Category
Inspection & Process Safety
Subcategory
Fitness for Service
Applicable standards
5
Issuing bodies
1
Description
Fitness-for-service assessment for in-service damaged equipment.
Applicable Standards (5)
API — 5 standards
API 579-1 / ASME FFS-1
Fitness-for-Service
Quantitative engineering assessment of equipment with flaws (corrosion, cracks, dents, blisters, fire damage, creep, etc.) for continued service.
Key requirements (7)
- Fitness-For-Service standard, jointly with ASME (FFS-1).
- Three assessment levels: 1 (screening), 2 (detailed analytical), 3 (advanced FEA / fracture mechanics).
- Part 4: General metal loss; Part 5: Local metal loss; Part 6: Pitting.
- Part 7: HIC and SOHIC; Part 8: Weld misalignment; Part 9: Crack-like flaws.
- Part 10: Creep; Part 11: Fire damage; Part 12: Dents and gouges; Part 13: Laminations.
- RSF (Remaining Strength Factor) method for general metal loss; RSF ≥ 0.90 typical screening.
- Companion to API 510, 570, 653 for repair-vs-replace decisions.
API 571
Damage Mechanisms Affecting Fixed Equipment in the Refining Industry
Catalog of ~70 damage mechanisms (corrosion, cracking, metallurgical, mechanical, environmental).
Key requirements (5)
- Catalog of >70 damage mechanisms in refining and petrochemical service.
- For each mechanism: description, materials affected, factors, appearance, prevention/mitigation.
- Examples: high-temp H2S corrosion, naphthenic acid corrosion, polythionic acid SCC, CUI, MIC.
- Hydrogen damage: HTHA per Nelson curves (now revised post-Tesoro 2010 incident).
- Used as input to RBI (API 580/581) and inspection planning.
API 510
Pressure Vessel Inspection Code: In-service Inspection, Rating, Repair, and Alteration
In-service inspection, repair, alteration and re-rating of pressure vessels.
Key requirements (8)
- Applies to in-service pressure vessels covered originally by ASME VIII or other recognized code.
- Inspection intervals: external ≤ 5 years, internal ≤ 10 years OR ½ remaining life — whichever is less.
- On-stream UT inspection can replace internal at user's choice if conditions permit.
- Authorized Inspector (AI) certification required for inspection signoff (API ICP).
- Repair/alteration must follow original construction code; reratings allowed via re-calculation + hydrotest waiver if conditions met.
- RBI per API 580/581 may justify extended intervals beyond default limits.
- Damage mechanisms reference: API 571.
- Fitness-For-Service per API 579 when defects exceed acceptance limits.
API 570
Piping Inspection Code
In-service inspection, rating, repair and alteration of process piping.
Key requirements (7)
- Applies to in-service process piping (B31.3 scope typical).
- Piping classified Class 1 (severe), 2 (most), 3 (less severe) by service.
- Thickness inspection intervals: Class 1 ≤ 5 yr, Class 2 ≤ 10 yr, Class 3 ≤ 10 yr (or ½ life).
- External inspection: Class 1/2 ≤ 5 yr, Class 3 ≤ 10 yr.
- CUI inspection mandatory in -12 °C to 175 °C range for insulated CS piping.
- Injection points and dead legs flagged as high-priority TMLs.
- Authorized Piping Inspector (API 570 ICP) certification required.
API 653
Tank Inspection, Repair, Alteration, and Reconstruction
In-service inspection and repair of API 650 and 12C tanks.
Key requirements (7)
- Applies to API 650 / API 12C atmospheric storage tanks in service.
- External inspection ≤ 5 years; internal ≤ 10 years (extendable via RBI to 15–20 yr).
- Bottom MFL/UT scanning during internal inspection — quantifies underside corrosion.
- Settlement survey at intervals (cosine-curve fit, edge settlement criteria).
- Reconstruction: hydrotest required after major shell replacement.
- Authorized Tank Inspector (API 653 ICP) required.
- Repairs categorized as 'Major Alteration', 'Repair' or 'Routine Maintenance' with different documentation.