Xylem LN - Manual (Page 61)

Installation, Operating and Maintenance Instruction Model L, LN
Page 57
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 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
■ ■ Lines and roughness on shaft or shaft sleeve 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
■ ■ ■ 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