API 510 Fundamentals & Core Concepts 4 — Questions and Answers
Question 1: API 510 references API 579-1/ASME FFS-1 for fitness-for-service evaluations. Which level of FFS assessment is the most rigorous and detailed?
- Level 1 — screening using conservative tables
- Level 2 — more detailed analysis using code-based procedures
- Level 3 — detailed analysis often requiring advanced numerical methods or specialist review (Correct answer)
- Level 4 — reserved for catastrophic damage only
Correct answer: Level 3 — detailed analysis often requiring advanced numerical methods or specialist review
Level 3 FFS assessments are the most rigorous, typically requiring advanced methods such as finite element analysis or specialist engineering review.
Question 2: Under API 510, what action is required before a pressure vessel can be returned to service after an internal inspection?
- The vessel must receive a new National Board stamp
- The authorized inspector must review findings and confirm the vessel is fit for continued service (Correct answer)
- A pressure test at 1.5× MAWP is always mandatory
- The original designer must recertify the vessel
Correct answer: The authorized inspector must review findings and confirm the vessel is fit for continued service
The authorized inspector reviews inspection findings and must confirm fitness for service before the vessel is returned to operation.
Question 3: Which of the following best describes 'corrosion under insulation' (CUI) as it applies to API 510 inspection planning?
- External corrosion occurring beneath thermal insulation, often unseen and potentially severe (Correct answer)
- Internal corrosion caused by process fluids attacking insulated nozzles
- Crevice corrosion inside a vessel shell at support saddles
- Galvanic corrosion between dissimilar metals in heat exchanger bundles
Correct answer: External corrosion occurring beneath thermal insulation, often unseen and potentially severe
CUI is external corrosion that develops beneath insulation where moisture becomes trapped, making it a hidden and potentially significant degradation mechanism.
Question 4: According to API 510, the inspection interval for an on-stream (external) inspection of a pressure vessel is based primarily on what?
- The vessel's original construction date
- Half the remaining corrosion life or 10 years, whichever is less, unless RBI is used (Correct answer)
- A fixed 5-year government-mandated schedule
- The frequency of process upsets in the prior year
Correct answer: Half the remaining corrosion life or 10 years, whichever is less, unless RBI is used
API 510 limits the external inspection interval to half the remaining corrosion life or 10 years maximum, unless a risk-based inspection (RBI) program is in place.
Question 5: What does the term 'nominal thickness' mean in the context of API 510 pressure vessel inspection?
- The measured thickness at the thinnest point found during inspection
- The thickness specified on the engineering drawings or mill order, not accounting for undertolerance (Correct answer)
- The minimum required thickness calculated from the pressure formula
- The thickness after subtracting the full corrosion allowance
Correct answer: The thickness specified on the engineering drawings or mill order, not accounting for undertolerance
Nominal thickness is the design or specified thickness on drawings, before mill undertolerance or corrosion is subtracted.
Question 6: In API 510, a 'repair' to a pressure vessel is distinguished from an 'alteration' primarily by which criterion?
- Cost — repairs under $10,000 are not alterations
- An alteration changes the vessel's design pressure, temperature, or capacity; a repair restores it to its original condition (Correct answer)
- Any work requiring welding is classified as an alteration
- Repairs are done by the owner; alterations require a third-party contractor
Correct answer: An alteration changes the vessel's design pressure, temperature, or capacity; a repair restores it to its original condition
An alteration changes design parameters such as MAWP, temperature rating, or capacity; a repair simply restores the vessel to its previous acceptable condition.
Question 7: Which ASME code section is most commonly referenced in API 510 for the design and construction of unfired pressure vessels?
- ASME Section I — Power Boilers
- ASME Section VIII — Pressure Vessels (Correct answer)
- ASME Section IX — Welding Qualifications
- ASME Section V — Nondestructive Examination
Correct answer: ASME Section VIII — Pressure Vessels
ASME Section VIII, Division 1 and Division 2, governs the design and construction of unfired pressure vessels and is the primary construction code referenced by API 510.
API 510 Fundamentals & Core Concepts 4
API 510 references API 579-1/ASME FFS-1 for fitness-for-service evaluations.
Which level of FFS assessment is the most rigorous and detailed?