Fault and Event Tree Analysis Flashcards
Event Trees use _____ logic because they look at the initiating event and consider the impact on _____.
Event Trees use forward logic because they look at the initiating event and consider the impact on sequential events.
(The left to right looking graph)
Fault Trees use _____ logic because they start with the top event which is not the ______, but rather the ______ and considers what combination of events lead to that point.
Fault Trees use backwards logic because they start with the top event which is not the initiator, but rather the unwanted consequence and considers what combination of events lead to that point.
Failure Modes and Effects Analysis (FMEA) are another tool used at the _____ stage of a reliability assessment.
This is ______ than fault tree analysis but can only assess ______ of a component failure.
Failure Modes and Effects Analysis (FMEA) are another tool used at the preliminary stage of a reliability assessment.
This is easier than fault tree analysis but can only assess local effects of a component failure.
(FTA in comparison can determine multiple failures which lead to the same top event).
Critically, Event trees model the evolution of a system ____.
Fault trees offer a ____ of a system.
Critically, Event trees model the evolution of a system through time.
Fault trees offer a static view of a system.
The three boundaries which can describe the contents of Fault Trees include:
1)
2)
3)
1) Internal (Things included in the fault tree)
2) External (Things omitted from the fault tree)
3) Temporal (The FT assumes relationship between events doesn’t change with time)
Primary Failure is the failure of a component while it _________.
Primary Failure is the failure of a component while it carried out a function it was supposed to fill.
Secondary Failure is the failure of a component _________.
Secondary Failure is the failure of a component outside of its normal operating parameters.
Command Failure is when a component has _________.
Command Failure is when a component has not been given an instruction to operate under the normal expected conditions.
What does “No gate, no connections” mean?
“No gate, no connections” says you should fully describe each logic gate in fault trees.
What does “No miracles” mean?
“No miracles” discourages us from flooding the fault tree with extremely unlikely scenarios to keep the fault tree coherent.
Complete the Equations which are used to reduce minimal path and cut set equations: A.A = A+A = A+(A.B) = A+(B.C) =
A.A = A A+A = A A+(A.B) = A A+(B.C) = (A+B).(A+C)
The Cut Set representation is obtained when we _______ to obtain an expression for the top event in a fault tree.
The Cut Set representation is obtained when we multiply out brackets to obtain an expression for the top event in a fault tree.
Give 4 points about Minimal Cut Sets
- Cannot be further reduced. • Tells us the minimum combination of events to lead to the top event.
- A Qualitative tool which focuses on common mode failure impacts and help avoid single point failures.
- A Quantitative tool which determines the probability of the top event and rank the importance of different sub-systems or events.
The Path Set is a collection of events whose ______ guarantees that the top event ______.
The Path Set is a collection of events whose non-occurrence guarantees that the top event won’t occur.
What is “asymptotic unavailability”.
Probability might change with time.
Typically, we accept an average value to represent the probability of the top event at any “random” point in time.
We call this, the mean or asymptotic unavailability.
