Exercise A
55
between 1350ml/min and 1450ml/min then the pressure regulator will need adjusting
as follows:
Pull the large grey knob on the pressure regulator away from the body of the
regulator.
Gradually turn the knob to adjust the pressure regulator setting until the flow rate is
approximately 1400ml/min. Clockwise rotation opens the valve, anticlockwise rotation
closes the valve.
Depending on variations in the local water pressure, the flow rate figure may
oscillate.
If local water pressure is low then a lower value than 1400ml/min may be set. Where
this is the case, always set a value slightly lower than the maximum flow rate to
protect against spikes in pressure.
Push the knob back in to fix the setting.
Note: If the flow rate exceeds 1500ml/min then the flow meter may give a reading of
0ml/min. The flow meter is not designed to read flow rate values of greater than
1500ml/min. The regulator valve must be closed to reduce the flow below this value.
On the lid of the large process vessel, loosen the locking nut at the top of the level
switch and adjust the height of the switch to a suitable starting value. An initial value
of approximately 200mm is suggested.
Partially close the drain valve at the base of the large process vessel, limiting flow out
of the vessel.
In the Sample/Configure menu of the software, check that data logging is set to
automatic at intervals of five seconds. Check that the pressure reading L1 is varying
with the rising water levels. In the On/Off – Solenoid 1 box, select the radio button for
‘Level (Float) Switch’ control.
Select the
icon to begin data logging.
Observe that the large process vessel fills with water until the fluid level reaches the
level switch. Observe the action of the level switch as the fluid level rises further.
Note the position of the switch when SOL 1 is closed by the control software.
Observe the action of the level switch as the fluid level falls once more, and note the
position of the switch when the control software allows SOL 1 to open again.
Continue logging until the oscillations in fluid level reach stable values for magnitude
(height) and duration. Select the
icon to finish data logging.
Disturbances
Within the software it is possible to introduce disturbances in the outflow from the
vessel by opening the Normally Closed solenoid valves SOL 2 and SOL 3:
Following the previous section of this experiment, create a new results sheet by
selecting the
icon in the tool bar of the software.
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