Maryland Stationary Engineer Grade 4: 200
Practice Questions with Answers & Explanations
– Complete Exam Prep for Low-Pressure Boiler
Operator License (Fire-Tube Boilers, Safety
Devices, Hot Water Systems, Gas & Oil Burners,
ASME Code)
Section 1: Fire-Tube Boilers
1. In a fire-tube boiler, the hot gases pass:
a) Outside the tubes
b) Through the tubes
c) Through the water legs
d) Through the downcomers
Correct answer: b
Hot combustion gases travel inside the tubes, which are surrounded by water.
2. The shell of a fire-tube boiler is constructed according to:
a) NFPA 85
b) ASME Section I
c) ASME Section VIII
d) ASTM A36
Correct answer: b
ASME Section I covers power boiler construction, including fire-tube boilers.
3. A scotch marine boiler is a type of:
a) Water-tube boiler
b) Fire-tube boiler
,c) Electric boiler
d) Cast iron sectional boiler
Correct answer: b
Scotch marine boilers are horizontal fire-tube boilers with multiple passes.
4. The furnace (Morrison tube) in a fire-tube boiler is the:
a) First pass
b) Second pass
c) Third pass
d) Economizer
Correct answer: a
The furnace is the large tube where combustion first occurs (first pass).
5. A dry-top vertical fire-tube boiler has the steam outlet located:
a) Below water level
b) Above water level
c) At the mud drum
d) In the downcomer
Correct answer: b
Dry-top means steam space is above water level, reducing moisture carryover.
6. Maximum allowable working pressure (MAWP) for a low-pressure fire-tube boiler is:
a) 15 psi steam / 160 psi water
b) 100 psi steam / 300 psi water
c) 15 psi steam / 250 psi water
d) 30 psi steam / 160 psi water
Correct answer: a
*Low-pressure steam boilers ≤15 psi; hot water boilers ≤160 psi or 250°F.*
7. The staybolts in a fire-tube boiler prevent:
a) Overheating of tubes
b) Collapse of furnace
c) Flattening of shell ends
d) Scale formation
Correct answer: b
Staybolts support flat surfaces and the furnace against pressure.
,8. A handhole is used for:
a) Flame observation
b) Cleaning and inspection
c) Adding chemicals
d) Venting air
Correct answer: b
Handholes allow manual cleaning of water spaces.
9. The lowest visible water level in a fire-tube boiler should be at least:
a) 1 inch above top of tubes
b) 3 inches above top of tubes
c) 6 inches above top of tubes
d) Level with top of tubes
Correct answer: a
ASME requires at least 1 inch of water above the highest tube to prevent overheating.
10. A two-pass fire-tube boiler has:
a) Gases through furnace then back through tubes
b) Gases through tubes then furnace
c) Vertical tubes only
d) No refractory
Correct answer: a
First pass = furnace; second pass = shell tubes returning gases.
11. The crown sheet in a horizontal fire-tube boiler is located:
a) Above the furnace
b) Below the furnace
c) At the steam drum
d) At the mud ring
Correct answer: a
Crown sheet is the top plate of the furnace; must be covered with water.
12. A fusible plug is placed in the:
a) Steam outlet nozzle
b) Mud drum
c) Crown sheet or above furnace
d) Blowdown line
, Correct answer: c
Fusible plug melts if water level drops, releasing steam to extinguish fire.
13. Staybolts are tested by:
a) Hammer test (ringing)
b) Pressure test to 2x MAWP
c) X-ray
d) Ultrasonic only
Correct answer: a
Hammer test: solid sound = intact, dull sound = cracked or broken.
14. The refractory in a fire-tube boiler:
a) Transfers heat
b) Protects boiler metal from direct flame
c) Increases draft
d) Reduces scale
Correct answer: b
Refractory lining in furnace area resists heat and protects steel.
15. A boiler with 4 passes: gases travel through furnace, then back through tubes three
times:
a) True
b) False
Correct answer: a
Each reversal increases heat transfer.
16. The mud drum in a fire-tube boiler is:
a) Always separate
b) The lowest point in the water space
c) Above the steam drum
d) Not used
Correct answer: b
Mud collects at lowest point (bottom of shell or drum) for blowdown.
17. Boiler rating: 10 BHP = how many sq ft of heating surface?
a) 100
b) 33.5
Practice Questions with Answers & Explanations
– Complete Exam Prep for Low-Pressure Boiler
Operator License (Fire-Tube Boilers, Safety
Devices, Hot Water Systems, Gas & Oil Burners,
ASME Code)
Section 1: Fire-Tube Boilers
1. In a fire-tube boiler, the hot gases pass:
a) Outside the tubes
b) Through the tubes
c) Through the water legs
d) Through the downcomers
Correct answer: b
Hot combustion gases travel inside the tubes, which are surrounded by water.
2. The shell of a fire-tube boiler is constructed according to:
a) NFPA 85
b) ASME Section I
c) ASME Section VIII
d) ASTM A36
Correct answer: b
ASME Section I covers power boiler construction, including fire-tube boilers.
3. A scotch marine boiler is a type of:
a) Water-tube boiler
b) Fire-tube boiler
,c) Electric boiler
d) Cast iron sectional boiler
Correct answer: b
Scotch marine boilers are horizontal fire-tube boilers with multiple passes.
4. The furnace (Morrison tube) in a fire-tube boiler is the:
a) First pass
b) Second pass
c) Third pass
d) Economizer
Correct answer: a
The furnace is the large tube where combustion first occurs (first pass).
5. A dry-top vertical fire-tube boiler has the steam outlet located:
a) Below water level
b) Above water level
c) At the mud drum
d) In the downcomer
Correct answer: b
Dry-top means steam space is above water level, reducing moisture carryover.
6. Maximum allowable working pressure (MAWP) for a low-pressure fire-tube boiler is:
a) 15 psi steam / 160 psi water
b) 100 psi steam / 300 psi water
c) 15 psi steam / 250 psi water
d) 30 psi steam / 160 psi water
Correct answer: a
*Low-pressure steam boilers ≤15 psi; hot water boilers ≤160 psi or 250°F.*
7. The staybolts in a fire-tube boiler prevent:
a) Overheating of tubes
b) Collapse of furnace
c) Flattening of shell ends
d) Scale formation
Correct answer: b
Staybolts support flat surfaces and the furnace against pressure.
,8. A handhole is used for:
a) Flame observation
b) Cleaning and inspection
c) Adding chemicals
d) Venting air
Correct answer: b
Handholes allow manual cleaning of water spaces.
9. The lowest visible water level in a fire-tube boiler should be at least:
a) 1 inch above top of tubes
b) 3 inches above top of tubes
c) 6 inches above top of tubes
d) Level with top of tubes
Correct answer: a
ASME requires at least 1 inch of water above the highest tube to prevent overheating.
10. A two-pass fire-tube boiler has:
a) Gases through furnace then back through tubes
b) Gases through tubes then furnace
c) Vertical tubes only
d) No refractory
Correct answer: a
First pass = furnace; second pass = shell tubes returning gases.
11. The crown sheet in a horizontal fire-tube boiler is located:
a) Above the furnace
b) Below the furnace
c) At the steam drum
d) At the mud ring
Correct answer: a
Crown sheet is the top plate of the furnace; must be covered with water.
12. A fusible plug is placed in the:
a) Steam outlet nozzle
b) Mud drum
c) Crown sheet or above furnace
d) Blowdown line
, Correct answer: c
Fusible plug melts if water level drops, releasing steam to extinguish fire.
13. Staybolts are tested by:
a) Hammer test (ringing)
b) Pressure test to 2x MAWP
c) X-ray
d) Ultrasonic only
Correct answer: a
Hammer test: solid sound = intact, dull sound = cracked or broken.
14. The refractory in a fire-tube boiler:
a) Transfers heat
b) Protects boiler metal from direct flame
c) Increases draft
d) Reduces scale
Correct answer: b
Refractory lining in furnace area resists heat and protects steel.
15. A boiler with 4 passes: gases travel through furnace, then back through tubes three
times:
a) True
b) False
Correct answer: a
Each reversal increases heat transfer.
16. The mud drum in a fire-tube boiler is:
a) Always separate
b) The lowest point in the water space
c) Above the steam drum
d) Not used
Correct answer: b
Mud collects at lowest point (bottom of shell or drum) for blowdown.
17. Boiler rating: 10 BHP = how many sq ft of heating surface?
a) 100
b) 33.5
