3rd Class Power Engineer A2 Exam Questions
and Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. The primary purpose of a deaerator in a boiler feedwater system
is to:
A. Increase feedwater pressure
B. Remove dissolved oxygen and carbon dioxide
C. Reduce feedwater temperature
D. Increase boiler steam pressure
Correct Answer: B. Remove dissolved oxygen and carbon dioxide
Rationale: A deaerator removes dissolved oxygen and carbon dioxide
from boiler feedwater. These gases promote corrosion in boilers,
piping, and condensate systems. Mechanical scrubbing combined with
heating near saturation temperature significantly reduces oxygen
levels, extending equipment life and improving system reliability.
2. Boiler scale primarily reduces:
A. Steam quality
,B. Boiler efficiency
C. Fuel heating value
D. Condensate return
Correct Answer: B. Boiler efficiency
Rationale: Scale acts as an insulating layer between hot combustion
gases and boiler water. This reduces heat transfer efficiency, increases
fuel consumption, raises tube metal temperatures, and may
eventually lead to overheating and tube failure.
3. The pressure relief valve on a boiler is designed to:
A. Control steam pressure during normal operation
B. Prevent excessive pressure buildup
C. Regulate feedwater flow
D. Increase boiler efficiency
Correct Answer: B. Prevent excessive pressure buildup
Rationale: Safety relief valves automatically open when boiler
pressure reaches the set pressure, preventing dangerous overpressure
conditions that could result in catastrophic equipment failure.
4. A feedwater economizer improves boiler efficiency by:
,A. Cooling stack gases
B. Heating combustion air
C. Preheating feedwater using waste heat
D. Increasing steam pressure
Correct Answer: C. Preheating feedwater using waste heat
Rationale: An economizer captures heat from flue gases to raise
feedwater temperature before it enters the boiler. This reduces the
fuel required to produce steam and improves overall thermal
efficiency.
5. The purpose of boiler blowdown is to:
A. Increase boiler pressure
B. Remove accumulated impurities
C. Raise water level
D. Increase steam production
Correct Answer: B. Remove accumulated impurities
Rationale: Blowdown removes concentrated dissolved solids and
sludge that accumulate during boiler operation. Proper blowdown
prevents scale formation, foaming, and carryover while maintaining
acceptable water chemistry.
, 6. Steam traps are primarily installed to:
A. Remove condensate while retaining steam
B. Increase steam pressure
C. Reduce condensate temperature
D. Purify steam
Correct Answer: A. Remove condensate while retaining steam
Rationale: Steam traps automatically discharge condensate and non-
condensable gases while preventing the loss of valuable live steam,
maintaining efficient heat transfer and system performance.
7. The lowest visible water level in a gauge glass should:
A. Be ignored
B. Always remain above the minimum safe operating level
C. Touch the bottom of the glass
D. Equal steam pressure
Correct Answer: B. Always remain above the minimum safe operating
level
and Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. The primary purpose of a deaerator in a boiler feedwater system
is to:
A. Increase feedwater pressure
B. Remove dissolved oxygen and carbon dioxide
C. Reduce feedwater temperature
D. Increase boiler steam pressure
Correct Answer: B. Remove dissolved oxygen and carbon dioxide
Rationale: A deaerator removes dissolved oxygen and carbon dioxide
from boiler feedwater. These gases promote corrosion in boilers,
piping, and condensate systems. Mechanical scrubbing combined with
heating near saturation temperature significantly reduces oxygen
levels, extending equipment life and improving system reliability.
2. Boiler scale primarily reduces:
A. Steam quality
,B. Boiler efficiency
C. Fuel heating value
D. Condensate return
Correct Answer: B. Boiler efficiency
Rationale: Scale acts as an insulating layer between hot combustion
gases and boiler water. This reduces heat transfer efficiency, increases
fuel consumption, raises tube metal temperatures, and may
eventually lead to overheating and tube failure.
3. The pressure relief valve on a boiler is designed to:
A. Control steam pressure during normal operation
B. Prevent excessive pressure buildup
C. Regulate feedwater flow
D. Increase boiler efficiency
Correct Answer: B. Prevent excessive pressure buildup
Rationale: Safety relief valves automatically open when boiler
pressure reaches the set pressure, preventing dangerous overpressure
conditions that could result in catastrophic equipment failure.
4. A feedwater economizer improves boiler efficiency by:
,A. Cooling stack gases
B. Heating combustion air
C. Preheating feedwater using waste heat
D. Increasing steam pressure
Correct Answer: C. Preheating feedwater using waste heat
Rationale: An economizer captures heat from flue gases to raise
feedwater temperature before it enters the boiler. This reduces the
fuel required to produce steam and improves overall thermal
efficiency.
5. The purpose of boiler blowdown is to:
A. Increase boiler pressure
B. Remove accumulated impurities
C. Raise water level
D. Increase steam production
Correct Answer: B. Remove accumulated impurities
Rationale: Blowdown removes concentrated dissolved solids and
sludge that accumulate during boiler operation. Proper blowdown
prevents scale formation, foaming, and carryover while maintaining
acceptable water chemistry.
, 6. Steam traps are primarily installed to:
A. Remove condensate while retaining steam
B. Increase steam pressure
C. Reduce condensate temperature
D. Purify steam
Correct Answer: A. Remove condensate while retaining steam
Rationale: Steam traps automatically discharge condensate and non-
condensable gases while preventing the loss of valuable live steam,
maintaining efficient heat transfer and system performance.
7. The lowest visible water level in a gauge glass should:
A. Be ignored
B. Always remain above the minimum safe operating level
C. Touch the bottom of the glass
D. Equal steam pressure
Correct Answer: B. Always remain above the minimum safe operating
level
