Power Eng 3rd Class flashcards
Power Eng 3rd Class · 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.
- Sensible heat
- Heat that changes a substance's temperature without changing phase; calculated as mass times specific heat times temperature change.
- Latent heat of vaporization
- Heat absorbed or released when a substance changes phase at constant temperature, such as water boiling to steam.
- LMTD
- Log mean temperature difference; the driving temperature difference for heat transfer in a heat exchanger, calculated from the two end temperature differences.
- Excess air
- Air supplied above the theoretical amount needed for complete combustion; expressed as a percentage of theoretical air.
- MAWP
- Maximum allowable working pressure; the highest pressure at which a boiler or pressure vessel may legally operate.
- Bottom blowdown
- Discharge of water from the lowest point of a boiler to remove sludge and sediment and control dissolved solids.
- Air preheater
- Auxiliary that uses hot flue gas to warm combustion air before it enters the furnace, reducing stack heat loss.
- Economizer
- Heat exchanger that heats boiler feedwater using exiting flue gas, lowering stack temperature and improving efficiency.
- Deaerator
- Vessel that heats feedwater to saturation and vents dissolved oxygen and carbon dioxide, also providing feedwater storage.
- Gate valve
- Isolation valve with a sliding gate that gives low pressure drop when fully open; not intended for throttling flow.
- Check valve
- Valve that permits flow in one direction only, preventing backflow; it is not used for throttling.
- Water hammer
- Pressure surge caused by rapid valve closure or trapped condensate; prevented by slow closing and proper drainage.
- NPSH
- Net positive suction head; the margin of pressure above vapor pressure available or required at a pump suction to avoid cavitation.
- Affinity laws
- Relations for a pump or fan: flow varies with speed, head with speed squared, and power with speed cubed.
- Cavitation
- Formation and collapse of vapor bubbles when local pressure drops below vapor pressure, causing noise, vibration, and damage.
- LWCO
- Low-water fuel cutoff; a safety device that shuts off fuel when boiler water level falls below a safe limit.
- PID control
- Control using proportional, integral, and derivative actions; proportional responds to error, integral removes offset, derivative anticipates change.
- Flame scanner
- Safety device that proves the presence of flame and trips fuel if the flame signal is lost during operation.
- Power factor
- Ratio of real power to apparent power in an AC circuit; low power factor increases reactive current and line losses.
- LOTO
- Lockout/tagout; procedure that isolates energy sources and locks them off before maintenance to prevent unexpected energization.
- Oxygen scavenger
- Chemical such as sulfite added to boiler water to remove dissolved oxygen and prevent pitting corrosion.
- Carryover
- Passage of boiler water droplets or dissolved solids into steam, often caused by high TDS or foaming.
- COP
- Coefficient of performance; ratio of refrigeration effect to work input for a refrigeration cycle.
- Superheat
- Temperature of refrigerant vapor above its saturation temperature at the same pressure; protects the compressor from liquid slugging.
- Confined space
- Enclosed area with limited entry and exit that may contain hazardous atmosphere; entry requires permit, testing, and an attendant.
- Hydrostatic test
- Pressure test using water to verify the integrity of a boiler or pressure vessel before service or after repair.
- Preventive maintenance
- Scheduled inspection, lubrication, and servicing performed to prevent failures and reduce unplanned downtime.
- Root-cause analysis
- Method such as 5 Whys or fishbone used to identify the underlying cause of a failure rather than its symptoms.
- Impulse turbine stage
- Turbine stage in which steam expands through stationary nozzles and pressure drops before reaching the moving blades.
- Condenser vacuum
- Low absolute pressure at a turbine exhaust that increases enthalpy drop and improves turbine efficiency.
- Cv
- Valve flow coefficient; a number relating flow rate to pressure drop and fluid specific gravity for valve sizing.
- Dew point
- Temperature at which moist air becomes saturated and condensation begins; a measure of moisture content.