Input Information and Methods of Analysis

In order to carry out a safety analysis fundamental information on the plant and the hazards associated with its process and operation is needed. In general, knowledge of the following issues is required  

The information on plant and system structure comprises a description of the plant, its layout, and the design and construction characteristics of equipment, systems and components. Furthermore, operating and handling procedures are included. 

Before analyzing a technical system it makes sense to define the boundary conditions of the analysis. This implies fixing the outer boundary for the object of analysis defined in Table 9.1 and the degree of detail (depth) of the analysis. The way of doing this is illustrated by the following example of a telephone [8]. 

Apart from the outer boundary the inner boundary, i.e. the degree of detail of the analysis, must be determined. With reference to the telephone example this implies the question whether screws, coils, cables etc. have to be considered or not. Does the analysis have to address the molecular or atomic level or go even further Obviously not. In practical cases the degree of detail is determined by the objective of the analysis. If we intend to find out the consequences of a pump failure, it suffices to consider the pump as a unit. This unit comprises the motor, the impeller, the power transmission and the easing as well as the local control boards and the cables to the sockets in the wall. Should, however, the failure of the pump itself be examined, the piece-parts mentioned must be eonsidered individually or even be broken down to smaller units. 

The adequate choice of the inner and outer boundaries is important for the success of the investigation. Whatever has an impact on the objective of the investigation must be considered without clouding the view on the essentials by too much detail. The outer boundary fixes the scope of the analysis, the inner boundary its detail (depth). 

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