English (GB)
27
7
The impeller is completely
clogged.
Dismantle the pump and clean the impeller.
8
The inlet pipe is partially blocked.
Remove any obstructions in the inlet pipe.
9
Air leak in the inlet pipe or flange.
Replace or repair the defective pipe section or flange.
10
Air leak in the stuffing box.
Clean the flushing pipe. Replace the stuffing box packing rings, if
necessary.
11
Cavitation; insufficient NPSH
(depending on installation).
1. Increase the net positive suction head by placing the pump in
a lower position.
2. Pressurise the inlet vessel.
12
The impeller or wear rings are
worn.
Replace the impeller and/or wear rings. If necessary, also
replace the bearings and the shaft.
13
Defective packing rings.
Replace the packing rings.
14
The non-return valve is too small
or partially obstructed.
Replace or clean the non-return valve.
15
The inlet pipe is not immersed
deeply enough.
Extend the inlet pipe so that the risk of sucking air is eliminated.
16
The impeller diameter is too small.
Check with Grundfos if you can use a larger impeller. If not,
reduce the outlet pipe friction losses. But be careful not to
seriously overload the motor.
17
Obstruction in pump casing.
Dismantle the pump and remove the obstruction.
18
Air or gases in the liquid.
Remove the gas or air from the pumped liquid.
See 11 above.
19
The actual duty point of the pump
lies to the right of the specified
duty point on the pump curve. The
result is lower head, higher flow
and higher power consumption.
Install an orifice plate immediately after the outlet flange. The
orifice plate will raise the system characteristic or increase the
counterpressure thus increasing the head and lowering the flow.
The size of the orifice plate must be adapted so that the pressure
corresponds to the required duty point.
20
The viscosity or specific gravity of
the pumped liquid is higher than
that of water.
Use a larger motor. Consult Grundfos for recommended size.
Test the liquid for viscosity and specific gravity.
21
The shaft is bent due to damage.
Check the deflection of the shaft. The total indicator runout must
not exceed 0.05 mm.
Possibly replace the shaft.
22
Mechanical failure of bearing
and/or impeller.
Check the bearings and the impeller for damage.
Replace the bearings or the impeller, if necessary.
23
Misalignment.
Realign the pump and motor.
24
Electrical defects.
Check that the voltage and frequency of the power supply are
correct.
Remedy the possible defects in the motor.
Check that the motor is properly cooled.
25
The speed is too high.
Check that the frequency of the power supply corresponds to the
frequency stated on the motor nameplate.
26
The foundation is not rigid enough.
Retighten the anchor bolt nuts. Make sure that the foundation is
made according to the installation and operating instructions.
27
The lubricating oil or grease is dirty
or contaminated.
Clean the bearings and bearing housings according to the
instructions and relubricate the bearings.
No. Cause
Remedy
