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Safety is the primary concern during the processes of storage, transportation and application of liquid hydrogen. The flammable vapor cloud formed by liquid hydrogen spill poses serious threat to life and property, and it is vital to determine safe distance (the maximum downwind distance of flammable vapor cloud to the spill source) for risk assessment and safe protection. Three-dimensional CFD simulations predicting liquid hydrogen spill in open environment are performed, and variation characteristics of safe distance with different parameters are analyzed. The wind transporting, the atmospheric turbulence, and the shear force between cloud and air are all enhanced by increased wind speed, and consequently the safe distance increases in the first phase and then decreases with wind speed. Safe distance is positively related to liquid spill rate, while the increase rate slows down gradually. A correlation that relates safe distance with wind speed and spill rate is then established for the real-time guidance in a liquid hydrogen spill accident.

Flammable gases and liquids are widely used in industry and have serious leakage hazards. When a leaking gas cloud accidentally encounters an ignition source, it results in vapor cloud explosion accidents and multiple explosions. Pressure and flow field monitoring of a primary exploding spherical gas cloud and the secondary explosion of the gas cloud were conducted using the pressure acquisition system and schlieren system, and the impact of different influencing factors on exploding were analyzed. It was found that the larger the size of the primary exploding gas cloud, the smaller the distance between the primary exploding gas cloud and the secondary explosion gas cloud, and the larger the explosion intensity of the two gas clouds. Ignition on both sides of the primary exploding gas cloud was more likely to cause a blasting effect than was central ignition. The change in sparking ignition energy had no obvious effect on explosion propagation. When multiple gas clouds were exploding, the position of the primary exploding gas cloud had a considerable influence on the chain effect of exploding. If the primary exploding gas cloud was located in the middle of multiple gas clouds, interaction occurred between the primary exploding spherical gas cloud and the secondary explosion gas cloud because the angle formed by the secondary explosion gas cloud decreased, and the explosive intensity of the exploding gas cloud was higher. When the primary exploding gas cloud was on the side, the smaller the angle, the closer the lateral gas cloud was to the flame development path of the explosive gas cloud, which increased the likelihood of a blast and increased explosion intensity.

Oil spill-induced vapor cloud explosions in a confined space can cause catastrophic consequences. In this work, investigation was conducted on the catastrophic pipeline leak, oil spill, and the resulting vapor cloud explosion accident occurring in China in 2013 by modeling analysis, field surveys, and numerical simulations. The total amount of the spilled oil was up to 2044.4 m3 due to improper disposal. The long residence time of the oil remaining in a confined space permitted the formation of explosive mixtures and caused the vapor cloud explosion. A numerical model was developed to estimate the consequence of the explosion based on volatilization testing results. The results show that the death-leading zone and the glass-breaking zone could be 18 m and 92 m, respectively, which are consistent with the field investigation. The severity of the explosion is related to the amount of the oil spill, properties of oil, and volatilization time. It is recommended that a comprehensive risk assessment be conducted to analyze the possible consequences upon oil spilling into a confined space. Prompt collection and ventilation measures should be taken immediately after the spill occurs to reduce the time for oil volatilization and prevent the mixture from reaching its explosive limit.

Characterization of the dispersion behaviors of spilled liquid hydrogen is necessary from the safety prospective. In this study, the two-phase flow of liquid hydrogen spill is predicted with the mixture multiphase model, Lee model and Realizable k-e model, and the dispersion of hydrogen vapor cloud with the atmospheric inversion layer is numerically analyzed. The inversion layer restrains the upward movement of the cloud and the mixing of the cloud with air, increasing its ground-level hydrogen concentration. The heights of the flammable cloud can be reduced by 5.71%, 10.49% and 12.86%, respectively, with the temperature lapse rates of 0.03, 0.06 and 0.10 K/m in our investigated scenarios. Besides, the restraining effect is strengthened by increasing the ground air temperature if the temperature lapse rate remains unchanged.

Micro-explosion characteristics of soybean oil droplet were investigated using high speed backlight imaging technique at ambient temperature 873 K, 923 K and 973 K. Experimental results indicate that soybean oil droplet underwent transient heating phase, micro-explosion evaporation phase, equilibrium evaporation phase, and residue evaporation phase at all the studied temperatures. The evaporation rate of equilibrium evaporation phase is increased when the temperature increased. However, a decrease for the evaporation rate of residue evaporation phase. Homogeneous and heterogeneous nucleation are observed at all temperatures, homogeneous nucleation lead to strong micro-explosion and heterogeneous nucleation lead to weak micro-explosion. Moreover, micro-explosion strength increased when the ambient increased. It was found that the micro-explosion occurred at the end of droplet evaporation, this is one of the reasons for the poor atomization characteristics of bio-oil in the engine. More importantly, the evaporation induced vapor cloud is observed at 973 K, this is mainly due to the non-isothermal condensation caused by Stefan outflow.

A gas tank is an important storage facility in chemical enterprises. When an explosion occurs, it can easily cause mass injury and death. This paper takes a 50,000 m3 gas tank as an example to analyze the consequences of an accident. First, a TNT-equivalent explosion model, quantitative risk analysis and FLACS software are used to quantitatively analyze the explosion consequences. The range of casualties caused by the vapor cloud explosion is obtained. The simulation results are then compared with the actual damage range of a gas tank explosion, and the accuracy of the simulation results is verified. Next, the personal and social risks of a gas tank are identified according to China's national standards, and it is concluded that the individual risk can be tolerated, the social risk is within the tolerable range and its area has been reduced as far as possible, and it is necessary to minimize the overall risk as much as possible. Finally, a qualitative analysis of the gas tank explosion accident is carried out and the causes of the accident are analyzed. These analyses can be used to guide practices and effectively prevent the occurrence of similar accidents.

This study describe and quantifier the effects of a virtual ammonia release accident from tanks in the industrial area of Matanzas on the population and the environment. Climate data of the study area were characterized using the Areal Locations of Hazardous Atmospheres (ALOHA) software which entails different scenarios. Predictions for three of them include: “Toxic Vapor Cloud”, “Flammable Area” and “Vapor Cloud Explosion”. The results show that the worse scenario is the toxic cloud of ammonia affecting a vast area with a dense population and causing environmental damage. Under this scenario 294 casualties should be expected.

Safety is one of the most important concerns in handling liquid hydrogen. Mixture model and Realizable k-e model are adopted to simulate the spills of liquid hydrogen in the present work. Effects of a dike around the liquid hydrogen source on vapor cloud dispersion are numerically investigated. The dike increases the hydrogen concentration near the source, and promotes the upward movement of flammable cloud thanks to the enhanced mixing with air, reducing the cloud detachment distance. The time needed for the hydrogen vapor cloud to be diluted out of hazards is largely influenced by dike size, and introducing the dike does not necessarily increase the overall hazard duration. Increasing the height to length ratio of the dike makes the near-source region exposed to high hydrogen concentration for longer hazard duration, while detachment distance reduces with the increment in dike height.

Current industry accepted methods for predicting structural blast damage to pre-engineered metal buildings (PEMBs) subject to vapor cloud explosions are quick and cost-effective to perform. However, they also tend to be overly conservative; while costs may be saved on analysis, the results may prompt unnecessary mitigation. This paper investigates the effectiveness of using more advanced computational techniques with increasing levels of refinement and sophistication to produce more realistic estimates of structural damage and corresponding human injury. The goal is to reduce the amount of over-conservatism in results and avoid the degree of costly mitigation measures that may be unnecessary. In this study, a typical PEMB is selected and assessed for selected loads using a variety of approaches of increasing analytical sophistication. The extent of building damage is determined by each method and the results are compared to demonstrate the benefit of each analytical method. The use of refined analytical methods is shown to estimate significantly less damage in the PEMB for the loads considered.

In the chemical industry, multi-hazard (toxic, flammable, and explosive) materials such as acrylonitrile are stored, transported, and processed in large quantities. A release of multi-hazard materials can simultaneously or sequentially lead to acute toxicity, fire and explosion. The spatial-temporal evolution of hazards may also result in cascading effects. In this study, a dynamic methodology called “Dynamic Graph Monte Carlo” (DGMC) is developed to model the evolution of multi-hazard accident scenarios and assess the vulnerability of humans and installations exposed to such hazards. In the DGMC model, chemical plants are modeled as a multi-agent system with three kinds of agents: hazardous installations, ignition sources, and humans while considering the uncertainties and interdependencies among the agents and their impacts on the evolution of hazards and possible escalation effects. A case study is analyzed using the DGMC methodology, demonstrating that the risk can be underestimated if the spatial-temporal evolution of multi-hazard scenarios is neglected. Vapor cloud explosion (VCEs) may lead to more severe damage than fire, and the safety distances which are implemented only based on fire hazards are not sufficient to prevent from the damage of VCEs.

If flammable gas is mixed with air, and the mixture is ignited, it is possible to form a vapor cloud explosion (VCE) which may be very destructive, and easy to trigger a domino effect of accidents because of its large extent of impact. A VCE accident may induce secondary VCE accidents, then tertiary VCE accidents, and so on. This is called the cascading effect of VCE accidents, which requires an understanding of probabilities and propagation patterns to prevent and mitigate the potential damages. In this work, a methodology based on Petri-net is proposed to model the cascading effect of VCE accidents and perform probability analysis, taking the mutual influence between the accidents into account. The deficiency in probability analysis of VCE accidents is discussed. According to the limits of states and their changes which reflect characteristics of VCE propagation, a Petri-net approach is provided for modeling and analysis of VCE cascading effect, and the modeling approach and analysis process of VCE cascading effect are presented. The application and efficacy of the methodology are demonstrated via an example of VCE accidents occurring in a gasoline tank storage area. The results show that the developed methodology can effectively reveal the propagation patterns of VCEs cascading and calculate the respective probabilities of VCE accidents.

Different kinds of derivative accidents due to reaction runaway happen frequently. The research and the prediction of such accidents and their consequences are useful in the determination of safety distances and the establishment of emergency plan. The present paper takes into account the complex components and their dynamic change in the reactor, and proposes a new quantitative analysis method for the derivative accident consequences of reaction runaway. The so-called “simulated process for derivative accidents of reaction runaway” (SPDA-RR), based on the logic diagram of accident judgement, relies on Aspen Plus to describe the process simulation. The hazard analysis of such accidents involves many mathematical models for overpressure explosion, fireball, vapor cloud explosion, harmful gas dispersion, etc. The governing parameters of the mixture used in the mathematical models, such as the component content, temperature, pressure, enthalpy and entropy, can be obtained from SPDA-RR. Furthermore, in order to analyze other cases of reaction runaway, this SPDA-RR can be easily extended by an adequate parameter adjustment.

For the example of 80 organic solvents, the method developed by the All-Russian Research Institute for Fire Protection (ARRIFP) and the Baker–Strehlow–Tang (BST) method for the prediction of vapor-cloud explosions (VCE) in enclosed spaces are compared, in terms of the specific safe volume of a building. A correlation is found between the results given by these methods. On introducing an energy correction (the ratio of the calorific value of the solvent to that of methane) and a correction factor of 1/4.47, the BST method (in the 2.5D configuration with low congestion) may be used to categorize production buildings in terms of explosion and fire safety.

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%.

The sudden rupture of a vessel containing liquefied carbon dioxide (CO 2 ) can generate a boiling liquid expanding vapor cloud explosion (BLEVE). The entire evolution process and mechanism of CO 2 BLEVE has not been fully characterized, and its influencing factors have not been systematically examined. In this study, the ejection process and microphase change process in the vessel were recorded by a high-speed camera. Within 20 ms, the pressure peaks surpassed the initial values and were considered to be the initiation of a sequence that generated a CO 2 BLEVE under certain conditions. In addition, a critical relief caliber with a diameter of 8 mm was observed under the initial burst pressures of 3 and 5 MPa. This critical relief caliber is essential for risk control and management. About 52 ms after the rupture, a heterogeneous nucleation center was formed in the liquefied CO 2 in the vessel. Subsequent nucleation center extension and swelling generated another pressure peak. The pressure peak did not surpass the initial pressure value. However, this phenomenon did not eliminate any possible connections between the heterogeneous nucleation process and the CO 2 BLEVE. If the conditions had been proper, the explosion could have happened.

Vapor cloud explosions (VCEs) can cause significant damage to nearby buildings, facilities and infrastructure with potential loss of life and significant business interruption, so the accuracy of predicting blast loads on facility buildings is critical in estimating these losses. Closely spaced buildings and process equipment outside of the congested region of a VCE provide a complicated flow field for an expanding blast wave. Their presence can channel and shield the blast, resulting in significant effects on the blast load magnitude and waveform shape. Currently, the most common way to estimate applied blast pressures resulting from VCE's is to use simplified methods that account for the total energy from the stoichiometric portion of the vapor cloud, fuel reactivity, and level of congestion and confinement, such as the TNO Multi-energy, equivalent TNT, CAM, and BST methods. These simplified tools assume an unobstructed line-of-site condition, which can overestimate and/or underestimate blast loads. This paper illustrates the use of a fast-running Computational Fluid Dynamics (CFD) approach that can account for channeling and shielding effects without having to use a turbulent combustion model. This approach provides a convenient tool for designers and process safety planners to more accurately quantify the hazard from postulated VCE hazards that include site-specific channeling and shielding effects. The accuracy of the approach is demonstrated via comparisons of CFD simulations to experimentally measured waveforms. Computed pressure and impulse are also compared to the BST predictions for unobstructed and obstructed sites.

Cylindrical tanks are widely used to store liquids in industry, where liquefied natural gas (LNG) poses a unique hazard to personnel, assets, and the surrounding community because of its flammability and cryogenic nature. There are regulations, such as National Fire Protection Association standard NFPA 59A, requiring dikes to mitigate the risk in the case of a catastrophic failure of an LNG tank. Dikes help to control pool spreading, limit vaporization, and mitigate the vapor cloud, but these effects would be undermined if the liquids overtopped the dikes. Previous studies of overtopping involved small-scale tests and a medium-scale quadrant setup. In this work, the overtopping study was further enhanced by investigating dike and tank configurations, dike materials, and liquid types through both laboratory-scale and field tests. A CFD model was developed to understand the physics, and the results of CFD simulations were compared with experimental results. The findings of this work can help to provide scie...

For the example of 80 organic solvents, the methods developed by the All-Russian Research Institute for Fire Protection (ARIFP) and the Dutch ME-TNO method for vapor cloud explosions (VCE) in enclosed spaces are compared. The comparison focuses on the safe volume of the building. The correlation between the results of the two methods is established. After introducing a correction factor of 1.42, the METNO method for third-class VCE may be used to categorize production buildings in terms of explosion safety.

A large vapor cloud explosion followed by a fire is one of the most dangerous and high consequence events that can occur at petrochemical facilities. However, one of the most devastating explosions is when a deflagration transitions to a detonation, which can travel at speeds greater than 1800 m/s and pressures greater than 18 barg. This phenomenon is called a deflagration-to-detonation transition, whereby the deflagration (flame front) continues to accelerate due to confinement or flow-induced turbulence (e.g. obstacles) and ultimately transitions at flame speeds greater than the speed of sound to a detonation. Unlike a deflagration that requires the presence of confinement or obstacles to generate high flame speeds and associated elevated overpressures, a detonation is a self-sustaining phenomenon having the shock front coupled to the combustion. Once established, the resulting detonation will continue to propagate through the vapor cloud at speeds (1800 m/s) that are of similar order as high explosives (7000–8000 m/s). While there are differences between high explosives and vapor cloud explosions (e.g. high explosives can have pressures well in excess of 100 bar), vapor cloud explosions that transition to detonations can cause significant damage due to the extremely high pressures not typically associated with gas phase explosions (>18 barg), high energy release rate per unit mass, and higher impulses due to large cloud sizes. While the likelihood of deflagration-to-detonation transitions is lower than deflagrations, they have been identified in some of the most recent large-scale explosion incidents. The consequences of deflagration-to-detonation transitions can be orders of magnitude larger than deflagrations. This article will present the results of large-scale testing conducted in a newly developed test rig of 1500 m3 gross volume involving stoichiometric, lean, and rich mixtures of propane and methane.

In the chemical process industry, flammable gases are handled or stored in many production- or storage facilities. They can cause a vapor cloud explosion (VCE) accident if they come free from their containment and there is an ignition. A knock-on effect propagation from a primary VCE to one or more subsequent VCE(s) forms the cascading effect of VCEs. A new methodology of probabilistic Petri-net (PPN), which is an extension of Petri-net, is proposed to model the cascading effect and estimate the probabilities of escalation VCEs. The definition of what is a PPN is provided and three types of probabilistic relationships based on PPN are modeled. Further, the VCE cascading analysis approach based on Petri-net reasoning (execution of transitions) is discussed. The approach is illustrated by an example analyzing a VCE cascading effect in atmospheric tanks containing gasoline.

A large vapor cloud explosion (VCE) followed by a fire is one of the most dangerous and high-consequence events that can occur at petrochemical facilities. As the size and complexity of facilities increase, designs must consider the potential adverse effects associated with vapor cloud explosions in large congested areas and understand the potential for more devastating deflagration-to-detonation transitions (DDTs) on these facilities. While the likelihood of DDTs is lower than deflagrations, they have been identified in some of the most recent large-scale explosion incidents including: 2005 Buncefield explosion, 2009 San Juan explosion, and 2009 Jaipur event. The consequences of DDTs can be orders of magnitude larger than deflagration because they have the ability to self-propagate outside the region of high congestion/confinement. Hence, it is critical to understand how a facility's geometry or equipment layout can affect explosion consequences and assist in their mitigation and/or prevention. Due to the inability to predict such devastating phenomena on the large scale, owners and designers cannot evaluate installations for risk of DDTs and provide “inherently safer” layout or mitigation measures to significantly reduce or eliminate such hazards. However, there is a lack of data at the large scale to validate the necessary design tools used to predict the risk of DDT. One of the main goals of this research project is to provide large scale DDT explosion data and validate the tools necessary to predict vapor cloud explosions in early design phase. This paper will present the results of large scale testing being conducted in a newly developed test rig of 50,000 ft3 (1500 m3) gross volume under award Subcontract 12121-6403-01 provided by the Research Partnership to Secure Energy for America (RPSEA). These tests involve evaluation of deflagrations and DDTs involving stoichiometric, lean and rich mixtures, with propane and methane fuels. The effectiveness of mitigation techniques such as solid inhibitors or deluge is evaluated for preventing DDTs.

The possibility that Deflagration to Detonation Transition (DDT) occurs in vapor cloud explosions (VCEs) in industrial accidents has generally only been recognized for very reactive fuels such as hydrogen and ethylene. Assessment of the explosion hazards and risks associated with less reactive fuels such as propane and other alkanes has generally been based around the assumption that, in practice, only a deflagration can occur. This has the benefit that the magnitude of the maximum hazard to surrounding areas is defined by the physical parameters of any congested process region and not by the extent of the vapor cloud, as would be the case if there was a sustained detonation. However, following the Buncefield incident in the UK in 2005, a considerable amount of effort was expended in explaining the major VCE that occurred. This initially involved gathering and interpreting the evidence from the incident but then extended to experimental and theoretical research over two phases and lasting five years. Further research since showed that DDT can be achieved within dense vegetation and regions of pipework with a relatively small extent (of the order of a few meters). The results from this project will be summarized, indicating why the only explanation that is consistent with all of the evidence is a DDT soon after ignition of the cloud, with a sustained detonation then propagating through the majority of the cloud. Reference will be made to other incidents where similar evidence was observed. Awareness of the significance of such evidence will be important in the investigation of future VCEs. In addition, the possibility of DDT needs to be recognized in the methodologies used to assess VCE hazards. © 2017 American Institute of Chemical Engineers Process Saf Prog 36: 292–300, 2017

In this study, the authors used a specially designed experimental device to detect the amount of diesel that evaporated at different diesel and environmental temperatures and quantify the distribution of diesel at different heights within the subsequent vapor cloud. They also examined the relationship between the total diesel concentration of the vapor cloud and the amount of diesel evaporated, the relationship between the explosive threshold of the diesel vapor cloud and the environmental temperature, and the formation of the vapor cloud. Finally, the authors investigated the conditions relevant to the formation of an explosive vapor cloud after diesel spillage.

In this article, a new concept is presented with the intent to suppress the generation of damaging overpressures during a vapor cloud explosion via triggering ignitions at additional locations within the vapor cloud immediately after the primary ignition has occurred. The resulting lower explosion overpressures would then be less damaging to buildings and their occupants. The results of early experimental work support the hypothesis underlying this new concept. © 2016 American Institute of Chemical Engineers Process Saf Prog 36: 54–61, 2017

Background: Ammonia is a commonly used chemical in the process industries. Chemical leakage is one of the main problems threatening the staff, facilities, and the environment in the process industries. Objectives: The aim of this study was to model the emission of ammonia and its consequences in the petrochemical industry. Methods: In this study, three accident scenarios of the most probable ones were chosen, including toxic vapor cloud, jet fire, and boiling liquid expanding vapor explosion (BLEVE). Then, the scenario modeling was done using areal locations of hazardous atmospheres (ALOHA) software. Results: In the first scenario, the total released ammonia is 81,316 kg. The concentration of ammonia toxic vapor is greater than 1,100 ppm (AEGL-3 region) at a distance of 1 km, which might cause death in 60 seconds. The overpressure never exceeds 3.5 psi; thus, there is no possibility of serious injury or destruction of buildings. In the third scenario, the thermal radiation of BLEVE is greater than 10 kW/m2 at a distance of 376 m, which is potentially lethal within 60 seconds. Conclusions: One of the main risks in petrochemical companies is the leakage of ammonia. The toxicity of ammonia is the most significant threat to people. The overpressure of vapor cloud explosion does not cause serious injury or of building destruction. The thermal radiation from jet fire and fireball has no effect on the city while it may cause death to the staff within 60 seconds. Thus, safety precautions should be considered to prevent the consequences of leakage accidents.

Chained explosions happened occasionally, leading to heavy casualties and huge property losses. However, the development regime of the chained explosions is unclear. Experiments of both single and two vertically distributed vapor clouds with different sizes, volume concentrations and ignition conditions were conducted. The experimental results show that the maximum overpressure generated by the primary methane/air mixture explosion increases with vapor diameter, but hardly changes with the ignition energy. The effect of ignition position on chained explosions is significant since the development trajectory of the primary explosion varies with the ignition position. The secondary explosion is more likely to be triggered in the case of ignition at the center of the primary vapor cloud. Because of the enhanced ignition and turbulence induced by the primary explosion, the maximum overpressure and rate of pressure rise of the secondary explosion are larger than that of the primary explosion and increase with a decrease in the separation distance between the two vapor clouds. In addition, the development of the explosion flame for the secondary explosion induced by a primary explosion is asymmetric due to the uncertain ignition point.

The oil industry operates installations and processes with important quantities of flammable substances within a wide range of pressures and temperatures. A particular hazard for this type of installations is an accidental release of a large quantity of flammable material resulting in a devastating vapor cloud explosion. Extensive research was conducted to assess the efficiency of chemicals for inhibition of flames. Especially alkali metal compounds (especially carbonates and bicarbonates of sodium and potassium) have shown to be one of the more efficient flame inhibitor species. In this paper, the principles of flame inhibition by alkali metal compounds are briefly explained. Based on these principles, a practical implementation of an industrial system for chemical inhibition of vapor cloud explosions is discussed. This implementation is based on the use of dry powders of carbonates and bicarbonates of sodium and potassium as flame inhibitor species. The efficiency of the final design of the inhibition system was tested and confirmed on a very large scale in Vapor Cloud Explosion tests in California (US) in September 2016. Several projects in TOTAL were identified in which the VCE inhibition technology is implemented (new cracker units in Daesan (South-Korea) and in Port Arthur (United States)).

Storage tank separation distance, which considerably affects forestalling and mitigating accident consequences, is principally determined by thermal radiation modeling and meeting industry safety requirements. However, little is known about the influence of separation distance on gas dispersion or gas explosion, which are the most destructive types of accidents in industrial settings. This study evaluated the effect of separation distance on gas dispersion and vapor cloud explosion in a storage tank farm. Experiments were conducted using Flame Acceleration Simulator, an advanced computational fluid dynamics software program. Codes governing the design of separation distances in China and the United States were compared. A series of geometrical models of storage tanks with various separation distances were established. Overall, increasing separation distance led to a substantial reduction in vapor cloud volume and size in most cases. Notably, a 1.0 storage diameter separation distance appeared to be optimal. In terms of vapor cloud explosion, a greater separation distance had a marked effect on mitigating overpressure in gas explosions. Therefore, separation distance merited consideration in the design of storage tanks to prevent gas dispersion and explosion.

This study is related to consequence analyses of accidental natural gas explosions and used to assess the risk of the long-distance transmission pipeline system. In these consequence analyses, it is indispensable to adequately predict the blast wave propagation of gas vapor cloud explosions (VCEs) in open space. In this study, a new theoretical prediction method for natural gas VCEs in open space was developed and a full-scale experiment involving explosion in a natural gas pipeline was carried out. The predictions by the improved theoretical method agreed well with the results of the full-scale experiment. On the basis of damage criteria, to demonstrate the probability and potential damage range to humans and surroundings, risk analysis of this case was performed on the PHAST simulator. We conclude that a nearly 100% fatality is expected in a blast wave zone of within 160 m, while the explosions made serious effects on the surrounding construction, causing all of the buildings to collapse with the radial...

Gas/vapor cloud explosions and fires are responsible for most of the largest property loss events worldwide in the hydrocarbon industry. Motivation for this article is to summarize explosion pressure caused by corrosive gases/vapors in terms of mathematical modeling. Presented explosions based on real scenarios of accidents associated with transport and storage facilities with corrosive flammable chemicals. While explosions of pure flammable chemicals are well described in the literature, the information about explosions of corrosive and toxic flammable substances is rather scarce. This work aims at studying the explosion behavior of pure hydrogen-air, pure ammonia-air, ammonia-hydrogen-air, ammonia-methanol-air, ammonia-ethanol-air mixtures at different initial temperatures and pressures. The results of mathematical modeling of the calculated maximum explosion pressure are described.

This paper presents an analysis and simulation of an accident involving a liquefied petroleum gas (LPG) truck tanker in Kannur, Kerala, India. During the accident, a truck tanker hit a divider and overturned. A crack in the bottom pipe caused leakage of LPG for about 20 min forming a large vapor cloud, which got ignited, creating a fireball and a boiling liquid expanding vapor explosion (BLEVE) situation in the LPG tank with subsequent fire and explosion. Many fatalities and injuries were reported along with burning of trees, houses, shops, vehicles, etc. In the present study, ALOHA (Area Locations of Hazardous Atmospheres) and PHAST (Process Hazard Analysis Software Tool) software have been used to model and simulate the accident scenario. Modeling and simulation results of the fireball, jet flame radiation and explosion overpressure agree well with the actual loss reported from the site. The effects of the fireball scenario were more significant in comparison to that of the jet fire scenario.

Although industrial denotations in semi-open and congested geometries are often neglected by many practitioners during risk assessment, recent studies have shown that industrial detonations might be more common than previously believed. Therefore, from the explosion safety perspective, it becomes imperative to better assess industrial detonation hazards to improve robustness of explosion mitigation design, emergency response procedures, and building siting evaluation. Having that in mind, this study aims to review current empirical vapor cloud explosion models, understand their limitations, and assess their capability to indicate detonation onset for elongated vapor clouds. Six models were evaluated in total: TNO Multi-Energy, Baker-Strehlow-Tang (BST), Congestion Assessment Method (CAM), Quest Model for Estimation of Flame Speed (QMEFS), Primary Explosion Site (PES), and Confinement Specific Correlation (CSC). Model estimations were compared with large-scale test data available in the open literature. The CAM model demonstrated good performance in indicating deflagration-to-detonation transition (DDT) for test conditions experiencing detonation onset without any modification in the methodology. Some suggestions are provided to improve simulation results from PES, BST and QMEFS.

Toxic gas-containing flammable gas leak can lead to poisoning accidents as well as explosion accidents once the ignition source appears. Many attempts have been made to evaluate and mitigate the adverse effects of these accidents. All these efforts are instructive and valuable for risk assessment and risk management towards the poisoning effect and explosion effect. However, these analyses assessed the poisoning effect and explosion effect separately, ignoring that these two kinds of hazard effects may happen simultaneously. Accordingly, an integrated methodology is proposed to evaluate the consequences of toxic gas-containing flammable gas leakage and explosion accident, in which a risk-based concept and the grid-based concept are adopted to combine the effects. The approach is applied to a hypothetical accident scenario concerning an H2S-containing natural gas leakage and explosion accident on an offshore platform. The dispersion behavior and accumulation characteristics of released gas as well as the subsequent vapor cloud explosion (VCE) are modeled by Computational Fluid Dynamics (CFD) code Flame Acceleration Simulator (FLACS). This approach is concise and efficient for practical engineering applications. And it helps to develop safety measures and improve the emergency response plan.

Not all accidental releases of flammable gases and vapors create explosions. Most releases do not find an ignition source, and of those that do ignite, most of them result in deflagrations that generate low or moderate overpressures. Under some circumstances, however, it is possible for deflagration-to-detonation transition (DDT) to occur, and this can be followed by a propagating detonation that quickly consumes the remaining detonable cloud. In a detonable cloud, a detonation creates the worst accident that can happen. Because detonation overpressures are much higher than those in a deflagration and continue through the entire detonable cloud, the damage from a DDT event is more severe. This paper first provides a brief summary of our knowledge to date of the fundamental mechanisms of flame acceleration and DDT. This information is then contrasted to and combined with evidence of detonations (detonation markers) obtained from large-scale tests and actual large vapor cloud explosions (VCEs), including events at Buncefield (UK), Jaipur (India), CAPECO (Puerto Rico), and Port Hudson (US). The major conclusion from this review is that detonations did occur in prior VCEs in at least part of the VCE accidents. Finally, actions are suggested that could be taken to minimize detonation hazards.

Over the last decades a significant need has developed for change regarding safety control in the process and storage industries. Past-accident analysis shows that most dangerous incidents are related to failure of process operations and/or associated equipment. In October 2009, a series of events triggered by the dearth of redundant level control measures led to the release of huge quantities of gasoline from a bulk storage of Indian Oil Corporation Limited (IOCL) facility at Sitapura near the Jaipur airport in India, preceded by Buncefield, UK (2005), Puerto-Rico, USA (2009). All the above episodic incidents involved much extended clouds with characteristic diameters in the range 400–1000 m. Such incident established the need to not only understand vapour cloud explosion (VCE), but also the importance of avoiding the escalation of minor incidents into much more devastating consequences. At 18:10 IST on 29th October 2009, a leakage of gasoline occurred from one of the storage tanks on the IOCL Petroleum Oil Lubricants Terminal at Jaipur, India. The leakage continued for about 75–90 min led to the release of almost 340–400 tons of gasoline and created a very large vapor cloud (≈180,000 m2) over the entire installation. The delay ignition triggered a devastating VCE, which generated significant peak overpressure (>200 kPa). The VCE was followed by a multiple tank fire (9 tanks immediate after VCE), which lasted for 11 days. This accident resulted 11 fatalities, more than 150 people were injured, and a property loss of approximately US $60 million was reported. From an incident investigation so far, it can be understood that the obstacle in the flame path will create the intensified flame velocity reaching the Deflagration to Detonation Transition (DDT) level. A detonation is an unusual event; however, it is the worst case accidental event. The detailed analysis of IOCL, Jaipur and other accidents reported have highlighted that a typical major accident is not the result of a single undesired event, but rather the consequence of a succession of failures at several levels. Therefore, it has been a key challenge to anticipate combinations of such failures and corresponding unidentified incident scenarios. Additionally, the consideration of DDT phenomena in hazard and risk assessment would identify new escalation potentials and identify critical impacted. This knowledge will allow a more effective management of this hazard. Two complementary approaches to deal with this challenge are: i) improved identification of a typical scenarios, to reduce the occurrence of unforeseen events; ii) improved early detection, to reduce the possibility of remaining unforeseen events leading to an accident.

An unexpected explosion accident of an LNG transport trailer occurred in China on April 23, 2019, resulting in a massive vapor cloud explosion (VCE) fireball. The outstanding thermal damage induced by the LNG VCE’s fireball is enhanced in open space, which impose a serious threat on injured workers, building destruction, and even raise safety alarm about a potential second catastrophe. According to post-accident investigations of the present accident case, an integrated analysis of the fireball’s characteristics and thermal damage during the explosion accident are performed. Previously, an optimized model for the fireball’s characteristics have been developed based on full-scale experimental validation. It is found that the optimized model can facilitate better predictions in detailed parameters from the LNG VCE’s fireball in this study. Meanwhile, the numerical approach relating PHAST is applied to rebuild real accident scene, and the simulations involved fireball’s thermal hazards and damage radius on human and environment. Comparative research show that a near 100% fatality range is expected within a radius of 162.7 m and there is a harmless area with an ellipse distance of 893.9 m. It aims to bring a new development to predicted model, thereby improving performance of risk assessment on VCE fireball’s thermal damage duo to LNG transport process failure.

This paper describes data of post-release mitigation strategy and its effect for chemical process. The data in this paper is associated with the article entitled “Damage reduction strategies against chemical accidents by using a mitigation barrier in Korean chemical risk management”. The data includes computational fluid dynamics (CFD) simulation result for vapor cloud explosion accident scenarios. Simulations with suggested mitigation strategy and without the mitigation strategy were conducted. The data is expected to good reference for developing chemical plant mitigation plan.

The common rift between academia and industry has existed in all fields of engineering. However, ultimately that can be seen as more of a lag; it is not so much a question of academia research, which ends up finding its way into the practical world of industry years if not decades later. On the topic of detonations or Vapor Cloud Explosions (VCE), this is indeed a true statement. A little more than a decade ago the common belief in the chemical process industry was that detonations were not possible unless you had some very reactive process materials such as hydrogen or acetylene. When some industry and consulting experts began to challenge this view, they soon found out that a more common and less reactive process material such as ethylene could in fact be made to detonate as well. The key was that the environment had to be just right for an ignited flame to accelerate and transition to a detonation. In fact, academia had known this since the early 1960s and so the question remains, what else can we learn? Industry has retuned itself and made use of a several common explosion modeling tools which for some can be made to predict detonations. In others, they must be inferred and only very knowledgeable users can determine detonations. This paper will review the basics of detonations, the academic perspective and the industrial applications. Additionally, several of the various and commonly used models for explosion prediction will be reviewed, in the light of detonation.

On Sunday 11 December 2005, a severe unconfined vapor cloud explosion followed by several tank fires occurred at the Buncefield oil storage depot in England, near London, causing widespread damage to homes and businesses surrounding the site, hopefully without any victim. The damage caused by the resulting blast wave(s) surprised all the process safety community and explosion experts, as common hazard assessments would have predicted overpressures of only 5 kPa (0.73 psi), instead of 200 kPa (29 psi) as suggested by the data collected onsite. One of the particularities of the Buncefield oil storage depot is that it was surrounded by long and continuous rows of trees and bushes; this singularity is currently considered as a preponderant factor in the resulting high overpressures. Recently, explanations of the resulting overpressures were given by some authors using data from large-scale explosion tests and CFD simulations. The objective of this article is to verify whether application of simple methodologies used in common risk assessments could allow to estimate the severity of the Buncefield explosion. © 2011 American Institute of Chemical Engineers Process Saf Prog, 2012