Minnesota Special Engineer Boiler License Exam |
Minnesota Special Boiler Engineer License Study Guide
& Exam Prep 2026/2027 | Minnesota DLI Boiler License,
Special Engineer Certification, Boiler Operation &
Maintenance, Low-Pressure Boiler Systems, Boiler
Safety, Controls & Safety Devices, Steam & Hot Water
Boilers, Boiler Components, Operating Procedures,
Minnesota Boiler Laws & Rules, Practice Questions,
Answers & Detailed Rationales
Question 1: A boiler has a maximum allowable working pressure (MAWP) of
150 psig. During a routine inspection, the safety valve is found to be set at 160
psig. According to ASME Code and Minnesota regulations, what is the most
appropriate course of action?
A. Lower the boiler pressure to 140 psig to provide a safety margin.
B. No action is required as the safety valve is within acceptable tolerance.
C. Immediately take the boiler out of service and have the safety valve reset to 150 psig
or lower.
D. Increase the boiler MAWP to 160 psig to match the safety valve setting.
CORRECT ANSWER: C. Immediately take the boiler out of service and have the
safety valve reset to 150 psig or lower.
Rationale: The safety valve set pressure must not exceed the MAWP of the boiler. ASME
Code and Minnesota regulations require safety valves to be set at or below the MAWP to
ensure the boiler is protected from overpressure conditions. A valve set above MAWP
would allow the boiler to exceed its design pressure, which is a serious safety violation
that requires immediate correction.
Question 2: A low-pressure steam boiler is operating at 12 psig and is equipped
with two safety relief valves. One valve is set at 15 psig and the other at 25
psig. Which is the most critical violation of ASME Code and Minnesota rules?
A. The two valves must have the same set pressure to ensure simultaneous opening.
B. The valve set at 25 psig is set higher than the MAWP, creating a risk of
overpressurization.
C. The relieving capacity of the valve set at 25 psig is insufficient.
D. The valve set at 15 psig is too low for a low-pressure boiler.
CORRECT ANSWER: B. The valve set at 25 psig is set higher than the MAWP,
creating a risk of overpressurization.
Rationale: For low-pressure heating boilers, the safety relief valve set pressure must not
exceed the MAWP, which is typically 15 psig for steam boilers. The 25 psig valve
exceeds this limit and would not open until pressure is already above the boiler's design
,maximum, risking a dangerous overpressure condition. Valves may have different set
pressures as long as they are within code limits .
Question 3: What is the primary reason for conducting a hydrostatic test on a
new boiler installation?
A. To verify the safety relief valve operates at its set pressure.
B. To prove the boiler can withstand 1.5 times the MAWP without leakage or
deformation.
C. To check the burner flame failure response time.
D. To calibrate the water level controls.
CORRECT ANSWER: B. To prove the boiler can withstand 1.5 times the MAWP
without leakage or deformation.
Rationale: A hydrostatic test is performed to verify the integrity of the pressure vessel by
pressurizing it with water to 1.5 times the MAWP (or per code) and checking for leaks or
deformation. This ensures the boiler can safely operate at its design pressure. Safety
relief valves, burner response, and controls are tested separately through other
procedures .
Question 4: A high-pressure boiler plant of 31 to 200 horsepower may be left
unattended for a maximum of how long when the premises are occupied by
employees or the public?
A. 30 minutes
B. 1 hour
C. 2 hours
D. 4 hours
CORRECT ANSWER: C. 2 hours
Rationale: According to Minnesota Rules 5225.1180, a high-pressure boiler plant of 31
to 200 horsepower may be left in operation unattended by an operating engineer for no
more than two consecutive hours when the premises are occupied by employees or the
public .
Question 5: An engineer discovers a defect in a boiler that requires repairs not
of a routine nature. What is the engineer's first obligation?
A. Attempt to make temporary repairs to keep the boiler in service.
B. Notify the boiler inspector.
C. Continue operating the boiler at reduced pressure.
D. Order replacement parts immediately.
,CORRECT ANSWER: B. Notify the boiler inspector.
Rationale: When a defect requiring non-routine repairs is discovered, the operating
engineer must notify the boiler inspector. This ensures proper evaluation and repair
procedures are followed according to code requirements. Attempting temporary repairs
without authorization or continuing to operate a compromised boiler would be a
violation of safety regulations .
Question 6: What is the minimum passing score for the State of Minnesota
boiler license test?
A. 60%
B. 65%
C. 70%
D. 75%
CORRECT ANSWER: C. 70%
Rationale: The Minnesota boiler license test requires a minimum passing score of 70%.
This applies to all license classifications including Special Engineer .
Question 7: A low-pressure boiler cannot be left unattended for more than how
many hours?
A. 24 hours
B. 36 hours
C. 48 hours
D. 72 hours
CORRECT ANSWER: C. 48 hours
Rationale: According to Minnesota regulations, a low-pressure boiler cannot be left
unattended for more than 48 hours. This requirement ensures that boilers are regularly
checked for proper operation and safety .
Question 8: A Minnesota Special Engineer license allows the holder to be in
charge of a boiler up to what maximum horsepower?
A. 25 horsepower
B. 50 horsepower
C. 75 horsepower
D. 100 horsepower
CORRECT ANSWER: B. 50 horsepower
, Rationale: A Minnesota Special Engineer license permits the holder to be in charge of a
boiler up to 50 horsepower. This is a defined limitation of the license classification .
Question 9: A mud drum would typically be found on what type of boiler?
A. Fire-tube boiler
B. Water-tube boiler
C. Cast iron sectional boiler
D. Scotch marine boiler
CORRECT ANSWER: B. Water-tube boiler
Rationale: Mud drums are a component typically found on water-tube boilers. They are
located at the lowest point of the boiler and collect sediment and solids (mud) that settle
out of the boiler water, allowing for removal through blowdown .
Question 10: A gate valve offers what characteristic compared to other valve
types?
A. The highest resistance to flow.
B. The least resistance to flow.
C. The most precise flow control.
D. The best throttling capability.
CORRECT ANSWER: B. The least resistance to flow.
Rationale: Gate valves offer the least resistance to flow because they have a straight-
through design with no obstructions when fully open. This makes them ideal for
isolation service where minimal pressure drop is desired, but they are not suitable for
throttling applications .
Question 11: A hydrostatic test pressurizes the boiler to what multiple of its
MAWP?
A. 1.0 times
B. 1.25 times
C. 1.5 times
D. 2.0 times
CORRECT ANSWER: C. 1.5 times
Rationale: A hydrostatic test is typically performed at 1.5 times the MAWP of the boiler.
This test pressure is used to verify the integrity of the pressure vessel and ensure it can
safely contain its design pressure without leakage or deformation .
Minnesota Special Boiler Engineer License Study Guide
& Exam Prep 2026/2027 | Minnesota DLI Boiler License,
Special Engineer Certification, Boiler Operation &
Maintenance, Low-Pressure Boiler Systems, Boiler
Safety, Controls & Safety Devices, Steam & Hot Water
Boilers, Boiler Components, Operating Procedures,
Minnesota Boiler Laws & Rules, Practice Questions,
Answers & Detailed Rationales
Question 1: A boiler has a maximum allowable working pressure (MAWP) of
150 psig. During a routine inspection, the safety valve is found to be set at 160
psig. According to ASME Code and Minnesota regulations, what is the most
appropriate course of action?
A. Lower the boiler pressure to 140 psig to provide a safety margin.
B. No action is required as the safety valve is within acceptable tolerance.
C. Immediately take the boiler out of service and have the safety valve reset to 150 psig
or lower.
D. Increase the boiler MAWP to 160 psig to match the safety valve setting.
CORRECT ANSWER: C. Immediately take the boiler out of service and have the
safety valve reset to 150 psig or lower.
Rationale: The safety valve set pressure must not exceed the MAWP of the boiler. ASME
Code and Minnesota regulations require safety valves to be set at or below the MAWP to
ensure the boiler is protected from overpressure conditions. A valve set above MAWP
would allow the boiler to exceed its design pressure, which is a serious safety violation
that requires immediate correction.
Question 2: A low-pressure steam boiler is operating at 12 psig and is equipped
with two safety relief valves. One valve is set at 15 psig and the other at 25
psig. Which is the most critical violation of ASME Code and Minnesota rules?
A. The two valves must have the same set pressure to ensure simultaneous opening.
B. The valve set at 25 psig is set higher than the MAWP, creating a risk of
overpressurization.
C. The relieving capacity of the valve set at 25 psig is insufficient.
D. The valve set at 15 psig is too low for a low-pressure boiler.
CORRECT ANSWER: B. The valve set at 25 psig is set higher than the MAWP,
creating a risk of overpressurization.
Rationale: For low-pressure heating boilers, the safety relief valve set pressure must not
exceed the MAWP, which is typically 15 psig for steam boilers. The 25 psig valve
exceeds this limit and would not open until pressure is already above the boiler's design
,maximum, risking a dangerous overpressure condition. Valves may have different set
pressures as long as they are within code limits .
Question 3: What is the primary reason for conducting a hydrostatic test on a
new boiler installation?
A. To verify the safety relief valve operates at its set pressure.
B. To prove the boiler can withstand 1.5 times the MAWP without leakage or
deformation.
C. To check the burner flame failure response time.
D. To calibrate the water level controls.
CORRECT ANSWER: B. To prove the boiler can withstand 1.5 times the MAWP
without leakage or deformation.
Rationale: A hydrostatic test is performed to verify the integrity of the pressure vessel by
pressurizing it with water to 1.5 times the MAWP (or per code) and checking for leaks or
deformation. This ensures the boiler can safely operate at its design pressure. Safety
relief valves, burner response, and controls are tested separately through other
procedures .
Question 4: A high-pressure boiler plant of 31 to 200 horsepower may be left
unattended for a maximum of how long when the premises are occupied by
employees or the public?
A. 30 minutes
B. 1 hour
C. 2 hours
D. 4 hours
CORRECT ANSWER: C. 2 hours
Rationale: According to Minnesota Rules 5225.1180, a high-pressure boiler plant of 31
to 200 horsepower may be left in operation unattended by an operating engineer for no
more than two consecutive hours when the premises are occupied by employees or the
public .
Question 5: An engineer discovers a defect in a boiler that requires repairs not
of a routine nature. What is the engineer's first obligation?
A. Attempt to make temporary repairs to keep the boiler in service.
B. Notify the boiler inspector.
C. Continue operating the boiler at reduced pressure.
D. Order replacement parts immediately.
,CORRECT ANSWER: B. Notify the boiler inspector.
Rationale: When a defect requiring non-routine repairs is discovered, the operating
engineer must notify the boiler inspector. This ensures proper evaluation and repair
procedures are followed according to code requirements. Attempting temporary repairs
without authorization or continuing to operate a compromised boiler would be a
violation of safety regulations .
Question 6: What is the minimum passing score for the State of Minnesota
boiler license test?
A. 60%
B. 65%
C. 70%
D. 75%
CORRECT ANSWER: C. 70%
Rationale: The Minnesota boiler license test requires a minimum passing score of 70%.
This applies to all license classifications including Special Engineer .
Question 7: A low-pressure boiler cannot be left unattended for more than how
many hours?
A. 24 hours
B. 36 hours
C. 48 hours
D. 72 hours
CORRECT ANSWER: C. 48 hours
Rationale: According to Minnesota regulations, a low-pressure boiler cannot be left
unattended for more than 48 hours. This requirement ensures that boilers are regularly
checked for proper operation and safety .
Question 8: A Minnesota Special Engineer license allows the holder to be in
charge of a boiler up to what maximum horsepower?
A. 25 horsepower
B. 50 horsepower
C. 75 horsepower
D. 100 horsepower
CORRECT ANSWER: B. 50 horsepower
, Rationale: A Minnesota Special Engineer license permits the holder to be in charge of a
boiler up to 50 horsepower. This is a defined limitation of the license classification .
Question 9: A mud drum would typically be found on what type of boiler?
A. Fire-tube boiler
B. Water-tube boiler
C. Cast iron sectional boiler
D. Scotch marine boiler
CORRECT ANSWER: B. Water-tube boiler
Rationale: Mud drums are a component typically found on water-tube boilers. They are
located at the lowest point of the boiler and collect sediment and solids (mud) that settle
out of the boiler water, allowing for removal through blowdown .
Question 10: A gate valve offers what characteristic compared to other valve
types?
A. The highest resistance to flow.
B. The least resistance to flow.
C. The most precise flow control.
D. The best throttling capability.
CORRECT ANSWER: B. The least resistance to flow.
Rationale: Gate valves offer the least resistance to flow because they have a straight-
through design with no obstructions when fully open. This makes them ideal for
isolation service where minimal pressure drop is desired, but they are not suitable for
throttling applications .
Question 11: A hydrostatic test pressurizes the boiler to what multiple of its
MAWP?
A. 1.0 times
B. 1.25 times
C. 1.5 times
D. 2.0 times
CORRECT ANSWER: C. 1.5 times
Rationale: A hydrostatic test is typically performed at 1.5 times the MAWP of the boiler.
This test pressure is used to verify the integrity of the pressure vessel and ensure it can
safely contain its design pressure without leakage or deformation .
