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Improved tools are needed to manage major accident hazard of progressively more complex offshore oil&gas systems in environmentally sensitive areas. Inherent safety principles provide a strategic opportunity to reduce major accident hazards since the early design phase, but a suitable metric to orient safer design choices is needed to apply such principles intro practice. This study aims at providing a systematic approach to the assessment of the hazard profile of alternative process designs in offshore oil & gas production facilities. A novel methodology providing a ranking of inherently safer solutions in conceptual design is described. The methodology is able to highlight the different contributors to the safety profile of the offshore oil & gas production system, linking them to the specific features of the design. The proposed approach, based on multi-criteria Key Performance Indicators (KPIs), addresses different targets (people, assets, environment) and provides a quantitative assessment of the safety score, accounting for both the possible accident consequences and their credibility. An application to a case study concerning an offshore facility for gas production is discussed to demonstrate the potential of the methodology.

The study of the protection performance provided by fibrous fireproofing materials asks for simple and reliable models for the description of their thermal behavior in accident scenarios involving industrial fires. This paper focuses on the development and validation of a physical model for effective thermal conductivity in highly porous fibrous materials used in industrial fireproofing applications. Unlike other literature models, that include several adjustable parameters, the proposed model mainly relies on physical and easily measurable properties of the material (void fraction, average fiber diameter, bulk conductivity of the phases, etc.). The model was validated against experimental data measured for three commercial passive fire protection materials. If compared with the models currently available in the literature, the proposed model shows a better correlation to the experimental data, especially at higher temperature, where radiation is the predominant phenomenon.

Alkali activated lightweight mortars, obtained by room temperature activation of coal fly ash, were studied as passive fire protection systems for steel elements. Physical, mechanical and thermal properties were investigated as a function of the compositional Si/Al molar ratio and of the amount of lightweight aggregate and foaming agent. Experimental findings were used as input data to assess their fire resistance by finite volume simulations. Results pointed out that the optimized alkali activated lightweight mortars are able to outperform alternative commercial cement-based mortars, thus representing a promising technology.

Fragment projection from equipment failure has been extensively recognized as a cause of cascading events and of severe domino scenarios. In recent years several mathematical models suitable for the quantitative assessment of risk due to domino effects and cascading events were developed and validated, but a systematic methodology for quantitative risk assessment caused by fragment projection and impact is still missing. In the present study, a step-by-step approach is proposed for the assessment of domino risk indices due to fragment projection. The approach builds on available sub-models for the quantitative assessment of fragment generation, impact and damage probabilities. Altogether, the proposed model supports a quantification of the risk due to escalation triggered by fragment impact that can be easily automated and integrated in risk assessment studies.

Industrial infrastructures, in particular those where hazardous substances are stored or handled, may be the target of malicious acts aiming at the disruption of normal operations. In the present study a toolbox of complementary and synergic techniques (Correspondence Analysis (CA), Fishbone Diagrams, Cause-Consequence Chains, Adversary Sequence Diagram, Root Cause Analysis) was applied to the in-depth analysis of physical security- and cybersecurity-related events that affected the process industry. The unprecedented original set of information obtained provides novel insights concerning these events. Clear correlations among security threats, including cyber-threats, and specific industrial sectors, as well as among the final scenarios and the different security threats from which they originate were identified by CA. In particular, vandalism resulted strongly correlated with the transportation of hazardous substances, and theft of materials with oil and gas pipelines. When considering chemical and petrochemical sites, cyber-attacks and the use of improvised explosives resulted to be the most common attack modes performed by the threat actors. Personnel and vehicle gateways resulted key elements when designing the Physical Protection System (PPS) of a facility. Insiders having the permission to enter the site bypass such controls, and were responsible of several successful attacks. Overall, the results confirm the concreteness of security-related events in the process industry and provide an original structured and detailed insight on the attack patterns experienced to date. Moreover, the results and the data obtained provide a novel set of baseline information for the application of SVA (Security Vulnerability Assessment) or SRA (Security Risk Assessment) methodologies in facilities where hazardous substances are stored or processed.

The Seveso accident triggered a virtuous process towards the development of methods, models and tools for safety and risk assessment and management. Among the more relevant results of such process was the stemming of methods and tools addressing the transportation of hazardous substances in the framework of a holistic approach to the control of major accident hazards related to dangerous substances. The present study aims at the analysis of reference procedures and tools available for the analysis of the risk in the transportation of dangerous substances in the light of the Viareggio accident. The Viareggio accident represents a paradigmatic event involving the transportation of dangerous substances. The accident, that took place in Italy in 2009, was analyzed in the perspective of current approaches to the analysis of risk in the transportation of hazardous materials. The results pointed out that the Viareggio scenario, although of particular severity, is comprised within those accounted in quantitative risk analysis.

Emerging risks may arise from process intensification and new scenarios due to the innovative technologies and higher potentialities of new LNG regasification facilities. In the conventional hazard identification process it is difficult to include new scenarios related to innovative technologies or facilities, for which limited or no operational experience is available. In the present study, a new technique for HAZard IDentification (HAZID), named Dynamic Procedure for Atypical Scenarios Identification (DyPASI), was applied to identify atypical accident scenarios in LNG terminals. The technique aims to make easier and more systematic the process of learning from early warnings and identify atypical accident scenarios otherwise disregarded by common HAZID techniques. The comparison with a survey of the accident scenarios typically considered in available Environmental Impact Assessment (EIA) studies evidences that DyPASI is a valuable tool to obtain a complete and updated overview of potential hazards in particular for new or innovative technologies, where limited operational experience is available.

Security threats on the industrial automated control systems (IACSs) are becoming a growing concern for all the industrial facilities, and in particular for those where large quantities of hazardous substances are stored or handled (e.g. Seveso sites in Europe). Remote (cyber) or physical malicious manipulations of the automated control system of Seveso sites may have consequences comparable to those of conventional major accidents due to internal causes (e.g. loss of containment of hazardous materials, fires, explosions). While consolidated approaches exist to manage and control the cybersecurity of IT and OT systems of a facility, there is an evident lack of procedures to assess the actual link between malicious manipulations of the safety and control systems and the major accidents that can be triggered. In the present study, a specific methodology (PHAROS) was developed to address the identification of major accident scenarios achievable by malicious manipulation of physical components of the plant through the control and safety instrumented systems. The methodology, which exploits a reverse-HazOp concept, also analyses the role of the existing safety barriers in contrasting the chain of events triggered by the malicious manipulation, and may support the definition of design specifications and/or possible IT protection requirements for such barriers. The methodology was applied to a demonstrative case study to understand the features of the results obtained and their potential towards the improvement of the security of the process facility.

The evaluation of the initial direction and velocity of the fragments generated in the fragmentation of a vessel due to internal pressure is an important information in the assessment of damage caused by fragments, in particular within the quantitative risk assessment (QRA) of chemical and process plants. In the present study an approach is proposed to the identification and validation of probability density functions (pdfs) for the initial direction of the fragments. A detailed review of a large number of past accidents provided the background information for the validation procedure. A specific method was developed for the validation of the proposed pdfs. Validated pdfs were obtained for both the vertical and horizontal angles of projection and for the initial velocity of the fragments.

Acid gases as hydrogen halides and sulphur oxides are typical pollutants of combustion processes. Their removal from flue gas can be performed via the injection of dry powdered sorbents, as calcium hydroxide. However, the efficiency of dry treatment methods is hindered by the limited final conversion of the solid reactant, due to an abrupt decline of its reactivity during the reaction process. Fundamental gas-solid reaction models such as the shrinking core model and the grain model are able to reproduce this phenomenon only introducing an arbitrary value of the final conversion or an adjustable value of the solid-state diffusivity of the gaseous reactant. In the present study, the conventional grain model approach was integrated with a crystallisation and fracture (CF) submodel, which links the chemical potential of nucleation to the work needed to displace the layer of solid product formed on the reaction interface. The decline in reactivity of the sorbent was accounted by a twofold effect of the product layer growth: (i) the increase of the characteristic length for solid-state diffusion, accounted for in the grain model, and (ii) the increase of the mechanical work required for nucleation as a function of product layer thickness, accounted for in the CF submodel. This approach, validated against literature data on the Ca(OH)2/HCl system, allowed reproducing the conversion of the solid reactant at different operating temperatures.

Land use planning (LUP) around industrial sites at risk of major accidents requires the application of sound approaches in the selection of credible accident scenarios. In fact, the ‘technical’ phase of LUP is based on the identification and assessment of relevant accident scenarios. An improper choice of scenarios may critically affect both the ‘technical’ phase of risk assessment and the following ‘policy’ phase concerning decision making on land-use restrictions and/or licensing. The present study introduces a procedure aimed at the systematic identification of reference accident scenarios to be used in the gathering of technical data on potential major accidents, which is a necessary step for LUP around Seveso sites. Possible accident scenarios are generated by an improved version of the MIMAH methodology (Methodology for the Identification of Major Accident Hazards). The accident scenarios are then assessed for LUP relevance considering severity, frequency and time scale criteria. The influence of prevention and mitigation barriers is also taken into account. Two applications are used to demonstrate the proposed procedure. In both case-studies, the proposed methodology proved successful in producing consistent sets of reference scenarios.

The evolution of domino scenarios triggered by fire critically depends on the presence and the performance of safety barriers that may have the potential to prevent escalation, delaying or avoiding the heat-up of secondary targets. The aim of the present study is the quantitative assessment of safety barrier performance in preventing the escalation of fired domino scenarios. A LOPA (layer of protection analysis) based methodology, aimed at the definition and quantification of safety barrier performance in the prevention of escalation was developed. Data on the more common types of safety barriers were obtained in order to characterize the effectiveness and probability of failure on demand of relevant safety barriers. The methodology was exemplified with a case study. The results obtained define a procedure for the estimation of safety barrier performance in the prevention of fire escalation in domino scenarios. © 2015 Elsevier Ltd.

Severe accidents may be triggered by the impact of floods on process and storage equipment containing hazardous substances. The present study analyses the possible damage of horizontal cylindrical equipment, either operating at atmospheric or at higher pressures. A mechanical damage model was developed and validated by available literature data on past accidents. Simplified correlations were then obtained to calculate the critical flooding conditions leading to vessel failure. A fragility model was proposed for the straightforward assessment of equipment damage probability in the framework of the quantitative risk assessment of NaTech scenarios triggered by floods. A case-study was discussed to test the potentialities of the method.

Passive fire protection by the application of fireproofing materials is a crucial safety barrier in the prevention of the escalation of fire scenarios. Fireproofing improves the capacity of process items and of support structures to maintain their structural integrity during a fire, preventing or at least delaying the collapse of structural elements. Maintenance and cost issues require, however, to apply such protection only where an actual risk of severe fire scenarios is present. Available methodologies for fireproofing application in on-shore installation do not consider the effect of jet-fires. In the present study, a risk-based methodology aimed at the protection from both pool fire and jet fire escalation was developed. The procedure addresses both the prevention of domino effect and the mitigation of asset damage due to the primary fire scenario. The method is mainly oriented to early design application, allowing the identification of fireproofing zones in the initial phases of lay-out definition.

Layout planning plays a key role in the inherent safety performance of process plants since this design feature controls the possibility of accidental chain-events and the magnitude of possible consequences. A lack of suitable methods to promote the effective implementation of inherent safety in layout design calls for the development of new techniques and methods. In the present paper, a safety assessment approach suitable for layout design in the critical early phase is proposed. The concept of inherent safety is implemented within this safety assessment; the approach is based on an integrated assessment of inherent safety guideword applicability within the constraints typically present in layout design. Application of these guidewords is evaluated along with unit hazards and control devices to quantitatively map the safety performance of different layout options. Moreover, the economic aspects related to safety and inherent safety are evaluated by the method. Specific sub-indices are developed within the integrated safety assessment system to analyze and quantify the hazard related to domino effects. The proposed approach is quick in application, auditable and shares a common framework applicable in other phases of the design lifecycle (e.g. process design). The present work is divided in two parts: Part 1 (current paper) presents the application of inherent safety guidelines in layout design and the index method for safety assessment; Part 2 (accompanying paper) describes the domino hazard sub-index and demonstrates the proposed approach with a case study, thus evidencing the introduction of inherent safety features in layout design.

The expected inherent safety performance of hydrogen storage technologies was investigated. Reference schemes were defined for alternative processes proposed for hydrogen storage, and several storage potentialities were considered. The expected safety performance of alternative process technologies was explored estimating key performance indicators based on consequence assessment and credit factors of possible loss of containment events. The results indicated that the potential hazard is always lower for the innovative technologies proposed for hydrogen storage, as metal or complex hydrides. This derived mainly from the application of the inherent safety principles of "substitution" and "moderation", since in these processes hydrogen is stored as a less hazardous hydride. However, the results also evidenced that in the perspective of an industrial implementation of these technologies, the reliability of the auxiliary equipment will be a critical issue to be addressed.