API 571

A specific process or phenomenon that causes degradation of material properties, leading to eventual failure of equipment. Damage mechanisms include corrosion (uniform, localized, galvanic), erosion, fatigue, creep, hydrogen damage, stress corrosion cracking, embrittlement, and other metallurgical or environmental attack modes. API 571 catalogues over 60 damage mechanisms relevant to refining and petrochemical equipment.

A methodology that uses risk assessment to prioritize and plan inspection activities for pressurized and other equipment. RBI combines Probability of Failure (driven by damage mechanisms and equipment condition) with Consequence of Failure (driven by process hazards and safety impact) to rank equipment by risk and allocate inspection resources where they will have the greatest impact on risk reduction.

A numerical modifier in the API 581 RBI methodology that quantifies the increased probability of failure due to specific active damage mechanisms. Damage factors account for the type, rate, and extent of degradation relative to the equipment's design margins. Higher damage factors indicate more aggressive degradation and higher probability of failure. Total damage factor is the sum of individual damage factors for all active mechanisms.

Risk-Based Inspection standard — provides guidance on developing and implementing a risk-based inspection program for fixed equipment in the hydrocarbon and chemical process industries. It defines the framework for assessing probability and consequence of failure to prioritize inspection resources.

Risk-Based Inspection Technology — provides the quantitative methodology for calculating probability of failure (PoF) and consequence of failure (CoF) for pressurized equipment. It includes detailed procedures for determining damage factor, management system factor, generic failure frequency, and consequence areas for toxic, flammable, and environmental releases.

The degree to which an equipment item is vulnerable to a specific damage mechanism, based on material of construction, process conditions (temperature, pressure, chemistry), design features, and operating history. Susceptibility is typically rated as None, Low, Medium, or High, and drives the selection of damage factors and inspection techniques in RBI assessments.