Stationary Engineer Third Class Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A stationary engineer is primarily responsible for the operation of
which of the following systems in a facility?
A) A) Boilers, HVAC, and associated mechanical power systems
B) B) Computer programming systems and network administration
C) C) Electrical circuit design for microprocessors
D) D) Automotive engine manufacturing processes
A stationary engineer is tasked with managing and maintaining
large-scale mechanical systems such as boilers, HVAC units, and
related utility equipment to ensure safe and efficient facility
operation.
2. What is the primary purpose of a boiler in an industrial plant?
A) A) To convert electrical energy into chemical energy
B) B) To compress air for pneumatic tools
, C) C) To generate steam or hot water for heating and power
applications
D) D) To cool refrigerant for air conditioning systems
A boiler is designed to produce steam or hot water by transferring
heat energy from fuel combustion or electrical input, which is then
used for heating or mechanical power generation.
3. Which safety device is designed to prevent excessive pressure buildup
in a boiler?
A) A) Water level gauge
B) B) Thermostat controller
C) C) Feedwater pump
D) D) Pressure relief valve
A pressure relief valve automatically releases excess pressure from a
boiler system to prevent rupture or catastrophic failure, ensuring safe
operation under varying load conditions.
4. What is the function of a steam trap in a steam system?
A) A) To increase steam pressure
B) B) To convert steam back into fuel
C) C) To measure steam flow rate
D) D) To remove condensate while preventing steam loss
A steam trap efficiently discharges condensate and non-condensable
gases from steam lines while retaining live steam, maintaining
system efficiency.
,5. Which thermodynamic process occurs when water changes into steam
at constant pressure?
A) A) Condensation
B) B) Superheating
C) C) Compression
D) D) Vaporization (boiling process)
Vaporization is the phase change where water absorbs latent heat at
constant pressure and converts into steam, a key principle in boiler
operation.
6. What is the purpose of a deaerator in a boiler system?
A) A) To increase water hardness
B) B) To cool down steam before use
C) C) To filter solid debris from fuel
D) D) To remove dissolved oxygen and gases from feedwater
A deaerator removes oxygen and other dissolved gases from
feedwater to reduce corrosion in boilers and steam systems.
7. Which instrument is commonly used to measure steam pressure?
A) A) Pyrometer
B) B) Tachometer
C) C) Hydrometer
D) D) Bourdon gauge
A Bourdon gauge is widely used in industrial settings to measure
, pressure in steam and fluid systems through mechanical deformation
of a curved tube.
8. What is the main function of a centrifugal pump in a boiler system?
A) A) To generate electrical current
B) B) To increase steam temperature
C) C) To separate oil from water
D) D) To circulate water through the system
Centrifugal pumps are used to move water through boiler and HVAC
systems by converting rotational energy into fluid flow energy.
9. What does BTU stand for in thermal engineering?
A) A) Boiler Thermal Utility
B) B) Basic Temperature Unit
C) C) Balanced Thermal Output
D) D) British Thermal Unit
A British Thermal Unit (BTU) is the amount of heat required to raise
the temperature of one pound of water by one degree Fahrenheit.
10. Which component controls the water level in a boiler?
A) A) Draft fan
B) B) Steam separator
C) C) Burner nozzle
D) D) Float switch or level controller
A float switch or level controller maintains proper boiler water levels
to ensure safe and efficient operation and prevent dry firing.
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A stationary engineer is primarily responsible for the operation of
which of the following systems in a facility?
A) A) Boilers, HVAC, and associated mechanical power systems
B) B) Computer programming systems and network administration
C) C) Electrical circuit design for microprocessors
D) D) Automotive engine manufacturing processes
A stationary engineer is tasked with managing and maintaining
large-scale mechanical systems such as boilers, HVAC units, and
related utility equipment to ensure safe and efficient facility
operation.
2. What is the primary purpose of a boiler in an industrial plant?
A) A) To convert electrical energy into chemical energy
B) B) To compress air for pneumatic tools
, C) C) To generate steam or hot water for heating and power
applications
D) D) To cool refrigerant for air conditioning systems
A boiler is designed to produce steam or hot water by transferring
heat energy from fuel combustion or electrical input, which is then
used for heating or mechanical power generation.
3. Which safety device is designed to prevent excessive pressure buildup
in a boiler?
A) A) Water level gauge
B) B) Thermostat controller
C) C) Feedwater pump
D) D) Pressure relief valve
A pressure relief valve automatically releases excess pressure from a
boiler system to prevent rupture or catastrophic failure, ensuring safe
operation under varying load conditions.
4. What is the function of a steam trap in a steam system?
A) A) To increase steam pressure
B) B) To convert steam back into fuel
C) C) To measure steam flow rate
D) D) To remove condensate while preventing steam loss
A steam trap efficiently discharges condensate and non-condensable
gases from steam lines while retaining live steam, maintaining
system efficiency.
,5. Which thermodynamic process occurs when water changes into steam
at constant pressure?
A) A) Condensation
B) B) Superheating
C) C) Compression
D) D) Vaporization (boiling process)
Vaporization is the phase change where water absorbs latent heat at
constant pressure and converts into steam, a key principle in boiler
operation.
6. What is the purpose of a deaerator in a boiler system?
A) A) To increase water hardness
B) B) To cool down steam before use
C) C) To filter solid debris from fuel
D) D) To remove dissolved oxygen and gases from feedwater
A deaerator removes oxygen and other dissolved gases from
feedwater to reduce corrosion in boilers and steam systems.
7. Which instrument is commonly used to measure steam pressure?
A) A) Pyrometer
B) B) Tachometer
C) C) Hydrometer
D) D) Bourdon gauge
A Bourdon gauge is widely used in industrial settings to measure
, pressure in steam and fluid systems through mechanical deformation
of a curved tube.
8. What is the main function of a centrifugal pump in a boiler system?
A) A) To generate electrical current
B) B) To increase steam temperature
C) C) To separate oil from water
D) D) To circulate water through the system
Centrifugal pumps are used to move water through boiler and HVAC
systems by converting rotational energy into fluid flow energy.
9. What does BTU stand for in thermal engineering?
A) A) Boiler Thermal Utility
B) B) Basic Temperature Unit
C) C) Balanced Thermal Output
D) D) British Thermal Unit
A British Thermal Unit (BTU) is the amount of heat required to raise
the temperature of one pound of water by one degree Fahrenheit.
10. Which component controls the water level in a boiler?
A) A) Draft fan
B) B) Steam separator
C) C) Burner nozzle
D) D) Float switch or level controller
A float switch or level controller maintains proper boiler water levels
to ensure safe and efficient operation and prevent dry firing.
