2nd Class Power Engineer A1 Exam Questions
and Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. In a water-tube boiler, the primary advantage over a fire-tube
boiler is:
A. Lower operating pressure
B. Lower steam capacity
C. Higher pressure and higher steam generation capability
D. Simpler construction
Rationale: Water-tube boilers circulate water through tubes while hot
gases flow around them. This design permits operation at much
higher pressures and steam generation rates than fire-tube boilers,
making them suitable for large industrial plants and power
generation.
2. The critical pressure of water is approximately:
A. 10 MPa
B. 16 MPa
, C. 22.1 MPa
D. 30 MPa
Rationale: The critical pressure of water is about 22.1 MPa (3,206 psi).
Above this pressure, there is no distinct liquid or vapor phase,
allowing once-through supercritical boilers to operate without boiling
in the conventional sense.
3. A safety valve on a boiler is primarily intended to:
A. Control steam flow
B. Prevent excessive pressure
C. Measure pressure
D. Reduce feedwater temperature
Rationale: Safety valves automatically relieve excess pressure when
the maximum allowable working pressure is exceeded. They are the
most important pressure-protective device on a boiler and prevent
catastrophic failure.
4. Boiler feedwater should be deaerated primarily to remove:
A. Calcium
B. Magnesium
, C. Oxygen and carbon dioxide
D. Chlorides
Rationale: Dissolved oxygen and carbon dioxide cause severe
corrosion in boilers and condensate systems. Deaerators remove these
gases by heating water close to saturation temperature and venting
the released gases.
5. The purpose of a superheater is to:
A. Increase boiler pressure
B. Remove impurities
C. Raise steam temperature above saturation
D. Reduce steam flow
Rationale: A superheater increases steam temperature beyond its
saturation point without increasing pressure. Superheated steam
improves turbine efficiency and prevents moisture damage to turbine
blades.
6. The instrument used to indicate boiler water level is the:
A. Thermometer
B. Pressure gauge
, C. Gauge glass
D. Flowmeter
Rationale: The gauge glass provides a direct visual indication of boiler
water level. Maintaining proper water level is critical to prevent
overheating of boiler tubes or water carryover.
7. Boiler blowdown is performed primarily to:
A. Increase steam pressure
B. Control dissolved and suspended solids
C. Raise feedwater temperature
D. Improve combustion
Rationale: Blowdown removes concentrated impurities from the boiler
water, maintaining acceptable total dissolved solids and reducing
scaling, foaming, and corrosion.
8. Economizers improve boiler efficiency by:
A. Cooling flue gases
B. Cooling feedwater
C. Recovering heat from flue gases to preheat feedwater
D. Increasing furnace pressure
and Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. In a water-tube boiler, the primary advantage over a fire-tube
boiler is:
A. Lower operating pressure
B. Lower steam capacity
C. Higher pressure and higher steam generation capability
D. Simpler construction
Rationale: Water-tube boilers circulate water through tubes while hot
gases flow around them. This design permits operation at much
higher pressures and steam generation rates than fire-tube boilers,
making them suitable for large industrial plants and power
generation.
2. The critical pressure of water is approximately:
A. 10 MPa
B. 16 MPa
, C. 22.1 MPa
D. 30 MPa
Rationale: The critical pressure of water is about 22.1 MPa (3,206 psi).
Above this pressure, there is no distinct liquid or vapor phase,
allowing once-through supercritical boilers to operate without boiling
in the conventional sense.
3. A safety valve on a boiler is primarily intended to:
A. Control steam flow
B. Prevent excessive pressure
C. Measure pressure
D. Reduce feedwater temperature
Rationale: Safety valves automatically relieve excess pressure when
the maximum allowable working pressure is exceeded. They are the
most important pressure-protective device on a boiler and prevent
catastrophic failure.
4. Boiler feedwater should be deaerated primarily to remove:
A. Calcium
B. Magnesium
, C. Oxygen and carbon dioxide
D. Chlorides
Rationale: Dissolved oxygen and carbon dioxide cause severe
corrosion in boilers and condensate systems. Deaerators remove these
gases by heating water close to saturation temperature and venting
the released gases.
5. The purpose of a superheater is to:
A. Increase boiler pressure
B. Remove impurities
C. Raise steam temperature above saturation
D. Reduce steam flow
Rationale: A superheater increases steam temperature beyond its
saturation point without increasing pressure. Superheated steam
improves turbine efficiency and prevents moisture damage to turbine
blades.
6. The instrument used to indicate boiler water level is the:
A. Thermometer
B. Pressure gauge
, C. Gauge glass
D. Flowmeter
Rationale: The gauge glass provides a direct visual indication of boiler
water level. Maintaining proper water level is critical to prevent
overheating of boiler tubes or water carryover.
7. Boiler blowdown is performed primarily to:
A. Increase steam pressure
B. Control dissolved and suspended solids
C. Raise feedwater temperature
D. Improve combustion
Rationale: Blowdown removes concentrated impurities from the boiler
water, maintaining acceptable total dissolved solids and reducing
scaling, foaming, and corrosion.
8. Economizers improve boiler efficiency by:
A. Cooling flue gases
B. Cooling feedwater
C. Recovering heat from flue gases to preheat feedwater
D. Increasing furnace pressure
