Standards Development

Scope

Fault tree analysis (FTA) identifies and analyses combinations of conditions and factors that cause or can potentially cause or contribute to the occurrence of a defined undesirable outcome, referred to as the "top event". This document describes the (FTA) technique and provides guidance on its application. This includes:–        definition and description of commonly used terms and symbols;–        purpose, applications and limitations of FTs;–        a description of basic concepts and principles;–        a description of the steps involved in scoping, constructing and developing the FT;–        guidance on performing qualitative and quantitative analysis of the FT including discussion of requirements and limitations of the associated mathematical models;–        identification of basic items that should be included in documenting and reporting the FTA;–        how to perform FTA when some of the commonly used assumptions in FTA are not satisfied (e.g., non-coherent FTs, dynamic FTs);–        example applications in support of the above;–        procedures for calculating  dependability measures (unavailability failure frequency and unreliability) for different types of system, with constant or time dependent probabilities  or with non-repaired or repaired faults).In annexes, the document also describes:–        the relationship of FTA with other related techniques such as Reliability Block Diagram analysis (IEC 61078), Failure Mode and Effects Analysis (FMEA) (IEC 60812), Event Tree Analysis (IEC 62502) and Markov techniques (IEC 61165);–        how the importance of various events included in the FT can be established;–        automated fault tree construction;–        mathematical models required for large and more complex FTs;–        numerical examples demonstrating the use of FTs for dependability calculations.