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24
Wilo AG 09/2005
Excessive pump casing temperature
Pump or suction pipe not completely
filled
Check and complete filling
Suction level too low
• Check: the available NPSH > the
required NPSH
• Reduce geometrical suction lift
• Reduce head losses in pipes and in fit-
tings (diameter increase and appropri-
ate fitting positions)
• Check valves and strainers
• Check the immersion head of the suc-
tion valve
Wrong rotation
Reverse 2 phases on motor terminal
boxes
Pipes (valves, filter...)
Control, dismantle and clean
Insufficient flow rate
Check the suction and discharge pipes
(valves, back pressure)
Specific gravity or viscosity of liquid too
high
Consult our local agent to analyze the
problem
Insuffcient pressure
Rotation speed too low (check the dri-
ver)
Check the connection in the terminal
box according to the voltage
Presence of air
Check and de-aerate
Suction pressure insufficient
Check: the available NPSH > the required
NPSH
Mechanical defects
CONSULT US
Pump looses prime after starting
Presence of air
Check and de-aerate
Air leak in the suction pipe
Check suction pipe is airtight
Restriction in suction pipe
Check diameter of suction pipe
Suction level too low
• Check the NPSH >NPSH
• Reduce geometrical suction lift
• Reduce head losses in pipes and in fit-
tings (diameter increase and appropri-
ate fitting positions)
• Check valves and strainers
• Check the immersion head of the suc-
tion valve
Obstruction of suction pipe
Check condition of pipe
Defective gland packing on the shaft
• Check and replace all the gland
packing.
• Mechanical seal
Defective gasket
CONSULT US
Trouble
Possible Causes
Solutions
