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Proceedings of the Eighth International Conference on Probabilistic Safety Assessment & Management (PSAM)

Michael G. Stamatelatos
Michael G. Stamatelatos
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Harold S. Blackman
Harold S. Blackman
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ASME Press
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The regulations from the Petroleum Safety Authority Norway (PSA) for the management of health, safety and environment of offshore petroleum installations call for a dedicated assessment and evaluation of all barriers against major hazards, both physical and non-physical, as well as any interdependencies and common threats to barriers and barrier elements. Such assessments and evaluations have not been carried out for offshore installations, although corresponding requirements apply in other industries, most notably in the nuclear power industry.

A comprehensive R&D program initiated by the Norwegian Research Council has set a goal to carry out an extensive demonstration project, whereby all relevant barrier elements are integrated into one comprehensive model, for a dedicated case study.

A method has been proposed based on use of Fault Trees, Event Trees, Influence Diagrams, Risk Influencing Factors and simplified analysis of dependencies between RIFs. The method was outlined in a PSAM7 paper in 2004.

Some case studies in order to demonstrate application of the method and explore the strengths and challenges of the analysis have been carried out in 2004 and 2005. The case studies have focused in particular on the robustness of the results, and the usefulness of quantitative results in a risk-informed decision-making context in the operations phase of an offshore petroleum installation. The case studies have been quite different with respect to input data available, which gives an opportunity to compare how these differences influence on the usefulness and robustness.

The focus in this case study has been on testing different methodologies for establishing platform specific values, both in relation to the containment barrier and in relation to two of the consequence barriers. Limited focus has been on establishing risk results as such, except as a means to provide information about the methodology and how it is suited for use in risk studies.

The overall conclusion is that the methodology that has been developed and tested shows a promising potential for use in practical applications. TTS (Technical Condition Safety) audits and expert judgement are the two most effective sources for scoring of RIFs.

It is considered that the methodology addresses some of the weaknesses identified in currently applied approaches. It is quite clear that more experience needs to be gained with use and that the details need to be developed further through practical usage, but it is considered that the basic framework is a sound and reasonable approach for addressing these issues.

As regards the work associated with implementing this approach into practical studies, it is also the analysts' opinion that it is possible to implement the key elements of this into QRAs without excessive additional amount of work. The experience from performing the case study work is that the work required to establish platform specific scores related to both technical systems and organizational/human factors is likely to be much more limited than what was expected before the work was started. There is no doubt that the process can be “streamlined” and probably also simplified in such a way that the work can be performed significantly quicker than what was the case in the case study. Through the introduction of “generic elements” (e.g. generic weights of RIFs) in the analysis process, further optimization of the work process can be achieved.

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