Wilo NPG Series Installation And Operating Instructions Manual page 21

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