Dynamic probability assessment of urban natural gas pipeline accidents considering integrated external activities

Urban gas pipelines usually have high structural vulnerability due to long service time. The locations across urban areas with high population density make the gas pipelines easily exposed to external activities. Recently, urban pipelines may also have been the target of terrorist attacks. Nevertheless, the intentional damage, i.e. terrorist attack, was seldom considered in previous risk analysis of urban gas pipelines. This work presents a dynamic risk analysis of external activities to urban gas pipelines, which integrates unintentional and intentional damage to pipelines in a unified framework. A Bayesian network mapping from the Bow-tie model is used to represent the evolution process of pipeline accidents initiating from intentional and unintentional hazards. The probabilities of basic events and safety barriers are estimated by adopting the Fuzzy set theory and hierarchical Bayesian analysis (HBA). The developed model enables assessment of the dynamic probabilities of consequences and identifies the most credible contributing factors to the risk, given observed evidence. It also captures both data and model uncertainties. Eventually, an industrial case is presented to illustrate the applicability and effectiveness of the developed methodology. It is observed that the proposed methodology helps to more accurately conduct risk assessment and management of urban natural gas pipelines.     

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.     

An integrated methodology to manage risk factors of aging urban oil and gas pipelines

Aging urban oil and gas pipelines have a high failure probability due to their structural degradation and external interference. The operational safety of the aging urban oil and gas pipeline is challenged by different hazards. This paper proposes a novel methodology by integrating an index-based risk evaluation system and fuzzy TOPSIS model for risk management of aging urban oil and gas pipelines, and it is carried out by evaluating the priority of hazards affecting pipeline safety. Firstly, the hazard factors of aging urban oil and gas pipelines are identified to establish an index-based risk evaluation system. Subsequently, the fuzzy TOPSIS model is employed to evaluate the importance of these hazard factors and to decide which factors should be managed with priority. This work measures the importance of a hazard factor from three aspects, i.e. occurrence (O), severity (S) and detectability (D), and the weights of these three parameters are determined by a combination weight method. Eventually, the proposed methodology is tested by an industrial case to illustrate its effectiveness, and some safety strategies to reduce the operational risk of the pipeline are presented. The proposed methodology is a useful tool to implement more efficient risk management of aging urban oil and gas pipelines.     

燃气管网定量风险分析方法综述

以城市燃气管网的风险为研究对象,分析并提出一种可用于城市燃气管网定量风险分析的新思路,包含了不同事故后果及其物理模型的分析即事故可能性分析、后果分析和风险评价,分为失效事故假定、泄漏率计算、物理效应计算、致死率计算、风险值计算、风险评价等环节;整理、研究城市燃气管网定量风险分析所涉及的多种物理模型,并通过比较不同模型的特点,分析各个模型的不足之处;最后针对国内外研究现状及燃气管网风险的特点,指出研究发展方向:研究风险在燃气管网内的传播,提出燃气管网相继失效的风险分析方法。所提出的分析思路、计算方法可与工程应用相结合。     

An integrated quantitative risk analysis method for natural gas pipeline network

Natural gas industry is developing rapidly, and its accidents are threatening the urban safety. Risk management through quantitative assessment has become an important way to improve the safety performance of the natural gas supply system. In this paper, an integrated quantitative risk analysis method for natural gas pipeline network is proposed. This method is composed of the probability assessment of accidents, the analysis of consequences and the evaluation of risk. It is noteworthy that the consequences analyzed here include those of the outside and inside gas pipelines. The analysis of consequences of the outside pipelines focuses on the individual risk and societal risk caused by different accidents, while those of the inside pipelines concerns about the risk of the economic loss because of the pressure re-distribution. Risk of a sample urban gas pipeline network is analyzed to demonstrate the presented method. The results show that this presented integrated quantitative risk analysis method for natural gas pipeline network can be used in practical application.     

基于IAHP和灾变链式方法的城市油气管道风险诱因与预警研究

城市油气管道穿越城区街道、建筑和居民区等特殊地段,保障其安全运行具有重要意义。为实现城市油气管道风险早期预警,基于城市与野外长输油气管道风险对比分析,识别城市油气管道风险预警指标;建立城市油气管道风险预警指标体系,采用区间层次分析法对预警指标重要度进行定量排序,确定关键预警监测点;并依据灾变链式理论,构建城市油气管道重大事故灾变链式模型,研究管道风险演化过程,发现灾变前兆进行断链减灾。研究结果表明:“腐蚀”及“第三方破坏”占据城市油气管道失效致因比重最大,风险因子“油气管道与市政管道距离”以及“城市工程施工作业”应作为城市油气管道重点监测点。同时,围绕城市油气管道风险预警需致力于孕源断链。     

Dynamic failure probability analysis of urban gas pipeline network

The gas pipeline network is an essential infrastructure for a smart city. It provides a much-needed energy source; however, it poses a significant risk to the community. Effective risk management assists in maintaining the operational safety of the network. The risk management of the network requires reliable dynamic failure probability analysis. This paper proposes a methodology of condition monitoring and dynamic failure probability analysis of urban gas pipeline network. The methodology begins with identifying key design and operational factors responsible for pipeline failure. Subsequently, a causation-based failure model is developed as the Bowtie model. The Bowtie model is transformed into a Bayesian network, which is analyzed using operational data. The key contributory factors of accident causation are monitored. The monitored data is used to analyze the updated failure probability of the network. The gas pipeline network's dynamic failure probability is combined with the potential consequences to assess the risk. The application of the approach is demonstrated in a section of the urban gas pipeline.     

基于AHP-熵权法的城市燃气管道风险评价*

为全面、客观地评价城市燃气管道风险,提出1种基于AHP-熵权法的城市燃气管道风险评价模型。该模型基于风险评价理论,结合管道失效可能性与后果严重性,构建包含105个评价底因素的城市燃气管道风险评价指标体系。针对城市燃气管道风险因素的复杂性和模糊性,引入模糊数学思想和方法,结合AHP和熵权法确定评价指标的综合权重,再运用模糊综合评价法和风险分析矩阵评估燃气管道风险等级。结果表明:该评价模型风险评价结果与实际情况相符,可为城市燃气管道风险预警与管理提供依据。     

An urban pipeline accident model based on system engineering and game theory

Urban pipeline accidents are caused by complex social-technical factors, in which urban communities and pipeline systems are involved. Such accidents can thus be investigated from the viewpoint of system engineering. System-Theoretic Accident Model and Processes (STAMP) is a systemic method for safety assessment, which has been adopted in many domains. This approach can provide deep insights of accident causes by considering direct and indirect factors. Meanwhile, competition and cooperation between stakeholders in accidents are observed. Therefore, these parties can also be analyzed with the game theory. That is, stakeholders in STAMP can be regarded as players in game. The aim of this paper is to provide a new insight to analyze urban pipeline accidents by considering both STAMP and game theory. In this paper, we proposed an accident model for urban pipelines, with a case study of China-Qingdao pipeline accident occurred in 2013. We concluded that accident reasons can be investigated in-depth and lessons can be learned from analyzing causal factors by using STAMP. Based on results generated from STAMP, we applied the game theory to analyze roles that government and companies act in the China-Qingdao urban pipeline accident. The results show that current punishment and incentive systems are incomplete, lacking of the driving force and constraining force for the stakeholders involved in the accident.     

基于多维云模型的埋地并行油气管道风险评价研究*

为提高风险评价准确性以有效支撑管道完整性维护,保证油气管道在多管并行敷设下安全运行,提出1种基于博弈论-多维云模型的风险评价方法。首先,从并行间距、土壤压实度、土壤导热系数、介质流速、管径、埋深、应急响应时间、上下游截断阀间距等方面建立并行管道风险评价指标体系,为降低传统赋权方法的主观性,通过结合熵权法改进层次分析法（AHP）,从而确定主客观权重,再经博弈论组合赋权法综合计算指标权重;其次,运用多维云模型理论确定风险等级,通过修正各风险评分项的等级区间结合指标权重,计算出各级的综合确定度,并进行等级评判;最后,将该方法应用于工程实例。研究结果表明:所评价管段的指标风险处于中等风险水平,风险可接受,管段的整体风险评价结果良好,有利于并行管道安全管理;实例证明该评价方法具有较好的适用性。     

天然气管道不同孔径泄漏失效概率量化方法研究*

为研究不同孔径泄漏下天然气管道失效概率,首先基于EGIG数据库和UKOPA数据库天然气管道历史失效数据,计算由不同失效原因导致3种孔径泄漏所占比例;然后将我国管道各原因基础失效概率按照对应比例分别进行修正,获得较适用于我国天然气管道特点的不同孔径泄漏基础失效概率;最后分别考虑第三方破坏、腐蚀、施工缺陷/材料失效、误操作、自然力破坏5种失效原因,完成对天然气管道不同孔径泄漏基础失效概率的修正计算。研究结果表明:小孔泄漏、中孔泄漏和破裂泄漏的基础失效概率分别为0.173,0.128,0.048次/（103 km·a）;修正因子包括管径、埋深、壁厚、管龄、防腐层类型、管道所处区域,上述因子能够满足不同场景下天然气管道失效概率的修正计算;概率量化方法综合考虑失效原因、泄漏孔径以及管道本体信息,能够定量化预测天然气管道失效概率,为天然气管道定量风险评价提供数据支撑。     

Corrosion failure probability analysis of buried gas pipelines based on subset simulation

Corrosion is the main reason for the failure of buried gas pipelines. For effective corrosion failure probability analysis, the structural reliability theory was adopted in this study to establish two calculation models for pipeline corrosion failure: the pressure failure model and von Mises stress failure model. Then, two calculation models for the corrosion failure probability were established based on a corrosion depth growth model obtained from actual survey data of soil corrosion characteristics. In an example, Monte Carlo simulation (MCS) and subset simulation (SS) were used to analyze the corrosion failure probability of pipelines, and the results were compared. SS can compensate for the shortcomings of MCS as it has higher computational efficiency and accuracy. Therefore, SS was adopted to simulate variations in the corrosion failure probability of buried pipelines with the service time for the two failure probability calculation models, which were applied to a natural gas pipeline located in a chemical industry park in Zhuhai, China. A sensitivity analysis was carried out on the relevant parameters that affect the failure probability. The results showed that multiple loads caused by the covering soil, residual stress, temperature differential, and bending stress have a non-negligible effect on the pipeline reliability. The corrosion coefficients gradually become the most important factors that affect the failure probability with increased service time. The proposed methodology considers the actual operating conditions of pipelines to provide a reliable theoretical basis for integrity management.     

城市天然气管道风险特征与肯特法的改进

根据城市高压天然气管道特点,将适合于城市天然气管道风险分析的肯特评分法加以改进,包括调整评分项目和事故因素权重,使其成为适于城市天然气管道的风险分析法。将改进后的肯特评分法应用于常州21km高压天然气管道的风险评价,得出8个相对高风险管段,其分析结果可作为安全管理人员合理分配维护资源的理论依据。工程应用实例证明:改进后的肯特法具有较强的可行性,是城市高压天然气管道风险评估的有效工具。     

1种城市燃气管道风险评估模型及其应用研究

为科学评估燃气管道在复杂且敏感的城市环境中个人风险可接受情况,促进城市和谐稳定。以燃气管道泄漏射流火灾为事故场景,在常规评估基础上结合管道地区特点,构建基于公众可接受伤亡风险标准的评估模型,并通过案例分析,开展城市燃气管道个人风险定量评估研究。结果表明:我国城市燃气管道个人死亡风险、个人受伤风险可接受标准的建议值分别为5.00×10-6和2.74×10-5,其在一般情况下的公众可接受风险标准建议值范围为5.00×10-7~5.50×10-5和2.74×10-6~4.11×10-4;公众的伤亡风险感知偏差将直接影响风险评估结果,及时有效地对目标群体进行风险疏导以改善其风险认知,有助于避免公众风险感知偏差引发的负面社会效应。     

Quantification of impact of line markers on risk on transmission pipelines with natural gas

The paper presents a model for the assessment of the influence of line markers on risk on transmission pipelines with natural gas. The impact of line markers on risk is determined as a function of the line marker recognisability, which in turn depends on the ability to discern a line marker from a distance. The model is based on physical properties of line markers, especially on their colour, measures and the colour of the environment. These properties served to quantitatively assess the discernability of two most frequently encountered types of line markers. Calculated distances at which a particular line marker is discernible were compared to the average distances between two line markers. Risk reduction factors were derived from the comparison between the calculated results and the data from the appropriate hazardous event database. Results of the model indicated significant dependence of the risk reduction factor due to line markers on the distance between two line markers and the weather conditions. The model shows its flexibility through its distinct dependence on local conditions along the pipeline route. It can serve as a supplement to the existing models for quantitative risk assessment on pipelines used in natural gas transportation.     

A hybrid model for human factor analysis in process accidents: FBN-HFACS

Human factors are the largest contributing factors to unsafe operation of the chemical process systems. Conventional methods of human factor assessment are often static, unable to deal with data and model uncertainty, and to consider independencies among failure modes. To overcome the above limitations, this paper presents a hybrid dynamic human factor model considering Human Factor Analysis and Classification System (HFACS), intuitionistic fuzzy set theory, and Bayesian network. The model is tested on accident scenarios which have occurred in a hot tapping operation of a natural gas pipeline. The results demonstrate that poor occupational safety training, failure to implement risk management principles, and ignoring reporting unsafe conditions were the factors that contributed most failures causing accident. The potential risk-based safety measures for preventing similar accidents are discussed. The application of the model confirms its robustness in estimating impact rate (degree) of human factor induced failures, consideration of the conditional dependency, and a dynamic and flexible modelling structure.     

城市天然气管道泄漏的危害分析

城市天然气系统的管道化很大程度上便利了人们的生活,但与此同时管道泄漏也造成灾难性后果.采用高斯烟团扩散模型,对天然气管道瞬间泄漏的扩散行为进行模拟,计算出天然气管道泄漏后的最大危害距离,其结果可以为应急救援提供决策支持.     

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.     

An integrated EDIB model for probabilistic risk analysis of natural gas pipeline leakage accidents

Natural gas pipeline construction is developing rapidly worldwide to meet the needs of international and domestic energy transportation. Meanwhile, leakage accidents occur to natural gas pipelines frequently due to mechanical failure, personal operation errors, etc., and induce huge economic property loss, environmental damages, and even casualties. However, few models have been developed to describe the evolution process of natural gas pipeline leakage accidents (NGPLA) and assess their corresponding consequences and influencing factors quantitatively. Therefore, this study aims to propose a comprehensive risk analysis model, named EDIB (ET-DEMATEL-ISM-BN) model, which can be employed to analyze the accident evolution process of NGPLA and conduct probabilistic risk assessments of NGPLA with the consideration of multiple influencing factors. In the proposed integrated model, event tree analysis (ET) is employed to analyze the evolution process of NGPLA before the influencing factors of accident evolution can be identified with the help of accident reports. Then, the combination of DEMATEL (Decision-making Trial and Evaluation Laboratory) and ISM (Interpretative Structural Modeling) is used to determine the relationship among accident evolution events of NGPLA and obtain a hierarchical network, which can be employed to support the construction of a Bayesian network (BN) model. The prior conditional probabilities of the BN model were determined based on the data analysis of 773 accident reports or expert judgment with the help of the Dempster-Shafer evidence theory. Finally, the developed BN model was used to conduct accident evolution scenario analysis and influencing factor sensitivity analysis with respect to secondary accidents (fire, vapor cloud explosion, and asphyxia or poisoning). The results show that ignition is the most critical influencing factor leading to secondary accidents. The occurrence time and occurrence location of NGPLA mainly affect the efficiency of emergency response and further influence the accident consequence. Meanwhile, the weight ranking of economic loss, environmental influence, and casualties on social influence is determined with respect to NGPLAs.