A review of safety analysis methods applied to the design process

Design for safety is a process of identifying hazards, estimating them and finally evaluating them in terms of two basic parameters, namely the occurrence probability of each hazard and the magnitude of possible consequences. These two parameters can be assessed using either a top-down or a bottom-up approach on either a qualitative or a quantitative basis, depending on the nature of the particular engineering system and the safety assessment techniques in hand. This paper describes the concepts of qualitative and quantitative safety analysis, and bottom-up and top-down safety modelling approaches. The typical safety analysis techniques are studied with respect to the proposed design for safety framework. An analysis of the input requirements and the outcomes of the safety analysis methods is carried out to identify their possible interrelationships within the safety analysis process in order to make full use of the advantages of each method. The selection of these safety analysis methods is discussed in the context of large engineering products. Problems concerned with failure and repair data collection programmes are also studied and some typical failure and repair data sources are described.