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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.

To determine and optimize the emergency evacuation path of personnel in the case of vapor cloud explosion caused by pipeline leakage and improve the safety control measures in the high-consequence areas of gas pipelines, this study was conducted. This work mainly studied two questions: whether various research methods applicable to the solid explosive explosion are also applicable to vapor cloud explosion and the influence of different building layouts on the overpressure propagation law of vapor cloud explosion. First, the applicability of several empirical models and computational fluid dynamics (CFD) methods in vapor cloud explosion overpressure prediction is systematically compared and analyzed. Second, the finite element models based on the fluid-structure interaction are established to study the overpressure propagation law under the influence of different building layouts. Finally, based on the overpressure propagation law, the determination and optimization principle of the emergency evacuation path of personnel when an accident occurs are given. The results show that the CFD method and empirical model based on equivalent assumption between trinitrotoluene and combustible gas are not suitable for the study of gas-phase explosion, while the mixed gas method based on CFD is more suitable for exploring the overpressure problem of vapor cloud explosion. Buildings arranged perpendicular to the direction of blast wave have the most obvious enhancement and weakening effect on overpressure, and the maximum increase rate and decrease rate are about 90%. The maximum increase rate of overpressure between two vertical layout buildings is more than 60% higher than that between two horizontal layout buildings. When determining the emergency evacuation path, the non-explosive side of the building perpendicular to the shock wave layout should be given priority. If it is necessary to pass through the building gap, the gap between the two horizontal layout buildings should be preferred to ensure that the damage of overpressure to personnel is minimized. The research results can provide a theoretical basis for the improvement of personnel safety control measures in high-consequence areas of the gas pipeline.

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.

Vapor cloud explosion (VCE) accidents such as the Jaipur explosion in 2005 manifest that VCEs may lead to unpredicted overpressures, resulting in catastrophic domino effects. Many attempts have been made to assess VCEs and the subsequent domino effects in the process and chemical industry, whereas little attention has been paid to the spatial–temporal evolution of VCEs. Thus, this chapter provides a dynamic methodology based on the discrete dynamic event tree to assess the likelihood of VCEs and possible subsequent domino effects. The developed methodology includes six steps: identification and characterization of loss of containment scenarios, analysis of vapor cloud dispersion, identification and characterization of ignition sources, explosion frequency assessment, overpressure calculation, and escalation assessment. Given a release scenario, by applying the developed methodology, we can obtain the probability of VCEs, the likelihood of domino effects, and the damage probabilities of installations exposed to overpressure.

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.

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.

The vapor cloud explosion (VCE) begins with a release of a large quantity of flammable vaporing liquid from a storage tank, transportation vessel or pipeline. If VCE occurs in an oil storage facility, multiple tanks burn simultaneously. There is no effective firefighting method for multiple tanks fire. It will be extinguished when oil burned out spending several days. Many incidents of multiple tanks fire due to VCE have occurred all over the world in recent 50 years. This paper reviews the past 6 incidents of multiple tanks fire due to VCE.

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.

Shale gas is usually a high-purity methane gas and its content can reach up to 98%-99%, and shale gas well has low production and low wellhead pressure, therefore, jet fire and vapor cloud explosion are very typical accidents after shale gas wells leakage. We use computational fluid dynamics PHAST Software to simulate the consequences of wellhead shale gas leakage fire and explosion under different gas production, wellhead pressure, wind speed and atmospheric stability. We can determine the safety distance of facilities and personnel on the gas production well sites with the thermal radiation and shock wave overpressure damage industry standards for equipment and human body. When the shale gas production is from 4×104m3/d to 20×104m3/d and the wellhead pressure is from 2Mpa to 4.61Mpa, the safe distance between the facilities and the wellhead is 23.2m, and the safe distance between the personnel and the wellhead is 58.9m. These findings are very important to optimize well site layout and to ensure personnel safety, which can achieve safe and efficient development of shale gas.

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.

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.

In recent decades, vapor cloud explosions (VCEs) have occurred frequently and resulted in numerous personnel injuries and large property losses. As a main concern in the petrochemical industry, it is of great importance to assess the consequence of VCEs. Currently, the TNT equivalency method (TNT EM), the TNO multi-energy method (TNO MEM), and the Baker-Strehlow-Tang (BST) method are widely used to estimate the blast load from VCEs. The TNO MEM and BST method determine the blast load from blast curves based on the class number and the flame speed, respectively. To quantitatively evaluate the flame speed for the BST method, the experimental data is adopted to validate the confinement specific correlation (CSC) for the determination of the class number in the TNO MEM. As a bridge, a quantitative evaluation correlation (QEC) between CSC correlation and the flame speed is established and the blast wave shapes corresponding to different flame speeds are proposed. CFD software FLACS was used to verify the quantitative correlation with the numerical models of three geometrical scales. It is found that the calculated flame speeds by the QEC are in good agreement with the simulated ones. A petrochemical plant is selected as a realistic scenario to analyze the TNT EM, TNO MEM, BST method and FLACS simulations in terms of the positive-phase side-on overpressure and impulse at different distances. Compared with the flame speed table, the predicted overpressure from BST curves determined by the proposed QEC is closer to that from FLACS and more conservative. Furthermore, the predicted results of different methods are compared with each other. It is found that the estimated positive-phase side-on overpressure and impulse by the TNO MEM are the largest, and the estimated impulse by the TNT EM is the smallest. Moreover, the estimated overpressure and impulse are larger in the higher reactivity gas.

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.