Category
Inspection & Process Safety
Subcategory
Damage Mechanisms
Applicable standards
5
Issuing bodies
1
Description
Catalog of damage mechanisms in refining & petrochemical industries.
Applicable Standards (5)
API — 5 standards
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 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 580
Risk-Based Inspection
Recommended practice for RBI program development.
Key requirements (8)
- Risk-Based Inspection (RBI) framework — qualitative, semi-quantitative, quantitative.
- Risk = POF (probability of failure) × COF (consequence of failure).
- POF drivers: damage mechanism, corrosion rate, inspection effectiveness.
- COF drivers: flammable inventory, toxic release area, business interruption.
- Risk matrix typical: 5×5, with 'high' risk items getting tightest inspection intervals.
- Inspection interval typically capped at one-half remaining life by API 510/570/653.
- Re-evaluate RBI: every 5 years OR after significant change.
- Companion API 581 provides quantitative methodology and damage factor tables.
API 581
Risk-Based Inspection Methodology
Quantitative RBI calculation methodology — POF, COF, risk ranking, inspection planning.
Key requirements (7)
- Quantitative RBI methodology — damage factor approach.
- Damage factor (DF) by mechanism: thinning, SCC, HTHA, brittle fracture, fatigue, etc.
- Generic failure frequency (gff) baseline: typically 4×10⁻⁵/yr leak frequency.
- Adjusted POF = gff × DF × FMS (management systems factor).
- COF: area-based (ft²) for flammable, dispersion modeling for toxic.
- Inspection effectiveness: A (highly effective) to E (no effectiveness) — degrades DF.
- Re-inspection date driven by acceptable risk threshold (often 5×10⁻⁴/yr).
API 572
Inspection Practices for Pressure Vessels
Companion to API 510 — practical inspection methods.
Key requirements (8)
- Inspection practices for pressure vessels (companion to API 510).
- External inspection minimum: every 5 years.
- Internal inspection minimum: every 10 years (or one-half remaining corrosion allowance life).
- On-stream UT inspection acceptable in lieu of internal in many cases.
- Damage mechanisms reference: API 571 (HIC, SOHIC, polythionic SCC, CUI, HTHA).
- TML (Thickness Measurement Location) selection on injection points, dead legs, mixing zones.
- RBI (API 580/581) may extend interval based on risk assessment.
- WFMT, PAUT, AUBT for high-priority weld inspection.