Exercise V
147
Set the gear pump back to 0%.
Disturbances
Within the software it is possible to introduce disturbances in the temperature inside
the process vessel by changing the flowrate of water through the coil:
Select the
icon to begin data logging.
In the software, increase the PSV setting by 20%. Open the drain valve at the base
of the process vessel enough to balance the flow in and out of the vessel, so that the
fluid level in the vessel remains constant.
Note the control action required to maintain the temperature within the vessel at the
new flow rate.
Increase the PSV setting by a further 20%, and open the drain valve more to
maintain the fluid level within the vessel.
Continue to control the temperature, noting the action required.
Set the PSV back to its original setting, close the drain valve, and continue to control
the temperature within the vessel.
Select the
icon to finish data logging.
Create a new results sheet by selecting the
icon.
Set the gear pump to 50% to circulate the hot water within the vessel, select the
icon to begin data logging, and repeat the investigation of the effect of disturbances.
Select the
icon to finish data logging.
Create a new results sheet by selecting the
icon.
Results
For easy identification or results, it is suggested that each results sheet is renamed
with a descriptive title (e.g. ‘Disturbances’, etc.). The entire workbook should be
saved with a suitable filename for future reference (e.g. PCT40 Exercise V).
Each set of data should be plotted on a graph of temperature T3 against time.
Write up your experiment, commenting on the heating and cooling characteristics of
continuous operation and the actions required for manual control of the heating
process. Give reasons for any time delay between applying a control action and
observing a response. Explain any difference between heating and cooling rate.
Comment on the effect of stirring. Give examples of industrial control situations in
which a step change in flow rate might occur.
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