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Exercise A - On/off level switch
Objective
To control the level in the process vessel using an on/off level switch with a Normally
Closed solenoid valve (SOL1) controlling inflow to the vessel.
Overview
The on/off level switch used for this exercise is a float switch, i.e. a vertical probe with
a moving float which rises with the water level until it closes the circuit of the switch.
This activates an on/off valve to control the flow into the process vessel.
Equipment Required
PCT40 bench with large process vessel, inner cylinder and supplied flexible tubing.
Equipment set up
Ensure that the apparatus has been set up according to the Installation section.
Ensure that the inlet connector for the apparatus (on the right of the plinth behind the
pressure regulator) is connected to a suitable mains water supply. Check that the
central cylinder is securely in position inside large process vessel. Using a suitable
length of tubing, connect the self-sealing connection socket on the base of the large
process vessel to the quick release connection on the valve SOL1 at the front right of
the plinth.
The drain valve at the end of the plinth should be directed to a drain and left open.
Solenoid valves 2 and 3 should be connected to a suitable drain using the tubing
supplied. The drain valve in the base of the large process vessel should also be
connected directly to drain using flexible tubing.
Connect the apparatus to a suitable PC on which the software has been installed
using the pale grey USB cable supplied. The flat connector on the cable connects to
the PC, usually via a socket at the back. The other end connects to the socket on the
orange panel on the front of the plinth. Check that the PC is working and switched
on.
Procedure
Switch on mains power to the console. The apparatus must not be left unattended
once in operation. Manual operation of the inlet pressure regulator and the drain
valves should be used to control the fluid level if the vessel volume reaches the
overflow pipe or the drainage channel in the plinth becomes full of water.
Run the PCT40 software and select Section 1: Level Control (inflow). Select the
icon to view the mimic diagram screen.
Open the valve SOL1 and allow water into the process vessel, as follows: Check that
the ‘Controller’ radio button is selected in the On/Off – Solenoid 1 box on the left of
the screen. Select ‘Control’ below the Tank Level sensor display, to open the PID
controller window. Choose ‘Manual’ Mode of Operation, then set ‘Manual Output’ to
100% and click on ‘Apply’. There should be an audible click as the valve opens, and
water should begin to flow into the process vessel. Close the PID controller window.
Open the drain valve in the base of the vessel to allow water to drain from the vessel.
Check the flow rate with the reading from the flow meter. If the flow rate is not
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