Model mp, mpa, mpai, Faults - causes and solutions – Xylem MPAI User Manual
Page 101
Installation, Operating and Maintenance Instruction
Model
MP, MPA, MPAI
MP 100-english
page 97
Revision 04
Article No 771074011
Issue 11/2011
11. Faults - Causes and Solutions
The following notes on causes of faults and how to
repair them are intended as an aid to recognising the
problem. The manufacturer's Customer Service
Department is available to help repair faults that the
operator cannot or does not want to repair. If the
operator repairs or changes the pump, the design data
on the Confirmation of Order / Data Sheet and chapter
2 of these Operating Instructions should be particularly
taken into account. If necessary, the written
agreement of the manufacturer must be obtained.
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Cause
Solution
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)
Back-pressure too low, discharge too low
throttle discharge valve
Speed too high
reduce speed
compare speed of motor with specified pump speed (rating plate)
when adjusting speed (frequency transformer) check refer-
ence value setting
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
Flow too little
increase min. flow (open discharge valve, bypass)
Flow too big
reduce flow (throttle discharge valve)
Impeller diameter too big
use smaller impeller
Impeller diameter too small
use larger impeller (check available motor power)
Pump and/or pipes not completely filled with liquid
fill
vent
Pump or suction/intake pipe blocked
clean
Air pocket in pipeline
vent
improve course of pipe
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)
Air being sucked in
increase liquid level
check if suction pipe is vacuum-tight
Air being sucked in through shaft sealing
clean sealing pipe
increase sealing pressure
replace shaft sealing
Direction of rotation is wrong
swap over two phases of power supply (to be done by an
electrician)
Inner components suffering from wear
replace worn parts
Density and/or viscosity of liquid handled is too high
seek assistance
Stuffing box not straight
tighten evenly
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
Lines and roughness on shaft or shaft sleeve
replace parts
Unsuitable packing material
use suitable material (check shaft or shaft sleeve for damage
beforehand)
Deposits on mechanical seal
clean
replace mechanical seal if necessary
if necessary provide additional rinsing or quench
Impeller out of balance
remove blocks/deposits
replace impeller if broken or unevenly worn
check shafts to ensure that they are running true
Coupling not aligned
align pump unit better
Coupling distance too small
change
Forces in pipeline too high (pump unit under strain)
change (support pipes, use compensators, etc.)
is foundation plate/frame properly cast in place?
Too much, too little or the wrong type of lubricant
change
Electricity supply not right (2-phase running)
check voltage of all phases
check cable connections and fuses
Sealing insufficient
tighten screws
replace sealing
Bearing damaged
replace
check lubricant and bearing space for pollutants (rinse oil area)
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