Reliability of industrial vessels under impact of structural fragments - Domino effect

Abstract : Industrial facilities, such as vessels under pressure, might be damaged by explosions caused by an overpressure, an exterior mechanical impact or an overheating for instance. In general, such explosions generate many structural fragments. During their flight, these projectiles may impact other facilities, such as vessels under pressure, in the vicinity. Under given conditions of pressure and mechanical damage, these impacted targets may explode and generate other sets of structural fragments, and so on. This kind of scenario corresponds to the so-called domino effect. In this document, the domino effect caused by projections that may occur in the industrial sites is analyzed with a stochastic framework. For this purpose, a global methodology is developed. The determination of the occurrence probability of this effect requires four steps : - source terms analysis : the structural fragments generated by vessels explosions have different features, i.e. number of fragments, shape, mass, departure velocity and departure angles. These features are considered as random variables. Based on the maximum entropy principle and according to existing data, the probabilistic distributions are developed for each variable. This study focuses on the case of explosions in cylindrical or spherical vessels. - Fragments motion and impact analysis : according to the fragments features at their departure, the fragment trajectory is evaluated under the effects combined from the inertia, the gravitation and the aerodynamics. The simplified approach, under the hypothesis of constant aerodynamic coefficients, allows the analytical description of the trajectory whereas the numerical solutions are obtained for the complete approach when these coefficients vary. The translational as well as rotational movements are also considered. Monte Carlo simulations are performed in order to estimate the probability of impact. Three fragments shapes are considered : end-cap, oblong end-cap and plate. Three main shapes are investigated for the targets : ellipsoidal, cylindrical and cubic vessels. - Analysis of the mechanical behaviour of the impacted targets : simplified models are developed in order to study the mechanical interaction between the fragments and the impacted targets. A complete mechanical model, including elastic-plastic behaviour and a fissure model are also proposed. This model is then implemented in the mesh-free code (Smoothed Particles Hydrodynamics). In order to estimate the rupture probability of the impacted targets, the simplified models are used, reducing therefore the calculation duration. - Domino effect occurrence : according to its residual bearing capacity and its internal physical conditions, the impacted target may give rise to a new sequence of explosions and fragments generation. This last point is not studied in this document
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Quoc Bao Nguyen. Reliability of industrial vessels under impact of structural fragments - Domino effect. Engineering Sciences. Université Paris-Est, 2009. French. <NNT : 2009PEST1057>. <tel-00551266>

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