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An integrated framework for risk and safety evaluation and process design

Moradi, Fakhteh (2010) An integrated framework for risk and safety evaluation and process design. PhD thesis, Murdoch University.

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Safety evaluation and risk assessment in processing plants can improve the reliability of systems and reduce the number of hazardous events or eliminate the undesirable consequences of these events. Safety and risk study may be conducted at any stage of the plant life cycle from the conceptual design to the operational phase. Although performing safety improvement and risk treatment in any step of plant life would have important benefits, only early consideration of risk and safety results in permanent and fundamental impacts on the reliability of the system. Integration of safety assessment into process design provides the opportunity to take preventive and proactive actions to eliminate possible hazards. It allows to fundamentally enhance the safety status of the plant rather than using passive add-on controls and taking corrective actions which were common in traditional approaches. A number of works have addressed this topic previously, however, few works have tried to develop an integrated framework to implement both process design and safety assessment concurrently.

Petri net tool has been introduced and investigated in this study to achieve integration of safety assessment and process design. The Petri net is a powerful graphical modelling tool with the mathematical ability to implement multiple functions simultaneously. Inherent safety assessment method and probabilistic risk analysis technique have been combined to create a new measure for safety evaluation and risk assessment of the plant. The integrated framework has been developed based on the implementation of the combined method using the introduced Petri net tool. The proposed approach has the capability to automatically generate all possible combinations of the basic unit operations and the unit operations which are available for safety enhancement in a processing plant.

The performance of the integrated framework has been demonstrated and evaluated through two case studies: an acrylic acid production plant and a gold processing plant. The results with the outcomes of application of two well-known methods of inherent safety assessment and probabilistic risk analysis confirmed the reliability of the proposed method. It showed that the proposed approach has the ability to generate all possible process options and execute the safety evaluation simultaneously. The final safety factor calculated for each process option takes into account a wide range of safety and risk aspects. This approach provides a more comprehensive safety and risk assessment in comparison with the other existing methods. It was concluded that the proposed framework is an efficient solution to safety consideration during the early design stages.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Engineering and Energy
Supervisor(s): Bahri, Parisa
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