This document provides background information on damage that can occur to equipment in the refining process. It is intended to supplement Risk Based Inspection (RP 580 and Publ. 581) and Fitness-for-Service (RP 579) technologies developed in recent years by API to manage existing refining equipment integrity. It is also an excellent reference for inspection, operations, and maintenance personnel. API RP 571 covers over 60 damage mechanisms. Each write-up consists of a general description of the damage, susceptible materials of construction, critical factors, inspection method selection guidelines, and control measures. Wherever possible, pictures are included and references are provided for each mechanism. In addition, generic process flow diagrams have been included that contain a summary of the major damage mechanism expected for typical refinery process units.