NBBI Exam Prep Free practice test →

Free NBBI Practice Questions

10 free, exam-style NBBI (NBBI) practice questions with answers and explanations. No signup required. Work through them below, then take the full free NBBI practice test to study every exam domain.

Question 1

A pressure vessel shell measured 0.500 in. thick when new. After 8 years in service it measures 0.420 in. What is the average corrosion rate?

  1. 0.080 in./year
  2. 0.010 in./year
  3. 0.063 in./year
  4. 0.053 in./year
Show answer & explanation

Correct answer: B - 0.010 in./year

Question 2

An in-service vessel has a current thickness of 0.380 in., a minimum required thickness of 0.300 in., and a corrosion rate of 0.020 in./year. Using the standard NBIC approach, what is the maximum recommended interval to the next inspection?

  1. 4 years
  2. 8 years
  3. 2 years
  4. 1 year
Show answer & explanation

Correct answer: C - 2 years

Question 3

A cylindrical pressure vessel shell has an inside radius of 24 in., a maximum allowable stress of 17,500 psi, a joint efficiency of 1.0, and a wall thickness of 0.500 in. (no corrosion allowance remaining). Using the ASME Section VIII, Division 1 formula, what is the MAWP?

  1. 181 psi
  2. 306 psi
  3. 720 psi
  4. 360 psi
Show answer & explanation

Correct answer: D - 360 psi

Question 4

A power boiler has a MAWP of 200 psi and is protected by two safety valves. Under ASME Section I, what is the highest permissible set pressure for the additional (higher-set) valve?

  1. 206 psi
  2. 200 psi
  3. 210 psi
  4. 220 psi
Show answer & explanation

Correct answer: A - 206 psi

Question 5

A vertical pressure vessel is filled with water and stands 30 ft tall. The MAWP marked at the top connection is 150 psi. What total pressure acts on the bottom head?

  1. 150 psi
  2. 163 psi
  3. 137 psi
  4. 13 psi
Show answer & explanation

Correct answer: B - 163 psi

Question 6

An austenitic (300-series) stainless steel vessel in chloride-bearing service develops branching cracks under tensile stress, with no measurable general wall thinning. This damage is BEST classified as:

  1. Fatigue cracking
  2. Chloride-induced pitting corrosion
  3. Stress corrosion cracking
  4. Crevice corrosion
Show answer & explanation

Correct answer: C - Stress corrosion cracking

Question 7

An inspector must examine a 300-series (austenitic) stainless steel component for surface-breaking cracks. Which examination method is LEAST suitable because of the component's material?

  1. Liquid penetrant testing
  2. Ultrasonic (angle-beam) testing
  3. Visual examination
  4. Magnetic particle testing
Show answer & explanation

Correct answer: D - Magnetic particle testing

Question 8

Before entering a boiler to perform an internal inspection, which action must the inspector ensure is completed FIRST?

  1. Test the internal atmosphere for oxygen and combustible gases
  2. Isolate and lock out the steam, water, and fuel lines
  3. Put on personal protective equipment
  4. Record the boiler nameplate and certificate data
Show answer & explanation

Correct answer: B - Isolate and lock out the steam, water, and fuel lines

Question 9

On an automatically fired steam boiler, what is the primary purpose of the low-water fuel cutoff?

  1. Maintain the correct feedwater flow to match the steaming rate
  2. Relieve pressure if the boiler exceeds its MAWP
  3. Cut off the fuel when the water drops below a safe level
  4. Indicate the current water level to the operator
Show answer & explanation

Correct answer: C - Cut off the fuel when the water drops below a safe level

Question 10

A safety valve discharge pipe on a power boiler must be sized and arranged so that:

  1. Its diameter is smaller than the valve outlet to increase discharge velocity
  2. It includes a shutoff valve for maintenance access
  3. The discharge is directed toward the operating floor
  4. Back pressure cannot impair the valve's relieving capacity
Show answer & explanation

Correct answer: D - Back pressure cannot impair the valve's relieving capacity

Ready for the real thing?

Practice hundreds more NBBI questions with instant scoring, weak-area drills, and full exam simulations.

Start the free practice test See pricing