AZ C-74 Boilers, Pressure Vessels &
Industrial Heating Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary function of a boiler in an
industrial system?
A. To store water
B. To circulate air
C. To generate steam or hot water for heating or process use
D. To cool fluids
Rationale: Boilers are designed to generate steam or hot water for
heating, power, or industrial processes.
2. What is the typical purpose of a pressure relief valve on a boiler?
A. To increase pressure
B. To prevent overpressure and ensure safety
C. To control temperature
D. To filter water
Rationale: Pressure relief valves protect the boiler from exceeding safe
pressure limits.
3. Which material is most commonly used for constructing pressure
vessels?
A. Aluminum
B. Carbon steel
C. Plastic
D. Copper
, Rationale: Carbon steel provides high strength, durability, and
resistance to high pressure at a reasonable cost.
4. What is the most common type of boiler used in industrial applications?
A. Fire-tube
B. Electric
C. Water-tube
D. Solar
Rationale: Water-tube boilers can handle higher pressures and
capacities, making them suitable for industrial use.
5. What is the primary danger of a boiler explosion?
A. Water spillage
B. Steam loss
C. Sudden release of pressure causing structural damage and
injury
D. Noise pollution
Rationale: Boiler explosions occur when pressure containment fails,
releasing steam and fragments with catastrophic force.
6. What is the purpose of a boiler economizer?
A. To regulate pressure
B. To recover heat from flue gases and improve efficiency
C. To store fuel
D. To mix water and steam
Rationale: Economizers transfer heat from exhaust gases to feedwater,
improving overall boiler efficiency.
7. Which of the following inspections is mandatory before starting a new
boiler?
A. Annual chemical treatment
B. Hydrostatic test
C. Steam venting
D. Painting
Rationale: Hydrostatic testing ensures the boiler can safely handle
maximum design pressure.
8. Which device prevents backflow of water into a boiler?
A. Pump
B. Strainer
C. Check valve
D. Pressure gauge
, Rationale: Check valves allow flow in one direction, preventing
contamination or damage from reverse flow.
9. What is the typical allowable working pressure for a low-pressure
steam boiler?
A. 15 psi
B. 15–30 psi
C. 50–75 psi
D. 100 psi
Rationale: Low-pressure boilers generally operate between 15 and 30
psi according to most safety codes.
10. Which instrument is used to measure the water level in a boiler?
A. Pressure gauge
B. Thermometer
C. Sight glass
D. Flow meter
Rationale: Sight glasses allow visual monitoring of the water level in
the boiler.
11. Which type of heat exchanger is commonly used in industrial
heating systems?
A. Plate
B. Shell-and-tube
C. Spiral
D. All of the above
Rationale: Plate, shell-and-tube, and spiral heat exchangers are all
used depending on design and application.
12. What is the main purpose of a deaerator in a boiler system?
A. To filter solids
B. To remove dissolved gases from feedwater
C. To circulate steam
D. To measure pressure
Rationale: Deaerators reduce oxygen and carbon dioxide levels in
water to prevent corrosion.
13. Which fuel type is most commonly used in industrial boilers?
A. Wood
B. Natural gas
C. Diesel only
D. Solar
Industrial Heating Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary function of a boiler in an
industrial system?
A. To store water
B. To circulate air
C. To generate steam or hot water for heating or process use
D. To cool fluids
Rationale: Boilers are designed to generate steam or hot water for
heating, power, or industrial processes.
2. What is the typical purpose of a pressure relief valve on a boiler?
A. To increase pressure
B. To prevent overpressure and ensure safety
C. To control temperature
D. To filter water
Rationale: Pressure relief valves protect the boiler from exceeding safe
pressure limits.
3. Which material is most commonly used for constructing pressure
vessels?
A. Aluminum
B. Carbon steel
C. Plastic
D. Copper
, Rationale: Carbon steel provides high strength, durability, and
resistance to high pressure at a reasonable cost.
4. What is the most common type of boiler used in industrial applications?
A. Fire-tube
B. Electric
C. Water-tube
D. Solar
Rationale: Water-tube boilers can handle higher pressures and
capacities, making them suitable for industrial use.
5. What is the primary danger of a boiler explosion?
A. Water spillage
B. Steam loss
C. Sudden release of pressure causing structural damage and
injury
D. Noise pollution
Rationale: Boiler explosions occur when pressure containment fails,
releasing steam and fragments with catastrophic force.
6. What is the purpose of a boiler economizer?
A. To regulate pressure
B. To recover heat from flue gases and improve efficiency
C. To store fuel
D. To mix water and steam
Rationale: Economizers transfer heat from exhaust gases to feedwater,
improving overall boiler efficiency.
7. Which of the following inspections is mandatory before starting a new
boiler?
A. Annual chemical treatment
B. Hydrostatic test
C. Steam venting
D. Painting
Rationale: Hydrostatic testing ensures the boiler can safely handle
maximum design pressure.
8. Which device prevents backflow of water into a boiler?
A. Pump
B. Strainer
C. Check valve
D. Pressure gauge
, Rationale: Check valves allow flow in one direction, preventing
contamination or damage from reverse flow.
9. What is the typical allowable working pressure for a low-pressure
steam boiler?
A. 15 psi
B. 15–30 psi
C. 50–75 psi
D. 100 psi
Rationale: Low-pressure boilers generally operate between 15 and 30
psi according to most safety codes.
10. Which instrument is used to measure the water level in a boiler?
A. Pressure gauge
B. Thermometer
C. Sight glass
D. Flow meter
Rationale: Sight glasses allow visual monitoring of the water level in
the boiler.
11. Which type of heat exchanger is commonly used in industrial
heating systems?
A. Plate
B. Shell-and-tube
C. Spiral
D. All of the above
Rationale: Plate, shell-and-tube, and spiral heat exchangers are all
used depending on design and application.
12. What is the main purpose of a deaerator in a boiler system?
A. To filter solids
B. To remove dissolved gases from feedwater
C. To circulate steam
D. To measure pressure
Rationale: Deaerators reduce oxygen and carbon dioxide levels in
water to prevent corrosion.
13. Which fuel type is most commonly used in industrial boilers?
A. Wood
B. Natural gas
C. Diesel only
D. Solar
