Danfoss APP 46 Installation, Operation And Maintenance Manual page 42

Operating guide
3. Building up the
pump unit
3-5 mm
0.12-0.20 inch
D
42 | 180R9407 | AQ274347577038en-000902
Installation, Operation and Maintenance APP 21-46 pumps
2.3 Reversible pumps
If exposed to high-pressure in the outlet while
the electric motor is not energized, the pumps
will start spinning backwards. This will not harm
the pumps 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.
In order to avoid the risk of cavitation, the
inlet pressure for APP 21-38 must be min.
2 barg (29 psig) and 3.5 barg (50.8 psig) for
APP 46, depending on speed. The inlet line
connection must be properly tightened, as
possible entrance of air will cause cavitation.
2.4 General comments
Filtration
A good ltration is vital to ensure a long and
trouble-free life of the pump.
3.1 Mounting
1. Mount the coupling ush or maximum
1 mm o set from the pump shaft end.
Ensure an air gap between coupling parts
of 3-5 mm (0.12-0.2 inch).
2. Mount the bell housing on pump. Secure
nuts with the right torque.
3. Measure the longest distance "A" from top
of bell housing to the button of coupling
claw.
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 e ciency of
99.98% at 10 m. We recommend to use preci-
sion depth lter cartridges rated 10 m abs. β10 ≥
5000 (equivalent to a ltration e ciency of
99.98%). Bag lters and string wounded lter
cartridges typically have only 50% ltration
e ciency. 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 e ciency of 99.98%.
For more information on the importance of
proper ltration, please consult our publication
"Filtration" (code number 521B1009), which also
will provide you with an explanation of ltration
de nitions and a guidance on how to select the
right lter.
Monitoring
It is recommended to continuously monitor the
following conditions:
• Filter clogging
• Pressure (inlet- and outlet side of the pump)
A: Elastic coupling
B: Bell housing
C: Motor shaft
D: Pump ange
4. Mount the coupling on motor shaft. Ensure
the coupling and motor ange are not in
contact with each other.
5. Measure from motor ange to the top of
the coupling. That measurement "B" shall
be 3-5 mm (0.12-0.2 inch) shorter than the
measurement "A".
("A" and "B" can be found on the next
page).
© Danfoss | 2023.03