NEW BRUNSWICK SCIENTIFIC BioFlo 4500, Manual To Operations

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BioFlo 4500 M1254-0050 User’s Guide
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The loop called
AIRFLOW
in Section on the Air System is the
GAS1
loop in four-gas
applications. It is configured exactly the same way.
The
GAS2
loop is very similar, but there are changes in the Input Device and Output
Device. The PID values also differ loop to loop. For more specific details about four-gas
control, see Section 13.5 below.
13.1 Setting Up the Two-, Three- or Four-Gas Mixer Option
Typically, the two-gas mixer is used to supplement the air stream with pure oxygen
to meet the huge oxygen requirements of high density cell cultures. The three-gas
mixer is often used to mix Air, O
2
, and CO
2
or N
2
to provide the appropriate
conditions for interactive pH & DO, central to feed batch mode. With the built-in
four-gas controller, N
2
, O
2
, CO
2
, and air are mixed to provide interactive control of
pH and DO in batch or perfusion modes.
With the Gas Mix controller output type selected, the controller mixes
combinations of air, oxygen, nitrogen and carbon dioxide as required to control DO
and pH. A constant gas flow rate is maintained during this process. The
composition of the gas mixture is determined by the duty cycle of the solenoid
valves which control the flow of the respective gases. The time required to cycle
once through all four valves is called the Pulse Width Modulation Period or PWM
Period. It is typically set to 10 seconds, but the time period can be made shorter for
smoother control, or longer for extended valve life.
The gas mix control mode is determined by the controller output action and the
presence of a cascade input to the loop:
Control
Mode
Cascade
Input
Output
Action
Gases
Mixed Application
2-Gas No Direct Air and O
2
Oxygen enrichment
2-Gas Yes 2 Ch Comp Air and O
2
Cascade-driven oxygen
enrichment
3-Gas No Center Off Air, N
2
and O
2
Bi-directional DO Control
3-Gas Yes Direct Air, O
2
, and CO
2
Oxygen enrichment w/ CO
2
addition for pH control
4-Gas Yes Center Off Air, N
2
, O
2
, and
CO
2
Bi-directional DO Control w/
CO
2
addition for pH control
WARNING!
Gases used in 2-, 3- and 4-gas mixing must be oil-free,
must be particulate-free, and must meet 85% relative humidity
requirements.