Methods For The Identification Of Deviations And Their Assessment

One of the most important steps of a safety technical assessment of a plant or a process is the systematic identification of possible disturbing influences, their initiating events and effects. The character of the method applied can be quite different. In consequence the quality of the result of this identification procedure also will be different. 

The selection of the method should depend on the aim of the study. If the aim is a purely qualitative evaluation focusing on a very small balance volume, the checklist methods will be sufficient in most cases, as they have been developed to quite a degree of maturity for such a purpose. If the character of a system is more strongly addressed and if the mostly complex interactions of different functional units are to be investigated with regard to possible malfunctions, then significantly more sophisticated methods have to be applied. 

The necessary effort becomes largest when a quantitative risk assessment is to be performed. Besides identification techniques, quantitative consequence modelling methods and procedures to determine the event probability of the incident being considered must be applied. 

The following discussion can only provide a very rough overview of the methods mainly used in the chemical industry today, briefly mentioning their strengths and weaknesses. The order of presentation contains a rating only in so fiir that first the qualitative methods are described, followed by the quantitative methods. Besides this, there is not the one and only method. In many cases it is even recommendable to apply a number of methods in combination in order to meet the goal as well as possible. 

It must especially be emphasized that studying the pure description of a method does not make anyone an expert in its application. For some of those explained here, it is extremely recommendable to attend educational and training courses, which are offered by several institutions. This should be supplemented by accompanying experienced users to collect further practical experience. The proverb a method can only be as good as its user is seldom found to be as true as it is with the techniques for the identification of maloperation to be presented here. 

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The application of checklists is one of the most popular methods for the identification of process deviations and their effects, The reason lies in their broad and very simple applicability as well as in the usually relatively limited effort required. Checklists can be compiled for quite different aims of a safety technical assessment. Special lists can be developed and applied for... 

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