API 510 Pressure Vessel Inspection Code: FFS Evaluation of Widely Scattered Pits
Inspectioneering has recently published a blog post titled "API 510 Pressure Vessel Inspection Code: FFS Evaluation of Widely Scattered Pits." Click the link above to read the full article.
API 579-1/ASME FFS-1, Part 6 defines pitting as:
"localized regions of metal loss that can be characterized by a pit diameter on the order of the plate thickness or less, and a pit depth that is less than the plate thickness."
The fitness-for-service (FFS) assessment procedures in Part 6 can be used to evaluate four types of pitting:
Widely scattered pitting that occurs over a significant region of the component
Local thin area (LTA) located in a region of widely scattered pitting
Localized regions of pitting
Pitting confined within a region of a LTA
API 510, 7.4.3 addresses widely scattered pitting by providing an FFS assessment procedure with three different conditions that if met, considers the pits to be widely scattered and may be ignored by the inspector; or if not met, then the pits should be considered as a local thin area and analyzed accordingly.
On this basis, while performing a pressure vessel inspection, an inspector may ignore widely scattered pits if all of the following criteria specified in API 510, 7.4.3 are met.
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