TABLE OF CONTENTS The first step into the analysis of the risk of a given system is that of identifying the hazards associated to its operation. The output of this task consists of a list of the sources of potential danger, i.e. those accident initiators (component failures, process deviations, external events, operator errors) which have a probability of occurrence not equal to zero and which can give rise to significant consequences. The identification of the accident initiators is obviously a key aspect of the overall safety analysis and great care must be put into its completeness since those accident events not included at this stage are very unlikely to enter in the analysis at a later stage.
The methods developed for performing this step consist, in general, in a qualitative analysis of the system and its functions, within a systematic framework of procedures. The methods strongly rely on the expertise of the designers, analysts and personnel who have designed, operated and maintained the system. Some of the methodologies most commonly used are:
Check list
Hazard index method
Hierarchical trees
System Identification of Release Points (SIRP)
Failure Mode and Effect Analysis (FMEA)
HAZard and OPerability analysis (HAZOP)
Such methodologies are not mutually exclusive but, rather, they are often used in a complementary way.
As the first two methods are of straightforward application, here we limit ourselves to giving few insights into the principles of the other four methods in the list. For more details, the interested reader should consult the specialized literature, e.g.
