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8.8 Cavitation noise
Cause
Air leak in the inlet pipe or flange.
Cavitation; insufficient NPSH (depending on
installation).
The inlet pipe is not immersed deeply enough.
Air or gases in the liquid.
The speed is too high.
8.9 The pump bearings are overheated
Cause
The shaft is bent due to damage.
Mechanical failure of bearing and/or impeller.
Misalignment.
The lubricating oil or grease is dirty or contaminated.
8.10 The pump operates for a short time and then stops
Cause
The pump is not primed, lack of priming liquid,
incomplete priming.
The suction lift or static lift is too high.
Air leak in the inlet pipe or flange.
Air leak in the stuffing box.
Remedy
•
Replace or repair the defective pipe section or
flange.
1. Increase the net positive suction head by placing the
pump in a lower position.
2. Pressurise the inlet vessel.
•
Extend the inlet pipe so that the risk of sucking air is
eliminated.
•
Remove the gas or air from the pumped liquid.
•
See remedy in Cavitation; insufficient NPSH
(depending on installation) above.
•
Check that the frequency of the power supply
corresponds to the frequency stated on the motor
nameplate.
Remedy
•
Check the deflection of the shaft. The total indicator
runout must not exceed 0.05 mm.
•
Possibly replace the shaft.
•
Check the bearings and the impeller for damage.
•
Replace the bearings or the impeller, if necessary.
•
Realign the pump and the motor.
•
Clean the bearings and bearing housings according
to the instructions and relubricate the bearings.
Remedy
•
Fill the pump and inlet pipe completely with pumped
liquid.
•
Reduce the difference in height between the water
reservoir or water supply and the pump.
•
Replace or repair the defective pipe section or
flange.
•
Clean the flushing pipe. Replace the stuffing box
packing rings, if necessary.
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