Special Boiler Operator flashcards
Special Boiler Operator · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Boiler horsepower
- A measure of boiler capacity equal to 33,475 Btu per hour, defined as evaporating 34.5 pounds of water per hour from and at 212 degrees Fahrenheit.
- Fire-tube boiler
- A boiler in which hot combustion gases flow through tubes surrounded by water, limiting pressure and capacity but offering large steam storage and simple construction.
- Water-tube boiler
- A boiler in which water circulates through tubes heated externally by combustion gases, permitting higher pressures, larger capacities, and faster response to load changes.
- Equivalent evaporation
- The evaporation rate corrected to a standard of feedwater at 212 degrees Fahrenheit producing dry saturated steam, allowing boilers of different conditions to be compared.
- Safety valve requirement
- Each boiler must have at least one safety valve whose capacity equals or exceeds maximum steam output, with set pressure not above the maximum allowable working pressure.
- Steam drum function
- The upper drum separates steam from water, houses separators and baffles, and provides a point for chemical feed and water level indication.
- Mud drum function
- The lower drum collects sludge and sediment and provides a low point for bottom blowdown, helping keep heating surfaces free of deposits.
- Gauge glass test
- Opening the gauge glass drain and observing water return verifies that the water column connections are clear and the indicated level is reliable.
- Economizer
- A heat recovery device that uses flue gas to preheat feedwater before it enters the boiler, improving efficiency and reducing stack temperature.
- Three T's of combustion
- Temperature, turbulence, and time must all be sufficient for complete combustion; a deficiency in any one produces smoke, carbon monoxide, or unburned fuel.
- Excess air
- The amount of combustion air supplied above theoretical air, expressed as a percentage and adjusted by flue gas oxygen and carbon monoxide readings.
- Flame scanner
- A detector that senses ultraviolet or infrared radiation from the burner flame and signals the flame safeguard to close the fuel valve on flame loss.
- Burner turndown
- The ratio of maximum firing rate to minimum stable firing rate; operating below the turndown limit risks flame instability and unburned fuel.
- Atomization
- Breaking liquid fuel into fine droplets so it vaporizes and mixes with air, improving combustion efficiency and reducing smoke and unburned fuel.
- Scale formation
- Deposits of precipitated calcium and magnesium salts on heating surfaces that reduce heat transfer, raise metal temperatures, and can cause tube failure.
- Deaerator
- Equipment that heats feedwater to near saturation and vents released gases, removing dissolved oxygen and carbon dioxide that cause corrosion.
- Continuous blowdown
- A controlled, continuous removal of boiler water from near the water surface to limit dissolved solids concentration and prevent foaming and carryover.
- Carryover
- Boiler water droplets entrained in steam, caused by high dissolved solids, foaming, or high water level, which can deposit solids on superheaters and turbines.
- Furnace purge
- A required flow of air through the furnace before ignition to remove combustible gases, typically four to five furnace volumes.
- Cold startup sequence
- Verify water level, purge the furnace, establish pilot flame, prove main flame, then raise load gradually while monitoring pressure and level.
- Bottom blowdown
- Short, repeated opening of the bottom blowdown valves with the boiler under load to remove sludge and sediment from the mud drum.
- Normal shutdown
- Reduce load gradually, cut fuel, purge the furnace, close the main steam stop, and maintain water level while the boiler cools.
- Low-water fuel cutoff
- A safety device that stops fuel and air supply when the water level falls below a safe point, preventing overheating and tube failure.
- High-pressure limit switch
- A control that stops the burner at a set pressure above normal operating pressure but below the safety valve setpoint, providing overpressure protection.
- Flame safeguard programmer
- A control that supervises purge, pilot, main flame, and flame failure timing, closing the main fuel valve when the flame signal is lost.
- Manual reset requirement
- A low-water trip must remain latched after a low-water condition so the boiler cannot restart automatically until an operator resets it.
- Hydrostatic test
- A pressure test at 1.5 times maximum allowable working pressure for new boilers, with safety valves removed or gagged and the boiler vented.
- Safety valve pop test
- A test performed with steam pressure to verify that the safety valve opens at its set pressure and reseats properly, never by hand lifting alone.
- Low-water cutoff test
- Lowering the water level or opening the test connection to confirm the burner trips and the alarm sounds, verifying the safety device functions.
- Low-water emergency
- Shut off fuel, do not add water to a hot boiler until the cause is found and the boiler cools, and inspect for overheating damage.
- Dry-fired boiler
- An overheated boiler without water must be cooled slowly; adding cold water to hot dry metal can cause violent steam expansion and a pressure surge.
- ASME Code sections
- ASME Section I covers power boilers, Section IV covers heating boilers, and Section VIII covers pressure vessels, establishing design and construction rules.
- Maximum allowable working pressure
- The highest pressure at which a boiler may be operated, established by code design and protected by the safety valve as the final overpressure device.