Grundfos LF User Manual

21
English (US)
4. Insufficient flow. a) The pump is not primed. Prime the pump.
b) The system pressure exceeds the shut off
pressure.
• Increase the liquid level on the inlet side.
• Open the isolating valve in the inlet pipe.
c) The speed of rotation is too low. Reestablish the correct speed of rotation.
d) The suction lift is too high or there is
insufficient NPSH.
Reduce the suction lift or restore required
NPSH.
e) The strainer or the impeller is clogged. Clean the strainer and the impeller passages.
f) Wrong direction of rotation. Reestablish the correct direction of rotation.
g) Leaking joints. Tighten the joints.
h) Broken shaft or coupling Repair or replace damaged parts.
i) Closed inlet valve. If the inlet valve is closed, open it slowly.
j) There is not enough inlet pressure for hot
or volatile liquids.
Reestablish required inlet pressure.
k) Foot valve is too small. Replace the foot valve.
l) Worn or damaged hydraulic parts. Repair or replace the worn parts.
m) Excessive clearance between the wear
surfaces.
See section 8.5 Replacing the wear ring.
5. The pump loses its prime after
starting.
a) Joints or the stuffing box are leaking. • Tighten the joints or the stuffing box gland.
• Replace the shaft sleeve.
• Replace the gaskets.
b) The suction lift is too high or there is
insufficient NPSH.
Reduce the suction lift or restore required
NPSH.
6. Excessive power required. a) The speed of rotation is too high. Reduce the speed of rotation.
b) The pump is operating beyond its
recommended performance range.
Set the duty point in accordance with the
recommended performance range.
c) The specific gravity or viscosity of the
pumped liquid is too high.
If less flow is sufficient, reduce the flow on the
outlet side, or fit the pump with a more powerful
motor.
d) The shaft is bent. Replace the shaft.
e) The stuffing-box is too tight. Retighten the stuffing box if possible.
Alternatively, repair or replace the stuffing box.
f) The impeller clearance is too small causing
rubbing or worn wear surfaces.
Adjust the impeller clearance, if possible, or
replace the wear ring.
g) There is an electrical or mechanical defect
in the motor.
Contact your local service center for
diagnostics.
h) The pump is restricted in its rotation. Remove any obstacles or replace any worn
parts.
i) Incorrect lubrication of the motor. Reestablish correct lubrication of the motor.
Fault Cause Remedy
LC_LCV_LF_LCS_1 language_US Eng.book Page 21 Thursday, August 24, 2017 4:08 PM

Grundfos LF Specifications

General

Brand	Grundfos
Model	LF
Category	Water Pump
Language	English