NDT Boilermaker Structural Integrity Assessments 3 — Questions and Answers
Question 1: Which ASME code section primarily governs the inspection, repair, and alteration of power boilers in service?
- ASME Section I (Power Boilers) (Correct answer)
- ASME Section VIII (Pressure Vessels)
- ASME Section IX (Welding)
- ASME B31.1 (Power Piping)
Correct answer: ASME Section I (Power Boilers)
ASME Section I establishes the rules for construction of power boilers, and its requirements are used as the basis for in-service inspection, repair, and alteration standards.
Question 2: During an acoustic emission (AE) test of a pressure vessel, an increase in AE activity at a specific sensor location during pressurization MOST likely indicates:
- Active crack growth or plastic deformation at that location (Correct answer)
- Normal elastic deformation of the vessel wall
- Proper weld integrity in the monitored zone
- Instrument calibration error
Correct answer: Active crack growth or plastic deformation at that location
Acoustic emission testing detects stress waves released by active crack propagation or plastic deformation, and increased AE activity at a location suggests a developing discontinuity.
Question 3: When assessing corrosion under insulation (CUI) in boiler systems, which NDT technique is preferred because it can inspect through the insulation without removal?
- Pulsed eddy current testing (Correct answer)
- Magnetic particle testing
- Liquid penetrant testing
- Visual inspection
Correct answer: Pulsed eddy current testing
Pulsed eddy current (PEC) testing can measure wall thickness through insulation and coatings without requiring their removal, making it ideal for CUI inspection.
Question 4: A boiler tube shows evidence of external pitting corrosion. What measurement is MOST critical to determine whether the tube must be replaced?
- Remaining wall thickness at the deepest pit (Correct answer)
- Outer diameter of the tube
- Pit density per square inch
- Color of the corrosion products
Correct answer: Remaining wall thickness at the deepest pit
The remaining wall thickness at the deepest pit determines whether sufficient material exists to withstand operating pressure, which is the critical acceptance criterion.
Question 5: In phased array ultrasonic testing (PAUT) of boiler welds, what advantage does electronic scanning provide over conventional single-element UT?
- Multiple angles can be inspected simultaneously without moving the probe (Correct answer)
- Higher maximum test frequency is achievable
- No couplant is required
- It can inspect through thicker materials exclusively
Correct answer: Multiple angles can be inspected simultaneously without moving the probe
PAUT uses electronically controlled focal laws to steer and focus the beam at multiple angles simultaneously, increasing coverage and detection probability without physical probe movement.
Question 6: When interpreting hardness test results after post-weld heat treatment (PWHT) of a boiler weld, excessively HIGH hardness in the heat-affected zone indicates:
- Incomplete stress relief and risk of hydrogen-induced cracking (Correct answer)
- Successful softening of the microstructure
- Excessive carbon migration into the weld
- Over-tempering of the base material
Correct answer: Incomplete stress relief and risk of hydrogen-induced cracking
High hardness after PWHT indicates the heat-affected zone was not adequately stress relieved, leaving a hard martensitic structure that is susceptible to hydrogen-induced cracking.
Question 7: Which of the following best describes the purpose of a 'ligament efficiency' calculation in boiler structural integrity assessment?
- To determine the weakening effect of multiple tube holes on a tube sheet or shell (Correct answer)
- To calculate the maximum allowable pressure for a single tube
- To assess the strength of welded attachments
- To determine insulation thickness requirements
Correct answer: To determine the weakening effect of multiple tube holes on a tube sheet or shell
Ligament efficiency accounts for the reduction in strength caused by the pattern of tube holes in a tube sheet, determining how much of the original plate strength remains between holes.
NDT Boilermaker Structural Integrity Assessments 3
Which ASME code section primarily governs the inspection, repair, and alteration of power boilers in service?