42
CORN I NG ASCENT FBR PD SYSTEM
Figure 7-24.
Graphing tuning window and
auto-tune window.
Figure 7-24 is the PID auto-tuning window. This is a standard function supplied with the PID control loops. This functionality shall be used
by a training controls engineer familiar with the Rockwell PID auto-tuner.
NOTE:
Corning cannot guarantee the performance of this function nor the response of the system.
7.9 Control Loop Setup
This section describes the three screens that set up to control MCV and FBR DO, pH, and O
2
levels.
7.9.1 MCV DO Control
The MCV DO faceplate (Figure 7-25) allows the user to control MCV DO percentage by manipulating O
2
, air, mass flow controllers, and
agitator speed setpoints. Refer to Table 7-12 for details. Graphical representations are in Section 7.9.1.1.
Table 7-12.
MCV DO Control faceplate descriptions.
Label
Description
1
The DO Controller Value (CV) column represents the
output of the control loop in percent (%). The higher the
demand for oxygen for cell growth, the higher the DO
CV.
2
The three columns: O
2
%, Total Flow and Agitator
represent the three factors that affect MCV DO
concentration.
• O
2
% = Oxygen concentration in the sparge gas
mixture controlled by adjusting the air, O
2
and N
2
flow ratios and accounting for the CO
2
flow from pH
control loop.
• Total Flow (SCCM) = The sparge gas flow rate in
standard cubic centimeters/min. calculated as air +
O
2
+ N
2
+ CO
2
flow.
• Agitator = This refers to the agitator speed in rpm.
3
The gray top row indicates each output actual values at
the current time.
4
The P, I ,and D gains control how quickly the loop acts to
adjust the DO CV value if the measured DO % deviates
from the user setpoint.
NOTE:
The vast majority of applications will be best served by leaving the D-Gain at zero for the MCV DO controller configuration.
NOTE:
If user inputs Total Flow setpoints that exceed the systems ability to deliver the desired concentrations of O
2
(or CO
2
for the pH loop),
MCV DO control will not behave predictably. This is due to calculations being based on the requested total flow setpoint, even if total flow
cannot be met by the flow controllers. Care must be taken to avoid requesting total gas flows that exceed the flow controller capacities.
7.9.1.1 MCV DO Control Loop Configuration Examples
This section provides graphical representations for several MCV DO Control Loop configurations. Figures 7-26 to 7-29 represent examples
of 3-Gas (Air, O
2
, CO
2
) MCV DO Loop Configurations with variations in DO management strategies.
Figure 7-30 contains an example of a 4-Gas (air, O
2
or N
2
, CO
2
) DO control strategy to enable MCV DO operation below 20% to 21%.
NOTE:
PID controllers are inherently linear, meaning they do not handle large non-linearities in process or control outputs optimally,
making it difficult to tune control loops for all conditions. Generally speaking, configuring the control loops with uniform (linear) steps
between output levels (Figure 7-25) will provide the best results over a wide range of conditions when the system is connected to three
gasses only (air, oxygen, and CO
2
). In this case, the process will start at 100% DO in the MCV vessel.
Figure 7-25.
MCV DO Control.
