基于IPSO-GEV优化的腐蚀油气管道剩余寿命预测

针对埋地管道腐蚀的随机性及极值类型选择不当而引起的拟合误差等问题,构建了基于IPSO(免疫粒子群优化算法)-GEV(广义极值分布)优化的油气管道最大腐蚀深度预测模型。首先,采用GEV分布拟合极值数据,利用1PSO优化GEV分布函数的参数并确定极值分布类型,以此确定整条管道的最大腐蚀深度;然后,建立基于可靠性理论的腐蚀裕量模型,来预测管道的剩余寿命;最后,以国内两条腐蚀管道为例验证模型的预测精度。实例结果表明:经IPSO-GEV优化的管道最大腐蚀深度预测模型不受限于数据的具体分布,且预测模型的预测精度较高,管道的剩余寿命预测合理。     

“聊城-濮阳”成品油管道剩余寿命预测

腐蚀是导致油气管道失效的重要因素,定期对管道进行检测和评价可有效保证其安全运行。基于改进的ASME B31G剩余强度评价方程和有限元分析方法分别建立了管道剩余寿命预测模型,以"聊城-濮阳"成品油管道5处腐蚀较为严重的缺陷为研究对象,采用土壤埋片法测出平均腐蚀速率后,应用2种预测模型分别对这5处腐蚀缺陷进行了剩余寿命预测。结果表明:改进ASME B31G评价方程预测结果较有限元分析方法更为保守;无论采用哪种模型预测剩余寿命,具有缺陷的管道须在未来5~10年内进行维修;管道再检测评价周期不应超过5年。     

含外腐蚀缺陷管道剩余强度及剩余寿命的分析

埋地石油管道经常受到水分、土壤等外部腐蚀,外壁会出现形状不同的腐蚀缺陷,腐蚀处会产生应力集中现象,削弱管道的承压能力。因此,必须对管道剩余强度及剩余寿命进行评价。采用ANSYS-Workbench软件对含外腐蚀缺陷管道进行建模仿真,分析管道在不同腐蚀缺陷参数下的等效应力,利用Excel得出腐蚀参数与等效应力的关系曲线图,并对管道的运行可靠性进行了预测。结果表明:单独的矩形或椭圆腐蚀缺陷对管道的影响小于矩形和椭圆形组成的双腐蚀;等效应力随腐蚀区域长度的增加呈上升趋势,随缺陷宽度的增大趋于下降;腐蚀区域固定时,等效应力随腐蚀深度增加而增加。ANSYS-Workbench有限元法对于分析管道剩余强度和剩余寿命是可行的,对管道的设计和防护具有重要的参考价值。     

基于GA-LSSVM模型的管道腐蚀速率预测研究

腐蚀速率是反映管道腐蚀动力学过程的重要特征参数,为实现对管道长期运行可靠性和剩余寿命的精准评估,对腐蚀速率的预测显得尤为重要.最小二乘支持向量机(LSSVM)是一种基于机器学习的方法,常用于分类和预测研究,惩罚参数γ与核参数σ2是LSSVM的2个重要参数,在进行计算时只能经验取值,对计算结果影响较大.通过利用遗传算法(...     

管道综合状况的检测与寿命评估技术

针对航空输油管道的安全运行与寿命,分析了影响管道安全运行的四大因素,给出了钢质管道生命期模型及管腐蚀趋势预测和管道剩余寿命模型,在此基础上对机场管道进行检测并提出了维护管理建议。     

在役腐蚀管道动态非概率可靠性分析简

 腐蚀失效是压力管道失效的主要形式之一,研究腐蚀管道的可靠性具有重要理论意义和应用价值.在对腐蚀管道可靠性分析时,概率可靠性模型和模糊可靠性模型对于数据信息的要求较高.而在掌握不确定性信息很少情况下,为了充分利用管道的不确定性信息弥补原始数据的不足,可将腐蚀管道可靠性分析中的材料屈服强度、管道直径、缺陷深度和操作压力等不确定参数视为区间变量,基于区间模型建立一种在役腐蚀管道动态非概率可靠性模型,给出了腐蚀管道剩余寿命预测的简便方法.结合工程实例计算与分析,表明了文中所提出方法的可行性和合理性,并在此基础上,分析了管道的壁厚、缺陷深度、实际压力和腐蚀速率这些区间变量的不同变异系数对非概率可靠性指标的影响,分析结果表明非概率可靠性指标对管道壁厚的变异系数最为敏感.     

西气东输管道安全评价

西气东输管道安全评价是西气东输工程劳动安全卫生预评价的重要内容.基于FAD技术,并引入可靠性理论,计算了管道的可靠度,分析了第三方损伤、地质灾害等外部因素对管道可靠度的影响.结果表明,即使管道存在一定概率的漏检缺陷,管道本身的可靠度可以满足要求,影响管道可靠度的主要因素是第三方损伤和地质灾害.评估了西气东输管线疲劳可靠性寿命和腐蚀可靠性寿命.结果表明,管道设计寿命30年内不会发生疲劳破坏;若管道防腐层存在制造缺陷或现场施工损伤缺陷,多数地段土壤腐蚀寿命低于30年设计寿命.根据评价结果,给管道设计和管道的维护提出了建议.     

海底输油管道在悬空与腐蚀联合作用下的剩余寿命预测

为解决海底输油气管道在悬空与腐蚀联合作用下的剩余寿命预测问题,提出一种海底输油管道的强度计算与寿命预测方法。通过悬空管道受力分析求得管壁各项应力,采用应力集中系数法分析腐蚀缺陷对悬空管道强度的影响,根据模拟腐蚀试验得出的管道缺陷发展规律建立管道剩余寿命预测模型,从而解决输油气管道的剩余寿命预测问题。实验结果表明:悬空与腐蚀联合作用对管道强度的影响最强,悬空缺陷次之,腐蚀缺陷最弱;随着服役年限的增长,悬空与腐蚀缺陷尺寸逐步变大,管道强度降低,最终到达一定年限时管道失效。     

X56海底管道在腐蚀环境下疲劳裂纹扩展过程预测

海底管道浸没在海洋环境中,腐蚀疲劳破坏十分常见,因此为这些管道的剩余疲劳寿命提供一种准确的预测方法至关重要。本工作研究了海浪循环荷载下含裂纹管道的疲劳裂纹扩展行为,提出了一种新的管道寿命预测方法。使用新提出的形状因子处理试验数据获得X56钢的Paris常数,并分析了其在腐蚀环境下的疲劳性能。运用有限元软件模拟管道疲劳裂纹的扩展过程并计算其应力强度因子(Δ~K),随后基于Paris公式对管道的剩余寿命进行预测。结果表明,对于给定的Δ~K,海水中管道的疲劳裂纹扩展速率(da/d N)为空气中的1. 6倍,且随着疲劳裂纹扩展速率的增加,海水对管道腐蚀疲劳的影响逐渐降低。运用新提出的方法预测管道剩余寿命并与足尺寸X56管道疲劳试验结果进行对比,结果表明该方法能够有效地预测管道的疲劳裂纹扩展状态和剩余疲劳寿命。     

辽河油田埋地集输管道剩余寿命的预测

以辽河油田曙四联至首站集输管道为研究对象,通过计算机求解得到管道腐蚀缺陷的极限尺寸;基于室内挂片试验方法,计算管道的腐蚀速率。基于RSTRENG准则的管道剩余强度预测模型,对输油管道进行剩余寿命预测。结果显示:在管道的最大腐蚀深度为6.71 mm,均匀腐蚀速率为0.229 mm/a条件下,管道的剩余使用寿命为9 a,考虑到点蚀与局部腐蚀更为严重及预测中不确定因素的疏漏,建议下一次腐蚀评价应为4 a后。     

埋地长输管道交流腐蚀现场状态及其风险评估

超高压输电线路对埋地管道的交流干扰问题日益突出,国内对其交流腐蚀缺乏风险评估.以裸露X65钢模拟埋地长输管道防腐蚀涂层缺陷,采用交、直流电流及电位的在线监测和腐蚀失重等方法,研究了高压输电线路交流干扰特征及其对管道阴极保护系统的影响规律.结果表明,当土壤介质条件基本不变时,电位与电流的变化存在相似性;适当调节阴极保护电...     

穿越非均匀土体埋地管道地震离心实验研究

穿越非均匀土体经历不同地震作用的埋地管线的变形和残余强度严重影响着管道的安全。该文采用离心振动台分别平行于埋地管道长度方向输入0.6 g和0.3 g峰值地面加速度地震波,研究了埋地管道在一系列地震作用和不均匀土体变形共同作用下的响应,得到了PVC和铝合金两种埋地管道穿越软土/硬土土体的地震响应规律。地震引起不均匀土体的瞬时变形,导致埋地管道最大应变发生在土体分界面和软土中,管道拉伸应变幅值软土要大于硬土,而压缩应变幅值正好相反,硬土中管道拉伸应变幅值小于压缩应变幅值,硬土中管道压缩应变幅值受地震烈度影响比软土大。地震引起的土体永久变形对埋地管道残余变形影响很大,硬土中的管道残余应变为压应变,软土中管道的残余应变为拉压应变交替分布。     

Strong exploration of a cast iron pipe failure model

A physical probabilistic failure model for buried cast iron pipes is described, which is based on the fracture mechanics of the pipe failure process. Such a model is useful in the asset management of buried pipelines. The model is then applied within a Monte-Carlo simulation framework after adding stochasticity to input variables. Historical failure rates are calculated based on a database of 81,595 pipes and their recorded failures, and model parameters are chosen to provide the best fit between historical and predicted failure rates. This provides an estimated corrosion rate distribution, which agrees well with experimental results. The first model design was chosen in a deliberate simplistic fashion in order to allow for further strong exploration of model assumptions. Therefore, first runs of the initial model resulted in a poor quantitative and qualitative fit in regards to failure rates. However, by exploring natural additional assumptions such as relating to stochastic loads, a number of assumptions were chosen which improved the model to a stage where an acceptable fit was achieved. The model bridges the gap between micro- and macro-level, and this is the novelty in the approach. In this model, data can be used both from the macro-level in terms of failure rates, as well as from the micro-level such as in terms of corrosion rates.     

Influence of soil structures on corrosion performance of floating-DC transit systems

The production of stray currents by DC-transit systems leads to the corrosion of nearby buried metallic structures, such as pipelines and cable sheaths. The paper details the corrosion performance of a DC transit system with a floating return rail, for a number of different soil-resistivity structures: uniform, horizontal and vertical-layer models. This builds on previous work carried out in homogenous soils. It is shown that a variation in soil type along the route of a transit system can lead to high local leakage-current densities on buried metallic structures, increasing their vulnerability to corrosion damage.     

Assessment of Microbially Influenced Corrosion Risk in Slovak Pipeline Transmission Network

Microbial activities are particularly serious in buried natural gas pipelines resulting in high corrosion costs. It is a mater of necessity to deal with this factor during the evaluation of corrosion risk. The objective of this investigation was to determine to what extent the main factors of environment are responsible for biocorrosion behavior in particular transmission pipeline sections running through Slovakia and subsequently evaluate the biocorrosion risk in the studied areas. According to the point method the probability and outcome value of three chosen factors, such as soil characteristics, water presence, and location were determined for each excavation. Two from the monitored excavations in the east of Slovakia and three situated in the south of Slovakia were found to be the most hazardous sites in terms of biocorrosion risk.     

Stresses and deformations in a buried oil pipeline subject to differential frost heave in permafrost regions

Differential frost heave of the buried oil pipelines in permafrost regions can have an adverse effect on the mechanical status of the pipeline, and seriously endanger the pipeline security. In order to reduce the damage to the pipeline during its designed lifetime, it is necessary to analyze the mechanical behavior of oil pipelines taking into consideration the differential frost heave in the design of the pipelines in permafrost regions. In this paper, an elastico-plastic finite element model for the mechanical behaviors of the pipeline–soil system was established. In order to simplify computations, the effects of the temperature and moisture fields on the problem were considered by applying the computed temperature zones of soils surrounding the pipeline from the thermal analysis, and actual frost heaving ratio of the soils was applied to the mechanical model to calculate the stresses and deformations of the pipeline in permafrost regions. These analyses may provide some useful insights into the possible mechanical states of the pipeline–soil system for the design, construction and operation of the buried oil pipelines in permafrost regions.     

Life prediction based on analysis of crack coalescence in low cycle fatigue

The crack coalescence in some materials is known to make influence on the failure life significantly in low cycle fatigue as well as corrosion fatigue. A model was proposed to simulate crack linking during fatigue process. The crack distribution observed experimentally was idealized by a two-dimensional model with straight cracks. Some assumptions were made for the coalescence criterion in the model. A procedure for estimating residual life was developed based on the proposed model. The procedure was applied to fatigue process of a copper, in which the growth due to crack linkings was observed to be dominant through fatigue life. A good agreement was shown between the experimental and the predicted results. The statistical properties of life distribution were also discussed based on a Monte Carlo simulation.     

埋地输油管道对爆破振动的动力响应

为了控制爆破振动对油气管道的影响,利用ANSYS/LS-DYNA软件对埋地管道在爆破作用下不同方向的受力过程进行数值模拟,建立埋地管道三维有限元模型,采用多物质流固耦合算法模拟爆破过程。结果表明:基于流固耦合方法模拟得到的振速与现场实测结果基本一致,利用该模拟方法研究爆破振动对埋地输油管道的影响是可行的。经过爆破模拟分析,得到埋地管道上的有效应力变化规律。迎爆面和背爆面受到的应力远高于管顶、管底受到的应力,且迎爆面的有效应力大于背爆面,说明迎爆面是最容易发生变形的;管顶和管底位于管道的中轴面上,受到的应力较小,变形也较小。     

埋地钢管局部悬空的挠度和内力分析

在地质灾害作用下,埋地钢管下方的土壤下陷或流失会造成管道悬空,这给管道长期的安全运行构成了严重的威胁。对于埋地钢管在悬空时的失效问题曾有文献进行过研究,但均未推导出此种状态下埋地钢管的挠度和内力计算公式。该文基于Winkler假设的弹性地基梁理论,建立了埋地钢管在局部悬空时管道与土相互作用的力学模型。利用埋地钢管悬空段与非悬空段之间的变形协调性,通过求解管轴挠曲线微分方程,得出了埋地钢管在局部悬空时的挠度和内力计算公式。通过算例与有限元方法的结果进行了比较,结果表明:该方法在精度方面可满足工程要求。