n
20
Symptom on Pump
Trouble
Inspection and
Countermeasures
With Discharge
Valve Closed
With Discharge
Valve Open
Cause
Needles of
pressure and
vacuum gauges
indicate normal
values.
Needle of
vacuum gauge
indicates high
value.
l
Strainer is clogged
with foreign matter
and liquid passage
is blocked.
¡
Remove foreign matter
in strainer.
Needle of
vacuum gauge
indicates abnor-
mally high value.
l
Air is trapped in
suction pipe.
¡
Inspect installation of
suction pipe and modify
it as necessary.
l
Inlet section of
impeller unit is
clogged with
foreign matter.
¡
Partially disassemble
unit and remove foreign
matter.
Needles of
pressure gauge
and vacuum
gauge fluctuate.
l
Air enters via
suction pipe or
gasket section.
¡
Check flange gaskets of
suction pipe and tighten
Vacuum gauge
needle indicates
high value while
pressure needle
indicates normal
value.
l
Air pocket or
resistance in
suction pipe.
¡
Inspect suction piping
installation and make
corrective adjustments.
Pressure gauge
needle indicates
high value while
vacuum gauge
needle indicates
normal value.
l
There is a section in
discharge pipe that
causes high resis-
tance or actual
head and loss of
head are too high.
¡
Check actual head and
piping loss of discharge
pipe and take necessary
measures.
l
Discharge side of
pump is clogged
with foreign
matter.
¡
Remove foreign matter
in pump.
¡
Remove foreign matter
or scale inside of piping.
Discharge
quantity
is small.
