101
New Brunswick Scientific
User’s Guide
Figure 61: Typical Liquid Addition System
16.2.1
Addition Tubing Size
pH can be controlled by automatic additions of liquid acid and base. Additions
are triggered by the BioFlo 415 controller, which is constantly comparing
current pH value with the pH setpoint and making adjustments as necessary.
The concentrations of acid and base, and the inner diameter of the acid and
base addition tubing (where they pass through the peristaltic pumps), are
critical parameters in the proper operation of a P&I pH control system. If the
tubing is too large, excessive doses will be added. The result is that the system
will “overcontrol,” alternating in close succession between adding one liquid,
then the other, providing little or no change in pH reading. A user-selected
deadband value is an aid to control pH within the user-assigned range: no acid
or base will be added when the pH value falls within the deadband tolerance
above or below the setpoint.
PERISTALTIC
PUMP
ADDITION
BOTTLE
BREATHING
PORT with
STERILE
FILTER
(0.2 µ)
ADDITION
PORT
TUBING
PLASTIC
TIES
Содержание BioFlo 415
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