Prediction on Failure Pressure of Pipeline Containing Corrosion Defects Based on ISSA-BPNNModel

Oil and gas pipelines are affected by many factors,such as pipe wall thinning and pipeline rupture.Accurate prediction of failure pressure of oil and gas pipelines can provide technical support for pipeline safety management.Aiming at the shortcomings of the BP Neural Network(BPNN)model,such as low learning efficiency,sensitivity to initial weights,and easy falling into a local optimal state,an Improved Sparrow Search Algorithm(ISSA)is adopted to optimize the initial weights and thresholds of BPNN,and an ISSA-BPNN failure pressure prediction model for corroded pipelines is established.Taking 61 sets of pipelines blasting test data as an example,the prediction model was built and predicted by MATLAB software,and compared with the BPNN model,GA-BPNN model,and SSA-BPNN model.The results show that the MAPE of the ISSA-BPNN model is 3.4177%,and the R2 is 0.9880,both of which are superior to its comparison model.Using the ISSA-BPNN model has high prediction accuracy and stability,and can provide support for pipeline inspection and maintenance.

Ultimate Load Capacity of Offshore Pipeline with Arbitrary Shape Corrosion Defects

A set of generalized solutions are proposed for estimating ultimate load capacity of pipeline with arbitrary corrosion shapes subjected to combined internal pressure, axial force and bending moment. Isotropic and anisotropic material characteristics in longitudinal and circumferential direction of pipeline are also considered in the proposed equations. Simplified numerical method is used to solve the generalized expressions. The comparisons of numerical results based generalized solutions and full-scale experimental results are carried out. The predicted results agree reasonably well with the experiment results. Meanwhile, the effects of corrosion shapes and locations on the ultimate load capacity are studied.

Study on Interaction Relationship for Submarine Pipeline with Axial Corrosion Defects

Corrosion is one of the main reasons to cause the operation accident of submarine oil and gas transmission pipelines. As the major corrosion pattern in submarine pipelines, the effects of corrosion clusters consisting of the adjacent corrosion defects on failure pressure are investigated through non-linear large-deformation finite element method. Typically, the failure behavior and limit strength of submarine pipeline with axial groove- groove corrosion defect pair exposed to interhal pressure are analyzed. The effects of corrosion depth and axial spacing between a pair of corrosion defects on failure pressure are concluded. An interaction relationship for corrosion defects in pipelines, as well as prediction formulations for assessing the remaining strength of corroded pipelines are proposed. The expressions based on the proposed interaction relationship give more accurate results than the methods used in the existing design guidelines.

Modeling of the mechano-electrochemical effect at corrosion defect with varied inclinations on oil/gas pipelines

A 3-dimensional finite element model was built to determine the effect of inclination angle of a corro sion defect on local mechano-electrochemical(M-E)effect in a simulated soil solution.Because of the high effect of the defect inclination angle on the M-E effect,when the inclination angle is 0°(i.e.,the primary axis of the defect parallel to the longitudinal direction of the pipe),the greate st stress concentration level at the defect can be observed,which is associated with the lowest corrosion potential,the greatest anodic current density and the most serious accelerated localized corrosion.When the inclination angle is 90°,the stress concentration level reduces and the corrosion potential becomes less negative,accompanying with the decreased anodic/cathodic current densities.Besides,when the ratio(r_(ca))of the primary axial length of the defect to its secondary axial length is 1,the defect inclination does not affect the stress and the electrochemical corrosion rate at the defect.With the increase of r_(ca),the effect of the defect inclination angle is more apparent.

Inspection of pipeline girth welds with ultrasonic phased array technique

A novel automatic ultrasonic system used for the inspection of pipeline girth welds is developed, in which a linear phased array transducer using electronic scan is adopted. Optimal array parameters are determined based on a mathematical model of acoustic field for linear phased army derived from Huygens＇ principle. The testing method and the system structure are introduced. The experimental results show that the phased array transducer system has the same detectability as that of conventional ultrasonic transducer system, but the system architecture can be simplified greatly, and the testing flexibility and the testing speed can be improved greatly.

An Analysis on Limit Load for Corroded Submarine Pipelines

By means of elastic-plastic finite element analysis, a systematic nonlinear analysis of material and geometry has been carried out for submarine pipelines. A criterion for deriving limit load is studied. Based on this criterion, the limit load for corroded submarine pipelines is calculated. The corrosion length, corrosion depth and corrosion width affect the limit load. A solution to limit load is proposed and proved valid through comparison of the solution with burst test results and ASME B31G solutions.

考虑弯矩影响的含腐蚀缺陷X80管道失效内压的计算方法

通过非线性有限元方法研究了弯矩影响下含腐蚀缺陷X80管道失效内压与腐蚀缺陷深度、长度、宽度等参数的相关性,并给出相应的失效内压预测方法。结果表明:弯矩,腐蚀缺陷尺寸(深度、长度和宽度)等均会对含腐蚀缺陷高钢级管道的失效内压产生影响,给出的弯矩影响下含腐蚀缺陷高钢级管道的失效内压预测方法可以准确预测管道的失效内压,对实际工程具有指导意义。

基于同伦分析方法和神经网络的复杂腐蚀缺陷海底管道屈曲压力计算方法

针对含复杂形状腐蚀缺陷海底管道屈曲压力计算难的问题,本研究中采用同伦分析方法对含复杂腐蚀缺陷海底管道的屈曲压力进行了计算,并用有限元方法进行了对比验证,进而根据计算结果提出了基于神经网络模型的海底管道屈曲压力的计算方法。结果显示:同伦分析方法可以有效、准确地计算含复杂腐蚀缺陷海底管道的屈曲压力,在相同情况下抛物线形腐蚀管道的临界屈曲压力大于椭圆形管道的临界屈曲压力。基于神经网络模型的腐蚀海底管道屈曲压力计算方法具有良好的泛化性能,可以很好地应用于工程现场的计算。

油气田钢质管道内检测结果评价方法及分析

介绍一种依据ASME B31G和DNV RP-F101管道腐蚀缺陷标准的油气田钢质管道内检测结果评价方法,并以某均匀腐蚀管线钢管为例,运用该方法对其内检测结果进行评价。该方法可逻辑判断缺陷类型及量化方法,计算管道失效压力及腐蚀速率预测。该方法具有计算结果准确、易操作、应用前景广等优点。

智慧系统在液体散货码头装卸工艺中的应用

结合智慧港口应用热点和当前行业发展现状,以某液体散货码头为例,针对码头装卸工艺中智慧系统的应用,从智能装卸臂、在线腐蚀监测、在线自动取样、管道无人巡检等系统进行多角度的分析,提出可在当前液体散货码头装卸工艺中落实的智慧系统模块的应用方案。该方案可减少现场工人的工作量,通过数据赋能提升码头运营、管理等作业效率,提高港口管理的信息化、精准化,并可为类似工程提供参考。

条形缺陷对L360管线钢环焊缝硫化物应力腐蚀开裂敏感性的影响

通过抗硫化物应力腐蚀试验、慢应变速率拉伸试验、氢含量测试等方法研究条形缺陷对H_(2)S环境下L360管线钢环焊缝硫化物应力腐蚀开裂敏感性的影响。结果表明,环焊缝在72%、85%和110%SMYS(最小屈服强度)应力水平下,热影响区出现裂纹且裂纹长度随加载应力增大而增大;条形缺陷环焊缝试样在屈服点后快速发生断裂,其断裂应变(0.024)仅为非缺陷环焊缝试样的21.05%;条形缺陷存在促进氢离子在裂纹尖端聚集从而加剧发生开裂倾向,消氢处理技术可以有效降低氢含量,降低环焊缝抗硫化物应力腐蚀开裂敏感性降低。

轴向应变作用下含腐蚀缺陷X80管道氢渗透的有限元分析

目的研究在役天然气管道掺氢输送条件下氢原子在管道腐蚀缺陷处的扩散和分布情况及应变对腐蚀缺陷处氢扩散行为的影响。方法利用COMSOL软件,将固体力学模型和扩散模型相结合,建立了基于有限元的氢原子扩散渗透模型,研究了在纵向拉伸应变作用下X80钢制管道不同尺寸腐蚀缺陷处氢原子的分布情况。结果在没有拉伸应变的情况下,氢原子一旦进入管道内,在浓度梯度的驱动下,沿径向梯度扩散到管道内。当在管道上施加应变时,氢原子的扩散受到静水应力的驱动。氢原子在腐蚀缺陷处的最大浓度超过了进入管道的氢原子初始浓度。结论氢原子在腐蚀缺陷处聚集。此外,施加的拉伸应变也影响氢原子聚集的位置,随着缺陷长度的减小和深度的增大,在内壁腐蚀缺陷处,更多的氢原子会集中在缺陷中心和尖端。

掺氢环境下含腐蚀缺陷X52天然气管道的结构强度失效机理研究

[目的]旨在探究掺氢环境下含腐蚀缺陷管道的结构强度劣化规律。[方法]基于试验数据分析X52钢在不同掺氢比例下的承载性能,采用非线性有限元方法研究X52掺氢天然气管道在不同腐蚀缺陷下的结构强度失效机理。[结果]研究结果表明:掺氢比例增大到50.0%时,管道在组合载荷下达到失效的位移最小为2.58 mm,结构韧性劣化程度较大;掺氢比例为25.0%时,缺陷深度越大,结构失效程度越严重,通过对正方形和圆形缺陷的对比,发现正方形缺陷的最大应力高于圆形缺陷。[结论]基于材料性能构建的含缺陷管道模型能够实现对不同掺氢环境下天然气管道服役状态结构承载力劣化程度的评估,所做研究可为新能源管道设计及健康监测提供工程化建议。

基于蒙特卡洛方法的油田管道内腐蚀状态安全评价及预测

随着管道长时间运行,油气管道内壁会出现不同程度的腐蚀、凹点、裂纹、结垢及磨蚀等缺陷,需要及时维修或者更换。针对油田管道内壁腐蚀特点,提出了一种新的基于蒙特卡洛方法的管道安全评估模型。首先用管道内检测仪器对目标管道进行内检测,获取相关缺陷的具体数据,然后在分析数据的基础上预测腐蚀缺陷生长规律,最后基于安全预警模型对管道内腐蚀进行安全评价,预判管道失效年限。

管道内检测腐蚀数据概率分布规律研究及应用

腐蚀伴随着管道整个生命周期,管道腐蚀速率评估是管道剩余寿命评估的重要部分,为了提高管道剩余寿命评价的准确性,为制定合理的检测维修周期提供支撑,以某条管道连续两轮漏磁内检测腐蚀数据为基础,并采用最大似然估计法将腐蚀速率与几种常见的概率分布模型进行拟合,通过K-S检验和p-p散点图方法的比较分析,深入研究了该管道径向和轴向腐蚀速率的概率分布规律,发现该管道径向和轴向腐蚀速率的最优分布规律为广义极值分布规律。在此基础上建立了基于概率分布规律的管道剩余寿命评估模型,选取该概率分布模型95%分位数的腐蚀速率作为管道剩余寿命的评估腐蚀速率。分析采用局部腐蚀速率评价方法、最大腐蚀速率评价方法、概率分布腐蚀速率评价方法时5年内需要维修点的数量,结果表明:采用概率分布腐蚀速率评价方法需维修点数量介于局部腐蚀速率评价法和最大腐蚀速率评价法之间,可在一定程度上避免过度维修和维修不及时。

含双腐蚀缺陷高钢级油气管道剩余强度研究

为了加强含双腐蚀缺陷高钢级管道的安全评价,基于塑性失效准则,利用Workbench有限元分析软件对缺陷处的等效应力和剩余强度进行了模拟,考察了缺陷长度、缺陷深度和缺陷间距等参数对剩余强度的影响,利用99%相互作用准则确定极限作用距离,形成双腐蚀缺陷剩余强度评价方法,并进行数据验证。结果表明,随着内压的增加,管道先后经历弹性阶段、屈服阶段和强化阶段;在缺陷深度较深时,轴向间距对缺陷轴向分布时的最大等效应力影响较大,不同环向间距下的最大等效应力几乎不发生变化。当相邻腐蚀轴向间距系数n小于2.5、相邻腐蚀环向间距系数c小于1.26时,需考虑缺陷间的相互作用和影响;修正后公式可用于计算含双点腐蚀缺陷的高等级钢剩余强度,结果较DNV-RP-F101规范更接近有限元分析结果,最大相对误差不超过1.74%。研究结果可为提高管道完整性管理水平提供理论依据和实际参考。

苯酚管道数字射线在线检测试验研究

针对化工装置的苯酚管道在线检测的需求,通过制作含埋藏缺陷的不同管径的试样,选择合适的透照工艺参数,在有无介质的两种工况下,分别开展数字射线检测试验,研究缺陷的检出情况。通过对比研究检测结果发现后,管径DN 250 mm及以下含介质管道,气孔、未焊透等体积型可以有效检出,裂纹等面积型缺陷一定条件下可以检出,说明苯酚管道数字射线在线检测具有可行性。

基于内外检测数据对齐的管道腐蚀原因分析

长庆油田某原油管道经漏磁内检测后对典型的外部腐蚀进行开挖,发现保温管下大面积腐蚀。基于管道内外检测数据对比,阴极保护、土壤电阻率及交/直流杂散电流干扰检测,结合直接开挖结果,研究原油管道腐蚀原因。研究结果表明:基于外检测时,对阴极保护、土壤电阻率及交/直流杂散电流干扰进行检测,当无交/直流干扰,管道本体无腐蚀产生;基于内检测后,检测信号显示部分管道存在大量外部腐蚀缺陷,选取一处典型大面积腐蚀缺陷进行直接开挖,对该处缺陷进行交/直流干扰检测,检测无干扰,发现保温层出现渗水,保温层下管道本体出现浮锈,环氧煤沥青出现老化并与管道本体发生剥离,腐蚀产物和保温层发泡材料出现粘结。内外检测数据对齐能研究管道外部环境对管道本体安全和腐蚀的影响,可进一步完善管道完整性评价体系。

一种发射率可矫正的红外热成像全局检测方法

在无损检测领域中,红外热成像检测具有重要地位。在利用红外热成像技术检测缺陷的过程中,受加工工艺和周围环境的影响,待检测设备的表面粗糙度各有殊异,材料表面的发射率不均,导致温度采集误差较大。针对该问题,结合热辐射基本定律探究出一种发射率可矫正的红外热成像全局检测法,意在矫正材料的表面发射率,降低检测过程中可能出现的缺陷错检漏检等安全性问题的风险。其仿真和实验结果表明,一方面使用红外热成像法检测时,表面粗糙度不同会严重干扰检测的准确性,具体影响为粗糙度越大,检测出的辐射温度越高;另一方面使用分离温度法可以实现矫正物体表面由于粗糙度不同带来的发射率不同的影响,仿真和实验结果表明矫正准确度可达70%左右,最高可以达到75%以上。基于此矫正检测方法能够有效实现基于红外热成像技术的全局检测,减少发射率对红外热像仪检测精度的影响,提高检测精度,同时也可以极大程度上提高缺陷检测的效率。

含腐蚀缺陷管道弱磁信号的正演模型

针对埋地集输管道在非开挖条件下的腐蚀检测难题,结合磁偶极子模型以及应力磁化强度模型,建立一种含缺陷管道弱磁信号正演模型。通过数值模拟方法研究了腐蚀缺陷磁感应强度波形特征及离地高度、磁化强度对磁感应强度的影响。结果表明:腐蚀缺陷处Bx和By出现极值特征且方向相反,Bz出现过零点特征且峰值改变方向;分别讨论了离地高度以及磁化强度对信号的影响。通过开展现场检测,验证正演模型的准确率,其误差率为11.11%。