Armfield Instruction Manual
186
Set the PSV valve to 50% and slowly open the pressure regulator valve to achieve a
flow rate of 750 l/min.
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 1
second intervals with Continuous duration.
Set the PID values for the controller in the PID controller window. Suggested starting
values are a Set Point of 200mm, Proportional Band (P) of 50%, Integral Time
Constant (I) of 10s and Differential Time Constant (D) of 0s.
If the signal oscillates too much (there is too much noise) to be able to easily control
the flow rate, 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.
Select the
icon to begin data logging.
Log the pressure differential P3 until it settles to within a narrow range of the set
point, then select the
icon to stop logging.
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