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Importance / Sensitivity Analysis |
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Importance / Sensitivity Analysis |
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Importance / Sensitivity Analysis
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Importance / Sensitivity Analysis |
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Importance / Sensitivity Analysis |
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Importance & Sensitivity Analysis can only be performed after MCS analysis, because it uses generated Minimal Cut Sets. Importance analysis results help to select those fault tree events, which contribute most to the system’s unavailability. Sensitivity analysis helps to choose those events, where a relatively small change will lead to relatively large system unavailability changes.
Calculated values for each event are:
| • | Fussell-Vesely importance (FV Imp) |
Fussell - Vesely importance for basic event i FV(i) = Sum of all MCS containing the event i / sum of all MCS
| • | Risk Decrease Factor (RDF) |
Risk Decrease Factor for a basic event i RDF(i) = Sum of all MCS / sum of all MCS taking into account that event i probability is 0.
| • | Fractional Contribution (FC) |
Fractional Contribution for a basic event i FC(i) = 1 – 1/RDF(i)
| • | Risk Increase Factor (RIF) |
Risk Increase Factor for a basic event iRIF(i) = sum of all MCS taking into account that event i probability is 1 / sum of all MCS.
| • | Sensitivity |
Example of the analysis results report:
FTA - Importance & Sensitivity Analysis
Project name: FTA
FTA: RAMC
Top event: RAMC
Q mean=0.807138
N
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Code
|
Occur- rence |
Q mean |
FV Imp. |
FC |
RDF |
RIF |
Sens. high |
Sens. low |
Sensi- tivity |
|---|---|---|---|---|---|---|---|---|---|---|
1 |
ActiveX not registered |
1 |
0.3 |
0.371684 |
0.102405 |
1.11409 |
1.23895 |
1 |
0.732748 |
1.36472 |
2 |
Btrieve files absent |
1 |
0.3 |
0.371684 |
0.102405 |
1.11409 |
1.23895 |
1 |
0.732748 |
1.36472 |
3 |
Btrieve registry record is bad |
1 |
0.03 |
0.0371684 |
0.007390 |
1.00745 |
1.23895 |
0.860821 |
0.80177 |
1.07365 |
4 |
License |
2 |
0.3 |
0.212975 |
0.0496012 |
1.05219 |
1.09756 |
0.88588 |
0.771276 |
1.14859 |
5 |
Plug absent |
1 |
0.3 |
0.111505 |
0.023632 |
1.0242 |
1.05514 |
0.851645 |
0.789971 |
1.07807 |
6 |
Plug driver failure |
1 |
0.3 |
0.111505 |
0.023632 |
1.0242 |
1.05514 |
0.851645 |
0.789971 |
1.07807 |
7 |
RAMC files bad |
1 |
0.3 |
0.371684 |
0.102405 |
1.11409 |
1.23895 |
1 |
0.732748 |
1.36472 |
8 |
RAMC registry records bad |
1 |
0.3 |
0.371684 |
0.102405 |
1.11409 |
1.23895 |
1 |
0.732748 |
1.36472 |