Risk analysis methods

Risk-Based Inspection. Inspection programs developed using risk analysis methods are becoming increasingly popular (15,16) (see Hazard ANALYSIS AND RISK ASSESSMENT). In this approach, the frequency and type of in-service inspection (IS I) is determined by the probabiUstic risk assessment (PRA) of the inspection results. Here, the results might be a false acceptance of a part that will fail as well as the false rejection of a part that will not fail. Whether a plant or a consumer product, false acceptance of a defective part could lead to catastrophic failure and considerable cost. Also, the false rejection of parts may lead to unjustified, and sometimes exorbitant, costs of operation (2). Risk is defined as follows ... 

EIGURE 7. Ovei-view of risk analysis methods. 

McCormick, N. J. Reliability and Risk Analysis Methods and Nuclear Power Applications. Academic Press, San Diego, 1981. 

To those already familiar with hazard/risk analysis methods, a "PHA" designates a Preliminary Hazard Analysis. Unfortunately, the PSM Rule uses these same letters to designate Process Hazard Analysis. In this document, PrHA will designate Process Hazard Analysis to avoid confusion with Preliminary Hazard Analysis. Note that other literature may be confusing on this issue. 

In 1993, the Center for Chemical Process Safety (CCPS) published Guidelines for Safe Automation of Chemical Processes (referred to henceforth as Safe Automation). Safe Automation provides guidelines for the application of automation systems used to control and shut down chemical and petrochemical processes. The popularity of one of the hazard and risk analysis methods presented in Safe Automation led to the publication of the 2001 Concept Series book from CCPS, Layer of Protection Analysis A Simplified Risk Assessment Approach. This method builds upon traditional process hazards analysis techniques. It uses a semiquantitative approach to define the required performance for each identified protective system. 

Table 19 Comparison of different risk analysis methods. 

Our assignment for EPA was to apply quantitative risk analysis methods to the determination of risk for a particular chemical. The health risks for perchloroethylene turned out to be highly uncertain, but by using decision analysis concepts we were able to display this uncertainty in terms of alternative assumptions about the dose response relationship. Similar methods might be used to characterize uncertainties about human exposure to a chemical agent or about the costs to producers and consumers of a restriction on chemical use. 

Our failure risk analysis and opportunity method and iterative software tool, as part of our New Product Process Innovation (NPPI) Tool Library, promotes systematic collaboration and team-oriented engineering thinking when a new pharmaceutical manufacturing system process and/or product are developed. (We call it opportunity method too, since most risks, if not all, offer new opportunities for innovation.) It is based on our generic process failure risk analysis method that could be apphed to literally any process that involves risk—and innovation is a very risky process. 

Our risk analysis method and tools help the engineering management team to understand some of the following concerns ... 

One important aspect of the quality systems approach is the ongoing collection and analysis of quality data to continuously evaluate quality system effectiveness. Historical data, process knowledge, and risk analysis methods can be applied to identify specific data requirements. Trending and other data analysis methods can allow identification of actual and potential sources of nonconformity so that appropriate corrective and preventive actions can be taken in accordance with established change control procedures. 

Systematic searches for hazard, assessment of risk, and identification of possible remediation are the basic steps of risk analysis methods reviewed in this chapter. 

There are many risk analysis methods, but all have three steps in common ... 

In this section, a safety dataset, resulting from over 20 years of practical experience with risk analysis of chemical processes, is presented. These data build the base of risk analysis in the fine chemicals and pharmaceutical industries, essentially in multi-purpose plants. Therefore, the dataset introduces plant considerations only at its end. This allows exchanging them without any need for recollecting the whole dataset, in cases where the process is transferred from one plant unit to another. Moreover, this dataset may be used in the frame of different risk analysis methods. 

Contents indude qualitative and quantitative evaluation of human and animal studies, risk analysis, and acceptable concentrations. Helpful appendices Include a glossary, abbreviations, and acronyms, the USFDA risk analysis method for carcinogens, and equations. 

Risk analysis methods should be also considered in long-term projects or/and Involving a large amount of capital. The forecast of cash flows can make use of statistics. Details can be found in Holland Wilkinson (Perry, 1997). 

Risk Analysis Methods Rationai and structured results lead to recommendations Participation and engagement by individuais with different perspectives, roies, and backgrounds/skill sets for safety, security, and transportation Simiiar methodoiogy Same decision metrics (guidelines) ... 

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. 

Pate-Comell M. The engineering risk analysis method and some applications. Chapter 16. [Online], [cited June 2015 http //www.usc.edu/dept/create/assets/002/50856.pdfj. Available from http //www.usc.edu/dept/create/assets/002/50856.pdf. 

Phani K. Raj, et al. 2010. Pritchard. Hazardous materials transportation on U.S. railroads application of risk analysis methods to decision making in development of regulations. Journal of the Transportation Research Board. 17(7) 22-26. 

The required safety integrity level of the instrumented function shall be derived by taking into account the required risk reduction that is to be provided by that function. For those SILs, the target PFDj,yg on demand and the target frequencies of dangerous failure are hsted in Table 3.8 [ANSI/ISA-84.00.01(2004) Part 3] for each SIF. Several risk analysis methods ranging from qualitative to fully quantitative can be deployed based on the severity and complexity of the scope, as listed in Table 3.9. 

ABSTRACT This paper highlights some aspects of the many facets of electricity distribution system risk assessment - describing the different risk consequence categories which are relevant in the whole risk picture with regards to their characteristics, their type of impact and apphcable risk analysis methods. The paper illustrates that distribution system asset management constitutes of a variety of more or less conflicting objectives - and that there is no single risk assessment method which cover all the different aspects of distribution system risk. 

In the following chapters we look further into each of these risk consequence categories. The presentation is based on the authors knowledge and experience regarding the apphcation of risk assessment methods in electricity distribution first and foremost among Norwegian distribution companies. Some of the risks are well defined with respect to risk analysis methods, while others have less history of being subject to structured risk assessment. 

The need for data - and its resolution - is also increasing significantly from the simplified risk analysis methods to the model-based ones. 

To analyse vulnerabiUty risk various system simulations are applicable e.g. contingency analyses, dynamic analyses etc. Other - more generic - model-based risk analysis methods are also apphcable (e.g. fault tree and/or event tree. Simplified and standard risk analyses methods (brainstorming, plotting in risk matrices) can also be used for more coarse analyses... 

Table 3. Summary of risk consequence categories, their predominant impact and risk analysis methods. 

The most careful and consolidated risk analysis methods, as FTA, ETA, FMEA/FMECA, have serious problems with the possibility of finding the data which analysis are based on. 

Gurcanli, G., Mungen, U. 2009 An occupational safety risk analysis method at constmction sites using liizzy sets , bit. J. of Industrial Ergonomics, Vol. 39, pp. 371-387. 

Some problems related to comparison of different risk analysis methods and tools exist. These problems are ... 

In most quantitative risk analysis methods (Uijt de Haag 2006, purple book 1999), persons present in the hazardous area are assumed to be exposed for a fixed amount of time. Assumptions for fixed exposure times are 30 minutes for a toxic exposure and 20 seconds for exposure to heat radiation. Furthermore, persons are assumed to stay on the same place. The reahty is different in case of an emergency, every person capable of escape will try to rescue himself. In case of a toxic release it is possible that a safe location (for example inside a building) is reached within the prescribed 30 minutes. On the other hand, in case of fire in crowded places, it can be expected that people are unable to escape within 20 seconds. 

Current approaches to model risk in healthcare that have been borrowed from engineering domain and industry, have not proven to be effective and insight-fid, for a niunber of specific reasons. Unlike industry, in healthcare, there is much more variability in the procedures. Traditional PRA methods assinne a linear chain of independent events that lead to an accident or an unsafe condition, which by far is not the case in healthcare. Much of what happens in healthcare is subject to feedbacks. A hybrid approach to modeling risk in healthcare settings, as a combination of two modeling formalisms (system dynamics and Bayesian belief networks), has been proposed. We beheve that the proposed framework overcomes the deficiencies of conventional engineering risk analysis methods by its capability to explicitly model the feedback loops, time delays and the nonlinearities that exist in a complex healthcare setting. 

To a certain degree it is a matter of preference which risk analysis method to choose. If it decided to use [ISO 13849-1] for the complete design of the E/E/PE-based safety functions, maybe it is more natural to use the risk graph within that standard. Either way, these risk analysis chapters in [ISO 13849-1] and [lEC 62061] are informative and allow you to use the risk matrix in [lEC 62061] to identify which SIL is required and then transform this SIL to a PLr by using table 4 in [ISO 13849-1] (see Figure 4) and then use [ISO 13849-1] for the remaining design steps of the E/E/PE-based safety functions. 

Use the logical process risk analysis method to determine the ranking for applying funds to each of five plants in a company. Several plants were part of the analysis. The following table lists data for the five plants under current consideration. 

As facilities become familiar with the screening level risk analysis method, they may start using other methods as well, with each method having its own advantages and disadvantages. 

The risks posed by management are neither addressed by risk analysis nor included in safety cases. Yet they have been shown to be significant contributors to accidents. This paper argues for more attention to be paid to them and for the development of a risk-analysis method to address them. The paper examines the aspects of management risk that it might cover and offers a set of proposals for its design. 

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