Risk Assessment Methodology to Support Shutdown Plant Decision

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

Energy Planning Engineer (Coppe), Rio de Janeiro, Brasil.
Mogi das Cruzes University, Sao Paulo, Brasil.
Petrobras SA, Rio de Janeiro, Brasil.
Taubate University, Safety Engineer, Sao Paulo, Brasil.

DOI: 10.4236/ojsst.2013.34015                

Abstract

Nowadays one of the most important decisions in safety issues in Brazilian Oil and Gas industry is that it’s necessary to shut down plant 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 support their decision. Therefore in so many cases, refinery plants work on catastrophic risk level due to subjective decisions. In order to improve the operator decision, a specific methodology was established to apply risk assessment using PRA (Preliminary Risk Analysis), LOPA (Layer of Protection Analysis) and FTA (Fault Tree Analysis) in order to check risk level or layer of protection availability. By this way, as the first step, the Preliminary Risk Analysis will be carried out in order to qualify risk and mainly define consequences severity. The second step will carry out the LOPA in order to find out the failure probability of all layers of protection and without one of those layers of protection which requires maintenance or even failure. In addition, when is necessary to check that contingency systems availability FTA will be carried out? In the first case, 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 to check if contingency system is available and assess if consequence gets worse or keeps on the same level. In both cases, the final risk will be assessed and compared with the previous one defined on PRA. In case of risk, it is unacceptable that the final decision will shut down plant. The refinery study case will be shown as an instance of such methodology.

Keywords

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

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	F. De Cicco and M. L. Fantazzini, “Tecnologias Consagradas de Gestao de Riscos,” Série Risk Management, Sao Paulo, 2003.
[2]	E. Calixto, “Integrated Preliminary Hazard Analysis Methodology Regarding Environment, Safety and Social Issues: The Platform Risk Analysis Study,” ESREL, Stavanger, 2007.
[3]	E. M. Marzal and E. Scharpf, “Safety Integration Level Selection. Systematics Methods Including Layer of Protection Analysis,” The Instrumentation, Systems and Automation Society, 2002.
[4]	R. Gowland, “Practical Experience of Applying Layer of Protection Analysis for Safety Instrumented Systems to Comply with IEC 61511,” European Process Safety Centre, Rugby, ESREL, 2006.
[5]	Layer of Protection Analysis American Institute of Chemical Engineers Center for Chemical Process Safety, (CCPS).
[6]	E. Calixto “The Safety Integrity Level as Hazop Risk Consistence, the Brazilian Risk Analysis Case Study,” ESREL, Stavanger, 2007.
[7]	C. Ericson, “Fault Tree Analysis—A History,” 17th International System Safety Conference, 1999.