Section A Flashcards
Rare event approximation
First terms only
Top event failure probability
- full inclusion exclusion
- rare event approximation
- lower bound ( first terms - (second terms combo)
- upper bound
- minimal cut set approximation (1-((1-cut 1)(1-cut2)etc))
q = unavailability, failure rate , F
= time * failure rate (if given REVEALED FAILURE)
Laws
- X+ X.Y=X
- X + X =X
- X*X =X
Inclusion Exclusion
First terms - binary combo + triple combo
Rare event method
Provides overestimation
F-N graph
Cumulative frequency (X)
Consequences (Y)
Comment on high risk value
- we can minimise the rough re design
- or implement additional safety measures
If they ask what is frequency of experiencing more than 4 fatalities
It is basically cumulative frequency (add from bottom) flip frequencies up side down and then add to how ever many
Accidents occur through
- failure of man made systems (system failure, maintenance or operational issues)
- natural causes
- intentional
Risk
Frequency of undesired events
- consequence * frequency
Frequency
Probability of occurrence
Symbols
- curved bottom is OR
- flat bottom is AND
Components with no repair
= 1- e^(-lambda t)
( lambda is failure rate)
Close to lambdat
Unscheduled maintenance
where failure is revealed
Q = lambda * repair time
Scheduled maintenance
Q= lambda( inspection time/ 2 * repair time)
Inclusion exclusion
First terms - binary terms+ triple combo
Lower bound
First terms - binary combo
