NDT Boilermaker Structural Integrity Assessments 2 — Questions and Answers
Question 1: When performing a hydrostatic pressure test on a repaired boiler, the test pressure is typically set at what multiple of the maximum allowable working pressure (MAWP)?
- 1.5 times MAWP (Correct answer)
- 1.0 times MAWP
- 2.0 times MAWP
- 0.75 times MAWP
Correct answer: 1.5 times MAWP
ASME code requires hydrostatic test pressure to be 1.5 times the MAWP to verify structural integrity after repair.
Question 2: Which type of weld discontinuity is MOST likely to cause stress concentration and fatigue cracking in a pressure vessel under cyclic loading?
- Undercut at the weld toe (Correct answer)
- Slight porosity within the weld
- Minor slag inclusions
- Slight weld reinforcement excess
Correct answer: Undercut at the weld toe
Undercut creates a notch at the weld toe that acts as a stress riser, significantly reducing fatigue life under cyclic pressure loading.
Question 3: A boiler inspector discovers a bulge on the crown sheet of a firebox. Which NDT method is BEST suited to determine the thickness remaining in the bulged area?
- Ultrasonic thickness testing (Correct answer)
- Magnetic particle testing
- Liquid penetrant testing
- Visual inspection only
Correct answer: Ultrasonic thickness testing
Ultrasonic thickness testing can accurately measure remaining wall thickness in a bulged area without requiring access to both sides.
Question 4: In structural integrity assessments, what does the term 'fitness for service' (FFS) evaluation primarily determine?
- Whether a component with a flaw can continue safe operation (Correct answer)
- Whether a component meets new construction standards
- The maximum temperature a component can withstand
- The minimum required weld size for a joint
Correct answer: Whether a component with a flaw can continue safe operation
Fitness for service evaluation assesses whether a component containing flaws or damage can remain in service safely until the next planned inspection.
Question 5: Which corrosion mechanism is characterized by localized attack at grain boundaries in austenitic stainless steel boiler components?
- Sensitization and intergranular corrosion (Correct answer)
- Crevice corrosion
- Galvanic corrosion
- Pitting corrosion
Correct answer: Sensitization and intergranular corrosion
Sensitization occurs when chromium carbides precipitate at grain boundaries during improper heat treatment, depleting chromium and making the material vulnerable to intergranular attack.
Question 6: When reviewing radiographic film of a butt weld in a pressure vessel shell, an indication appearing as a light, irregular linear indication likely represents which discontinuity?
- Tungsten inclusion
- Crack or lack of fusion (Correct answer)
- Porosity
- Undercut
Correct answer: Crack or lack of fusion
Cracks and lack of fusion appear as light (low density) irregular linear indications on radiographic film because they are tight planar discontinuities that allow more radiation transmission.
Question 7: A boilermaker notices that stay bolts in a fire-tube boiler are showing signs of shearing. What is the PRIMARY structural concern associated with failed stay bolts?
- Loss of support allowing flat surfaces to bulge under pressure (Correct answer)
- Increased heat transfer efficiency
- Risk of electrochemical corrosion
- Reduction in boiler output capacity
Correct answer: Loss of support allowing flat surfaces to bulge under pressure
Stay bolts support flat surfaces such as tube sheets and firebox walls against internal pressure; failure causes these flat surfaces to bulge outward, potentially leading to catastrophic failure.
NDT Boilermaker Structural Integrity Assessments 2
When performing a hydrostatic pressure test on a repaired boiler, the test pressure is typically set at what multiple of the maximum allowable working pressure (MAWP)?