Fault Tree Analysis

Fault Tree Analysis - FTA
a website created by Relex Software Corporation

This website provides information about fault tree analysis (FTA) and how it relates to reliability and maintainability (RAM) software and analyses.

What is a Fault Tree?

Fault Tree analysis is one of the most widely-used methods in system reliability analysis. It is a deductive procedure for determining the various combinations of hardware and software failures, and human errors that could result in the occurrence of specified undesired events (referred to as top events) at the system level. A deductive analysis begins with a general conclusion, then attempts to determine the specific causes of this conclusion. This is often described as a "top down" approach.

Click here to see an example screen of a fault tree. (Click your browser's "Back" button to return.)

The main purpose of fault tree analysis is to evaluate the probability of the top event using analytical or statistical methods. These calculations involve system quantitative reliability and maintainability information, such as failure probability, failure rate, or repair rate. FTA can provide useful information concerning the likelihood of a failure and the means by which such a failure could occur. Efforts to improve system safety and reliability can be focused and refined using the results of the FTA.

Fault Tree Gates

A gate is used to describe the relationship between the input and output events in a fault tree. Fault trees can have several different kinds of gates. Two kinds of gates are described and shown below:

Description	Picture	Truth Table
AND Gate. The AND gate indicates that the output occurs if and only if all of the input events occur.		Input A	Input B	Output
		T T F F	T F T F	T F F F
OR Gate. The OR gate indicates that the output occurs if and only if at least one of the input events occur.		Input A	Input B	Output
		T T F F	T F T F	T T T F

Using Fault Tree with Reliability Software

Relex Software Corporation produces software that enables users to easily design fault trees and perform FTA quickly and easily. Relex Software is a leader in R&M (Reliability and Maintainability) software analysis tools. We specialize in software, training courses, and seminars covering all aspects of reliability engineering. Our products are used by thousands of engineers worldwide in a variety of businesses.

For More Information

Please visit the Links page for more online information about the Relex Software visual reliability software modules, and about FTA in general.

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