Human reliability analysis description

For some applications, for example, human reliability analysis, a situation needs to be rated on a numerical scale. In these cases, values such as those shown in the left-hand column of Table 3.1 can be generated by comparing the situation being evaluated with the descriptions in the second, third, and subsequent columns which represent other PIFs relevant to the situation being assessed. These represent the worst, average, and best conditions that are likely to occur in chemical plants in general and correspond to ratings of 1,5, and 9 on the numerical scale in the left hand colunrm of Table 3.1. Obviously,... 

Such a task description invites task analysis, which would lead naturally to human reliability analysis (HRA). Indeed, perhaps the earliest work in this field applied HRA techniques to construct fault trees for aircraft structural inspection (Lock and Strutt 1985). The HRA tradition lists task steps, such as expanded versions of the generic functions above, lists possible errors for each step, then compiles performance shaping factors for each error. Such an approach was tried early in the FAA s human factors initiative (Drury et al. 1990) but was ultimately seen as difficult to use because of the sheer number of possible errors and PSFs. It is occasionally revised, such as in the current FRANCIE project (Haney 1999), using a much expanded framework that incorporates inspection as one of a number of possible maintenance tasks. Other attempts have been made to apply some of the richer human error models (e.g.. Reason 1990 Hollnagel 1997 Rouse 1985) to inspection activities (La-toreUa and Drury 1992 Prabhu and Drury 1992 Latorella and Prabhu 2000) to inspection tasks. These have given a broader understanding of the possible errors but have not helped better define the PoD curve needed to ensure continuing airworthiness of the civil air fleet. 

Brief Description of Commonly Used Human Reliability Analysis Methods... 

JHEDI is derived from the human reliability management system (HMRS) and is a quick form of human reliability analysis that requires little training to apply. The tool consists of a scenario description, task analysis, human error identification, a quantification process, and performance shaping factors and assumptions. JEDHI is a moderate, flexible and auditable tool for use in human reliability analysis. Some expert knowledge of the system under scrutiny is required. 

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... 

Moreover, the description of the task, the qualitative analysis and the evaluation of human reliability has been extended. 

THERP involves performing a task analysis to provide a description of performance characteristics of human tasks being analyzed. Results are represented graphically in an HRA event tree, which is a formal representation of the required actions sequence. THERP relies on a large human reliability database containing HEPs, which is based upon both plant data and expert judgments. 

The editors sincerely hope that this book will, with its introduction into the basic principles and limitations of the presently available trace analytical methodology and its detailed description of reliable procedures and quality control measures, serve as a valuable aid for all those who are involved in trace element analysis. It should be especially beneficial for analysts and researchers in clinical chemistry, toxicology, biochemical and environmental research first as a general overview and second to serve as a collection of elaborated methods for the reliable determination of the above-mentioned elements and some of their species in selected (human) biological specimens. 

Since human errors consist the almost portion of causal factors of incidents in the target domain, the system provides the supports based on the Common Performance Conditions (CPCs), which is the description framework for the context of human performance adopted in the Cognitive Reliability and Error Analysis Method (CREAM) (Hollnagel 1998). 

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