Xylem LMN - Manual (Page 53)

Installation, Operating and Maintenance Instruction Model LM, LMN
LM ger/fr/eng Page 49 Revision 06
Article No 771073101 Issue 08/2013
10. 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 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.
D
ischarge too l
o
w
D
ischarge stops after a ti
me
H
ead too l
o
w
H
ead too hi
gh
D
ri
v
e mechani
sm overl
oaded
P
u
mp not runni
ng qui
etl
y
Temperature i
n
pump too hi
gh
Temperature i
n
shaft seal
ing too hi
gh
Temperature at the beari
ng too hi
gh
P
u
mp l
eaki
ng
Leakage rate at shaft seal
ing too hi
gh
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 reference
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
■ ■ Lines and roughness at shaft replace parts
■ ■ 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
■ ■ ■ ■ ■ Forces in pipeline too high (pump unit under strain) change (support pipes, use compensators, etc.)
is foundation plate/frame properly cast in place?
■ 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
■ 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