Reduced Flow/Reduced Pressure - Danfoss APP series User Manual

Instruction
2.

Reduced flow/reduced pressure

Cause
2.1 Wear on pump
Large internal leakage due to:
- Pre-treatment
- Main filtration
- Fluid type
- High fluid temperature
2.2 Low inlet pressure
2.3 Rotation speed (RPM)
Trouble shooting guide for APP pumps
Remedy
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 fit. If there is any space
(clearance) between liner and piston, liner
or piston is worn.
2.1.5 Analyse fluid for content of particles.
2.1.6 Check that filters are OK and working
correctly.
2.1.7 Install correct pre-filter (1μm nom.
string-wound filter).
2.1.8 Check that the correct filter type is used
(particles in fluidmust not exceed 10 μm).
Danfoss RO Solutions supply filters.
Please contact Danfoss sales office.
2.1.9 The APP pump is designed for seawater
operation; for any other fluid, please
contact Danfoss sales office for further
help.
2.1.10 If fluid temperature is above 50°C, stop
the pump immediately.
2.1.11 Check internal parts (see above).
2.2.1 Check that booster pump supplies the
right pressure/flow.
2.2.2 Check if filters require replacement.
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.
180R9265 / IOM APP 16-22 Appendices - v02 / 01.2013
Comments
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 filters can be bypassed, even if they are
correctly mounted. Some filters can create
channelling where particles can pass trough the
filter in tunnels. String wound filters are
typically channelling filters. A string wound
filter may have a filtration efficiency of only
50%, which will cause internal wear and must
always be followed by a main filter.
Insufficient filtration means that too many or
too large hard particles can pass the main filter
because it is damaged, bypassed or simply too
poor. Filtration efficiency 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 fluid
temperatures > 50° C.
If the pressure drop across the filters is too high,
the booster pump does not deliver sufficient
flow/pressure. No pressure or low pressure
results in cavitation and insufficient 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.
Speeds below 700 rpm result in insufficient
internal lubrication causing wear on the
internal pump parts.
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