Exercise DD
183
Watch as water flows into the small process vessel. Once the fluid level reaches the
level sensor probe, set the PSV valve to 0%.
Detach the tube from the small process vessel and connect it to the gear pump inlet
(right hand socket).
Procedure
Click on the ‘PID’ button beside the PSV valve on the software screen.
Select the Manual Control radio button in the top right section of the PID control
window
In the bottom right section, set the pump speed to 50%. Close the PID control
window.
On the software screen, set the gear pump to 50%.
Adjust the pressure regulator on the inlet pipe of the apparatus to set the median flow
rate:
Gradually turn the grey knob to adjust the pressure regulator setting until the flow
rate F1 is approximately 750 l/min. Clockwise rotation opens the valve (increases
flow), anticlockwise rotation closes the valve (decreases flow).
Depending on variations in the local water pressure, the flow rate figure may
oscillate.
Push the knob back in to fix the setting.
Check that water is flowing through the manifold black and out to drain.
Select ‘Configure...’ from the Sample menu. Set data logging to Automatic at 5
second intervals with Continuous duration.
Manual control of static line pressure
Select the icon to begin data logging.
Click on the ‘PID’ button beside the PSV valve on the software screen.
Check that the Manual Control radio button in the top right section of the PID control
window is selected.
Monitoring the differential pressure P3, adjust the setting of the PSV in the bottom
right hand section of the PID control window, to give a flow rate of 700ml/min. Note
the pressure differential across the orifice at this flow rate (this is likely to be in the
region of 150mm to 200mm). Pick a set point value close to this pressure differential
(e.g. 150mm or 200mm), and attempt to reach and maintain this set point by
controlling the setting of the PSV.
If the signal oscillates too much (there is too much noise) to be able to easily monitor
the pressure differential, it may be necessary to use filtering in order to average out
the signal. Filtering can be set in the Options menu under ‘IFD Sampling
Parameters’. Depending on local conditions, Linear or Constant filtering is probably
the most appropriate, but if this delays the response too much then Exponential may
be a better choice.
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