CRI CRI Pipe & Pressure Vessel Inspection 1 — Questions and Answers
Question 1: For radiographic examination of pipe welds per ASME B31.3, what is the minimum source-to-object distance (SOD) requirement relative to the source size?
- The SOD must produce geometric unsharpness (Ug) no greater than 1/100 of the weld thickness or 0.020 inch, whichever is smaller (Correct answer)
- The SOD must be at least 12 inches regardless of source size
- The SOD is left entirely to the radiographer's discretion
- The SOD must be at least 10 times the source diameter
Correct answer: The SOD must produce geometric unsharpness (Ug) no greater than 1/100 of the weld thickness or 0.020 inch, whichever is smaller
ASME B31.3 requires that geometric unsharpness not exceed the lesser of 1/100 of the weld thickness or 0.020 inch, which governs minimum SOD selection.
Question 2: Which radiographic technique is preferred for inspecting small-diameter pipe welds (under 3.5 inch OD) to achieve full-volume coverage in a single exposure?
- Double-wall double-image (DWDI) (Correct answer)
- Single-wall single-image (SWSI)
- Double-wall single-image (DWSI)
- Panoramic technique
Correct answer: Double-wall double-image (DWDI)
DWDI technique is used for small-diameter pipe because the source is placed outside and the image of the near and far wall weld are both recorded on the same film.
Question 3: When using the elliptical (double-wall double-image) technique on pipe, what is the recommended offset angle to separate the two weld images?
- Approximately 15–25 degrees from the plane of the weld (Correct answer)
- Exactly 45 degrees
- 90 degrees
- 0 degrees (superimposed)
Correct answer: Approximately 15–25 degrees from the plane of the weld
An offset angle of 15–25 degrees separates the two weld oval images on the film to allow independent interpretation of each wall.
Question 4: For a circumferential weld in a pressure vessel shell, how many IQI (penetrameter) placements are required for a full radiographic examination per ASME Section V?
- One IQI per film for film lengths up to 14 inches, two IQIs for longer films (Correct answer)
- One IQI per weld regardless of film length
- IQIs are placed every 6 inches along the weld
- Two IQIs at each end of every film
Correct answer: One IQI per film for film lengths up to 14 inches, two IQIs for longer films
ASME Section V Article 2 requires one IQI per film for single-film exposures up to 14 inches, and two IQIs (one at each end) for longer films.
Question 5: In pipeline girth weld radiography, what is the purpose of the 'back-scatter' lead marker ('B') placed behind the film?
- To detect radiation scattered from behind the film that could degrade image quality (Correct answer)
- To identify the technician performing the examination
- To mark the weld start location
- To measure source-to-film distance
Correct answer: To detect radiation scattered from behind the film that could degrade image quality
If the 'B' marker appears as a light image on the radiograph, back-scatter is excessive and the exposure must be repeated with added back-scatter shielding.
Question 6: Which radiographic exposure arrangement provides the most uniform density across the full circumference of a large-diameter vessel shell weld in a single shot?
- Panoramic internal source technique with film wrapped around the outside (Correct answer)
- Multiple external source exposures with overlapping films
- DWSI technique from one side
- Gamma source at 90 degrees from film
Correct answer: Panoramic internal source technique with film wrapped around the outside
Panoramic technique places the source at the vessel centerline so radiation travels equal distances to all points on the circumferential weld, yielding uniform density.
CRI CRI Pipe & Pressure Vessel Inspection 1
For radiographic examination of pipe welds per ASME B31.3, what is the minimum source-to-object distance (SOD) requirement relative to the source size?