MD Stationary Engineer Grade 1
Exam Questions and Answers Plus
Rationales
1. Which of the following is the main purpose of a fusible plug in a
boiler?
A. To regulate steam temperature
B. To relieve excess pressure
C. To detect low-water condition and provide protection **
D. To measure feedwater conductivity
The fusible plug is filled with a soft alloy that melts at a predetermined
high temperature when water level drops, providing protection against
overheating the boiler shell.
2. When measuring steam pressure with a gauge located below the
header, you must correct for the elevation difference. If the gauge
is 10 ft below the header, which correction applies approximately?
A. Add 4.43 psi to the reading
B. Subtract 4.33 psi from the reading **
C. Add 0.433 psi to the reading
D. No correction is necessary
Approximately 0.433 psi for each foot of vertical difference – if the
gauge is below the header you subtract the appropriate value.
3. Which of the following best describes “wiredrawing” in steam
systems?
A. A crack in the boiler shell due to heat
B. A reduction in steam pressure through a throttled valve causing
, erosion **
C. A sudden expansion of steam in a relief valve
D. A steam trap failing to discharge condensate
Wiredrawing refers to the pressure drop and velocity increase as steam
passes through a restricted or throttled valve, which can cause erosion
of the seat and disc.
4. What is the primary advantage of superheated steam in a turbine
application?
A. Lower temperature to reduce stress
B. Less condensate formation and increased work output **
C. Higher humidity in the steam
D. Smaller turbine size required
By superheating steam you reduce moisture content at turbine exhaust,
increase efficiency and reduce blade erosion and maintenance.
5. In boiler feedwater treatment, which of the following is used to
remove dissolved oxygen?
A. Caustic soda
B. Sodium sulfite **
C. Lime
D. Carbon dioxide
Sodium sulfite is an oxygen scavenger used in boiler feedwater systems
to remove dissolved oxygen and reduce corrosion.
6. If a pump discharge gauge reads 150 psi, how high (in feet) could a
column of water rise, ignoring friction losses? (Use ~0.433 psi per
foot)
A. About 300 ft
B. About 346 ft **
C. About 225 ft
D. About 150 ft
, 150 divided by ~0.433 ≈ 346 ft. This simple head-pressure conversion
is common in pump/boiler calculations.
7. Which schedule item is most likely required for safe operation of
a steam boiler?
A. Daily check of makeup water level
B. Monthly inspection of fuse holder
C. Annual inspection of safety valve capacity **
D. Weekly lubrication of turbine bearings
Safety valves must be tested/inspected to ensure they will relieve load
under fault or high load conditions — often annually.
8. Which of these statements is true about the selection of a
centrifugal pump in an industrial water system?
A. Smaller impeller always increases head
B. Larger suction pipeline always reduces capacity
C. The type of liquid, temperature, head, space limitations all must
be evaluated **
D. Only the flow rate matters
Pump selection must consider multiple factors — fluid properties,
temperature, required head, suction conditions etc.
9. What does an air ejector in a steam condenser system do?
A. Remove condensate from the system
B. Remove non-condensable gases and air from the condenser
vacuum system **
C. Provide lubrication to the turbine
D. Measure the vacuum level in the condenser
An air ejector uses steam or a jet to draw out air or vapours from the
condenser to maintain vacuum and system efficiency.
, 10. In combustion theory for a boiler, which of the following
describes the “theoretical air” concept?
A. The actual air required plus excess
B. The minimum air required to completely burn the fuel **
C. The air provided to the burner only
D. The air used to cool the flue gases
Theoretical air is the exact amount of air needed for complete
combustion without excess; actual systems use excess for safety.
11. In boiler operation, what is the function of a sample cooler?
A. To reduce feedwater temperature before entering the boiler
B. To cool the person taking the sample
C. To cool a sample of boiler feedwater or condensate to avoid
evaporation and get accurate test readings **
D. To condense steam for the feedwater tank
Cooling the sample ensures accurate chemical test results by
minimizing evaporation or temperature-related errors.
12. What must never be placed between the boiler and its
safety relief valve?
A. A shut-off valve **
B. A pressure gauge
C. A strainer
D. A check valve
Placing a shut-off valve between the boiler and its relief valve would
disable the safety function of the relief valve, which is prohibited.
13. Which of these is a disadvantage of using a steam injector
for feedwater supply?
A. No moving parts
B. Low initial cost
C. Limited to low pressures and can scale easily **
Exam Questions and Answers Plus
Rationales
1. Which of the following is the main purpose of a fusible plug in a
boiler?
A. To regulate steam temperature
B. To relieve excess pressure
C. To detect low-water condition and provide protection **
D. To measure feedwater conductivity
The fusible plug is filled with a soft alloy that melts at a predetermined
high temperature when water level drops, providing protection against
overheating the boiler shell.
2. When measuring steam pressure with a gauge located below the
header, you must correct for the elevation difference. If the gauge
is 10 ft below the header, which correction applies approximately?
A. Add 4.43 psi to the reading
B. Subtract 4.33 psi from the reading **
C. Add 0.433 psi to the reading
D. No correction is necessary
Approximately 0.433 psi for each foot of vertical difference – if the
gauge is below the header you subtract the appropriate value.
3. Which of the following best describes “wiredrawing” in steam
systems?
A. A crack in the boiler shell due to heat
B. A reduction in steam pressure through a throttled valve causing
, erosion **
C. A sudden expansion of steam in a relief valve
D. A steam trap failing to discharge condensate
Wiredrawing refers to the pressure drop and velocity increase as steam
passes through a restricted or throttled valve, which can cause erosion
of the seat and disc.
4. What is the primary advantage of superheated steam in a turbine
application?
A. Lower temperature to reduce stress
B. Less condensate formation and increased work output **
C. Higher humidity in the steam
D. Smaller turbine size required
By superheating steam you reduce moisture content at turbine exhaust,
increase efficiency and reduce blade erosion and maintenance.
5. In boiler feedwater treatment, which of the following is used to
remove dissolved oxygen?
A. Caustic soda
B. Sodium sulfite **
C. Lime
D. Carbon dioxide
Sodium sulfite is an oxygen scavenger used in boiler feedwater systems
to remove dissolved oxygen and reduce corrosion.
6. If a pump discharge gauge reads 150 psi, how high (in feet) could a
column of water rise, ignoring friction losses? (Use ~0.433 psi per
foot)
A. About 300 ft
B. About 346 ft **
C. About 225 ft
D. About 150 ft
, 150 divided by ~0.433 ≈ 346 ft. This simple head-pressure conversion
is common in pump/boiler calculations.
7. Which schedule item is most likely required for safe operation of
a steam boiler?
A. Daily check of makeup water level
B. Monthly inspection of fuse holder
C. Annual inspection of safety valve capacity **
D. Weekly lubrication of turbine bearings
Safety valves must be tested/inspected to ensure they will relieve load
under fault or high load conditions — often annually.
8. Which of these statements is true about the selection of a
centrifugal pump in an industrial water system?
A. Smaller impeller always increases head
B. Larger suction pipeline always reduces capacity
C. The type of liquid, temperature, head, space limitations all must
be evaluated **
D. Only the flow rate matters
Pump selection must consider multiple factors — fluid properties,
temperature, required head, suction conditions etc.
9. What does an air ejector in a steam condenser system do?
A. Remove condensate from the system
B. Remove non-condensable gases and air from the condenser
vacuum system **
C. Provide lubrication to the turbine
D. Measure the vacuum level in the condenser
An air ejector uses steam or a jet to draw out air or vapours from the
condenser to maintain vacuum and system efficiency.
, 10. In combustion theory for a boiler, which of the following
describes the “theoretical air” concept?
A. The actual air required plus excess
B. The minimum air required to completely burn the fuel **
C. The air provided to the burner only
D. The air used to cool the flue gases
Theoretical air is the exact amount of air needed for complete
combustion without excess; actual systems use excess for safety.
11. In boiler operation, what is the function of a sample cooler?
A. To reduce feedwater temperature before entering the boiler
B. To cool the person taking the sample
C. To cool a sample of boiler feedwater or condensate to avoid
evaporation and get accurate test readings **
D. To condense steam for the feedwater tank
Cooling the sample ensures accurate chemical test results by
minimizing evaporation or temperature-related errors.
12. What must never be placed between the boiler and its
safety relief valve?
A. A shut-off valve **
B. A pressure gauge
C. A strainer
D. A check valve
Placing a shut-off valve between the boiler and its relief valve would
disable the safety function of the relief valve, which is prohibited.
13. Which of these is a disadvantage of using a steam injector
for feedwater supply?
A. No moving parts
B. Low initial cost
C. Limited to low pressures and can scale easily **
