1.The blockage of balancing water pipe
If there is a blockage of the balancing water pipe, p6=p4 which means the balancing disc fail to generate balancing force. It will cause sever abrasion by axial force. In less serious case, the pump won’t work. Otherwise, the motor will be burned. The blockage of the balancing water pipe for multistage pumps is the common failure to solve and it happens a lot which is necessary for maintenance man to inspect.
2.Form tolerance of pump parts unqualified
As the high precision requirements of balancing disc and balancing ring, it won’s match when assemble the discharge parts. As soon as start the pump, it will be locking. The water pipe and balancing ring and balancing disc are fine, but assembled place of balancing ring in discharge part, which cause the asymmetry between balancing ring and balancing disc. If it happens, better change the discharge casing.
3.Pressure releasing from the balance ring
The balancing ring is connected by bolt with discharge casing, if the screws are not fastening will cause the releasing pressure which leads less balancing force, and the balancing disc have been worn out. You can check where between the balancing ring and discharge casing has been flushed. If yes, add extra o type seal ring and add some extra screws and fasten.
4.The clearance become large due to wear between balancing sleeve and shaft sleeve
Theoretically, larger clearance of b1 is more benefit for push the disc to open, but the efficiency will be declined. From actual operation of the pump, if b1 greater than 0.6, the balancing disc doesn’t work very well. It is because, I assume, when b1 greater than 0.6, the water volume will be big, and it will take more time for water pipe to suck the all water volume to suction stage. In the end, value of p6 rise, the differential pressure between p4 and p6 reduced and the balancing disc failed. Therefore, value of b1 should be 0.3-0.5.
5.Start the pump more often
It will cause great vibration in balancing device when it starts the pump, so it is not the best way under such circumstances.
