2nd Class Power Engineer A3 Exam Questions
and Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. In a water-tube boiler, the primary purpose of the steam drum is
to:
A. Increase furnace temperature
B. Separate steam from water
C. Reduce fuel consumption
D. Collect bottom sludge
Correct Answer: B. Separate steam from water
Rationale: The steam drum is the upper pressure vessel where the
steam-water mixture from the riser tubes is separated. Dry steam
exits the drum for use in the plant, while the separated water is
recirculated through the boiler. Efficient steam separation minimizes
moisture carryover and protects downstream equipment such as
superheaters and turbines.
, 2. Which factor has the greatest effect on natural circulation in a
water-tube boiler?
A. Fuel type
B. Difference in density between hot and cold water
C. Feedwater pH
D. Stack height
Correct Answer: B. Difference in density between hot and cold water
Rationale: Natural circulation depends on the density difference
between the heated water-steam mixture in the risers and the cooler
water in the downcomers. This density difference creates the driving
force that circulates water without pumps.
3. Boiler blowdown is primarily performed to:
A. Increase steam pressure
B. Remove dissolved and suspended solids
C. Increase combustion efficiency
D. Improve burner ignition
Correct Answer: B. Remove dissolved and suspended solids
Rationale: Blowdown controls the concentration of impurities within
the boiler. Without regular blowdown, dissolved solids become
,concentrated, leading to scale formation, foaming, carryover, and
corrosion, all of which reduce boiler efficiency and reliability.
4. Excessive boiler scale results in:
A. Improved heat transfer
B. Reduced fuel consumption
C. Poor heat transfer and possible tube overheating
D. Lower stack temperatures
Correct Answer: C. Poor heat transfer and possible tube overheating
Rationale: Scale acts as an insulating layer that reduces heat transfer
from combustion gases to boiler water. As a result, tube metal
temperatures increase, potentially causing overheating, loss of
strength, and tube failure.
5. The economizer is installed to:
A. Increase furnace volume
B. Heat feedwater using flue gases
C. Cool combustion gases before combustion
D. Reduce steam pressure
Correct Answer: B. Heat feedwater using flue gases
, Rationale: An economizer recovers waste heat from flue gases to
preheat boiler feedwater before it enters the boiler. This improves
boiler efficiency, reduces fuel consumption, and lowers stack gas
temperatures.
6. The purpose of a superheater is to:
A. Remove dissolved oxygen
B. Increase steam moisture
C. Raise steam temperature above saturation
D. Increase feedwater pressure
Correct Answer: C. Raise steam temperature above saturation
Rationale: A superheater increases the temperature of saturated
steam without increasing its pressure. Superheated steam contains
more energy, reduces condensation in turbines, and improves overall
thermal efficiency.
7. Which boiler component removes heat from flue gases to warm
combustion air?
A. Steam drum
B. Economizer
and Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. In a water-tube boiler, the primary purpose of the steam drum is
to:
A. Increase furnace temperature
B. Separate steam from water
C. Reduce fuel consumption
D. Collect bottom sludge
Correct Answer: B. Separate steam from water
Rationale: The steam drum is the upper pressure vessel where the
steam-water mixture from the riser tubes is separated. Dry steam
exits the drum for use in the plant, while the separated water is
recirculated through the boiler. Efficient steam separation minimizes
moisture carryover and protects downstream equipment such as
superheaters and turbines.
, 2. Which factor has the greatest effect on natural circulation in a
water-tube boiler?
A. Fuel type
B. Difference in density between hot and cold water
C. Feedwater pH
D. Stack height
Correct Answer: B. Difference in density between hot and cold water
Rationale: Natural circulation depends on the density difference
between the heated water-steam mixture in the risers and the cooler
water in the downcomers. This density difference creates the driving
force that circulates water without pumps.
3. Boiler blowdown is primarily performed to:
A. Increase steam pressure
B. Remove dissolved and suspended solids
C. Increase combustion efficiency
D. Improve burner ignition
Correct Answer: B. Remove dissolved and suspended solids
Rationale: Blowdown controls the concentration of impurities within
the boiler. Without regular blowdown, dissolved solids become
,concentrated, leading to scale formation, foaming, carryover, and
corrosion, all of which reduce boiler efficiency and reliability.
4. Excessive boiler scale results in:
A. Improved heat transfer
B. Reduced fuel consumption
C. Poor heat transfer and possible tube overheating
D. Lower stack temperatures
Correct Answer: C. Poor heat transfer and possible tube overheating
Rationale: Scale acts as an insulating layer that reduces heat transfer
from combustion gases to boiler water. As a result, tube metal
temperatures increase, potentially causing overheating, loss of
strength, and tube failure.
5. The economizer is installed to:
A. Increase furnace volume
B. Heat feedwater using flue gases
C. Cool combustion gases before combustion
D. Reduce steam pressure
Correct Answer: B. Heat feedwater using flue gases
, Rationale: An economizer recovers waste heat from flue gases to
preheat boiler feedwater before it enters the boiler. This improves
boiler efficiency, reduces fuel consumption, and lowers stack gas
temperatures.
6. The purpose of a superheater is to:
A. Remove dissolved oxygen
B. Increase steam moisture
C. Raise steam temperature above saturation
D. Increase feedwater pressure
Correct Answer: C. Raise steam temperature above saturation
Rationale: A superheater increases the temperature of saturated
steam without increasing its pressure. Superheated steam contains
more energy, reduces condensation in turbines, and improves overall
thermal efficiency.
7. Which boiler component removes heat from flue gases to warm
combustion air?
A. Steam drum
B. Economizer
