Читать книгу Risk Assessment - Marvin Rausand - Страница 143

The study object must be defined precisely. When the risk assessment is initiated at an early stage of a system development project, we have to suffice with a preliminary system definition and delimitation on a high level, leaving a more detailed description to a later stage. Aspects of the study object that need to be considered include the following:

 The boundaries and interfaces with related systems, both physical and functional.

 Interactions and constraints with respect to factors outside the boundary of the study object.

 Technical, human, and organizational aspects that are relevant.

 The environmental conditions.

 The energy, materials, and information flowing across boundaries (input to and output from the study object).

 The functions that are performed by the study object.

 The operating conditions to be covered by the risk assessment and any relevant limitations.

In many risk assessments, it is difficult to delimit the study object and to decide which assumptions and conditions that apply. What should be covered in the risk assessment, and what can be disregarded? In the first steps of a risk assessment, the objective should be to establish a picture of the most important risk issues related to the study object. Later on, the risk assessment may be extended to cover specific parts of the study object under special conditions.

In most cases, the study object must be divided into reasonable parts for analysis. Depending on how complicated the study object is, these parts may be subsystems, assemblies, subassemblies, and components. A numerical coding system corresponding to the system breakdown should be established, such that each part is given a unique number. In the offshore oil and gas industry, this system is usually called the tag number system.

Several methods are available for system breakdown. It is most common to use some sort of hierarchical structure. In some cases, it is most relevant to focus on functions or processes, whereas in others, the focus is on the physical elements of the system. System breakdown methods are discussed further in Chapter 11 and onwards when different methods are discussed. The study object is studied further in Chapter 4.