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Mission 28 · Pro PLC sequence recovery exercise

Recover the Interrupted Batch

Pause the batch safely. Restart it on purpose.

Start AND Permit starts filling: PumpOn and FillValve turn ON. Hold or Fault moves to the Batch held step and turns both OFF. This wins even if the tank reaches 70% at the same moment. Resume restarts filling only once Hold and Fault are both OFF. Level >= 70 moves to Complete: Done ON, PumpOn and FillValve OFF. MixerOn and DrainValve stay OFF throughout.

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The 3D process tank this mission runs on Pro mission
Test replay

Hold stops filling; only Resume restarts it

Test 1 of 5
Set by the testChecked by the testStep 5 of 5 · 220 ms
Level
Advanced
Time
About 18 min
Reward
+300 XP
Rig
3D process tank
Siemens editors
GRAPH
Rockwell editors
SFC
Course stage
15. Prove a safe recovery
Automatic tests

What the tests check

  1. Hold or Fault moves to Batch held.
  2. Batch held never restarts on its own.
  3. Resume works only after Hold and Fault are both OFF.
  4. A full tank (Level >= 70) completes the batch.
  1. Try it Use the buttons below the model and watch the rig respond.
  2. Test solution Every check runs on your code in one press.
  3. Replay If one fails, step through it one scan at a time to see why.
Why it matters

Where you’d see this on site

A drinks operator puts a batch on hold to look at a filling problem. Fixing the problem must not restart the equipment by itself.

A surprise restart can spill liquid while the operator is checking the tank. Resume must be a deliberate press, and must not work while the fault remains.

Where you'd find thisMaking one batch of drink

At a drinks factory, valves let measured amounts of water and syrup into a mixing tank. An electric mixer blends them into one batch. An outlet valve then sends the drink to a holding tank. Filling machines bottle it from there.

  1. Ingredient tanksHold the water and syrup
  2. Mixing tankFill, mix and measure one batchYou are here
  3. Holding tankKeeps the finished drink ready
  4. Bottle fillerPuts the drink into bottles
On a real site: places, parts and safety
  • Drinks factory — blending water and syrup
  • Paint factory — mixing ingredients into a consistent colour
  • Water-treatment works — preparing a measured chemical mixture
  • Brewery — heating water for washing equipment

A full tank does not close its own inlet. Water keeps arriving until the valve closes, so an open inlet can flood the room.

A heater that is not covered by liquid can overheat. Real tanks have separate safety devices as well as the PLC programme.

The sizes, timings and cutaways are teaching choices, not a drawing of any one real installation.

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