Fault Finding Chart - Grundfos Fire NKF series Montage- Und Betriebsanleitung

15. Fault finding chart

Warning
Before removing the terminal box cover and before any removal/dismantling of the pump, make sure that the power
supply has been switched off.
Fault Cause
1. The pump delivers a) Wrong electrical connection (2 phases).
no or too little
water.
b) Wrong direction of rotation.
c) Air in suction pipe.
d) Counter-pressure too high.
e) Inlet pressure too low.
f) Suction pipe or impeller blocked by impurities.
g) Pump draws in air due to defective seal.
2. Motor is a) Pump blocked by impurities.
overloaded.
b) Pump runs over the dimensioned duty point.
c) Overload setting is incorrect.
d) The motor runs on 2 phases.
3. Pump makes too a) Inlet pressure too low (cavitation).
much noise.
Pump runs
b) Air in suction pipe or pump.
unevenly and
c) Counter-pressure is lower than specified.
vibrates.
d) Impeller out of balance (blocked impeller
blades).
e) Inner parts worn.
f) Pump stressed by the pipework (thus causing
starting noise).
g) Defective bearings.
h) Defective motor fan.
i) Defective coupling.
j) Foreign bodies in the pump.
4. Leakage in pump a) Pump stressed by the pipework (thus causing
housing or in leaks in the pump housing or connections).
connections.
b) Pump housing gaskets or gasket at
Leakage in shaft
connections defective.
seal.
c) Mechanical shaft seal dirty or stuck together.
d) Mechanical shaft seal defective.
e) Shaft surface or shaft sleeve defective.
f) Mechanical shaft seal dirty or stuck together.
5. Too high a) Air in suction pipe or pump.
temperature in
b) Inlet pressure too low.
pump or motor.
c) Bearings lubricated with too little, too much or
unsuitable lubricant.
d) Pump with bearing seat stressed by the
pipework.
e) The axial pressure is too high.
f) Motor-protective circuit breaker is defective or
setting is incorrect.
g) Motor is overloaded.
14
Remedy
Check the electrical connection and remedy,
if necessary.
Interchange two phases in the power supply.
Vent the suction pipe or the pump and replenish.
Set the duty point in accordance with the data sheet.
Check the system for impurities.
Make sure that all the conditions in section 5.2 Minimum
inlet pressure and 7.5 Pipework are complied with.
Clean the pump.
Check the pipeline seals, pump housing gaskets and
shaft seals, and replace, if necessary.
Clean the pump.
Set the duty point in accordance with the data sheet.
Check the setting of the motor-protective circuit breaker
and replace, if necessary.
Check the electrical connections. Replace the fuse,
if defective.
Make sure that all the conditions in section 5.2 Minimum
inlet pressure and 7.5 Pipework are complied with.
Vent the suction pipe or the pump and replenish.
Set the duty point in accordance with the data sheet.
Clean and check the impeller.
Replace defective parts.
Mount the pump so that it is not stressed.
Support the pipes.
Replace bearings.
Replace the fan.
Replace the coupling. Align the coupling.
See section 8.2 How to align the unit.
Clean the pump.
Mount the pump so that it is not stressed.
Support the pipes.
Replace the pump housing gaskets or connection
gaskets.
Check and clean the mechanical shaft seal.
Replace the mechanical shaft seal.
Replace the shaft or the shaft sleeve.
Replace the packing in the stuffing box.
Check and clean the mechanical shaft seal.
Vent the suction pipe or the pump and replenish.
Make sure that all the conditions in section 5.2 Minimum
inlet pressure and 7.5 Pipework are complied with.
Replenish, reduce or replace the lubricant.
Mount the pump so that it is not stressed.
Support the pipes.
Check the alignment of the coupling.
See section 8.2 How to align the unit.
Check the relief holes of the impeller and the lock rings
on the suction side.
Check the setting of the motor-protective circuit breaker
and replace, if necessary.
Reduce the flow rate.