Boiler Startup Procedure

Pre-Startup Checks

• Verify water level: Ensure the boiler water level is at the normal operating level. Check both the gauge glass and remote level indicator.
• Check fuel supply: Verify fuel valves are open, fuel pressure is correct, and fuel is at the right temperature (for oil).
• Check ventilation: Ensure the boiler room is well-ventilated. Confirm the stack damper is open.
• Inspect burner: Visually inspect the burner, flame scanner, and ignition electrode. Clean if necessary.
• Verify safety systems: Test low-water cutout, safety relief valves, and flame scanner. Ensure all interlocks are functional.
• Open steam header vents: Open vents on the steam header to release air during warm-up.
• Open non-return valve bypass: Open the bypass around the main steam stop valve to allow slow warm-up of the steam header.

Startup Sequence

1. Start the burner on low fire. Most boilers use a programmed startup sequence that purges the furnace, ignites the pilot, then establishes main flame.
2. Allow the boiler to warm up slowly on low fire for 15 to 30 minutes (longer for large boilers). The goal is to gradually heat the refractory, tubes, and water to minimise thermal stress.
3. When pressure reaches 1 to 2 bar, close the steam header vent. Air should be fully discharged by now.
4. Gradually increase firing rate. The pressure ramp rate should not exceed 1 to 2 bar per minute for small boilers, or as specified by the manufacturer for large boilers.
5. When boiler pressure approaches header pressure, open the main steam stop valve slowly. The non-return valve will open automatically when boiler pressure exceeds header pressure.
6. Increase firing rate to match steam demand. Monitor water level closely as load increases.
7. Switch combustion controls from startup mode to modulating mode once stable load is established.

Critical Warnings

Common Startup Problems

• Water level rises on startup: As water heats, it expands. The level may rise above the normal line. Do not blow down immediately. Once steam production begins, the level will stabilise.
• Steam line water hammer: If the steam header is cold, steam will condense rapidly and cause water hammer. Warm the header slowly using the bypass valve. Ensure drip leg traps are functioning.
• Burner won't light: Check flame scanner alignment, ignition transformer, gas pressure, and combustion air supply. The purge cycle must complete before ignition.
• Safety valve lifting during startup: If the safety valve lifts before reaching operating pressure, it may be set incorrectly, weakened, or there may be a blockage in the steam path.