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180R9265 / IOM APP 16-22 Appendices - v02 / 01.2013
2.2 Preferred RO system design and P&ID
1. Dimension the inlet line to obtain mini-
mum pressure loss (large ow, minimum
pipe length, minimum number of bends/
connections, and ttings with small
pressure losses).
2. Place an inlet lter (1) in front of the APP
pump (2). Please consult the Danfoss lter
data sheet for guidance (521B1009) on how
to select the right lter. Thoroughly clean
pipes and ush system prior to start-up.
3. Place a monitoring pressure switch (3) set
at min. inlet pressure between lter and
pump inlet. The monitoring switch must
stop the pump at pressures lower than
minimum pressure.
4. Use exible hoses (4) to minimize vibrations
and noise.
5. In order to eliminate the risk of damage
and cavitation, a positive pressure at the
inlet (5) is always to be maintained at min.
inlet pressure and max. inlet pressure.
Recommend to install safety valve or a
pressure relief valve (9) in order to avoid
high pressure peaks in case the pump stops
momentarily or starts spinning backwards.
6. For easy system bleeding and ushing, a
bypass non-return vavle (6) is integrated in
the APP pump.
7. A non-return valve (7) in outlet can be
installed in order to avoid backspin of the
pump. The volume of water in the mem-
brane vessel works as an accumulator and
will send ow backwards in case of the
pump stops momentarily.
8. A safety valve or a pressure relief valve (8)
can be installed in order to avoid system
damage as the Danfoss APP pump creates
pressure and ow immediately after
start-up, regardless of any counter
pressure.
Note: If a non return valve is mounted in the
inlet line, a low pressure relief valve is also
required between non return valve and pump
as protection against high pressure peaks.
2.3 Reversible pumps
If exposed to high pressure in the outlet while the
electric motor is not energized, the pump will
start spinning backwards. This will not harm the
pump as long as the pressure in the inlet does not
exceed the max. pressure peak of 10 bar (145 psi).
If a non-return valve is mounted in the inlet line,
a low-pressure relief valve is also required as
protection against high-pressure pulses and high
pressure in general.
Alternatively a high-pressure check valve can be
mounted in the pump discharge line to prevent
the pump from reversing.
The dotted setup ensures that the inlet pressure
does not exceed 10 bar (145 psi), when a
non-return valve is mounted in the inlet.
Attention: In order to avoid the risk of cavita-
tion, the inlet pressure at the pump must be
min. 2 bar (29 psi).
The inlet line connection must be properly
tightened, as possible entrance of air will cause
cavitation.
2.4 General comments on
Filtration
A good ltration is vital to ensure a long and
trouble free life of the pump.
As water has very low viscosity, the APP pumps
have been designed with very narrow clearance
in order to control internal leakage rates and
improve component performance. Therefore it is
important that the inlet water is ltered properly
to minimize the wear of the pump.
The main lter must have a ltration eciency of
99.98% at 10 µm. We recommend to use
precision depth lter cartridges rated 10µm abs.
ß10>5000 (equivalent to a ltration eciency of
99.98%). Bag lters and string wound lter
cartridges typically have only 50% ltration
eciency. This means that for each 100,000
particles reaching the lter, 50,000 particles pass
through it compared to only 20 particles in a
lter with an eciency of 99.98%.
Instruction APP pump instruction APP 11-13 and APP 16-22
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