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These 10 free NBII questions are organized by exam domain, so you can see how each part of the National Board Inservice Inspector Commission blueprint is tested. Reveal the answer and explanation under each question.
Domain 1: Inservice Inspection
Question 1
The gas tungsten arc welding (GTAW) procedure specification and supporting procedure qualification record have been checked and found acceptable for a vessel repair. The assigned welder's current performance qualification covers shielded metal arc welding (SMAW) only. The supervisor says the approved procedure is sufficient because the welder has years of repair experience. What must be resolved before the assigned welder starts?
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Correct answer: B - Establish the welder's applicable GTAW performance qualification.
Question 2
No metal will be cut or welded, but an owner proposes increasing a vessel's documented MAWP from 150 to 175 psig at the same design temperature. Engineering calculations support the proposed rating. Under the 2025 NBIC, how should this work be classified and reported?
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Correct answer: D - An alteration, documented on Form R-2.
Domain 2: Boiler and Pressure Vessel Types and Terminology
Question 3
During a boiler walkdown, an inspector traces feedwater from the pump through a tube bank in the flue-gas path and then into the steam drum. The water gains heat in this bank but is not intended to boil there. What component has the inspector traced?
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Correct answer: A - Economizer
Domain 3: Conditions Causing Deterioration or Failures
Question 4
An inspector finds fine, branched cracks near a restrained nozzle weld in a Type 316 stainless-steel vessel handling warm, chloride-bearing water. Thickness mapping shows little general metal loss. Operating records show stable temperature and pressure, with few startup cycles. Which damage mechanism best fits this combination?
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Correct answer: C - Chloride stress-corrosion cracking
Domain 4: Installation
Question 5
Since a backflow preventer was installed on a potable-water heater's supply, the temperature-and-pressure relief valve discharges near the end of each heating cycle. Water temperature remains at the normal 135°F setting. Pressure rises while no water is drawn, then falls promptly when a hot-water tap opens. The relief valve tests correctly, and no expansion tank is installed. Which correction addresses the cause of the recurring discharge?
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Correct answer: D - Provide a correctly sized potable-water expansion tank on the closed side.
Domain 5: Code Calculations
Question 6
Two regions of a cylindrical vessel shell require separate pressure calculations. Region A includes a longitudinal weld: effective wall t = 0.440 in and joint efficiency E = 0.85. Region B is remote parent metal: t = 0.410 in and E = 1.00. For both regions, inside radius R = 18.0 in and allowable stress S = 18,000 psi. Apply P = SEt/(R + 0.6t). The stated walls are available for pressure resistance; no additional allowance is to be deducted, and other code checks do not govern. Identify the governing region and its approximate calculated pressure limit.
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Correct answer: D - Region A, 369 psig
Question 7
Comparable measurements at one uniformly corroding shell location were 0.500 in eight years ago, 0.460 in two years ago, and 0.420 in now. Required wall thickness is 0.300 in. The accepted assessment uses the larger of the long-term and recent corrosion rates and limits the next internal inspection interval to one-half of the estimated remaining life. The jurisdiction also imposes a four-year maximum. Service is below the creep range, and no other damage mechanism limits the interval. What is the latest permissible interval to the next internal inspection?
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Correct answer: B - 3 years
Domain 6: Nondestructive Examination
Question 8
A narrow line is visible at the toe of a carbon-steel weld. Magnetic particle examination produces no indication, but the only applied magnetic field was parallel to that line. Surface preparation, particle condition, and yoke performance have been verified. Before classifying the mark, what should the examiner do next?
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Correct answer: C - Reorient the field across the line and repeat the examination.
Domain 8: Pressure Relief Devices
Question 9
A pressure-reducing station supplies the steam space of a process vessel rated for a 150-psig MAWP. Normal steam demand is 2,800 lb/h, but the evaluated failed-open regulator flow is 6,200 lb/h. The vessel will have one safety relief valve. All candidates have suitable materials and temperature and backpressure ratings. Each listed certified steam capacity applies at the stated setting and permitted overpressure. Which single-valve selection provides the required protection?
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Correct answer: A - Set at 150 psig; certified capacity 6,500 lb/h
Domain 9: Controls and Safety Devices
Question 10
A cast-iron steam-heating boiler is still firing after an independent check confirms water below the lowest permissible level. There are signs that exposed sections have overheated. An operator reaches for the manual feedwater valve. Which instruction takes priority?
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Correct answer: C - Stop firing; withhold feedwater and arrange controlled cooling and a damage assessment.