TROUBLESHOOTING
NA Series Operating & Instruction Manual
Page 36
PROBLEM
PROBABLE CAUSE
SOLUTION
OV
E
R
HEATE
D
(E
X
T
E
R
NAL) PUMP
BEA
R
IN
G
S
(Lo
ng
-c
o
up
led
units
onl
y
)
Low inlet pressure, with
cavitation, loss of efficiency and
loss of liquid film in the pump
bearings.
STOP THE PUMP
IMMEDIATELY!
(Mechanical damage may be
occurring)
Decrease suction lift (negative head).
Increase static suction (positive head)
Check for inlet obstructions or
restrictions.
Reduce liquid temperature.
Increase inlet pipework bore.
Decrease length of inlet pipework.
Open inlet valve fully.
Check for excessive liquid viscosity:
increase liquid temperature if necessary.
Reduce liquid temperature.
Misaligned or badly secured
pipework
Check pipework alignment and support.
Refer to LOCATION AND PIPING section.
Lack of oil in bearing housing
Check oil level: refill oil if necessary.
Replace bearings if necessary.
Incorrect oil in bearing housing
Drain and replace oil if necessary.
Replace bearings if necessary.
Excessive temperature of
pumped liquid
Refill bearing housing with correct oil for
working temperature of the pump.
