what-when-how
In Depth Tutorials and Information
Union presents evidence of human failures representing 64% of declared accidents.
Risk analysis must consider factors outside the system level. Human operation and
organizational influence must be taken into account to sufficiently implement some
practice of accurate risk analysis.
he concept of risk is a widely studied topic. In order to assess risk, it must first
be defined. Risk is generally defined as the combination of the occurrence prob-
ability of damage and its gravity. Likewise, risk assessment is defined as the series of
logical steps used to systematically examine the risks associated with an operational
system [15]. his assessment consists of a risk assessment and reduction process,
which is graphically displayed in Figure 9.6.
A popular method for analyzing the occurrence of critical events is to apply
the “bow-tie” risk analysis. his method is suicient for analyzing a system at the
technical level, and consists of a fault tree and an event tree. he paths that exist
between different entities represent different accident scenarios from initial con-
tributing factors to the final consequences. However, this method is limited. It
adequately handles evaluating risk at the technical level but fails to consider con-
tributing factors that are relevant to an accident scenario. Modification of the bow-
tie method would be necessary to incorporate the contributing factors into the risk
analysis. Likewise, present risk analysis methods require modification because they
Start
Determination of the Machine Limits
Identification of
Dangerous Phenomena
Risk Analysis
Risk Estimation
Risk Assessment
Risk Evaluation
Was the risk
Suitably
Reduced?
Yes
End
No
Risk Reduction
Figure9.6
Riskassessmentandriskreductionprocesses.(FromLéger,A.,Duval,
C.,Weber,P.,Levrat,E.,andFarret,R.,RiskAnalysisofComplexSocioTechnical
SystemsbyUsingBayesianNetworkModeling,availablefrom:http://www.cper-
misn-sectaf.cran.uhp-nancy.fr/Files/ACD/p42.pdf.)
