API 510 Inspection Techniques & Nondestructive Testing 2 — Questions and Answers
Question 1: When performing ultrasonic thickness measurements on a vessel with internal corrosion, which scanning pattern best characterizes the corrosion profile?
- Single-point measurement at the thinnest visible location
- Grid scanning at regular intervals across the affected area (Correct answer)
- Scanning only along weld seams adjacent to the corrosion
- Random spot checks at inspector-selected locations
Correct answer: Grid scanning at regular intervals across the affected area
Grid scanning at regular intervals provides a systematic map of metal loss, identifying minimum thickness and corrosion patterns across the affected area.
Question 2: Magnetic particle testing (MT) is limited in its application to pressure vessels primarily because it:
- Cannot detect surface-breaking discontinuities
- Is only applicable to ferromagnetic materials (Correct answer)
- Requires removal of all coatings regardless of thickness
- Cannot be used on curved surfaces
Correct answer: Is only applicable to ferromagnetic materials
MT relies on magnetic flux leakage and is therefore restricted to ferromagnetic materials such as carbon steel, excluding austenitic stainless steels and nonferrous alloys.
Question 3: During a liquid penetrant test (PT), what is the purpose of the developer?
- To clean the surface before penetrant application
- To draw the penetrant back out of discontinuities for visual detection (Correct answer)
- To neutralize the penetrant after the dwell time
- To increase the sensitivity of the penetrant to fine cracks
Correct answer: To draw the penetrant back out of discontinuities for visual detection
The developer blots penetrant out of discontinuities through capillary action, creating a visible indication against the contrasting background.
Question 4: According to API 510, when is a Thickness Measurement Location (TML) plan most critical?
- Only when a vessel is newly placed into service
- Whenever corrosion allowance has been fully consumed
- As part of setting up an inspection program to track corrosion rates over time (Correct answer)
- Only prior to a fitness-for-service evaluation
Correct answer: As part of setting up an inspection program to track corrosion rates over time
TML plans are essential for establishing baseline thickness readings and tracking corrosion rates over successive inspections to predict remaining life.
Question 5: Radiographic testing (RT) of a pressure vessel weld reveals a linear indication parallel to the weld axis. This is most likely:
- Porosity cluster
- Incomplete fusion or lack of penetration (Correct answer)
- Tungsten inclusion
- Burn-through
Correct answer: Incomplete fusion or lack of penetration
Linear indications aligned with the weld axis are characteristic of incomplete fusion or lack of penetration, which are planar discontinuities that appear as straight dark lines on radiographs.
Question 6: Acoustic emission testing (AET) is best suited for which inspection scenario on pressure vessels?
- Detecting existing small pits on internal surfaces
- Monitoring active crack growth during a pressure test (Correct answer)
- Measuring precise wall thickness in corroded areas
- Identifying hydrogen blistering under insulation
Correct answer: Monitoring active crack growth during a pressure test
AET detects the elastic waves released by active flaw growth, making it ideal for monitoring crack propagation in real time during pressurization.
Question 7: When using shear wave ultrasonic testing to inspect a pressure vessel weld, the sound beam angle is selected primarily to:
- Maximize penetration depth into thick-walled vessels
- Direct the beam perpendicular to the expected flaw orientation (Correct answer)
- Reduce attenuation losses in fine-grained materials
- Comply with radiographic equivalency requirements
Correct answer: Direct the beam perpendicular to the expected flaw orientation
The beam angle is chosen so the sound strikes the most probable flaw orientation (typically perpendicular to it) to achieve maximum reflectivity and detection sensitivity.
API 510 Inspection Techniques & Nondestructive Testing 2
When performing ultrasonic thickness measurements on a vessel with internal corrosion, which scanning pattern best characterizes the corrosion profile?