Boiler Operation, Starting-up and Shutting-down
Before light-up
Check water level in the gauge glass, test gauge cocks, confirm all mountings are open or closed correctly, ensure the safety valve is free, check the feed supply and the blowdown valve is shut. Purge the furnace and flue passages before introducing fuel. On a cold boiler, warm through slowly to avoid thermal stress.
Raising steam
Light up on a low fire, allow uniform heating, and keep the boiler vented until steam issues from the vent - this expels air. Watch the water level as steam forms, since expansion raises the indicated level. When working pressure is reached, test the safety valves, blow down the gauge glass and test the low-water cut-out. Put the boiler on line by opening the stop valve slowly, draining warming-through condensate first.
Normal running
Maintain level and pressure, keep the correct excess air, blow down as scheduled, log readings, and never leave the boiler unattended while firing. Watch for carry-over, priming and foaming.
Shutting down
Reduce firing gradually, allow the boiler to cool, blow down when pressure has fallen, close the stop valve, and isolate. Do not dump a hot boiler or force-cool it.
Traps
Questions test the order of operations: purge before light-up; vent air before raising pressure; blow down the glass after pressure is established. A common trap is confusing the sequence of testing safety valves and putting the boiler on line.
Worked rule of thumb
Memory aid for light-up: P-W-F-P - Purge, Water level checked, Fire low, Pressure raised and vented. If any step is skipped, the answer is unsafe.