Probability of Failure(PoF)

A measure of the impact resulting from an equipment failure, encompassing safety (personnel injury/fatality), environmental (release to atmosphere/ground/water), production (lost throughput and business interruption), and equipment (repair/replacement cost). CoF is evaluated based on the worst credible release scenario, considering fluid properties, operating conditions, detection and isolation systems, and the surrounding environment.

A two-dimensional grid that combines Probability of Failure (PoF) on one axis and Consequence of Failure (CoF) on the other to produce a visual risk ranking. The matrix divides risk into categories (typically A through E or Low/Medium/High/Very High/Extreme) that determine inspection priority, interval, and strategy. Risk matrices provide a standardized framework for comparing and prioritizing risks across diverse equipment populations.

A categorical classification (typically A through E) derived from the risk matrix that represents the combined probability and consequence of failure for an equipment item. Risk ranking determines the urgency and extent of inspection, monitoring, and maintenance activities. Rankings are typically: A (lowest risk) through E (highest risk), each with prescribed inspection strategies and maximum interval limits.

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.

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.

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.