油气管道体积型缺陷弹塑性有限元分析

根据弹塑性有限元模型,通过有限元分析软件ANSYS对近似抛物面的燃气管道的外腐蚀缺陷、内腐蚀缺陷及凹痕缺陷进行失效分析,得到缺陷管道的最大等效应力和最大等效塑性应变。与无缺陷的管道进行对比,分析管道失效压力、爆破压力。同样形貌的缺陷,凹痕缺陷的管道失效压力和爆破压力均最大,外腐蚀缺陷的管道失效压力和爆破压力均最小。     

基于事件树的混凝土桥梁全寿命检测维修策略

文中采用事件树模型以桥梁全寿命总成本最小为目标,采用可靠指标限值作为约束,建立钢筋混凝土桥梁全寿命最优决策方法。研究抗力退化、检测精度和失效造成的损失等对结构全寿命总成本的影响,进一步确定对检测与维修策略的影响。研究表明,随着检测次数的增加,桥梁全寿命周期总成本先减小并达到最优而后增加,可靠指标一直增大;抗力退化严重时需要更多的检测和维修确保总成本达到最优;检测精度和失效造成的损失影响总成本更显著。     

燃气管道爆管物理爆炸对并行邻管的冲击行为

针对燃气管道爆管冲击同沟并行管道的潜在威胁,基于能量相当法则,确定爆管等效TNT当量。采用光滑粒子流体动力学-有限单元法(SPH-FEM),在验证有限元模型精度的基础上,基于软件LS-DYNA和LS-PREPOST建立缺陷管道-土壤-炸药耦合的三维实体爆炸模型,研究爆炸荷载下腐蚀尺寸(腐蚀深度及投影面半径)对缺陷管道动力响应的影响。结果表明:SPH-FEM耦合法可形象展示土体鼓包的宏观形态且模拟所得结果与试验数据吻合较好;管体最大应力的部位与腐蚀缺陷数量有关,单腐蚀缺陷管道的最大应力位于腐蚀中心处,双腐蚀缺陷管道的最大应力部位位于两腐蚀缺陷间的未腐蚀区域;双腐蚀管道的最大应力较单腐蚀管道大,最大振速较单腐蚀管道小,双腐蚀管道较单腐蚀管道发生失效的可能性大。随着腐蚀深度的增大,单腐蚀和双腐蚀管体的最大应力均增大;腐蚀深度对管体振速的影响较小,不同腐蚀深度下,单腐蚀或双腐蚀管道的振速时程曲线均基本重合,单腐蚀和双腐蚀管道振速时程曲线形式基本一致,单腐蚀较双腐蚀管道最大振速大。不同投影面半径下,单腐蚀和双腐蚀管道的应力时程曲线均基本重合,振速曲线也基本重合,说明投影面半径对管道的动力响应影响较小;单腐蚀较双腐蚀管道最大振速大;随着腐蚀投影面半径的增大,管体的最大应力增大。     

顺德某片区截污管网CCTV检测与修复技术

顺德某片区已建截污管网年代久远、长期缺乏管养。应用CCTV检测技术开展普查,根据检测结果统计,发现管道存在不同程度的破裂、脱节、渗漏及腐蚀等结构性缺陷和树根、障碍物、沉积及结垢等功能性缺陷,已经严重影响到管网的运行。结合现场实际情况,优先解决3级以上结构性缺陷和所有功能性缺陷。应用非开挖修复技术,对管道采取整体修复和局部点状修复。修复后管道恢复正常运行,极大提升了该片区的截污效率。     

面状腐蚀管道承压能力的仿真分析

埋地原油输送管道经常受到原油、土壤等腐蚀,管道内外壁会出现不同形状的腐蚀缺陷,因此会产生应力集中,并削弱管道承压能力,必须对其进行剩余强度评价.本文应用ANSYS软件对含外壁腐蚀管道进行分析计算,得到不同缺陷尺寸的管道在内压作用下的Mises应力,得出腐蚀参数与等效应力的关系曲线,结果表明,有限元法对于分析管道的剩余强度是可靠的,可为外壁腐蚀管道的安全评价提供较为准确和经济的相关依据.     

测速对远场涡流管道缺陷检测的影响

在基于远场涡流的管道缺陷定量检测中,在距离激励线圈2-8倍管道内径的位置设置了2个物理属性完全相同的接收线圈来实现管道缺陷的检测。当仪器以一定速度进行管道检测时,由于管道作为闭合导体,当产生磁场的激励线圈与管道产生相对速度时,由楞次定律可知,管道会产生阻碍磁场变化的感应电流影响缺陷检测。为了直观分析仪器速度效应给检测带来的影响,利用ANSYS有限元仿真软件建立远场涡流双线圈检测模型进行了仿真,鉴于远场涡流为低频测试以及仪器参数自身等限制,仪器存在最大检测速度,在最大检测速度以内仿真结果表明:随着仪器运行速度的增加两个检测线圈上的感应电压幅值减小,相位也有减小的特征,进一步反应速度对管道缺陷定量检测的影响,将检测的特征相位转化成管道壁厚,经过误差分析确定在最大速度范围内,远场涡流检测中由仪器速度效应带来的误差很小。     

CCTV用于成都市锦兴路排水管道检测与评估

以成都市锦兴路排水管道非开挖检测工程为例,介绍了闭路电视(CCTV)检测技术在城市污水管道功能检测评估中的应用,包括管道预处理、水位判断以及CCTV检测。根据CCTV检测结果,该段排水管道存在39处缺陷,主要为腐蚀和沉积,且腐蚀管道为整段腐蚀,总长度达到890 m。结合国家行业标准对该排水管道进行了结构性和功能性评估。结构性评估结果表明,该段管道修复等级为二级,管道在短期内不会发生破坏,但应做修复计划;功能性评估结果表明,管道养护等级为四级,输水功能受到严重影响,应立即对淤积的管道进行处理。     

小直径排水管道非开挖修复预处理技术应用研究

对待维修的管道进行预处理是非开挖修复技术的关键环节和先决条件,可以显著加快管道非开挖修复的进度。因此主要对小直径排水管道预处理措施进行研究,介绍了管道检测、清洗、注浆及缺陷预处理等内容。其中,着重研究了如何采用顶进挤压设备并结合套钢圈的方式,实现小直径排水管道的预处理。该技术适用于修复城镇小直径排水管道结构性缺陷或功能性缺陷。其成功的运用可为今后非开挖修复小直径排水管道提供范例。     

埋地钢管外防腐系统检测和评价技术的研究与应用

采用多频管中电流法、埋地外防腐检测仪、超声波导波技术，对埋地钢质管道外防腐等级、破损位置及阴极保护效果进行检测，并结合埋地钢质管道外腐蚀缺陷评价方法对腐蚀状况进行评价，通过评估以确定管道的剩余强度和剩余寿命。     

基于贝叶斯网络的城市燃气管道泄漏风险研究

为了研究城市燃气管道泄漏风险,基于贝叶斯网络理论建立城市燃气管道泄漏风险模型,对模型进行风险预测、风险诊断及敏感节点分析。结果表明,城市燃气管道泄漏风险主要由管道腐蚀、管道缺陷、人为因素及自然环境等因素造成;由第三方破坏、应力破坏及管道腐蚀造成管道破裂而引发城市燃气管道泄漏事故的风险概率最大;对施工破坏、恶意破坏、内防腐失效、地质灾害及材料缺陷等风险因素进行控制是城市燃气管道泄漏风险管理的关键点。     

Inspection and maintenance planning of pipeline under external corrosion considering generation of new defects

Safe operation of aging pipeline systems under external corrosion can be achieved through inspection and maintenance programs. Tools used for the pipeline inspection are uncertain in detecting a corrosion defect and in sizing a detected defect. The process of generation of new corrosion pits is an uncertain process. These uncertainties must be taken into account in the reliability analysis and in the pipeline inspection and maintenance planning. In this paper the effect of corrosion defect size on the remaining pipeline strength is modeled by a Markov process. Analytical solution of the probability transition matrix is obtained by solving the Kolmogorov forward differential equation. The matrix of probability transition function, the probability of defect detection and the probability distribution of sizing a detected defect is incorporated in estimating the probability of failure. The generation of new corrosion defects is modeled by a Poisson process. The optimal inspection and maintenance schedules are selected based on the reliability constraint. The sensitivity of optimal inspection schedule to the quality of inspection tools and to maintenance criteria is illustrated through examples.     

Multi-objective maintenance strategy for in-service corroding pipelines using genetic algorithms

Abstract

The multi-objective optimisation technique utilising genetic algorithms is employed to develop the optimal maintenance strategy for corroding oil and gas pipelines. The objective functions of the optimisation are the maximum annual conditional probabilities of small leak and burst, respectively, of all the pipe joints included in the pipeline segment over a predefined time horizon, and the total present-value cost of corrosion repair. The allowable annual probabilities of small leak and burst, and the annual repair budget are treated as constraints in the optimisation. The proposed optimal maintenance strategy is illustrated using a natural gas pipeline segment consisting of 90 corroding pipe joints. The analysis results indicate that a diverse set of solutions are included in the obtained Pareto front, which allow the decision-maker to select the maintenance plan achieving the desired tradeoff between the reliability and cost. The approach presented in this study can be incorporated in the practical optimal maintenance planning of corroding pipelines subjected to safety and resource constraints.     

Inspection and maintenance planning of underground pipelines under the combined effect of active corrosion and residual stress

In this paper, a maintenance policy is proposed for pipelines subjected to active corrosion and residual stress, by taking into account imperfect inspection results. The degradation of the pipeline is induced by uniform corrosion, leading to losses of the pipe wall thickness. Localized corrosion is not considered herein, as neither pitting nor crevice corrosion are strongly influenced by external loading conditions and, hence, are not critical in structural strength considerations. When the corroded layers are removed, strain relaxation occurs, causing a redistribution of residual stresses. In parallel, the inspection is applied to detect the corrosion defects, namely the thickness of the corroded layer, and it has a detection threshold under which no corrosion rate can be measured. Due to uncertainties, each inspection is affected by the probability of detecting small defects and the probability of wrong assessment in terms of defect existence and size. The present work aims at integrating imperfect inspection results in the cost model for corroded pipelines, where the failure probabilities are computed by reliability methods. A numerical application on a gas pipe shows the influence of corrosion rates and residual stresses on the optimal maintenance planning.     

RELIABILITY BASED OPTIMAL INSPECTION AND MAINTENANCE FOR PIPELINE UNDER CORROSION

Nondestructive inspection tools used for pipeline inspection are uncertain in detecting corrosion pits and in sizing detected defects. Probability-based optimal inspection schedule analysis must taken these uncertainties into account. In this paper, the probability of time to failure is formulated as integral equations with domain of integration expressed as unions and intersections of domains of failure, defect detection, defect nondetection and maintenance criterion. The rate of defect detection as a function of defect size and the maintenance criterion are used as filters to eliminate the defects that are not fit for service in an expected remaining service life after inspection. Simulation procedure is given to estimate the probability distribution of time to failure by using the integral equations. To facilitate the probabilistic analysis, a standard uniformly distributed variate is introduce and used in defining the domain of detected defect and the domain of nondetected defect. The advantages of using the proposed simulation procedure are discussed. Optimal inspection schedules are selected based on the minimum value of the maximum probability of time to failure before inspections and before the time at the end of service life. Effect of inspection quality and maintenance criterion on probability of time to failure and on selecting optimal inspection schedule is presented through an illustrative application study.     

埋地管道腐蚀检测与评价技术

介绍了土壤腐蚀环境的检测、管道防腐层检测技术、管体腐蚀损伤检测技术及杂散电流检测技术,探讨了管道剩余强度评价方法及管道剩余寿命预测方法。     

Allocation of effective maintenance limit for railway track geometry

Abstract

The objective of this study has been to develop an approach to the allocation of an effective maintenance limit for track geometry maintenance that leads to a minimisation of the total annual maintenance cost. A cost model was developed by considering the cost associated with inspection, preventive maintenance, normal corrective maintenance and emergency corrective maintenance. The standard deviation and extreme values of isolated defects of the longitudinal level were used as quality indicators for preventive and corrective maintenance activities. The Monte Carlo technique was used to simulate the track geometry behaviour under different maintenance limit scenarios and the effective limit was determined which minimises the total maintenance cost. The applicability of the model was tested in a case study on the Main Western Line in Sweden. Finally, a sensitivity analysis was carried out on the inspection intervals, the emergency corrective maintenance cost and the maintenance response time. The results show that there is an optimal region for selecting an effective limit. However, by considering the safety aspects in track geometry maintenance planning, it is suggested that the lower bound of the optimal region should be selected.     

Probabilistic characterisation of metal-loss corrosion growth on underground pipelines based on geometric Brownian motion process

This article describes a geometric Brownian motion process-based model to characterise the growth rate of the depth of corrosion defects on underground steel pipelines based on inspection data subjected to measurement uncertainties. To account for the uncertainties from different sources, the hierarchical Bayesian method is used to formulate the growth model, and the Markov Chain Monte Carlo simulation techniques are used to numerically evaluate the probabilistic characteristics of the model parameters. The growth model considers the bias and random scattering error associated with the in-line inspection (ILI) tool as well as the correlations between the random scattering errors associated with different ILI tools. The application of the growth model is illustrated through an example involving real ILI data collected from an in-service pipeline in Canada. The results indicate that the model in general can predict the growth of corrosion defects reasonably well. The proposed model can be used to facilitate the development and application of reliability-based pipeline corrosion management.     

Value of information-based decision analysis of the optimal next inspection type for deteriorating structural systems

Deteriorating infrastructure systems require inspections and maintenance to ensure safe operation. System operators are often required to decide the optimal type of inspection to perform, where some inspections are of higher accuracy, and correspondingly higher cost. Life cycle analysis is typically used to determine the optimal inspection type. While life cycle analysis is effective at determining the optimal inspection type, it is also inefficient, requiring analysis of the entire decision sequence throughout the system life cycle. This paper presents an efficient methodology to approximate the decision of the optimal next inspection type without performing a life cycle analysis. This methodology determines the range of the value of information provided by only the next inspection. When the inspection cost is outside the range of the value of information then this method yields the decision of which inspection type to choose, negating the need for life cycle analysis. When the inspection cost for some inspection types lies within the bounds then a subsequent life cycle analysis is required, but perhaps some inspection types can be eliminated, simplifying the life cycle analysis. Thus, this method is complimentary to life cycle analysis, functioning as a quick preliminary assessment. The methodology is demonstrated through a numerical example of a corroding pipeline.     

埋地钢质燃气管道腐蚀定期检测与维修实践

结合吉林市在役埋地钢管腐蚀定期检测与维修的实践,探讨了埋地钢管腐蚀定期检测的内容、流程、检测方法及仪器设备选择。结合检测结果分析了牺牲阳极阴极保护失效的原因,论述了对失效阴极保护管段采取补加牺牲阳极的对策。     

Inverse Gaussian process-based corrosion growth modeling and its application in the reliability analysis for energy pipelines

This paper describes an inverse Gaussian process-based model to characterize the growth of metal-loss corrosion defects on energy pipelines. The model parameters are evaluated using the Bayesian methodology by combining the inspection data obtained from multiple inspections with the prior distributions. The Markov Chain Monte Carlo (MCMC) simulation techniques are employed to numerically evaluate the posterior marginal distribution of each individual parameter. The measurement errors associated with the ILI tools are considered in the Bayesian inference. The application of the growth model is illustrated using an example involving real inspection data collected from an in-service pipeline in Alberta, Canada. The results indicate that the model in general can predict the growth of corrosion defects reasonably well. Parametric analyses associated with the growth model as well as reliability assessment of the pipeline based on the growth model are also included in the example. The proposed model can be used to facilitate the development and application of reliability-based pipeline corrosion management.