Probabilistic Risk Assessment Tool Applied in Facility Layout Optimization

The severity of several chemical incidents occurred in the recent past has been attributed to improper layout arrangement or proximity of a chemical facility to a densely populated area although this is not a new problem. To address this problem, researchers have been considering not just economic efficacy but also safety features in layout optimization. Therefore, there is still a need for a comprehensive risk assessment methodology in combination with the layout optimization formulation. Moreover, risk probability distributions should be employed to enhance understanding of overall risks and to support decision making during the design phase. The objective of this study is to incorporate a probabilistic risk assessment into the design optimization formulation. The methodology was divided in three main parts. First, a risk assessment program has been developed in MATLAB to estimate risks associated with human life losses and structural damage in a chemical plant. Analytical models for fire and explosion scenarios and toxic chemical releases were included in the program. Monte Carlo simulation was then employed to propagate uncertainties attributed to environemtal conditions and release paramenters. The proposed program generates risk maps and risk distributions at a particular point of interest in a timely manner. Second, domino effect concepts have been included in the resulting program to obtain minimal separation distances between process units necessary to prevent escalation events. These distances vary according the targeted unit type, escalation vector (overpressure or fire impigement) and the risk acceptability criteria. In the last stage, risk maps and safety distances are included in a mixed-integer linear programming (MILP) for layout optimization. The objective function is set to minimize the total capital cost associated with structural damage risk, fatality risk, pipeline interconnection, and protective devices. Individual risk criteria was applied as an additional constraint for high occupancy buildings, meaning that the overall risk for buildings such as control room or lab may not exceed this criterion. The proposed methodology has been demonstrated through a case study. It enhanced flexibility during the layout arrangement allowing the user not just include site-specific data but also the risk acceptance criteria, which reflects the company’s safety culture

Effects of Non-uniform Blockage Ratio and Obstacle Spacing on Flame Propagration in Premixed H2/O2 mixtures

PresentationMost of the current research in flame propagation and deflagration-to-detonation transition (DDT), including large and small-scale experiments, have analyzed the influence of obstacles uniformly distributed on the explosion severity. These uniform conditions are characterized by constant obstacle spacing, shape and blockage ratio (BR), and may not represent very well the layout of actual industrial facilities. Therefore, the objective of this study was to investigate the effects of varied BR in the peak overpressure and flame acceleration. A systematic analysis was conducted by varying layout parameters on a regular basis to examine what conditions favor the highest overpressure and minimal run-up distance when DDT is observed. Experiments were performed in a closed pipe with 38 mm internal diameter and an overall length to diameter ratio (L/D) equal to 73. The arrangement between two obstacles in the test vessel was varied in terms of blockage ratio (increasing, decreasing and equal) and obstacle distance (1D, 2D, and 3D). From the conditions tested, the increasing blockage ratio has a more significant impact on the overall maximum pressure and the DDT run-up distance

Analysis of Reliability Mapping in Refining Industry: Identification of Critical Regions and Interventions in Complex Production Systems

PresentationThe article aims demonstrate the importance of reliability mapping for decrease risks of shutdown and accident in critical activities. For mapping is needed to know the operational context, considering culture and deviations that between with other factors will be occasion total failure. The analyses of sociotechnical reliability need of mapping of human, operational, process and equipment reliability to occur, besides considering the system complexity and the social attractiveness, for that this way be possible the elaboration of efficient barriers. The reliability mapping demands tools in the area of social and human risk analysis, analysis of the task with the evaluation of the environment of the activities, project of work, analysis of human factors, identification of work behaviour for cultural transformation, leadership style for process safety, culture of guilt and fair culture, dynamic risk management, energy reliability and good energy practices. The Socio Technical Reliability Analyses – STRA is a more complete tool for the analyse of systems and decrease of risks. With this mapping, it is possible to identify the industrial areas that have the greatest influence on the losses occurred in the industrial context, after that it is possible use the information for make an using fault tree analyses & decision diagram. That provides for the manager makes decisions with a solid knowledge base. The methodology aims through application of tool, demonstrate the use in analyses of parameters and construction of sociotechnical reliability mapping, identifying the tasks, equipment and process that cause shutdown. After reliability assessment, it continued with barriers analysis using fault tree analyses & decision diagram tool. The conclusion is about understand different cause considering STRA and demonstrate the decision-making processes importance to take corrective and preventive actions

Analysis of the Low Perception of Risk: Causes, Consequences, and Barriers

PresentationThe principles of risk, danger, and sociability depend on cognitive limitations and the social work environment. Subjects are linked in binaries or multiples where they can establish causal relationships or influences that lead to informal rules of behavior in the workplace. A group that understands what positively influences the organizational goal of avoiding accidents and losing energy will know the importance of keeping the fundamentals of work alive. Understanding the principles is the basis for research into safe, alert, and resilient behavior. From the characterization of the principles adopted in the form of relationships, from the established standards of good practices, they present hypotheses about safe behavior. The hypotheses may indicate gaps in the difference between what is expected for a risk activity (good practices) and what is detected from the observation scenarios of this industrial routine. In the cognitive analysis based on the models that indicate perception, attention, and memory are initial stages for the construction of the mental scheme of execution of preformatted procedures or elaboration of procedures in unusual situations. A comparative analysis for a group indicates which aspects considered as priorities for decision and common sense allow a more complex preparation that requires a new concept. In the job search are the physical, cognitive (information flow and type of communication) and organizational situations that can cause human error and equipment failure. Working criteria can decrease or increase human error. This work aims to test the principles and indicate the hypotheses through the analysis of scenarios and confirm the relationships of the lack of perception of risk, with the analysis of the work station indicating which factors of performance that influence the human error. When designing interventions, it is important to suggest the influence of competence level and quality of communication tools in a stressful environment with specific leadership. Interventions depend on the type of human error, therefore, on the application of intellectual capital, operational groups for situations under stress, change of habits and educational campaigns

Effect of Uneven Obstacle Configuration on Detonation Transition in Flammable Gaseous Mixtures

Although the risks of industrial denotations in semi-open and congested geometries are often neglected by many safety practitioners, recent studies have shown that detonation onset in industrial installations might be more common than previously believed. Therefore, from the explosion safety perspective, it becomes imperative to assess industrial detonation hazards in order to ensure the robustness of explosion mitigation design, improve emergency response procedures, and provide adequate building siting evaluation. This study investigated flame acceleration and detonation onset under non-idealized obstruction characteristics. Furthermore, it also expanded the application of standard vapor cloud explosion (VCE) models to estimate the likelihood of deflagration-to-detonation transition (DDT) in industrial sites containing less reactive fuels such as propane and other light hydrocarbons. Experiments and high-fidelity numerical simulations were carried out to analyze flame propagation and detonation onset behind two solid obstructions with unequal characteristics in premixed, stoichiometric hydrogen-oxygen mixtures at 20 kPa. Four obstacle-pair characteristics were investigated: the blockage ratio variation across the obstacle pair, the opening size of the 2nd obstruction (d/λ), the opening shape, and the spacing (S) between consecutive barriers. The main findings from these studies can be summarized as follows: i) DDT occurred by the ignition of one or multiple hot-spots near the turbulent flame front; ii) the presence of an increasing BR across the obstacle pair reduces the detonation onset time significantly, and iii) the second obstacle blockage is the factor that most influenced early detonation onset, whereas the shape and opening dimension had minor or no effects. Finally, a review of current empirical VCE models was conducted to assess their capability in estimating detonation onset likelihood for large, elongated vapor clouds. Six models were evaluated in total: TNO Multi-Energy, Baker-Strehlow-Tang (BST), Congestion Assessment Method (CAM), Quest Model for Estimation of Flame Speed (QMEFS), Primary Explosion Site (PES), and Confinement Specific Correlation (CSC). Model estimations were compared with large-scale test data available in the open literature. Overall, it was demonstrated that simplified VCE methodologies could be used to indicate DDT in scales relevant for industrial applications with good accuracy after minor model modifications