西二线天然气管道内腐蚀状况及剩余强度评估

发布时间：2018-02-11 09:08

本文关键词： 西二线 X80钢内腐蚀电化学剩余强度　出处：《西南石油大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着长输天然气管道服役时间增加,管道内腐蚀问题日益凸显。管道内腐蚀达到一定程度,将会引起管道产生裂缝或穿孔,造成天然气的泄露,严重的甚至发生爆炸,对人身和财产安全带来严重隐患。西气东输二线(以下称西二线)输送的天然气主要来自土库曼斯坦和哈萨克斯坦两个气源。上述两气源均是经脱硫后满足西二线输送标准的天然气,虽然只含有微量的H2S(小于20mg/m3),但存在的硫组分仍会使管道内腐蚀影响因素更加复杂,内腐蚀程度更加严重,且内腐蚀穿孔后的后果也更加严重,故需要对西二线的内腐蚀状况进行评估,进而研究西二线的剩余强度,以保证西二线的安全高效运营。本文针对西二线的内腐蚀状况及剩余强度评估进行了以下几个方面的研究： (1)采用室内实验的方法,对收集的西二线12组清管产物进行了总硫含量和Cl-和S042-测试,对39组沿线气体样品进行了H2S含量测试。结合调研的西二线沿线高程,气质组分、管材等整体概况,确定了发生内腐蚀的关键管段为霍尔果斯至精河压气站管段以及精河至乌苏压气站管段。 (2)对西二线管材X80管线钢进行了电化学腐蚀实验,根据电化学原理,通过对电化学过程中的极化曲线和电化学阻抗进行拟合分析,得到相应的腐蚀电流密度和极化电阻。研究了X80钢在西二线清管产物模拟溶液(Cl-和SO42-)中的电化学腐蚀行为。 (3)利用高压釜,对X80管线钢在模拟西二线天然气及管液组成、运行压力、温度范围条件下进行了实验,测定了西二线X80钢的腐蚀速率。采用SEM和EDS对X80管线钢腐蚀产物进行了分析,研究了西二线X80钢的腐蚀机理。 (4)基于霍尔果斯至精河压气站、精河至乌苏压气站两条管段的内检测报告数据,对管道的内腐蚀缺陷的数量、类型、深度、相邻缺陷轴向间距进行了统计和分析,确定了三种代表性的内腐蚀缺陷形式。分别针对三种缺陷类型,统计了腐蚀缺陷的尺寸、面积,得到相应的分布规律,初步完成了对西二线关键管段内腐蚀缺陷的整体评估,对进一步进行西二线管道剩余强度的研究提供依据。 (5)基于西二线内腐蚀缺陷统计分析,将三种缺陷类型：轴向凹槽、轴向凹沟、坑状金属损失合理简化为三种物理模型：平底方形、同底方形、球形坑蚀,采用ANSYS有限元、B31G准则、DNV-PR-F101准则三种方法进行剩余强度的评估,并进行结果对比分析,提出针对不同管材、内腐蚀缺陷类型的管道安全评估时两种准则的选择依据。 (6)依据计算所得的西二线管道剩余强度、临界失效腐蚀深度和腐蚀速率,分析预测西二线管道的使用年限,并结合西二线工况运行条件等情况,提出延长管道使用年限的措施。本论文对高钢级天然气长输管道的内腐蚀状况及剩余强度评估方面有一定的意义。
[Abstract]:With the increase of service time of long distance natural gas pipeline, the corrosion problem in pipeline becomes more and more serious. If the corrosion in pipeline reaches a certain degree, it will cause crack or perforation of pipeline, cause natural gas leakage, and even explode seriously. Serious danger to personal and property safety. Natural gas from Turkmenistan and Kazakhstan mainly comes from Turkmenistan and Kazakhstan. These two gas sources are both desulphurized and satisfied with the west second gas source after desulphurization of the second line of natural gas transmission from the west to the east (hereinafter referred to as the second line of the west second line). Line conveys standard natural gas, Although it contains only a small amount of H _ 2s (less than 20 mg / m ~ (-3)), the presence of sulfur components will make the corrosion factors in the pipeline more complex, the degree of internal corrosion more serious, and the consequences of internal corrosion perforation more serious. Therefore, it is necessary to evaluate the internal corrosion of the second west line and study the residual strength of the second line. In order to ensure the safe and efficient operation of the West second Line, this paper studies the internal corrosion status and residual strength evaluation of the West second Line in the following aspects:. 1) the contents of total sulfur, Cl- and S042- were measured in 12 groups of pipe-clearing products collected from West second Line by laboratory experiment, and the content of H _ 2S in 39 groups of gas samples along the route were tested. According to the general situation of pipe material, the key section of internal corrosion is determined to be the section of Halgos to Jinghe gas pressure station and the section of Jinghe to Wusu gas pressure station. The electrochemical corrosion experiment of X80 pipeline steel was carried out. According to the principle of electrochemistry, the polarization curve and electrochemical impedance of X80 pipeline steel in the electrochemical process were fitted and analyzed. The corrosion current density and polarization resistance of X80 steel were obtained. The electrochemical corrosion behavior of X80 steel in simulated solutions of Cl- and SO42-was studied. Using autoclave, the X80 pipeline steel was tested under the conditions of simulating the composition of natural gas and pipe liquid, operating pressure and temperature range of the second line. The corrosion rate of X80 steel was measured, the corrosion products of X80 pipeline steel were analyzed by SEM and EDS, and the corrosion mechanism of X80 steel was studied. Based on the data of internal inspection report of the two pipe sections from Horgos to Jinghe Gas Station and from Jinghe to Wusu Gas Station, the quantity, type, depth and axial distance of adjacent defects of pipeline are analyzed and analyzed. Three representative forms of internal corrosion defects are determined. The size and area of corrosion defects are counted for the three types of defects, and the corresponding distribution laws are obtained, and the overall evaluation of corrosion defects in key sections of the West second Route is preliminarily completed. It provides the basis for further research on the residual strength of the west second line pipeline. Based on the statistical analysis of internal corrosion defects in the West second Line, three types of defects, namely, axial grooves, axial grooves, crater metal losses, are reasonably simplified into three physical models: square with flat bottom, square with same bottom, and spherical pit. The residual strength is evaluated by using the ANSYS finite element B31G criterion and DNV-PR-F101 criterion, and the results are compared and analyzed. The selection basis of the two criteria for the safety assessment of pipelines with different pipe and internal corrosion defects is put forward. Based on the calculated residual strength, critical failure corrosion depth and corrosion rate of the pipeline, the service life of the pipeline is analyzed and forecasted, and the measures for prolonging the service life of the pipeline are put forward in combination with the operating conditions of the second line. This paper has some significance for internal corrosion and residual strength evaluation of high grade gas pipeline.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE988.2

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