Troubleshooting
Fault number
1
2
3
4
5
6
7
8
Cause
Remedy
–
X
–
X
–
–
–
X
Viscosity or specific gravity of the pumped
medium outside the range specified for the
pump
Consult the manufacturer.
–
X
–
X
–
–
–
–
Geodetic differential head and/or pipe flow
resistances too high
Remove sediments from the pump
and/or pressure pipe.
Install a larger impeller and consult the
manufacturer.
–
X
–
–
X
X
–
–
Pressure-side armature not opened wide
enough
Open the pressure-side armature.
X
X
–
–
X
X
–
–
Pressure pipe blocked
Clean the pressure pipe.
X
X
–
X
–
X
–
–
Pump running in the wrong direction
Swap any two phases on the motor.
X
X
–
X
–
–
–
–
Motor speed too low
Compare the required motor speed with
the specifications on the pump type
plate. Replace the motor if necessary.
Increase the motor speed if speed
control is available.
–
X
–
X
–
X
–
–
Pump parts worn
Replace the worn pump parts.
–
–
X
X
–
X
–
X
Pressure-side armature opened too wide
Throttle down at the pressure-side
armature.
Machine the impeller down. Consult the
manufacturer and adjust the impeller
diameter.
–
–
X
–
–
X
–
X
Geodetic differential head, pipe flow
resistances and/or other resistances lower
than specified
Throttle down the flow rate at the
pressure-side armature. Observe the
minimum flow rate.
Machine the impeller down. Consult the
manufacturer and adjust the impeller
diameter.
–
–
X
–
X
–
–
–
Viscosity lower than expected
Machine the impeller down. Consult the
manufacturer and adjust the impeller
diameter.
–
–
X
–
X
X
–
X
Motor speed too high
Compare the required motor speed with
the specifications on the pump type
plate. Replace the motor if necessary.
Reduce the motor speed if speed control
is available.
–
–
X
–
X
X
–
X
Impeller diameter too large
Throttle down the flow rate at the
pressure-side armature. Observe the
minimum flow rate.
Machine the impeller down. Consult the
manufacturer and adjust the impeller
diameter.
X
X
–
X
–
X
–
–
Impeller out of balance or blocked
Dismount the pump and inspect it for
dry-running damage.
Clean the impeller.
–
X
–
X
–
X
–
–
Hydraulic parts of the pump dirty, clotted or
encrusted
Dismount the pump.
Clean the parts.
–
–
–
–
–
–
–
X
Defective antifriction bearing in motor
Replace the antifriction bearing
(→ manufacturer’s specifications).
28
NI series
BA-2021.06 en-US
550 113 – 146-900/E