Page 17 - Root Cause Failure Analysis

8 Root Cause Failure Analysis
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.
event
top
Define

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Establish boundaries

7
system
Understand

fault
tree
I
1 Construct - Analyze tree

Take corrective action

Figure 2-2 ljpical fault-tree process.

called the top event, and basic failures or causes, called primary events. Top events
can be broad, all-encompassing system failures or specific component failures.

Fault-tree analysis provides options for performing qualitative and quantitative reli-
ability analysis. It helps the analyst understand system failures deductively and points
out the aspects of a system that are important with respect to the failure of interest.
The analysis provides insight into system behavior.

A fault-tree model graphically and logically presents the various combinations of pos-
sible events occurring in a system that lead to the top event. The term event denotes a
dynamic change of state that occurs in a system element, which includes hardware,
software, human, and environmental factors. A fault event is an abnormal system
state. A nom1 event is expected to occur.

The structure of a fault tree is shown in Figure 2-3. The undesired event appears as
the top event and is linked to more basic fault events by event statements and logic
gates.