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Mission 45 · Pro PLC programming exercise

Take turns, survive the storm

Alternate two pumps and bring in the standby.

Empty the wet well from the high float to the low float with one pump, swap pumps every cycle, and use both in a storm.

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

Two cycles, two pumps

Test 1 of 3
Set by the testChecked by the testStep 10 of 10 · 540 ms
Level
Applied
Time
About 25 min
Reward
+300 XP
Rig
3D duty standby sump pumping station
Siemens editors
SCL, LAD
Rockwell editors
Structured Text, Ladder
Course stage
26. Machine lab 1: real machines, clear rules
Automatic tests

What the tests check

  1. A cycle starts at FloatHigh and ends when FloatLow turns OFF.
  2. Only the duty pump runs in a normal cycle.
  3. The duty pump swaps at the end of every cycle.
  4. At FloatHighHigh both healthy pumps run and HighAlarm is ON.
  5. A tripped pump is never started; the healthy one takes over.
  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

Water companies run thousands of stations like this, often unmanned and watched only by telemetry.

A station that always starts the same pump wears it out while the other seizes from disuse; one that cannot bring in the standby floods streets and basements.

Where you'd find thisKeep the wet well from overflowing, and wear both pumps evenly

Underground car parks, basements and sewage networks drain into sumps like this. Two pumps are fitted so one can fail without a flood. Swapping the duty pump each cycle shares the running hours, and both run together in a storm.

  1. InflowDrains and rain
  2. Wet wellFloats measure the levelYou are here
  3. PumpsDuty, then standby
  4. Rising mainTo the sewer
On a real site: places, parts and safety
  • Basements, underpasses and car parks
  • Sewage and surface-water pumping stations
  • Factory drainage and wash-down sumps

Wet wells are confined spaces with toxic gases: lift pumps out on their rails instead of going in.

A high-high alarm must reach a person, not just a lamp, because the next step is a flood.

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

Keep going

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