Liquid Temperature; Maximum Permissible Operating Pressure And Liquid Temperature For The Shaft Seal; Minimum Inlet Pressure - Grundfos CR Serie Instrucciones De Instalación Y Funcionamiento

5.2 Liquid temperature

The table on page 333 states the relationship between liquid
temperature range and maximum permissible operating pressure.
The maximum permissible operating pressure and
Note
liquid temperature ranges apply to the pump only.
5.3 Maximum permissible operating pressure and
liquid temperature for the shaft seal
The diagram below applies to clean water and water
Note
containing anti-freeze 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
HBQE/V
E V E
10
5
0
-60 -40 -20 0 20
Fig. 3 Maximum permissible operating pressure and liquid
temperature
Motor
Standard shaft seal
[kW]
HQQE 0.37 - 45
HBQE 55-75
HQQV 0.37 - 45
HBQV 55-75
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
Note
periodical noise and reduced pump life.
CR, CRI, CRN pumps are not suitable for the pumping of liquids
above 120 °C for long periods.
H H
Q B
Q Q
E E
40 60 80 100 120 140
t [°C]
Max. temperature range
[°C]
-40 - 120 °C
0-120 °C
-20 - 90 °C
0-90 °C

5.4 Minimum inlet pressure

Hf
H
Pb
Fig. 4 Schematic view of open system with a CR pump
Calculate the maximum suction lift "H" in metres head as follows:
H = p x 10.2 - NPSH - H
b
p = Barometric pressure in bar.
b
Barometric pressure can be set to 1 bar.
In closed systems, p
b
bar.
NPSH = Net Positive Suction Head in metres head.
To be read from the NPSH curve on page
highest flow the pump will be delivering.
H = Friction loss in inlet pipe in metres head at the highest
f
flow the pump will be delivering.
H = Vapour pressure in metres head, see fig. E on page
v
336. t = liquid temperature.
m
H = Safety margin = minimum 0.5 metres head.
s
If the calculated "H" is positive, the pump can operate at a suction
lift of maximum "H" metres head.
If the calculated "H" is negative, an inlet pressure of minimum "H"
metres head is required. There must be a pressure equal to the
calculated "H" during operation.
Example
p = 1 bar.
b
Pump type: CR 15, 50 Hz.
3
Flow rate: 15 m /h.
NPSH (from page 331): 1.1 metres head.
H = 3.0 metres head.
f
Liquid temperature: +60 °C.
H (from fig. E, page 336): 2.1 metres head.
v
H = p x 10.2 - NPSH - H - H
b f v
H = 1 x 10.2 - 1.1 - 3.0 - 2.1 - 0.5 = 3.5 metres head.
This means that the pump can operate at a suction lift of
maximum 3.5 metres head.
Pressure calculated in bar: 3.5 x 0.0981 = 0.343 bar.
Pressure calculated in kPa: 3.5 x 9.81 = 34.3 kPa.
5.5 Minimum inlet pressure
The table on page 334 states the maximum permissible inlet
pressure. However, the actual inlet pressure + maximum pump
pressure (at no flow) must always be lower than the values stated
in fig. A, page 333.
The pumps are pressure-tested at a pressure of 1.5 times the
values stated in fig. B, page 334.
NPSH
Hv
- H - H
f v s
indicates the system pressure in
331 at the
- H [metres head].
s
7