Operating Conditions - Grundfos Hydro Multi-E Montage- Und Betriebsanleitung

5. Operating conditions

5.1 Temperatures
5.1.1 Ambient temperature
At ambient temperatures ranging from 0 °C to +40 °C, the motors
may be loaded 100 %. If the pumps are to be operated at higher
ambient temperatures or at altitudes above 1000 meters above
sea level, see installation and operating instructions for the pump.
5.1.2 Liquid temperature
0 °C to +60 °C.
5.1.3 Temperature during storage and transportation
-40 °C to +60 °C.
5.2 Relative air humidity
Maximum 95 %.
5.3 Maximum operating pressure
The maximum operating pressure for Hydro Multi-E is 10 bar.
For the following pumps, however, the maximum operating
pressure is 16 bar:
• CME-I 5-6
• CME-I 5-8
• CR(I)E 3-15
• CR(I)E 5-16
• CR(I)E 10-9
• CR(I)E 15-7.
5.4 Shaft seal run-in
The seal faces are lubricated by the pumped liquid, meaning that
there may be a certain amount of leakage from the shaft seal.
When the pump is started up for the first time, or when a new
shaft seal is installed, a certain run-in period is required before
the leakage is reduced to an acceptable level. The time required
for this depends on the operating conditions, i.e. every time the
operating conditions change, a new run-in period will be started.
Under normal conditions, the leaking liquid will evaporate. As a
result, no leakage will be detected.
5.5 Minimum inlet pressure
Hydro Multi-E systems with CME pumps require a
Caution
positive inlet pressure during start-up and
operation.
H
f
Hf
H
H
p
Pb b
Fig. 3 Parameters for the calculation of minimum inlet
pressure
6
NPSH
NPSH
H
Hv
v
The minimum inlet pressure "H" in metres head required to avoid
cavitation in the pumps can be calculated as follows:
H = p x 10.2 - NPSH - H - H
b f v
p = Barometric pressure in bar.
b
(Barometric pressure can be set to 1 bar.)
In closed systems, p
bar.
NPSH = Net Positive Suction Head in metres head
(to be read from the NPSH curve on page
highest flow the individual pump will be delivering).
H = Friction loss in suction manifold in metres head at the
f
highest flow the individual pump will be delivering.
H = Vapour pressure in metres head, see page 427.
v
t = liquid temperature.
m
H = Safety margin = minimum 0.5 metres head.
s
If the calculated "H" is positive, the individual 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: CRE 15, 50 Hz.
3
Flow rate: 15 m /h.
NPSH (from page 425): 1.2 metres head.
H = 3.0 metres head.
f
Liquid temperature: +60 °C.
H (from page 427): 2.1 metres head.
v
H = p x 10.2 - NPSH - H - H
b f v
H = 1 x 10.2 - 1.2 - 3.0 - 2.1 - 0.5 = 2.8 metres head.
This means that each pump can operate at a suction lift of
maximum 2.8 metres head.
Pressure calculated in bar: 2.8 x 0.0981 = 0.27.
Pressure calculated in kPa: 2.8 x 9.81 = 27.4.
5.6 Maximum inlet pressure
The maximum inlet pressure must not exceed 8 bar. However, the
actual inlet pressure + pressure when the pump is operating
against a closed valve must always be lower than the maximum
operating pressure.
5.7 Minimum flow rate
Due to the risk of overheating, the pumps should not be used at
flows below 10 % of the rated flow of one pump.
The pumps must not run against a closed
Note
discharge valve.
5.8 Start/stop
The system must not be started and stopped via the mains supply
more than four times per hour.
When the system is switched on via the mains supply, it will start
after approx. 5 seconds.
5.9 Diaphragm tank
The diaphragm tank precharge pressure has been set to
0.7 x setpoint.
The factory-set setpoint is 0.5 x maximum pressure unless
otherwise specified in the quick guide supplied with the
Hydro Multi-E.
If the setpoint is changed, the diaphragm tank precharge
pressure should be changed accordingly to ensure optimum
operation.
Calculate the precharge pressure as follows:
Precharge pressure = 0.7 x setpoint.
Measure the precharge pressure while the
Note
system is pressureless.
We recommend to use nitrogen gas for precharging.
- H
s
indicates the system pressure in
b
425 at the
- H [metres head].
s