or blade installation angle is too small and blade installation reverse, etc.; the direction of rotation is wrong, or the speed does not meet the design requirements; the head is too high and the supporting power is insufficient. The reasons for the mixed flow pump may be: impeller damage; the air in the water inlet pipe is not exhausted, or the water inlet pipe and the packing leak; the water pump rotates incorrectly, or the speed is too low; the suction lift is too high or the total head is too high, or the gate valve, There are obstructions on the pipeline; the supporting power is insufficient, etc.

Treat it according to the reason of insufficient or no water output from the water pump. If the impeller is damaged, the blade angle is too small, the impeller is reversely installed, the steering is incorrect, the speed is insufficient, the pipeline is obstructed, the vacuum is insufficient, and the power is insufficient, etc., should be adjusted and improved as required to make the pump run normally. If the system head is too high, you should first find out the installation situation of the piping system, and study to reduce the loss head, thereby reducing the total pump head; secondly, study whether to increase the pump speed or increase the blade installation angle. If both cannot be solved, the water pump needs to be replaced or the water pump series connection method is adopted.

2. There are many reasons for the overload of the power machine.

(1) The flow and head exceed the design range. The solution varies from pump to pump. Axial flow pumps use speed reduction and blade angle reduction, and mixed flow pumps use throttling, speed reduction and turning impellers.

Mixed Flow Pump

(2) The speed of the water pump exceeds the regulation. According to the law of proportionality, the power of the pump increases with the third power of the speed. The running speed of the pump should be measured to check whether it exceeds the rated speed.

(3) Pump rotation part of the obstacles, such as blades around debris, shaft bending, blade and pump housing friction, bearing damage, transmission belt is too tight, sometimes because of packing pressure is too tight, pipeline congestion will also appear the power machine overload phenomenon. Remove the obstacle and the pump will operate normally.

(4) The tap door of the outlet pipe is not opened or the opening angle is insufficient. The opening angle of the slap door depends on the weight of the door body, buoyancy, water current impulse and cushioning force. When the opening angle reaches 50°, the loss head of the door body is already very small, so it is generally required that the opening angle should be greater than 50°-60°.

3. Noise and vibration occur when the pump is running, and its Haraoka is also multifaceted.

(1) The external circle of the blade and the pump shell friction, the bending of the pump shaft makes the bearing wear too much, the two shafts of the transmission are not aligned, there are impurities and foreign matter around the blade fall into the pump, etc., will cause noise and vibration, should be stopped to check and correct, remove obstacles.

(2) The foot screw is loose, the nut on the pump shaft and the drive shaft is loose, the coupling screw is loose, etc., all should be checked one by one, and the loose part should be tightened.

(3) Cavitation occurs. The cause of cavitation should be checked and analyzed and dealt with. If the suction lift is too high, the installation height of the pump should be lowered.

(4) In the same inlet tank, several pumps are arranged improperly. When the pumps are running, they interfere with each other and generate vortices, which will cause a large amount of air to enter the pump body and cause vibration. The pumps should be rationally arranged to reduce mutual interference.

(5) When the axial flow pump runs at a stage before the saddle-shaped inflection point, it is also prone to vibration and noise, so it is better to avoid this stage.

The above information is provided by axial flow water pump manufacturer.

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