Risk assessment semi-quantitative analysis level

The deviation scenarios found in the previous step of the risk analysis must be assessed in terms of risk, which consists of assigning a level of severity and probability of occurrence to each scenario. This assessment is qualitative or semi-quantitative, but rarely quantitative, since a quantitative assessment requires a statistical database on failure frequency, which is difficult to obtain for the fine chemicals industry with such a huge diversity of processes. The severity is clearly linked to the consequences of the scenario or to the extent of possible damage. It may be assessed using different points of view, such as the impact on humans, the environment, property, the business continuity, or the company s reputation. Table 1.4 gives an example of such a set of criteria. In order to allow for a correct assessment, it is essential to describe the scenarios with all their consequences. This is often a demanding task for the team, which must interpret the available data in order to work out the consequences of a scenario, together with its chain of events. 

Once the specific issues and scope of the analysis are defined, a semi-quantitative risk assessment may be conducted using either risk indexing or a risk ranking matrix. The risk indexing and risk matrix techniques should be built on the information from the earlier analyses. Each level of risk analysis should not be considered a separate effoit, but a continued understanding of the transportation issue. Additionally the information gained from these activities can be used to update the qualitative analysis, especially benchmarking comparisons. 

Once a set of recommendations has been developed, the options must be analyzed to determine the benefits, or essentially the level of risk reduction. The risk analysis method utilized to assess the baseline operational risks should be the same method used to analyze each of the potential risk mitigation options. Therefore, if a semi-quantitative technique was used to assess the baseline risk, then the same assumptions, techniques, and risk evaluation criteria (risk matrix, risk index, etc.) should be used to evaluate the effectiveness of the risk reduction options. 

There are several levels of risk analysis within most methodologies for assessing risk quantitative, semi-quantitative, and qualitative. For PSSR concerns we deal almost exclusively with qualitative assessments, that is, just a determination of high or low risk. Generally any truly quantitative risk analysis (QRA) indicated for a trigger event would be performed to enhance the process hazard analysis. The associated PSSR for such a trigger event would simply follow action item progress related to the quantitative risk assessment s action items. In this case the PSSR helps assure that any action items from a QRA are appropriately followed. 

Fire and explosion risks consider both probability of an undesired event, and severity of its consequences. For risk analysis purposes, the analyst defines the level of detail and system boundary. The common qualitative, quantitative, semi-quan-titative risk assessment approaches are supposed to be known to the reader EC/FDIS 31010 2009). 

Semi-quantitative methods use quahtative as well as quantitative evaluation procedures. Methods of indexing and ranging of risks also belong to this method. From the practical point of view, it is difficult to appraise the value of indexing methods for risk analysis purposes. Unlike quahtative methods it gives a quantitative assessment of a risk level, but differs in straightforwardness demanding for computer recourses. It also uses a small number of parameters to assess the efficacy of the FEP measurements. 

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