Endress+Hauser Liquisys M CPM223 - Neutralization Controller; Neutralization Control Process

Liquisys M CPM223/253 Commissioning
Endress+Hauser 61
Neutralization controller
During neutralization control, the pH value of a medium is kept constant by dosing acid and
alkali. Two separate actuating signals are required for this task, one for acid and one for
alkali.
The neutralization controller is a controller with two relay contacts and is specially designed
for this task. The P(ID) controller is available as the controller.
The values for the control gain K
p
for acid and alkali can be set separately. Integral action
time T
n
and derivative action time T
v
apply to both controllers (see "P(ID) controller" section).
The "neutral Zone" is located between the set values 1 and 2. There is no acid or alkali dosing
(Y = 0, see Fig. 44) in the "neutral zone" with a controller without integral components (P,
PD). In the case of a controller with an integral component (PI, PID), there is constant alkali/
acid dosing (Y
new
=Y
old
). The behaviour of the I-component within the neutral zone depends
on the process type (inline/batch).
The "neutral zone" can be shifted as desired in the X direction via set point 1 and 2.
Neutralisation control is only possible with relays 1 and 2.
a0006793
Fig. 43: Sequence of a cleaning cycle
A
B
C
0
1
Hold
Water
Cleaner
Contact on
Contact off
t
0
t
1
t
2
-t
1
t
3
-t
2
t
4
-t
3
t
5
-t
4
Normal mode
Cleaning start
Pre-rinse time
Cleaning time
Post rinse time
Hold dwell period
C07-CxM2x3xx-05-06-00-xx-009.eps
Fig. 44: Control characteristic of a proportional neutralization controller
1
2
3
Neutral zone
Set point 1
Set point
4
5
6
Set point 2
Control contact 1 for alkali
Control contact 2 for acid
A
B
C
t
0
t
1
t
2
t
3
t
4
t
5
0
0
0
1
1
1
Y [%]
X
100
50
0
1
2
3
4
5
6