Unconfined Vapor Cloud Explosion Research Articles

The critical mass for the unconfined vapour cloud explosion of compressed and liquid hydrogen

AbstractThe (unconfined) vapour cloud explosion (VCE) is a dramatic phenomenon that generates a severe pressure wave with a high potential to damage assets and produce injuries in the far field. This definition applies also to hydrogen. Nevertheless, no clear tools and methodology have been so far developed and tested for this highly reactive gas, and even advanced numerical simulations lack validation and suffer from large uncertainties. In this view, the comprehension of the physic which subtends this dramatic phenomenon for the specific case of hydrogen is still a central issue. This paper revises some of the most adopted theories on VCE based on classical acoustic theory and models for pressure wave propagation and provides a consequence‐based, threshold (minimum) value for the critical mass of hydrogen which is needed—at a stoichiometric concentration in air—for a vapour cloud to behave as a VCE. To this regard, any non‐stoichiometric hydrogen concentration in air or lower amount of hydrogen would decrease either the flame Mach number or the total energy, thus resulting in negligible overpressure. In this sense, the effects of buoyancy, diffusivity, and weather conditions on the dispersion of hydrogen should be taken into account. The results are valid either for compressed or cryogenic liquid tanks and can be adopted for the sake of distinction between hydrogen flash fire and VCE; for the hazard analysis of hydrogen production and storage; and more in general for the risk assessment of hydrogen systems.

Blowout Prediction on a Salt Cavern Selected for a Hydrogen Storage Pilot

To prevent climate change, Europe and the world must shift to low-carbon and renewable energies. Hydrogen, as an energy vector, provides viable solutions for replacing polluting and carbon-emitting fossil fuels. Gaseous hydrogen can be stored underground and coupled with existing natural gas pipe networks. Salt cavern storage is the best suited technology to meet the challenges of new energy systems. Hydrogen storage caverns are currently operated in the UK and Texas. A preliminary risk analysis dedicated to underground hydrogen salt caverns highlighted the importance of containment losses (leaks) and the formation of gas clouds following blowouts, whose ignition may generate dangerous phenomena such as jet fires, unconfined vapor cloud explosions (UVCEs), or flashfires. A blowout is not a frequent accident in gas storage caverns. A safety valve is often set at a 30 m depth below ground level; it is automatically triggered following a pressure drop at the wellhead. Nevertheless, a blowout remains to be one of the significant accidental scenarios likely to occur during hydrogen underground storage in salt caverns. In this paper, we present modelling the subterraneous and aerial parts of a blowout on an EZ53 salt cavern fully filled with hydrogen.

Risk Assessment of the Large-Scale Hydrogen Storage in Salt Caverns

Salt caverns are accepted as an ideal solution for high-pressure hydrogen storage. As well as considering the numerous benefits of the realization of underground hydrogen storage (UHS), such as high energy densities, low leakage rates and big storage volumes, risk analysis of UHS is a required step for assessing the suitability of this technology. In this work, a preliminary quantitative risk assessment (QRA) was performed by starting from the worst-case scenario: rupture at the ground of the riser pipe from the salt cavern to the ground. The influence of hydrogen contamination by bacterial metabolism was studied, considering the composition of the gas contained in the salt caverns as time variable. A bow-tie analysis was used to highlight all the possible causes (basic events) as well as the outcomes (jet fire, unconfined vapor cloud explosion (UVCE), toxic chemical release), and then, consequence and risk analyses were performed. The results showed that a UVCE is the most frequent outcome, but its effect zone decreases with time due to the hydrogen contamination and the higher contents of methane and hydrogen sulfide.

Optimal Safe Layout of Fuel Storage Tanks Exposed to Pool Fire: One Dimensional Deterministic Modelling Approach

Fire hazard is one of the main risks associated to fuel storage tanks in petroleum and in the petrochemical industries. Such a hazard includes pool fires in the storage tanks or in the bunds, fire propagation from the source tank to target tanks both in absence and in presence of wind, and also the cascading/domino effect due to confined and unconfined vapour cloud explosion and or BLEVE associated with the source tank. In the present work, a radiation shield of flowing water has been introduced at a distance from the source fuel storage tank to prevent the domino effect originating from this source tank, under fire, to the target fuel storage tanks in a tank farm. A simple one dimensional model has been developed from the steady state energy balance to simulate the safe distances (i.e. rim–rim distance) between fuel storage tanks containing class-I fuel (e.g. gasoline), both in presence and absence of a water-shield under no-wind and cross-wind conditions. The model predictions have shown that the maximum safe inter-tank separation distance of 28.42 m is anticipated at a wind velocity of 6 m/s, compared to 16.34 m in no-wind condition, beyond which the centroid of the parallelepiped (a solid-flame geometry) falls outside the base of the tilted flame geometry causing flattening of flame and a very sluggish increase in the flame tilt angle as the inverse of the Richardson number in the presence of wind velocity vector increases. Furthermore, the present one dimensional mathematical model has also been extended to show that introduction of a water-shield with an appropriate thickness (δopt) is able to prevent the propagation of radiation heat flux under both no-wind and cross-wind conditions to a much lower distance close to 8.34 m between tanks (measured from the centre of the source tank), than those predicted from the existing empirical models; viz. Point Source model and Shokrie-Beyler’s model.

Consequences Modeling of the Akçagaz Accident through Land Use Planning (LUP) Approach

In the study, consequences analysis of Akcagaz LPG Facilities accident was conducted. The consequences analysis, modeling studies were performed by the use of EFFECTS 10.0 Software over two liquefied gas LOC (Loss of Containment) scenarios. One of the scenarios was G1: Instantaneous release corresponding to BLEVE (Boiling Liquid Expanding Vapor Explosion) and the other was G2: Release in 10 min corresponding to UVCE (Unconfined Vapor Cloud Explosion). The highest threat zone distance (1kW/m2 heat radiation distance) was determined as 1699 m, the lethal burn distance as 377 m and distance from the center cloud to threshold overpressure as 342.46 m with the G1 scenario. French, Italian and Austrian methodologies relating to LUP (Land Use Planning) context of the Seveso Directive, which was not implemented in Turkish legislation, were evaluated for BLEVE of The Akcagaz Accident. Three different modeling approaches for BLEVE including static, dynamic and rupture of the vessel were used and the results were compared to the LUP methodology. The value (height of the fire ball: 273m) closed to the actual accident situation (height of the fire ball:200-300m) was obtained with the use of the static modeling approach. The distance access to fragments of the tank was calculated as 409 m with the use of rupture of vessel modeling approach which was compatible with the actual accident value (~500m). High lethality, the beginning of lethality, irreversible effects, indirect/reversible effects radius of The Akcagaz Accident were calculated for each country LUP methodology. The determined distances with the use of static BLEVE model correlation were obtained at the highest value again. High lethality radius was determined for French and Italian as 173.37 m and 86.13 m, respectively. The LUP methodology used in France is said to be more restrictive based on the large impact distances. On the other hand, when the TOTAL specifications (GS EP SAF 253& 262) are considered, which are dependent on demand but very important, the threshold values for health effects are seen to be much more stringent.

Influence of geometrical shapes on unconfined vapor cloud explosion

The vapor cloud explosion (VCE) usually results in large financial and environmental damages. There are many methods to evaluate the consequences of VCE and one of them is the TNO Multi-Energy method (MEM). In the practical applications, the MEM has some weaknesses. For example, it is assumed that the explosion model is hemispherical, which is usually inconsistent with the actual situations. In order to examine the effect of the geometrical shapes on explosion characteristics, a constant volume of clouds with different height-width ratios and length-width ratios were studied. For the vapor cloud with a given volume (32 m3), the geometrical shapes have a great influence on the explosion overpressure, but little on the explosion temperature. When the height-width ratio is 0.5 (the corresponding geometrical shape is 4 m × 4 m × 2 m), the explosion peak overpressure reaches the maximum of 1.57 bar, which is 3.6 times of that (0.44 bar) for the 2 m × 2 m × 8 m vapor cloud. For a constant volume of clouds with the four different height-width ratios in this paper, the MEM predictions correspond to three different initial explosion strengths. As effect of the geometrical shapes on the vapor cloud explosion was not taken into account in the MEM, its predicted results have a greater deviation, especially in the far field. For the scenarios calculated in this study, the relative error for the explosion overpressure predicated in the MEM reaches 150%.

Conformity checking of LPG Transportation Trucks by Modelling and Simulation

LPG Loading /unloading site is considered as a dangerous environment of significant risk, especially during LPG transfer operations. These risks may cause catastrophic dangers such as BLEVE (Boiling Liquid Expanding Vapour Explosion), UVCE (Unconfined Vapour Cloud Explosion), etc. The site consists of a tank (RST) containing LPG and threetransfer posts. Two posts allow loading of small carrier tankers 6 tons. The other one transfer post transfer LPG contained injumbo tankers 20 tons inside the tank. The industrial site at risks chooses to demonstrate the need for a modelling-simulation approach. The aim is to check first compliance and authorization of the truck when it enters the site for loading /unloading, to verify the authorization to make the transfer, and then, to identify the driver and his training to ensure that the transfer operations are going to take place without incident. Sometimes, it may happen that Consignment Operator (CO) is busy orabsent and thus the driver operates alone without being authorized, in this case the site risks a loss of control due to a lack of resources. The modelling-simulation will be done using multi-agent systems that will present the drivers, trucks, PO and loading unloading posts as agents in order to have a model facilitating this checking.

Assessment of safety distance between components of nuclear plant and study of the vulnerabiliy of the damage caused by an explosion

This paper deals with the assessment of external explosion, resulting from accidental release of jet fuel from the large commercial airliner in the nuclear power plant (NPP). The study used three widely prediction methods such as Trinitrotoluene (TNT), multi energy (TNO) and Baker-strehow (BST) to determine the unconfined vapour cloud explosion (UVCE) overpressure within the distances of 100-1400 m from the first impact location. The containment building was taken as the reference position. The fatalities of persons and damage of structures was estimated using probit methodology. Analysis of the results shows that both reactor building and control-room will be highly damaged with risk consequences and probability, depending on the assumed position of the crash. The structures at the radial distance of 600 m may suffer major structural damage with probability ranging from 25 to 100%. The minor structural damage was observed throughout the bounds of the plant complex. The people working within 250 m radius may get affected with different fatality ranging from 28 to 100%. The findings of this study is valuable to evaluate the safety improvement needed on the NPP site and on the risk and consequences associated with the hydrocarbon fuel release/fires due to external hazards.

Influence of built-in obstacles on unconfined vapor cloud explosion

The obstacle structure in the vapor cloud has a significant influence on the gas explosion. Obstacles could not only lead to the acceleration of flame, but also they may occupy some space, thus affecting the amount of combustible gas. In this paper, a new two-step method was proposed to respectively study the effects of the obstacles amount and volume blockage ratio (VBR) on the gas explosion by using Computation Fluid Dynamic software AutoReaGas, and the obstacles in the vapor cloud were set to “Solid” instead of “Subgrid”. Based on the results and analysis, it is found that the peak overpressure and the maximum combustion rate rise with the increase of the number of obstacles for a single VBR, which indicated that the vapor cloud explosion of more obstacles was more dangerous for a single VBR. However, under a single number of obstacles, the peak overpressure and the maximum combustion rate increase firstly and then decrease as VBR increases and reach the highest at the VBR of 0.74, which indicated that the intensity of vapor cloud explosion reach a peak at a certain VBR in the middle instead of the largest. In addition, the existence and structure of obstacles have little effect on the size of explosion fireball when the size and concentration of combustible gas cloud are the same.

Assessment of the impact of an unconfined vapour cloud explosion at a major hazard facility in Melbourne close to a large proposed housing development

An increasing problem in Australia is the encroachment of residential areas into former industrial zones near to operational Major Hazard Facilities (MHFs). The consequences of scenarios such as unexpected UVCE or Unconfined Vapour Cloud Deflagration (UVCD) events can be catastrophic with significant loss of life and extensive property damage. They follow from the formation of clouds of gases and vapours resulting from accidental release of flammable liquids or pressurised heavier–than–air flammable gases and their subsequent ignition. The paper describes superimposition of the published 2005 UK Buncefield accident overpressure contours on the Gellibrand Tank Farm (GTF) in Williamstown and presents the findings of a targeted CFD modelling study. The modelling was limited by absence of data for the GTF. The purpose of the work is to emphasise the need for a full and independent quantified risk assessment study to be performed as would be required in the UK, with respect to a major housing development proposed on former nearby industrial land.

A novel method of quantitative risk assessment based on grid difference of pipeline sections

The growing demand of the urban natural gas pipeline makes the security problem of in-use pipelines attract more and more concern. Risk assessment and management for urban natural gas pipeline network is the effective way to guarantee its safety running. This paper focuses on a method for quantitative risk assessment for urban natural gas pipeline network based on grid difference of pipeline sections (GDPSs), introduces the city gas pipeline network model, defines the pipeline fatal length and analyzes gas network accident probability and accident consequence of unconfined vapor cloud explosion (UVCE), fire ball combustion, jet flame. The outcome of the quantitative method is the risk contour line and then can get corresponding protective area according to risk acceptable criteria. Finally, the proposed method is applied to an urban pipe network. It is proved that is suitable for the urban natural gas pipeline network and can provide decision support for risk management of urban natural gas pipeline network.

Risk assessment of a propane storage sphere: Maintain or decommission?

The authors were asked to assist a utility with a risk man-agement decision. Specifically, the utility was consideringwhether they should maintain or decommission an 800,000gallon propane storage sphere. The 30-year old sphere wasthe fuel storage vessel for a propane standby system. One oftheir major concerns was the shrinking buffer zone aroundtheir facility. Although the facility was originally located in aremote rural area, residential development had begun toencroach upon the facility’s buffer zone.The original analysis was based on a consideration of theoffsite consequences for a worst-case scenario. This was doneat the request of the client as it reflected their degree of riskacceptance. The consequences of two hazard scenarios wereanalyzed: an unconfined vapor cloud explosion and a Boil-ing Liquid Expanding Vapor Explosion (BLEVE). To supportthis analysis, the mechanical integrity of the sphere was eval-uated deterministically by considering the pressure vesseldesign documents, the limited nondestructive test and evalu-ation data available, and published data on typical corro-sion rates. Additional factors incorporated into the analysiswere the capabilities of the existing fire protection system, thefacility security system, and the propane unloading stationfor tank car deliveries. Finally, the economics of maintainingthe sphere versus decommissioning it were explored. Ulti-mately, the utility decided to decommission the sphere.In this article, we conduct a retrospective study using arisk-based approach. We identify a set of hazard scenariosfor the propane storage sphere, calculate the leak frequencyfor each scenario, compute the associated source term, andevaluate the consequences. The results are compared with theoriginal consequence analysis and other published hazardstudies. The implications for risk management are discussed.

BPA 공장의 메탄올 분리공정에서 위험성 평가 및 안전대책

Abstract - For a methanol separation column of the BPA (Bisphenol A) plant, HAZOP (hazard and oper-ability) assessment was performed and damage ranges were predicted from the accident scenarios for the fire and the explosion. As a result, the damage range of the jet fire was 20 m in the case of rupture of the discharge pipe (50 mm diameter) of safety valve, and that of the flash fire was 267 m in the case of catastrophic rupture. Also, the damage ranges of the unconfined vapor cloud explosion (UVCE) for the rupture of the discharge pipe and for the catastrophic rupture were 22 m and 542 m, respectively. For the worst case of release scenarios, safety measures were suggested as follows: the pressure instruments, which can detect abnormal rise of the in-ternal pressure in the methanol separation column, should be installed by the 2 out of 3 voting method in the top section of the column. Through the detection, the instuments should simultaneously shut down the control and the emergency shut-off valves. Key words : HAZOP (hazard and operability), risk assessment, fire and explosion accidents, safety meas-ures, methanol separation column, BPA (Bisphenol A)

수소가스사고의 피해범위

수소가스의 제트 누출에 의한 확산, 화재, 그리고 폭발에 의한 위험 범위를 분석하고, 안전거리 기준을 설정하기 위한 위험거리를 확산, 화재, 그리고 폭발에 대한 단순한 예측 식들을 제시하였다. 핀홀에 의한 누출과 같은 소량 수소가스 누출속도에 있어서 피해거리는 제트누출 확산에 의한 피해거리가 제트화재에 의한 피해거리보다 크며, 압력의 제곱근에 그리고 누출 홀의 직경에 비례하고 이는 수 십 미터에 이른다. 배관의 완전 파손 또는 저장 탱크의 큰 홀 발생과 같은 대량의 수소가스 누출속도에서는 제트화재의 피해거리가 개방공간의 가스운 폭발에 의한 피해거리보다 크며, 수 백 미터에 이른다. 수소충전소와 건물과의 최소이격거리 즉 안전거리 설정 기준을 대량 수소가스누출 사고시나리오를 기반으로 한다면, 도심지에 수소충전소는 안전거리 기준을 만족시키기 어려울 것이다. 따라서 대량의 수소가스 누출사고를 안전장치들을 통하여 예방하고, 안전거리 기준을 소량의 수소가스누출사고 기준으로 설정 할 수 있다. 그러나 대량누출 가능성이 있는 경우 학교와 병원 등 인구밀집 건물은 수 백 미터의 안전거리를 유지하여야 한다. An analysis was completed of the hazards distance of hydrogen accidents such as jet release, jet fire, and vapor cloud explosion(VCE) of hydrogen gas, and simplified equations have been proposed to predict the hazard distances to set up safety distance by the gas dispersion, fire, and explosion following hydrogen gas release. For a small release rate of hydrogen gas, such as from a pine-hole, the hazard distance from jet dispersion is longer than that from jet fire. The hazard distance is directly proportional to the pressure raised to a half power and to the diameter of hole and up to several tens meters. For a large release rate, such as from full bore rupture of a pipeline or a large hole of storage vessel, the hazard distance from a large jet fire is longer than that from unconfined vapor cloud explosion. The hazard distance from the fire may be up to several hundred meters. Hydrogen filling station in urban area is difficult to compliance with the safety distance criterion, if the accident scenario of large hydrogen gas release is basis for setting up the safety distance, which is minimum separation distance between the station and building. Therefore, the accident of large hydrogen gas release must be prevented by using safety devices and the safety distance may be set based on the small release rate of hydrogen gas. But if there are any possibility of large release, populated building, such as school, hospital etc, should be separated several hundred meters.

Analysis of Accidental Consequence of Butadiene Tank

Butadiene is a kind of important material in the chemical engineering, and it is inflammable and explosive. Once it leaks to the air, fire and explosion accident may happen. In the current experiment, the Butadiene tank in a chemical plant was taken as the example to analyze the potential hazards that the tank may cause. Some mathematical models, such as the UVCE（the Unconfined Vapor Cloud Explosion） and the BLEVE（the Boiling Liquid Expanding Vapor Explosion）, were used to describe the results that the hazards may lead to，so that it could provide some scientific criteria to the similar companies, and help the companies to take measures to keep away from these dangers, and reduce the casualty and loss in the end.

Safety study of the coupling of a VHTR with a hydrogen production plant

The present paper deals with specific safety issues resulting from the coupling of a nuclear reactor (very high temperature reactor, VHTR) with a hydrogen production plant (HYPP). The first part is devoted to the safety approach consisting in taking into account the safety standards and rules dedicated to the nuclear facility as well as those dedicated to the process industry. This approach enabled two main families of events to be distinguished: the so-called internal events taking place in the coupling circuit (transients, breaks in pipes and in heat exchangers) and the external events able to threat the integrity of the various equipments (in particular the VHTR containment and emergency cooling system) that could result from accidents in the HYPP. By considering a hydrogen production by means of the iodine/sulfur (IS) process, the consequences of the both families of events aforementioned have been assessed in order to provide an order of magnitude of the effects of the incidents and accidents and also in order to propose safety provisions to mitigate these effects when it is necessary. The study of transients induced by a failure of a part of the HYPP has shown the possibility to keep the part of the HYPP unaffected by the transient under operation by means of an adapted regulation set. Moreover, the time to react in case of transfer of corrosive products in the VHTR containment has been assessed as well as the thermohydraulic loading that would experience the coupling pipes in case of very fast uncoupling of the facilities aiming at avoiding an excessive pressurization of the VHTR containment. Regarding the external events, by applying a method used in the process industries, the bounding representative scenarios have been identified on the basis of their consequences but also on the basis of their occurrence frequency. The consequences of the selected bounding scenarios, calculated taking into the source-term, the atmospheric dispersion and the pressure and toxic effects induced respectively by a hydrogen unconfined vapour cloud explosion (UVCE) and a sulfur dioxide release have been assessed. The resulting safety distance of about 100 m for the UVCE is fairly acceptable in terms of performance (head loss and thermal loss) of the coupling system. However, the longer safety distance (about 1.5 km) calculated for a SO 2 release implies to foresee a long distance to settle the control room of the site or to foresee provisions able to stop very fast the SO 2 leak.

Class-2 hazmat transportation consequence assessment on surrounding population

The transportation of hazardous materials by road is an utmost necessity of the world for the societal benefits, but at the same time the activity is inherently dangerous. Incidents involving hazardous material (hazmat) cargo particularly the class-2 materials can lead to severe consequences in terms of fatalities, injuries, evacuation, property damage and environmental degradation. The rationale behind considering class-2 hazmats is that they pose the greatest danger to the people and property along the transport route because of their storage condition on the transport vessel. They are stored either in pressurized vessels or in cryogenic containers. Any external impact due to collision may cause catastrophic failure of transport vessels, known as BLEVE (Boiling Liquid Expanding Vapour Explosion) with devastating consequences. Further, any continuous release from containment may cause what is known as ‘Unconfined Vapour Cloud Explosion’ (UVCE). Historically frequency of BLEVE occurrence is of the order of 1 × 10 −6 per year or less, but other release scenarios e.g. a large vapour or liquid leaks are more probable and could also have devastating effects on the surrounding population. As such, the paper discussed various event scenarios and the consequences taking examples of a class-2.1 material (1,3 butadiene) and another class-2.3 (ammonia) hazmat. Comparative analysis suggests that per ton basis a rupture of ammonia tanker gives rise to larger impact areas and poses larger lethality risks compared to 1,3 butadiene as far as toxic effects are concerned. Besides, from fireball fatality on similar basis propylene causes higher consequence distance than LPG followed by ethylene oxide and 1,3 butadiene. The impact zone study results may be utilized as inputs for identifying the potential vulnerable area on a GIS enabled map, along a designated State highway route passing through an important industrial corridor in western India.

Route risk evaluation on class-2 hazmat transportation

Incidents involving hazardous material (hazmat) road tankers carrying class-2 materials may pose the greatest danger to the people and property along the transport route because of their storage condition on the transport vessel i.e. stored either in pressurized vessels or in cryogenic containers and lead to severe consequences in terms of fatalities, injuries, evacuation, property damage and environmental degradation. The worst case of release may result into phenomenon like Boiling Liquid Expanding Vapor Explosion (BLEVE) due to collision related catastrophic failure of vessel and an Unconfined Vapor Cloud Explosion (UVCE) due to delayed ignition following a large release. The impact zones or vulnerable areas have been identified along two designated. State highway routes passing through an important industrial corridor in Western India and mapped on a GIS enabled local map. HAMS-GPS software was used for the analysis of flammables and ALOHA for toxic hazmat consequences. The route risks are compared which have been estimated based on the population likely to be affected within the lethality impact areas created by the worst case release scenarios of different class-2 hazmats, namely LPG, ethylene oxide, propylene, 1,3-Butadiene, ammonia and chlorine, enabling proper routing decision by local authorities and also for planning emergency mitigating actions.

Influence of Vapor Cloud Shape on Temperature Field of Unconfined Vapor Cloud Explosion

In order to analyze the influence of vapor cloud shape on temperature field effect of unconfined vapor cloud explosion (UVCE) and obtain creditable prediction method of explosion temperature effect, the transient temperature fields of cylindrical and hemispherical UVCEs with same methane concentration and mass were numerically studied by computational fluid dynamics (CFD) technology. According to numerical simulation results, the concepts of UVCE's temperature-near-field and temperature-far-field were proposed, the corresponding ranges were given, and the temperature attenuation laws and differences in corresponding regions with different vapor cloud shapes were presented. Through comparing with Baker fireball model, the accuracy and visualizability in acquisition of entire temperature effect based on numerical simulation were further validated. The functional relations among maximum temperature, horizontal distance, initial temperature and vapor cloud mass in temperature-near-field and temperature-far-field were deduced by means of data fitting, respectively. These conclusions provided quantitative basis for forecast and protection of UVCE disaster.

Conclusions Drawn from the Buncefield and Naples Incidents Regarding the Utilization of Consequence Models

AbstractIn both incidents, as a result of overfilling, a very large mass of winter gasoline (mf = 300 t in Buncefield, mf = 700 t in Naples) was released, which in both cases led to a major fire of several days duration and involved 22 of a total of 41 tanks (Buncefield) and 24 of a total of 31 tanks (Naples). Whilst the Buncefield site was unconfined or only slightly confined, the Naples site had a high degree of confinement due to walls, buildings as well as a high embankment. The most important, current consequence models as well as new consequence models for the prediction of the extraordinarily high flame heights, extraordinarily high thermal radiation as well as the extraordinarily high maximum peak overpressure are described and discussed. The analysis of the Buncefield incident so far has shown that the maximum visible relative flame height lies in the region of 2.5 < (H/d)max,Bunc < 6.5 and the predicted value lies in the region 1.8 < (H/d)max,calc < 1.9. For large, black smoky fires the estimation of the critical thermal separation distance is not dependent on the total fire, but on the height of a hot, clear burning zone. In addition, for multiple tank fires there is a considerable increase in the mass burning rate, the flame height, the surface emission power as well as the thermal separation distance. With the new consequence models maximum peak overpressures for an unconfined vapor cloud explosion (UVCE) of ≈ 1.3 bar (Buncefield) and of ≈ 1.5 bar (Naples) are predicted. For a partially confined vapor cloud explosion (VCE) a maximum peak overpressure of ≈ 3 bar for a jet ignition into a corridor is predicted.