Chapter 3 System Analysis Fault Tree Analysis Marvin Rausand Department of Production and Quality Engineering Norwegian University of Science and Technology marvin.rausand@ntnu.no

			Introduction
Introduction
What is...? History Main steps Preparation Construction
Assessment Quantification Input Data

What is fault tree analysis?

1. Fault tree analysis (FTA) is a top-down approach to failure

analysis, starting with a potential undesirable event (accident) called a TOP event, and then determining all the ways it can happen.

1. The analysis proceeds by determining how the TOP event can

be caused by individual or combined lower level failures or events.

1. The causes of the TOP event are connected through logic

gates

1. In this book we only consider AND-gates and OR-gates
2. FTA is the most commonly used technique for causal analysis

in risk and reliability studies.

1. FTA was first used by Bell Telephone Laboratories in

connection with the safety analysis of the Minuteman missile launch control system in 1962

1. Technique improved by Boeing Company
2. Extensively used and extended during the Reactor safety

study (WASH 1400)

Preparation for FTA

Boundary conditions

Introduction What is...? History Main steps Preparation Construction Assessment Quantification Input Data

Introduction			Fault tree construction
Construction
Construction Symbols Example Assessment Quantification Input Data

Fault tree construction

U Define the TOP event in a clear and unambiguous way. Should always answer: What e.g., Fire Where e.g., in the process oxidation reactor When e.g., during normal operation U What are the immediate, necessary, and sufficient events and conditions causing the TOP event? U Connect via AND- or OR-gate U Proceed in this way to an appropriate level (= basic events) U Appropriate level: + Independent basic events + Events for which we have failure data

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