Advanced Boiler (BA) flashcards
Advanced Boiler (BA) · 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.
- Boiler horsepower
- A unit of boiler capacity equal to 33,475 Btu/h (9.81 kW), approximately the evaporation of 34.5 lb of water per hour at 212°F into dry saturated steam at atmospheric pressure.
- ASME Section I
- The section of the ASME Boiler and Pressure Vessel Code that provides rules for construction of power boilers, defined as boilers operating above 15 psig steam or 160 psig water.
- Thermal efficiency
- The ratio of heat absorbed by the working fluid (steam or water) to the heat input from fuel, expressed as a percentage; calculated using fuel flow and heating value.
- Circulation ratio
- The mass flow rate of steam-water mixture circulating through the boiler divided by the steam mass flow rate leaving the drum; indicates the number of times water circulates before evaporating.
- Stoichiometric air
- The minimum amount of air required to completely burn a given quantity of fuel, providing exactly enough oxygen for all combustible elements without excess or deficiency.
- Excess air
- The amount of air supplied beyond stoichiometric requirements, expressed as a percentage of theoretical air; ensures complete combustion but reduces efficiency if excessive.
- Flame scanner
- A device (ultraviolet or infrared) that detects the presence of a flame and sends a signal to the burner management system; loss of flame signal initiates fuel trip.
- Furnace purge
- A mandatory procedure before ignition that forces air through the furnace for a specified number of volume changes (typically 5) to remove combustible gases and prevent explosion.
- Three-element drum level control
- A feedwater control strategy using steam flow, feedwater flow, and drum level signals to maintain drum level; compensates for shrink and swell during load changes.
- Low-water trip
- A safety interlock that shuts off fuel to the boiler when drum water level falls below a safe limit (typically −6 inches from normal), preventing overheating and explosion.
- Safety valve accumulation test
- A test verifying that the safety valve relieves capacity without allowing boiler pressure to exceed 10% above the set pressure; required by ASME Code.
- Controlled shutdown
- A systematic procedure to reduce boiler load gradually, trip fuel, purge the furnace, and allow controlled cooldown to prevent thermal stress and equipment damage.
- Deaerator
- A feedwater heater that removes dissolved oxygen and other non-condensable gases by heating water to saturation temperature and venting the gases, typically operating at 5–15 psig.
- Continuous blowdown
- A controlled water discharge from the steam drum to maintain boiler water total dissolved solids (TDS) within limits, preventing scale and carryover.
- Carryover
- The contamination of steam by boiler water droplets containing dissolved solids, caused by high water level, foaming, or high TDS; can foul superheaters and turbines.
- Oxygen scavenger
- A chemical (e.g., sodium sulfite, hydrazine, DEHA) added to feedwater to remove residual dissolved oxygen and prevent corrosion in the boiler and condensate system.
- NPSH
- Net Positive Suction Head: the absolute pressure at a pump suction above the vapor pressure of the liquid, expressed in feet; must exceed the pump's required NPSH to prevent cavitation.
- Affinity laws
- For centrifugal pumps and fans, flow varies directly with speed, head/pressure with the square of speed, and power with the cube of speed, assuming constant impeller diameter.
- Air preheater
- A heat exchanger that recovers waste heat from flue gas to preheat combustion air, improving boiler efficiency by reducing flue gas heat loss.
- Balanced draft
- A furnace operating condition where forced draft and induced draft fans maintain a slight negative pressure (e.g., −0.1 to −0.5 in. w.c.) to prevent hot gas leakage.
- Burner management system
- A control system that supervises safe startup, operation, and shutdown of burners, including purge, ignition, flame monitoring, and fuel trip functions per NFPA 85.
- Safety integrity level (SIL)
- A relative level of risk reduction provided by a safety instrumented function, ranging from SIL 1 to SIL 4, with higher levels indicating greater reliability and lower probability of failure.
- Double block and bleed
- A fuel gas piping arrangement with two safety shutoff valves in series and a vent valve between them, used to ensure positive isolation and leak testing before ignition.
- PID control
- A control algorithm using proportional, integral, and derivative actions to minimize error between a process variable and setpoint; widely used for boiler pressure, level, and temperature control.
- Hydrostatic test
- A pressure test in which the boiler is filled with water and pressurized to 1.5 times the maximum allowable working pressure to verify structural integrity and detect leaks.
- Non-destructive examination (NDE)
- Inspection methods such as visual, liquid penetrant, magnetic particle, ultrasonic, and radiographic testing used to detect surface or internal defects without damaging the component.
- ASME PTC 4
- The ASME Performance Test Code for steam generators, providing procedures for conducting efficiency and capacity tests, including measurement methods and uncertainty analysis.
- Safety valve set pressure
- The pressure at which a safety valve begins to open, typically set at or below the boiler maximum allowable working pressure (MAWP) and verified by testing.
- NFPA 85
- The Boiler and Combustion Systems Hazards Code, which establishes requirements for fuel systems, burner management, purging, ignition, flame monitoring, and interlocks to prevent explosions.
- OSHA 29 CFR 1910.261
- The OSHA regulation covering safety requirements for boiler operation, including training, personal protective equipment, lockout/tagout, and confined space entry procedures.
- NSPS
- New Source Performance Standards under the Clean Air Act (40 CFR Part 60), which set emission limits for new, modified, or reconstructed boilers for pollutants such as NOx, SO₂, and particulate matter.
- Low-water condition emergency
- A critical situation where drum water level is not visible in the gauge glass; immediate fuel trip is required, and water must not be added until the boiler has cooled to prevent a violent steam explosion.