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BD First Class Boiler Attendant study materials
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BD First Class Boiler Attendant practice questions

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Question 1Boiler Laws, Rules and Regulations

Under the Boiler and Pressure Vessel Regulation, who holds the primary legal responsibility for ensuring that a boiler is operated safely on a daily basis?

  1. The fuel supplier
  2. The water treatment vendor
  3. The insurance surveyor
  4. The boiler attendant on duty Correct answer.

Explanation

The regulation places day-to-day safe operation squarely on the certified attendant in charge of the boiler. The attendant must monitor water level, pressure, and firing conditions and act promptly on any abnormality. Other parties support the operation but do not carry this operational duty.

Question 2Boiler Laws, Rules and Regulations

What is the general purpose of a statutory boiler inspection performed by an authorized inspector?

  1. To calculate the plant's annual fuel budget
  2. To confirm the boiler meets safety requirements and remains fit for continued service Correct answer.
  3. To train new attendants in firing technique
  4. To set the price of the boiler for resale

Explanation

Statutory inspections exist to verify that a boiler still satisfies the safety requirements of the regulation after a period of service. The inspector examines the pressure parts, safety devices, and records to decide whether continued operation is permitted. Commercial, training, and budgeting matters lie outside this purpose.

Question 3Boiler Laws, Rules and Regulations

A boiler is required to have a safety valve. What is the primary function of this device under boiler regulations?

  1. To admit feedwater when the water level falls
  2. To silence the low-water alarm during start-up
  3. To discharge steam automatically before pressure exceeds the maximum allowable working pressure Correct answer.
  4. To drain condensate from the steam header during warm-up

Explanation

The safety valve is the final protective device against overpressure and must open automatically at or below the set pressure. It protects the pressure parts from exceeding the maximum allowable working pressure. Drainage, feed control, and alarm silencing are handled by entirely different equipment.

Question 4Boiler Laws, Rules and Regulations

Why does the regulation require the attendant to keep a boiler water level visible in the gauge glass at all times?

  1. So the true water level can be confirmed and low water detected before damage occurs Correct answer.
  2. So blowdown can be performed without opening any valve
  3. So the gauge glass can be used to measure steam pressure
  4. So the boiler can be fired without a low-water cutoff

Explanation

A clear gauge glass lets the attendant verify the actual water level and catch a low-water condition early. Losing the level risks overheating of heating surfaces and a serious failure. The glass indicates level only and cannot substitute for pressure gauges or protective cutoffs.

Question 5Boiler Laws, Rules and Regulations

Which document must generally be made available to an inspector during a boiler inspection?

  1. The vendor's equipment catalogue
  2. The attendant's personal tax return
  3. The boiler operating and maintenance records Correct answer.
  4. The plant's marketing brochure

Explanation

Operating and maintenance records show the boiler's service history and demonstrate that required checks have been carried out. Inspectors rely on these records together with the physical examination. Personal, promotional, and catalogue documents have no bearing on the inspection.

Question 6Boiler Laws, Rules and Regulations

What does the maximum allowable working pressure marked on a boiler's nameplate represent?

  1. The test pressure used for the original hydrostatic test
  2. The highest pressure at which the boiler may legally be operated Correct answer.
  3. The pressure at which the safety valve is factory-sealed shut
  4. The average pressure observed over the past year

Explanation

The nameplate value is the upper limit of normal operating pressure permitted by the regulation. Safety devices are set so that this limit is not exceeded in service. It is not an average reading, a sealed setting, or the higher hydrostatic test pressure.

Question 7Boiler Laws, Rules and Regulations

The low-water fuel cutoff on a steam boiler trips and the burner shuts down. According to good regulatory practice, what should the attendant do before restarting?

  1. Reset the cutoff immediately and resume firing
  2. Verify the actual water level in the gauge glass and find the cause of the trip Correct answer.
  3. Bypass the cutoff to keep steam production up
  4. Add water and restart without any check

Explanation

A low-water trip signals a real hazard, so the attendant must confirm the true level in the gauge glass and investigate why it occurred. Restarting is permitted only once the level is proven safe and the cause is understood. Immediate reset, blind restart, or bypassing defeats the protective device.

Question 8Boiler Laws, Rules and Regulations

An attendant finds the safety valve set pressure lower than the boiler's maximum allowable working pressure. What is the appropriate action?

  1. Ignore it because a lower setting is always safer
  2. Increase the firing rate to raise steam pressure
  3. Report it so the valve is adjusted by an authorized person to the correct setting Correct answer.
  4. Plug the valve so steam is not wasted

Explanation

The safety valve must be set to protect the boiler at its maximum allowable working pressure, and adjustment is restricted to authorized personnel. A setting below that value causes nuisance lifting and reduced capacity, while plugging is dangerous. Firing harder does not correct a wrong setting.

Question 9Boiler Laws, Rules and Regulations

During a shift, the attendant must leave the boiler room briefly. What does the regulation generally require regarding the boiler during that absence?

  1. Firing must be supervised or the boiler left in a safe, attended-equivalent condition Correct answer.
  2. The low-water cutoff may be switched off to avoid nuisance trips
  3. The boiler may be left firing unattended for up to one hour
  4. The safety valve may be gagged to prevent lifting

Explanation

Unattended firing is not permitted; the boiler must remain under supervision or be placed in a condition that is safe without an attendant. Gagging the safety valve or disabling the cutoff creates hazards and is prohibited. A fixed unattended firing period is not allowed by the regulation.

Question 10Boiler Laws, Rules and Regulations

A boiler is to be taken out of service for internal cleaning. Which regulatory step is normally required before internal work begins?

  1. Internal work may start as soon as the fire is out
  2. The safety valve must be removed and left off during cleaning
  3. The boiler must be cooled, drained, isolated, and the fuel and steam supplies locked out Correct answer.
  4. The boiler may be opened while still under pressure if work is quick

Explanation

Before internal work, the boiler must be depressurized, drained, and positively isolated from fuel, steam, and feed sources. Lockout procedures prevent accidental admission of energy while people are inside. Opening a pressurized boiler or omitting isolation is extremely dangerous and non-compliant.

Question 11Boiler Laws, Rules and Regulations

Which of the following best describes the role of the person in charge of a boiler plant under the regulation?

  1. They design the boiler pressure parts
  2. They personally fire every boiler on every shift
  3. They direct the safe operation and ensure attendants are competent and records kept Correct answer.
  4. They approve the plant's electricity tariff

Explanation

The person in charge oversees safe operation, confirms that attendants are trained and certified, and ensures records are maintained. This supervisory role does not require firing every boiler personally. Tariff approval and pressure-part design fall outside the regulation's scope.

Question 12Boiler Laws, Rules and Regulations

A boiler nameplate shows a design pressure, but the operating permit issued by the authority specifies a lower maximum. Which value governs operation?

  1. The pressure at which the plant runs most efficiently
  2. Whichever value the attendant prefers
  3. The higher nameplate design pressure
  4. The lower value stated in the operating permit Correct answer.

Explanation

Where the authority issues a permit with a specific limit, that limit governs operation even if the nameplate design pressure is higher. The permit reflects the conditions under which continued operation is approved. Personal preference and efficiency targets cannot override the permitted limit.

Question 13Boiler Laws, Rules and Regulations

The attendant notices that the pressure gauge reading has been steadily drifting and no longer returns to zero when the boiler is cold. What action is most consistent with regulatory requirements?

  1. Have the gauge checked and recalibrated or replaced before continued reliance on it Correct answer.
  2. Continue operating and add a mental correction to the reading
  3. Increase the safety valve set pressure to compensate
  4. Record the drift in the log and take no other action

Explanation

Pressure gauges must be accurate because they are the attendant's guide to safe operation, so a faulty gauge must be repaired, recalibrated, or replaced. Mentally correcting a reading is unreliable and unsafe. Adjusting the safety valve or merely logging the fault does not restore accuracy.

Question 14Boiler Laws, Rules and Regulations

Which practice is required when blowing down a boiler water column or gauge glass?

  1. Blow down only when the glass is completely empty
  2. Blow down while the boiler is being hydrostatically tested
  3. Leave the drain valve open after blowdown
  4. Blow down with the boiler at a safe level and confirm the glass refills properly afterward Correct answer.

Explanation

Blowdown of the water column confirms that connections are clear and that the glass refills to show the true level. The attendant must watch the refill to verify correct operation. Blowing down with an empty glass or leaving the drain open risks a false low-water reading and is unsafe.

Question 15Boiler Laws, Rules and Regulations

An inspector finds that the boiler logbook has not been completed for several weeks. What is the most likely regulatory consequence?

  1. The boiler is automatically scrapped
  2. No action is taken because logs are optional
  3. The attendant is promoted to supervisor
  4. The omission is recorded as a non-compliance requiring correction Correct answer.

Explanation

Operating records are a required part of demonstrating safe operation, so missing entries are recorded as a non-compliance to be corrected. The authority may require corrective action and follow-up. Scrapping, promotion, or ignoring the gap does not follow from a record-keeping failure.

Question 16Boiler Laws, Rules and Regulations

A new attendant is assigned to fire a high-capacity boiler. Under the regulation, which condition must be satisfied?

  1. The attendant must be at least the age of the plant manager
  2. The attendant must supply their own safety valve
  3. The attendant must hold the certificate of competency required for that boiler class Correct answer.
  4. The attendant must have read the manufacturer's brochure

Explanation

The regulation ties the class of boiler to the grade of certificate the attendant must hold. Only a properly certified person may take charge of firing that boiler. Reading brochures, matching a manager's age, or supplying parts does not satisfy the certification requirement.

Question 17Boiler Laws, Rules and Regulations

A plant plans to alter a boiler by replacing its burner with a higher-output model. What does the regulation generally require before the altered boiler is returned to service?

  1. Only a note in the logbook by the attendant
  2. Nothing, because the boiler shell is unchanged
  3. Approval of the alteration and re-inspection confirming the safety devices suit the new duty Correct answer.
  4. A verbal notice to the fuel supplier

Explanation

Alterations affecting boiler output or safety require approval and re-inspection so that protective devices match the new duty. The safety valve capacity, controls, and ratings must all remain adequate. A logbook note or informal notice does not satisfy this requirement.

Question 18Boiler Laws, Rules and Regulations

Two attendants disagree about whether a boiler with a slightly weeping safety valve may remain in service until the next scheduled shutdown. What is the correct regulatory position?

  1. A weeping safety valve is defective and must be reported and repaired without delay Correct answer.
  2. It may be kept in service if the leak is logged
  3. It may be kept in service if the firing rate is reduced
  4. It may remain in service because it still relieves pressure

Explanation

A safety valve that weeps is not seating correctly and may fail to protect the boiler, so it must be reported and repaired promptly. Continued service with a known defective protective device is not permitted. Logging the defect or reducing firing does not restore the valve's function.

Question 19Boiler Laws, Rules and Regulations

A boiler is sold and reinstalled at a different site. Which statement best reflects typical regulatory requirements for the move?

  1. The new owner may set the maximum pressure freely
  2. No inspection is needed because the boiler was previously approved
  3. The original permit travels with the boiler and remains valid
  4. The boiler must be re-inspected and a new operating permit obtained for the new location Correct answer.

Explanation

Reinstallation at a new site changes the operating context, so the boiler must be re-inspected and a permit obtained for that location. The original permit applies to the previous installation, not to the boiler wherever it goes. The new owner cannot set pressure limits at will.

Question 20Boiler Laws, Rules and Regulations

An attendant discovers that a required low-water cutoff has been deliberately bypassed by a previous shift. Which response best satisfies the attendant's legal duty?

  1. Restore the device to service, report the bypass, and record the event Correct answer.
  2. Operate manually and say nothing
  3. Leave the bypass in place to avoid conflict with the other shift
  4. Remove the cutoff entirely to simplify operation

Explanation

The attendant has a duty to ensure protective devices are functional, so the bypass must be corrected, reported, and documented. Concealing a known defeat of a safety device exposes the plant to serious risk and liability. Manual operation or removal does not satisfy this duty.

Question 21Boiler Types, Construction and Design

Which boiler component is designed to absorb the remaining heat from combustion gases after they leave the generating bank or superheater, improving overall thermal efficiency?

  1. Superheater
  2. Economiser Correct answer.
  3. Furnace
  4. Steam drum

Explanation

An economiser is a feedwater preheating device placed in the gas path downstream of the evaporating and superheating surfaces. It extracts sensible heat from the leaving gases and transfers it to the incoming feedwater, lowering stack temperature and raising boiler efficiency.

Question 22Boiler Types, Construction and Design

In a fire-tube boiler, where do the hot combustion gases flow?

  1. Inside the tubes surrounded by water Correct answer.
  2. Through the superheater coils before the drum
  3. Through a separate water-walled furnace only
  4. Outside the tubes while water passes inside

Explanation

The defining feature of a fire-tube boiler is that hot gases pass through tubes that are submerged in water contained in the shell. Heat travels from the gas through the tube wall into the surrounding water, which is the reverse of a water-tube arrangement.

Question 23Boiler Types, Construction and Design

What is the primary purpose of the steam drum in a water-tube boiler?

  1. To preheat the incoming combustion air
  2. To separate steam from water and provide water storage Correct answer.
  3. To grind and feed coal to the burners
  4. To support the superheater elements mechanically

Explanation

The steam drum provides a space where steam and water separate, holds a water reserve to absorb load swings, and allows blowdown and chemical dosing. Steam leaves from the top while saturated water returns to the generating tubes.

Question 24Boiler Types, Construction and Design

A boiler is described as having a 'D-type' or 'D-shaped' configuration. This classification refers mainly to which feature?

  1. The shape of the burner throat
  2. The arrangement of the furnace and convection bank relative to the drum Correct answer.
  3. The profile of the chimney stack
  4. The layout of the feedwater pump house

Explanation

In a D-type water-tube boiler the furnace and convection bank sit side by side, with the steam drum on top and water drums below, giving a cross-section resembling the letter D. The name describes the overall pressure-part layout, not external equipment.

Question 25Boiler Types, Construction and Design

Which material property is most important when selecting tube steel for the high-temperature superheater of a high-pressure boiler?

  1. Electrical resistivity
  2. Room-temperature hardness
  3. Creep strength at operating metal temperature Correct answer.
  4. Coefficient of thermal expansion at ambient conditions

Explanation

Superheater tubes operate at elevated metal temperatures under internal pressure, so resistance to creep deformation over the design life governs material selection. Alloy steels with adequate creep rupture strength at the calculated tube-wall temperature are chosen.

Question 26Boiler Types, Construction and Design

What is the function of a superheater in a boiler?

  1. To raise the temperature of saturated steam above its saturation point Correct answer.
  2. To remove dissolved oxygen from the feedwater
  3. To cool the furnace walls during start-up
  4. To filter solid particles from the flue gas

Explanation

A superheater transfers heat from the hot gases to saturated steam, raising its temperature above the saturation value for the drum pressure. This dry, hotter steam improves cycle efficiency and reduces condensation losses in the turbine.

Question 27Boiler Types, Construction and Design

A boiler is fitted with a water wall constructed of closely spaced tubes lining the furnace. What is the main benefit of this construction?

  1. It protects the refractory and absorbs radiant heat to generate steam Correct answer.
  2. It eliminates the need for a steam drum
  3. It allows the boiler to operate without a safety valve
  4. It increases the flue gas velocity through the convection bank

Explanation

Water walls line the furnace with tubes carrying water, absorbing radiant heat from the flame while shielding the furnace casing and refractory from extreme temperatures. This raises steam output and extends the life of the furnace structure.

Question 28Boiler Types, Construction and Design

A boiler has a rated evaporation of 10 000 kg/h of steam at a feedwater temperature of 100 °C and produces dry saturated steam at 10 bar gauge. Using an approximate specific enthalpy rise of 2 000 kJ/kg, what is the approximate heat output in kW?

  1. 11 111 kW
  2. 2 778 kW
  3. 20 000 kW
  4. 5 556 kW Correct answer.

Explanation

Heat output equals mass flow times enthalpy rise: 10 000 kg/h × 2 000 kJ/kg = 20 000 000 kJ/h. Dividing by 3 600 s/h gives about 5 556 kJ/s, that is 5 556 kW.

Question 29Boiler Types, Construction and Design

In a shell boiler, why is the furnace tube corrugated rather than plain?

  1. To reduce the weight of the pressure shell
  2. To allow the boiler to be fired without water
  3. To accommodate thermal expansion and improve heat transfer Correct answer.
  4. To simplify the attachment of the burner

Explanation

Corrugations give the furnace tube flexibility so it can expand and contract with temperature changes without overstressing the end plates. The corrugations also increase surface area and promote turbulence, improving heat transfer to the water.

Question 30Boiler Types, Construction and Design

What is the purpose of a baffle arrangement in the convection bank of a boiler?

  1. To distribute feedwater evenly to the drum
  2. To guide gas flow across the tubes in a controlled path for effective heat transfer Correct answer.
  3. To support the boiler on its foundations
  4. To regulate the fuel supply to the burners

Explanation

Baffles direct the combustion gases so they cross the tube bank in a defined pattern, increasing gas velocity and residence time over the surfaces. This improves the convective heat transfer coefficient and reduces gas bypassing.

Question 31Boiler Types, Construction and Design

A boiler is to be installed where rapid load swings are expected and floor space is limited. Which design characteristic would best suit this duty?

  1. A water-tube boiler with a small water inventory and fast response Correct answer.
  2. A large shell boiler with a high water content
  3. A brick-set boiler with thick refractory walls
  4. A waste-heat boiler dependent on a fixed process gas flow

Explanation

A water-tube boiler holds less water per unit output, so it can raise steam quickly and follow load changes without large storage effects. Its compact pressure parts also suit restricted floor space better than a bulky shell boiler.

Question 32Boiler Types, Construction and Design

Why are boiler tubes often expanded into the tube plate or drum rather than only welded?

  1. Expansion removes the need for any tube support
  2. Expansion increases the tube bore for higher flow
  3. Expansion gives a reliable pressure-tight joint and allows some movement Correct answer.
  4. Expansion lowers the tube metal temperature directly

Explanation

Roller expansion swages the tube end into the plate hole, producing a tight interference fit that seals against pressure and permits limited relative movement. It is a proven method for drum and tube plate joints in many boiler designs.

Question 33Boiler Types, Construction and Design

What is the main reason for fitting an air preheater in the flue gas path of a large boiler?

  1. To remove moisture from the fuel
  2. To increase the pressure of the combustion air
  3. To cool the flue gas below its acid dew point
  4. To recover heat from the leaving gases and improve combustion efficiency Correct answer.

Explanation

An air preheater transfers heat from the exhaust gas to the incoming combustion air, reducing stack loss and raising overall efficiency. Preheated air also improves ignition and combustion stability.

Question 34Boiler Types, Construction and Design

In a water-tube boiler, what is the role of the downcomers?

  1. To carry cooler water from the drum to the lower headers, completing the circulation loop Correct answer.
  2. To supply fuel to the furnace
  3. To carry steam from the drum to the superheater
  4. To drain condensate from the steam mains

Explanation

Downcomers are unheated or lightly heated pipes that take water from the drum down to the lower distribution headers. The density difference between this cooler column and the heated riser tubes drives natural circulation.

Question 35Boiler Types, Construction and Design

What does the term 'balanced draught' mean in a boiler installation?

  1. The steam and feedwater flows are balanced
  2. Forced draught and induced draught fans work together to hold the furnace near atmospheric pressure Correct answer.
  3. The fuel and air supplies are exactly equal in mass
  4. The boiler operates without any fans

Explanation

In balanced draught, a forced draught fan supplies air to the furnace while an induced draught fan draws gases out, keeping the furnace pressure slightly below atmospheric. This prevents hot gas and flame from escaping while avoiding excessive air ingress.

Question 36Boiler Types, Construction and Design

Which feature distinguishes a once-through boiler from a drum-type boiler?

  1. It operates only at atmospheric pressure
  2. It has no superheater surface
  3. Feedwater passes through the tubes once and leaves as steam without a separating drum Correct answer.
  4. It uses only natural circulation

Explanation

In a once-through design the feedwater is evaporated completely as it passes through the tube circuit, and the outlet is steam, so no steam drum is needed. Drum boilers rely on recirculation and separation of steam from water in the drum.

Question 37Boiler Types, Construction and Design

A boiler's generating tubes show a persistent pattern of overheating on the furnace side of one wall. Which design-related cause is most likely?

  1. A low stack gas temperature
  2. Excessive feedwater temperature
  3. An undersized steam drum
  4. Poor circulation or an excessive local heat flux in that tube circuit Correct answer.

Explanation

Local overheating of furnace tubes usually points to inadequate cooling of the tube wall, caused by restricted circulation or a heat flux that exceeds the tube's design capability. Deposit build-up can aggravate the same effect.

Question 38Boiler Types, Construction and Design

Why is a supercritical boiler able to operate without a steam drum?

  1. Steam is generated in the superheater alone
  2. Above the critical pressure there is no distinct phase change, so steam and water do not separate Correct answer.
  3. Supercritical boilers use only fire-tube construction
  4. The drum is replaced by a larger feedwater tank

Explanation

Above the critical pressure, water transforms continuously into a dense fluid without a latent vaporisation stage, so no steam-water interface exists to separate. The circuit is therefore once-through, and a drum would serve no purpose.

Question 39Boiler Types, Construction and Design

A boiler designer must limit the gas-side exit temperature of the economiser. What is the principal reason?

  1. To limit the steam drum pressure
  2. To keep the feedwater below saturation
  3. To keep the metal temperature above the acid dew point of the flue gas Correct answer.
  4. To reduce the air preheater duty

Explanation

If the economiser surface falls below the acid dew point of the gas, condensed acid will corrode the tubes and cause fouling. Design exit gas temperatures are therefore kept above that value, or corrosion-resistant materials are used.

Question 40Boiler Types, Construction and Design

In a natural-circulation boiler, what happens to circulation if the steam pressure is raised toward the critical value while heat input stays constant?

  1. Circulation is unaffected by pressure
  2. Circulation becomes stronger because steam is denser
  3. Circulation reverses direction permanently
  4. The density difference between risers and downcomers falls, weakening the circulating head Correct answer.

Explanation

Natural circulation depends on the density difference between the steam-water mixture in the heated risers and the cooler water in the downcomers. As pressure rises, the densities of the two phases converge, so the driving head diminishes.

Question 41Boiler Types, Construction and Design

Why are furnace walls in large boilers often constructed as membrane or finned tube panels?

  1. To eliminate the need for water circulation
  2. To reduce the boiler's steam output
  3. To allow the furnace to be cooled by air alone
  4. To form a gas-tight enclosure and improve radiant heat absorption per unit area Correct answer.

Explanation

Welding fins between adjacent tubes creates a continuous gas-tight wall that replaces much of the refractory and casing. The fins also conduct heat between tubes, increasing the effective radiant surface and improving absorption.

Question 42Boiler Types, Construction and Design

A boiler originally designed for saturated steam duty is to be uprated to supply superheated steam at the same pressure. Which change is most directly required?

  1. Adding more economiser surface only
  2. Adding superheater surface in a suitable gas temperature zone Correct answer.
  3. Reducing the furnace volume
  4. Increasing the steam drum diameter

Explanation

Superheating requires additional heat transfer surface placed where the gas temperature is high enough to raise the steam temperature. The superheater must also be matched to the desired outlet temperature and tube material limits.

Question 43Boiler Types, Construction and Design

What is the purpose of the steam drum internals such as cyclone separators and scrubbers?

  1. To cool the drum metal during start-up
  2. To increase the drum's pressure rating
  3. To remove water droplets from steam before it leaves the drum Correct answer.
  4. To distribute gas across the tube bank

Explanation

Mechanical separators spin out coarse water droplets, and scrubbers remove finer carryover, producing drier steam. Dry steam protects the superheater and turbine from deposits and erosion caused by water carryover.

Question 44Boiler Types, Construction and Design

Which statement best explains why a fire-tube boiler is generally limited to lower steam pressures than a water-tube boiler?

  1. Fire-tube boilers have no safety valves
  2. Water-tube boilers contain no pressurised parts
  3. The large cylindrical shell must resist pressure over a big diameter, so wall thickness becomes excessive Correct answer.
  4. Fire-tube boilers cannot burn liquid fuels

Explanation

In a fire-tube boiler the whole shell is a pressure vessel of large diameter, so hoop stress rises steeply with pressure and the required plate thickness becomes impractical. Water-tube boilers use small-diameter tubes that withstand high pressure with modest wall thickness.

Question 45Boiler Fittings, Mountings and Accessories

Which fitting is installed on a boiler to prevent the shell from being overpressurised by discharging steam automatically at a set pressure?

  1. Safety valve Correct answer.
  2. Feed check valve
  3. Air vent cock
  4. Blowdown valve

Explanation

A safety valve is the final protective device that opens automatically when pressure reaches its set point and reseats when pressure falls. It must have sufficient capacity to discharge all steam the boiler can generate without allowing pressure to rise above the maximum permissible working pressure.

Question 46Boiler Fittings, Mountings and Accessories

What is the primary purpose of a fusible plug fitted in the crown of a boiler furnace?

  1. To relieve excess pressure before the safety valve lifts
  2. To indicate the temperature of the flue gases
  3. To give warning of low water level by melting and releasing steam Correct answer.
  4. To drain sludge from the lowest part of the shell

Explanation

A fusible plug contains a low-melting alloy that melts if the metal around it becomes overheated through low water, allowing steam to escape into the furnace as an audible warning. This alerts the attendant before the crown plates are seriously damaged.

Question 47Boiler Fittings, Mountings and Accessories

A boiler is fitted with two independently mounted safety valves. What is the usual requirement for the pressure at which the second valve begins to lift?

  1. At a pressure slightly above the first, but not exceeding the maximum permissible working pressure Correct answer.
  2. Only after the first valve has failed completely
  3. At the same instant and pressure as the first valve
  4. At exactly half the maximum permissible working pressure

Explanation

Where more than one safety valve is fitted, one is set to lift at or below the working pressure and the other is set slightly higher, so that it opens only if pressure continues to rise. Neither valve may be set above the maximum permissible working pressure of the boiler.

Question 48Boiler Fittings, Mountings and Accessories

Why must the water level gauge glass be blown through periodically while the boiler is in service?

  1. To reduce the pressure inside the gauge glass
  2. To cool the glass and prevent thermal cracking
  3. To clear sludge and confirm that the indicated level is true Correct answer.
  4. To test the strength of the gauge glass fittings

Explanation

Blowing through with the drain and steam/water cocks proves that the connections are clear and that the water level shown is genuine. Sludge or scale blocking a connection can give a false high or low reading, which is dangerous.

Question 49Boiler Fittings, Mountings and Accessories

What is the function of a feed check valve in the feedwater line to a boiler?

  1. To regulate the quantity of steam leaving the boiler
  2. To drain water from the boiler during blowdown
  3. To isolate the boiler from the steam main
  4. To allow feedwater into the boiler while preventing backflow of boiler water Correct answer.

Explanation

The feed check valve opens in the direction of flow to admit feedwater and closes automatically when the feed pump stops, preventing hot boiler water from being forced back into the feed line. It is normally the last valve before the boiler on the feed line.

Question 50Boiler Fittings, Mountings and Accessories

Which device is required to protect a boiler against the danger of the burner firing while the furnace contains unburnt fuel?

  1. Flame failure and purge interlock system Correct answer.
  2. Water level gauge glass
  3. Main steam stop valve
  4. Pressure reducing valve

Explanation

A flame failure device shuts off fuel if the flame is lost, and a purge interlock forces air through the furnace before ignition to clear any accumulated combustible gases. Together they prevent furnace explosions during light-up and operation.