Boiler Operator flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Boiler horsepower definition
- One boiler horsepower equals 33,475 Btu per hour, the heat needed to evaporate 34.5 pounds of water per hour from and at 212 F.
- Fire-tube vs water-tube
- In a fire-tube boiler hot gases flow inside tubes surrounded by water; in a water-tube boiler water flows inside tubes surrounded by hot combustion gases.
- ASME Section I scope
- ASME Boiler and Pressure Vessel Code Section I covers power boilers and their appurtenances, setting requirements for materials, design, fabrication, inspection, and safety valve capacity.
- Staybolt function
- Staybolts tie together the flat plates of firebox and locomotive-type boilers, preventing the sheets from bulging or deforming under internal steam pressure.
- Three T's of combustion
- Complete combustion requires adequate Temperature, Turbulence for mixing fuel with air, and Time in the furnace for the combustion reaction to finish.
- Excess air purpose
- Air supplied beyond the theoretical amount ensures complete combustion; typical excess air is 10-20 percent for gas and oil and 20-40 percent for coal.
- Balanced draft
- Balanced draft uses a forced draft fan to supply combustion air and an induced draft fan to remove flue gas, holding furnace pressure slightly below atmospheric.
- Inches of water column
- Draft is measured in inches of water column; one psi equals about 27.7 inches of water column, and furnace draft normally reads about -0.05 to -0.10.
- Safety valve requirement
- Every boiler must have a safety valve set at or below its maximum allowable working pressure, with no shutoff valve between the boiler and that valve.
- Water column blowdown
- Blowing down the water column and gauge glass clears sludge and sediment from the connections so the indicated water level remains accurate.
- Economizer function
- An economizer transfers heat from leaving flue gas to incoming feedwater, lowering stack temperature and improving overall boiler thermal efficiency.
- Steam drum dry pipe
- A dry pipe or mechanical separator inside the steam drum removes entrained moisture from steam before it leaves the boiler, improving steam quality.
- Zeolite softening
- Sodium zeolite softening exchanges calcium and magnesium ions in the water for sodium ions, removing the hardness that would otherwise form boiler scale.
- Deaerator purpose
- A deaerator heats feedwater to saturation and strips out dissolved oxygen and carbon dioxide, which would otherwise cause pitting corrosion in the boiler.
- Scale effect on tubes
- Scale is a poor heat conductor; it insulates tube metal, raising metal temperature and causing overheating, bulging, and eventual tube failure.
- Continuous blowdown
- Continuous surface blowdown removes dissolved solids from the steam drum, controlling conductivity and total dissolved solids so carryover does not occur.
- Pneumatic control signal
- The standard pneumatic transmission signal in boiler controls is 3 to 15 psi, with 3 psi representing zero percent and 15 psi representing 100 percent.
- Flame scanner function
- A flame scanner uses ultraviolet, infrared, or flame-rectification sensing to prove the burner flame; loss of the flame signal trips the fuel valves.
- Pre-purge requirement
- Before each lightoff the burner management system must complete a pre-purge, typically five minutes or a specified number of furnace air changes, to clear unburned fuel.
- PID control terms
- Proportional action responds to the size of the deviation, integral action eliminates offset over time, and derivative action responds to the rate of change.
- Normal drum level
- Normal operating water level is at the center of the gauge glass; the level must stay visible at all times because low water requires an immediate fuel trip.
- Warm-up rate limit
- Boilers are heated slowly, commonly at about 100 F per hour, with drum top-to-bottom temperature difference limited to roughly 50-100 F to avoid thermal stress.
- Wet lay-up method
- Wet lay-up stores an idle boiler full of treated water, often with a nitrogen blanket or oxygen scavenger, to exclude oxygen and prevent corrosion.
- Bottom blowdown purpose
- Bottom blowdown removes sludge and sediment settling in the mud drum or lower shell; blows are short and frequent with the boiler under load.
- Hydrostatic test pressure
- A hydrostatic test is performed at 1.5 times the maximum allowable working pressure for new construction, with the boiler filled and all air vented.
- Ultrasonic thickness testing
- Ultrasonic thickness testing measures remaining wall thickness of tubes, shell, and headers, detecting metal loss from corrosion and erosion without cutting.
- Safety valve pop test
- A pop test verifies that the safety valve opens at its set pressure, reseats properly, and does not leak; results are recorded in the boiler log.
- Dry lay-up method
- Dry lay-up removes all water, dries the interior, and places desiccant inside sealed drums and headers to keep the metal free of moisture.
- Low-water emergency action
- If water is not visible in the gauge glass, shut off the fuel at once; do not add feedwater until the boiler has cooled enough to rule out overheated metal.
- Never gag safety valve
- A safety valve must never be gagged, plugged, or have its discharge blocked, because it is the final protection against overpressure of the boiler.
- NFPA 85 purpose
- NFPA 85 is the standard for boiler and burner management systems, covering pre-purge, ignition sequencing, flame proving, and safety interlocks.
- Confined space entry
- Entering a boiler drum or furnace requires a confined space permit, atmospheric testing, ventilation, an attendant outside, and lockout of all energy sources.