Technical Data; Ambient Temperature; Liquid Temperature; Maximum Permissible Operating Pressure And Liquid Temperature For The Shaft Seal - Grundfos CR Serie Montage- Und Betriebsanleitung

4. Technical data

4.1 Ambient temperature

Maximum +40°C.
If the ambient temperature exceeds +40°C or if the motor is lo-
cated 1000 metres above sea level, the motor output (P2) must
be reduced due to the low density and consequently low cooling
effect of the air. In such cases, it may be necessary to use a mo-
tor 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 66, which indicates the relationship between liq-
uid 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
-40 -20 0 20 40

4.4 Minimum inlet pressure

Fig. 3
Hf
H
Pb
t [°C]
3500 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 64 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
70. 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 64): 1.1 metres head.
H = 3.0 metres head.
f
Liquid temperature: +60°C.
H (from fig. E, page 70): 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 68, 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 68.

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 11 kW: Maximum 300 times per hour.
Other motors: Maximum 200 times per hour.
– H
v s
indicates the system pressure
b
– H [metres head].
v s
t [°C]
9