chapter  8
38 Pages

Risk Analysis Techniques

The objective of this chapter is to establish a set of tools and techniques that we need to utilize in the process of carrying out a risk analysis and assessment. In order to understand the application, importance and role of these techniques in the context of risk analysis, it is of crucial importance to first gain an understanding of the basic concepts of risk analysis, as well as the underlying components of risk. The first part of this chapter therefore gives a brief introduction to risk analysis and assessment, a concept that is treated in much more detail in later chapters. The second part of the chapter gives some useful basic theory related to system description and structures. Finally, the third and main part of this chapter deals directly with risk assessment techniques. The following five techniques are studied:

. Preliminary Hazard Analysis (PHA)

. Hazard and Operability Studies (HAZOP)

. Failure Mode, Effect and Criticality Analysis (FMECA)

. Fault Tree Analysis (FTA)

. Event Tree Analysis (ETA)

These techniques are utilized in relation to different aspects of risk analysis. The Preliminary Hazard Analysis (PHA) methodology is used to identify possible hazards, i.e. possible events and conditions that may result in any severity. A more extensive hazard identification method is Hazard and Operability Studies (HAZOP), which searches much more systematically for system deviations that may have harmful consequences. The Failure Mode, Effect and Criticality Analysis (FMECA) can be used to identify equipment/system failures and assess them in terms of causes, effects and criticality. The application of an FMECA gives enhanced system understanding as well as an improved basis for quantitative analysis. Fault Tree Analysis (FTA) and Event Tree Analysis (ETA) are the most commonly used methods in terms of establishing the

probability of occurrence and the severity of the consequences, for hazards in the context of risk analysis.