Cascading events triggering industrial accidents: quantitative assessment of NaTech and domino scenarios

The so called cascading events, which lead to high-impact low-frequency scenarios are rising concern worldwide. A chain of events result in a major industrial accident with dreadful (and often unpredicted) consequences. Cascading events can be the result of the realization of an external threat, like a terrorist attack a natural disaster or of “domino effect”. During domino events the escalation of a primary accident is driven by the propagation of the primary event to nearby units, causing an overall increment of the accident severity and an increment of the risk associated to an industrial installation. Also natural disasters, like intense flooding, hurricanes, earthquake and lightning are found capable to enhance the risk of an industrial area, triggering loss of containment of hazardous materials and in major accidents. The scientific community usually refers to those accidents as “NaTechs”: natural events triggering industrial accidents. In this document, a state of the art of available approaches to the modelling, assessment, prevention and management of domino and NaTech events is described. On the other hand, the relevant work carried out during past studies still needs to be consolidated and completed, in order to be applicable in a real industrial framework. New methodologies, developed during my research activity, aimed at the quantitative assessment of domino and NaTech accidents are presented. The tools and methods provided within this very study had the aim to assist the progress toward a consolidated and universal methodology for the assessment and prevention of cascading events, contributing to enhance safety and sustainability of the chemical and process industry

Report on LPG infrastructure impact at the WUI microscale

Preprin

DESIGN AND DEVELOPMENT OF A SMART ADVISORY SYSTEM FOR HAZARDOUS MATERIALS TRANSPORTATION RISK ANALYSIS VIA QUANTITATIVE APPROACHES

Safe transportation of hazardous materials is critical as it has a high potential of catastrophic accidents depending on the amount of transported product, its hazardous characteristics and the environmental conditions. Consequently, an efficient, smart and reliable intervention is essential to enhance prediction on the impacts of transportation hazards. Although various risk assessment techniques have been used in industry and regulatory bodies, they were developed for evaluating risk of hazardous materials for fixed installation cases instead of moving risk sources. This study applies the Transportation Risk Analysis (TRA), which is an extension of a well-known Quantitative Risk Analysis (QRA) technique in developing and design a Smart Advisory Systems (SAS), to determine the safest routes for transportation of hazardous materials according to Malaysia scenario

Modeling the behaviour of pressurized vessels exposed to fires through Computational Fluid Dynamics

Accidental events in the process industry can lead to the release of hazardous substances by inducing the catastrophic rupture of equipment, resulting in possible accident escalation. This type of event, in which a primary event is propagated to other units, is usually indicated as a “Domino Effect” and is typically associated to an amplification in the consequences. This type of accident may severely affect also tankers for the shipment by road or rail of hazardous substances leading to high levels of individual and social risk in highly populated areas. In the case of fires affecting tankers containing flammable pressurized liquefied gases (e.g., propane, butane, propylene, etc.), the effects of this event may lead to BLEVE (“Boiling Liquid Expanding Vapor Explosion”) and the associated fireball, with extremely severe consequences. This chain of events has actually occured several times over the years, both in chemical and process plants, but also in the framework of dangerous goods road and rail. For this reason, since the 1970, this accident scenario was investigated through large scale experiment and pilot tests, in order to test the response capabilities of the PRV (“Pressure Relief Valve”) and the effectiveness of the thermal protection such as fireproofing, installed on storage and tranport equipment. In addition, starting from the same period, researchers began to develop numerical models, which are currently increasing in complexity and capabilities due to more advanced computational resources. The aim of the present work is to demonstrate the capabilities of commercially available CFD (“Computational Fluid Dynamics”) codes for modeling thermo–fluid dynamics of tank containing pressurized liquified gases. ANSYS® FLUENT® v.14.5 software was used to set up the simulations. The CFD code allows to carry out a complete analysis of the heat transfer and the fluid motion which is generated in the stored substance due to the buoyancy forces. The heating of the vessel, due to the external fire, induces a temperature increase in the fluid, that laps the walls internally: the liquid, having higher temperature and less density, due to the gravitational field, rise again up to reach the interface with the vapour. This is the cause that leads to the establishment of the “liquid thermal stratification” in the vessel. In addition to the stratification, it is important to evaluate and predict the dynamics evolution of the liquid–vapour interface in space and time, or rather, the computation of the swelling of the liquid phase during the thermal stratification process, in order to estimate correctly the PRV opening time. These issues were addressed in the ANSYS® FLUENT® v.14.5 software through specific multiphase modelling tools, such as the Volume of Fluid model (VOF). In order to test the reliability of CFD predictions, the fluid dynamic model was validated by comparison with a large scale experimental test carried out in New Mexico (U.S.A.) in 1974. Once the CFD model has been validated, the focus of this work has shifted to the analysis of the peculiar aspect of “liquid thermal stratification” that occurs during the fire exposure, since it plays an essential role during the heat up of the tank. This phenomenon has relevant effects on the increase of pressure inside the vessel and on the energy accumulated in the liquid phase: this energy will be released at the time of catastrophic failure. The vertical temperature gradient affects the pressure build up in the vessel since the hotter liquid layer, that is placed at the liquid–vapour interface, determines the pressure reached from the tank: the above vapour is thermally overheated while the underlying liquid is subcooled. For this evaluation a sensitivity was carried out by varying the liquid filling level in the tank, the incident heat flux on the unprotected walls and geometrical parameters (thickness and diameter of the tank). The sensitivity analysis allowed extrapolating a correlation for assessing the thickness of thermally altered layer in function of the parameters mentioned above and by the pressure in the vessel. The evaluation of the thickness of this altered layer is important to improve the predictive capabilities of a lumped Model, so as not to neglect the stratification effects. Finally, the work discussed the implementation of “advanced boundary conditions” for the incident heat flux, function of the time and space. In particular, it was analysed an accidental scenario that can occur in a storage park of an industrial site: a pool fire resulting from the loss of containment of an atmospheric tank affecting a pressurized vessel. The boundary conditions, obtained using a semplified fires model for the calculation of incident heat flux for each point of the wall, were subsequently implemented on the CFD code through the construction of a dedicated User Defined Function (UDF). The results of this work demonstrated the capabilities of CFD models in supporting the analysis of complex accidental scenarios in order to supported advanced risk assessment studies. Gli eventi accidentali nell’ industria di processo possono portare al rilascio di sostanze pericolose inducendo la rottura catastrofica di apparecchiature, con conseguente possibile escalation di un incidente. Questo tipo di evento, in cui un evento primario è propagato ad altre unità, è generalmente conosciuto come “Effetto Domino” ed è tipicamente associato ad un amplificazione nelle conseguenze. Questo tipo di incidente può colpire anche serbatoi per il trasporto su strada o ferrovia di sostanze pericolose portando ad alti livelli di rischio individuale e sociale nelle zone ad elevata densità di popolazione. Nel caso di incendi che interessano serbatoi contenenti gas liquefatti in pressione (propane, butane, propylene, etc.), gli effetti di questo evento possono portare al BLEVE (“Boiling Liquid Expanding Vapor Explosion”) e alla Fireball associata, con conseguenze estremamente gravi. Questa catena di eventi si è realmente verificata varie volte nel corso degli anni, sia in impianti chimici e di processo, sia nel trasporto ferroviario e stradale di tali sostanze. Per questo motivo, fin dagli anni ’70 questo scenario incidentale è stato investigato attraverso test su larga scala e prove pilota, in modo da testare la capacità di risposta della PRV ( Valvola di Rilascio della Pressione) e l’efficacia delle protezioni termiche associate all’apparecchiatura. Inoltre, nello stesso periodo, i ricercatori iniziarono a sviluppare i primi modelli numerici, che sono in continuo incremento in complessità e capacità a causa dell’aumento delle potenze computazionali. L’obiettivo del presente lavoro è dimostrare la capacità dei codici CFD (Fluidodinamica Computazionale) disponibili in commercio per la modellazione termo–fluidodinamica di serbatoio contenenti gas liquefatto in pressione. Per effettuare le simulazioni è stato utilizzato il software commerciale Ansys®Fluent® v. 14.5. Il codice CFD permette di effettuare una completa analisi fluidodinamica dello scambio termico e del profilo di moto che è generato nel fluido stoccato a causa delle forze gravitazionali. Il riscaldamento del serbatoio, dovuto all’incendio esterno, induce un incremento di temperatura nel fluido che ne lambisce internamente le pareti: il liquido avente maggiore temperatura e minor denso, per effetto del campo gravitazionale, risale fino a raggiungere l’interfaccia con il vapore. Questa è la causa che porta all’ istituzione della stratificazione termica del liquido stoccato nel serbatoio. Oltre alla stratificazione, è importante valutare e predire l’evoluzione dinamica dell’interfaccia liquido–vapore nello spazio e nel tempo, o meglio, la computazione della dilatazione della fase liquida durante il processo di stratificazione termica, al fine di stimare correttamente il tempo di apertura della PRV. Il software Ansys®Fluent® v. 14.5 dispone di un modello multifase specifico per il monitoraggio in stato stazionario e transitorio, di qualsiasi interfaccia gas–liquido: il Volume of Fluid Model (VOF). Per dimostrare la veridicità del codice CFD, il modello fluidodinamico è stato validato attraverso il confronto con un test sperimentale su larga scala effettuato nel 1974 in New Mexico (U.S.A.). Una volta che il modello CFD è stato validato, il focus del presente lavoro si è spostato sugli aspetti peculiari della “stratificazione termica” della fase liquida durante l’esposizione al fuoco, in quanto questa riveste un ruolo essenziale nella risposta del serbatoio. Questo fenomeno ha effetti sull’aumento di pressione all’interno del serbatoio e sull’energia immagazzinata dalla fase liquida: questa energia sarà poi rilasciata al momento della rottura catastrofica. Il gradiente di temperatura verticale regola la pressione nel vessel poichè lo strato di liquido più caldo, che si colloca presso l’interfaccia liquido–vapore, determina la pressione raggiunta dal serbatoio: il vapore sovrastante è termicamente surriscaldato mentre il liquido sottostante è sottoraffreddato. Per questa valutazione è stato necessario effettuare un’analisi di sensitività andando a variare il livello di riempimento di liquido nel serbatoio, il flusso termico incidente sulle pareti non protette e i parametri geometrici (spessore e diametro del serbatoio). L’analisi di sensitività ha permesso di estrapolare una correlazione per la valutazione dello spessore della strato termicamente alterato in funzione dei parametri precedentemente citati e della pressione nel serbatoio. La valutazione di questo strato è importante per migliorare le capacità predittive di un modello a parametri concentrati, in modo da non trascurare l’effetto della stratificazione. L’ultima parte del lavoro mira all’ implemetazione di “advanced boundary conditions” per il flusso termico incidente sulle pareti del serbatoio, variabili nel tempo e nello spazio. In particolare, è stato analizzato una scenario incidentale che può verificarsi in un parco stoccaggi di un sito industriale: un pool fire derivante dalla perdita di contenimento di un serbatoio atmosferico può propagarsi e recare danni ai serbatoi pressurizzati presenti nelle vicinanze. Le condizioni al contorno, ottenute usando modelli semplificati di incendio per il calcolo del flusso termico incidente in ogni punto della parete, sono stati successivamente implementate sul codice CFD attraverso la costruzione di una dedicata User Defined Function (UFD). I risultati di questo lavoro hanno dimostrato le capacità dei modelli CFD nel sostenere l’analisi di complessi scenari incidentali pr studi di valutazione del rischio con strumenti avanzati

Modelling the behaviour of pressurized vessels exposed to fire with defective thermal protection systems

Industrialized society is linked to the transport of hazardous materials by road and rail, among other. During transportation, accidents may occur and propagate among the tankers leading to severe fires, explosion or toxic dispersions. This may increase the level of individual and social risk associated to those activities, since the transport network often crosses densely populated area. The escalation of a primary event, in this case the fire, is typically denoted as domino effect, and the triggered secondary events typically are amplified. In the framework of liquefied petroleum gas (LPG) transportation, severe fire and explosion hazards are associated to the possible catastrophic rupture of tankers, which may be induced by domino effect of accidental fires. Heat resistant coatings may protected tankers against the fire, reducing the heat load that reaches the tank shell wall and the lading. Indeed, the rupture is the result of the double effect of thermal weakening of the tank material and the increasing pressure due to LPG evaporation. However, this protection systems are not ideal and undergo defects due to both material degradation and accidental damage. Therefore, protection may be ineffective. The present work is aimed at characterizing the performance of defective coatings. The first part of the work is devoted to the characterization of past accidents occurred in the framework of road and rail transportation of hazardous materials. The ARIA and MHIDAS databases are adopted as data sources, identifying 245 road and 220 rail accidents involving hazardous materials. The analysis highlighted the importance of protecting tank from heat load to avoid the rupture and related severe scenario. For these reasons, in North America the installation of a heat resistant coating is used to protect dangerous good tankers from accidental fire exposure. In Europe, ADR and RID regulations govern transnational transport of hazardous materials by road and by rail, respectively, and still not include any section about thermal protection systems of tankers. Possible concerns related to the installation of these systems is due presence of defects that may be formed accidentally in the fireproofing layer. It is therefore important to establish what level of defect is acceptable in order to avoid the failure of tankers, in the prospective of a wider implementation of tankers fire protections in the European framework. Since large scale bonfire tests are expensive and difficult to be carried out in order to verify the thermal protections adopted, modelling the behaviour of pressurized insulated tankers when exposed to the fire is a possible solution to test the adequateness of defective protections. In order to describe the thermal behaviour of real scale LPG tanks exposed to fire, a lumped model (namely, ‘RADMOD’) and a Finite Elements Model (FEM) are developed. The models are validated against available experimental data and allow predicting the thermal behaviour of tankers with defective coating when exposed to fire, with the aim to assess the thermal protection performance. The phenomena taking place through the vessel in presence of defects are investigated and characterized, in order to reproduce the experimental data on thermal behaviour of defective thermal protection systems exposed to fire. The FEM model allows to determine the wall temperature profile and the stress distribution over the vessel, determining, in the end, a critical defect size that lead to the tank failure, with respect different fire conditions. A sensitivity analysis is performed on the FEM model in order to identify the parameters that mostly affect the heat exchanges of the system. This analysis highlights the main relevance of the flame temperature against other parameters, such as convective heat transfer coefficients and emissivity of flame and steel. The complex analysis performed by FEM model, requires high computational times, which may be prohibitive when a wide number of runs is required. The RADMOD code is a simplified lumped model, which allows to assess the behaviour, among other, of the pressure and the fluid temperature with lower, and thus acceptable, computational time. Another plus of the RADMOD model is that it can be run for a wide range of materials, substances, geometries and fire scenario, estimating a conservative but credible time to failure of the tank. The novel mathematical code for defective thermal protection system is added to the previous version of the RADMOD model, which was implemented for unprotected or completely coated tanks, thus all the phenomena related to the defect enclosure are characterised. In addition, other phenomena, already present in the RADMOD model, are revised to enhance the potentiality of the code. The comparison of results with available experimental data on medium-scale shows that the model proposed in this thesis work can reasonably predict the thermal response. The application of the modelling tool to different geometries is performed considering real-scale defects. Thus, several case-studies were defined in order to reproduce medium- and large-scale tanks varying a few parameters, such as defect size and liquid filling level, for testing the reproducibility of the new model. The results from the case studies highlight the potentiality and the flexibility of the RADMOD code in modelling the thermal response. The ultimate goal would be to apply the data collected from RADMOD code about temperature and pressure of lading, as boundary condition in the FEM model for an improved modelling of thermal behaviour of real-scale LPG tanks in fire scenarios even if there is a defective thermal protection system

Fire performance of residential shipping containers designed with a shaft wall system

seven story building made of shipping containers is planned to be built in Barcelona, Spain. This study mainly aimed to evaluate the fire performance of one of these residential shipping containers whose walls and ceiling will have a shaft wall system installed. The default assembly consisted of three fire resistant gypsum boards for vertical panels and a mineral wool layer within the framing system. This work aimed to assess if system variants (e.g. less gypsum boards, no mineral wool layer) could still be adequate considering fire resistance purposes. To determine if steel temperatures would attain a predetermined temperature of 300-350ºC (a temperature value above which mechanical properties of steel start to change significantly) the temperature evolution within the shaft wall system and the corrugated steel profile of the container was analysed under different fire conditions. Diamonds simulator (v. 2020; Buildsoft) was used to perform the heat transfer analysis from the inside surface of the container (where the fire source was present) and within the shaft wall and the corrugated profile. To do so gas temperatures near the walls and the ceiling were required, so these temperatures were obtained from two sources: (1) The standard fire curve ISO834; (2) CFD simulations performed using the Fire Dynamics Simulator (FDS). Post-flashover fire scenarios were modelled in FDS taking into account the type of fuel present in residential buildings according to international standards. The results obtained indicate that temperatures lower than 350ºC were attained on the ribbed steel sheet under all the tested heat exposure conditions. When changing the assembly by removing the mineral wool layer, fire resistance was found to still be adequate. Therefore, under the tested conditions, the structural response of the containers would comply with fire protection standards, even in the case where insulation was reduced.Postprint (published version

Wind load effect on storage tanks in Azerbaijan

Oil storage tanks play a significant role in social and economic development in Azerbaijan where is known as an oil producer country; however, there have been various cases of wind and earthquake destruction. The effect of wind disturbance on dynamic responses is analyzed, and the role of storage ratio and seismic waveform on dynamic responses under wind-earthquake activity is investigated further. The results show that the wind disruption effect has a significant impact on the dynamic responses of liquid storage tanks, especially in the empty state. When the liquid storage level is high, traditional oil storage tanks are easily destroyed by the action of a strong wind. Wind interference effect should be considered in the design and implementation of oil storage tanks, while shock absorption and strengthening steps for oil storage tanks under wind-strong earthquakes should be taken

A methodology for the assessment of domino effect scenarios due to projection of fragments generated by internal explosions of spherical vessels

The domino effect related to the projection of fragments m an Industrial environment occurs when an element of a system, such as a chemical vessel, undergoes catastrophic fragmentation as the result of an explosion The high-velocity fragments then Impact and damage neighboring systems which then leads to Other dangerous scenarios such as loss of containment, fires or even Other explosions_ Of all industrial accident scenarios, those Involving throwing of fragments have the greatest range from the accident point, well over 1 km. This process has been seen m several major accidents worldwide_ In this work, a methodology for the assessment of that kind of domino effect scenar10 was proposed_ this methodology was developed considering the three steps m which that event is divided: fragment generation, trajectory calculation and Impact damage. In the first step fragmentation patterns were studied using numerical simulations_ For this the Internal explosions of 100 stainless steel 304 vessels with spherical geometry, diameters between 1 m and 20 m and thickness m a range from 10 mm to 90 mm, were simulated With the software of material dynamics modeling ANSYS-AUTODYN.Magíster en Ingeniería QuímicaMaestrí

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

Visualizing the irradiated body and radioactive landscape in American art, 1945-1976

Looking beyond mushroom-cloud imagery, this dissertation investigates the greater effect that radiation science had on intellectually and imaginatively stimulating the visual artists László Moholy-Nagy, Ralston Crawford, Ben Shahn, and Bruce Conner, who sought knowledge of the long-range consequences of nuclear testing. Primarily concerned with the specter of the tests' aftermath rather than the spectacle of the explosions themselves, these artists explored the toxicity of radiation and ultimately discovered, I argue, that they lived in perpetual and uneasy co-existence with their subject. This study chronologically follows the course of scientific inquiry into radiological effects, from the Second World War to the height of the Cold War, beginning in the first chapter with a discussion of the role of nuclear medicine in the work of Moholy-Nagy. In postwar Chicago, he developed his earlier engagement with x-ray photographs into a deeper knowledge of atomic processes, which culminated in two paintings that suggest the healing and hazardous effects of nuclear energy. The second chapter considers Crawford's commission by Fortune magazine in 1946 to illustrate an atom-bomb test in the Pacific, for which he made several renderings based on post-blast meteorological and radiological data. The critical response to these works exposed not only the public's lack of understanding about the invisible phenomena of the bomb, but also Crawford's own loose grasp of the pertinent science. Continuing the focus on newsworthy nuclear events, the third chapter examines Shahn's portraits of J. Robert Oppenheimer, following the latter's official censure by the Atomic Energy Commission in 1954, and Shahn's paintings and drawings about a contemporaneous fallout disaster leading to the death of a Japanese fisherman. Both series link the heedless actions of scientists and their government employers to the rise of universal radiation sickness, precipitated by what Shahn perceived as mass dehumanization. The fourth and final chapter addresses Conner's long-held view that San Francisco, the city in which he lived, was radioactively contaminated and a potential target of nuclear attack. Through the representation of self-destruction in his assemblages and films, Conner mimed a cultural malaise that struck him as particularly rampant in the local environment of nuclear experimentation