Exercise T
135
In the software, increase the PSV value using the arrow keys until the water level in
the process vessel is stable and covers the coil. Adjust the drain valve so that the
water level in the vessel remains constant and covers the coil at a PSV setting of
approximately 50%. The apparatus should not be left unattended, to ensure the
process vessel does not overflow or run dry.
Procedure
SAFETY NOTE: During this exercise the apparatus may reach temperatures hot
enough to cause burns or scalds. Do not touch the process vessel during the
exercise, or remove the coil or sensors from within the vessel. Allow the apparatus to
cool before draining the water or disconnecting any of the tubes from the process
vessel.
Run the PCT40 software. Select ‘Configure’ from the Sample menu and set sampling
to Automatic with sample intervals of 30 seconds and a duration of Continuous.
Fixed (manually set) ratio
In the PCT40 software, select ‘Control’ to open the PID controller window.
Set P, I and D to 0.
In Manual Control set the percentage time during which the heater will be on. 50% is
suggested as a starting value
At the bottom left, set the Cycle Time to 10s- this is the time over which the control
percentage will be applied (i.e. for a percentage of 50% and a cycle time of 10s, the
heater will be switched on for 5s and switched off for 5s).
Select the Manual Control radio button and click on ‘Apply’. The heater should begin
to operate intermittently as the time proportional controller sends signals to control it.
Check that there is a new data sheet for data logging.
Select the
icon to begin data logging, and observe the temperature in the vessel,
T1. When the temperature has changed by more than 20 °C, select the
icon to
finish data logging.
Adjust the control percentage according to the change in temperature. If the change
was rapid, reduce the setting by 25 to 30%. If it was gradual, reduce the value by 10
or 15%.
Continue to monitor the temperature and adjust the percentage value until the
temperature maintains a constant level.
Create a new results sheet by selecting the
icon in the tool bar of the software.
Select the
icon to begin data logging, and log the temperature T1 for a few
minutes. Select the
icon to finish data logging.
Make a note of the settings used.
Open the controller window and set Mode of Operation to Off.
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