Integrated dynamic risk assessment of buried gas pipeline leakages in urban areas

In urban areas, buried gas pipeline leakages could potentially cause numerous casualties and massive damage. Traditional static analysis and dynamic probability-based quantitative risk assessment (QRA) methods have been widely used in various industries. However, dynamic QRA methods combined with probability and consequence are rarely used to evaluate gas pipelines buried in urban areas. Therefore, an integrated dynamic risk assessment approach was proposed. First, a failure rate calculation of buried gas pipelines was performed, where the corrosion failure rate dependent on time was calculated by integrating the subset simulation method. The relationship between failure probability and failure rate was considered, and a mechanical analysis model considering the corrosion growth model and multiple loads was used. The time-independent failure rates were calculated by the modification factor methods. Next, the overall evolution process from pipeline failures to accidents was proposed, with the accident rates subsequently updated. Then, the consequences of buried gas pipeline accidents corresponding to the accident types in the evolution process were modeled and analyzed. Finally, based on the above research, dynamic calculation and assessment methods for evaluating individual and social risks were established, and an overall application example was provided to demonstrate the capacity of the proposed approach. A reliable and practical theoretical basis and supporting information are provided for the integrity and emergency management of buried gas pipelines in urban areas, considering actual operational conditions.     

Methods and models in process safety and risk management: Past,present and future

The paper reviews past progress in the development of methods and models for process safety and risk management and highlights the present research trends; also it outlines the opinions of the authors regarding the future research direction in the field. Based on the open literature published in the leading journals in the field of safety, risk and reliability, the review covers the evolution of the methods and models developed for process safety and risk management. The methods and models are categorized as qualitative, semi-quantitative, quantitative and hybrid. The progress in the last few decades is discussed in the context of the past. Developments in the current decade formulate the basis of the present trends; future directions for research in these fields are also outlined. The aim of the article is to provide a historical development in this field with respect to the driving forces behind the development. It is expected that it will help researchers and industrial practitioners to gain a better understanding of the existing concepts. At the same time the aim is to provide direction to bridge the existing gaps through research and developments.     

Quantitative risk assessment of domino effect in Natech scenarios triggered by lightning

Lightning strike is the natural event more frequency causing Natech accidents involving atmospheric storage tanks. Despite the resulting fires have usually limited severity and only local effects, domino effect may cause the escalation of these primary events, possibly affecting nearby pressurized storages and process equipment, thus resulting in relevant increase in the potential area impacted. A methodology was developed for the quantitative assessment of risk due to domino effects caused by Natech accidents triggered by lightning. A comprehensive procedure was obtained, tailoring lightning risk assessment to include probabilistic models for domino escalation based on probit approach and combinatorial analysis. The methodology was applied to a case-study to evidence the shift in risk figures due to domino effect and the credibility of the secondary domino scenarios. The results of the case-study show that an increase up to two orders of magnitude with respect to risk calculated for conventional scenarios is possible when considering lightning-induced Natech primary scenarios and their escalation.     

区域自然灾害综合风险模糊随机评价方法

从自然灾害危险性、社会经济易损性和区域设防等多种角度建立了区域自然灾害综合风险评价指标体系。针对典型自然灾害综合风险评价影响因素具有随机性、模糊性和数据资料不精确等多种不确定性,利用蒙特卡洛方法模拟三角模糊数,把三角模糊数及其函数之间的运算简化为普通的实数之间的运算,从而建立区域自然灾害综合风险模糊随机评价模型。研究表明,在评价结果一致的前提下以置信区间形式表示的综合风险评价结果比其他常规方法,提供的信息更加丰富,充分反映了受多种不确定性因素综合影响的区域自然灾害综合风险评价的客观实际情况,研究结果可为区域防御自然灾害与提升综合抗灾能力提供决策依据。     

Chronicles of security risk assessment in process industries: Past,present and future perspectives

Security incidents around the world causes enormous loss in terms of life, economy, and environment. The 9/11 ′triggered the serious onset of research initiatives in the field of security with a more specific focus on the protection of high sensitive and hazardous facilities. It is well known that technology is advancing in a very rapid phase, proportionally increasing the security risk of the facilities. Conventional deterministic risk techniques widely found their applications in the earlier stage but owing to the increasing dynamic nature of the security risk, probabilistic dynamic risk assessment models were developed over time. In this article, the authors attempted to present the evolution of security risk concepts, their present status, and their future scope in a precise and consolidated form. The last 20 years of development in the security risk assessment concept involving deterministic and dynamic risk assessment models and applications in security risk assessment relevant to physical security are discussed in this article. The objective of the article is to outline the past, current and future directions of security risk highlighting their strength, weakness and limitations.     

海上石油平台工艺区风环境模拟及韧性评估*

为研究不同风向下海上石油平台工艺区的风场特征和系统韧性,采用Fluent软件从8种不同风向角度对海上平台工艺区风环境进行三维数值模拟,分析研究高于工艺区地面1.5,3,4.5 m水平风场风速分布特征,确定微静风区和强风速区面积,并以微静风区域占比为指标评估系统抗灾韧性。研究结果表明:风速激增区出现在障碍物前缘或侧翼;风口顺延形成强风道,风速介于1.6～3.1 m/s之间;系统韧性与微静风区占比呈现负相关,在1.5 m高度风场处,E-90°风向时微静风区域面积占比约为69%,工艺系统韧性较弱,风险较大;NW-315°风向时微静风区域面积占比约为9.6%,工艺系统韧性较强,风险较小;随着风场高度增大,各个风向系统韧性均有所提高,W-270°风向时系统韧性升幅达12.1%,N-0°风向时系统韧性升幅达12.24%。研究结果可为海上石油平台逃生路线设计、火气监控设备布置及提高平台自身抗灾韧性方面提供指导依据。     

Dynamic risk assessment of oil spill scenario for Three Gorges Reservoir in China based on numerical simulation

A novel method for dynamic risk assessment of oil spill accidents based on numerical simulation was presented in this paper. The dynamic risk assessment model was developed consisting of a comprehensive list of caused consequences like environmental damage, asset loss, health impact and social effect as well as emergency actions preventing these losses. Contributing events in the Mater Logic Diagram (MLD) of the dynamic risk assessment model were valued based on the simulated evolvement of oil contaminants under spill scenario on quasi-static fluid, which was obtained by coupling an oil spill model with hydrodynamic module in Jialing river of Three Gorges Reservoir in China after the impoundment of the reservoir to 175 m water level in 2010. Calculated result of dynamic risk as grade IV indicated that the assessed oil spill was not as catastrophic as we thought because of the slow transport of oil fractions on water surface and absence of dispersed oil in water body due to the quasi-static fluid, very gentle wind and effective emergency actions, as well as by the reason that rare agriculture or industrial crops exist in spill adjacent area.     

成品油站场工艺管道风险辨识与评价

为保障成品油站场工艺管道的安全平稳运行,在充分辨识风险因素的前提下,提出了一种基于KENT法和RBI的风险评价方法。首先,以风险机理分析为基础,采用SHEL模型从导致风险上升的直接原因（风险内因）和间接原因（风险外因）2个角度辨识了风险因素,并细化各因素指标项;然后借鉴KENT法,对各指标项进行评分量化;依据RBI法,采用风险外因体系修正风险内因体系的方式确定失效可能性;综合环境后果、人员后果与商业后果,明确失效后果的评价体系与计算方法;最后,结合失效可能性与失效后果进行风险评价,从风险等级和风险排序2方面为检维修决策提供依据。应用表明:该评价方法便于工艺管道风险评价的基层实施,可为基于风险的检维修决策提供有效技术支撑。     

A quantitative risk assessment tool for the external safety of industrial plants with a dust explosion hazard

A quantitative risk assessment (QRA) tool has been developed by TNO for the external safety of industrial plants with a dust explosion hazard. As a first step an industrial plant is divided into groups of modules, defined by their size, shape, and constructional properties. Then the relevant explosion scenarios are determined, together with their frequency of occurrence. These include scenarios in which one module participates, as well as domino scenarios. The frequency is partly based on casuistry.

A typical burning velocity is determined depending on the ignition type, the dust properties and the local conditions for flame acceleration. The resulting pressure development is predicted with the ‘thin flame model’. Module failure occurs when the explosion load exceeds thresholds, which are derived from single degree of freedom (SDOF) calculations for various types of modules. A model has been developed to predict the process of pressure venting after module failure and the related motion of launched module parts.

The blast effects of the primary explosion are based on results from calculations with BLAST3D. The blast and flame effects of the secondary external explosion due to venting are calculated using existing models. The throw of fragments and debris is quantified with a recently developed model. This model is based on trajectory calculations and gives the impact densities, velocities, and angles as output. Furthermore the outflow of bulk material is taken into account. The consequences for external objects and human beings are calculated using existing models. Finally the risk contours and the Societal risk (FN curve) are calculated, which can be compared to regulations.     

Comprehensive framework for underground pipeline management with reliability and cost factors using Monte Carlo simulation

A reliability model for underground pipeline management that can quantify the trade-off between risk reduction and increased maintenance costs in various underground piping management scenarios can be useful for many pipeline-maintenance decision-makers. In this paper, we propose a comprehensive framework for analyzing underground pipeline management options. Pipeline reliability is calculated using time-dependent and independent limit state functions with a probabilistic model and a deterministic model about the frequency of a failure occurrence event. The proposed framework includes the target reliability, consequences, and cost model, and has the advantage that it can be intuitively utilized for piping management decision-making. We conducted several case studies using a Monte Carlo simulation on pipelines in industrial complexes in Korea.     

渭河西咸段表层沉积物重金属赋存形态及风险评价

以渭河西咸段表层沉积物及其孔隙水为研究对象,采用ICPMS测定了As、Cd、Cr、Cu、Pb和Zn的含量,应用改进BCR法分析了沉积物重金属的赋存形态特征,基于风险评价编码法(RAC)和潜在生态风险指数法(PERI)评价了表层沉积物重金属的生态风险。结果表明:渭河西咸段表层沉积物已受到多种重金属的复合污染,孔隙水中As和Cd质量浓度在部分断面超过US EPA水生生物水质基准的持续基准质量浓度,表层沉积物中Cd质量比在所有断面、其余重金属质量比在部分断面超过其对应陕西省A层土壤背景值;表层沉积物重金属赋存形态各异,Cd主要存在于酸可溶态中,Pb主要存在于可还原态中,Cu、As和Cr主要存在于残渣态中,Zn在酸可溶态和残渣态上均有较高的比例,以残渣态为主;RAC评价显示,As和Cu处于低风险级或中风险级,Cd处于高风险级或极高风险级,Cr、Pb均为低风险级,Zn在低风险级和高风险级之间变化;RI评价显示,各断面处于轻微至极强生态风险,Cd处于较强至极强生态风险,其余重金属均属于轻微生态风险。     

Developing a new alternative risk assessment framework in the work sites by including a stochastic and a deterministic process: A case study for the Greek Public Electric Power Provider

An individual method cannot achieve the optimum risk-assessment result in the worksites, and future perspectives should focus on the parallel application of a deterministic approach with a stochastic approach. In particular, the risk analysis and assessment techniques of the deterministic (DET) approach are classified into three main categories: (a) the qualitative, (b) the quantitative, and (c) the hybrid techniques (qualitative-quantitative, semi-quantitative). Furthermore, the stochastic (STO) approach includes the classic statistical approach (CSA) and the accident forecasting modeling (AFM). The objective of this paper is triple: (a) the presentation and classification of the main risk analysis and risk assessment methods and techniques of the deterministic approach and the stochastic approach as well, (b) the development and presentation of a new alternative risk assessment framework (called as STODET) including a stochastic and a deterministic process, and (c) the application of STODET in the Greek Public Power Corporation (PPC) by using occupational accidents that have been recorded, during the 17-year period of 1993-2009. In particular, the STODET application proves that required actions (or suppressive measures) are essential and must be taken in a medium-term period (1 working year) for abolishing the hazard sources.