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Mission 53 · Pro PLC programming exercise

Purge, prove, fire

Write a burner management sequence that locks out on any doubt.

Light the boiler safely: prove air, purge at high fire for 15 s, light and prove a pilot within 5 s, establish the main flame, then fire high or low on steam pressure. Lock out at once on any flame, air or gas fault.

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The 3D burner management system this mission runs on Pro mission
Test replay

Light-off and firing

Test 1 of 6
Set by the testChecked by the testStep 19 of 19 · 35.4 s
Level
Advanced
Time
About 60 min
Reward
+750 XP
Rig
3D burner management system
Siemens editors
SCL, LAD
Rockwell editors
Structured Text, Ladder
Course stage
29. Machine lab 4: safety sequences and plant control
Automatic tests

What the tests check

  1. Air proven within 5 s, purge 15 s at high fire, back to low fire before ignition.
  2. 5 s pilot trial; no flame means lockout.
  3. Main flame with the pilot for 5 s, then pilot off; high/low fire on pressure.
  4. Flame lost, air lost, stray flame or low gas: gas off at once and lockout.
  5. Lockout post-purges for 10 s and waits for Reset.
  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

Every gas boiler, oven and dryer has a burner controller running this sequence. In industry they are certified safety devices, configured rather than programmed.

Gas in a furnace with no flame becomes an explosive mixture; the next spark finds it. The purge clears it, the trial-for-ignition limits how much can collect, and the lockout stops anyone simply retrying.

Where you'd find thisNever let gas into a furnace without a flame to burn it

Boilers, ovens and furnaces burn gas with a strict sequence: blow the furnace clear of gas, light a small pilot, prove it, then open the main gas. Any doubt about the flame and the gas is shut off and the burner locks out.

  1. PurgeAir at high fire
  2. PilotTrial for ignition
  3. Main flameProven, then runYou are here
  4. Steam8 bar to the plant
On a real site: places, parts and safety
  • Steam boilers in factories, hospitals and breweries
  • Process heaters, dryers and ovens
  • Thermal oxidisers and furnaces

Real burners use certified burner controllers or safety PLCs (EN 298, EN 746-2, NFPA 85/86). This mission teaches the sequence; it is not a design for a real burner.

A furnace that fills with gas and then finds a spark explodes. That is why the purge and the ignition trial are timed so strictly.

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

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