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In this study, the liquefied petroleum gas (LPG) accident in Wenling, Zhejiang Province, China, on June 13, 2020, was analyzed and simulated. An LPG tank truck overturned and collided with the concrete guardrail; the subsequent explosion of the tank released 25.36 t LPG. Shortly afterward, the LPG tank was shot into the air, and the gas cloud ignited, thereby triggering a fire and vapor cloud explosion (VCE). This accident killed 20 people, injured 175 people, and caused significant property loss. The accident timeline was established based on multiple accident images, and the accident process was discussed in detail. The distribution of tank debris, evaporation and spreading of the LPG pool, dispersion of the LPG gas cloud, and VCE were simulated with the EFFECTS and ALOHA software. The images of the accident scene helped to determine and analyze the accident process. In the particular case in which a tank is shot into the air with a continuous two-phase jet, the actual flight distance of the tank is much greater than the prediction of the debris distribution model. The gas cloud distribution simulated with the SLAB model approximately corresponds to a major part of the severely damaged zone. In this accident, the TNO multi-energy method and ALOHA provide relatively consistent predictions with the actual building damage distribution when models use a specific confined explosive mass.

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.

Background: Modular steel buildings (MSB) are extensively used in petrochemical plants and refineries. Limited guidelines are available in the industry for analysis and design of (MSB) subject to accidental vapor cloud explosions (VCEs). Objectives: The paper presents simplified engineering model for modular steel buildings (MSB) subject to accidental vapor cloud explosions (VCEs) that are extensively used in petrochemical plants and refineries. Method: A Single degree of freedom (SDOF) dynamic model is utilized to simulate the dynamic response of primary building components. Analytical expressions are then provided to compute the dynamic load factors (DLF) for critical building elements. Recommended foundation systems are also proposed to install the modular building with minimum cost. Results: Numerical results are presented to illustrate the dynamic response of (MSB) subject to blast loading. It is shown that (DLF)=1.6 is attained at (td/t)=0.4 for front wall (W1) with (td/T)=1.25. For side walls (DLF)=1.41 and is attained at (td/t)=0.6. Conclusions: The paper presented simplified tools for analysis and design of (MSB) subject accidental vapor cloud blast explosions (VCEs). The analytical expressions can be utilized by practitioners to compute the (MSB) response and identify the design parameters. They are simple to use compared to Finite Element Analysis.

Background As of March 2019, JUUL electronic cigarettes are the most popular e-cigarette on the U.S. market, but little is known of nicotine exposure and dependence on JUUL and user experience. Methods JUUL users participated in a community-based study involving questionnaires, saliva collection and a qualitative interview. Results Fifteen participants were enrolled (80% male, 53% White) and had an average age of 29.8 (standard deviation = 10) years. Daily exposure to nicotine assessed via salivary cotinine was similar to those reported for other e-cigarette and tobacco cigarette users in general. The majority reported low to moderate nicotine dependence. Qualitative interview themes included: the importance of social networks in adoption and use of the product; device features such as small size and vapor cloud reinforced product use; the product provided satisfaction compared to a tobacco cigarette; and a perceived sense of addiction to the product. Conclusions JUUL e-cigarettes expose users to levels of nicotine similar to other e-cigarettes but may be more satisfying due to unique device features. JUUL may be quite acceptable to tobacco cigarette smokers who are seeking to quit. However, it holds addictive potential and can reinforce long-term nicotine use.

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.

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.

The dynamic analysis of a tent structure subjected to an external blast load is presented. The case studied refers to temporary structures employed in petrochemical facilities that need to resist to vapor cloud explosions that can happen in the vicinity of the tent. The structure can undergo severe permanent deformations but must not collapse and the maximum displacements have to be limited in order not to harm the occupants.

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.

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.

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 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

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...

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.

Structural insulated panel (SIP) is a lightweight composite panel widely used in commercial, industrial and residential building industry. It consists of insulating polymer foam sandwiched by two layers of structural skins. The composite structural insulated panel is considered as a sustainable, economical, thermal insulated, moisture resistant, acoustic insulated and flame retardant panel, which has been more and more commonly used in building industry, and also in petrochemical industry for construction of office buildings, control rooms, store rooms and residential structures. These structures might be subjected to far field explosion loads caused by accidental gas explosion in residential areas and vapor cloud explosion (VCE) in petroleum and chemical processing industries. The performance of composite structural insulated panel against accidental explosions has yet been investigated. In this study, the blast resistant performance of the composite panel is numerically investigated by using software LS-DYNA with the calibrated numerical model. Its blast resistance capacity and energy absorption capacity are quantitatively examined. Parametric studies are also carried out to investigate the effect of panel configurations on its blast resistance capacity. Keywords: Composite, Structural insulated panel (SIP), Numerical simulation, Blast resistant performance, Panel configurations

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.

Chemicals used in paint industry are generally comprised of toxic and inflammable substances; they may cause serious problems for humans and environment if safety conditions are neglected. In 2012, rupture of a toluene tank in a paint factory in Iran claimed lives of two workers near the tank. The present study is formulated in order to model the incident. The results showed the area prone to flash fire occurrence and extension. Furthermore, radiation was measured in terms of distance to the tank. A bund wall is also assumed around the vessel in order to determine its influence on evaporation in flash fire area, radiation, and maximum concentration of vapor cloud. The results provided important hints on minimum and required distance of electrical equipment or electrical enclosure (PLC) installation from vessels as well as suitable distance between the vessels. Finally, preventive recommendations were proposed to reduce the risk of potential accidents.

In the last two decades, several serious accidents at large-scale technological systems that have had grave consequences, such as that at Bhopal, have primarily been attributed to human error. However, further investigations have revealed that humans are not the primary cause of these accidents, but have inherited the problems and difficulties of working with complex systems created by engineers. The operators have to comprehend malfunctions in real time, respond quickly, and make rapid decisions to return operational units to normal conditions, but under these circumstances, the mental workload of operators rises sharply, and a mental workload that is too high increases the rate of error. Therefore, cognivitive human features such as situation awareness (SA)—one of the most important prerequisite for decision-making—should be considered and analyzed appropriately. This paper applys the SA Error Taxonomy methodology to analyze the role of SA in three different accidents: (1) A runaway chemical reaction at Institute, West Virginia killing two employees, injuring eight people, and requiring the evacuation of more than 40,000 residents adjacent to the facility, (2) The ignition of a vapor cloud at Bellwood, Illinois that killed one person, injured two employees, and caused significant business interruption, and (3) An explosion at Ontario, California injuring four workers and caused extensive damage to the facility. In addition, the paper presents certain requirements for cognitive operator support system development and operator training under abnormal situations to promote operators’ SA in the process industry.

In this work, the prediction of the overpressure resulting from a vapor cloud explosion (VCE) will be conducted from external area of a chemical process plant. Based on Feyzin Refinery disaster, this study will analyzed and focused on the spillage from a delayed ignition causing a VCE from the T61-443 sphere tank. TNT Mass Method and Baker-Strehlow models are used to estimate the overpressure of the explosion. The results are presented in the form of table and figures to compare the two methods and justify the overpressure predicted.

A devastating crude oil vapor explosion accident, which killed 62 people and injured 136, occurred on November 22, 2013. It was one of the most disastrous vapor cloud explosion accidents that happened in Qingdao's storm drains in China. It was noted that blast overpressure and flying debris were the main causes of human deaths, personal injuries and structure damages. Two months after the accident, it was reported that there were three contentious issues in the investigation report. First issue was the discrepancy between the temperature of the crude oil vapor explosive limits which were measured by the investigation panel and the temperature reported by the local fire department. Second issue was the contradiction between the upper explosive limit and vapor pressure of the crude oil vapor. The last issue was the location of the ignition source which led to the explosion. In the present study some specific features of this accident and various causes led to the explosion, high casualties and severe damages were analyzed. Three contentious issues in the official investigation report were investigated and tested in detail. The first element tested was the explosive limits and limiting oxygen concentration of the crude oil vapor at different temperatures. Based on theoretical analysis and field investigations, the last two elements in the report were analyzed from multiple perspectives. Based on the TNO Multi-Energy model and PROBIT equations, damage probability of affected people at the leaking site was also estimated. The investigation concluded with a result that precautions need to be taken to prevent flammable gas explosions in the drainage systems. Key steps were explicitly discussed for improving the hazard identification and risk assessment of similar accidents in the future.

This study investigated the explosion characteristics of HCNG fuel using a simulation tool. The damage caused by the storage container explosion and vapor cloud explosion in a gas station was predicted. In case of an vapor cloud explosion in the HCNG station, 50 200kPa explosion pressure was predicted inside the ‡A station. When the cylinder explosion was occurred, in case of hydrogen, the measured influential distance of overpressure was 59m and radiant heat was 75m. In case of CNG, influential distance of overpressure was 89m and radiant heat was 144m would be estimated. In case of 30% HCNG that was blended with hydrogen and CNG, influential distance of overpressure was 81m and radiant heat was 130m were measured. The damage distance that explosive overpressure and radiant heat influenced CNG was seen as the highest. HCNG that was placed between CNG and hydrogen tended to be seen as more similar with CNG.

A hydrocarbon Vapor Cloud Explosion (VCE) is one of critical hazardous events in offshore installations. Once VCE occurs in the ocean, it results in tremendous economic loss, casualties, and environmental impact. The combustion mechanism of VCE differs from HE in particular in complex geometries (e.g. offshore oil and gas production facilities) as there exist many objects which can trigger severe turbulences. Although many research efforts have been made to develop design provisions for blast resistant structures, most of those provisions are based on high-order explosives (HE) such as TNT (TriNiTrotoluene) in a free field. Therefore, typical blast resistant structural design standards were examined to address the weaknesses of standards in this study. Existing blast wave models which provide key design load parameters were also reviewed to address limitations of each approach. Finally, essential recommendations are discussed in this paper for future studies to improve blast resistant structural design provisions with the ultimate aim of protecting our lives, assets and environment from VCE in the ocean.

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.

A model for predicting vapor cloud explosion blast loads is described extending a previously developed model. The model considers the contribution of a Primary Explosion Site (PES) as well as the bulk effect of the total flammable cloud. The model results are then compared with historical accidents and other commonly used models considering a single PES. Four historical events are examined: the Flixborough accident of 1974, the Texas City accident of 2005, the Phillips 66 accident of 1989, and the Buncefield incident of 2005. It is found that the combined model produced pressure and impulse values consistent with the damage observed. If the contribution of the total cloud is not considered, the far field pressure, which included overpressures up to 0.35 bar, was underpredicted and impulse was significantly underpredicted. The other methods, produced, in general, significantly lower overpressures and impulses when compared with the damage indicators seen in the explosion accidents. © 2014 American Institute of Chemical Engineers Process Saf Prog 34: 147–153, 2015

Fire risk of gas pipeline leakage is high.The factors contributing to gas pipeline leakage most are third party damage, corrosion, design and incorrect operation. The accident consequences of gas pipeline leakage and quantitative risk assessment method of gas pipeline leakage consequence are analyzed. In order to achieve quantitative fire risk assessment of gas pipeline leakage, flash fire model, vapor cloud explosion model and thermal radiation damage criterion are analyzed. Firstly, the gas leakage quantity is estimated. Then, the heat radiation estimate flux, the thermal dose and damage range are got by using flash fire model, vapor cloud explosion model and the thermal radiation damage criterion respectively.Combined with an example of gas pipeline, damage ranges of different disaster patterns are estimated according to different gas pipeline leakage pattern. Through comparing the accident consequences of gas pipeline leakage, this paper provides some reliable scientific references for gas pipeline management departments.

This paper analyzes the fire explosion risk of liquefied petroleum gas (LPG) storage tank through methods of model calculation and simulation. A large crude oil reserves library in Tianjin is the main study object in this paper, the fire process for the storage tank pool fire is simulated using the fire simulation software FDS, which produces the development of fire and the change of the radiation intensity in the case of fire. And the damage degree of explosion accident consequences has been calculated quantitatively by the vapor cloud explosion model, which obtains the casualties radius and property damage. Study results provide reference data and theoretical guidance for fire protection design and fire fighting tactics in LPG storage tank area.

A test was conducted which demonstrates that a detonation wave, once formed due to a deflagration to detonation transition (DDT) within a congested region, will propagate as a detonation from the congested region into an uncongested region. This is the expected behavior based on the general behavior of detonation waves as well as other tests reported in literature. The impact of a detonation wave propagating beyond the congested volume in which it is initiated on the resulting blast load was evaluated parametrically. As would be expected, the impact on the blast load is large for flammable clouds which extend well beyond the congested volume. The test rig was 16.5 m (54 ft) long with the first 9.1 m (30 ft) of the rig length comprised of a congested section 3.7 m (12 ft) in width and 1.8 m (6 ft) high. The congestion was made up of a regular array of vertical circular tubes [6 cm (2.375 in.) diameter, pitch-to-diameter ratio of 4.1, area and volume blockage ratios of 23% and 4.2%, respectively]. The last 7.3 m (24 ft) of the test rig length was completely uncongested. The test rig was configured without any confinement (i.e., no wall or roof sections). A near-stoichiometric ethylene-air mixture completely filled both the congested and uncongested portions of the test rig. Prior testing with a similar rig configuration had shown that this flammable mixture would undergo a DDT within the congested portion of the rig. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

API Recommended Practice 752 is one of the most referenced practices for evaluating vapor cloud explosion (VCE) impacts to site occupied buildings. This reference introduces generic VCE frequencies for different types of process units that are based on VCE incidents database. Although these reported VCE frequencies are not capable of illustrating all parameters that affect explosion likelihood, they are widely used in risk analysis studies and software packages. This paper delineates the structure of a more realistic method for estimation of local VCE frequencies for independent congested spaces or units as a function of process, site, and meteorological variables. Compared to traditional methods for VCE frequency estimation, the new proposed approach is supported by an obviously more populated and precisely categorized database of leakage frequencies and features a multi-variable functionality of process/plant conditions. Contrary to previous procedures that aimed at finding the frequency of occurrence for a single VCE incident, this proposed methodology characterizes each congested space with a local VCE frequency. This frequency is an integration of the frequencies pertaining to VCE's that are likely to be initiated by each congested space. This new VCE frequency can also be used to determine the level of explosion hazard in each unit and in risk matrix analysis.

It is very important and necessary to perform quantitative hazard analysis for possible accidental leakage from an underground gas storage cavern in salt rock. An integrated quantitative hazard analysis method for natural gas jet release from salt caverns is presented in this paper, which was constituted by a revised model for gas leakage rate calculation, a consequence analysis and a model of probability assessment for harm. The presented method was validated by comparing the analytical results with the data collected from the real accidents (including the leakage, jet fire, fireball and vapor cloud explosion). It is indicated that the proposed method was more accurate than the TNT equivalence method for vapor cloud explosion and gave more reasonable results when applied to the consequence analysis for the thermal radiation from jet fire and fireball.

Gas dispersion and explosion dynamics can be very complex. Blast effects in the far field are less sensitive to the local dynamics of an explosion event, and simplified techniques have been developed to roughly estimate the amount of fuel involved (i.e., energy released) in an explosion based on the observed damage in the far field. However, these simple techniques are not suitable to predict the complex explosion dynamics that occur in the near field. The phenomena that drive explosions and resulting damage in the near field are complex in nature, as they depend on non-linear interactions between multiple variables (e.g., ignition location, flame accelerations due to object interaction, fuel reactivity, geometry of the facility regarding confinement and interconnected rooms, vent areas, etc.). Furthermore, the damage created in the near field by overpressure development, blast wave reflections and focusing, pressure impulse, pressure piling, blast wind and ensuing drag forces, may be difficult to interpret using simple methods. The origin of an explosion may, in fact, differ from the intuitive epicenter determined from oversimplified assumptions and may lead to incorrect conclusions regarding the cause and origin or initiating events of the accident. State-of-the-art 3D modeling tools, such as FLACS, are typically required to understand and evaluate complex explosions. FLACS was specifically developed to predict the consequences associated with complex explosions, especially in the near field, and has been extensively validated against hundreds of full-scale experiments. Therefore, FLACS simulations can be used to investigate the chain of events of the explosion and provide a more complete understanding of the evidence, including near-field blast damage. This paper presents the findings of how FLACS was used to help determine the explosion origin in the explosion that occurred at an ink and paint manufacturing facility in Danvers, Massachusetts, on November 22, 2006. This paper is not intended to provide complete investigation findings and will only provide the necessary background material to follow the explosion origin analysis.

Hydrocarbon gas explosion is one of the critical hazards resulting in huge environmental impact as well as loss of valuable assets and lives as observed from the historical disasters in the oil and gas industry. In response to these events, stronger international rules and regulations have been made to ensure safety of these structures. Hence, considerable effort has been devoted to quantify accidental design loads for flammable gas based on probabilistic approaches which requires extensive computational fluid dynamic simulations. Also, demand for 3D nonlinear dynamic finite element structural simulations has increased significantly with rapid progress in computer performance. Some of the major issues and difficulties in structural design and evaluation for probabilistic design loads are discussed in this paper. Uncertainties in explosion hazard analysis which cause large variations in probabilistic explosion responses are reviewed. Some gaps between provisions for design load estimation based on probabilistic approaches versus current structural design and analysis schemes are compared. Finally, it is concluded that there is an urgent need for reliable guidelines for risk-based structural design and simulation for probabilistic explosion design loads.

Various models are currently applied to predict the dispersion of leaked combustible gas and overpressure from a vapor cloud explosion(VCE). However, those models use simple approaches where top-ography and barriers of anti-leakage facilities and the effects of buildings were not sufficiently taken into considerations. For this reason, this study has proposed the dispersion process of leaked gas, distribution pat-terns, and flames and overpressure generated from gas explosions in 2D and 3D virtual spaces by reviewing more accurately analyzable computational fluid dynamics (CFD) model by considering various variables in-cluding combustion types of leaked substances, geometry of facility, warm currents, barriers, the influence of wind, and others. The CFD analysis results are anticipated to be usefully applied for the risk analysis of ex-plosion and for the risk-based design.Key words : VCE(vapor cloud explosion), CFD(computational fluid dynamics), risk analysis 1) † 교신저자:hmkwon@kosha.netKIGAS Vol. 16, No. 5, pp 58~65, 2012 http://dx.doi.org/10.7842/kigas.2012.16.5.58(Journal of the Korean Institute of Gas)

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.

The main objectives of this study are to analyze the leaked gas dispersion and quantify the potential overpressures due to vapor cloud explosions in order to identify the most significant contributors to risk by using Computational Fluid Dynamics (CFX & FLACS) for gas fuelled ships. A series of CFD simulations and analyses have been performed for the various gas release scenarios in a closed module, covering different release rates and ventilating methods. This study is specially focused on the LNG FGS (Fuel Gas Supply) system recently developed for the propulsion of VLCC crude oil carriers by shipyards. Most of work presented is discussed on the gas dispersion from leaks in the FGS room, and shows some blast prediction validation examples.

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.

Based on the tunnel environment and the characteristic of flammability and explosion of liquefied petroleum gas (LGP), the leak of LPG tanker can induce heavy casualties and property loss in the tunnel. In order to study quantitative risk of LGP transportation in road tunnel, the data of 599 accidents and 659 accidental vehicles are collected. From these data, the proportion of LGP tanker accident in the total accident vehicles and million vehicles kilometer (MVK) tanker accident rates are obtained. By analyzing the leakage scene of LGP tanker, the possible accident types of the LGP transportation were analyzed, such as boiling liquid expanding vapor explosion (BLEVE), vapor cloud explosion (VCE), flash fire and jet fire, etc. The impact of leak time to various ranges of injury is studied in the condition of LGP continued leakage. The slight injury, serious injury and death radius of LGP leakage accidents are calculated in tanker loaded with different LGP quantity. In view of the accidental analysis, the countermeasures will be proposed to reduce the risk of LGP transportation in road tunnel.

CNG cylinder is a sort of used storage device in CNG filling stations. As a gas storage container with high-pressure, it will lead to harmful consequences if failure occurs. The explosion consequences after its leakage are analyzed in this article. The vapor cloud explosion (VCE) quantitative evaluation model is compared with API pub 581 consequences evaluation model. And the comparison of the consequences of the explosion bteween two evaluation models is also made based on an example with a set of CNG cylinders.

The first edition of the CCPS book Guidelines to Evaluating Vapor Cloud Explosions, Flash Fires and BLEVEs was published in 1994. The second edition was completed in October 2010. It is a major revision of the Guideline with contents completely reorganized, recent research results added, revised and new prediction methods inserted, with sample problems worked for each prediction method. The treatment of pressure vessel burst was expanded and placed in a dedicated chapter, resulting in a new name for the second edition of the Guideline. © 2011 American Institute of Chemical Engineers Process Saf Prog, 2011.

Vapor cloud explosions (VCEs) cause considerable problems in the chemical and petrochemical industries. They generate damaging levels of overpressure and the possibility of human injury/death, and building/equipment damage. Predicting the possible consequences of VCEs is important to ensure the safe design of existing and new structures. Prediction of the overpressures resulting from a VCE is typically done using simplified (empirical) models, phenomenological models, and computational fluid dynamics models. The focus of this article is on two of the most frequently used simplified prediction methods: TNO multienergy and Baker–Strehlow–Tang models. These models are compared in terms of structural response and vulnerability of damage caused by an explosion. © 2010 American Institute of Chemical Engineers Process Saf Prog, 2011

Quantifying the size of flammable vapor cloud hazards associated with an accidental release of Liquefied Natural Gas (LNG) into a spill containment system supported by narrow drainage trenches has posed a modeling challenge since the inception of the LNG industry. Early attempts to treat the vapors evolving from the trenches included using line-source Gaussian models, and the use of the DEGADIS model by modeling “segmented” trench elements and adding the contributions from each trench segment at a specified downwind distance. These approaches often are only reasonable for a select set of conditions (e.g., winds perpendicular to the trench) and have no ability to simulate many of the conditions that might result in a larger potential impact (e.g., winds blowing parallel to the trench).

Fire and explosion hazards in ammonia plants include releases of flammable materials. The distinction between fire and explosion scenarios is often whether the fuel ignites promptly upon release or has delayed ignition. Prompt ignition prevents formation of a flammable vapor cloud and, thereby, averts a VCE. Syngas contains a significant amount of hydrogen, a fuel that is easily ignited. Industry experience with accidental releases of syngas has been that it promptly ignites. Literature was reviewed for test and accident data for syngas and hydrogen to estimate the probability of prompt versus delayed ignition. No instances of syngas VCEs were found in literature; however, numerous test and accidents were reported for hydrogen. The probability of delayed ignition varied with the release conditions. A conservative estimate of the probability of delayed ignition was developed. © 2010 American Institute of Chemical Engineers Process Saf Prog, 2010

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.

Effective safety measures to prevent and mitigate the consequences of an accidental release of flammable LNG are critical. Water spray curtain is currently recognized as an effective technique to control and mitigate various hazards in the industries. It has been used to absorb, dilute and disperse both toxic and flammable vapor cloud. It is also used as protection against heat radiation, in case of fighting vapor cloud fire. Water curtain has also been considered as one of the most economic and promising LNG vapor cloud control techniques. Water curtains are expected to enhance LNG vapor cloud dispersion mainly through mechanical effects, dilution, and thermal effects. The actual phenomena involved in LNG vapor and water curtain interaction were not clearly established from previous research. LNG spill experiments have been performed at the Brayton Fire Training Field at Texas A&M University (TAMU) to understand the effect of water curtain in controlling and dispersing LNG vapor cloud. This paper summarizes experimental methodology and presents data from two water curtain tests. The analysis of the test results are also presented to identify the effectiveness of these two types of water spray curtains in enhancing the LNG vapor cloud dispersion.

A few years ago, there was an explosion in a reactor at the XYZ Chemical Company. The reactor was a block copolymerization reactor where butadiene and styrene monomers were added in a semibatch manner. The heat of reaction was removed by means of a refrigeration system. The incident occurred when the reactants were not added in the sequence or quantity required. The resulting runaway reaction overpressurized the reactor system and caused an expansion joint to rupture. The hydrocarbons released formed a vapor cloud that exploded, causing the death of two workers, serious injury to three others, and significant damage to the facility. The contributing causes of the incident include: (a) lack of information about the hazards of the chemicals in the process, (b) lack of information about the equipment in the process and inadequate equipment, (c) inadequate or no PHA, (d) inadequate training, (e) confusing operating procedures, (f) failure to use management of change procedures, (g) failure to perform a prestartup safety review, (h) failure to have an adequate contractor safety program, and (i) failure to investigate previous near misses and incidents and take corrective actions. This article describes this accident, the root causes, and the major plant deficiencies. The following expresses my opinion of the events that led to this explosion as testified to in open court. Others may have different opinions. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2010