基于贝叶斯网络的城市地下燃气管网动态风险分析

为研究城市燃气管网风险的动态性,针对传统风险分析方法的局限性,提出基于贝叶斯网络的燃气管网动态风险分析方法。构建燃气管网失效蝴蝶结模型并将其转化为贝叶斯网络模型;在事故发生状态下更新事件失效概率,识别出关键因素;根据异常事件数据和贝叶斯理论,对基本事件失效概率进行实时动态改变;随之更新管网失效及各后果发生的概率,从而实现管网的动态风险分析。研究结果表明:该方法克服了传统风险分析方法的不足,可动态反映燃气管网失效和事故后果发生概率随时间变化的特征,能够为城市地下燃气管网的风险分析与事故预防提供参考。     

城市天然气管网预警系统的研究与实现

随着城市天然气管网密度加大,由于天然气管理手段滞后导致的天然气泄漏事故急剧增加。基于GIS技术并结合燃气管网定量风险分析(QRA)模型,提出利用定量风险分析模型实现管网风险预警的方法。结合C#+ArcEngine编程技术,开发城市天然气管网预警系统,实现管网失效率分析、燃气事故扩散模拟、火灾及爆炸模拟、个人风险等值线绘制、社会风险分析等功能,能够进行区域性事故后果预测、个人风险和社会风险计算、安全性评价及应急预案编制等项工作。     

基于改进Bow-tie模型的城镇燃气管网风险分析

燃气管网是城镇中的重大危险源,一旦发生事故,后果多数较为严重。为更清晰地了解事故发生原因、后果,制定预防、减缓措施,笔者提出改进Bow-tie模型对城镇燃气管网进行风险分析。改进Bow-tie模型从人、机、环、管四方面分析事故原因,从人员、财产、环境、社会四方面分析事故后果,将风险识别、风险分析、风险评估、风险控制、风险管理在图中展示,并为燃气管网事故提出预防和减缓措施,降低事故率。结果表明应用改进Bow-tie模型可直观掌握事故全过程动态,清晰了解事故的起因、结果,对分析燃气管网泄漏事故具有重要意义。     

基于风险的城市埋地燃气管道安全评价模型及应用

城市埋地燃气管道一旦失效会产生泄漏,甚至引发火灾爆炸等事故,造成人员伤亡和财产损失等严重后果,影响社会稳定,因此其安全运行十分重要。由于城市地下环境的复杂性,使得埋地燃气管道失效的因素多种多样,且具有模糊性;由于城市地面状况各异,所以构成失效后果的因素也具有不确定性。文章以某市在役燃气管道为例,使用模糊数学语言表达了埋地燃气管道的失效可能性和失效后果,采用模糊综合评价模型对燃气管道的失效可能性和失效后果进行了评价,并以美国石油协会(API)风险矩阵表征了埋地燃气管道的风险等级,得到不同管道单元的风险级别和管道单元数,根据不同的风险等级采取不同的策略或措施,完善管道的完整性管理,降低管道的使用风险,确保城市燃气管网的正常安全运行。     

城镇燃气管道第三方施工损伤风险评价方法研究

针对第三方施工对城镇燃气管道的不利影响,提出一种半定量风险评价方法。首先,基于“人—机—环境—管理”系统确定失效因素,利用G2赋权法对因素赋权,并引入物元模型分析失效可能性;然后,建立喷射火焰、闪火和蒸气云爆炸的数学模型计算管道泄漏的伤害面积,确定失效后果等级;最后,根据API 581中的风险矩阵得出燃气管道第三方施工破坏风险等级。实例分析表明,该方法兼具定性评价与定量评价的优点,能更加准确有效地进行风险分析,确定风险等级。     

城市燃气管网泄漏蒸气云爆炸事故风险评估

为解决城市燃气管网泄漏蒸气云爆炸事故的风险定量评估问题,提出一种网格化的风险评估方法。首先,综合分析管道故障的影响因素和管道泄漏蒸气云爆炸的后果损失类型,并计算管道的失效概率和管道某一点泄漏导致蒸气云爆炸后在一个网格内的后果损失货币量化值,两者相乘得到该网格中心点的风险值。然后,利用叠加场的原理,将对网格中心点有影响的管段各点风险值耦合叠加,得出各网格中心点的总风险值,进而绘制出评估区域的风险等值线。最后,应用于实例,绘制出某地区燃气管网泄漏蒸气云爆炸的风险等值线,根据风险可接受准则,评价区域划分为特别、重点和一般防护区,并得到相应的防护区域范围。结果表明：网格化的风险评估方法能够准确评估城市燃气管网泄漏蒸气云爆炸事故风险,并使区域风险划分相比传统方法更加精细和形象,有助于提高社会安全防护物资利用率。     

天然气管道失效个人生命风险评价技术研究

为研究天然气长输管道失效个人生命风险,提出一种以人员伤亡概率为指标的天然气管道失效后果风险评价方法。基于天然气管道的失效概率和失效致死长度参数,建立天然气长输管道生命风险评价模型。用该模型,对国内某城市住宅小区内带腐蚀缺陷的天然气管线进行定量风险分析。借鉴英国天然气输送公司数据,确定天然气管线个人生命风险值。案例证明,用所建立的天然气管道失效个人生命风险评价模型能够有效地分析带缺陷天然气管道失效后果,实现天然气管道的个人安全生命风险全定量评价。     

城市天然气管道半定量风险评估方法研究

以实现天然气管道风险评估资源的合理分配，确定天然气管道定量风险评估的重点为目标，改进燃气管道风险评估方法的肯特模型，探求城市天然气管道的半定量风险评估方法；分析了城市埋地天然气管道失效可能性与失效后果的影响因子，并研究其评分标准；分别给出了城市天然气管道失效可能性与失效后果的等级划分标准，并运用半定量风险矩阵进行燃气管道单元的风险初步排序，以确定高风险管道单元；对城市天然气管道进行半定量风险评估，可为识别管道沿线高风险后果区域、风险动态排序、风险预警及制定事故应急预案等提供科学依据和方法指导，具有重要的工程应用价值。     

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。     

一种城市燃气管网泄漏风险动态计算模型

为科学地评估并及时控制城市燃气管网泄漏的风险,采用贝叶斯网络(BN)与地理信息系统(GIS)相结合的方法,建立燃气管网泄漏风险动态计算模型。首先,利用故障树(FT)系统地分析管网泄漏事故,考虑到管网服役时间和外界干扰事件的动态性,将建成的FT映射到BN中,进而动态计算燃气管网的泄漏概率;然后运用GIS技术对管网泄漏后果的严重度指标进行赋值,并将动态泄漏概率和后果严重度值结合,建立上述模型;最后,以某区域的燃气管网为研究对象,验证该模型的有效性。结果表明:该模型能够综合时间因素以及突发事件对管网泄漏的影响,实现对管网泄漏风险的动态计算和可视化显示。     

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 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.     

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.     

A new pre-assessment model for failure-probability-based-planning by neural network

At present, the prediction of failure probability is based on the operation period for laid pipelines, and the method is complicated and time-consuming. If the failure probability can be predicted in the planning stage, the risk assessment system of gas pipeline will be greatly improved. In this paper, the pre-laying assessment model is established to minimize risk of leakage due to piping layout. Firstly, Fault Tree Analysis (FTA) modeling is carried out for urban natural gas pipeline network. According to expert evaluation, 84 failure factors, which can be determined in the planning stage, are selected as the input variables of the training network. Then the FTA model is used to calculate the theoretical failure probability value, and the failure probability prediction model is determined through repeated trial calculation based on BP (Back Propagation Neural Network) and RBF (Radial Basis Function), for obtaining the optimal network parameter combination. Finally, two prediction models are used to calculate the same example. By comparing our pre-assessment model with the theoretical prediction consequences of the fault tree, the results show that the error of RBF prediction model can be close to 3%, which proves the validity and correctness of the method.     

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.     

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。     

城镇燃气管道动火作业安全评价

针对城镇燃气管道动火作业的高危险性,为保障生命财产安全,提出一种基于未确知测度的安全评价方法。首先,从动火施工作业的前、中、后3个阶段对整个作业过程进行安全分析,并基于作业的前阶段建立安全评价体系。然后,引入未确知测度模型,将因素的量化值与测度函数结合得出测度评价矩阵,采用变异系数法处理评价矩阵,确定各危害因素的客观权重。最后,根据测度评价矩阵与因素权重得出动火作业的安全等级,并对危害因素进行排序。实例结果表明:应用该方法能有效地确定出城镇燃气管道动火作业的安全等级,对于不安全的施工作业,可根据排序确定高危险因素,并采取措施降低其危险性,提高整个动火作业过程的安全性。     

基于贝叶斯网络的气井井筒完整性风险评价

井筒完整性失效是气井生产中的主要风险,为有效评价井筒完整性风险,应用贝叶斯网络的推理与学习能力,建立了基于贝叶斯网络和Noisy-OR gate模型的井筒完整性失效概率计算方法和风险评价模型。由故障树分析将井筒分为管柱、水泥环密封性、井口装置、水力屏障和其他部件5个评价单元,确定了各单元的主要风险因素,建立了井筒完整性失效的贝叶斯网络拓扑结构;由Noisy-OR gate模型和历史数据,确定了贝叶斯网络的条件概率参数;将基于贝叶斯网络的失效概率与层次分析法相结合,确定了风险评价指标和等级划分标准;建立了气井井筒完整性风险评价方法。结果表明,该方法实现了井筒完整性失效概率的定量计算、风险的定量评价和主要风险因素的反向推理,可为预防和控制井筒完整性失效提供决策依据,有助于降低井筒完整性失效风险。