A Framework For Synthesis Of Safety-Related Control Design To Avoid Critical Faults And Pathogenic Accidents In The Process Industries

This work proposes a framework for synthesis of safety-related control design in the process industries based on two aspects: (i) critical faults prevention and mitigation and, (ii) pathogenic accidents. The approaches found in the literature are based on the development of control solutions that use the results of hazard identification and risk analysis that were carried out to specify safety requirements to avoid or mitigate critical faults. However, the possibility of occurrence of the undesirable unobserved and/or hidden hazardous events associated with possible pathogenic accidents is not addressed. The objective of this work is to integrate the issue of analysis of pathogenic accidents into the context of synthesis of safety-related control design. Thus, a framework is proposed to: (1) address the issue of pathogenic accidents, which according to the analysis of accident investigation reports, its represent critical and / or undesirable unobserved and/or hidden events during the process of events evolution. This step is based on the analysis of the databases with missing data or incompleted obtained through accident records; (2) proposes an improvement in the hazard identification process, as it considers a systematic integration between the knowledge from experts (eg, automated HAZOP) and accident models that describe the critical and / or unwanted process of events evolution ensuring the principles of defense-in-depth and safe diagnosability; (3) address the use of safety barrier diagrams formalism to design a controlled degeneration process that will be treated locally, by each defense mechanism (eg, prevention / mitigation safety barrier), reducing the damage of the whole process; and (4) address the modeling, analysis and validation of defense algorithms with a focus on the prevention and mitigation of critical faults given a particular critical scenario using a hierarchical control structure based-approach via Petri nets formalism. Finally, the proposed framework is aligned with the requirements of the IEC 61511(2016) and IEC 61508(2010) Standards; and the models generated in Petri nets that have been validated, can be transcribed in an isomorphic way in control programs recommended by the IEC 61131-3 standard. The framework proposed was applied into an application example of an accident that occurred at isomerization unit of the British Petroleum (BP) refinery in Texas - USA.