Grundfos DME 2 Product Manual page 15

Functions
Anti-cavitation (60 to 940)
The pump features an anti-cavitation function. When
this function is selected, the pump extends and
smoothes its suction stroke, resulting in softer priming.
The anti-cavitation function is used:
• when pumping liquids of high viscosity,
• in the case of a long suction tube and
• in the case of a high suction lift.
Depending on the circumstances, during the suction
stroke, the motor speed can be reduced by 75%, 50%
or 25% compared to the normal motor speed during the
suction stroke.
The maximum pump capacity is reduced when the anti-
cavitation function is selected
Anti-cav max capacity (DME 60 to 150)
DME 60 to 940
DME Max cap. 75%
60 g/h. (l/h) 15.9. (60) 11.9. (45)
150 g/h. (l/h) 39.6. (150) 29.6. (112)
375 g/h. (l/h) 99.1. (375) 74.2. (281)
940 g/h. (l/h) 248.3. (940) 186.2. (705) 124.2. (470) 62.1. (235)
Maximum capacity limitation
Applies to DME
This function offers the possibility of reducing the
maximum capacity (MAX. CAP). It influences the func-
tions in which the pump is normally operating at
maximum capacity. Under normal operating conditions,
the pump cannot operate at a capacity higher than the
one stated in the display. This does not apply to the
priming button.
By means of this function, a large pump can be set to
act as a much smaller pump. Together with the 1:1000/
1:800 capacity range, the purposes of this function are:
1. To utilize the smooth and even dosing characteris-
tics of the pump at low capacities to achieve
– improved chemical mixing,
– improved dosing through long discharge tubes and
– improved dosing of high-viscous liquids.
2. To improve the dosing of gas-containing liquids: In a
large pump, as compared to a small pump, the dis-
placed volume (1) is much larger than the non-dis-
placed volume (2).
3. To cover several needs with just one pump size.
4. To adapt the pump to a 4-20 mA signal control with
In this way it is possible for instance to use a DME 48
for dosing a very small quantity of liquid without
changing the input signal. See example below.
50% 25%
Example:
7.9. (30) 4.0. (15)
A DME 48 receives a 12 mA input signal from a control
19.8. (75) 10.0. (38)
instrument, resulting in a 50% output (according to the
49.7. (188) 24.8. (94)
analog curve on page 13) and a capacity of 24 l/h. A
new situation occurs where it is only necessary to dose
2 l/h. The maximum capacity limitation is set to 4 l/h.
The pump is still receiving a 12 mA signal resulting in a
50% output and a capacity of 2 l/h.
The maximum capacity limitation will also reduce the
pump speed in timer-based batch control, pulse-based
batch control and during calibration where the pump is
usually operating at maximum capacity.
Calibration
After start-up, the dosing pumps can be calibrated to
the actual installation to ensure that the displayed value
(milliliters or liters) is correct. A calibration program in
the main menu facilitates this process.
1
2
2
Small pump Large pump
4 mA corresponding to 0% and 20 mA to the set
maximum capacity.
Q Q
[US GPH] [l/h]
48
12
44
11
40
10
36
9
32
8
28
7
24
6
20
5
16
4
12
3
8
2
1 4
0 0
0 4 8 12
DME and DMS
1
16 20
[mA]
15