Identi Cation; System Design; Closed-System Design; Closed Water Hydraulic Systems, Water - Danfoss PAHT Operation, Installation, And Maintenance Manual

Operation guide
1.

Identi cation

2.

System design

© Danfoss | 2023.12
Installation, Operation and Maintenance Manual for PAHT 20-90 pumps
Systems can be either:
• Water hydraulic systems, in which the water
is recirculated back to tank.
• Open-ended systems with water supply
from a tank.
• Open-ended systems with direct water-
supply (boosted pressure).
The design of the system must ensure that
selfemptying of the pump during standstill is
avoided.
The minimum boost pressure is 2 barg (29 psig)
and the maximum peak pressure is 20 barg
(290 psig). The recommended normal boost
pressure is 2-6 barg (29-87 psig) (3-7 barg
[43.5-101.5 psig] abs).

2.2 Closed-system design

A Inlet line:
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).
B Inlet lter:
Install the inlet lter (1) in front of the tank
(2). Place the tank above pump and pump
inlet. Please consult the Danfoss lter data
sheet for guidance on how to select the
right lter.
C Monitoring pressure switch:
Install the monitoring pressure switch (3) in
front of the lter (1). Set the maximum inlet
pressure to 2 barg (29.0 psig). The monitor-
ing pressure switch will stop the pump (5) if
inlet pressure is higher than 2 barg
(29.0 psig), indicating that the lter element
must be changed.
D Monitoring temperature switch:
Install the monitoring temperature switch
(4) in the tank. Set the temperature value
according to technical data, item 4. The
monitoring temperature stops the pump if
inlet temperature is higher than the set
value.
Protective cap must be removed
and thrown away before usage.
If it is unknown what the peak inlet pressure can
be, then there should be a 15 barg (218 psig)
safety relief valve on the inlet side of the pump.
Note: All mentioned pressures refer to
measures in the respective pump gauge ports.
The inlet pressure of the pump must never
exceed the outlet pressure. This may typically
occur in boosted or open-ended systems with
supply direct from the tap and where a bypass
valve is activated.

2.1 Closed water hydraulic systems, water

recirculated
In order to eliminate the risk of cavitation, always
ensure a minimum inlet pressure of 0 barg
(0 psig) (1 barg [14.5 psig] abs) by observing the
following guidelines:
.
E Hoses:
Always use exible hoses (6) to minimize
vibrations and noise.
F Inlet pressure:
In order to eliminate the risk of cavitation
and other pump damage, pump inlet
pressure must be maintained according to
speci cations described in item 4, technical
data.
G Non-return valve (7):
Should be installed after the outlet to
prevent pump backspin, which may ruin
the pump.
H Pressure relief valve:
As the Danfoss PAHT pump begins to
create pressure and ow immediately after
start-up regardless of any counter pressure,
a pressure relief valve (8) should be
installed to prevent system damage.
I System water lling:
To ensure proper ltration of new water
(10) supplied to the system, always use the
lling valve (9).
J Minimum level switch:
Install the minimum level switch (11) above
the outlet of the reservoir. The level switch
must stop the pump if the water in the
reservoir is below the switch, which
indicates that the reservoir is empty.
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