IA 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
- A unit of boiler capacity equal to 33,475 Btu/h, roughly the heat needed to evaporate 15.65 kg of water per hour at atmospheric pressure.
- MAWP
- Maximum allowable working pressure, the highest gauge pressure at which a boiler may be operated, stamped on the nameplate and set as the safety valve limit.
- Latent heat of vaporization
- The heat absorbed when a unit mass changes from saturated liquid to saturated vapor at constant temperature and pressure; about 2,257 kJ/kg at 100 °C.
- Superheated steam
- Steam heated above its saturation temperature at a given pressure; it carries no moisture and gives up sensible heat as it cools.
- LMTD
- Logarithmic mean temperature difference, the effective driving temperature difference for heat transfer in a boiler or heat exchanger, used in Q = U·A·LMTD.
- Fire-tube boiler
- A boiler in which hot combustion gases pass through tubes surrounded by water; limited to moderate pressure and capacity, common in packaged heating plants.
- Water-tube boiler
- A boiler in which water circulates inside tubes surrounded by hot gas; used for high pressure and large capacity in utility and industrial service.
- Economizer
- A heat exchanger that preheats boiler feedwater using heat from the flue gas before the gas leaves the stack, raising overall thermal efficiency.
- Steam drum
- The upper pressure vessel that separates steam from water, holds the water level, and provides space for steam release and chemical addition.
- Safety valve capacity
- The maximum mass flow a safety valve can discharge at its set pressure; it must equal or exceed the boiler's maximum steam-generating capacity.
- Excess air
- The percentage of combustion air supplied above the theoretical stoichiometric amount; typically 10–20% for gas firing to ensure complete combustion.
- Turndown ratio
- The ratio of a burner's maximum firing rate to its minimum stable firing rate; a 10:1 burner can fire from full rate down to one-tenth.
- Pre-purge
- A timed period of air flow through the furnace before ignition that removes any accumulated combustible gas, typically 15–60 seconds.
- Flame scanner
- A sensor, usually ultraviolet or a flame rod, that proves the presence of flame; loss of signal trips the fuel valve within the flame-failure response time.
- Makeup water
- Treated water added to the boiler to replace steam and condensate losses; it is softened and demineralized to prevent scale and corrosion.
- Deaerator
- A vessel that heats feedwater and strips dissolved oxygen and carbon dioxide, reducing corrosion in the boiler and condensate system.
- Scale
- A hard deposit of calcium and magnesium salts on boiler surfaces that insulates tubes, reduces heat transfer, and can cause overheating and tube failure.
- Carryover
- The entrainment of boiler water droplets and dissolved solids into the steam, detected by high conductivity in condensed steam and controlled by blowdown.
- Low-water fuel cutoff
- A safety device that shuts off fuel to the burner when the water level falls below the safe limit, preventing overheating and tube damage.
- Burner management system
- The control system that sequences pre-purge, ignition, main flame, and shutdown, and interlocks all safety devices to prevent unsafe firing.
- High gas pressure switch
- A safety switch that trips the burner when fuel gas pressure rises above its set point, protecting the burner and fuel train from overpressure.
- Gauge glass
- A transparent tube connected to the boiler at the steam and water space that shows the water level; its normal level mark is the operating datum.
- Bottom blowdown
- Opening the mud drum valve to discharge sludge and sediment; done at low fire with the boiler under steady load and the valve fully opened and closed.
- Priming
- A condition in which boiler water is carried over into the steam line, often caused by high water level, foaming, or rapid load changes.
- Hydrostatic test
- A pressure test with water at 1.5 times MAWP for new boilers, with safety valves removed or gagged, to verify strength and tightness.
- Ultrasonic thickness test
- A non-destructive method that measures tube and shell wall thickness to detect corrosion or erosion loss and determine whether replacement is required.
- Flue gas analysis
- Measurement of oxygen, carbon monoxide, carbon dioxide, and stack temperature used to set excess air and calculate combustion efficiency.
- ASME Section I
- The section of the ASME Boiler and Pressure Vessel Code that sets rules for construction of power boilers, including materials, design, and stamping.
- ASME Section IV
- The ASME code section covering construction of heating boilers, which operate at lower pressure and temperature than power boilers.
- ASME CSD-1
- The ASME standard for controls and safety devices on automatically fired boilers, covering interlocks, flame safeguards, and limit controls.
- NFPA 85
- The National Fire Protection Association standard for boiler and combustion systems hazards, covering fuel trains, purging, and burner safety.
- Lockout/tagout
- A procedure that isolates and locks energy sources, including fuel, electricity, and steam, before maintenance to prevent unexpected startup or release.