A bakery customer has two tanks containing a release agent that is sprayed into the baking trays. If the release agent runs out, the bread sticks to the trays. Two release agent drums, TANK 1 and TANK 2 are placed onto two independent load-cell platforms and both load cell outputs are connected to a dual load-cell input module installed in a DI-60AT controller.

  1. On start up, TANK 1 valve is open.
  2. When TANK 1 low level (set-point 1) operates, TANK 1 valve closes and TANK 2 valve opens.
  3. The system is now operating from TANK 2.
  4. TANK 1 is replaced, TANK 1 low level alarm is now OFF.
  5. When TANK 2 low level alarm operates, TANK 2 valve is closed and TANK 1 valve is opened.
  6. The sequence is repeated.

The controller is programmed to scroll a text message across the display to indicate the tank in use, and when the tank low alarms are energized. For example:

  1. If both tanks above their low setpoint then display tANk 1
  2. If TANK 1 is below low setpoint controller will automatically open TANK 2 valve and close TANK 1 valve, the scrolling display then tANk 2 in use tANK 1 low
  3. If TANK 1 is replaced therefore no low alarms display then tANk2
  4. If TANK 2 is low, the controller will automatically open TANK 1 valve and close TANK 2 valve the display will then scroll tANK 1 in use tANK 2 low
  5. If TANK 2 is replaced therefore no alarms display tANk1
  6. If both tanks are low the display will scroll tANk1 Lo tANk2 Lo

38_Dual Tank Level Annunciator Controller

The example macro has been written to

  1. Automate the valve position and therefore the tank in use.
  2. Scroll across the display appropriate text message indicating the condition of the tanks and valves.