4. 5. Operating troubles causes and remedies
Before attempting to cure any operating troubles, the instruments on the pump should be checked in respect of their reliability
and accuracy.
4. 5. 1. Pump does not deliver rated capacity
Possible cause Remedy
1. Excessive pressure in discharge line.
Increase pump speed. If this impossible on an electrically driven
pump, it may be necessary to fit oversize impellers or extra
stages to the pump. Please consult us first.
2. Incomplete priming or venting of pump or piping.
Prime the pump and piping again and carefully vent them, if
necessary change the layout of the piping and fit vent cocks or
vent lines.
3. Suction line or impeller clogged.
Clean out the suction line and if necessary dismantle and clean
the impeller.
4. The suction head is too low (on pumps operating with
positive suction head).
Check the liquid level in the suction vessel. Check that the
isolating valves in the suction line are fully open, and if
necessary lock them open to prevent accidental closure.
Examine piping for faulty runs and high resistance lengths.
Clean any strainers incorporate in the line. Before restarting the
pump, check that the rotor can be turned easily by hand.
5. Excessive suction lift (on pumps operating with
suction lift).
Check liquid level in pit, and make sure that the foot valve is
fully open. Clean out the strainer basket and the suction
piping, and if necessary fit larger bore suction piping.
6. Entrainment of air through the stuffing box.
Increase sealing fluid pressure; check sealing fluid line in case
it is cogged, and clean it if necessary.
7. Reverse rotation.
Restore correct rotation by changing pole connections of the
motor. If the pump has run for any length of time in reverse
rotation, the condition of balancing device and of the shaft
protecting sleeves should be checked; The shaft sleeves must
seat properly and should be screwed up if necessary.
8. Pump speed is too low.
On electrically driven pumps, this fault cannot be easily
remedied. Please consult our works, indicating the actual
speed of the motor. On pumps driven by an internal
combustion engine, the speed can be adjusted within certain
limits by adjusting the fuel governor. On pumps driven by a
steam turbine, the speed can usually be adjusted by suitably
adjusting the turbine governor. On belt driven pumps, belt
slippage may cause the speed to drop; the belt should be
tightened, or if necessary a pulley of different diameter should
be used.
9. Excessive wear of the pump internals. Open up the pump, and check the clearances between part
subjected to wear, e.g. 5020/2300, or 1060/5251, or
1070/6010 (on sizes MML 40-125), or 1070/5252 (on sizes
MML 150-350), or 6010 or 5252 and 5210 (on sizes MML 200-
350), as the case may be. Adjust as necessary, or replace
worn components by new ones.
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