3rd Class stationary steam engineer
liCense PraCtiCe exam
100 Questions with CorreCt answers and
detailed rationales
seCtion 1: Boiler ConstruCtion and design
(Questions 1–15)
1. A Scotch Marine boiler is easily identified because it:
A. Has a cylindrical internal furnace
B. Has water inside the tubes
C. Is made of cast iron
D. Has no shell
Correct Answer: A
Rationale: A Scotch Marine boiler is easily identified because it has a cylindrical internal
furnace. This is a defining characteristic of the Scotch Marine design .
2. In a fire-tube boiler, the heat and gases of combustion pass:
A. Around the outside of the tubes
B. Through the tubes
C. Through the shell only
D. Through a separate combustion chamber
Correct Answer: B
Rationale: In a fire-tube boiler, the heat and gases of combustion pass through the tubes,
while water surrounds the tubes on the outside .
3. Water-tube boilers require less water than:
A. Fire-tube boilers
B. Cast-iron boilers
C. Electric boilers
D. Hot water boilers
Correct Answer: A
,Rationale: Water-tube boilers require less water than fire-tube boilers. This allows them to
operate at higher pressures and heat up more quickly .
4. The tubes in a water-tube boiler are fastened by:
A. Welding only
B. Rolling and expanding in drums and headers
C. Bolting
D. Riveting
Correct Answer: B
Rationale: The tubes in a water-tube boiler are fastened by rolling and expanding them into
drums and headers .
5. _______ boilers can operate at higher pressures than fire-tube boilers.
A. Cast-iron
B. Water-tube
C. Scotch Marine
D. Fire-tube
Correct Answer: B
Rationale: Water-tube boilers can operate at higher pressures than fire-tube boilers because
the smaller diameter tubes can withstand greater pressure .
6. A water column is connected to the boiler with a minimum of _______ inch pipe.
A. 1/2
B. 3/4
C. 1
D. 2
Correct Answer: C
Rationale: Water columns are connected to the boiler with a minimum of 1-inch pipe .
7. The maximum size bottom blowdown valve on a boiler is:
A. 1 inch
B. 1-1/2 inches
C. 2 inches
D. 2-1/2 inches
Correct Answer: D
Rationale: The maximum size bottom blowdown valve on a boiler is 2-1/2 inches .
8. The minimum size of a water column blowdown valve is:
, A. 1/4 inch
B. 1/2 inch
C. 3/4 inch
D. 1 inch
Correct Answer: C
Rationale: The minimum size of a water column blowdown valve is 3/4 inch .
9. A boiler connected in battery requires a free blowing drain between the two stop valves
when the:
A. Boiler has a manhole opening
B. Boiler is above 100 PSI
C. Boiler has no safety valve
D. Boiler is a water-tube type
Correct Answer: A
Rationale: A boiler connected in battery requires a free blowing drain between the two stop
valves when the boiler has a manhole opening .
10. Water wall tubes protect the refractory and:
A. Decrease boiler heating surface
B. Increase boiler heating surface
C. Have no effect on heating surface
D. Replace the need for a drum
Correct Answer: B
Rationale: Water wall tubes protect the refractory and increase boiler heating surface .
11. A deposit of scale or mud in an HRT boiler could cause:
A. A bag to develop
B. Improved efficiency
C. Lower stack temperature
D. Increased steam production
Correct Answer: A
Rationale: A deposit of scale or mud in an HRT (horizontal return tubular) boiler could cause
a bag to develop due to uneven heating and expansion .
12. A sudden rise in chimney temperature with no increase in load indicates:
A. Improved combustion
B. There is a broken baffle
liCense PraCtiCe exam
100 Questions with CorreCt answers and
detailed rationales
seCtion 1: Boiler ConstruCtion and design
(Questions 1–15)
1. A Scotch Marine boiler is easily identified because it:
A. Has a cylindrical internal furnace
B. Has water inside the tubes
C. Is made of cast iron
D. Has no shell
Correct Answer: A
Rationale: A Scotch Marine boiler is easily identified because it has a cylindrical internal
furnace. This is a defining characteristic of the Scotch Marine design .
2. In a fire-tube boiler, the heat and gases of combustion pass:
A. Around the outside of the tubes
B. Through the tubes
C. Through the shell only
D. Through a separate combustion chamber
Correct Answer: B
Rationale: In a fire-tube boiler, the heat and gases of combustion pass through the tubes,
while water surrounds the tubes on the outside .
3. Water-tube boilers require less water than:
A. Fire-tube boilers
B. Cast-iron boilers
C. Electric boilers
D. Hot water boilers
Correct Answer: A
,Rationale: Water-tube boilers require less water than fire-tube boilers. This allows them to
operate at higher pressures and heat up more quickly .
4. The tubes in a water-tube boiler are fastened by:
A. Welding only
B. Rolling and expanding in drums and headers
C. Bolting
D. Riveting
Correct Answer: B
Rationale: The tubes in a water-tube boiler are fastened by rolling and expanding them into
drums and headers .
5. _______ boilers can operate at higher pressures than fire-tube boilers.
A. Cast-iron
B. Water-tube
C. Scotch Marine
D. Fire-tube
Correct Answer: B
Rationale: Water-tube boilers can operate at higher pressures than fire-tube boilers because
the smaller diameter tubes can withstand greater pressure .
6. A water column is connected to the boiler with a minimum of _______ inch pipe.
A. 1/2
B. 3/4
C. 1
D. 2
Correct Answer: C
Rationale: Water columns are connected to the boiler with a minimum of 1-inch pipe .
7. The maximum size bottom blowdown valve on a boiler is:
A. 1 inch
B. 1-1/2 inches
C. 2 inches
D. 2-1/2 inches
Correct Answer: D
Rationale: The maximum size bottom blowdown valve on a boiler is 2-1/2 inches .
8. The minimum size of a water column blowdown valve is:
, A. 1/4 inch
B. 1/2 inch
C. 3/4 inch
D. 1 inch
Correct Answer: C
Rationale: The minimum size of a water column blowdown valve is 3/4 inch .
9. A boiler connected in battery requires a free blowing drain between the two stop valves
when the:
A. Boiler has a manhole opening
B. Boiler is above 100 PSI
C. Boiler has no safety valve
D. Boiler is a water-tube type
Correct Answer: A
Rationale: A boiler connected in battery requires a free blowing drain between the two stop
valves when the boiler has a manhole opening .
10. Water wall tubes protect the refractory and:
A. Decrease boiler heating surface
B. Increase boiler heating surface
C. Have no effect on heating surface
D. Replace the need for a drum
Correct Answer: B
Rationale: Water wall tubes protect the refractory and increase boiler heating surface .
11. A deposit of scale or mud in an HRT boiler could cause:
A. A bag to develop
B. Improved efficiency
C. Lower stack temperature
D. Increased steam production
Correct Answer: A
Rationale: A deposit of scale or mud in an HRT (horizontal return tubular) boiler could cause
a bag to develop due to uneven heating and expansion .
12. A sudden rise in chimney temperature with no increase in load indicates:
A. Improved combustion
B. There is a broken baffle
