MN Boiler Operator flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

ASME Section I

Code covering power boilers over 15 psi steam, including design, materials, fabrication, and required fittings such as safety valves and gauge glasses.

MAWP

Maximum allowable working pressure stamped on the boiler nameplate; safety valve settings and operating limits must not exceed this value.

Water column height rule

Lowest visible water level in the gauge glass must be at least 2 inches above the highest fire line or heating surface, confirmed by try cocks.

Hydrostatic test pressure

For new construction, test at 1.5 times MAWP; for existing boilers under repair, ASME permits testing at the stamped MAWP with jurisdiction approval.

Pre-start purge

Before any ignition attempt, run forced and induced draft fans to move at least four air changes through the furnace and gas passages.

Light-off sequence

Purge, prove igniter flame, open fuel valve, prove main flame within trial-for-ignition time; failure closes fuel and locks out the burner.

Cold boiler warm-up

Raise pressure over 1 to 4 hours, keep drum metal temperature rise near 100 °F per hour, and keep superheater drains open until steam flows.

Bottom blowdown rule

Blow down at low to moderate firing with the boiler under load, one valve at a time, short duration; never blow down during low water.

Stoichiometric methane

CH4 + 2O2 yields CO2 + 2H2O; theoretical air is about 10 cubic feet per cubic foot of natural gas.

Excess air targets

Typically 15 to 25 percent for natural gas and 20 to 30 percent for fuel oil; tune to the lowest excess air with no CO rise or smoke.

Stack loss rule

Each 40 °F rise in flue gas temperature above boiler water or steam temperature costs roughly 1 percent boiler efficiency.

Furnace draft

Normally held slightly negative, about 0.05 to 0.10 inches water column, to keep hot gas in the furnace and prevent leakage.

Safety valve testing

Pop the valve at operating pressure; a valve that leaks or fails to reseat must be repaired or replaced by a qualified valve shop.

Low-water cutoff test

Lower water level with the burner firing; confirm fuel stops and manual reset prevents restart until water is restored to a safe level.

Minnesota inspection rule

Boilers and pressure vessels must be inspected by a state or commissioned inspector at rule-set intervals, and the certificate must be posted.

Boiler horsepower

One boiler horsepower equals 33,475 Btu per hour, about 34.5 pounds of steam per hour from and at 212 °F.

Firetube vs watertube

Firetube boilers pass hot gas through tubes surrounded by water; watertube boilers pass water through tubes surrounded by hot gas.

Superheater protection

Superheater tubes need steam flow for cooling; open drains during warm-up and protect the superheater during light-off and low load.

Main steam stop valve

A stop or stop-check valve on the boiler outlet that isolates the boiler from the header and prevents backflow on a multi-boiler plant.

Paralleling a boiler

Warm and drain the steam header, match boiler pressure to header pressure, then open the main steam stop slowly to bring the boiler on line.

Foaming and carryover

Caused by high dissolved solids, high alkalinity, or oil contamination; blow down, test boiler water, and treat to correct.

Wet vs dry layup

Wet layup uses treated water with an oxygen scavenger and nitrogen blanket; dry layup uses desiccant and sealed openings.

Combustion air-fuel ratio

Burner linkage positions fuel valve and air damper together; mismatch causes smoke or high CO, corrected with a flue gas analyzer.

Burner turndown

Ratio of maximum to minimum stable firing rate; a 10:1 turndown allows low fire operation without cycling the burner on and off.

Flame safeguard lockout

On flame failure the programmer closes the fuel valve and locks out; a manual reset and full purge are required before the next light-off.

Safety valve discharge piping

Must be piped to a safe discharge point with no valve or restriction between the boiler and the valve; piping must be independently supported.

Flame scanner sighting

Adjust sighting so the scanner sees only its own flame, not the igniter, refractory glow, or the opposite burner's flame.

Minnesota operator licensing

License is by class and boiler horsepower; a licensed operator must be on duty or available as required by the boiler size and type.

Economizer protection

Economizer must have water flow before firing and a bypass for startup to prevent steaming; keep feedwater above the acid dew point.

Pressure gauge siphon

A siphon coil protects the pressure gauge from steam temperature; the gauge connects to the highest part of the steam space.

Low water emergency

If water disappears from the gauge glass, secure the burner immediately and do not add water until the boiler has cooled.

Boiler room ventilation

Combustion air and ventilation openings must be kept clear; blocked openings cause incomplete combustion and unsafe conditions.