Cram Sheet

A high-pressure boiler operates above 15 psi steam pressure.

1 Boiler Horsepower ≈ 10 sq ft of heating surface (Minnesota).

MAWP = Maximum Allowable Working Pressure — stamped on the boiler nameplate.

Firetube boiler: hot gases inside tubes, water outside. Watertube boiler: water inside tubes, hot gases outside.

Latent heat = energy to change water to steam WITHOUT temperature increase (phase change).

Sodium sulfite is an oxygen scavenger — removes dissolved O₂ to prevent pitting corrosion.

Scale acts as insulation — causes tube overheating and potential failure.

Bottom blowdown removes sludge/sediment. Surface blowdown removes floating solids and controls TDS.

Foaming causes: high TDS, oil contamination, high alkalinity. Treatment: surface blowdown + chemistry correction.

LWCO is tested by blowdown test (drain water) or evaporation test (let water drop naturally).

Safety valves may ONLY be adjusted by qualified/authorized personnel.

Lockout/tagout (LOTO) is ALWAYS required before boiler maintenance.

Passing score on the MN boiler exam is 70%.

1 psi = 2.31 feet of water.

°F = (°C × 1.8) + 32. Water boils at 212°F / 100°C at atmospheric pressure.

Perfect combustion requires: fuel + oxygen + heat + proper mixing.

Pre-purge removes combustible gases from the furnace BEFORE ignition. Required before every start.

Excess air = lower efficiency (heat goes up the stack). Insufficient air = CO production (dangerous).

Flue gas analysis is the best indicator of combustion efficiency.

Rising stack temperature over time usually means soot or scale buildup — reduced heat transfer.

Water hammer is caused by condensate slugs — always open steam valves SLOWLY.

Startup sequence: verify water level → open vents → check fuel → low fire → warm slowly → monitor pressure.

Burner lockout = manual reset required. Investigate the cause before resetting.