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Figure 3.8. Fault trees before Cause 4 is moved

Fault trees before Cause 4 is moved (Probability equations omitted). Two trees are shown in this figure: Harmful Event and Benign Failure. The Harmful Event tree progresses from Harmful Event to an OR symbol, which splits in three branches; one branch (right) leads to element labeled Cause #4; the second branch (center) leads to an element labeled Cause #3. Cause numbers 3 and 4 are labeled 'No redundancy'. The third branch (left) leads to AND symbol where the tree again splits in two, leading to pair of elements labeled Cause #1 and Cause #2. The Benign Failure tree begins with element labeled Benign Failure, which splits into three branches at AND symbol, which is labeled 'Multiple redundancies'; the three branches terminate in elements labeled, respectively, Cause #A, Cause #B, and Cause #C.

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Figure 3.9. Fault trees after Cause 4 is moved

Fault trees after Cause 4 is moved (Probability equations omitted). Two trees are shown in this figure: Harmful Event and Benign Failure. The Harmful Event tree progresses from Harmful Event to an OR symbol, which splits in three branches; one branch (right) leads to an element labeled Cause #4, which has been crossed out, and an arrow points from its former location to a new branch in the Benign Failure tree; the second branch (center) leads to an element labeled Cause #3. Cause numbers 3 and 4 are labeled 'No redundancy'. The third branch (left) leads to AND symbol where the tree again splits in two, leading to pair of elements labeled Cause #1 and Cause #2. The Benign Failure tree begins with element labeled Benign Failure, which splits into two branches at an OR symbol. The first (left) branch leads to Cause #4. The second (right) branch leads to AND symbol, which splits into three branches; the three branches terminate in elements labeled, respectively, Cause #A, Cause #B, and Cause #C.

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