RBI 581 is an approach to qualify and quantify risks. It involves detailed calculation methods to determine an inspection plan. The output of the API 581 RBI assessment is the same as the S-RBI output: the inspection frequencies or intervals, the scope of work, and priorities.
Risk = Probability x Consequence
Risk = PoF x CoF
Risk = [gff Df(t) FMS] x CoF
The implemented Consequence of Failure (CoF) calculation applies to all Damage Factors. Relevant calculation tables can be viewed in the IMS settings.
The Probability of Failure (PoF) is computed from: gff Df(t) FMS, where gff is the generic failure frequency (industry failure data, tabulated in API 581 Part 2), FMS is the Management Systems Factor reflecting the quality of your mechanical integrity program, and Df(t) is the Damage Factor as a function of time. FMS can be defined at Site/Plant/Unit level in Settings.
The Risk Calculation Method — either ISO Risk Plot or API RBI Matrix (balanced or unbalanced) — can be selected at Site/Plant/Unit level. For the RBI Matrix, two Criticality Targets can be set: the Risk Target Criteria (set at Site/Plant/Unit level) and the Legal/Local Inspection Interval (LII) target (set in the RBI assessment). For the ISO Risk method, the Area Acceptable Risk Target and Economic Acceptable Risk Target are set at Site/Plant/Unit level, and the LII target is set in the RBI assessment. IMS iterates the Age until the Criticality Target is exceeded, resulting in a Maximum Inspection Interval (MII).