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9
Problem
Cause
What to do
Wrong direction of rota-
tion
- Electric cables to motor wrongly
connected.
Reverse the terminal connection on
electric motor.
21
Connecting and disconnec-
ting of electric cables must
be done only by personnel
authorized to do such
work.
The pump cannot be
primed
- Wrong direction of rotation.
- Suction line is not open or pressure
drop in the suction line is too high.
- Major air leakage into the suction
line.
- The pump cannot evacuate the air
through the discharge line due to
excessive counter pressure.
See above.
Check all components in suction line.
The inlet condition should be checked
with a vacuum gauge at the pump inlet.
Check the suction line.
See the chapter on Deaeration
(see page 19).
The magnetic coupling is
slipping
- A too high viscosity has caused the
magnetic coupling to slip.
- The pump is blocked inside the ro-
tors by a foreign object.
Lower the viscosity to a maximum
approved (the viscosity normally used
in the pumped liquid) and restart the
pump by switching it off and on.
Remove the foreign object from the
pump and control the bores and rotors
for abnormalities/damages. Restart the
pump by switching it off and on.
No flow
- The pump is not primed.
- The pressure relief valve is set be-
low the counter pressure.
See above.
Readjust the pressure relief valve to a
value above counter pressure.
Flow too low
- The magnetic coupling is slipping
- The pressure relief valve is set too
low (Discharge pressure also low).
- Something is restricting the flow in
the suction line. (This would usually
cause noise).
- The pumped liquid contains a
significant amount of compressible
gas, such as free air. (This would
usually cause noise).
See above.
Readjust the pressure relief valve
Check all components in the suction
line (strainers, valves etc.).
Go thru the system and determine if
there are any leaks.
Trouble shooting
