Boiler Operator Licensing Exam
question And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A
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1. What is the primary purpose of a boiler?
A. Cooling water
B. Generating electricity
C. Producing steam or hot water
D. Compressing air
Rationale: Boilers convert water into steam or hot water for heating and
power.
2. The main fuel used in most industrial boilers is:
A. Sand
B. Natural gas
C. Water
D. Carbon
Rationale: Natural gas is commonly used due to efficiency and cleanliness.
3. What device prevents excessive pressure buildup in a boiler?
A. Thermostat
B. Feedwater pump
C. Safety valve
D. Economizer
Rationale: Safety valves release excess pressure to prevent explosion.
4. Normal boiler water level should be:
A. Completely empty
, B. At the very top of the gauge glass
C. At the middle of the gauge glass
D. Below the gauge glass
Rationale: Mid-level ensures safe steam separation and prevents damage.
5. A low-water cutoff device is designed to:
A. Increase boiler pressure
B. Shut down the burner if water level is too low
C. Add chemicals
D. Clean the boiler
Rationale: It prevents dangerous dry-firing conditions.
6. What type of valve controls the flow of feedwater into the boiler?
A. Blowdown valve
B. Feedwater valve
C. Safety valve
D. Steam trap
Rationale: Feedwater valves regulate water entering the boiler.
7. Boiler blowdown is performed to:
A. Increase pressure
B. Reduce steam output
C. Remove sludge and dissolved solids
D. Cool the boiler
Rationale: Blowdown controls total dissolved solids and prevents scaling.
8. The device that removes air and non-condensable gases from feedwater is
called a:
A. Condenser
B. Steam trap
C. Deaerator
D. Superheater
Rationale: Deaerators prevent corrosion by eliminating oxygen and gases.
, 9. A fire-tube boiler is characterized by:
A. Water flowing inside tubes
B. Hot gases flowing through tubes
C. No tubes
D. Electric heating only
Rationale: Flue gases pass through tubes surrounded by water.
10.A water-tube boiler differs by having:
A. No water in it
B. Water flowing inside tubes
C. Steam inside fire tubes
D. No pressure
Rationale: Water circulates inside tubes while heat surrounds them.
11.What instrument shows boiler pressure?
A. Thermometer
B. Sight glass
C. Pressure gauge
D. Manometer
Rationale: Pressure gauges indicate internal boiler pressure.
12.What fuel burns the cleanest?
A. Coal
B. Diesel
C. Natural gas
D. Wood
Rationale: Natural gas produces fewer particulates and residues.
13.The purpose of an economizer is to:
A. Cool flue gases
B. Preheat feedwater using waste heat
C. Store water
D. Increase steam dryness
Rationale: Economizers improve efficiency by recycling heat.
question And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A
Instant Download Pdf
1. What is the primary purpose of a boiler?
A. Cooling water
B. Generating electricity
C. Producing steam or hot water
D. Compressing air
Rationale: Boilers convert water into steam or hot water for heating and
power.
2. The main fuel used in most industrial boilers is:
A. Sand
B. Natural gas
C. Water
D. Carbon
Rationale: Natural gas is commonly used due to efficiency and cleanliness.
3. What device prevents excessive pressure buildup in a boiler?
A. Thermostat
B. Feedwater pump
C. Safety valve
D. Economizer
Rationale: Safety valves release excess pressure to prevent explosion.
4. Normal boiler water level should be:
A. Completely empty
, B. At the very top of the gauge glass
C. At the middle of the gauge glass
D. Below the gauge glass
Rationale: Mid-level ensures safe steam separation and prevents damage.
5. A low-water cutoff device is designed to:
A. Increase boiler pressure
B. Shut down the burner if water level is too low
C. Add chemicals
D. Clean the boiler
Rationale: It prevents dangerous dry-firing conditions.
6. What type of valve controls the flow of feedwater into the boiler?
A. Blowdown valve
B. Feedwater valve
C. Safety valve
D. Steam trap
Rationale: Feedwater valves regulate water entering the boiler.
7. Boiler blowdown is performed to:
A. Increase pressure
B. Reduce steam output
C. Remove sludge and dissolved solids
D. Cool the boiler
Rationale: Blowdown controls total dissolved solids and prevents scaling.
8. The device that removes air and non-condensable gases from feedwater is
called a:
A. Condenser
B. Steam trap
C. Deaerator
D. Superheater
Rationale: Deaerators prevent corrosion by eliminating oxygen and gases.
, 9. A fire-tube boiler is characterized by:
A. Water flowing inside tubes
B. Hot gases flowing through tubes
C. No tubes
D. Electric heating only
Rationale: Flue gases pass through tubes surrounded by water.
10.A water-tube boiler differs by having:
A. No water in it
B. Water flowing inside tubes
C. Steam inside fire tubes
D. No pressure
Rationale: Water circulates inside tubes while heat surrounds them.
11.What instrument shows boiler pressure?
A. Thermometer
B. Sight glass
C. Pressure gauge
D. Manometer
Rationale: Pressure gauges indicate internal boiler pressure.
12.What fuel burns the cleanest?
A. Coal
B. Diesel
C. Natural gas
D. Wood
Rationale: Natural gas produces fewer particulates and residues.
13.The purpose of an economizer is to:
A. Cool flue gases
B. Preheat feedwater using waste heat
C. Store water
D. Increase steam dryness
Rationale: Economizers improve efficiency by recycling heat.
