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12.6
Metering rates
Repeatable metering accuracy is approx. ± 3 % at minimum 30 % stroke length and
otherwise constant conditions. In order to balance the clearance, the stroke length adjustment
has to be based on the lower value towards the desired stroke length (= sense of rotation to the
right).
Due to the characteristics of the pump, higher output can be produced until the operating
temperature is reached.
Precise metering can be achieved provided the following items are adhered to:
a)
All metering-rate data is referred to measurements using water at 20° C, constant
supply voltage and the metering pump at operating temperature.
b)
A pressure-maintenance valve (or metering valve) for generation of the most constant
possible counter pressure of not less than 0.5 bar should be used in order to obtain
high metering accuracy in case of metering with unobstructed discharge.
c)
If there is pre-pressure on the suction side, the pressure difference between the suction
and the pressure sides must be at least 1 bar. The water column on the metering pump
must be protected by an appropriate valve arrangement.
NOTE
ATTENTION
12.7
Delivery capacity in relation to the back pressure
Setting accuracy + 15 % - 5 % of the nominal value; all data relate to water at 20 °C and
comply with the notes in the operating instructions.
NOTE
Fig. 12.8
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
417101338_EMPKKS.doc
A pressure control valve or a metering value is not an absolutely hermetically sealing
shutoff device.
Metering stroke adjustment may only be performed with the pump running if the stroke
adjusting screw is released.
The tender specifications are shown at a pump frequency of 50 Hz.
2
3
4
5
6
Back pressure (bar)
69
7
8
9
Rev: 08-01.10
10
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