Operational reliability - Key concepts

Dependability is a major concern for those responsible for operating complex industrial systems to meet operational and regulatory requirements. This article describes the terminology and main concepts for optimizing the reliability, maintainability and safety of complex industrial installations. In view of the various interpretations and definitions of the terms "safety" and "security", the first section clarifies these notions according to the different sectors of activity and standards, to avoid any ambiguity in the content of this article. Operating safety is a multidisciplinary scientific discipline in its own right, and is constantly evolving to incorporate new tools and requirements, particularly in terms of maintenance and technological risk control. These issues are the subject of the second section. Often referred to as the science of failures, operational safety studies are based on precise definitions of functions, missions and failures, and are developed in the third section. In parallel, the functional and material hierarchical decompositions of industrial processes, which enable us to specify the levels of analysis, are described in the fourth section. As the time of occurrence of a failure is random, the fifth section provides a reminder of probabilities and the main failure laws. The sixth section focuses on the definitions that form the basis of operational safety: reliability, maintainability, availability and safety. Feedback on the root causes of incidents and accidents shows that over 60% of them are attributable to human error; the seventh section describes methods for assessing human reliability. The economic profitability of an industrial plant over its entire lifecycle, from design to dismantling, depends in part on operating safety. The eighth section explains its role in the evaluation of overall costs of ownership and life cycle costs, which are highly dependent on the choices made during the design phase of the industrial plant. The ninth section provides the basis for design-integrated maintenance methods and integrated logistical support. Today, the consequences of failures on people's health, property and the environment are major concerns for operating managers, who are subject to increasingly stringent regulations. The tenth section presents the challenges and methodologies involved in managing technological risks, and explains the terminology used. Based on Reason's "Swiss cheese" model, it explains the role of preventive measures in achieving an acceptable level of risk. Particular attention is paid to the special case of safety instrumented systems. The conclusion stresses the need to fully assimilate the concepts of reliability, maintainability, availability and safety in order to successfully undertake a study of operational safety. Since the early 2000s, advances in artificial...