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.
- On start up, TANK 1 valve is open.
- When TANK 1 low level (set-point 1) operates, TANK 1 valve closes and TANK 2 valve opens.
- The system is now operating from TANK 2.
- TANK 1 is replaced, TANK 1 low level alarm is now OFF.
- When TANK 2 low level alarm operates, TANK 2 valve is closed and TANK 1 valve is opened.
- 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:
- If both tanks above their low setpoint then display tANk 1
- 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
- If TANK 1 is replaced therefore no low alarms display then tANk2
- 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
- If TANK 2 is replaced therefore no alarms display tANk1
- If both tanks are low the display will scroll tANk1 Lo tANk2 Lo
TANK LEVEL MACRO
The example macro has been written to
- Automate the valve position and therefore the tank in use.
- Scroll across the display appropriate text message indicating the condition of the tanks and valves.