API 510

Piping Inspection Code — provides requirements for the inspection, repair, alteration, and rerating of in-service metallic and fiberglass-reinforced plastic piping systems. It covers inspection practices for maintaining the mechanical integrity of process piping, including determination of corrosion rates, remaining life, and inspection intervals.

Fitness-For-Service standard — provides quantitative engineering assessment procedures for evaluating flaws, damage, and degradation found in pressurized equipment. It covers assessment levels (Level 1 screening through Level 3 detailed analysis) for general metal loss, local thin areas, pitting, blisters, weld misalignment, crack-like flaws, creep damage, and fire damage.

An engineering assessment methodology used to determine whether equipment with identified flaws, damage, or degradation can continue to operate safely and reliably for a defined future period. FFS evaluations quantify the remaining structural capacity of degraded equipment using the procedures in API 579-1/ASME FFS-1, considering the specific type and extent of damage relative to the design margins.

The estimated time from the present until an equipment item reaches a condition where it can no longer perform its intended function safely and must be repaired, replaced, or retired. For static equipment, RUL is typically calculated from the current measured wall thickness, the minimum required thickness, and the corrosion rate. For rotating equipment, RUL may be estimated from degradation models fitted to condition monitoring data.

The wall thickness specified at the time of design and fabrication, before any in-service degradation. Nominal thickness is the starting point for remaining life calculations and is the thickness that should be measured at a CML immediately after construction. It includes the minimum required thickness plus the corrosion allowance plus any manufacturing tolerance.