Burkert Type 8620 - Manual (Page 128)

mxCONTROL Type 8620
Page 128
14.8 Batch Dosing (BATCH)
The input signal for the batch controller is derived from one of the digital inputs, configured as a pulse
counter input.
The Batch dosing module is used to control a dosing pump (e.g. for inhibitors). A detected amount of
pulses (volume) leads to a dosing event
for predetermined time.
These modules are
explained below.
Figure 66: BATCH
Batch Controller in Automatic Mode
The incoming pulses at the assigned input are counted. The current number of incoming pulses is
scaled by the K-Factor of the assigned input. The result is the current batch size PV BSi which
corresponds to the number of incoming pulses since the last counter reset.
In the batch function the current batch size PV BSi is compared with the parameterized target batch
size (SP BSi)
. If the target batch size SP BSi is reached, the assigned output is energised for an
adjustable time and the counter of the incoming pulses will be reset.
The remaining dosing time will be displayed in the corresponding process data menu if the output is
energised.
Dosing start delay function
The parameter Tdelay delays the start of the dosing output when a dosing event occures.
This start delay function can be used to dose 2 chemicals (one after the other) with 2 BATCH control
functions dependent on one flow, for example.
In this case you must use the start delay to stagger dosing as required because there is no interlock
between control functions. You also have to ensure that there is sufficient time between Batch dosing
events for the Tdose and Tdelay. The reason therefor is: new dosing events during active start delay
or dosing process expire.
Example:
2 BATCH control functions Batch1 and Batch2 are connected to the same Flow input.
- Batch1: SP BSi = 1000 L (Makeup), Tdose = 600 sec, TDelay = 0 sec
- Batch2: SP BSi = 1000 L (Makeup), Tdose = 180 sec, TDelay = 660 sec
...
The output timer will be only energised if no dosing process is active on the assigned output.
A new dosing event is only triggered, if the previous dosing process was finished. New
dosing events in between expire.