29
10.3
Troubleshooting Table
Problem
Possible Cause
Remedy
Pump either does not pump or pumps irregu-
larly.
Suction line blocked/clogged.
Open/clean suction line.
Suction filter contaminated.
Clean suction filter.
Discharge-side shut-off valve closed.
Open discharge line.
Pump not completely filled with
liquid.
Install pipe system so that casing is still filled with
liquid when pump is off.
Pump with geodesic suction head
1
; liquid level
falls at standstill.
Install foot valve in suction line.
Suction line leaky (drawing in air).
Seal suction line.
Foot valve blocked or contaminated.
Reestablish proper function of foot valve; clean.
Suction head too high.
Lower pump;
reduce suction head.
Air pocket in suction line.
Lay suction line at steady incline.
Excessive air or gas in pumping medium.
Install vent valve.
Air ingress at shaft seal.
Check shaft seal installation.
Replace elastomers.
Cavitation at impeller inlet;
resistance in suction line too high;
suction head too high.
NPSHa values not adapted to pump.
Optimize suction line;
increase inlet height;
lower media temperature;
contact
Fristam
.
Flow rate too high.
Discharge-side valve opened too wide.
Throttle valve.
Discharge line diameter too large.
Reduce nominal pipe size;
insert orifice plate.
Impeller diameter too large.
Trim impeller outside diameter.
Reduce speed with frequency converter.
Contact
Fristam
.
Flow rate too low; discharge head too low.
Selected pump too small.
Contact
Fristam
.
Selected impeller diameter too small.
Contact
Fristam
.
Replace impeller.
Direction of rotation of motor incorrect.
Exchange connections on motor terminal box.
Speed too low
(voltage incorrect).
Correct connection according to motor rating
plate.
Nominal pipe sizes too small.
Use larger pipe diameters.
Pipe resistances in suction and/or
discharge line too high.
Optimize pipe system;
reduce elbows and valves.
Contact
Fristam
.
Pipe clogged or full of deposits.
Clean pipes.
Foreign objects/deposits in impeller.
Remove impeller and clean.
Impeller incorrectly adjusted.
Check impeller clearance and readjust.
Density of pumping medium too high.
Viscosity of pumping medium too high.
Contact
Fristam
.
Metal noise.
Foreign objects in pump interior.
Disassemble, inspect, and repair.
Impeller catching.
Readjust impeller clearance;
tighten impeller nut using
torque wrench.
Pump/shaft seal running dry.
Immediately supply pumping medium;
open suction valve.
Table 14 Troubleshooting table