API 510 Fitness for Service Assessment 4 — Questions and Answers
Question 1: According to API 579-1/ASME FFS-1, what is the primary purpose of a Level 1 FFS assessment?
- Perform detailed stress analysis using finite element methods
- Apply conservative screening criteria that can be performed by an inspector in the field (Correct answer)
- Require a full remaining life calculation with creep damage
- Mandate an immediate repair or replacement decision
Correct answer: Apply conservative screening criteria that can be performed by an inspector in the field
Level 1 is the most conservative and simplest assessment level, using screening criteria that inspectors can apply with minimal calculations.
Question 2: When performing a FFS assessment for local thin areas (LTA) using API 579, which parameter is used to characterize the extent of metal loss in the longitudinal direction?
- Remaining thickness ratio (Rt)
- Longitudinal flaw length parameter (λ) (Correct answer)
- Maximum allowable working pressure (MAWP)
- Folias factor (Mt)
Correct answer: Longitudinal flaw length parameter (λ)
The longitudinal flaw length parameter (λ) normalizes the flaw length relative to vessel diameter and wall thickness to characterize LTA extent.
Question 3: In a FFS assessment for hydrogen blistering, which condition would MOST LIKELY require a Level 3 assessment?
- Single blister with diameter less than the minimum dimension criterion
- Blister located away from structural discontinuities with no HIC cracking
- Multiple blisters with through-thickness cracking or Step-Wise Cracking (SWC) (Correct answer)
- Blister elevation less than 10% of the base metal thickness
Correct answer: Multiple blisters with through-thickness cracking or Step-Wise Cracking (SWC)
Multiple blisters exhibiting through-thickness cracking or step-wise cracking indicate severe HIC damage requiring a detailed Level 3 assessment.
Question 4: The remaining strength factor (RSF) concept in API 579 FFS assessments is used to:
- Calculate the corrosion allowance for future inspection intervals
- Compare the strength of the damaged component to the undamaged component (Correct answer)
- Determine the minimum required thickness per the original design code
- Establish the maximum inspection interval before the next shutdown
Correct answer: Compare the strength of the damaged component to the undamaged component
RSF quantifies how much load-carrying capacity remains in a damaged component relative to the undamaged condition.
Question 5: For a weld with a detected planar flaw, which API 579 Part addresses the FFS evaluation methodology?
- Part 4 — General Metal Loss
- Part 5 — Local Metal Loss
- Part 9 — Crack-Like Flaws (Correct answer)
- Part 7 — Hydrogen Blistering
Correct answer: Part 9 — Crack-Like Flaws
API 579 Part 9 covers the FFS assessment methodology for crack-like flaws including weld flaws using fracture mechanics.
Question 6: In a FFS assessment, the term 'future corrosion allowance' (FCA) refers to:
- The original corrosion allowance specified in the design code
- The expected metal loss between the assessment date and the next planned inspection (Correct answer)
- The minimum required thickness for pressure containment per MAWP
- The thickness tolerance allowed by the original fabrication standard
Correct answer: The expected metal loss between the assessment date and the next planned inspection
FCA is the anticipated metal loss from the assessment date to the next planned inspection or end of equipment life.
Question 7: When a FFS assessment results in an RSF below the allowable RSF (RSFa), the recommended course of action is to:
- Accept the equipment for continued operation with no action required
- Reduce the MAWP or repair/retire the component (Correct answer)
- Increase the inspection frequency and continue at full MAWP
- Apply an external coating and defer further evaluation
Correct answer: Reduce the MAWP or repair/retire the component
If RSF < RSFa, the equipment does not meet the FFS acceptance criteria and must either be de-rated to a lower MAWP, repaired, or retired.
API 510 Fitness for Service Assessment 4
According to API 579-1/ASME FFS-1, what is the primary purpose of a Level 1 FFS assessment?