API 510 Inspection Planning and Scheduling 4 — Questions and Answers
Question 1: Which condition would MOST likely prompt an inspector to specify ultrasonic thickness (UT) scanning rather than spot UT readings in the inspection plan?
- Uniform general corrosion documented in prior inspections
- Localized or pitting corrosion with high variability in prior readings (Correct answer)
- Insulation in good condition with no external corrosion
- A vessel operating below its design pressure
Correct answer: Localized or pitting corrosion with high variability in prior readings
When prior data shows localized or pitting corrosion, scanning covers a larger area to find the minimum thickness rather than relying on spot readings that may miss the worst locations.
Question 2: An API 510 inspection plan should document which of the following?
- Only the inspection date and inspector name
- Inspection scope, methods, locations, acceptance criteria, and responsible personnel (Correct answer)
- Vessel purchase cost and insurance value
- Number of operators assigned to the vessel
Correct answer: Inspection scope, methods, locations, acceptance criteria, and responsible personnel
A complete inspection plan specifies what will be inspected, which NDE methods will be used, where measurements will be taken, acceptance criteria, and who is responsible.
Question 3: When should fitness-for-service (FFS) assessment per API 579 be incorporated into inspection planning?
- For all vessels regardless of condition
- When inspection reveals damage mechanisms or flaws that may challenge fitness of the vessel (Correct answer)
- Only when the vessel is over 25 years old
- Only after a hydrostatic test failure
Correct answer: When inspection reveals damage mechanisms or flaws that may challenge fitness of the vessel
FFS assessment is triggered when inspection findings such as corrosion, cracks, or dents raise questions about whether the vessel can safely continue operation.
Question 4: For vessels subject to stress corrosion cracking (SCC), which NDE method should be emphasized in the inspection plan?
- Visual inspection only
- Surface examination techniques such as wet fluorescent magnetic particle or liquid penetrant testing (Correct answer)
- Hydrostatic pressure testing only
- Radiographic testing of shell plate
Correct answer: Surface examination techniques such as wet fluorescent magnetic particle or liquid penetrant testing
SCC produces tight surface-breaking cracks best detected by wet fluorescent magnetic particle (WFMT) on ferromagnetic materials or liquid penetrant testing (PT) on non-ferromagnetic surfaces.
Question 5: What action is required under API 510 if actual corrosion is found to exceed the corrosion rate used in the current inspection interval calculation?
- Continue on the existing inspection schedule until the next planned internal inspection
- Recalculate remaining life using the updated rate and adjust the next inspection date accordingly (Correct answer)
- Immediately shut down the vessel for emergency replacement
- Notify only the plant manager, with no documentation required
Correct answer: Recalculate remaining life using the updated rate and adjust the next inspection date accordingly
When actual corrosion exceeds the assumed rate, remaining life must be recalculated and the inspection schedule revised to reflect the more aggressive deterioration.
Question 6: During inspection planning for a vessel with external insulation, which damage mechanism requires special attention?
- High-temperature hydrogen attack
- Corrosion under insulation (CUI) (Correct answer)
- Hydrogen embrittlement
- Graphitic corrosion
Correct answer: Corrosion under insulation (CUI)
Corrosion under insulation (CUI) occurs when moisture penetrates insulation and attacks the external vessel surface, making it a priority concern in planning inspections of insulated vessels.
Question 7: Which statement best describes the role of process unit history in API 510 inspection planning?
- It is irrelevant if the vessel has passed its last hydrostatic test
- Process upsets, temperature excursions, and feedstock changes can alter damage rates and should be incorporated into planning (Correct answer)
- Only the nameplate data matters for scheduling
- Process history is only relevant for piping, not pressure vessels
Correct answer: Process upsets, temperature excursions, and feedstock changes can alter damage rates and should be incorporated into planning
Changes in process conditions, such as feedstock composition or temperature excursions, can accelerate or introduce new damage mechanisms that must be factored into the inspection plan.
API 510 Inspection Planning and Scheduling 4
Which condition would MOST likely prompt an inspector to specify ultrasonic thickness (UT) scanning rather than spot UT readings in the inspection plan?