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

4. Technical data

4.1 Ambient temperature

0.37-0.75 kW motors (EFF 2, MG):
1.1-11 kW motors (EFF 1, MG):
15-45 kW motors (EFF 1, Siemens):
If the ambient temperature exceeds above maximum values or if
the motor is located 1000 metres above sea level, the motor out-
put (P2) must be reduced due to the low density and conse-
quently low cooling effect of the air. In such cases, it may be
necessary to use a motor with a higher rated output.
Fig. 1
P2
[%]
100
90
80
70
60
50
20 25 30 35 40 45 50 55 60 65 70 75 80
1000 2250
Example:
Figure 1 shows that P2 must be reduced to 88% when the pump
is installed 3500 metres above sea level. At an ambient tempera-
ture of 70°C, P2 must be reduced to 78% of the rated output.

4.2 Liquid temperature

See fig. A, page 149, which indicates the relationship between
liquid temperature and maximum permissible operating pressure.
Note: The maximum permissible operating pressure and liquid
temperature ranges apply to the pump only.
4.3 Maximum permissible operating pressure and
liquid temperature for the shaft seal
Fig. 2
CR, CRI, CRN 1s to 20 and CR, CRN 32 to 90
p [bar]
35
30
25
H
20
Q
HQQE
Q
15
HQQV
E
10
5
0
-60 -40 -20 0 20 40

4.4 Minimum inlet pressure

Fig. 3
Hf
H
Pb
Max. +40°C.
Max. +60°C.
Max. +55°C.
EFF 1, Siemens
EFF 1, MG
EFF 2, MG
t [°C]
3500 4750 m
H
Q
Q
E
60 80 100 120 140
t [°C]
NPSH
Hv
The maximum suction lift "H" in metres head can be calculated as
follows:
H = p x 10.2 – NPSH – H – H
b f
p = Barometric pressure in bar.
b
(Barometric pressure can be set to 1 bar.)
In closed systems, p
in bar.
NPSH = Net Positive Suction Head in metres head
(to be read from the NPSH curve on page 147 at the
highest flow the pump will be delivering).
H = Friction loss in suction pipe in metres head at the
f
highest flow the pump will be delivering.
H = Vapour pressure in metres head, see fig. E on page
v
152. 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.
Flow rate: 15 m³/h.
NPSH (from page 147): 1.1 metres head.
H = 3.0 metres head.
f
Liquid temperature: +60°C.
H (from fig. E, page 152): 2.1 metres head.
v
H = p x 10.2 – NPSH – H – H
b f
H = 1 x 10.2 – 1.1 – 3.0 – 2.1 – 0.5 = 2.7 metres head.
This means that the pump can operate at a suction lift of maxi-
mum 2.7 metres head.
Pressure calculated in bar: 2.7 x 0.0981 = 0.265 bar.
Pressure calculated in kPa: 2.7 x 9.81 = 26.5 kPa.

4.5 Maximum inlet pressure

Figure B, page 150, shows the maximum permissible inlet pres-
sure. However, the actual inlet pressure + pressure when the
pump is running against a closed valve must always be lower
than the "maximum permissible operating pressure".
The pumps are pressure-tested at a pressure of 1.5 times the
value stated in fig. B, page 150.

4.6 Minimum flow rate

Due to the risk of overheating, the pump should not be used at
flows below the minimum flow rate.
The curve below shows the minimum flow rate as a percentage of
the nominal flow rate in relation to the liquid temperature.
– – – – = air-cooled top.
Fig. 4
Qmin
[%]
30
20
10
0
40 60 80 100 120 140 160 180
Note: The pump must never operate against a closed discharge
valve.

4.7 Electrical data

See motor nameplate.

4.8 Frequency of starts and stops

Motors up to and including 4 kW: Maximum 200 times per hour.
Motors of 5.5 kW and up: Maximum 100 times per hour.
– H
v s
indicates the system pressure
b
– H [metres head].
v s
t [°C]
15