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NJ Boiler Operator practice questions

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Question 1Boiler Construction, Design, and Types

In a firetube boiler, the hot products of combustion flow:

  1. Through a superheater coil before reaching the furnace
  2. Into the steam drum ahead of the tube bank
  3. Around the tubes, with water inside them
  4. Through the tubes, with water surrounding them Correct answer.

Explanation

In a firetube design the products of combustion pass through tubes that are surrounded by water held in the shell. Heat moves from the hot gas through the tube wall into the water, and the cooled gas then travels on to the stack. The water is on the outside of the tubes, never the inside.

Question 2Boiler Construction, Design, and Types

A watertube boiler is best described as a boiler in which:

  1. Water circulates inside tubes that are surrounded by hot gases Correct answer.
  2. Water surrounds tubes that carry the flue gas
  3. Water is sprayed into the combustion chamber to evaporate
  4. Water is heated only in an external economizer

Explanation

In a watertube boiler the water and steam mixture is contained inside the tubes while the hot combustion gases pass over the outside surfaces. Because the pressure boundary is the relatively small tube diameter, this design is suited to high pressures and large steam capacities.

Question 3Boiler Construction, Design, and Types

The primary function of the steam drum in a watertube boiler is to:

  1. Separate steam from the steam-water mixture and store it Correct answer.
  2. Preheat the combustion air entering the furnace
  3. Support the furnace refractory and casing
  4. Collect ash and sediment from the flue gas

Explanation

The steam drum receives the steam-water mixture from the riser tubes, allows the steam to separate from the water, and stores steam to smooth out load swings. Drum internals such as separators and scrubbers improve steam purity before the steam leaves for the superheater.

Question 4Boiler Construction, Design, and Types

In a two-drum watertube boiler, the lower drum is called the mud drum and its purpose is to:

  1. Hold and support the superheater elements
  2. Reheat steam that has already passed through the turbine
  3. Collect sediment and form a header for the lower tube ends Correct answer.
  4. Provide the space in which fuel is burned

Explanation

The lower or mud drum acts as the lower header for the generating tubes and provides a low point where sludge and sediment settle so they can be removed by bottom blowdown. The upper drum performs the steam separation and storage function.

Question 5Boiler Construction, Design, and Types

A superheater in a boiler raises the:

  1. Temperature of the feedwater before it enters the drum
  2. Temperature of the steam above its saturation point Correct answer.
  3. Pressure of the steam without changing its temperature
  4. Temperature of the combustion air before it enters the furnace

Explanation

A superheater adds heat to saturated steam taken from the drum, raising its temperature above the saturation temperature corresponding to the drum pressure. Dry superheated steam carries more useful energy per pound and reduces condensation losses in the turbine or process lines.

Question 6Boiler Construction, Design, and Types

An economizer is installed in a boiler to:

  1. Remove moisture droplets from the saturated steam
  2. Heat the combustion air with heat taken from the leaving flue gases
  3. Cool the steam leaving the superheater to a set temperature
  4. Heat the feedwater with heat taken from the leaving flue gases Correct answer.

Explanation

The economizer is a heat exchanger in the gas path between the boiler bank and the air preheater that transfers heat from the leaving flue gas to the incoming feedwater. This lowers stack temperature and reduces the fuel needed to bring the water up to saturation.

Question 7Boiler Construction, Design, and Types

The purpose of an air preheater in a boiler unit is to:

  1. Cool the furnace gases before they enter the superheater
  2. Raise the steam temperature above saturation
  3. Heat combustion air using heat from the flue gas Correct answer.
  4. Heat the feedwater before it reaches the economizer

Explanation

An air preheater recovers heat from the flue gas leaving the economizer and uses it to warm the combustion air supplied to the furnace. Warmer air improves combustion stability and lowers the stack loss, raising overall boiler efficiency.

Question 8Boiler Construction, Design, and Types

The furnace or combustion chamber of a boiler is the space where:

  1. Feedwater is preheated before entering the drum
  2. Sediment is settled out of the boiler water
  3. Steam is separated from the water mixture
  4. Fuel is burned and combustion is completed Correct answer.

Explanation

The furnace provides the volume and residence time needed for the fuel to burn out completely before the gases enter the convection passes. It is normally lined with waterwall tubes and refractory so that the heat released can be absorbed while the gas is cooled to a temperature the tube metal can tolerate.

Question 9Boiler Construction, Design, and Types

Which statement best describes a Scotch marine boiler?

  1. A watertube unit with an upper and lower drum joined by a bank of bent tubes
  2. A coil-type once-through unit that operates without a steam drum
  3. A sectional cast iron unit limited to low-pressure heating service
  4. A firetube unit with furnaces inside a water-filled cylindrical shell Correct answer.

Explanation

The Scotch marine boiler is a firetube boiler whose large cylindrical shell contains one or more furnaces and a tube bank, all surrounded by water. Hot gases make several passes through the tubes before leaving the boiler, and the design is widely used in packaged form for packaged steam and hot water plants.

Question 10Boiler Construction, Design, and Types

A horizontal return tubular (HRT) boiler is characterized by:

  1. A bent-tube arrangement with two drums and waterwalls
  2. A shop-assembled package with an integral burner and no brickwork
  3. A vertical assembly of cast iron sections bolted together
  4. A cylindrical shell set over a brick furnace, with gases returning under the shell Correct answer.

Explanation

In an HRT boiler the fire is built in a brick furnace outside and below the cylindrical shell, and the hot gases travel through the shell's tubes and then return along the underside of the shell to the stack. These boilers are field-erected with a substantial masonry setting and are now largely historical.

Question 11Boiler Construction, Design, and Types

Cast iron sectional boilers are typically limited to:

  1. Supercritical steam service in large utility plants
  2. Waste heat recovery from diesel engine exhaust
  3. Low-pressure steam or hot water heating service Correct answer.
  4. High-pressure steam service above 250 psig

Explanation

Cast iron is brittle and the bolted or gasketed section joints cannot be relied on at high pressure or temperature, so these boilers are restricted to low-pressure steam and hot water heating. Their sectional construction allows them to be carried into a basement and assembled in place.

Question 12Boiler Construction, Design, and Types

Waterwall tubes in a boiler furnace serve to:

  1. Absorb radiant heat and shield the furnace refractory from high temperature Correct answer.
  2. Preheat the fuel oil to atomizing temperature
  3. Wash ash out of the flue gas before it leaves the furnace
  4. Carry and support the superheater elements

Explanation

Waterwall tubes line the furnace and absorb radiant heat directly from the flame, which both increases steam generation and keeps the refractory and casing behind them cooler. Cooling the gas in the furnace also helps prevent slagging and reduces the gas temperature entering the convection bank.

Question 13Boiler Construction, Design, and Types

Baffles in a firetube boiler are installed to:

  1. Separate steam from water inside the shell
  2. Meter the feedwater flow into the boiler
  3. Guide the hot gases across the tubes in a series of passes Correct answer.
  4. Brace the tubes against internal pressure

Explanation

Baffles and baffle plates force the combustion gases to travel across the tube bank in a defined number of passes rather than short-circuiting straight to the outlet. This increases gas velocity across the tubes and the effective heat transfer surface, improving efficiency.

Question 14Boiler Construction, Design, and Types

Staybolts in a boiler are used to:

  1. Support the weight of the superheater elements
  2. Anchor the boiler shell to its concrete foundation
  3. Fasten the tubes into the tube sheets
  4. Tie together flat stayed surfaces that pressure would otherwise force apart Correct answer.

Explanation

Flat surfaces such as the crown sheet, firebox sheets and the space between the furnace and shell cannot resist internal pressure by shape alone, so staybolts tie the opposing plates together. The stays carry the pressure load in tension and keep the plates from bulging or failing.

Question 15Boiler Construction, Design, and Types

A handhole in a boiler is provided primarily to:

  1. Relieve excess pressure before it reaches the safety valve
  2. Admit secondary combustion air into the furnace
  3. Permit inspection and cleaning where a manhole is too large Correct answer.
  4. Drain condensate from the main steam header

Explanation

Handholes are small, gasketed openings that let a worker inspect and wash out waterside areas that are too small for a manhole. They are fitted with covers and gaskets and must be tightened and checked for leakage after use.

Question 16Boiler Construction, Design, and Types

Natural circulation in a watertube boiler is produced by:

  1. The density difference between the steam-water mixture and the cooler water Correct answer.
  2. A circulating pump installed in the downcomer circuit
  3. The rotation of the boiler drum during operation
  4. An ejector placed at the economizer outlet

Explanation

Water in the unheated downcomers is denser than the steam-water mixture in the heated riser tubes, so the heavier column flows down and the lighter mixture rises. This density difference drives continuous circulation without any pump.

Question 17Boiler Construction, Design, and Types

A once-through boiler differs from a drum-type boiler in that it:

  1. Passes feedwater through the tubes in a single pass with no steam drum Correct answer.
  2. Recirculates water through the furnace several times before evaporating
  3. Uses a mud drum to collect sludge before evaporation
  4. Relies on a steam drum to remove moisture from the steam

Explanation

In a once-through boiler the feedwater is pumped through the tubes one time and leaves as steam, with no recirculation and no drum. Because there is no drum to act as a buffer or to separate moisture, feedwater quality and control must be very precise.

Question 18Boiler Construction, Design, and Types

A heat recovery steam generator (HRSG) produces steam by:

  1. Passing current through electrodes immersed in the boiler water
  2. Recovering heat from hot exhaust gases such as gas turbine exhaust Correct answer.
  3. Recovering heat only from boiler blowdown
  4. Burning pulverized coal in a cyclone furnace

Explanation

An HRSG has no burner of its own in the simple case; it uses the hot exhaust from a gas turbine or process to evaporate water in tube banks, often with economizer and superheater sections. This is the basis of combined cycle and cogeneration plants.

Question 19Boiler Construction, Design, and Types

In a firetube boiler, the tubes are commonly fastened to the tube sheet by:

  1. Bolting them through the shell with studs
  2. Rolling or expanding the tube ends into the tube holes Correct answer.
  3. Welding them to the baffle plates
  4. Threading them into the steam drum

Explanation

The tube end is inserted into the tube hole and expanded with a roller expander until the metal is pressed tightly against the sheet, which seals the joint and holds the tube. The projecting end is then beaded over or welded to add strength and prevent the tube from pulling out.

Question 20Boiler Construction, Design, and Types

Refractory material in a boiler furnace is used to:

  1. Conduct heat rapidly into the boiler tubes
  2. Withstand high temperature and protect the structure from combustion heat Correct answer.
  3. Support the full weight of the boiler shell
  4. Seal the boiler casing against air inleakage only

Explanation

Refractory is a heat-resistant ceramic material that lines hot areas to protect the steel casing and structural members and to limit heat loss. It also stores heat and helps stabilize combustion, especially at low firing rates.

Question 21Boiler Construction, Design, and Types

Bent tubes are used in many watertube boilers because the bends:

  1. Prevent natural circulation from reversing in the risers
  2. Give a higher pressure rating than straight tubes of the same wall
  3. Eliminate the need for a steam drum in the boiler circuit
  4. Accommodate thermal expansion and let the tubes follow the furnace contour Correct answer.

Explanation

A bent-tube boiler can be laid out so that tubes follow the furnace walls and roof and connect drums separated by a considerable distance. The bends absorb differential expansion between the tubes and the drums, avoiding the high stresses that rigid straight tubes would develop.

Question 22Boiler Construction, Design, and Types

The fusible plug in a firetube boiler is installed:

  1. In the crown sheet, where its fusible metal melts on low water Correct answer.
  2. In the feedwater line to sense water temperature
  3. In the main steam line to relieve overpressure
  4. At the blowdown connection to detect sludge

Explanation

The fusible plug is screwed into the crown sheet or upper firebox sheet, with the fusible alloy on the fireside. If the water level drops and exposes the plug, the alloy melts and releases steam into the firebox, warning the operator and quenching the fire before the sheet overheats and fails.

Question 23Boiler Construction, Design, and Types

Compared with a riveted longitudinal shell seam of equal plate thickness, a welded seam:

  1. Needs no joint efficiency factor because welds cannot fail
  2. Cannot be radiographed, so its strength cannot be verified
  3. Is stronger because rivet holes no longer reduce the effective section Correct answer.
  4. Has exactly the same joint efficiency under every code

Explanation

Riveted seams require drilled or punched holes that remove metal from the plate, and the joint efficiency used in the shell thickness calculation must account for that lost section as well as for the rivet pattern. A welded seam has no holes in the plate, so a properly examined weld earns a higher joint efficiency and a thinner shell for the same pressure.

Question 24Boiler Construction, Design, and Types

In a wetback Scotch boiler, the rear turnaround chamber is:

  1. Left open to the atmosphere so it can be air cooled
  2. Water cooled on the fireside only by a spray nozzle
  3. Surrounded by boiler water, removing refractory from that hot zone Correct answer.
  4. Lined with a thick layer of high-duty firebrick

Explanation

In a wetback design the reversing chamber at the back of the boiler is formed by a water-jacketed section connected to the shell, so boiler water surrounds it. This eliminates the refractory in the hottest turnaround area, reducing maintenance and allowing faster start-up and cooldown.

Question 25Boiler Construction, Design, and Types

An attemperator is used in a boiler to:

  1. Raise the temperature of combustion air entering the furnace
  2. Reduce the pressure of steam entering the turbine
  3. Control superheated steam temperature by injecting water or cooling the steam Correct answer.
  4. Remove dissolved oxygen from the feedwater

Explanation

An attemperator holds final superheat temperature at its design value by spraying high-purity feedwater into the steam or by passing the steam through a heat exchanger cooled by boiler water. This protects the superheater and turbine from overheating when boiler load or gas temperature changes.

Question 26Boiler Construction, Design, and Types

The primary function of a superheater in a boiler unit is to:

  1. Heat the feedwater before it enters the steam drum
  2. Remove suspended moisture droplets from the saturated steam
  3. Heat the combustion air before it enters the furnace
  4. Raise the temperature of the steam above its saturation point Correct answer.

Explanation

A superheater is a bank of tubes placed in the hot gas path downstream of the furnace that adds sensible heat to saturated steam, raising its temperature above the saturation temperature for that pressure. Superheated steam contains no moisture and gives up heat before condensing, which improves turbine efficiency and reduces erosion. Feedwater heating and air heating are handled by separate components.

Question 27Boiler Construction, Design, and Types

In a boiler steam drum, a dry pipe is installed so that steam is:

  1. Directed downward into the mud drum to improve circulation
  2. Collected from the upper part of the drum, away from the bubbling water surface Correct answer.
  3. Used to preheat incoming feedwater before it mixes with boiler water
  4. Distributed evenly across the length of the drum to cool the shell

Explanation

A dry pipe is a perforated or slotted header mounted near the top of the steam drum, above the normal water level. Steam leaving through it has already passed through separators and is drawn away from the turbulent, moisture-laden surface, so carryover of water droplets into the superheater or steam line is reduced. It plays no role in feedwater heating or in promoting circulation.

Question 28Boiler Construction, Design, and Types

In a membrane-wall furnace, the fins welded between adjacent waterwall tubes serve mainly to:

  1. Permit unrestricted relative expansion between neighbouring tubes
  2. Increase the circulation ratio by adding flow area between tubes
  3. Carry the weight of the furnace roof and drum supports
  4. Form a gas-tight furnace enclosure while conducting heat between tubes Correct answer.

Explanation

Welded fins join the tubes into a continuous pressure-tight and gas-tight wall, so the furnace needs no separate refractory casing and air inleakage is prevented. Because the fins are metal and wetted by the tubes, they also conduct heat into the tube wall surface. Expansion is accommodated by the tube bends and by the furnace bottom, not by the fins.

Question 29Combustion, Fuels, and Burner Systems

The combustible component that makes up the largest share of natural gas is:

  1. Butane
  2. Carbon monoxide
  3. Methane Correct answer.
  4. Propane

Explanation

Pipeline natural gas is typically 90 to 95 percent methane by volume, with small amounts of ethane, propane, nitrogen, and carbon dioxide. The heavier hydrocarbons and inert gases are minor constituents.

Question 30Combustion, Fuels, and Burner Systems

The minimum quantity of air needed to burn a fuel completely with no oxygen left over is called:

  1. Excess air
  2. Primary air
  3. Secondary air
  4. Theoretical air Correct answer.

Explanation

Theoretical, or stoichiometric, air supplies exactly enough oxygen to convert all carbon to carbon dioxide and all hydrogen to water. Any air supplied beyond that point is excess air, and primary/secondary refer to how air enters the burner, not how much is needed.

Question 31Combustion, Fuels, and Burner Systems

The flash point of a fuel oil is the temperature at which:

  1. Viscosity drops into the atomizing range
  2. The oil burns continuously once it is ignited
  3. The oil begins to boil and form bubbles
  4. Vapor forms an ignitable mixture near it Correct answer.

Explanation

Flash point is the temperature at which enough vapor is released to form a flammable mixture with air close to the liquid surface. It is a fire-safety property and is always lower than the fire point and the boiling point.

Question 32Combustion, Fuels, and Burner Systems

Before a burner is lighted, the furnace and flue passages must be:

  1. Warmed to at least 200 degrees F
  2. Filled with a rich fuel-air mixture
  3. Purged with air Correct answer.
  4. Sealed and pressurized with gas

Explanation

The pre-purge sweeps any accumulated fuel vapor out of the furnace, breeching, and stack so that ignition cannot cause a furnace explosion. The purge volume and time are set by the burner manufacturer and the flame safeguard programmer.

Question 33Combustion, Fuels, and Burner Systems

Excess air is supplied to a burner mainly to:

  1. Ensure complete combustion Correct answer.
  2. Lower the dew point of the flue gas
  3. Raise the stack temperature
  4. Reduce the fuel burned

Explanation

Because fuel and air are never perfectly mixed, a small amount of air beyond theoretical is supplied so that every fuel molecule finds oxygen. Too much excess air, however, carries heat up the stack and lowers efficiency.

Question 34Combustion, Fuels, and Burner Systems

No. 6 fuel oil is heated before firing mainly to:

  1. Reduce viscosity for atomization Correct answer.
  2. Lower the sulfur content of the oil
  3. Increase the heating value of the oil
  4. Raise the flash point of the oil

Explanation

Heavy oil is nearly solid at room temperature and must be heated so it can be pumped and broken into fine droplets at the nozzle. Good atomization is essential for complete combustion and a clean stack.

Question 35Combustion, Fuels, and Burner Systems

Black smoke from an oil-fired boiler generally indicates:

  1. A cold stack
  2. Too much excess air
  3. Incomplete combustion Correct answer.
  4. Excessive draft

Explanation

Black smoke consists largely of unburned carbon particles, showing that fuel did not receive enough oxygen or enough time and temperature to burn out. It is a direct sign of combustion inefficiency and a fouled stack.

Question 36Combustion, Fuels, and Burner Systems

Complete combustion of a hydrocarbon fuel produces mainly:

  1. Carbon dioxide and water vapor Correct answer.
  2. Carbon dioxide and nitrogen
  3. Carbon monoxide and water
  4. Sulfur dioxide and water vapor

Explanation

In complete combustion the carbon in the fuel is oxidized to carbon dioxide and the hydrogen to water vapor. Nitrogen from the combustion air passes through the furnace essentially unchanged.

Question 37Combustion, Fuels, and Burner Systems

Two identical gas-fired boilers are tested: Boiler A shows 3 percent oxygen in the flue gas and Boiler B shows 9 percent oxygen. Which statement is correct?

  1. Boiler B has less excess air than Boiler A
  2. Boiler A runs with less excess air Correct answer.
  3. Both boilers have the same excess air
  4. Boiler A has a fuel-rich mixture producing CO

Explanation

Oxygen in the flue gas is a direct measure of excess air for a given fuel: lower oxygen means less excess air. With carbon monoxide negligible, less excess air means a smaller stack heat loss and better efficiency.

Question 38Combustion, Fuels, and Burner Systems

Approximately how many cubic feet of air are needed for stoichiometric combustion of 1 cubic foot of natural gas?

  1. 50 cubic feet
  2. 2 cubic feet
  3. 10 cubic feet Correct answer.
  4. 25 cubic feet

Explanation

Methane requires two volumes of oxygen per volume of gas, and air is about 21 percent oxygen, so roughly 9.5 to 10 volumes of air are needed per volume of natural gas burned.

Question 39Combustion, Fuels, and Burner Systems

A flame scanner loses its flame signal while the burner is firing. The flame safeguard system should:

  1. Increase pilot gas flow
  2. Shut off the fuel and lock out Correct answer.
  3. Open the forced draft damper wider
  4. Switch automatically to the standby fuel

Explanation

Loss of flame signal is treated as a flame failure, so the programmer closes the safety shutoff valves and locks out. Manual reset is then required before another light-off attempt.

Question 40Combustion, Fuels, and Burner Systems

Carbon monoxide in flue gas most often results from:

  1. Excessive excess air
  2. Low stack temperature
  3. Too little air or poor mixing Correct answer.
  4. A clean heat transfer surface

Explanation

Carbon monoxide is an intermediate product that must still be oxidized to carbon dioxide; it survives when local oxygen is short or fuel and air are not brought together well.

Question 41Combustion, Fuels, and Burner Systems

A pressure-atomizing oil burner produces a coarse spray with large droplets. The most likely result is:

  1. Smoke and carbon monoxide Correct answer.
  2. Higher combustion efficiency
  3. A lower draft requirement
  4. A leaner flame with less CO

Explanation

Large droplets take longer to vaporize than the flame can provide, so some fuel escapes as carbon particles and carbon monoxide. Fine atomization is a prerequisite for clean, efficient oil combustion.

Question 42Combustion, Fuels, and Burner Systems

Burner manifold gas pressure is below the manufacturer's specified range. The most likely result is:

  1. A larger flame with high CO2
  2. More excess air with a steady flame
  3. A higher stack temperature
  4. A lower firing rate and an unstable flame Correct answer.

Explanation

Manifold pressure determines the gas flow through the burner orifice, so pressure below the specified range reduces heat input. The weakened flame may lift off the burner or become unstable.

Question 43Combustion, Fuels, and Burner Systems

A combustion air proving switch on a forced-draft burner is interlocked so that:

  1. The fuel valves cannot open without airflow Correct answer.
  2. The stack damper opens after ignition
  3. The feedwater pump starts before the burner
  4. The low-water cutoff is bypassed at light-off

Explanation

The proving switch confirms that the fan is moving combustion air, and its interlock keeps the safety shutoff valves closed until airflow is established. This prevents fuel from being admitted to an air-starved furnace.

Question 44Combustion, Fuels, and Burner Systems

Cooling flue gas below the acid dew point in an oil-fired boiler causes:

  1. Reduced excess air
  2. Acid corrosion of the stack Correct answer.
  3. Increased natural draft
  4. Higher combustion efficiency

Explanation

Sulfur in the oil burns to sulfur dioxide and some sulfur trioxide, which combine with moisture to form sulfurous and sulfuric acid. Below the acid dew point these condense on metal surfaces and corrode the stack and breeching.

Question 45Combustion, Fuels, and Burner Systems

For a given fuel and firing rate, as excess air increases the carbon dioxide content of the flue gas:

  1. Stays the same
  2. Increases then holds constant
  3. Decreases Correct answer.
  4. Increases

Explanation

Extra air adds nitrogen and oxygen to the flue gas without adding carbon, so the carbon dioxide percentage is diluted and falls. This is why CO2 readings are used as a tuning indicator for a fixed fuel.

Question 46Combustion, Fuels, and Burner Systems

Burner turndown ratio is the ratio of:

  1. Primary air to secondary air
  2. Maximum rate to minimum stable rate Correct answer.
  3. Stack draft to furnace draft
  4. Fuel pressure to atomizing pressure

Explanation

Turndown compares the highest firing rate the burner can deliver with the lowest rate at which it still holds a stable flame. A wide turndown lets one burner follow load changes without short cycling.

Question 47Combustion, Fuels, and Burner Systems

A gas burner flame that is long, yellow, and lazy most likely indicates:

  1. Too little air or overfiring Correct answer.
  2. A correct stoichiometric mixture
  3. Too much primary air
  4. Excessive furnace draft

Explanation

A long yellow flame shows fuel-rich combustion: not enough air, too much fuel for the air supplied, or poor mixing at the burner. A properly adjusted gas flame is short, blue, and well defined.

Question 48Combustion, Fuels, and Burner Systems

Primary air in a gas burner is the air that:

  1. Is drawn in around the flame at the burner throat
  2. Provides the secondary combustion air
  3. Mixes with the fuel before it leaves the burner Correct answer.
  4. Cools the burner housing

Explanation

Primary air is premixed with the fuel as it leaves the burner to begin combustion, while secondary air is supplied around the flame to complete the burning. The split between the two shapes flame length and stability.

Question 49Combustion, Fuels, and Burner Systems

A fuel oil contains 87 percent carbon, 12 percent hydrogen, and 1 percent sulfur by mass. Using 11.5 lb of air per lb of carbon, 34.5 lb per lb of hydrogen, and 4.3 lb per lb of sulfur, the theoretical air required per pound of fuel is:

  1. About 22 lb
  2. About 10 lb
  3. About 18 lb
  4. About 14 lb Correct answer.

Explanation

Multiplying each element by its air requirement gives 0.87 x 11.5 = 10.0, 0.12 x 34.5 = 4.1, and 0.01 x 4.3 = 0.04, for a total of roughly 14.2 lb of air per pound of fuel.

Question 50Combustion, Fuels, and Burner Systems

If the main flame fails to prove during the trial-for-ignition period, the programmer must:

  1. Hold the fuel valves open for one more trial period
  2. Reduce the firing rate and retry automatically
  3. Close the fuel valves and lock out Correct answer.
  4. Leave the pilot on and continue at low fire

Explanation

Flame must be proven within the timed trial-for-ignition period; if it is not, the programmer closes the safety shutoff valves and locks out. This prevents unburned fuel from accumulating in the furnace.