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Practice missions
Mission 17 · Pro PLC fault-finding exercise

The pump chatters

Look at the trend before you change the 30% or 70% limits.

Put back the missing fill memory, so the pump remembers it is filling. Start PumpOn below 30%. Keep filling between 30% and 70%, and stop at 70%. Without Permit, PumpOn must be off, but the remembered demand must not be lost.

This mission is part of ProTry the full course, every mission and the expert challenges free for 7 days. No card needed.
The 3D process tank this mission runs on Pro mission
Test replay

Operator recording: noise around 30%

Test 1 of 7
Set by the testChecked by the testStep 9 of 9 · 720 ms
Level
Applied
Time
About 12 min
Reward
+200 XP
Rig
3D process tank
Siemens editors
FBD
Rockwell editors
FBD
Course stage
7. Keep control steady
The operator’s report · process tank
P-101 kicks in below 30%, then drops out as soon as the level creeps over 30%. The reading wobbles between 29.8% and 30.3%, so the pump keeps starting and stopping. It never gets the tank up to 70%.
Automatic tests

What the tests check

  1. A wobbly reading around 30% must not stop a fill that has started.
  2. After 70%, the pump stays off until the level drops below 30%.
  3. With Permit off, the pump is off on every .
  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 caretaker hears the tank-filling pump start, stop and start again. The water level is barely changing.

Repeated starts heat the motor and wear its parts. Watch the level and the pump command together to find what causes each change.

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.

Keep going

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