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Risk and reliability allocation methodology for offshore oil units.

Faertes, Denise (2001) Risk and reliability allocation methodology for offshore oil units. PhD thesis, University of Sheffield.

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Abstract

Early approaches in engineering safety were based on deterministic concepts, according to which, safety was assured by making conservative assumptions in the design of industrial systems, as well as through the use of safety factors, based on engineering judgement. Recent safety approaches are based on probabilistic concepts, in reliability techniques and accident consequence modelling, according to which safety is defined in terms of probabilities or frequency of failures and severity of consequences. These two items compose the basis for the evaluation of industrial risks. Risk assessment techniques are particularly relevant for those working offshore, who are exposed full-time to several different hazards from process equipment, risers or blow-outs, ship collisions, helicopter accidents, extreme weather, etc. At present, there are several sophisticated techniques, models and software already developed, that can be used in probabilistic risk analysis. However, general criteria for the acceptability of estimated risks have not been suitably developed, although several attempts have been made, and the question: "How safe is safe enough?" still remains without an appropriate answer. Within this context, this Thesis presents a brief description of techniques and models presently used for risk evaluation, as well as legislation concerning risk tolerability criteria and other proposed safety targets. Regarding the establishment of global safety criteria for offshore oil units, the focus of this work will be the development of a risk and reliability allocation methodology to achieve them. From data collected from more than thirty Brazilian offshore oil units, some of them operating for more then ten years, individual risk values for offshore employees are going to be calculated. Based on these values, obtained for the individual risk, and on a quantitative risk assessment performed for a Brazilian Floating Production Storage Offloading vessel, a risk and re1iability allocation methodology will be proposed. This methodology provides a feasible" model to allocate reliability and risk criteria for the main safety functions of an offshore unit in a self-consistent manner. It provides a method for design engineers to establish minimum reliability levels for the safety systems of an industrial facility, in order to achieve safety targets previously defined for it. The application of a risk and reliability allocation model to the problem of setting criteria for a range of hazardous scenarios presented in the operation of an offshore oil production unit is a novel approach. It is hope that the proposed methodology can contribute to a wider discussion about the establishment of a global measure for the evaluation of safety performance of offshore oil units.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Chemical and Biological Engineering (Sheffield)
Identification Number/EthosID: uk.bl.ethos.518870
Depositing User: EThOS Import Sheffield
Date Deposited: 14 Dec 2016 14:49
Last Modified: 14 Dec 2016 14:49
URI: http://etheses.whiterose.ac.uk/id/eprint/14960

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