Risk analysis quantitative reviews

Hazards and Operability (HAZOP) Facility Risk Review Quantitative Risk Analysis... 

The comprehensive and detailed assessment of the risks required for a safety-case can only be satisfactorily carried out for major installations with the aid of computer software. Suites of programmes for quantitative risk analysis have been developed over the past decade by consulting firms specializing in safety and environmental protection. Typical of the software available is the SAFETI (Suite for Assessment of Flammability Explosion and Toxic Impact) suite of programs developed by DNV Technica Ltd. These programs were initially developed for the authorities in the Netherlands, as a response to the Seveso Directives of the EU (which requires the development of safety cases and hazard reviews). The programs have subsequently been developed further and extended, and are widely used in the preparation of safety cases see Pitblado el al. (1990). 

Let us now turn our attention to the main steps of any procedure constructed to anticipate or respond to the risk analysis requirements set forth by the statutes reviewed above or voluntarily established as product standards by industries. It is important to note that this type of procedure is a technical means to arrive at a quantitative estimate. The decisions regarding the acceptability of the result is sociopolitical and is, therefore, beyond the scope of this discussion. 

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. 

Allowing time in the early stages of design for critical reviews and evaluation of alternatives would involve studies such as an early hazard and operability (HAZOP) study, using flowsheets, before final design begins,4 Fault tree analysis, quantitative risk assessment (QRA), checklists, audits, and other review and checking techniques can also be very helpful. These techniques are extensively discussed in the technical literature and will not be discussed in detail here. 

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. 

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. 

In the course of assessing your company s current PSM status, you and your team have almost certainly gained a clear sense of which facilities pose the greatest risk, whether by virtue of inherent process hazards, human factors, management systems, or a combination. As you set priorities for implementation you should closely review information gleaned from the assessment tasks. In addition, you should try to validate or flesh out your impressions through some more quantitative analysis that can help to identify priority facilities. 

Tliis part of tlie book reviews and develops quantitative metliods for tlie analysis of liazard conditions in terms of the frequency of occurrence of unfavorable consequences. Uncertainty characterizes not only Uie transformation of a liazard into an accident, disaster, or catastrophe, but also tlie effects of such a transformation. Measurement of uncertainty falls witliin tlie purview of matliematical probability. Accordingly, Chapter 19 presents fundamental concepts and Uieorems of probability used in risk assessment. Chapter 20 discusses special probability distributions and teclmiques pertinent to risk assessment, and Chapter 21 presents actual case studies illustrating teclmiques in liazard risk assessment tliat use probability concepts, tlieorems, and special distributions. 

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. 

This paper will summarize briefly some work my colleagues and I at Decision Focus Incorporated have carried out for EPA to show how decision analysis might be used to assist decision making under TSCA ( 5). I will first briefly review the concepts of quantitative risk assessment and cost-benefit analysis to show how decision analysis fits with these concepts and provides a natural way of extending them. Then I will illustrate the approach using a case study on a specific chemical, perchloroethylene. 

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. 

The AE double dot plot is a type of graph designed to compare safety data between an experimental treatment and its control group with a quantitative risk measurement (Eigure 11.3). It has also been used in meta-analysis in randomized controlled trials and observational studies. In AE reporting, double dot plots are often used to present the frequency of key AEs along with quantitative risk measurements. Having both types of information side-by-side helps reviewers to identify elevated AEs. 

---