Boiler Operation, Startup, and Shutdown Procedures
What this domain tests
This domain tests safe operating sequences from cold start through normal firing and controlled shutdown. Questions often ask for the next step, the purpose of warm-up, or the correct order of valve, damper, and fuel operations.
Pre-start checks
- Confirm water level at normal in the gauge glass; test try cocks.
- Open the drum vent on a cold or empty boiler so air leaves and pressure does not build prematurely.
- Check the fuel train for leaks, confirm combustion air, and verify draft.
- Purge the furnace and gas passes before light-off, typically five volume changes or as the manufacturer requires.
Startup sequence
- Warm up gradually to avoid thermal shock.
- Light off at low fire; prove the pilot and main flame; then increase firing.
- Close the drum vent when pressure begins to rise.
- Blow down the gauge glass and water column; test the low-water fuel cutoff.
- Perform bottom blowdown when pressure is low and stable, following the boiler’s written procedure.
Shutdown
- Reduce firing, purge, secure fuel, and stop the burner.
- Maintain water level; keep the vent open if the boiler is cooling.
- Do not dump hot water or cool rapidly; cool slowly to avoid thermal stress.
- In an emergency, cut fuel first, then air.
Worked example
A cold boiler sits at 0 psig with normal water level. You open the drum vent, start the fan, purge for five minutes, prove the pilot, and light the main flame at low fire. At 5 psig you close the vent. At 15 psig you blow down the low-water cutoff and confirm it cuts fuel. At 50 psig you begin bottom blowdown. Reasoning: the vent prevents pressure while air is expelled; low-fire light-off limits thermal stress; the cutoff is tested after pressure is established but before full load.
Traps
- Lighting off without a proper purge, which risks a furnace explosion.
- Closing the vent too early or leaving it open under pressure.
- Rapid cool-down causing thermal shock or rolling.
- Skipping the low-water cutoff test during startup.