Search

Fire is one of the most frequent accident scenarios in process facilities and it may be responsible of severe escalation scenarios: flames and heat radiation can damage equipment units, support structures, and piping with consequent loss of containment of hazardous materials. Mitigation measures are acquiring increasing importance in the design of the facilities with the goal of reducing the probability of domino effect. Passive Fire Protection Materials (PFP), properly applied, contributes to the protection of industrial equipment against accidental fires. PFP delays the heating of the protected metal and vessel contents, allowing increased time for other mitigation measures. The present contribution focuses on the measurement and modeling of some key properties for the assessment of the performance of fiber fireproofing materials. The results of the experimental activities were used to develop heat transfer models in fire-like conditions applicable to Finite Element Modeling (FEM) simulations for advanced fire and safety analysis. Particular attention was devoted to the development of a unified model for effective thermal conductivity able to account for the role of operative conditions (temperature, deformation of the fireproofing, etc.). © Copyright 2014, AIDIC Servizi S.r.l.

In the last few years, several accidental events have highlighted the importance of major manmade hazards,either accidental or deliberate by nature, within chemical and process facilities. Moreover, many plants arelocated in unstable geo-political areas, where the risk of major accidents triggered by external factors, such asterroristic attacks or sabotages, is not negligible. Hence, intentional risks should be investigated by proper riskassessments, included in the risk picture and reduced by applying adequate security measures. Because ofthe increased attention for security issues, optimal selection of security measures, by developing and applyingeconomic analyses, may become more important to reduce plants vulnerability towards intentional malevolentacts, as terroristic attacks and sabotages. Despite economic models, such as cost-benefit analysis forsupporting the decision-making process, have proved to be fundamental in many respects with regards tosafety, for instance no specific applications of cost-benefit analysis are available in the security domain, withinthe chemical and process industry context. In this paper, the role of the fundamental terms of cost-benefitanalysis within the specific framework of process-industry security is discussed, focusing on the estimation ofthe threat probability, the assessment of physical security systems costs and performances and the evaluationof the costs of the losses derived from either perspective or retrospective accidental scenarios.Furthermore, a cost-benefit analysis was applied to an illustrative case study, based on a hypotheticalsabotage to a storage tank in a process facility, leading to a major accident. The aim of the case study is toprove that the application of cost-benefit analysis provides an economic aid or criterion for selecting additionalsecurity measures in a process plant. Starting from a credible sequence of adversary’s actions, theuncertainties related to the threat probability have been accounted and realistic security measures in placehave been considered, determining the baseline physical security system performance. Therefore, threepertinent security upgrades have been proposed; for each of them the performances improvement andrealistic total costs have been calculated; the losses derived from an expected accidental scenario have beenestimated. Then, cost-benefit analysis has been applied proving that it allows defining a rational allocation ofsecurity measures. Therefore, we conclude that cost-benefit analysis may offer a relevant support in securityrisk analysis and its related decision-making process, within the chemical and process industry domain.

Process plants are particularly subjected to major accidental events, whose catastrophic escalations, triggered by external factors and characterized by very high impact and low probability, can affect both workers and population in the nearby of a process facility, as well as assets and environment. In the context of major accidents prevention, control and mitigation, safety barriers are widely employed; nevertheless, concerning their quantitative assessment, only availability is generally accounted as a measure of their performances and a frequency-based approach is applied. Recent applications have highlighted the potential of Bayesian Networks, a graphical probabilistic method, in major accidents modelling and prevention. This contribution is aimed at applying Bayesian Networks to quantitative assessment of safety barriers’ performance in the context of major accidents prevention within the process industry. The Bayesian approach will be compared with a conventional Event-Tree based one by the application to an illustrative case study, considering a major accident whose occurrence can be prevented by the action of several pertinent technical safety barriers. In the Bayesian approach, safety barriers performance has been assessed by means of specific gates, depending on barriers states and classification. An adequate number of final states has been considered. The conversion of the Event-Tree, key element of the conventional frequency-based approach, into a Bayesian Network has been performed, with the aim to test the ability of Bayesian Networks in representing possible events sequences. Indeed, the potentialities of the Bayesian approach in revising probabilities have been explored by means of two different techniques: probability updating and probability adapting. In probability updating, the information about one of the outcomes is used as an evidence, determining the most probable explanation, leading to that specific final state. In probability adapting, additional information during a time interval, in the form of accident sequence precursors, are inserted in the analysis, in purpose to revise safety barriers’ performances and final events probabilities. The results of the case study will highlight the advantages of a Bayesian approach to safety barriers’ performance assessment, proving that its application may eventually will turn into a more flexible and realistic analysis of major accidental scenarios, in comparison with conventional techniques.