NIULPE Class 1 flashcards
NIULPE Class 1 · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Maximum allowable working pressure
- The highest pressure at which a boiler component may legally operate, computed from shell thickness, allowable stress, joint efficiency, and corrosion allowance under ASME Section I rules.
- Joint efficiency
- A factor between 0.70 and 1.0 applied to allowable stress in shell calculations; it reflects the strength of a welded seam and whether full radiography was performed.
- Postweld heat treatment
- Controlled heating and cooling of a welded component to relieve residual stresses and reduce hardness, required for thick carbon steel and many alloy steel joints.
- Safety valve accumulation
- The pressure rise above set pressure allowed while the safety valve relieves full capacity; ASME limits accumulation to 10 percent above maximum allowable working pressure.
- Stoichiometric air
- The exact quantity of air needed to burn a fuel completely with no oxygen left over; excess air is supplied above this value to ensure complete combustion.
- Flame failure response time
- The maximum interval, typically 4 seconds, within which the burner management system must shut off fuel after loss of proven flame is detected.
- Pre-purge
- A forced-air purge of the furnace and passes, at least four volume changes, performed before light-off to remove combustible gases and prevent furnace explosion.
- Low-water fuel cutoff
- A safety device that stops burner firing when boiler water level falls below a safe limit; it is proven by a slow-drain evaporation test.
- Three-element feedwater control
- A drum level control strategy using steam flow, feedwater flow, and drum level signals together to anticipate load changes and hold level stable.
- Deaerator
- A feedwater heater that removes dissolved oxygen and other gases by heating water to saturation and venting; it limits oxygen pitting in the boiler.
- Economizer
- A heat exchanger that recovers heat from flue gas to preheat boiler feedwater, lowering stack temperature and improving overall boiler efficiency.
- Induced-draft fan
- A fan located after the boiler that pulls flue gas through the unit and maintains slightly negative furnace pressure; it starts before and stops after the forced-draft fan.
- Turbine heat rate
- The thermal energy input in Btu required to produce one kilowatt-hour of output; it equals 3,413 divided by cycle thermal efficiency and measures plant performance.
- Overspeed trip
- A protective device that stops steam admission when turbine speed reaches about 110 percent of rated speed, preventing catastrophic rotor and blade failure.
- Reaction turbine stage
- A stage in which steam expands and drops pressure across both stationary and moving blades, producing reaction force on the rotor in addition to impulse force.
- Synchronous speed
- The rotational speed of an AC generator set by frequency and pole count, calculated as 120 times frequency divided by the number of poles.
- Latent heat of vaporization
- The heat absorbed when water changes to steam at constant temperature and pressure; at atmospheric pressure it is about 970 Btu per pound.
- Overall heat transfer coefficient
- A combined value U that accounts for convection on both sides, conduction through the wall, and fouling resistance, used in Q equals U times area times temperature difference.
- Thermal expansion
- The change in length of a material caused by temperature change, calculated as the expansion coefficient times original length times temperature difference.
- Boiler thermal efficiency
- The ratio of heat absorbed by steam to heat released by fuel, usually based on higher heating value, expressed as a percentage.
- Live zero
- A 4–20 mA instrument signal in which 4 mA represents the zero measurement, allowing an open circuit or failed transmitter to be detected below 3.6 mA.
- Programmable logic controller scan
- The repeating cycle in which a controller reads inputs, executes its program, and updates outputs; scan time determines control response speed.
- Power factor
- The ratio of real power in kilowatts to apparent power in kilovolt-amperes; a low value means more current is needed for the same useful work.
- Flame scanner
- A sensor that verifies the presence of a stable flame by detecting ultraviolet or infrared radiation and signals the burner management system to permit or stop fuel.
- Caustic embrittlement
- Stress corrosion cracking of stressed steel caused by concentrated caustic in crevices; prevented by controlling boiler water pH and limiting caustic concentration.
- Oxygen scavenger
- A chemical such as sodium sulfite or hydrazine added to feedwater to remove residual dissolved oxygen and prevent pitting corrosion in the boiler.
- Blowdown
- The controlled removal of boiler water to limit dissolved solids and sludge; the rate is set by conductivity or chemical analysis to prevent carryover and foaming.
- National Board Inspection Code
- The standard governing inspection, repair, and alteration of in-service boilers; repairs require approval by an authorized inspector and documented records.
- Lockout/tagout
- A procedure under OSHA 1910.147 that isolates and de-energizes equipment, applies locks and tags, and verifies zero energy before maintenance begins.
- Confined-space entry permit
- A written authorization for entering a boiler drum or furnace that documents atmospheric testing, ventilation, attendant presence, and rescue provisions.
- Selective catalytic reduction
- A NOx control method that injects ammonia or urea into flue gas over a catalyst at about 600–750 degrees Fahrenheit, converting NOx to nitrogen and water.
- Continuous emission monitoring
- An instrument system that measures pollutants such as NOx, sulfur dioxide, carbon monoxide, and opacity in stack gas and records data for regulatory compliance.