CRI CRI Pipe & Pressure Vessel Inspection 2 — Questions and Answers
Question 1: What characteristic radiographic appearance distinguishes internal corrosion in a pipe from a weld discontinuity?
- Corrosion appears as irregular dark areas or pitting with no sharp edges, not aligned with weld features (Correct answer)
- Corrosion always appears as light areas
- Corrosion follows the weld bead profile
- Corrosion is indistinguishable from slag inclusions
Correct answer: Corrosion appears as irregular dark areas or pitting with no sharp edges, not aligned with weld features
Internal corrosion produces irregular, diffuse dark density variations that do not align with the weld geometry and typically show a pitted or channeled pattern.
Question 2: For pressure vessel nozzle-to-shell welds, which examination technique is used when film cannot be placed inside the nozzle bore?
- Double-wall single-image (DWSI) technique (Correct answer)
- Double-wall double-image (DWDI) technique
- Panoramic technique
- Single-wall single-image (SWSI) technique
Correct answer: Double-wall single-image (DWSI) technique
DWSI technique is used for nozzle welds where film placement inside is impossible; the source is placed outside and the image of only the far-side wall is interpreted.
Question 3: A pressure vessel radiograph shows a region of lighter density (less exposure) at the edge of the weld near the nozzle junction. What is the most likely cause?
- Increased material thickness at the reinforcement pad reducing radiation transmission (Correct answer)
- Burn-through at the weld toe
- Film processing error
- Scattered radiation from the vessel shell
Correct answer: Increased material thickness at the reinforcement pad reducing radiation transmission
A reinforcement pad or extra material at a nozzle junction increases local thickness, attenuating more radiation and producing a lighter (lower density) area on film.
Question 4: Per ASME Section VIII, when is 100% radiographic examination required for pressure vessel Category A and B welds?
- When the vessel is in lethal service or designed for over 1.5 times joint efficiency credit (Correct answer)
- When wall thickness exceeds 1 inch
- Only when the customer specifies it
- Only for vessels above 300 psi MAWP
Correct answer: When the vessel is in lethal service or designed for over 1.5 times joint efficiency credit
ASME Section VIII Division 1 mandates full RT for vessels in lethal service and when the designer takes full (1.0) joint efficiency credit for weld design.
Question 5: What is the primary reason that helical (spiral) weld seams in pipe require special consideration when planning radiographic examination?
- The weld angle to the pipe axis affects the projection geometry and requires angled source placement to maintain proper coverage (Correct answer)
- Spiral welds are exempt from radiographic examination
- Spiral welds always require gamma ray sources
- The weld is too short for IQI placement
Correct answer: The weld angle to the pipe axis affects the projection geometry and requires angled source placement to maintain proper coverage
The helical angle of a spiral weld means a straight radiographic beam would not be perpendicular to the weld plane, requiring angled source placement to properly image the weld cross-section.
Question 6: In pressure vessel radiography, what does the term 'volumetric examination' mean?
- Examination that detects discontinuities throughout the full weld cross-section volume, not just the surface (Correct answer)
- Examination of vessels above a certain volume capacity
- Examination using a volumetric IQI only
- A multi-shot technique using more than three exposures
Correct answer: Examination that detects discontinuities throughout the full weld cross-section volume, not just the surface
Volumetric examination means the full through-thickness volume of the weld is interrogated, distinguishing RT and UT from surface-only methods like MT or PT.
CRI CRI Pipe & Pressure Vessel Inspection 2
What characteristic radiographic appearance distinguishes internal corrosion in a pipe from a weld discontinuity?