System analysis - Operation safety

The growing complexity of industrial organizations and systems, and the constant quest for greater competitiveness, are forcing companies and equipment managers to systematically and almost continuously assess performance. Performance is multidimensional. Declined according to the attributes of cost, quality, lead time, ..., criteria of productivity, flexibility, robustness, ..., environmental, social, societal aspects, ..., it must be evaluated over the entire life cycle of the system or products produced. This diversity, driven by a socio-economic rationale of sustainable development, generates a strong need for methodologies, techniques and tools to help decision-makers make choices in the design, development or operating phases of products and systems. There are many answers to this need, and many specialized books and articles on the subject, ranging from a detailed overview of all forms of assistance to the precise presentation of specific tools or techniques.

The aim of this dossier is to provide an effective approach to system analysis, in order to estimate and evaluate system performance. The methodological elements that guarantee a rational analysis of the system and its performance are highlighted, focusing on the operating safety aspects considered right from the design stages; the search for performance is, in fact, correlated with the constant concern to improve the system's operational availability and optimize its overall cost of ownership.

The file is organized into five parts.

The notion of a system is first discussed. Based on the various descriptive views of a system, the approach to be followed for effective analysis is studied. The angle considered is then that of a systemic approach to analysis.

The notion of system performance and its measurement is presented in the second paragraph. Going straight to the heart of performance evaluation problems, the position of dependability in achieving performance is highlighted.

In the following paragraph, we briefly present the main analysis methods used to describe and represent system operation. These methods prepare the way for functional performance evaluation and predictive risk assessment. This review has been limited to a few illustrative, commonly-used tools, focusing on the position taken by these tools in the general analysis process and, on a particular level, highlighting the presence of uncertain parameters, preponderant in the early stages of the product or system life cycle.

The fourth paragraph describes the principles involved in dealing with uncertainty in modelling and assessment, followed by a presentation of the principles involved in predictive risk analysis. This paragraph contains...