Fault Tree Analysis Why do we need fault tree analysis? What is it? Why do we use it? Why this matters to you How it works Bridgestone/Firestone Brief exercise Summary

What Is Fault Tree Analysis? A common tool using graphics and statistics to analyze an event and predict how and how often it will fail Used in engineering and business to aid process and system development

Why Do We Use Fault Tree Analysis? Very easy to understand Effective way to diagram problems in a system Helps to organize possible causes of a problem in the system

Example Of Fault Tree

Is Fault Tree A Tool For You? Does your company have problems in your system or process flow? Does your system work under the worst case scenario? Do external forces effect your system?

Is Fault Tree A Tool For You? Yes!!

How Does It Work? Uses a variety of gates and events to explain the system Uses a top-down approach to its logic End result is at the top of the tree and what leads to that result follows under it

And Gate One of main gates used The output above will occur if the two events below both occur

Or Gate The second main gate used The output above will occur if either of one or more events happens below

Three Main Events Primary Event Intermediate Event Expanded Event

Primary Events Made up of basic, undeveloped, and external events A time in the event where the process or system might fail

Basic Event Nothing is leading up to the event Can be like a machine breaking unexpectedly A circle is used to represent the event in the fault tree

Undeveloped Event Events that don’t have a major effect on the system Also events that there is not enough information about Represented by a diamond in the fault tree

External Event Expected to happen Not considered a fault A house shape in a fault tree

Intermediate Event A combination of multiple different faults Shown by rectangles in the fault tree Sometimes linked by and/or gates

Expanded Event Complex event that needs another fault tree to explain The fault tree for the expanded event is not directly shown in current fault tree Shown by a triangle on the fault tree

Bridgestone Firestone tires Faulty tires on S.U.V.’s caused numerous accidents Officially 148 deaths but estimates up to 250 Mostly involved with the Ford Explorer

Results Of Inquiry Four events that led to faulty tires Design problem in tread Faulty process in Decatur, Illinois Problem with Ford Explorer Customers don’t take proper care of tires

Values Of Fault Tree For Firestone Preventing the error in the first place After the error in the tire was found, finding all the things that caused it Preventing similar problems from happening again

The New Firestone Firestone advertise that they are a changed company Tries to get back old customers

Test Yourself What are the two major kinds of gates? What are the three main events? A basic event is represented by a what? True or False, an undeveloped event has a major impact on the system?

Test Yourself What are the two major kinds of gates? And/Or gates What are the three main events? Primary, Independent, and Undeveloped A basic event is represented by a what? Circle True or False, an undeveloped event has a major impact on the system? False

Summary Of Fault Tree Analysis An important tool Simple to use Graphics make it easy to understand Each event is displayed by a unique shape Helps to prevent and correct errors in the system