English (GB)
8
8. The pump
performance is
unstable.
a) Pump inlet pressure too low. Check the inlet conditions of the pump.
b) Suction pipe is partly blocked by
impurities. Remove and clean the suction pipe.
c) Leakage in suction pipe. Remove and repair the suction pipe.
d) Air in suction pipe or pump. Vent the suction pipe/pump.
Check the inlet conditions of the pump.
9. The pump runs
backwards when
switched off.
a) Leakage in suction pipe. Remove and repair the suction pipe.
b) Foot or non-return valve defective. Remove and clean, repair or replace
the valve.
c) The foot valve is stuck in completely
or partly open position.
Remove and clean, repair or replace
the valve.
Self-priming pumps only:
10. The pump
performance is
unstable and the
pump is noisy.
a) The differential pressure across the
pump is too low. Close the tap gradually until the
discharge pressure is stable and the
noise has ceased.
11. When startup is
attempted, the
pump will start, but
delivers no
pressure or flow.
a) Liquid column above non-return
valve in discharge pipe prevents the
pump from self-priming.
Empty the discharge pipe. Make sure
that the non-return valve does not hold
back liquid in the discharge pipe.
Repeat the startup procedure.
b) Suction pipe draws in air. Make sure that the suction pipe is
airtight from pump to liquid level.
Repeat the startup procedure.
12. The pump runs, but
does not deliver
the rated flow.
a) The internal valve did not close. Close the tap gradually until the
pressure or flow suddenly increases.
Then open the tap gradually until the
required flow is reached.
13. The pump
performance is
unstable.
a) Pump inlet pressure too low. Check the inlet conditions of the pump.
b) Suction pipe is partly blocked by
impurities. Remove and clean the suction pipe.
c) Leakage in suction pipe. Remove and repair the suction pipe.
d) Air in suction pipe or pump. Vent the suction pipe/pump.
Check the inlet conditions of the pump.
14. The pump runs
backwards when
switched off.
a) Leakage in suction pipe. Remove and repair the suction pipe.
b) Foot or non-return valve defective. Remove and clean, repair or replace
the valve.
c) The foot valve is stuck in completely
or partly open position.
Remove and clean, repair or replace
the valve.
Self-priming pumps only:
15. The pump
performance is
unstable and the
pump is noisy.
a) The differential pressure across the
pump is too low. Close the tap gradually until the
discharge pressure is stable and the
noise has ceased.
16. When startup is
attempted, the
pump will start, but
delivers no
pressure or flow.
a) Liquid column above non-return
valve in discharge pipe prevents the
pump from self-priming.
Empty the discharge pipe. Make sure
that the non-return valve does not hold
back liquid in the discharge pipe.
Repeat the startup procedure.
b) Suction pipe draws in air. Make sure that the suction pipe is
airtight from pump to liquid level.
Repeat the startup procedure.
Fault Cause Remedy
