Stationary Engineer First Class Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1.A First Class Stationary Engineer is responsible for operating a high-
pressure boiler plant. Which of the following actions is most important
before placing a newly repaired boiler back into service?
A. Increasing the firing rate immediately to test maximum capacity
B. Ensuring all safety devices, controls, valves, and inspections are properly
completed
C. Operating the boiler without water to check for leaks
D. Closing all steam outlets to increase pressure rapidly
Correct Answer: B
A repaired boiler must not return to service until safety inspections,
pressure tests, control checks, and proper functioning of protective devices
have been verified to prevent catastrophic failure.
2. The primary function of a boiler safety valve is to:
A. Regulate feedwater temperature
B. Prevent excessive steam pressure buildup
C. Increase combustion efficiency
D. Control fuel atomization
Correct Answer: B
,Safety valves are critical pressure-relief devices designed to automatically
discharge steam when boiler pressure exceeds the approved operating
limit.
3. In a water-tube boiler, water circulates through:
A. Large furnace tubes only
B. Tubes surrounded by combustion gases
C. The combustion chamber only
D. The steam drum exclusively
Correct Answer: B
Water-tube boilers pass water through tubes that are heated externally by
combustion gases, allowing efficient production of high-pressure steam.
4. The purpose of a boiler low-water cutoff device is to:
A. Increase boiler pressure
B. Prevent burner operation when water level is dangerously low
C. Reduce steam temperature
D. Increase fuel flow
Correct Answer: B
A low-water cutoff protects the boiler from overheating by shutting down
the burner when the water level falls below a safe operating point.
5. The main purpose of a boiler blowdown operation is to:
A. Add chemicals to the boiler
B. Remove dissolved solids and accumulated impurities
C. Increase steam pressure
D. Reduce combustion air
Correct Answer: B
,Blowdown removes concentrated minerals and contaminants from boiler
water, helping prevent scale formation, corrosion, and poor heat transfer.
6. The function of an economizer in a boiler system is to:
A. Cool exhaust gases before combustion
B. Heat feedwater using waste heat from flue gases
C. Increase steam pressure directly
D. Remove oxygen from fuel
Correct Answer: B
An economizer improves efficiency by transferring heat from outgoing flue
gases to incoming boiler feedwater, reducing fuel consumption.
7. A boiler water level that fluctuates rapidly may indicate:
A. Perfect combustion
B. Improper operation or foaming in the boiler
C. Excessive fuel efficiency
D. Correct feedwater control
Correct Answer: B
Rapid water-level fluctuations may result from foaming, improper
circulation, sudden load changes, or poor water treatment conditions.
8. The main purpose of a deaerator in a steam plant is to:
A. Remove dissolved gases from feedwater
B. Increase boiler pressure
C. Reduce steam temperature
D. Increase fuel viscosity
Correct Answer: A
A deaerator removes oxygen and carbon dioxide from feedwater, reducing
corrosion in boilers and piping systems.
, 9. Boiler scale is dangerous because it:
A. Improves heat transfer
B. Reduces heat transfer efficiency and may cause overheating
C. Increases water circulation
D. Lowers operating costs
Correct Answer: B
Scale acts as an insulating layer on heating surfaces, causing metal
temperatures to rise and increasing the risk of tube failure.
10. The primary purpose of a steam separator is to:
A. Remove moisture from steam
B. Increase combustion rate
C. Reduce boiler water level
D. Increase feedwater pressure
Correct Answer: A
Steam separators remove entrained water droplets from steam, improving
steam quality and protecting downstream equipment.
11. The correct fuel-to-air ratio in combustion is important because
it:
A. Eliminates the need for maintenance
B. Ensures efficient combustion with minimal emissions
C. Prevents steam production
D. Increases water hardness
Correct Answer: B
Proper combustion requires balanced fuel and air quantities to maximize
efficiency while minimizing incomplete combustion and pollutants.
12. Carbon monoxide in boiler exhaust gases usually indicates:
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1.A First Class Stationary Engineer is responsible for operating a high-
pressure boiler plant. Which of the following actions is most important
before placing a newly repaired boiler back into service?
A. Increasing the firing rate immediately to test maximum capacity
B. Ensuring all safety devices, controls, valves, and inspections are properly
completed
C. Operating the boiler without water to check for leaks
D. Closing all steam outlets to increase pressure rapidly
Correct Answer: B
A repaired boiler must not return to service until safety inspections,
pressure tests, control checks, and proper functioning of protective devices
have been verified to prevent catastrophic failure.
2. The primary function of a boiler safety valve is to:
A. Regulate feedwater temperature
B. Prevent excessive steam pressure buildup
C. Increase combustion efficiency
D. Control fuel atomization
Correct Answer: B
,Safety valves are critical pressure-relief devices designed to automatically
discharge steam when boiler pressure exceeds the approved operating
limit.
3. In a water-tube boiler, water circulates through:
A. Large furnace tubes only
B. Tubes surrounded by combustion gases
C. The combustion chamber only
D. The steam drum exclusively
Correct Answer: B
Water-tube boilers pass water through tubes that are heated externally by
combustion gases, allowing efficient production of high-pressure steam.
4. The purpose of a boiler low-water cutoff device is to:
A. Increase boiler pressure
B. Prevent burner operation when water level is dangerously low
C. Reduce steam temperature
D. Increase fuel flow
Correct Answer: B
A low-water cutoff protects the boiler from overheating by shutting down
the burner when the water level falls below a safe operating point.
5. The main purpose of a boiler blowdown operation is to:
A. Add chemicals to the boiler
B. Remove dissolved solids and accumulated impurities
C. Increase steam pressure
D. Reduce combustion air
Correct Answer: B
,Blowdown removes concentrated minerals and contaminants from boiler
water, helping prevent scale formation, corrosion, and poor heat transfer.
6. The function of an economizer in a boiler system is to:
A. Cool exhaust gases before combustion
B. Heat feedwater using waste heat from flue gases
C. Increase steam pressure directly
D. Remove oxygen from fuel
Correct Answer: B
An economizer improves efficiency by transferring heat from outgoing flue
gases to incoming boiler feedwater, reducing fuel consumption.
7. A boiler water level that fluctuates rapidly may indicate:
A. Perfect combustion
B. Improper operation or foaming in the boiler
C. Excessive fuel efficiency
D. Correct feedwater control
Correct Answer: B
Rapid water-level fluctuations may result from foaming, improper
circulation, sudden load changes, or poor water treatment conditions.
8. The main purpose of a deaerator in a steam plant is to:
A. Remove dissolved gases from feedwater
B. Increase boiler pressure
C. Reduce steam temperature
D. Increase fuel viscosity
Correct Answer: A
A deaerator removes oxygen and carbon dioxide from feedwater, reducing
corrosion in boilers and piping systems.
, 9. Boiler scale is dangerous because it:
A. Improves heat transfer
B. Reduces heat transfer efficiency and may cause overheating
C. Increases water circulation
D. Lowers operating costs
Correct Answer: B
Scale acts as an insulating layer on heating surfaces, causing metal
temperatures to rise and increasing the risk of tube failure.
10. The primary purpose of a steam separator is to:
A. Remove moisture from steam
B. Increase combustion rate
C. Reduce boiler water level
D. Increase feedwater pressure
Correct Answer: A
Steam separators remove entrained water droplets from steam, improving
steam quality and protecting downstream equipment.
11. The correct fuel-to-air ratio in combustion is important because
it:
A. Eliminates the need for maintenance
B. Ensures efficient combustion with minimal emissions
C. Prevents steam production
D. Increases water hardness
Correct Answer: B
Proper combustion requires balanced fuel and air quantities to maximize
efficiency while minimizing incomplete combustion and pollutants.
12. Carbon monoxide in boiler exhaust gases usually indicates:
