NJ Boiler Operator key terms

A boiler in which hot combustion gases pass through tubes surrounded by water. Fire-tube units hold a large volume of water, respond slowly to load changes, and are common in low-pressure heating service.

A boiler in which water flows inside tubes that are heated on the outside by combustion gases. The small water content heats quickly and the design suits high pressure and large steam capacity.

A sectional boiler built of cast iron sections joined by push nipples or gaskets, used mainly for low-pressure steam and hot-water heating. It is limited to low pressure and must never be fired dry.

The upper cylindrical vessel of a water-tube boiler where steam separates from water before leaving the unit. It carries the water column, gauge glass connections, and internal separating equipment.

Tubes that add heat to steam after it leaves the boiler drum, raising its temperature above the saturation point. Superheated steam carries more energy and reduces condensation losses in piping and turbines.

A heat exchanger that uses hot boiler exhaust gas to preheat incoming feedwater. It recovers heat that would otherwise go up the stack, improving overall boiler efficiency and lowering fuel use.

A measure of boiler capacity equal to evaporating 34.5 pounds of water per hour from and at 212 degrees Fahrenheit, roughly 33,475 Btu per hour of heat output.

The air supplied to a burner so fuel burns completely. Its quantity, temperature, and distribution affect flame stability, efficiency, and the amount of unburned fuel left in the flue gas.

Air supplied beyond the theoretical amount needed for complete combustion, usually stated as a percentage. A small amount is needed for safety and complete burning, but too much carries heat up the stack.

The proportion of combustion air to fuel delivered to the burner. The correct ratio gives a stable flame and low emissions; too little air produces carbon monoxide and smoke, while too much wastes fuel.

The small pressure difference that moves air into the furnace and combustion gases through the boiler passages. It may be produced by a chimney, a forced-draft fan, an induced-draft fan, or a combination.

A period of forced airflow through the furnace and gas passages before ignition that clears out any combustible gases. A full purge of several air changes must be proven before the burner may light.

A sensor, such as an ultraviolet or infrared detector, that proves a flame is present at the burner. If the flame signal is lost, the flame safeguard control shuts off fuel within seconds.

A spring-loaded valve that opens automatically at a set pressure and releases steam to keep the boiler from exceeding its maximum allowable working pressure. It is the final overpressure protection and must be tested and sealed.

An automatic pressure-relief device designed to handle steam, air, or liquid, used on hot-water boilers and some tanks. It opens at a preset pressure and reseats after the pressure drops.

A vertical fitting piped to the boiler shell that carries the gauge glass and low-water cutoff connections. It dampens water-level surges so the glass shows a steadier and more accurate level.

A transparent sight tube mounted on the water column that shows the water level inside the boiler. Operators blow it down regularly to confirm the passages are clear and the reading is true.

Small manually operated valves mounted at fixed heights on the boiler, usually at the lowest and highest visible water levels. They verify the gauge glass reading when the glass is broken or suspect.

The valve, or pair of valves, used to discharge water and sludge from the lowest point of the boiler. It is opened slowly and briefly, normally with the burner at low fire or shut off.

A device that automatically discharges condensate and noncondensable gases from steam lines while holding back live steam. It keeps the system efficient and helps prevent water hammer.

A plug with a low-melting alloy core installed in the crown sheet or tube sheet of certain boilers. If the metal becomes uncovered and overheats, the alloy melts and releases steam as a low-water warning.

A safety control that senses boiler water level and stops the burner when the water drops below a safe point. Float and probe types are common and must be tested regularly, usually by evaporation or slow drain.

A control that adjusts feedwater flow or pump operation to hold boiler water level at the set point as steam demand changes. It works with level sensors, a control valve, and the feed pump.

A vessel that heats feedwater with steam to drive off dissolved oxygen and other gases, reducing corrosion in the boiler and feed system. It usually includes a storage tank and vents the released gases.

A hard deposit of calcium and magnesium salts baked onto boiler heating surfaces. Scale insulates the metal, wastes fuel, and can overheat tubes until they bulge or fail.

Chemical and mechanical treatment that limits metal attack by oxygen, carbon dioxide, and low pH in the boiler and feed system. It includes deaeration, oxygen scavengers, and pH adjustment with regular testing.

Water added to the system to replace steam and condensate losses. Its quality must be controlled by treatment, because untreated makeup carries hardness and oxygen that cause scale and corrosion.

A condition in which high concentrations of dissolved solids and organic matter form a froth of bubbles on the boiler water surface. It causes erratic level readings and carryover of water into steam lines.

Carryover of boiler water with steam caused by high water level, sudden steam demand, or foaming. It can contaminate steam, promote water hammer, and produce false high-level readings.

The deliberate removal of water from the boiler to control dissolved solids and clear out sludge. Bottom blowdown removes sediment; surface blowdown skims the top of the water to reduce conductivity.

A pressure test in which the boiler is filled with water and pressurized, commonly to 1.5 times the maximum allowable working pressure, to check for leaks and structural strength before being returned to service.

A test confirming that the safety valves can release all the steam the boiler can generate at maximum firing without pressure rising above the permitted limit. The boiler is isolated and fired for the test.

A sharp banging or knocking caused by condensate slugs or sudden valve closure in steam or water piping. It can crack pipe and fittings, so traps, drip legs, and slow valve operation are used to prevent it.

A rapid ignition of accumulated fuel in the furnace or gas passages that produces a sudden pressure wave, often blowing fire out of the firing door. Proper purge and burner maintenance prevent it.

A state in which boiler water falls below the safe operating level, risking overheated metal and tube failure. The operator must stop firing, never add water to a badly overheated boiler, and follow shutdown procedures.

The highest pressure at which a boiler or pressure vessel may legally operate, based on its design, materials, and thickness. Safety valves are set at or below this value and the pressure gauge is marked accordingly.

Under N.J.A.C. 12:90, a boiler operating above the low-pressure limits, generally more than 15 psig steam or more than 160 psig water at 250 degrees Fahrenheit. It requires more frequent inspection and licensed operators.

A boiler limited to 15 psig or less steam pressure, or to water pressure of 160 psig or less at a temperature not above 250 degrees Fahrenheit, as defined in N.J.A.C. 12:90.

A document issued after the required boiler inspection, authorizing operation for a stated period. Operating a boiler without a currently valid certificate is prohibited by state regulation.

A credential issued by the State under N.J.A.C. 12:90 that authorizes a person to operate a specific class of boiler. The class and qualification requirements depend on boiler type, pressure, and size.