1,721,128 research outputs found
Risk Analysis: a useful tool for accident prevention and emergency response
No full textRisk Analysis is a well known methodol-ogy for the assessment of the risk posed by an industrial activity. However, due to the complexities and to the uncertainties associated with some models, its effec-tiveness and use is sometimes questioned. As a consequence, it is not as widely adopted as it would deserve, with detri-ment of the safety of the plant and with a risk for the exposed population higher than might be achieved by applying ade-quate actions deriving from a proper risk management. This paper will present two such examples of application and the ad-vantages they can provid
CFD modeling of jet-fires
No full textOne of the fundamental steps in the assessment of the risk associated with industrial installations is the evaluation of the magnitude of the consequences deriving from the incidents possibly occurring in the installation.
Some of these accidental events (toxic release and explosions) can impact quite large areas, and can therefore affect a large number of the exposed population, while some others (pool fires, jet fires) are usually limited to small areas close to the site of the accident. Nonetheless, even these latter can give rise to more serious accidental events when involved in so-called “domino effects”.
In the present work Computational Fluid-Dynamics (CFD) has been used for the numerical simulation of jet fires due to the ignition of flammable materials accidentally released from storage tanks. As a matter of fact, computational fluid dynamics can provide an efficient tool for the prediction of large-scale effects taking into account all the inherent complexities associated with this phenomenon, such as gas-dynamics, multi-phase flow, turbulent mixing and combustion, radiative, convective and conductive heat transfer and so on.
The analysis allowed to predict shape and trajectory of the flame, its length and the heat transfer to the surrounding environment. The effects of wind and other ambient conditions have also been taken into consideration.
Finally, the results have been compared with some of the available empirical models and with experimental data reported in the literature, thus providing an assessment of the reliability of the metho
Risk mitigation within industrial installations: criticalities in overpressure protection systems design
No full textOne of the main causes of severe accidents in industrial installations is represented by the accidental and uncontrolled increase of the operating pressure within some process equipment or piping. When this happens without a timely and effective intervention of the control system, the possible catastrophic release of large amounts of dangerous materials is possible, with subsequent possible large scale accidents like fires, explosions or toxic cloud dispersion.
In order to avoid this kind of events, different prevention and/or protection measures are generally adopted: accurate process design, testing and maintenance, adequate instrumentation and control, and, as a last barrier, proper emergency systems, in particular an emergency relief system.
Emergency relief systems are widely adopted since long in all branches of industrial applications and even in common home devices, and they usually act safely and reliably. However some lack of understanding and a number of uncertainties are still present both in their sizing criteria and management procedures. These issues should be properly addressed in order to reach a higher level of trust and to avoid the occurrence of accidents which, even if already characterized by low values of frequency of occurrence, might give rise to very severe consequences, either for the exposed population and the environment.
The above mentioned uncertainties and lack of understanding actually relate to a range of issues. After a general overview of them, some of the most important causes of possible errors, and hence sources of possible accidents, will be addressed, with specific reference to emergency scenarios identification and relieving fluid characterization. It is expected that a more thorough knowledge of the involved phenomena will allow a more proper sizing, selection and installation of these very important safety system
Renewable energy and safety concerns: the case of secondary batteries
No full textIn the framework of the continuous effort in reducing the emissions of greenhouse gases and increasing the amount of renewable energy sources, secondary batteries are playing a more and more significant key role. In fact, on one hand, they allow to make the use of the energy derived from these sources more continuous, in contrast with the intermittent availability which often characterizes them (e.g. wind energy); on the other hand, they allow its adoption in a much wider range of application, such as in the automotive industry, where the number of electric and hybrid electric vehicles is constantly increasing.
Consequently, a strong interest is present in the availability of efficient and reliable rechargeable energy storage systems both to be inserted in the main electric network (large stationary systems and off-grid solar PV power systems), and to be installed on mobile electric vehicles. From this point of view, secondary Lithium-ion batteries represent the most promising technology available at the moment.
However, despite the wide adoption of these batteries in a number of commonly used technologies (mobile cellular phones, laptops, etc.), a number of past accidents have raised concern about their introduction in the above mentioned larger systems where even much higher powers and energy densities are required (e.g. in the aeronautical and aerospace technologies).
In the present paper, an analysis of the causes and of the final consequences of as many as possible of the failures reported in the literature will be carried out. In addition, based on the main characteristics of the energy storage systems and of the specific life cycle under consideration, an efficient risk analysis methodology framework will be suggested, with specific reference to the Li-ion battery technology. This would allow a safer use of this important technology in a wider range of practical applications, thus leading to a more efficient use of renewable energy sources and, at the same time, reducing the risk to the possibly exposed people (either workers or consumers) and to the environment
Use of environmental vulnerability indicators to assess the safety sustainability of a production process
No full textIn the present paper several parameters adopted for the assessment of the sustainability of a production process will be introduced, with specific reference to safety issues and the interaction between the process and the surrounding territory. The main accident scenarios associated with the different phases of the production process, and the corresponding impact areas have been estimated, taking into consideration all the target typologies: people, environment, structures . Then, a number of sustainability indicators have been introduced, either intrinsic to the process only, or including the characteristic of the territory. The proposed methodology has been applied to a real medium-size oil refinery and the results provide very useful information about the effectiveness of the indicators and their limit
Effetto della geometria del recipiente sulla potenza ruchiesta per la miscelazione liquido-solido
No full textMathematical modelling of BLEVE accidents
No full textA BLEVE (Boiling-Liquid Expanding-Vapour Explosion) represents one of the most dangerous accidents which can occur during the handling or storage of a low-boiling liquid. It consists in the explosive expansion of the liquid when suddenly exposed to a non-equilibrium thermo-dynamic condition. In most of the cases this means that the liquid is at a temperature higher than the boiling temperature at a newly established pressure. The expansion of the vapour produced by the evaporation can be so fast that a pressure wave is generated, possibly leading to damages to people, structures and facilities.
Many studies have been conducted to estimate the consequences of such an event (Prugh, 1988; Crowl and Louvar, 1990; CCPS 1994, 2000; Lees 2005) while less effort has been devoted to studying the dynamics of the accident before the occurrence of the explosion. Works by previous authors (Reid, 1979; Birk and Cunningham, 1994; Birk, 1995; Birk and Cunningham, 1996), describe the different phenomena involved in the process, but a comprehensive model of the accident and, above all, a simple tool describing the evolution of the physical processes simultaneously occurring during the accident, are still missing.
In the present paper the results of a mathematical description of the phenomenon are presented and compared with experimental data reported in the literatur
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