Installation, Operating and Maintenance Instruction
Model LS, LC, LCP
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Cause
Solution
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Back-pressure too high
check facility for pollution, open discharge valve
reduce resistance in discharge pipe (e.g. clean filter if
necessary)
use larger impeller (note available motor power)
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Back-pressure too low, discharge too low
throttle discharge valve
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Speed too high
reduce speed
compare speed of motor with specified pump speed (rating
plate)
when adjusting speed (frequency transformer) check reference
value setting
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Speed too low
increase speed (check available motor power)
compare speed of motor with specified pump speed (rating
plate)
when adjusting speed (frequency transformer) check reference
value settings
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Flow too little
increase min. flow (open discharge valve, bypass)
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Flow too big
reduce flow (throttle discharge valve)
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Impeller diameter too big
use smaller impeller
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Impeller diameter too small
use larger impeller (check available motor power)
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Pump and/or pipes not completely filled with liquid
fill
vent
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Pump or suction/intake pipe blocked
clean
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Air pocket in pipeline
vent
improve course of pipe
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Suction height too big / NPSH of system too small
increase liquid level and admission pressure
reduce resistance in the intake/suction pipe (change course
and rated width, open shut-off valves, clean filters)
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Air being sucked in
increase liquid level
check if suction pipe is vacuum-tight
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Air being sucked in through shaft sealing
clean sealing pipe
increase sealing pressure
replace shaft sealing
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Direction of rotation is wrong
swap over two phases of power supply (to be done by an
electrician)
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Inner components suffering from wear
replace worn parts
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Density and/or viscosity of liquid handled is too high
seek assistance
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Stuffing box not straight
tighten evenly
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Stuffing box is fastened too tight resp. shaft sealing is worn loosen stuffing box
replace packing and/or mechanical seal
check sealing, flushing and cooling pipes (pressure)
avoid dry running
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Lines and roughness on shaft or shaft sleeve
replace parts
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Unsuitable packing material
use suitable material (check shaft or shaft sleeve for damage
beforehand)
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Deposits on mechanical seal
clean
replace mechanical seal if necessary
if necessary provide additional rinsing or quench
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Impeller out of balance
remove blocks/deposits
replace impeller if broken or unevenly worn
check shafts to ensure that they are running true
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Coupling not aligned
align pump unit better
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Coupling distance too small
change
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Forces in pipeline too high (pump unit under strain)
change (support pipes, use compensators, etc.)
is foundation plate/frame properly cast in place?
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Too much, too little or the wrong type of lubricant
change
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Electricity supply not right (2-phase running)
check voltage of all phases
check cable connections and fuses
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Sealing insufficient
tighten screws
replace sealing
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Bearing damaged
replace
check lubricant and bearing space for pollutants (rinse oil area)
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Relief fittings insufficient
clean relief openings in impeller
replace worn parts (impeller, split rings)
adjust in line with the system pressure/intake pressure given on
ordering
■
System-related vibrations (resonance)
seek assistance
