Minimum Inlet Pressure; Motor Temperature - Grundfos CR Serie Instrucciones De Instalación Y Funcionamiento

9.1.3 Maximum permissible operating pressure
and liquid temperature for the shaft seal
The diagram below applies to clean water
and water containing antifreeze liquids.
CR, CRI, CRN 1s to 20 and CR, CRN 32 to 150
p [bar]
35
30
25
H H H
20
Q Q Q
HQQE/V
Q Q Q
15
E V E
10
5
0
-60 -40 -20 0 20
Fig. 20 Maximum permissible operating
pressure and liquid temperature
Standard shaft
seal
HQQE 0.37 - 45
HBQE
HQQV 0.37 - 45
HBQV
You can clean CRI and CRN pumps in place (CIP)
with a type H shaft seal with EPDM rubber parts,
HxxE and liquids up to 150 °C for maximum 15
minutes.
The pumping of liquids above 120 °C may
result in periodical noise and reduced
pump life.
CR, CRI, CRN pumps are not suitable for the
pumping of liquids above 120 °C for long periods.
22
H
Q
Q
E
40 60 80 100 120 140
t [°C]
Motor Temperature
[kW] range [°C]
-40 to +120
55-75 0 to 120
-20 to +90
55-75 0 to 90

9.1.4 Minimum inlet pressure

Hf
H
Pb
Fig. 21 Schematic view of open system with a
CR pump
Calculate the maximum suction lift "H" in m head as
follows:
H = Pb x 10.2 - NPSH - Hf - Hv - H
Pb = Barometric pressure in bar.
Barometric pressure can be set to 1 bar.
In closed systems, Pb indicates the
system pressure in bar.
NPSH = Net Positive Suction Head in m head, to
be read from the NPSH curve inthe
appendix (at the highest flow the pump
will be delivering.
Hf = Friction loss in the inlet pipe in m head
at the highest flow the pump will be
delivering.
Hv = Vapour pressure for water in m head.
See fig. 5 in the appendix.
If the pumped liquid is not water, then
use the vapour pressure for the liquid
which is being pumped.
tm = Liquid temperature.
Hs = Safety margin = minimum 0.5 m head.
If the calculated "H" is positive, the pump can
operate at a suction lift of maximum "H" m head.
If the calculated "H" is negative, an inlet pressure of
minimum "H" m head is required. There must be a
pressure equal to the calculated "H" during
operation.
NPSH
Hv