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Fault Tree Analysis

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  1. Fault Tree Analysis By Patrick Ackerson

  2. Outline • 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

  3. 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

  4. 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

  5. Example Of Fault Tree

  6. 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?

  7. Is Fault Tree A Tool For You? Yes!!

  8. 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

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

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

  11. Three Main Events • Primary Event • Intermediate Event • Expanded Event

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

  13. 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

  14. 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

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

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

  17. 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

  18. 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

  19. 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

  20. 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

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

  22. 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?

  23. 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

  24. 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

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