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TREES DIAGRAMS IN RISK ASSESSMENT, Fadhila Abidah 09111840000092 …
TREES DIAGRAMS IN RISK ASSESSMENT
Event Tree Analysis
Definition.
Event tree considers the impact of the failure of a particular component or item in the system, and works out the effect such a failure will have on the overall system risk or reliability
Inductive approach
Intiating events
Failure/unsafe conditions in individual items of equipments
Human error
Utility failures
External events: Hurricanes, earthquakes
Y
if event has taken place
N
if not
Uses & Limitations
Fault Trees Analysis
(+)
Identify failures deductively
Highlight the important elements of system related to system failure
Create a graphical aid for system analysis and management
Provides an alternative way to analyze the system
Focus on one fault at a time
Expose system behavior and possible interactions
Accounts for human error
(-)
Diagrammatic format discourages analysts from stating explicitly the assumptions and conditional probabilities for each gate
Can be time-consuming and complicated for larger systems
Only examines one specific top event
Analysts may overlook failure modes and fail to recognize common cause failures unless they have a high level expertise and work jointly
Event Trees Analysis
(+)
Enables the assessment of multiple, co-existing faults and failures
Functions simultaneously in cases of failure and success
No need to anticipate end events
Can be performed on various levels of details
Visual cause and effect relationship
Relatively easy to learn and execute
(-)
Addresses only one initiating event at a time
The initiating challenge must be identified by the analyst
Pathways must be identified by the analyst
Level of loss for each pathway may not be distinguishable without further analysis
Success or failure probabilities are difficult to find
Requires an analyst with practical training and experience
Fault Tree Analysis
Definition.
A graphical binary logic top-down technique that is used to describe how a specific unwanted event in a system may be caused by the effects of a single failure or combination of failures.
Consists of two elements,
events
and
logic gates
which connect the events to identify the causes of the
top undesired event
Layout
FTA Events
Undeveloped event:
No scope of developing it further
Intermediate event:
Occurs between top and basic events
Basic event:
Lowermost event that can't be developed further
Transfer:
Signifies continuation of tree on a separate sheet
Logic gates
AND gate.
Output event occurs if
all input
events occur simultaneously
OR gate.
Output event occurs if
any one
of the input event occurs
Fadhila Abidah
09111840000092
Manajemen Risiko dan GCG B