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Nowadays one of the most important decisions in safety issues inBrazilian Oil and Gas industry is that it’s necessary to shut downplant because one specific failure or required maintenance in protection system makes influence on risk level. Most of time, experienced operators make decisions based on their background despite carrying out a risk analysis to supporttheir decision. Therefore in so many cases, refinery plants work oncatastrophic risk level due to subjective decisions. In order toimprove the operator decision, a specific methodology was established to applyrisk assessment using PRA Preliminary Risk Analysis, LOPA Layer ofProtection Analysis and FTA Fault Tree Analysis in order to check risk levelor layer of protection availability. By this way, as the first step, thePreliminary Risk Analysis will be carried out in order to qualify risk andmainly define consequences severity. The second step will carry out the LOPA inorder to find out the failure probability of all layers of protection andwithout one of those layers of protection which requires maintenance oreven failure. In addition, when is necessary to check that contingencysystems availability FTA will be carried out? In the firstcase, it is possible to substitute the layer of protection for another in order to keep risk on acceptable level. In the second case, it is necessary tocheck if contingency system is available and assess if consequence gets worseor keeps on the same level. In both cases, the final risk will be assessedand compared with the previous one defined on PRA. In case of risk, it isunacceptable that the final decision will shut down plant. Therefinery study case will be shown as an instance of such methodology.

KEYWORDS

Preliminary Risk Analysis; Fault Tree Analysis; Layer of Protection Analysis; Tolerable Risk

Cite this paper

E. Calixto, C. Daniel Cunha de Moraes, C. Atusi Outi and W. Alves dos Santos -Risk Assessment Methodology to Support Shutdown Plant Decision,- Open Journal of Safety Science and Technology, Vol. 3 No. 4, 2013, pp. 116-124. doi: 10.4236-ojsst.2013.34015.





Autor: Eduardo Calixto, Carlos Daniel Cunha de Moraes, Cid Atusi Outi, Wilson Alves dos Santos

Fuente: http://www.scirp.org/



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