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The European Directive 2004/54/EC - concerning minimum safety requirements for tunnels on the trans-European road network - requires a quantitative risk analysis for tunnels belonging to the trans-European road network and longer than 500 m, based on accident data. Strada dei Parchi S.p.A. is a company that manages a large number of road tunnels belonging to the A24 and A25 motorways in central Italy. In the course of recent modernization work on several tunnels, Strada dei Parchi S.p.A. has decided to set up and train emergency teams as a measure to further reduce the risk to tunnel users. This paper discusses the effectiveness of emergency teams during major events, in particular fire accidents. The effect of emergency teams on road tunnel risk is assessed through a quantitative model implemented by Politecnico di Milano: TRAM - Tunnel Risk Analysis Model. The TRAM risk analysis model is able to assess the societal risk for the different tunnel configurations also taking into account the presence of emergency teams. Starting from two types of initiating events, fire and DG (Dangerous Goods) release, TRAM can consider up to 18 accidental scenarios occurring in different positions inside the tunnel under investigation. The main goal of the work is to analyze the effect of the presence of emergency teams in terms of reduction of the societal risk index for a representative tunnel; the resulting F-N (Cumulated Frequency - Number of Casualties) curves are also compared with the ALARP acceptance criterion. This study is divided into three main parts. The first part of the study describes the tunnel infrastructure and the equipment of the emergency teams; the second part is related to the description of the risk model with respect to the effectiveness of the emergency teams and, finally, the third part describes an application of this model to a case study. The effectiveness of the emergency teams and, in particular, their ability to control or extinguish the fire principles is analyzed using observations made inside the tunnels of the A24/25 motorways which were recorded and provided by Strada dei Parchi S.p.A.

In industrial processes, it is not uncommon to replace regular processes and procedures with temporary ones, due to factors such as maintenance operations, breakdown of equipment or machines. All risks associated with the implementation of these temporary procedures are not analyzed, because they are applied usually for short periods. Nevertheless, the lack of proper attention levels towards the introduction of such modified procedures can lead to unfortunate and unpredictable accidents. In order to update the risk assessment document properly, fast and effective methods are needed but widely acknowledged methods are not currently available. In this work we propose the Recursive Operability Analysis – Cause Consequence Diagrams as a fast and efficient tool to include temporary and/or special procedures in an already developed risk analyses. The model was applied to the Zhong Rong Metal Products Co case study, which witnessed a severe explosion of an aluminum-alloy dust. The accident was mainly due to the implementation of a manual procedure to perform the cleaning of the bag filters present in the plant, subsequent to the breakdown of an electric motor. Results show that the update of the risk analysis can be performed in a fast and efficient way.

In industrial safety, large engulfing jet fires can cause damages and collapse of process vessels with catastrophic consequences; however, even smaller jet fires can be extremely dangerous due to their ability to induce hazardous conditions when chemical reacting systems are involved. This work investigates the ethoxylation of 1-dodecanol as a case-study to investigate the potentialities of a multiscale approach able to analyse scenarios of accidental impingement on a chemical reactor involving a jet fire. In particular, the investigated system was a Venturi tower reactor, where the reacting fluid is pumped, cooled via an external heat exchanger and sprayed from the top of the reactor together with ethylene oxide. The aim is to understand if and when the cooling power of the external heat exchanger can prevent dangerous temperature build-up in the chemical reactor. The multiscale approach used in this work involves a series of mathematical simulations aimed at evaluating the effects of different jet fires in terms of heat flux entering the Venturi reactor impinged by a jet fire. These simulations were carried out using a mathematical model developed in the framework of computational fluid dynamics (CFD). The results of such simulations were used to carry out a parametric study with a 0D model able to foresee the dynamic behaviour of the reactor impinged by the jet fire. Preliminary results confirmed the possibility of linking jet fires characteristics with the time available before dangerous conditions in the Venturi reactor occur, therefore allowing for making an estimation of the time available for activating proper mitigation measures.

The paper illustrates and describes the structure of a new quantitative model of risk analysis for road tunnels named TRAM (Tunnel Risk Analysis Model). The result of the model, in accordance with the European Directive and the Italian Legislative Decree, returns the F-N curves of societal risk, in other words functions that relate the frequency of occurrence of an accidental scenario (F) with the expected consequences in terms of potential victims (N). Starting from two types of initial events, a fire and a Dangerous Goods (DG) release, a total of 18 accidental scenarios was defined. The frequencies of occurrence of each accidental scenario is obtained using the Event Tree Analysis (ETA) technique. For each scenario, the number of fatalities, expressed in terms of deaths, is obtained by simulating the formation dynamics of the queue of vehicles, using a model able to calculate the queue length, depending on traffic, the vehicle type, as well as the closure time of the tunnel. Then, a distribution model of the potentially exposed users has been defined and coupled with an egress model. The users’ tenability is estimated on the basis of the egress model and the evolution of each accidental scenario, which is evaluated using a zone model. The proposed model can simulate each of the 18 accidental scenarios in several different positions along the tunnel, considering the impact that different tunnel infrastructure measures, equipment and management procedures can have on the users egress and on the propagation of the effects of the accidental scenarios. The model is able to consider the interdependence between these measures and their reliability in terms of their availability in an emergency situation. Finally, to validate the model, comparisons are made with the QRAM software developed by PIARC for some representative case studies. Through this model, it is possible to perform the risk analysis of a tunnel in an actual configuration and compare the expected value of damage with the corresponding one of the tunnel in a virtual configuration, as prescribed by the Italian decree compliant with the European Directive 2004/54/EC.

Thermal runaway in chemical batch and semibatch reactors is one of the major plagues in fine chemical, pharmaceutical and plastic industries. Quite often the root cause of such events is a poor knowledge of the process kinetics and thermodynamics. For this reason, accidents continue to occur with a high frequency in both European and American countries. The present work is focused on the accident occurred in 2006 at Synthron Inc. (Morganton, NC), an American company that manufactured a great variety of powder coatings and paint additives. The accident has been originated by a runaway reaction and subsequent vapor cloud explosion (that killed one worker and injured 14 others) due to a wrong scaling-up of the original process recipe. Particularly, the standard synthesis was carried out in a 1,500 gallon semibatch reactor by polymerizing liquid acrylic monomers in a high flammable solvent blend. On the day of the accident, in order to produce slightly more of the desired product, plant managers decided to scale-up the process recipe in a single larger batch. In order to perform the synthesis in the same time of the standard recipe, they also decided to load almost all of the additional monomer required into the initial reactor charge: that is, using a quasi-batch operating mode. Unfortunately, adding all the monomer in one shot, more than doubled the rate of energy release in the reactor, exceeding the cooling capacity of the equipped condenser and causing a runaway reaction. The reactor pressure increased rapidly. Solvent vapors, vented from the reactor’s rupture disc, formed a flammable cloud inside the building, found an ignition source and, finally, resulted in a violent explosion. This work presents a detailed reconstruction of the dynamics of the accident occurred at Synthron Inc. using all data collected by the U.S. Chemical Safety Board (CSB) and implementing a detailed mathematical model capable of describing monomer conversion, temperature and pressure evolution inside the reactor together with the condenser efficiency. Particularly, all constitutive equations of material and energy balance, dosing policies and mixing rules have been considered. Results arising from simulations have been found to be in good agreement with both CSB collected data and successive reconstructions.

Since the beginning of modern industry, the need to move large quantity of raw materials and products has increased continuously, matching with the improvement of the transport routes, especially public roads. With more and more trucks on world’s streets, the number of accidents has increased together with the risk connected to side events derived from the transport of hazardous materials such as fuels, acids, toxic wastes and so on. In a world where there is an increasing attention to safety, transport of hazardous materials has become one important aspect to evaluate. In order to reduce the risk, a proper choice of the transport route and a reliable simulation of the consequences of possible accidents is needed. To estimate the consequences of an accident involving flammable materials, mathematical models developed in the frame of the Computational Fluid Dynamics (CFD) are able to provide a detailed description of temperatures and species concentrations but, since they are very demanding in terms of both CPU-time and analyst skill, they are not often used for a screening evaluation of the magnitude of the consequences of an accident (as required by an ordinary shipping operation). Aim of this work is to develop a simplified mathematical model able to evaluate the effects of an accident involving the spill of a fuel (in this case study, gasoline) from a tanker in a road tunnel with a subsequent fire. The simplified model should be able to produce results comparable with those obtained using CFD models with much less CPU-time, in order to be easily implemented in a risk analysis software. To achieve this purpose, a set of differential equations has been written to describe the main phenomena involved in a tunnel fire accident; moreover, all space-time correlations have been sundered to obtain a set of equations easily solvable, therefore avoiding the time-consuming operations due to multiple numerical resolutions. The results obtained for the investigated case study using the simplified model are in fairly good agreement with those obtained from a dedicated CFD model.

Radical emulsion polymerizations are a class of fast and exothermic reactions widely diffused around the world to produce a great variety of paints and plastics. At industrial scale, repeatability of emulsion polymerization processes within narrow limits is highly desirable; this means that final solids content, particles size, emulsion viscosity and polymer average molecular weight should vary little from batch to batch. Moreover, the process should be completed in the shortest possible time and preparing a latex at the highest possible concentration to save time in production. Because of all these critical features, a reliable modelling of such processes would be very helpful at industrial scale. In this work, a detailed model of emulsion polymerization, accounting for dosing strategies, temperature control modes, volume variations, radical diffusion (inside and outside the micelle/polymer particles) and different mechanisms of particles nucleation, is developed. A non-stationary numerical approach based onto the Smith-Ewart theory has been employed to compute the average number of radicals per particle. Finally, a series of experiments on the emulsion polymerization of vinyl acetate has been carried out in an indirectly cooled semibatch reactor (RC1, 1 L, Mettler Toledo) to validate the model.

The present study focused on the consequence analysis of the severe transportation accident which took place on June 29th, 2009 in Viareggio (Italy). The accident followed the derailment of a train carrying 14 tank cars of LPG. The first tank car was punctured after the derailment releasing its entire content, that ignited causing an extended and severe flash-fire, that set on fire several houses, causing extended damage and 31 fatalities. A map of the damage following the flash-fire was obtained from the images collected after the accident. Con-ventional simplified tools for consequence assessment were used to reproduce the results, yielding to overconservative results. A computational fluid dynamic (CFD) model was also developed in order to perform a more detailed simulation. The presence of obstacles (e.g. walls, trees) and the shape of buildings around the railway line were taken into account, showing a good performance in the identification of the area affected by the flash-fire that followed the LPG release.