Sartorius DCU 3, Operator'S Handbook Manual

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Operators Handbook DCU3 – System
6., Main function „Control Loops“
BAEDCU3 - Rev. 4.6 - 0504 6 - 22
6.14 Oxygen (O
2
) – Enrichment Using 2 Massflow Controllers
6.14.1 Functional Principles
The control method „O
2
-Enrichment using 2 massflow controllers“ acts in two phases, „Gasflow Total“
and „Gasflow Ratio“:
1. The pO
2
is controlled by air supply until a user definable maximum flowrate is achieved. For
this the DCU3 - system controls one massflow controller, which used for air supply. This
phase is specified as „Gasflow Total“ in the display of the controller.
2. If the oxygen demand exceeds the supply possible at maximum airflow rate, the input air
can be enriched by oxygen. While the total flowrate is kept constant at its maximum the
DCU3 - system reduces the flow rate of the massflow controller for air supply and triggers a
second massflow controller to add oxygen to the air inlet.
The increase of oxygen input is propertional to the decrease of air input. This phase is
specified as „Gasflow Ratio“ in the DCU - display of the controller.
The „O
2
-Enrichment“ control method can be extended by an additional control of other process pa-
rameters, such as the stirring speed.
6.14.2 Realization and Operation with the DCU3 - System
The “O
2
-Enrichment” control method is implemented as a „cascade control“. The pO
2
-controller acts as
the master controller. You will enter all settings, such as the controller mode, setpoint or intended
servo controller, in the menu of the pO
2
-controller.
See the description of the „pO
2
cascade controller“ for details on how to proceed.
The DCU3 - system automatically activates the „Gasflow-Total / Gasflow-Ratio“ - controller to operate
as servo controller.