AK Boiler Operator key terms

The construction code for power and heating boilers. It sets minimum rules for materials, design, fabrication, welding, inspection and stamping so a boiler can safely hold its rated pressure.

The highest pressure at which a boiler or pressure part may legally and safely operate. It is established by design calculations, marked on the nameplate, and never exceeded in service.

A boiler in which water flows inside tubes that are heated from the outside by combustion gases. This arrangement allows high pressures, large steam output, and quick response to load changes.

A boiler in which hot combustion gases pass through tubes surrounded by water. It holds a large water volume and responds slowly, so it is usually limited to lower pressures and smaller capacities.

The top plate of a firebox that has flame beneath it and water above it. If the water level drops below it, the metal overheats, weakens, and can collapse.

The upper cylindrical vessel of a watertube boiler. Steam separates from water inside it, the operating water level is held and observed there, and saturated steam leaves toward the superheater or plant.

A group of tubes that receives saturated steam from the drum and heats it further. The result is drier, hotter steam that carries more energy and condenses less in piping and turbines.

A vertical fitting attached to the boiler shell that stills the water surface and carries the gauge glass and level controls. Its connections must be kept open by regular blowdown or level readings become false.

A clear tube or flat glass assembly connected to the water column that shows the true water level in the boiler. It is the operator's primary visual check of level.

A device that releases condensate and trapped air from steam lines and equipment while holding back live steam. Without working traps, lines fill with water and lose heat output.

A one-way valve on the feedwater line that permits water to enter the boiler but stops it from flowing back into the feed pump or deaerator when the pump stops.

Burning fuel with exactly the amount of oxygen required to convert all carbon to carbon dioxide and all hydrogen to water, leaving no oxygen or unburned fuel in the products.

Air supplied above the theoretical amount needed for complete burning, usually stated as a percentage. Too little produces smoke and carbon monoxide; too much carries heat up the stack.

Testing of exhaust gas for oxygen, carbon dioxide, carbon monoxide and temperature. Results show whether the burner is running too rich or too lean and guide air-fuel adjustments.

A fan that pushes combustion air into the burner and furnace, overcoming the resistance of ducts, dampers and air heaters. Its output must match fuel flow to keep the mixture correct.

Breaking liquid fuel into a fine mist so it mixes readily with air and burns as a short, bright flame. Poor atomization causes smoking, carbon buildup and wasted fuel.

The amount of dissolved salts and other solids in boiler water, reported in parts per million. High levels cause foaming, priming and carryover, so the concentration is limited by blowdown.

A hard coating of calcium and magnesium salts baked onto heated boiler surfaces. It blocks heat transfer, raises metal temperature, wastes fuel and can lead to tube rupture.

An ion exchange unit that swaps hardness minerals in makeup water for sodium. Softening prevents scale in the boiler but does not remove dissolved solids, so blowdown is still needed.

A vessel that heats feedwater with steam and strips out dissolved oxygen and carbon dioxide. Removing these gases prevents pitting and corrosion in the boiler and condensate system.

Boiler water droplets and the dissolved solids they contain leaving with the steam. It fouls superheaters, contaminates processes and deposits solids in turbines and steam mains.

A timed air sweep through the furnace and gas passages, with all fuel valves closed, before ignition. It clears any combustible gas so light-off cannot cause an explosion.

A timed air sweep after the fuel has been shut off, removing leftover combustible gases from the furnace and passages before the boiler is left idle or re-lighted.

Opening a valve at the lowest point of the boiler to discharge sludge, sediment and concentrated water. It is done in short bursts so the water level stays within safe limits.

Drawing water from near the normal water level, where dissolved solids and floating impurities collect. Continuous or frequent surface blowdown keeps boiler water chemistry within limits.

A test in which the boiler is filled with water and pressurized above its working pressure to prove the strength and tightness of new or repaired pressure parts.

A non-destructive method that uses sound waves to measure how much wall thickness remains in shells, tubes and piping, revealing loss from corrosion or erosion.

Examining the drained boiler's waterside and fireside during a shutdown for scale, corrosion, cracking, bulging, and damage to refractory or burner parts.

A procedure for isolating fuel, steam, water and electrical energy with locks and warning tags so equipment cannot be started while someone is working on it.

A spring-loaded valve that opens automatically at a set pressure and discharges steam or water, protecting the boiler from overpressure. It must be tested and never gagged or blocked.

A plug with a low-melting alloy core installed in a crown sheet or similar plate. If water drops below it, the alloy melts and releases steam into the furnace as a warning.

A control that monitors water level and shuts off the burner when the level falls below a safe point, preventing overheating of heated surfaces and a dangerous restart.

A control system with a flame sensor that proves ignition and main flame are established. If the flame signal is lost, it closes the fuel valves and starts a shutdown sequence.

A sudden ignition of unburned fuel that has collected in the furnace or gas passages. Typical causes are skipped purges, repeated failed light-offs, and leaking fuel valves.

A sharp bang or series of bangs in steam piping caused by condensate slugs driven at high speed or by abrupt valve closure. It can crack fittings, gaskets and pipe supports.

Entering a boiler drum or other enclosed vessel through a small opening. It requires a permit, gas testing, ventilation, a standby attendant and rescue provisions before anyone goes in.

Recording a boiler's design and construction details and stamp with the National Board, creating a permanent traceable record used by inspectors during repairs and jurisdictional reviews.

A license granted by the jurisdiction after written and practical examination, allowing a person to operate boilers of a specified type and size. Operating without one breaks boiler law.

A periodic examination of a boiler by a state, provincial or municipal inspector, or by an authorized insurance inspector, to confirm it is still safe for continued service.

The operator's running record of water level, pressure, blowdowns, tests, repairs and unusual events. Inspectors and regulators use it as evidence that the plant is properly attended.