Developing Fault Tree
rude-1
lectures.zipLectures/Answers to Fault Tree Example.pdf
Circuit overloads Circuit Breaker Broken brake Fails joint Operator Back-up Drunk not available
Hydraulic Failure
Human Error
Braking Failure Starter Switch Failure
Lectures/Developing Fault Trees.html.zip
Developing Fault Trees.html
Lectures/Discussion-Fault Trees.pdf
Fault Trees
1. Originated by H.A. Watson at Bell Telephone Laboratories in 1962 2. Deductive process that moves from general to specific 3. Combinations and interactions of events 4. After the tree is constructed
A. Qualitative analysis B. Quantitative analysis
5. Limitations of Fault Trees A. Failure to include events – inexperience or oversight B. Assigning valid probabilities to event causes C. Cost of the process
6. Fault Tree symbols:
EVENTS: 4 kinds Fault event Basic Event Normal Event Undeveloped Event
Fault Event – Top or immediate event. For quantitative analysis, it is computed from the information below Basic Event – An event for which there will be no further analysis. Can be a terminus of a branch in the fault tree. Probabilities assigned to basic events. Undeveloped Event – Analyst chooses not to analyze. May or may not be another fault tree concerning that event. Normal Event – It either occurs or does not occur. Sometimes called switch events. LOGIC GATES: 2 kinds: “And” Gate “Or Gate” “And” Gate - All inputs must occur before the output event “Or” Gate – Any one of the input events can cause the output event
Lectures/Fault Trees Example Exercise.pdf
Fault Trees Example…. You have an industrial conveyor machine. The hydraulic system on the conveyor machine is vital to worker safety. If it fails, the results could be catastrophic. The hydraulic system could fail in two ways. The starter switch could fail, or the braking mechanism could fail. The starter switch could fail if the circuit overloads and the circuit breaker fails. The braking mechanism could fail to human error or from a broken brake joint. Human error could occur if the operator is drunk and his backup operator is not available. Diagram this fault tree.
