Burkert Type 8620 - Manual (Page 133)

mxCONTROL Type 8620
Page 133
The Figure 69 demonstrates the relationship between system water conductivity and biocide dosing.
Delay Tm1 Bleed lock-out Tm2
(Tm2 adjustable)
Time
Conductivity
Bleed
Biocide Dosing
Biocide Dosing Off
Biocide Dosing On
Bleed Valve open
Bleed Valve closed
Control limits of
Conductivity
Pre-bleed limit of
conductivity before
biocide dosing
(Main dosing
time: 2/3Tdose)
Time
Time
Biocide timer
starts pre-bleed
(time scheduled)
(Post dosing
Time: 1/3Tdose)
Dosing time Tdose
Figure 69: Strategy of biocide dosing
Rules for the biocide dosing:
● A new biocide dosing event will be only triggered, if the previous biocide dosing process on
this channel is finished. The new biocide dosing event in between expires.
● Both biocide dosing channels work independently.
● If a biocide dosing process is running on one channel and the second channel begins, too, the
internal status of the conductivity controller will not be changed:
● If the channel one has left the pre-bleed, the pre-bleed for the later starting second channel
will be skipped and the second channel will begin immediately with the dosing process.
● If channel one is in the pre-bleed phase and the second channel starts, too, the minimum of
the pre-bleed limits from both channels will be taken in order to determine the end of the
pre-bleed process. The max. duration of the pre-bleed phase is determined by the greater one
of the max. pre-bleed durations of both channels.
● If both biocide dosing channels are active, the control will return to the assigned
conductivity controller if both channels have finished the dosing process.
● If at least one of the digital inputs is configured as a binary input for system status or as a flow
switch and if at least one of these binary inputs gets or is active, all active biocide dosing
processes will be cancelled and no new biocide dosing events will be triggered and started.
Channel Output in Manual Mode
In manual Mode all active biocide dosing processes are cancelled. The control of biocide dosing is
assumed by the operator, who must now manually control the biocide dosing by operating the dosing
valves with soft keys on the „Type 8620 mxCONTROL“ (in the "Process Data" menu).