Transcript Fault Tree Analysis Basics.ppt

Outline
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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
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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
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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
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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
Bibliography
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Bridgestone/Firestone, “Firestone Homepage,”
19992000, www.firestone.com
“Firestone Facts,” www.firestone-facts.com
Foster, S. Thomas, Managing Quality: An Integrated
(Upper Saddle River, NJ: PrenticeHall Inc. 2001)
Garsten, Ed, “Bridgestone/Firestone says its found
its dig for cause of tire failure,”Dec
12,2000,
http://www.cnn.com/2000/US/12/20/brid
gestone.firestone/index.html
Relex Software Company, “Fault Tree Analysis,”
tree.com
Approach,
answers in
www.fault-