API 579-1 / ASME FFS-1

Covers — quantitative fitness-for-service assessment of in-service pressure equipment and piping with flaws or damage: general and local metal loss, pitting, blisters/HIC, weld misalignment, crack-like flaws, creep, fatigue, fire damage, dents/gouges, and HTHA, using tiered (Level 1/2/3) methods to set acceptability, MAWP, and remaining life.

Does NOT cover (exclusions) — the following are governed elsewhere:

• The inspection program that finds the flaw → API 570 / 510.
• The repair method once FFS is unfavorable → ASME PCC-2.
• Damage-mechanism background → API RP 571.

FFS-1 quantifies whether a found flaw is acceptable; the inspection code finds it and PCC-2 repairs it.

FFS-1 sets assessment procedures by flaw type and level:

• Assessment Levels — Level 1 (conservative screening), Level 2 (more detailed), Level 3 (advanced FEA/fracture mechanics).
• Flaw-Specific Methods — dedicated parts for metal loss, pitting, crack-like flaws, creep, fatigue, dents, HTHA, etc.
• Outputs — acceptability, reduced MAWP, remaining strength factor, and remaining life.
• Inputs — inspection data, material properties, stresses, and future damage rate.

API 579-1/ASME FFS-1 is the quantitative fitness-for-service standard: when an inspection finds a flaw that exceeds the simple rules of the construction/inspection code, FFS-1 decides whether the equipment can keep operating, at what MAWP, and for how long. It has dedicated methods for metal loss, pitting, crack-like flaws, creep, fatigue, HTHA, dents, and more.

Assessments are tiered — Level 1 conservative screening, Level 2 refined, Level 3 advanced FEA/fracture mechanics — so effort scales with the stakes. It sits between the inspection code (API 570/510, which finds the flaw) and the repair standard (PCC-2, used if FFS is unfavorable).

Engineering Note: An FFS assessment is only as good as its inputs — reliable flaw sizing, correct material toughness, and a defensible future corrosion/damage rate. A favorable Level 1 result on optimistic inputs can be unconservative; escalate the level when the consequence or uncertainty is high.