36 | 180R9264 | AQ115586503043en-000903
© Danfoss | 2023.03
Operating guide
Installation, Operation and Maintenance APP 11-13
2.2 Preferred RO system design and P&ID
1.
Dimension the inlet line to obtain minimum
pressure loss (large flow, minimum pipe
length, minimum number of bends/
connections, and fittings with small
pressure losses).
2.
Place an inlet filter (1) in front of the APP
pump (2). Please consult the Danfoss filter
data sheet for guidance (521B1009) on how
to select the right filter. Thoroughly clean
pipes and flush system prior to start-up.
3.
Place a monitoring pressure switch (3) set at
min. inlet pressure between filter and
pump inlet. The monitoring switch must
stop the pump at pressures lower than
minimum pressure.
4.
Use flexible 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. Recom-
mend 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 flushing, a
bypass non-return valve (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 flow 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 flow 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 barg (145 psig).
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 barg (145 psig), 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 barg (29 psig).
The inlet line connection must be properly tightened,
as possible entrance of air will cause cavitation.
2.4 General comments on
Filtration
A good filtration 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 filtered properly
to minimize the wear of the pump.
The main filter must have a filtration efficiency of
99.98% at 10 µm. We recommend to use
precision depth filter cartridges rated 10 µm abs.
ß
10
≥ 5000 (equivalent to a filtration efficiency of
99.98%). Bag filters and string wounded filter
cartridges typically have only 50% filtration
efficiency. This means that for each 100,000
particles reaching the filter, 50,000 particles pass
through it compared to only 20 particles in a filter
with an efficiency of 99.98%.
Media filter
M
Brine
Permeate
Feed
PI
PI
PI
PT
PI
PI
PI
Fresh water
permeat flush
1
1
9
3
2
6
7
4
5
8
Instruction
