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180R9265 / IOM APP 16-22 Appendices - v02 / 01.2013
Instruction Trouble shooting guide for APP pumps
Cause Remedy Comments
2.1 Wear on pump
Large internal leakage due to:
- Pre-treatment
- Main ltration
- Fluid type
- High uid temperature
2.1.1 Dismantle the pump.
2.1.2 Check valve plate.
Valve plate has marks/scratches on the
surface facing the port plate. Minor wear
on valve plate can cause large internal
leakage. See Index 6.1
2.1.3 Check port plate.
Port plate has marks/scratches on the
surface facing the valve plate. Minor wear
on port plate can cause large internal
leakage. See Index 6.2
2.1.4 Check cylinder barrel.
Liners in cylinder barrel may be scratched
or worn. Insert a piston in the liner and
check the t. If there is any space
(clearance) between liner and piston, liner
or piston is worn.
2.1.5 Analyse uid for content of particles.
2.1.6 Check that lters are OK and working
correctly.
2.1.7 Install correct pre-lter (1μm nom.
string-wound lter).
2.1.8 Check that the correct lter type is used
(particles in uidmust not exceed 10 μm).
Danfoss RO Solutions supply lters.
Please contact Danfoss sales oce.
2.1.9 The APP pump is designed for seawater
operation; for any other uid, please
contact Danfoss sales oce for further
help.
2.1.10 If uid temperature is above 50°C, stop
the pump immediately.
2.1.11 Check internal parts (see above).
See instruction on replacement criteria
(521B0925).
Are available on www.ro-solutions.com
Typical signs of wear:
Polished surface all over the swash plate.
Normally, only half of the swash plate = the
pressure side is polished. See index 6.3.
If the ring is missing, the piston is very worn.
The lters can be bypassed, even if they are
correctly mounted. Some lters can create
channelling where particles can pass trough the
lter in tunnels. String wound lters are
typically channelling lters. A string wound
lter may have a ltration eciency of only
50%, which will cause internal wear and must
always be followed by a main lter.
Insucient ltration means that too many or
too large hard particles can pass the main lter
because it is damaged, bypassed or simply too
poor. Filtration eciency must be 99.98%
(Beta = 5000) at 10 μmto prevent abnormal
wear of the pump.
Temperature > 50° C will cause wear on internal
pump parts. Mount a temperature switch and
check its set point / function. The temperature
switch will ensure that the pump stops at uid
temperatures > 50° C.
2.2 Low inlet pressure 2.2.1 Check that booster pump supplies the
right pressure/ow.
2.2.2 Check if lters require replacement.
If the pressure drop across the lters is too high,
the booster pump does not deliver sucient
ow/pressure. No pressure or low pressure
results in cavitation and insucient internal
lubrication causing wear on internal pump
parts.
Mount a low-pressure switch before the pump
and check its set point/ function. The low-
pressure switch ensures that the pump does
not start until the inlet pressure has reached
1 bar.
2.3 Rotation speed (RPM) 2.3.1 If VFD-operated, check frequency.
2.3.2 Check that rotation speed of the electric
motor is as stated on name plate on
electric motor. Check that the motor rotor
winding is not damaged.
Speeds below 700 rpm result in insucient
internal lubrication causing wear on the
internal pump parts.
2. Reduced ow/reduced pressure
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