Comparative analysis of BLEVE mechanical energy and overpressure modelling

The mechanical effects of a BLEVE are overpressure and ejection of fragments. Although fragments reach much longer distances, peak overpressure can be very strong over a certain area. Diverse authors have proposed methodologies for the estimation of the explosion energy and peak overpressure from these type of explosions, based on different thermodynamic and physical assumptions. Here these methodologies are commented and compared. Their predictions, which show an important scattering, are checked by comparison with two sets of experimental data taken from the literature. The results obtained indicate that none of the models take into account Reid’s theory. The models based on ideal gas behaviour and constant volume energy addition, isentropic expansion and isothermal expansion give quite conservative (i.e., high) values of both energy released and overpressure, while those assuming real gas behaviour and adiabatic irreversible expansion give lower values, much closer to the real/experimental ones. The diverse uncertainty factors affecting the prediction of peak overpressure are also commented.Postprint (published version

Fire as a primary event of accident domino sequences: The case of BLEVE

The domino sequences found in major accidents have been analyzed for a large set of cases (330); the first event triggering the domino effect was an explosion or a fire, both with approximately the same contribution; the same proportion has been found when all domino effect steps were considered. Although fire effects usually reach a distance much shorter than those of an explosion, as fire is the most frequent major accident it is often found as the first step of domino sequences. This is especially true in the case of BLEVEs. Both in fixed plants and in the transportation of hazardous materials, in the event of a fire, if flames affect a vessel and the fireproofing layer has been damaged, a BLEW can occur at any moment 127 BLEW accidents involving domino effect have been analyzed. It has been found that fire is significantly more frequent than explosion, both in triggering the domino effect sequence and in intermediate steps. The time to failure can range from 1 min or even less up to several hours, an aspect that should be very important for the management of the emergency. A set of conclusions are inferred from this survey. (C) 2015 Elsevier Ltd. All rights reserved.Postprint (author's final draft

A new procedure to estimate BLEVE overpressure

Several methodologies, based on different thermodynamic assumptions and requiring substance properties and thermodynamic data, have been proposed in the literature for the prediction of the mechanical energy released by a Boiling Liquid Expanding Vapour Explosion (BLEVE) and the associated overpressure. A new method, simple and easy to use, is presented which only requires the vessel filling degree and the temperature at failure as input variables to estimate this energy. The polynomial approach has been used to obtain the equation corresponding to the diverse substances most commonly involved in these explosions. The comparison of the predicted values with experimental data shows a good agreement.Peer ReviewedPostprint (author's final draft

BLEVE: The case of water and a historical survey

After a short update of the current more accepted definition of BLEVE, the special features of water BLEVEs are analyzed. The stronger overpressure wave generated in the case of water as compared to that of other substances is justified in terms of volume change. Through a comparison with liquefied pressurized propane, three possibilities are analyzed: the simultaneous contribution of both the liquid and the preexisting vapor, the contribution of the liquid flash vaporization, and the contribution of the pre-existing vapor. Also a historical survey on a set of 202 BLEVE accidents –the largest sample of BLEVE accidents surveyed until now– is presented. LPG was the most common substances in this set of accidents. However, water and LNG (11% of water and 4% of LNG in the studied cases) have also been involved. Impact failure (44.8%) and human factor (30.3%) were the most common causes of BLEVEs. Transport, storage, process plants, and transfer were the activities in which more accidents occurred.Peer ReviewedPostprint (published version

Contribution to the study of boiling liquid expanding vapor explosions and their mechanical effects

Boiling Liquid Expanding Vapor Explosions keep occurring from time to time in process plants, storage areas and transportation by road or rail, often with severe effects. There is no doubt that a better knowledge of their main features will help in decreasing both their frequency and their consequences. This is the main aim of this thesis: the analysis of the main causes of BLEVEs, the improvement in the prediction of their effects and consequences and, finally, the definition of simple measures to be applied in the management of emergencies associated to these events. Historical analyses have been performed to determine the prevalence of BLEVEs among all major accidents in fixed plants and in the transportation of hazardous materials, as well as their main causes; the action of fire as domino effect escalation has also been studied, with special attention to the time to failure of a vessel in such a situation. The different existing methodologies for the estimation of the peak overpressure are presented and compared, and the diverse uncertainty factors affecting the prediction of BLEVE mechanical effects are analyzed. A new and relatively simple methodology has been proposed to predict the blast effects of these explosions, which allows a quick and accurate estimation. Finally, based on all these analyses, simple emergency management measures are proposed which could reduce significantly the consequences of BLEVEs on people.Encara avui, en plantes de procés, àrees d’emmagatzematge o en el transport per carretera o ferrocarril, de tant en tant es continuen produint les explosions anomenades BLEVE (Boiling Liquid Expanding Vapor Explosion, en català explosió del vapor en expansió d’un líquid bullent), sovint amb efectes molt severs. No hi ha cap mena de dubte que conèixer millor les principals característiques d’aquestes explosions permetrà reduir-ne tant la seva freqüència com les seves conseqüències. Aquesta és precisament la principal finalitat d’aquesta tesi: l’anàlisi de les causes principals de les BLEVEs, la millora en la predicció dels seus efectes i conseqüències i, finalment, la definició de mesures que siguin senzilles d’aplicar quan es produeixen emergències associades a aquest tipus d’esdeveniment. S’han dut a terme anàlisis històriques per a determinar la prevalença de les BLEVEs d’entre tots els accidents greus que es poden produir en instal·lacions fixes i durant el transport de mercaderies perilloses, així com també per a determinar-ne les causes principals. També s’ha analitzat l’acció que exerceix el foc com a element desencadenant d’efecte dominó, fent especial atenció al temps que trigarà un dipòsit en esclatar quan es veu sotmès a la seva acció. També es presenten i comparen les diverses metodologies existents per a l’estimació del pic de sobrepressió produït en una BLEVE, i s ¿analitzen els diversos factors d’incertesa que afecten la predicció dels efectes mecànics generats en una BLEVE. S’ha presentat una metodologia nova i relativament simple per predir els efectes d’aquest tipus d’explosions, que permet fer estimacions ràpides i acurades. Finalment, en base a totes aquestes anàlisis, s’han proposat mesures senzilles per a la gestió d’aquest tipus d’emergències que poden ajudar a reduir significativament les conseqüències de les BLEVEs sobre les persones.Postprint (published version

Prediction of BLEVE mechanical energy by implementation of artificial neural network

In the event of a BLEVE, the overpressure wave can cause important effects over a certain area. Several thermodynamic assumptions have been proposed as the basis for developing methodologies to predict both the mechanical energy associated to such a wave and the peak overpressure. According to a recent comparative analysis, methods based on real gas behavior and adiabatic irreversible expansion assumptions can give a good estimation of this energy. In this communication, the Artificial Neural Network (ANN) approach has been implemented to predict the BLEVE mechanical energy for the case of propane and butane. Temperature and vessel filling degree at failure have been considered as input parameters (plus vessel volume), and the BLEVE blast energy has been estimated as output data by the ANN model. A Bayesian Regularization algorithm was chosen as the three-layer backpropagation training algorithm. Based on the neurons optimization process, the number of neurons at the hidden layer was five in the case of propane and four in the case of butane. The transfer function applied in this layer was a sigmoid, because it had an easy and straightforward differentiation for using in the backpropagation algorithm. For the output layer, the number of neurons had to be one in both cases, and the transfer function was purelin (linear). The model performance has been compared with experimental values, proving that the mechanical energy of a BLEVE explosion can be adequately predicted with the Artificial Neural Network approach.Peer ReviewedPostprint (author's final draft

Essential points in the emergency management in transport accidents which can lead to a bleve-fireball

Huge amounts of hazardous materials are transported by rail and road, being from time to time involved in traffic accidents. In these cases, flammable materials such as, for example, LPG, can originate a severe accident if a loss of containment takes place: a BLEVE explosion usually followed by a fireball. This type of accident, which often follows the domino effect sequence of fire¿explosion, has caused the death of many people, including firefighters and spectators, the mechanical and thermal effects reaching significant distances. A historical survey has been performed on 167 accidents obtained from diverse databases. The results thus obtained have been used, together with the adequate mathematical models, to analyze the time to failure that can be expected and to estimate the lethality reach of the diverse effects-overpressure, ejected fragments, thermal radiation. Finally, a set of considerations concerning the safety and emergency measures that should be adopted in these accidents are commentedPostprint (published version

Analysis of methodologies and uncertainties in the prediction of BLEVE blast

Even though BLEVEs have been studied by a number of authors, there are still significant gaps in their knowledge and in the prediction of their physical effects. Diverse methodologies have been proposed to calculate the peak overpressure of the explosion, but their results sh ow an important scattering. Most of them assume a reversible, isentropic phenomenon, not at all logical for an explosion. Instead, some recent papers have assumed an irreversible process, much closer to the real phenomenon. This communication analyses these aspects, comparing the results obtaine d by applying the diverse methodologies to data obtained from a real case. The uncertainties found (v essel failure mode, directional effects) are also commented. Finally, some conclusions are derived on the best way to estimate the overpressure

Comparative analysis of BLEVE mechanical energy and overpressure modelling

The mechanical effects of a BLEVE are overpressure and ejection of fragments. Although fragments reach much longer distances, peak overpressure can be very strong over a certain area. Diverse authors have proposed methodologies for the estimation of the explosion energy and peak overpressure from these type of explosions, based on different thermodynamic and physical assumptions. Here these methodologies are commented and compared. Their predictions, which show an important scattering, are checked by comparison with two sets of experimental data taken from the literature. The results obtained indicate that none of the models take into account Reid’s theory. The models based on ideal gas behaviour and constant volume energy addition, isentropic expansion and isothermal expansion give quite conservative (i.e., high) values of both energy released and overpressure, while those assuming real gas behaviour and adiabatic irreversible expansion give lower values, much closer to the real/experimental ones. The diverse uncertainty factors affecting the prediction of peak overpressure are also commented

Fire as a primary event of accident domino sequences: The case of BLEVE

The domino sequences found in major accidents have been analyzed for a large set of cases (330); the first event triggering the domino effect was an explosion or a fire, both with approximately the same contribution; the same proportion has been found when all domino effect steps were considered. Although fire effects usually reach a distance much shorter than those of an explosion, as fire is the most frequent major accident it is often found as the first step of domino sequences. This is especially true in the case of BLEVEs. Both in fixed plants and in the transportation of hazardous materials, in the event of a fire, if flames affect a vessel and the fireproofing layer has been damaged, a BLEW can occur at any moment 127 BLEW accidents involving domino effect have been analyzed. It has been found that fire is significantly more frequent than explosion, both in triggering the domino effect sequence and in intermediate steps. The time to failure can range from 1 min or even less up to several hours, an aspect that should be very important for the management of the emergency. A set of conclusions are inferred from this survey. (C) 2015 Elsevier Ltd. All rights reserved