Consequence analysis by means of characteristic curves to determine the damage to buildings from bursting spherical vessels

Since the damage suffered by buildings as a consequence of explosions usually affect the people inside them, it is important to take it into account when performing consequence analysis. The aim of this paper is to provide a methodology to estimate consequences to buildings from pressure waves produced by spherical vessel burst. This is done by combining characteristic overpressure–impulse–distance curves [González Ferradás, E., Diaz Alonso, F., Sanchez Perez, J.F., Miñana Aznar, A., Ruiz Gimeno, J. and Martinez Alonso, J., 2006, Characteristic overpressure–impulse–distance curves for vessel burst, Process Safety Progress, 25(3): 250–254] with PROBIT equations. The main advantage of this methodology is that it allows an overview of all the magnitudes involved, as damage is shown in the same graph as the overpressure, impulse and distance. In this paper diagrams and equations are presented to determine minor damage to buildings (broken windows, displacement of doors and window frames, tile displacement, etc.), major structural damage (cracks in walls, collapse of some walls) and collapse (the damage is so extensive that the building is partially or totally demolished).     

Consequence modeling of a real rupture of toluene storage tank

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.     

Class-2 hazmat transportation consequence assessment on surrounding population

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

基于灰色关联分析和IAHP的CNG加气站安全评价方法研究

建立了压缩天然气(CNG)加气站安全评价的指标体系和安全等级的评分标准,运用改进的层次分析法(IAHP)计算CNG加气站安全指标权重序列,运用灰色关联法计算参评序列与标准序列的关联度。最大关联度所对应的标准向量等级,即为CNG加气站所属的安全等级。IAHP采用"三标度"法确定判断矩阵,相对于层次分析法中的"九标度"法来说,更易于保持矩阵的一致性。应用笔者提出的理论与方法,对北京某CNG加气站的实际案例计算,验证该方法的有效性。计算结果表明:售气系统安全、气体储存和压缩系统安全、人员的违章操作情况、司机或加气站人员是否在站内抽烟、站内设施与站外建筑物防火距离等是CNG加气站安全的主要影响因素,应对其进行重点管理。     

Case study: Assessment on large scale LPG BLEVEs in the 2011 Tohoku earthquakes

After the 2011 Tohoku earthquakes, several chemical and oil complexes on the Pacific Ocean shoreline of northeast Japan experienced massive losses. In Chiba, a refinery operated by Cosmo Oil lost 17 LPG storage vessels which were either heavily damaged or totally destroyed by fires and explosions in the refinery. These large vessels ranged in size from 1000 to 5000 m³. The estimated volume of LPG at the time of the incident was between 400 and 5000 m³ for each vessel. Five boiling liquid expanding vapor explosions (BLEVEs) of LPG occurred, resulting in huge fire balls measuring about 500 m in diameter.A BLEVE is defined as the explosive release of expanding vapor and boiling liquid when a container holding a pressure-liquefied gas fails catastrophically. It is thus important to estimate the physical properties of superheated liquids: the thermodynamic and transport properties, the intrinsic limits to superheating and depressurization, and the nature of thermodynamic paths. Also it is hoped to provide better understanding of the vessels designed, manufactured, installed, and operated to reduce or eliminate the probability that a sequence of events will result in BLEVE or loss of primary containment. Knowledge of these matters is still incomplete. The objective of this research is to estimate the significant BLEVE phenomenon in very large scale spherical vessels based on published information in Japan. There are some models predicting BLEVEs. However, it is essential to know if this is true for very large scales such as spheres since validation is usually rare to provide confidence in estimating the superheated liquids behaviors. To this end, comparing with the information on this event, the conditions in the five LPG vessels at the time of the BLEVE were determined in terms of: duration of vessel failure (time to BLEVE); mass fraction in the vessel with time; temperature distribution in the liquid and vapor region and pressure within the vessel (e.g. initial pressure and internal high-speed transient pressure during failure), by means of a computer program AFFTAC Analysis of Fire Effects on Tank Cars, which solves heat conduction, stress and a failure model of the tank, a thermodynamic model of its fluid contents, and a flow model for the lading flowing through the safety relief device. Subsequently, the consequences from the sphere BLEVE, such as the expected fireball diameter and duration and the expected blast overpressure produced by the BLEVE failures, are also subjects of active research. Here the blast using the methods of PHAST and SFPE Handbook of Fire Protection Engineering was calculated.Results suggest that methodologies here used gave reasonable estimations for such real and huge BLEVEs in a validated way, which may provide valuable guidance for risk mitigation strategy with regard to LPG facility in design, emergency planning, resiliency, operations, and risk management.     

Preliminary study of ballistic impact on an industrial tank: Projectile velocity decay

Since the events of September 11, 2001, the possibility of an intentional act targeting the chemical process industry has become realistic. It is, therefore, a great concern to be able to predict the immediate consequences of such an act. This study is intended to improve our knowledge about the sequence of events that occurs when a high-speed bullet (>1000 m s⁻¹) penetrates a vessel filled with toxic liquid. We find that, prior to liquid ejection, several well-defined phases occur, including the phenomenon known as the “hydraulic ram.” This paper focuses on projectile–target interactions and explains how the decay of projectile velocity is related to the initial conditions of the target.     

Towards more detailed determination of third party impact on risk on natural gas pipelines: Influence of population density

The paper presents a refined way to quantify the effects of third party interference on risk that is posed on people by transmission pipelines for natural gas. The main focus is set on the influence of population density on risk. Using the interdisciplinary approach, the presented study combines the knowledge from relevant risk assessment recommendations, physical consequences of hazardous events, existing history databases of hazardous event frequencies and urban planning. A quantitative boundary between two most populated types of area was established. A flexible risk coefficient was determined for a suburban type of populated area that is dependent on average population density. Consequently, a new approach for determination of a hazard distance from the pipeline and area boundaries for calculation of average population density was presented. This differs from the established methods described in some guidelines, but is based on results of applied quantitative risk assessment. The final result is more accurate determination of risk levels in suburban areas. Described methods may serve as a supplement to the existing models for quantitative risk assessment on pipelines used in natural gas transportation and may be used by pipeline operators as well as policy- and decision makers.     

Analyzing effective factors on leakage-induced hydrogen fires

Currently, novel energy resources are receiving increasing attention as a response to the limitation in fossil fuels as well as their adverse effects on human health. Hydrogen, one of the most abundant elements on the earth, can be regarded as a new energy source to replace fossil fuels. Therefore, safety assessment of the relating processes is very crucial by increasing use of hydrogen as a fuel source. In this regard, consequence analysis for risk assessment and power reduction is very important. The present study aims at modeling hydrogen dispersion along with consequence analyses for such events as jet fire and flash fire. The model was validated by using the data derived from a study on hydrogen leakage in supply pipelines in the laboratory of the University of Pisa. Modeling results reveal that ambient conditions will impose a milder impact on leakage consequences if internal pressure is high in release source. The safe distance was also estimated to be 14 m. Dispersion consequence modeling was performed, followed by the evaluation of the effect of environmental (i.e., stability, ambient temperature, surface roughness, wind speed, and humidity) and process (i.e., vessel temperature and pressure, leakage diameter, and releasing point height) parameters on maximum size flammable vapor cloud and maximum level jet fire radiation on the ground. The size of flammable vapor cloud (consequence dispersion index) and the maximum flux of radiation were affected by process parameters more than ambient parameters. Leakage diameter and the vessel pressure were found to have the highest impact on the operational parameters.     

Study on the early stage of runaway reaction using Dewar vessels

In this paper, compared with a UN cylindrical 500 mL Dewar (H.4 in the UN tests), a spherical 1 L Dewar vessel was used to study the early stages of runaway reactions of several liquid and solid samples, including three organic peroxides and a reactive material. The samples were filled in the vessels and the temperature profiles versus times at different positions of the samples were measured. As a result, the minimum temperatures, defined as the SADT, were averagely 10 K lower than those measured in the cylindrical Dewar vessels. At the same time, the temperature profiles of solids in the spherical Dewars tended to be homogeneous. The heat transfer coefficient of a spherical Dewar is only 0.18 W/K/m, one-eighth of a conventional cylindrical Dewar vessel. Meanwhile it has a low phi factor. These factors are essential to simulate low heat loss bulk conditions in the equilibrium process and at the early stage of a runaway reaction. To characterize the ability of the adiabaticity of a storage vessel, it can be seen that a spherical Dewar could simulate the plant process having critical storage size of a reactive-material, r₀, approximately 0.6 m. It is recommended that such a technique is used to investigate the SADT of an unstable material in larger scale packaging or a material with very weak heat release in industry.     

Propagation Characteristics of Gas Explosion in Linked Vessels Based on DDT Criteria

To study the occurrence conditions and propagation characteristics of deflagration to detonation transition (DDT) in linked vessels, two typical linked vessels were investigated in this study. The DDT of the methane–air mixture under different pipe lengths and inner diameters was studied. Results showed that the CJ detonation pressure of the methane–air mixture was 1.86 MPa, and the CJ detonation velocity was 1987.4 m/s. Compared with a single pipe, the induced distance of DDT is relatively short in the linked vessels. With the increase in pipeline length, DDT is more likely to occur. Under the same pipe diameter, the DDT induction distance in the vessel–pipe–vessel structure is shorter than that in the vessel–pipe structure. With the increase in pipeline diameter, the length of the pipe required to form the DDT is reduced. For linked vessels in which detonation formed, four stages, namely, slow combustion, deflagration, deflagration to detonation, and stable detonation, occurred in the vessels. Moreover, for a pipe diameter of 60 mm and a length of 8 m, overdriven detonation occurred in the vessel–pipe–vessel structure.     

The significance of domino effect in chemical accidents

A historical survey was performed on 330 accidents involving domino effect, occurred in process/storage plants and in the transportation of hazardous materials; only accidents occurred after 1st-January-1961 have been considered. The main features – geographical location, type of accident, materials involved, origin and causes, consequences, domino sequences – were analyzed, with special consideration to the situation in the developing countries and compared to those from other previous surveys. Among the involved substances, LPG was the most frequent one, followed by liquid hydrocarbons. Process plants (38.5% of cases) and storage areas (33%) were the most common settings; 10.6% of past domino accidents occurred in transfer operations. The ratio between “two-step” and “three-step” domino accidents was found to be 6. A specific analysis of the accidents (84) occurred in the 21st century was performed, comparing them with the total set of accidents. Finally, a set of specific recommendations inferred from the results is provided.     

Experimental investigation of gas explosion in single vessel and connected vessels

Gas explosion in connected vessels usually leads to high pressure and high rate of pressure increase which the vessels and pipes can not tolerate. Severe human casualties and property losses may occur due to the variation characteristics of gas explosion pressure in connected vessels. To determine gas explosion strength, an experimental testing system for methane and air mixture explosion in a single vessel, in a single vessel connected a pipe and in connected vessels has been set up. The experiment apparatus consisted of two spherical vessels of 350 mm and 600 mm in diameter, three connecting pipes of 89 mm in diameter and 6 m in length. First, the results of gas explosion pressure in a single vessel and connected vessels were compared and analyzed. And then the development of gas explosion, its changing characteristics and relevant influencing factors were analyzed. When gas explosion occurs in a single vessel, the maximum explosion pressure and pressure growth rate with ignition at the center of a spherical vessel are higher than those with ignition on the inner-wall of the vessel. In conclusion, besides ignition source on the inner wall, the ignition source at the center of the vessels must be avoided to reduce the damage level. When the gas mixture is ignited in the large vessel, the maximum explosion pressure and explosion pressure rising rate in the small vessel raise. And the maximum explosion pressure and pressure rising rate in connected vessels are higher than those in the single containment vessel. So whenever possible, some isolation techniques, such as fast-acting valves, rotary valves, etc., might be applied to reduce explosion strength in the integrated system. However, when the gas mixture is ignited in the small vessel, the maximum explosion pressures in the large vessel and in the small vessel both decrease. Moreover, the explosion pressure is lower than that in the single vessel. When gas explosion happens in a single vessel connected to a pipe, the maximum explosion pressure occurs at the end of the pipe if the gas mixture is ignited in the spherical vessel. Therefore, installing a pipe into the system can reduce the maximum explosion pressure, but it also causes the explosion pressure growth rate to increase.     

CNG加气站事故后果分析方法研究

根据CNG加气站系统运行的实际情况，将CNG加气站中易发生泄漏的设备分为管道阀门、挠性连接器、压缩机、储气设备、放散管5类。建立了CNG泄漏的事件树，将CNG加气站的事故后果类型概括为喷射火、闪火、蒸气云爆炸。总结了CNG加气站事故后果的计算模型，采用美国环保局的ALOHA软件确定事故后果的影响范围。综合运用该两种方法对喷射火和蒸气云爆炸的事故案例进行对比研究，结果表明，计算结果基本一致。该两种事故后果分析方法为CNG加气站安全管理和安全规划提供依据。     

The velocity of end-cap and rocket missiles generated by failure of a gas pressurised vessel containing particulate material

Many industrial installations include pressure vessels which contain high pressure gas and particulate material. Given the rupture of such a vessel, it is established that provided the particulate acceleration is not greater than the acceleration of a detached end-cap, the end-cap velocity will be similar to that generated by rupture of a gas filled vessel with the same available gas expansion energy. In contrast, if the particulates accelerate to overtake the end-cap, the momentum transfer resulting from the bombardment of the end-cap by the particulates generates a higher end-cap velocity. The latter can be similar to that generated when the rupturing vessel contains only high pressure gas and a consequent greater gas expansion energy than available when the vessel contains both high pressure gas and particulates.The velocity of a `rocket' missile resulting from failure of a gas-pressurised vessel containing particulate material is greater than that generated by failure of a similar vessel containing only high pressure gas.     

CNG加气站危险性分析及事故预防措施研究

本文首先研究提出了国内外CNG加气站的一般组成结构，即调压计量系统、净化干燥系统、气体压缩系统、压缩天然气储存系统、控制系统和售气系统6个子系统；接着对近几年发生的加气站事故进行统计与分析，指出了加气站易发生事故的关键部位一售气系统、高压储气系统和CNG压缩系统；然后对CNG加气站的常见危险有害因素进行了辨识与分析，即高压、易燃易爆、易泄漏、点火源众多等；最后根据辨识结果，研究提出了建设安全监控预警与事故应急综合管理系统等具体事故预防措施。     

Predicting commercial fishing vessel disasters through a novel application of the theory of man-made disasters

Introduction: Vessel disasters (e.g., sinkings, capsizings) are a leading contributor to fatalities in the U.S. commercial fishing industry. Primary prevention strategies are needed to reduce the occurrence of vessel disasters, which can only be done by developing an understanding of their causes and risk factors. If less serious vessel casualties (e.g., loss of propulsion, fire, flooding) are predictors of future disasters, then reducing vessel casualties should in turn reduce vessel disasters and the accompanying loss of life. Method: This case-control study examined the association between vessel casualties and disasters using fishing vessels in Alaska during 2010–2015. Results: The findings show that vessels that experienced casualties within a preceding 10-year period were at increased odds of disaster. Other significant predictors included safety decal status and hull material. Practical Applications: The results of this analysis emphasize the importance of implementing vessel-specific preventive maintenance plans. At an industry level, specific prevention policies should be developed focusing on high-risk fleets to identify and correct a wide range of safety deficits before they have catastrophic and fatal consequences.     

基于QRA角度评价LNG储罐类型的选择

为提高LNG储存的安全性,基于QRA(定量风险评价),利用应急危险定位分析软件分别进行了LNG中小型储罐及大型储槽泄漏事故分析和LNG带压储罐充注压力专项对比分析。结果表明:立式圆柱常压储罐应选择高径比接近于1的罐体而压力罐的选择受高径比的影响很小;当对常压储罐高度有要求时,球形罐是比立式圆柱罐更好的选择;在大型LNG储槽中,常压储槽自身压力很大,可以起到抑制BOG(蒸发气体)产生的作用;在饱和状态下,压力罐的充注压力并非越小越好,需进行针对性分析计算,选取最适合的充注与设计压力。掌握LNG储罐事故后果与罐体形状与类型之间的关系可加强并丰富对其储罐类型选择的认识,可较好的为提高其储存安全性提供数据支撑与理论基础。     

基于故障树与灰色模糊理论的城市CNG加气站安全评价

城市CNG加气站安全状况好坏,直接影响到整个城市天然气汽车的安全运行,为此提出运用故障树分析法与灰色模糊理论对城市CNG加气站进行安全状况分析。通过对站内危险因素的分析,建立了加气站主要系统的故障树,得到引起加气站主要系统失效的70个基本事件,建立加气站安全评价指标体系,利用专家评分法对指标进行评分,利用层次分析法计算各指标层次相对权重。运用灰色关联分析法,计算参评数据序列与标准数据序列的关联系数矩阵,即得出模糊评判矩阵。再由模糊理论得出加气站安全等级,并给出相应的日常安全工作重点。用该方法对常州市CNG加气站进行安全评价,得出安全等级为Ⅱ级,这与加气站实际运行状况相符,说明用该方法对加气站进行安全评价是有效的、可靠的,能够为城市CNG加气站安全管理提供依据。     

Investigative consequence analysis: A case study research of beirut explosion accident

Around 15:00 GMT on August 4th, an explosion occurred in the warehouse facility storing Ammonium Nitrate (AN) at Beirut port, Lebanon. The explosion resulted in more than 178 fatalities and injured more than 6500 people, and also left an estimated 300,000 people homeless and registered as an equivalent to a 3.3 magnitude earth quake. The accident was considered to be the largest of its kind and the most severe anthropological disaster of the decade, the financial loss the nation was subjected to post the explosion was estimated to be around $ 15 billion as informed by the governor. The storage conditions of ammonium nitrate at Beirut port is not definitively known to anyone, and there is no documentation provided so far from the authorities regarding the same. This work focuses on the investigation & consequence analysis of the explosion using TNT equivalent approach. The overpressure and the impulse obtained from TNT calculations are used in probit models to assess the damages caused on human beings and structures. The results obtained in this investigative approach are then utilized to provide an analytical inference relative to the damage proxy map reported by the advance rapid imaging analysis team from NASA. Also, this work examines the existing standards, fire safety measures and legal regulations for ammonium nitrate facilities in the region. AN explosion during storage like other fire and explosion accidents are definitely preventable owing to the technological advancements and developments to prevent or extinguish controllable fires. The significance of this work relates to the methods for calculation of consequences of explosion that are happening due to the storage of highly hazardous explosive materials in excessive quantities and insists the necessity of incorporating adequate safety measures while storing such reactive and hazardous materials.     

储气井螺纹连接安全性有限元模拟分析及实验研究

储气井是一种新型压力容器,其螺纹连接的安全性目前既没有经过充分的研究论证,也没有经过实践的充分检验.通过实验和有限元模拟方法,对储气井螺纹连接的安全性进行了分析研究,得出了以下结论:(1)储气井模拟构件在极限内压实验过程中,在管体发生强度失效前,螺纹连接接头部位先发生泄漏失效,表明螺纹连接接头是储气井的薄弱环节;(2)储气井在极限内压条件下的破坏模式为“漏而不破”,这一特性有益于保障储气井的安全;(3)螺纹沟槽对于井管管体而言是一种“损伤”,但其并没有增高螺纹连接接头部位的结构应力,原因是因为接箍起到了加强作用;(4)螺纹连接接头部位螺纹牙底存在应力集中,可能会导致疲劳失效,建议设计时予以重点考虑,内压疲劳实验结果显示螺纹连接接头的抗疲劳性能满足储气井一般工况要求.