Grundfos LFE Instrucciones De Instalación Y Funcionamiento página 19

Fault
4. Insufficient flow.
5. Pump loses its prime after
starting.
6. Excessive power required.
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Cause
a) The pump is not primed.
b) The system pressure exceeds the shut off
pressure.
c) The rotation speed is too low.
d) The suction lift is too high or there is
insufficient NPSH.
e) The strainer or impeller is clogged.
f) Wrong direction of rotation.
g) Leaking joints.
h) Broken shafting or coupling.
i) Closed inlet valve.
j) There is not enough inlet pressure for hot
or volatile liquids.
k) Foot valve is too small.
l) Worn or damaged hydraulic parts.
m) Excessive clearance between the wear
surfaces.
a) Joints or the stuffing box are leaking.
b) The suction lift is too high or there is
insufficient NPSH.
a) The speed of rotation is too high.
b) The pump is operating beyond its
recommended performance range.
c) The specific gravity or the viscosity of the
pumped liquid is too high.
d) The shaft is bent.
e) Stuffing-boxes too tight.
f) Impeller clearances are too small causing
rubbing or worn wear surfaces.
g) There is an electrical or mechanical defect
in the motor.
h) The pump is restricted in its rotation.
i) Incorrect lubrication of the motor.
Remedy
Prime the pump.
• Increase the liquid level on the inlet side.
• Open the isolating valve in the inlet pipe.
Reestablish the correct speed of rotation.
Reduce the suction lift or restore required
NPSH.
Clean the strainer and impeller passages.
Reestablish the correct direction of rotation.
Tighten the joints.
Repair or replace damaged parts.
If the inlet valve is closed, open it slowly.
Reestablish required inlet pressure.
Replace the foot valve.
Repair or replace the worn parts.
See section
8.5 Replacing the wear
• Tighten the joints or the stuffing box gland.
• Replace the shaft sleeve.
• Replace the gaskets.
Reduce the suction lift or restore required
NPSH.
Reduce the speed of rotation.
Set the duty point in accordance with the
recommended performance range.
If less flow is sufficient, reduce the flow on the
outlet side, or fit the pump with a more powerful
motor.
Replace the shaft.
Retighten the stuffing box if possible.
Alternatively, repair or replace the stuffing box.
Adjust the impeller clearance, if possible, or
replace the wear ring.
Contact your local service center for
diagnostics.
Remove any obstacles or replace any worn
parts.
Reestablish correct lubrication of the motor.
ring.
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