Detonation Research Articles

High-velocity powder compaction: An experimental investigation, modelling, and optimization

Dynamic compaction of Aluminum powder using gas detonation forming technique was investigated. The experiments were carried out on four different conditions of total pre-detonation pressure. The effects of the initial powder mass and grain particle size on the green density and strength of compacted specimens were investigated. The relationships between the mentioned powder design parameters and the final features of specimens were characterized using Response Surface Methodology (RSM). Artificial Neural Network (ANN) models using the Group Method of Data Handling (GMDH) algorithm were also developed to predict the green density and green strength of compacted specimens. Furthermore, the desirability function was employed for multi-objective optimization purposes. The obtained optimal solutions were verified with three new experiments and ANN models. The obtained experimental results corresponding to the best optimal setting with the desirability of 1 are 2714 kg m3 and 21.5 MPa for the green density and green strength, respectively, which are very close to the predicted values.

Objetos en revolución. Hacia una (cosmo)política idiota

Las cosas son dependiendo de cómo las hagamos públicas. Este es el sugerente argumento que activan Bruno Latour y Peter Weibel en el dispositivo, de largo aliento e influencia, Making Things Public. Atmospheres of Democracy, desplegado en el ZKM de Karlsruhe en 2005. Este artículo, al modo de un re-enactment tramposo, trata de invertir el orden de los factores para alterar el producto: “lo público se hace a partir de la movilización de las cosas”. Making the Public with Things sería el contra-slogan. Para mostrar que las cosas hacen lo público se someterán a prueba de esfuerzo dos objetos, banderas y rodamientos, que, pese a que difieren entre sí en cuento a utilidades y carga simbólica, resuenan en la misma frecuencia cosmopolítica, es decir, desde el punto de vista de lo que Simondon llama su modo técnico de existencia, detonando materialidades públicas (Marres).

Impacto ambiental en suelos sometidos a explosivos en San Luis, Tolima (Colombia)

espanolEl proyecto realizado identifico la alteracion que pueden causar los explosivos en el suelo luego de realizar detonaciones controladas con pentolita, pentrita y C4 en terrenos identificados del municipio de San Luis, Tolima. Lo anterior sirve de base para proponer un procedimiento que apoye la lucha contra la contaminacion ambiental. Esto se llevo a cabo utilizando un diseno metodologico estructurado con un tipo de estudio descriptivo-experimental con enfoque mixto. Los resultados obtenidos se soportaron en un trabajo de campo que siguio los protocolos que en materia de suelos propone el Instituto Geografico Agustin Codazzi (IGAC), asi como de metodos estandar de laboratorio del Centro Tecnologico de Ambiente y Sostenibilidad de la Universidad de la Salle, con el fin de determinar las propiedades del recurso suelo, midiendo las variaciones en sus componentes antes y despues de las detonaciones de manera controlada. Las propiedades medidas fueron: materia organica, nitrogeno amoniacal y nitratos. Los resultados obtenidos en este trabajo permitieron identificar el impacto ambiental en el suelo debido a la variacion de las propiedades fisicoquimicas en este tales como materia organica y especies con nitrogeno en forma de nitratos y nitrogeno amoniacal. portuguesO projeto realizado identificou a alteracao possivelmente causada pelos explosivos no solo apos a realizacao de detonacoes controladas com pentolita, pentrita e C4 em terrenos identificados do municipio de San Luis, Tolima. O supracitado serve de base para sugerir um procedimento que suporte a luta contra a contaminacao ambiental. Isto se realizou utilizando um desenho metodologico estruturado com um tipo de estudo descritivo-experimental com uma abordagem mista. Os resultados obtidos foram alavancados por um trabalho de campo que seguiu os protocolos que, em materia de solos, propoe o Instituto Geografico Agustin Codazzi (IGAC), assim como de metodos padrao de laboratorio do Centro Tecnologico de Ambiente e Sustentabilidade da Universidade de La Salle, com o objeto de determinar as propriedades do recurso solo, medindo as variacoes em seus componentes antes e depois das detonacoes de maneira controlada. As propriedades medidas foram: materia orgânica, nitrogenio amoniacal e nitratos. Os resultados obtidos com este trabalho permiti-ram identificar o impacto ambiental no solo devido a variacao de suas propriedades fisico-quimicas, tais como materia orgânica e especies com nitrogenio em forma de nitratos e nitrogenio amoniacal. EnglishThe project undertaken identified the alteration to the land that explosives can cause after carrying out controlled detonations with pentolite, pentrite and C4 in identified lands in the municipality of San Luis, Tolima. The above serves as the basis for proposing a procedure that supports the fight against environ-mental pollution. This was carried out using a structured methodological design with a descriptive-experimental type of study which followed a mixed approach. The results obtained were supported by field work that followed the protocols proposed by the Agustin Codazzi Geographical Institute (IGAC), as well as the standard laboratory methods proposed by the Technology Centre for Environment and Sustainability from the La Salle University, in order to determine the properties of the land resources, measuring the variations in its components before and after detonations in a controlled manner. The properties measured were: organic matter, ammonia nitrogen, and nitrates. The results obtained in this project helped identify the environmental impact on the land due to the variation of the physico-chemical properties in it, such as organic matter and species with nitrogen in the form of nitrates and ammoniacal nitrogen

Monte Carlo analysis of the induced cracked zone by single-hole rock explosion

Estimating the damage induced by an explosion around a blast hole has always been a challenging issue in geotechnical engineering. It is difficult to determine an exact dimension for damage zone since many parameters are involved in the formation of failures, and there are some uncertainties lying in these parameters. Thus, the present study adopted a probabilistic approach towards this problem. First, a reliability model of the problem was established and the failure probability of induced damage was calculated. Then, the corresponding exceedance risk curve was developed indicating the relation between the failure probability and the cracked zone radius. The obtained risk curve indicated that the failure probability drops dramatically by increasing the cracked zone radius so that the probability of exceedance for any crack length greater than 4.5 m is less than 5%. Moreover, the effect of each parameter involved in the probability of failure, including blast hole radius, explosive density, detonation velocity, and tensile strength of the rock, was evaluated by using a sensitivity analysis. Finally, the impact of the decoupling ratio on the reduction of failures was investigated and the location of its maximum influence was demonstrated around the blast point.

An Analysis of Severe Vapour Cloud Explosions and Detonations in the Process Industries

Not all accidental releases of flammable gases and vapours create explosions; most releases do not find an ignition source and of those that do ignite, most of them generate low or moderate overpressure only (deflagrative combustion). However, when certain conditions are satisfied, deflagration to detonation transition (DDT) can occur followed by stable detonation. A detonation is a rare event; however, it is a worst-case accidental event. Overpressures in detonation are much higher compared to deflagration. In addition, detonation does not stop at the edge of the congestion, as in case of deflagrations, but detonation continues through the entire flammable cloud. Items within the detonating cloud are destroyed or rendered unusable.An intense vapour cloud explosion (VCE) occurred at the Buncefield fuel storage site in 2005. Extensive research into this incident revealed beyond doubt that detonation had taken place in the vapour cloud. Alternative mechanisms were considered and dismissed because they did not adequately explain the observed damage. Unique data were collected on the impact of blast on items of industrial plant, vegetation and vehicles. Combined with advances in fundamental knowledge of detonation science and large-scale tests on detonations, these new insights have allowed a comprehensive interpretation of the multitude of previous accidents involving intense vapour cloud explosions. The review identifies several past industrial accidents in which detonation was the cause of major destruction and loss of life. The new insight presented should help safety engineers to comprehend aspects of explosion hazards, to prepare and to optimise safety management procedures to minimise the detonation risk.

Experimental investigation on the pollutant dispersion driven by a condensed-phase explosion in an urban environment

The atmospheric dispersion in an urban or industrial environment is well documented in the literature. However, there is a lack of knowledge about the dispersion triggered by rapid and short phenomena such as explosions. The presented research provides information about the pollutant dispersion caused by a condensed-phase detonation in an urban environment. Experimental campaigns are conducted inside a subsonic wind tunnel at a 1:200 reduced scale. An explosion leading to the dispersion of solid particles is experimentally simulated in free field and in a straight street under a controlled neutral urban atmospheric boundary layer. Exploding-bridge-wire detonators are used to disperse a micro-talc powder. The pollutant dispersion and the overpressure caused by the explosion are measured respectively through a fast response optical measurement technique and fast response pressure sensors. The effects of key parameters on the dispersion are investigated. Two gram-scale detonators are used to analyze the effects of the explosion energy. The effect of the powder is studied through two masses of a micro-talc powder. Additionally, the transition between the predominance of the effect of the explosion and the predominance of the effect of the wind is analyzed with three wind velocities. The velocity field of the dispersion is obtained for each time step through Large Scale Particle Image Velocimetry. Similarly, the dispersion is investigated inside a T-junction to highlight the effect of an urban configuration on the pollutant release. This project provides a strong experimental database about dispersion driven by an explosion. A better understanding of the phenomenon can be used to improve industrial safety and security through more reliable predictions.

Vapour Cloud Explosions - The Evidence for Deflagration to Detonation Transition

Approximately forty years ago, it was realised that the generation of high flame speeds would result in damaging pressures being produced in vapour cloud explosions (VCEs). At the time, however, it was not clear how high flame speeds could be generated in VCE. Research in the 1970s and 1980s showed that if a vapour cloud engulfed a region of congested process pipework, the flame could accelerate to levels where damaging pressures were produced. Since that time, the accepted basis for assessing VCE hazards has been to consider congested process regions as potential locations of deflagrations, with pressure reducing as the explosion propagated away from the region. However, this was not sufficient to explain the evidence found following the Buncefield explosion in the UK (2005). The research conducted following Buncefield, the most extensive for any VCE, led to the conclusion that the incident involved a transition from a deflagration to a detonation (DDT). In reaching this conclusion, several possibilities were considered and dismissed, including a speculative explosion mechanism not previously observed that involved ignition by radiation of dust particles ahead of the flame. Taken in combination with more recent experimental studies, they indicate that DDT was not just an explanation for Buncefield, but likely has a much wider relevance. The evidence obtained from Buncefield and subsequent research supporting DDT will be reviewed.

Numerical simulation of influence of temperature disturbance on oblique detonation wave structure

Numerical simulation of influence of temperature disturbance on oblique detonation wave structure

运用从头算分子动力学模拟高温耦合爆轰压力条件下α-RDX的分解机理（英）

The initiation and subsequent decomposition mechanisms of α-RDX crystal under high temperature (3000 K) coupled with detonation pressure (34.5 GPa) were studied by ab initio molecular dynamics simulations. The crystal structure of RDX was relaxed using two types of van der Waals corrections such as PBEG06 and PBETS functional at ambient conditions. The results indicate that the PBEG06 functional is much suitable for studying α-RDX. Results show that the decomposition of α-RDX is triggered by the homolysis of the C—H bond. The DOS clearly validates that the C—H bond is broken. The elimination reaction of HONO during the decomposition is observed. The primary reactions for producing NO2, NO, N2O, N2, HONO, N2O4, H, O—H, H2O, and CO2 occur at very early stages. After the initiation of RDX, there are three different subsequent decomposition pathways. There are three main interesting subsequent decomposition paths include: (1) the C—N bond hemolysis triggers the other C—N bonds of this ring to break; (2) the dissociation of N—NO2 bond releases NO2 gas; (3) the H radical attacks the O atom to release O—H radical by forming O—H bond.

Boosting the Octane Rating of Petrol: A Review of the Trends and Impacts on the Environment

An important quality of petrol (also called motor spirit or gasoline) is its octane rating (number) which is a measure of how resistant petrol is to the abnormal combustion phenomenon known as knocking (detonation or pinging). Petrol with low octane rating will burn uncontrollably in motor engine resulting loss of power, fuel wastage, and ultimately total engine failure. At the design level, increasing the octane number of petrol meant that the engine compression ratio could be raised to maximized power output. Straight-run motor spirit is characterized by low octane number and was only suitable for the earlier engines with low compression ratios. Latter demands for more powerful engines call for increase in compression ratios of the latter designed engines. The challenge however, was that these latter engines could not run on low quality petrol (with low octane rating). Various additives were sought to boost the octane rating of petrol, and more recently refinery reconfiguration is being given much attention. This work peruses the trends towards boosting the octane quality of petrol, highlighting the impacts of these trends to the sustainability of the environment.

Transpoétiquement votre, Anthologie (1966–2016) / Transpoeticamente vostro, Antologia (1966–2016) by Hédi Bouraoui

74 BOOK REVIEWS / COMPTES RENDUS possible clue to race), at mid-desert wells. By contrast, the historic supply of West African gold to North Africa and beyond has left abundant evidence in gold coins and other artefacts. Intriguingly, we learn, some of these surviving objects of presumed West African origin are now being analysed in an attempt to define their chemical composition. Development of clear chemical signatures for this gold would mean that coins could be traced archaeologically over time and space: then some very intriguing historical trading links might be suggested, or indeed confirmed. This important and revealing study suggests overall that the Saharan historian would do well to heed the findings and wisdom of the archaeologist (and his scientific colleagues), as the archaeologist equally needs to heed the work and wisdom of the historian, to their mutual benefit. The opportunity is provided by this and the further planned volumes in the series, with their promise to continue illuminating Saharan ancient history with much-needed floodlights of new knowledge JOHN WRIGHT Richmond HÉDI BOURAOUI, TRANSPOÉTIQUEMENT VOTRE, ANTHOLOGIE (19662016 ) / TRANSPOETICAMENTE VOSTRO, ANTOLOGIA (1966-2016), ROME: EDIZIONI UNIVERSITARIE ROMANE, 2016, PP. 220. Mario Selvaggio’s bilingual anthology Transpoétiquement votre, Anthologie (1966-2016) / Transpoeticamente vostro, Antologia (1966-2016) is a carefully arranged selection of Hédi Bouraoui’s poetry spanning over a period of forty years. It contains one to three selected poems in French from most of Bouraoui’s poetry collections with a translation in Italian by Mario Selvaggio (himself a poet). Alternating between the French and Italian languages, the reader is invited to perform a constant movement not only through time, but also through the multiplicity of cultural and linguistic spaces explored. An entirely new space emerges from this type of reading, something that Bouraoui himself names the space of “l’interstice”. Indeed, central to the philosophy of his (poetry) writing is the notion of transpoétique. As Bouraoui himself explains in an interview I conducted with him in July 2011 in London, this notion is closely connected to the concept of the border, or rather the transgression of that border at the level of the cultural, political and poetic: “la transpoétique c’est le transvasement d’une poésie à une autre, le passage d’un registre à un autre, le va-et-vient entre les langues, les métaphores, les styles, les registres, les sonorités…”.1 As Bouraoui writes in his 2005 essay 1 See “Interview with Hédi Bouraoui in July 2011”, in: Bolfek-Radovani, J., Geo/graphies of Loss: Space, Place and Spatial Loss in Maghrebian and Canadian writing in French, BOOK REVIEWS / COMPTES RENDUS 75 Transpoétique, éloge du Nomadisme, the space that emerges from this approach to writing or ‘du faire poétique’ is a transucultural one: “Ce travail symbiotique, qui tisse parfois à notre insu cette nouvelle sensibilité, permet à chaque vecteur culturel d’établir des lignes de communication avec d’autres cultures tout en se transcendant, c’est-à-dire, en s’effaçant pour laisser la trace palimpseste de son processus créateur”.2 The anthology opens with two poems from the collection Musocktail (Chicago: Tower Publications, 1966) - “Création” and “Cocktail Poétique” that can be said to lay the foundation of Bouraoui’s innovative approach to writing. The ‘transpoetic’ aspects of Bouraoui’s poetics begin to take their full expression, however, in the collection Haïtuvois suivi de Antillades (Montréal: Éditions Nouvelle Optique, 1980). So, in “Les globules de ton île”, the first stanza of the poem begins with a powerful verse: “Je t’ai dans la peau HAÏTI”. As the author explains himself in the introduction, it is only within the cultural space of Haïti that he was able to recuperate the three main components of his identity: African, European and North American. The prose poem ‘Paix’ published in the collection Vers et l’envers (Toronto: ECM Press, 1982) marks the beginning of a new humanism and transcultural consciousness, as can be seen in the following verse: “La paix, c’est la véritable rencontre de l’Autre dans sa vérité; c’est l’acceptation totale de la difference”. Yet, one can witness a...

Assessment of N-oxide in a new high performance energetic tetrazine derivative on its physical, thermodynamic, sensitivity combustion and detonation performance

This work uses density functional theory (DFT) and suitable predictive methods to assess the effect of N-oxide in 1,2-bis(6-nitro-1,2,4,5-tetrazine-3-yl)diazene 1-oxide as a new heterocycle-based high performance tetrazine explosive in its thermophysical and performance properties. Important prperties are investigated, which include: (i) Physical properties: crystal density and melting point; (ii) Thermodynamic properties: condensed phase heat of formation, enthalpy of fusion, Gibbs energy of formation; (iii) Combustion performance: specific impulse; (iv) Detonation performance: velocity of detonation, detonation pressure, heat of detonation and power; (v) Sensitivity to external stimuli: impact sensivity and deflagration temperature. The predicted properties of the new compound are compared with related compound 2-bis(6-nitro-1,2,4,5-tetrazin-3-yl)diazene as well as two well-known explosives 2,4,6-Trinitro toluene (TNT), as a melt-castable explosive, and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), as a high performance explosive. It will be shown that introducing N-oxide in 1,2-bis(6-nitro-1,2,4,5-tetrazin-3-yl)diazene 1-oxide can improve its crystal density, specific impulse, heat of detonation, velocity of detonation, detonation pressure and power. The presence of N-oxide has larger effect in increasing sensitivity with respect to impact than heat sensitivity.

Synthesis and properties of 4,4’,5,5’-tetranitro-2,2’-biimidazolates: bis-semicarbazidium, bis(3-amino-1,2,4-triazolium) and bis(5-aminotetrazolium)

Ionic derivatives of 4,4’,5,5’-tetranitro-2,2’-biimidazole (TNBI) have recently been identified as interesting low sensitivity explosive compounds that combine low vulnerability to mechanical stimuli with high performance. In this work bis-semicarbazidium (1), bis(3- amino-1,2,4-triazolium) (2), bis(5-aminotetrazolium) (3) 4,4’,5,5’-tetranitro-2,2’-biimidazolates were synthesized and some of their experimental and calculated explosive properties are presented. TNBI was synthesized by nitration of 2,2’-biimidazole (BI) with nitric acid in polyphosphoric acid. Salts 1, 2, and 3 can be easily prepared in good yields and purity by reaction of TNBI with semicarbazide hydrochloride in water, 3-amino-1,2,4-triazole in methanol, and 5-aminotetrazole in diethyl ether, respectively. The compounds were characterized by NMR and vibrational spectroscopy, elemental analysis, thermal analysis (DSC, DTA/TG), and small scale safety testing (impact and friction sensitivity). The measured densities and standard enthalpy of formation, as well as calculated performance characteristics are reported. The compounds are thermally stable up to 180-210°C and insensitive to mechanical stimuli. The TNBI salts have slightly better performance than TNT with regard to calculated detonation parameters.

凸形の火炎と平面衝撃波の干渉によるデトネーション遷移過程

凸形の火炎と平面衝撃波の干渉によるデトネーション遷移過程

Experimental Research on the Effect of Aluminum Additive on the Electromagnetic Radiation in Detonation Process

Explosions of explosives can produce electromagnetic radiation signals. Based on the theory of the explosion of electromagnetic radiation, the effects of metal additives on the electromagnetic radiation produced by explosive detonation should be researched. In this paper, the electromagnetic radiation signal characteristic produced by the passivation RDX of metal additives explosion were studied by experimental. The rod-shaped antenna measurement system was used to measure the electromagnetic radiation signals generated by the different percentages of aluminum-containing passivation RDX and pure passivation RDX. The results show that the intensity of the electromagnetic radiation signal produced by the explosion is obviously increased by mixing aluminum. In the case of the same explosive mass, the signal intensity of the electromagnetic radiation generated by the explosion increases with the aluminum mass percentage is increased. When the content of aluminum is the same，with the increase of the mass of explosives，the intensity of the electromagnetic radiation signal generated by explosion also increases. The main component of the electromagnetic radiation signal frequency generated by explosives is less than 1MHz，the electromagnetic spectrum generated by explosives with the same composition is consistent.

新型含能内盐5,5′-双(3-重氮基-1,2,4-三唑)合成与表征（英）

A novel energetic inner-salt 5, 5′-bis(3-diazo-1, 2, 4-triazole)(BDTZ) was firstly designed and synthesized via two-step reactions of cyclodehydration and diazotization using oxalic acid and aminoguanidinium bicarbonate as starting materials with a total yield of 53.0%, and its structure was characterized by the means of IR spectrum, NMR and elemental analysis. Based on 3LYP/6-311G+(d, p) level, the estimated density of BDTZ is 1.73 g·cm-3, its detonation velocity is 7780 m·s-1 and the detonation pressure is 26.72 GPa. The nitrogen content of BDTZ is 74.47%, which contains no toxic heavy metals, showing that BDTZ is a green primary explosive with good detonation performance.

Effect of Aging on the Performances of TNT Based Melt-cast Explosives

To research the effect of aging on the explosive performances, the accelerated aging test of three kinds of melt-cast explosives TNT/RDX, TNT/RDX/Al and TNT/HMX/Al stockpiled for a period of time were carried out. The micro morphology and safety properties of these explosives before and after aging were studied by scanning electron microscopy and vacuum stability test (VST). The mechanical sensitivities and detonation velocities of these explosives before and after aging were tested. The results show that after aging, the color of explosives becomes dark, the volume is expanded, and the mass is decreased. The amount of evolved gas of samples is less than 2 mL/g.The thermal sensitivity of samples also has smaller change. The change in mechanical sensitivity is related to the components and aging mode of explosive. For the TNT/RDX, the detonation velocity gradually decreases with increasing the storage time, which is consistent with that of overall accelerated aging. The change trend of heat of detonation with increasing the storage time for the TNT/RDX/Al and TNT/HMX/Al is opposite, revealing that the aging mechanism may be different.

Oppau 1921: Old Facts Revisited

The likely causes for the explosion of an ammonium sulfate nitrate silo in Oppau 1921 are reviewed on the basis of publications from 1922 - 1926.Ammonium sulfate nitrate is a mixture of 2 salts: ammonium nitrate (explosive) and ammonium sulfate (inert). The explosiveness of the mixed salt is mainly determined by the ratio of these 2 salts.The influence of the mixed salt composition on the sensitivity to detonation impact had been thoroughly investigated before the accident as it was common practice to use small explosive charges to loosen the salt which had solidified during storage in the silo. About 20.000 blasting operations were carried out without any notable incident.Experiments conducted after the accident revealed that several physical parameters (particle size, density, water content, homogeneity of crystal structure) also had an influence.The introduction of a new drying process for ammonium sulfate nitrate (spray process, “Spritzverfahren”) caused changes in all these parameters resulting in a salt with increased explosiveness. In addition a dust-like fine fraction with increased ammonium nitrate content was formed which accumulated at the edge of the silo. It can be assumed that on the day of the accident at least one of the explosions for loosening the caked salt was carried out in the area of the fine fraction, thus initiating a detonation of this fine fraction and causing the detonation of further fractions with approximately “normal” nitrate content.This accident is a strong example for the need of Management of Change (MOC) procedures, which are an integral part of today´s process safety.

Improved Explosion Consequence Analysis with Combined CFD and Damage Models

The most-widely used approach to explosion consequence analysis is the classical engineering method based on the combination of TNT equivalence, scaled distances and overpressure-based damage levels. This approach rests on established and easily comprehensible elements and permits a fast assessment of explosion consequences. There are however several limitations inherent in this approach. In contrast, a simulation-based approach using computational fluid dynamics (CFD) and structural dynamics (CSD) methods permits an analysis with a high level of detail regarding both the prediction of the explosive loads and the caused damage. This comes at the cost of complex simulation models which require expert knowledge, intense validation and a high computational effort. To bridge the gap between the classical simplified approach and the CFD/CSD based methods, we have developed a specialized CFD tool, the APOLLO Blastsimulator, with a built-in library of experimentally validated damage models and blast-injury models suitable for an improved explosion consequence analysis. The high resolution CFD tool uses globally and locally adaptive Cartesian grids and includes models for TNT detonations as well as gas detonations. The built-in damage models are based on experimentally validated single-degree-of-freedom (SDOF) representations of structural components. This paper gives a brief review on the classical approaches and their limitations and an overview on the concepts used in the APOLLO Blastsimulator and the SDOF damage models. For an exemplary explosion scenario the results obtained with different explosive source and damage models are compared.

Potential for Major Explosions from Crude Oil Pipeline Releases in Varied Terrain

Crude oil is often transported by pipelines from remote production sites to refineries. Sometimes oil releases take place, caused by sabotage, corrosion or external impact. In a safety consequence study the main hazards considered are often pool, jet or flash fire. The integral models applied may give somewhat misleading hazard estimates, as a flat terrain surrounding the pipeline is assumed, and the models lack the ability to predict dense gas dispersion for calm and low wind scenarios. In a varied terrain an unrealistic large pool and following pool/flash fire, is often predicted. A major hazard often ignored is vapour cloud explosion. The fractions of volatile components in crude oil are limited. Still, as demonstrated by cascade flow experiments after the Buncefield accident, certain release mechanisms may lead to an enhanced evaporation and the likely generation of flammable vapour clouds. For an oil release it can be assumed that a pressurized oil release generating a vertical oil spray into the air, can lead to the evaporation of significant fractions of flammable vapours of propane, butane and pentane. For major pipeline releses during calm wind conditions (0-0.5 m/s) in a varied terrain, a CFD simulation study demonstrated that very large flammable vapour clouds could be generated and could fill lower lying areas of the terrain. The simulated clouds could be 5-10m deep with likely ignition sources as homes, farm houses and roads inside for 20-30 minutes. Areas with trees and dense vegetation were also inside the gas cloud, and could have led to significant flame acceleration, potentially deflagration to detonation transition (DDT) and severe consequences as seen for the Buncefield accident. For pipelines buried below the ground one possible way to prevent such a scenario will be to avoid the possibility for oil sprays upwards, for instance by covering the pipeline with plates which will remain in place during a major release. If this is not possible, vapour fences may be used to limit the gas cloud migration towards likely ignition sources or areas with dense vegetation. While such scenarios may be rare for unintended releases, the severity of the potential consequences should justify their evaluation as part of a safety study.