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Quizzes > Science

Boiler Test: High-Pressure Questions on Safety and Operation

Quick, free boiler quiz with instant results to check high-pressure safety and operation

Editorial: Review CompletedCreated By: Jonathan MillerUpdated Aug 27, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for boiler exam quiz on a coral background

This high-pressure boiler test helps you check your knowledge of safe operation, controls, and shutdowns with instant feedback. If you want to sharpen related skills, try our Gas Safe inspection questions and review basics with an hvac quiz. For safety devices, practice with the temperature pressure relief valve quiz. Build confidence before your next shift or exam.

What is the primary function of a boiler in an industrial process?
Filter impurities from water
Increase fuel calorific value
Convert feedwater into steam
Cool down exhaust gases
A boiler's main purpose is to heat water under pressure to produce steam that drives turbines or process heating. Steam generation is fundamental to power and process industries. Other functions like filtration and cooling are done by ancillary equipment.
Which type of boiler has water-filled tubes surrounded by combustion gases?
Fire-tube boiler
Electric boiler
Cast iron boiler
Water-tube boiler
Water-tube boilers circulate water inside tubes which are heated externally by combustion gases, allowing higher pressures. Fire-tube boilers run gases inside tubes surrounded by water. Water-tube designs are common for high-pressure applications.
What safety device prevents overpressure in a boiler?
Pressure gauge
Flow meter
Safety valve
Water level indicator
Safety valves automatically discharge steam when pressure exceeds the set limit to protect the boiler. Gauges only indicate pressure, they do not relieve it. Properly calibrated safety valves are mandatory under ASME.
What is boiler blowdown used for?
Remove dissolved solids
Increase steam temperature
Control draft
Reduce fuel consumption
Blowdown periodically removes concentrated dissolved solids and sediments from the boiler to prevent scale and corrosion. It does not change steam temperature directly. Controlling dissolved solids maintains heat transfer efficiency.
Which instrument measures boiler drum water level?
Sight glass
Flow transmitter
Thermocouple
Manometer
Sight glasses provide a visual indication of water level in the boiler drum. Thermocouples measure temperature, not level. Accurate water-level monitoring is critical for safe operation.
What is the usual maximum working pressure for a high-pressure boiler?
Above 15 psi
Below 1 psi
Below 5 psi
Above 1000 psi
By definition, a high-pressure boiler operates above 15 psi for steam service. Low-pressure systems are under 15 psi. Ultra-high pressure (1000+ psi) exists but is specialized.
What is the effect of scale formation on boiler tubes?
Reduces heat transfer
Improves tube strength
Increases steam production
Decreases water hardness
Scale is an insulating deposit that reduces heat transfer from flue gases to water, causing tube overheating and failure. It does not improve strength or production. Proper water treatment prevents scale.
What type of draft uses induced fan downstream of boiler?
Natural draft
Balanced draft
Forced draft
Induced draft
An induced draft fan draws flue gases out of the boiler, creating a negative pressure. A forced draft fan pushes air in. Balanced uses both fans.
Which flame color indicates complete combustion?
Red
Orange
Yellow
Blue
A blue flame shows that fuel is burning completely with sufficient oxygen. Yellow or orange flames indicate incomplete combustion and soot. Complete combustion maximizes efficiency.
What is the purpose of an economizer in a boiler system?
Reduce draft loss
Clean boiler tubes
Separate steam and water
Preheat feedwater with flue gases
Economizers capture waste heat from flue gases to preheat feedwater, improving efficiency. They do not separate steam or reduce draft. Preheating reduces fuel consumption.
Which scale-forming element is most problematic in boiler water?
Calcium
Sodium
Iron
Chloride
Calcium salts precipitate as scale at high temperatures, severely reducing heat transfer. Iron oxide causes sludge but less scale. Chloride and sodium remain soluble.
What component removes oxygen from feedwater?
Economizer
Heat exchanger
Deaerator
Steam trap
A deaerator heats feedwater and vents oxygen and carbon dioxide to prevent corrosion. Heat exchangers transfer heat but don't remove gases. Steam traps remove condensate.
Which test checks for water purity in a boiler?
Hardness test
pH test
TDS test
Dissolved oxygen test
A Total Dissolved Solids (TDS) test measures mineral concentration, which must be controlled to prevent scale. pH and oxygen tests are important but do not measure salts. Hardness relates to scale but TDS is total mineral content.
What is the effect of low water level in a boiler?
Higher feedwater temperature
Increased efficiency
Reduced draft
Tube overheating
When water level drops too low, exposing tubes to excessive heat leads to hot spots and tube failure. It doesn't affect draft. Maintaining proper level is a critical safety aspect.
Which gas analyzer parameter indicates combustion efficiency?
Oxygen content
Nitrogen oxide
Sulfur dioxide
Carbon monoxide only
Measuring O? in flue gas shows excess air levels, which directly relate to combustion efficiency. CO and NOx provide pollution data. Optimal O? ensures efficient fuel use.
What does 'superheated steam' mean?
Steam heated above its saturation temperature
Condensed steam
Wet steam containing droplets
Steam at saturation temperature
Superheated steam is heated beyond its boiling point at a given pressure, making it dry and higher in energy. Saturated steam is at boiling temperature. Wet steam contains moisture.
Which piping component protects against overpressure between steam header and boiler?
Feedwater pump
Pressure gauge
Safety valve only
Stop valve and check valve in series
A properly arranged stop valve with a check valve prevents steam backflow and isolates the boiler, protecting from header overpressure. Safety valves relieve, but isolation requires valves.
What control uses drum level and flow to maintain proper water level during load swings?
Three-element control
Single-element control
Cascade control
Feedforward control
Three-element control uses drum level, steam flow, and feedwater flow for stable water-level regulation during load changes. Single-element uses only drum level. This is the ASME-recommended method.
In a boiler heat balance, which loss is typically largest?
Radiation loss
Dry flue gas loss
Blowdown loss
Moisture loss
Dry flue gas carries significant heat away, often the largest loss in a boiler. Radiation losses are comparatively small. Measuring and minimizing flue gas temperature improves efficiency.
What is the effect of excess air on boiler efficiency?
Increases steam purity
Decreases efficiency
Reduces flue gas temperature
Eliminates carbon dioxide
Too much excess air cools the flame and carries heat up the stack, reducing efficiency. It doesn't improve purity. Optimal excess air is needed to ensure complete combustion without undue heat loss.
Which chemical prevents scale and sludge in boilers by threshold inhibition?
Sodium chloride
Polymaleic acid
Sodium sulfate
Calcium carbonate
Polymaleic acid binds scale-forming ions and keeps them in suspension. It's a common threshold inhibitor in boiler water treatment. Salts like sodium chloride cause scale rather than prevent it.
What device measures flue gas oxygen and CO in real time?
Combustion analyzer
Level switch
Sulfur analyzer
Water quality meter
Combustion analyzers sample flue gas to detect O?, CO, and other gases, enabling combustion tuning. Sulfur analyzers measure SO? only. Real-time data ensures optimal burner settings.
How often is boiler internal inspection required by ASME for high-pressure units?
Every 5 years
Every 2 years
Annually
Every 10 years
ASME Section I mandates a full internal inspection at least every five inspections or not exceeding five years. External inspections are more frequent. Adherence ensures safety and compliance.
What boiler mount prevents water hammer by isolating condensate from steam lines?
Steam trap
Feedwater regulator
Pressure reducing valve
Safety valve
Steam traps discharge condensate while retaining steam, preventing water hammer. Safety valves relieve pressure only. Correct trap selection is crucial for steam system health.
In blowdown control, what does intermittent blowdown remove?
Bottom sludge
Oxygen
Scale inhibitors
Dissolved solids
Intermittent (bottom) blowdown clears settled mud and sludge from the boiler mud drum. Continuous blowdown removes dissolved solids. It does not remove gases.
Which burner control ensures ignition and monitors flame?
Pressure controller
Flame safeguard controller
Temperature limiter
Flow interlock
Flame safeguard controllers manage startup, verify flame presence via sensors, and shut down on failure. They are required by NFPA. Other controls regulate process variables.
Why is conductivity monitoring important in boiler water?
Detects pH only
Measures temperature
Determines oxygen level
Tracks dissolved ion concentration
Conductivity correlates with total dissolved ions; rising conductivity signals need for blowdown. It does not measure temperature or pH directly. Maintaining low conductivity prevents scale.
How does a soot blower improve boiler performance?
Balances draft
Increases feedwater flow
Removes soot deposits
Deaerates feedwater
Soot blowers use steam or air to clean heat transfer surfaces, restoring thermal efficiency. They do not affect feedwater or deaeration. Regular cleaning maintains output and lowers fuel use.
What is typical blowdown rate percentage for high-pressure boilers?
0.1% of feedwater
25% of feedwater
5 - 10% of feedwater
50% of feedwater
A 5 - 10% blowdown maintains TDS within limits. Too little allows scaling; too much wastes water and heat. Exact rates depend on feedwater quality.
What test is used to detect localized corrosion on boiler tubes?
pH meter
Electric holiday detector
Thermocouple
Ultrasonic thickness gauge
Holiday detectors find pinholes or coating defects in insulation that expose tubes to corrosion. Ultrasonic gauges measure thickness but don't locate holes. Early detection prevents leaks.
Why must feedwater temperature be controlled before steam drum entry?
Prevent thermal shock
Increase steam quality
Balance pressure
Reduce feedwater hardness
Cold feedwater can thermally shock the drum and tubes, causing stress cracks. Preheating via economizer or deaerator avoids damage. It also improves cycle efficiency.
What is the main cause of priming and carryover in boilers?
Low feedwater temperature
Excess blowdown
High water steam velocity
Insufficient draft
High steam velocity can entrain water droplets into the steam line, causing priming. Proper level control and steam separators reduce carryover. Temperature and draft are less direct factors.
Which control strategy uses feedwater flow measurement to correct level before it changes?
Feedback control
Feed-forward control
Bang-bang control
Proportional control
Feed-forward control anticipates load changes by measuring feedwater flow and adjusting the valve proactively. Feedback reacts after level change. It improves response in boilers.
In a boiler heat balance, latent heat constitutes approximately what fraction of total heat input?
95 - 100%
80 - 85%
10 - 15%
50 - 55%
Most heat input goes into the phase change (latent heat), typically about 80 - 85%. Sensible heat and losses make up the rest. This ratio is key in boiler sizing.
What failure mechanism is indicated by thinning and pitting on boiler tube interiors?
Corrosion
Creep
Fatigue
Erosion
Corrosion from oxygen or acidic condensate causes pitting and thinning inside tubes. Erosion is usually caused by high-velocity particles. Creep and fatigue show different crack patterns.
What is the primary purpose of a steam drum internals cyclonic separator?
Remove water droplets from steam
Support tubes
Vent air
Heat feedwater
Cyclonic separators use centrifugal force to throw water droplets outward, improving steam dryness. They are critical in high-pressure boilers. Other internals have different roles.
How does thickness variation from creep manifest in high-temperature superheater tubes?
Crystalline embrittlement with no shape change
Localized bulging and cross-sectional reduction
Surface pitting
Uniform thinning
Creep causes sections of tubing under high stress and temperature to elongate and reduce cross-sectional area, forming bulges. Uniform thinning is more characteristic of corrosion.
What is the role of a deaerator tray in feedwater treatment?
Increase contact time for gas removal
Filter solids
Cool feedwater
Add scale inhibitor
Deaerator trays break up feedwater into thin films, maximizing steam contact and releasing dissolved gases. They don't filter solids or add chemicals. Proper tray design is essential for corrosion control.
Which NDE method is best for detecting internal defects in boiler tubes?
Visual only
Ultrasonic testing
Magnetic particle
Radiography
Ultrasonic testing can measure wall thickness and detect internal flaws precisely. Radiography requires access both sides. Magnetic particle detects surface cracks only.
Why is a feedwater heater used in a high-pressure boiler cycle?
Separate steam and water
Recover bleed steam to preheat feedwater
Desuperheat steam
Cool down condensate
Feedwater heaters use extracted steam to preheat feedwater, improving cycle efficiency. This reduces fuel consumption. Cooling condensate is done by condensers, not heaters.
What causes thermal fatigue in boiler headers?
Steady high temperature
High-pressure spikes only
Vibration only
Cyclic temperature fluctuations
Repeated heating and cooling cycles induce stress variations at stress concentrators, leading to fatigue cracks. Constant high temperature causes creep, not fatigue.
How is boiler horsepower (BHP) defined?
34.5 lb of steam/hr at 0 psig and 212°F
1,000,000 BTU/hr
1000 kg steam/hr at 10 bar
10,000 kcal/hr
One boiler horsepower is defined as producing 34.5 lbs of steam per hour at 0 psig and 212°F. It's a traditional unit. The million BTU/hr is a plant term but not BHP.
What parameter must be controlled to prevent caustic embrittlement?
pH of boiler water
Feedwater temperature
Steam purity
Conductivity alone
Maintaining pH within the recommended alkaline range prevents caustic concentration at crevices and subsequent embrittlement. Steam purity and conductivity are important but pH is critical.
Which ASME code section covers power boiler construction?
Section V
Section VIII
Section IX
Section I
ASME Section I provides rules for the design, materials, fabrication, and inspection of power boilers. Section VIII covers pressure vessels. Section V covers NDE.
What is the effect of flue gas recirculation in combustion?
Reduces NOx formation
Eliminates soot
Increases O? concentration
Increases stack temperature
Recirculating flue gas lowers flame temperature and oxygen concentration locally, reducing thermal NOx formation. It can slightly lower stack temperature.
Why is drum steam space height important?
Reduces metal fatigue
Prevents carryover by allowing separation
Improves feedwater preheating
Increases steam pressure
Adequate steam space allows droplets to fall back into water, reducing carryover. Too little space leads to priming. It doesn't directly affect fatigue or pressure.
What method is best for controlling TDS in boiler water when feedwater varies frequently?
Timed intermittent blowdown
Deaerator bleed control
Continuous blowdown with conductivity probe
Manual blowdown only
Continuous blowdown tied to a conductivity probe maintains constant TDS despite feedwater variability. Timed blowdown can under- or over-blow. Automatic control prevents scale effectively.
Which advanced control strategy minimizes drum level upset during rapid load changes?
On-off control
PI control only
Model predictive control (MPC)
Manual tuning
MPC uses a dynamic model to predict and counteract level disturbances before they occur, offering superior performance over standard PID. On-off is too coarse.
How does hydrazine treatment protect high-pressure boilers?
Removes dissolved oxygen and forms protective oxide
Increases pH only
Reduces hardness
Acts as a scale dispersant
Hydrazine scavenges oxygen and promotes a magnetite film on steel surfaces, reducing corrosion. It does not alter hardness or disperse scale.
Which phenomenon causes tube rupture at superheater outlet during low-load operation?
Excessive soot deposition
High feedwater temperature
Low flue gas velocity
Moisture carryover leading to rapid steam flashing
At low loads, wet steam carryover can flash violently in superheater tubes, overpressuring them. Proper separation and minimum loads are required.
What is the primary consideration when selecting tube material for supercritical boilers?
Creep strength at high temperatures
Corrosion resistance at ambient
Availability of seamless tubes
Ease of welding
Supercritical boilers operate above critical temperature requiring materials with high creep strength to withstand sustained stress. Corrosion and weldability matter but creep strength is paramount.
In two-element feedwater control, what two signals are used?
Drum level and steam flow
Steam pressure and feedwater flow
Drum level and feedwater temperature
Feedwater conductivity and level
Two-element control uses drum level and steam flow to correct for load changes, improving response over single-element. It does not use temperature or conductivity.
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Study Outcomes

  1. Understand key topics in the boiler exam test -

    Gain clarity on core high-pressure boiler concepts - safety, operation, and maintenance - to prepare effectively for your boiler exam test.

  2. Analyze boiler test questions and answers -

    Learn to dissect realistic quiz questions, identify key clues, and apply logical reasoning to select accurate answers in both practice quizzes and the official boiler license test.

  3. Apply routine maintenance and troubleshooting procedures -

    Master step-by-step methods for inspecting, maintaining, and troubleshooting common issues in high-pressure boilers to ensure peak performance and safety compliance.

  4. Evaluate safety protocols and hazard prevention -

    Critically assess boiler room safety measures, identify potential risks, and implement best practices to prevent accidents and meet regulatory standards.

  5. Interpret boiler performance metrics -

    Understand how to read and evaluate pressure, temperature, and efficiency data to diagnose boiler health and optimize operational efficiency.

  6. Prepare strategically for your boiler license test -

    Develop personalized study plans and test-taking strategies based on quiz performance insights to boost confidence and exam readiness.

Cheat Sheet

  1. High-Pressure Boiler Components -

    Review the core parts of a high-pressure boiler - furnace, steam drum, water drum, and superheater - as defined by ASME Boiler & Pressure Vessel Code. Knowing each component's function helps you troubleshoot and understand heat flow paths. Try the mnemonic "FSSW" (Furnace, Steam drum, Superheater, Water drum) to lock in the sequence.

  2. Combustion Efficiency Calculation -

    Understand the formula η = (Q usable ÷ Q input) × 100% to evaluate how effectively the boiler converts fuel energy into steam (University of Illinois Fire Protection Engineering). For example, if 85,000 kJ of steam energy is produced from 100,000 kJ of fuel, η = 85%. Regular stack-gas analysis keeps efficiency above 80% in licensed boiler operations.

  3. Steam Property Tables -

    Master using steam tables to find enthalpy (h), entropy (s), and saturation pressure (P). Remember the "Two-Column Trick": column 1 for saturated liquid (hf), column 2 for saturated vapor (hg). Accurate table lookups are critical for thermodynamic cycle calculations on your boiler license test.

  4. Safety Valve Settings & Blowdown -

    Study the ASME requirement that safety valves lift at 103% of the maximum allowable working pressure (MAWP). The blowdown (BD) percentage is set by BD% = (Pop - PR)/Pop × 100; many plants use 7 - 10% for reliable reseating. Use "Pop-PR" (pop goes the pressure minus PR) as a recall phrase.

  5. Water Treatment & Scale Control -

    Memorize the "5C" water-treatment checklist: Coagulation, Clarification, Carbonate removal, Conditioning, and Control of cycles of concentration (Babcock & Wilcox tutorials). Proper softening prevents scale and maintains heat transfer. Aim for cycles of concentration below 5 to minimize boiler blowdown and extend tube life.

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