1. 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

2. 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
Fault Tree Analysis is a common tool in business and engineering. It uses simple graphics to help show how a system will fail. Percentages can be added to the graphic to show the chances for an event to take place.

3. 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
The graphic design allows the fault tree to be easily explained and understood by anyone in the situation that is using it. Fault tree analysis also provides a unique way of dealing with problems in a process or system flow.

4. Example Of Fault Tree
Picture provided by Relax Software Corporation.

5. 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?
Fault tree analysis can be useful if your company answers yes to any or all of these questions. Fault tree will help you locate problem areas in your system. It will also show how other events would effect the system and cause it to fail. It will even show you if your system can withstand everything going wrong at once. Overall fault tree analysis will help your company be prepared for any thing that could effect your system.

6. Is Fault Tree A Tool For You?
Yes!!
Fault tree analysis can be used for anyone answering yes in the previous slide. It is easy enough to understand that it can be used in all departments. The information can then be shared with people all through the company to make the system run smoothly.

7. 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
The gates and events range from specific types of events to and/or gates. Gates are used to progress from one event to another. Top-down approach is when the end is at the top and the tree works its way up from the bottom to get to the end event.

8. And Gate One of main gates used
The output above will occur if the two events below both occur
An example of an And gate is that if you are pay your taxes on time and don’t cheat on them the I.R.S. will not fine you.

9. Or Gate The second main gate used
The output above will occur if either of one or more events happens below
An example of an Or gate would be if you are late on your taxes or you cheat on your taxes the I.R.S. will fine you. Or gates and And gates can be used with each other in the tree.

10. Three Main Events Primary Event Intermediate Event Expanded Event
Primary events are broken down into 3 other types of events. Intermediate events are made of primary events.

11. Primary Events Made up of basic, undeveloped, and external events
A time in the event where the process or system might fail
An example of a primary event is when you put a MAC card into a MAC machine you might have the wrong password so you wouldn’t be able to continue if you did.

12. 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
A basic event is something like a truck breaks down and is unable to get the necessary parts to the plant on time.

13. 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
An example of an undeveloped event is when the product that a company is making gets randomly inspected. This could be used to just show that its happening but it really doesn’t effect the process of what the company is making.

14. External Event Expected to happen Not considered a fault
A house shape in a fault tree
An example of an external event would be routine maintenance every week at the same time every week.

15. Intermediate Event A combination of multiple different faults
Shown by rectangles in the fault tree
Sometimes linked by and/or gates
An example of an intermediate event would be when a car is ran for 10,000 miles and the oil is not changed the engine would blow up. The engine blowing up is the intermediate event.

16. 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
An example of an expanded event is when the process is slowed by a late part. The only event that would show up in the fault tree would be that the part was late. The additional tree would contain information like the company that delivers the part used an old truck and the truck was not maintained and this caused it to break down.

17. 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
Last year Bridgestone Firestone tires had a defect where the tread was separating causing many accidents all over the country and the world. The tire was made for sports utility vehicles and the problem occurred most often in Ford Explorers. Bridgestone had to issue a recall on 14.4 million tires. Ford and Firestone were both investigated by the National Transportation Safety Board and Congress. This would have been a perfect opportunity to use fault tree analysis to understand why these tires failed and how they could correct the problem.

18. 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
Firestone came up with these four causes of the faulty tire. It blamed a design flaw that they corrected already, an error in the process at a plant in Illinois that was unique to that plant. Ford’s recommended tire pressure and their improper weight distribution. Firestone also blamed customers for not providing proper maintenance on the tires.

19. 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
Firestone could have made a fault tree for the process that developed the tire. There it would have found that the plant in Illinois had a faulty process in attaching the rubber to the steel belts in the tire. The process at the Illinois plant would be an expanded event. Firestone would have also noticed that with the combination of the error in the Illinois process and Ford’s recommended tire pressure it could cause the tread separation.

20. The New Firestone Firestone advertise that they are a changed company
Tries to get back old customers
Once you lose a customer its almost impossible to get them back. But Firestone still tried to repair all the damage to their ability to market their product. By using fault tree analysis this problem might have been adverted.

21. 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?

22. 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

23. 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
Fault tree analysis is an important tool for anyone in business are engineering. Its graphics make it simple to use and its easy enough to understand that people company wide can benefit from it. Using circles rectangles and other shapes to represent the different events makes it universal so it can be understood by people even outside the company. Fault tree is also a good problem solver and preventer.