---
title: "RBI 581 Overview"
slug: "api-581-overview"
description: "API RBI 581 quantifies risks using detailed calculations for inspection plans, determining frequencies, scopes, and priorities for effective risk management."
updated: 2026-10-27T23:11:45Z
published: 2026-10-27T23:11:45Z
canonical: "ims-handbook.cenosco.com/api-581-overview"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://ims-handbook.cenosco.com/llms.txt
> Use this file to discover all available pages before exploring further.

# RBI 581 Overview

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](/v414/docs/setting-up-for-rbi-581-analyses#setting-up-the-management-systems-factor-fms).

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](/v414/docs/setting-up-for-rbi-581-analyses#setting-up-the-management-systems-factor-fms).

The Risk Calculation Method — either ISO Risk Plot or API RBI Matrix (balanced or unbalanced) — can be [selected](/v414/docs/setting-up-for-rbi-581-analyses#specifying-which-risk-calculation-method-to-use) 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).