Risk analysis qualitative reviews

Several qualitative approaches can be used to identify hazardous reaction scenarios, including process hazard analysis, checklists, chemical interaction matrices, and an experience-based review. CCPS (1995a p. 176) describes nine hazard evaluation procedures that can be used to identify hazardous reaction scenarios-checklists, Dow fire and explosion indices, preliminary hazard analysis, what-if analysis, failure modes and effects analysis (FMEA), HAZOP study, fault tree analysis, human error analysis, and quantitative risk analysis. 

The results of the prioritization process are detailed in Table 3.5. Three activities have been ranked as Lower Risk and will be dropped from further consideration. These chemicals have been ranked as lower risk because the concentration of aqueous ammonia and formaldehyde in combination with a small shipment volume presents only a minor enviromnental impact potential. Additionally, methyl bromide is used at some facilities, but it is received in small cylinders that have only a localized impact potential if released while in transit. These chemicals and modes of transport will, however, continue to be reviewed and monitored as part of the global risk management program, including a primary management system review. The remaining chemical and modes of transport will be escalated for qualitative risk analysis. 

At this point in the example, the eompany-wide reviews eompleted in Chapters 2 and 3 are replaeed with a first-level qualitative risk analysis foeused on the transportation aetivities of a single XYZ Cheinieal faeihty. To eontinue the example, a single XYZ Chemical facility is selected. This facility will continue to be evaluated as the level of analysis detail increases from qualitative to semi-quantitative in this chapter to quantitative risk analysis (Chapter 5). As the level of detail increases, the analysis will be directed at specific questions that remain following each level of analysis. This facility will continue to be the focus of Chapter 6 where the security vulnerabihty of the hazardous materials in transit is evaluated. Chapter 7 where risk reduction options are evaluated, and Chapter 8 where the ongoing management of risk continues in the future. 

The site-level health and safety manager was given notice from corporate for the need to conduct the qualitative risk analysis of the plant s hazardous material transportation operations. The safety manager was provided with a questiotmaire regarding all chemicals of concern, shipping quantities, modes of transit, and the route characteristics (similar to the checklist found in Table 4.2). This information was transmitted back to corporate for analysis, which included a corporate-level comparison to the other XYZ Chemical facihties risk results. Based on the information collected at the site level, the following was determined and reviewed by corporate for this facility ... 

From this qualitative review of the operation, it was recommended that certain activities undergo a more detailed risk analysis. The analysis will be facilitated by a corporate representative and performed by a team of local personnel and other supply chain partners, as required. The activities that will be included in this more detailed review will include ... 

An early or initial screening study for the identification, qualitative review, and ranking of process hazards, typically conducted during an initial evaluation of existing facilities or a project s conceptual design. Recommendations for the mitigation of identified hazards are provided. See also Preliminary Risk Analysis Process Hazard Analysis (PHA). 

Fire Protection FIVE and FRANC support quantitative and qualitative fire risk, assessmeiil. FRANC also supports the analysis of alternative safe shutdown paths during an Appendix R review. System train availability is exhibited on a system status panel, Using this a strategy can be defined to upgrade Thcrnm 1. if identify risk significant areas. 

Because most research effort in the human reliability domain has focused on the quantification of error probabilities, a large number of techniques exist. However, a relatively small number of these techniques have actually been applied in practical risk assessments, and even fewer have been used in the CPI. For this reason, in this section only three techniques will be described in detail. More extensive reviews are available from other sources (e.g., Kirwan et al., 1988 Kirwan, 1990 Meister, 1984). Following a brief description of each technique, a case study will be provided to illustrate the application of the technique in practice. As emphasized in the early part of this chapter, quantification has to be preceded by a rigorous qualitative analysis in order to ensure that all errors with significant consequences are identified. If the qualitative analysis is incomplete, then quanhfication will be inaccurate. It is also important to be aware of the limitations of the accuracy of the data generally available... 

Both qualitative and quantitative evaluation techniques may be used to consider the risk associated with a facility. The level and magnitude of these reviews should be commensurate with the risk that the facility represents. High value, critical facilities or employee vulnerability may warrant high review levels. While unmanned "off-the-shelf, low hazard facilities may suffice with only a checklist review. Specialized studies are performed when in-depth analysis is needed to determine the cost benefit of a safety feature or to fully demonstrate the intended safety feature has the capability to fully meet prescribed safety requirements. 

Many methods have been developed that are suitable for assessing risks associated with the operation of facilities involving chemical reactivity hazards. The more commonly used methods are summarized in Table 4.9. They differ in their applicability, level of effort, and how systematic they are in identifying accident scenarios. All of the methods except layer of protection analysis (LOPA) may be applied qualitatively, and all except checklist reviews may be performed in at least a semiquantitative manner. CCPS (1992a) is a basic source of information on each of these methods. 

Process Hazard Analysis— An organized effort to identify and evaluate hazards associated with chemical processes and operations to enable their control. This review normally involves the use of qualitative techniques to identify and assess the significance of hazards. Conclusions and appropriate recommendations are developed. Occasionally, quantitative methods are used to help prioritize risk reduction measures. 

For methods which require an additional qualitative identification component, snch as an FDA method for the analysis of pesticide residnes in food (Section 10.4.3a), the analysis of the validation data shonld be reviewed from the perspective of whether or not the resnlts snpport the need to demonstrate an extremely low risk for false positives. In this respect, a zero rate of false positives refers to method validation, nnder controlled circnmstances with known samples. If there is one false positive for a confirmatory method, the validation shonld be failed. 

The students were then directed to read a well balanced review of quantitative versus qualitative analysis of risk (Apostolakis 2004), and a good account of possible approaches for assessing and managing risks from extreme events (Bier et al. 1999). 

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