Inspectioneering Journal

API RP 581 Risk-based Inspection Technology Demonstrating the Technology Through a Worked Example Problem

Part 1 of 3

By Lynne Kaley, Director of Reliability Strategy at Pinnacle. This article appears in the January/February 2009 issue of Inspectioneering Journal.
This article is part 1 of a 3-part series.
Part 1 | Part 2 | Part 3

Editor's note: This article provides a unique opportunity to guide the reader through API RBI quantitative calculations per API RP 581, Second Edition, September 2008, using real data. The author guides you step by step from input data to final answers including, probability of failure, consequence of failure, financial and risk return and metrics usage, and inspection planning. This article will help those who are seriously interested and invested in RBI to better understand the importance of using a sound technical basis for making critical decisions. This grows increasingly important as the infrastructure ages and tougher decisions need to be made. The type of equipment and fluids used in these examples are typical of those found in the petrochemical and oil & gas industries.

It is important to keep in mind that API RBI RP 581 is an industry ANSI consensus document created by an ANSI accredited organization.

Keep in mind that information from this article (Part 1) will be used in subsequent parts of
this series. Parts 2 and 3 will cover:

  • Consequence of Failure
    • Calculation of release Phase
    • Determination of Release Hole Size Selection
    • Calculation of Release Rate
    • Estimate the Fluid Inventory Available for Release
    • Determining the Release Type
    • Estimate Impact of Detection and Isolation Systems on Release Magnitude
    • Determining Flammable and Explosive Consequence
    • Determining Financial Consequence
    • Component Damage Cost
    • Damage cost to Surrounding Equipment and Affected Area
    • Business Interruption Costs
    • Potential Injury Cost
    • Environmental Cleanup Cost
    • Total Financial Consequence
  • Risk Analysis — Determination of Risk
  • Inspection Planning
  • Future Development Work


The Joint Industry Project for Risk-Based Inspection (RBI JIP) was initiated and managed by API within the refining and petrochemical industry in 1992. The work from the JIP resulted in two publications, API 580 Risk-Based Inspection released in 2002 and API 581 Base Resource Document – Risk-Based Inspection originally released in 1996. The concept behind these publications was for API 580 to introduce the principles and present minimum general guidelines for RBI while API 581 was to provide quantitative RBI methods. The API RBI JIP has made major advances in the technology since the original publication of these documents and released the second edition of API 581 - Recommended Practice for Risk-Based Inspection Technology in September 2008. The second edition is a three volume set, Part 1 – Inspection Planning Using API RBI Technology, Part 2 – Probability of Failure in API RBI, and Part 3 – Consequence Modeling in API RBI. This paper provides a step-by-step worked example that demonstrates the technology documented in API 581, Second Edition.

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