American Petroleum Institute

Risk-Based Inspection Technology - Second Edition
 N RP 581

Annotation

Purpose

This recommended practice provides quantitative procedures to establish an inspection program using riskbased methods for pressurized fixed equipment including pressure vessel, piping, tankage, pressure relief devices, and heat exchanger tube bundles. API RP 580 [1] provides guidance on developing a risk-based inspection program for fixed equipment in the refining and petrochemical, and chemical process plants. The intent of these publications is for API RP 580 to introduce the principles and present minimum general guidelines for RBI while this recommended practice provides quantitative calculation methods to determine an inspection plan.

Introduction

The calculation of risk in the Risk-Based Inspection (API RBI) methodology involves the determination of a probability of failure combined with the consequence of failure. Failure in API RBI is defined as a loss of containment from the pressure boundary resulting in leakage to the atmosphere or rupture of a pressurized component. As damage accumulates in a pressurized component during in-service operation the risk increases. At some point, a risk tolerance or risk target is exceeded and an inspection is recommended of sufficient effectiveness to better quantify the damage state of the component. The inspection action itself does not reduce the risk; however, it does reduce uncertainty thereby allowing better quantification of the damage present in the component.

Risk Management

In most situations, once risks have been identified, alternate opportunities are available to reduce them. However, nearly all major commercial losses are the result of a failure to understand or manage risk.