Tank Level Control
This exercise is to control the fluid level in a tank to ensure sufficient supply to downstream facilities. It will be necessary to generate and control a series of alarms if the fluid level is too low or, on the contrary, when an overflow is about to occur.
The top section of the window shows the tank with four level sensors which check normal operation and fluid low/high level limits. Each sensor is energised whenever the fluid level in the tank exceeds its position. When one sensor is energised, the corresponding LED is lit.
The feed and the supply tubing are valve controlled. Selector switches allow various operating modes to be enabled: manual valve open; manual valve closed and automatic.
When in automatic mode, the position of the inlet tap valve is defined from the PLC output to which it is connected. The position of the outlet tap valve is randomly defined, in order to simulate the different fluid demand from downstream facilities.
The bottom section of the window contains a control and alarm panel;
two warning light indicators and a siren are available along with alarm reset and siren off buttons.
The Trend recorder window simulates an instrument that is common in industrial applications: a chart recorder. On graph paper, organised with percentage (vertical) versus time scale (horizontal), a dot representing the tank level is continuously plotted in real time. A level trend signal is then graphically displayed to allow evaluation off the effectiveness of any adjustments made.
When the available screen space is full, the window scrolls: last samples disappear and space is provided for new samples.