基于检查片检测的川气东送管道阴极保护有效性评价

发布时间：2018-07-03 02:00

本文选题：川气东送管道 + 阴极保护　；参考：《西南石油大学》2015年硕士论文

【摘要】：川气东送管道是继西气东输管道又一条贯穿我国东西部地区的天然气管道大动脉,其安全运营至关重要。管道运营2年后对防腐层进行检漏和修复时,发现防腐层破损处管道均已出现不同程度的腐蚀,阴极保护系统并未起到很好地保护作用。因此弄清楚川气东送管道的阴极保护状况,并对阴极保护效果进行检测与有效性评价非常重要。论文针对川气东送管道的阴极保护现状,通过建立阴极保护电位数学模型,选择了基于边界元的数值模拟软件Beasy CP开展检查片现场检测方案分析,同时利用极化曲线设计检查片,从而进行检查片现场试验,最后基于检查片检测数据和阴极保护准则来分析与评价川气东送管道阴极保护的有效性,并对阴极保护不合格管段提出针对性的整改措施。主要研究成果如下： (1)建立埋地管道阴极保护电位分布模型,通过对比常用数值解法,最终选择了基于边界元法的数值模拟软件Beasy CP开展研究,为检查片检测方案分析奠定了基础。 (2)根据建立的电位数学模型,考虑了川气东送管道阴极保护系统的具体参数,运用软件Beasy CP模拟检查片形状、检查片面积、检查片位置、管道防腐层破损率及土壤电阻率对管道与检查片电位的影响,分析了检查片现场检测方案,并提出了对检查片设计与现场试验时的建议。 (3)基于检查片的设计原理,总结了检查片检测的适用范围,确定了川气东送管道检查片的5个试验周期。测试了X70钢在不同pH值的土壤溶液中的极化曲线,根据钢质检查片消耗电流的大小值计算钢质检查片面积,进而确定了检查片的规格尺寸。同时对检查片进行IR降预测,从而验证了阴保检查片面积大小不会影响真实电位的测量,最终确定了川气东送管道检查片组的设计方案。 (4)根据检查片方案分析与设计进行检查片现场试验,制作检查片组,布置了沿线40个检查片试验的检测点,对检查片进行埋设、定期开挖、通断电电位测量、清洗、扫描电镜(SEM)及XPS能谱分析,形成了一套基于检查片的阴极保护检测实施规程。 (5)基于检查片检测数据对川气东送管道阴极保护进行有效性分析、评价与建议。 1)根据检查片检测数据分析了管道沿线39个检测点的土壤腐蚀性分布,通过腐蚀产物的宏、微观分析,从腐蚀产物的角度说明了阴极保护对管道腐蚀的抑制作用。 2)基于保护度评估了管道阴极保护效果,其合格率为44%。并将保护度与通断电电位相联系,得出了川气东送管道的平均IR降为220mV,即保护电位(Uon)准则应取-1070mV (CSE);而当真实电位(Uoff)达到-850mV (CSE)时,其对应的最小阴极保护度不会低于65%,提供了阴极保护日常管理维护的依据。 3)以阴极保护检查片的年腐蚀速率、通电电位和瞬时断电电位三大准则为判据,分析和评价了川气东送管道沿线39个检测点的阴极保护状况,其阴极保护合格率为74.4%,同时判断出了10处阴极保护失效管段。 4)用风险评价和危险矩阵方法,绘制了以环境腐蚀性对“不保护度”作的危险矩阵图,评估了各个检测管段的风险等级,结果表明,无试验管段位于最高风险区(V),且5、22、27和30号管段位于次高风险区(Ⅳ)。 5)分析影响川气东送管道阴极保护的因素,提出了对阴极保护不合格管段具有针对性的整改措施,并通过管道电位监测和现场开挖验证了检查片检测技术的可靠性。
[Abstract]:The East pipeline of Sichuan gas transmission is a large artery of natural gas pipeline which runs through the west east gas pipeline and runs through the eastern and western regions of China. Its safe operation is very important. When the pipeline is operated for 2 years, it is found that the corrosion layer has been corroded in different degrees, and the cathodic protection system has not been well protected. Therefore, it is very important to find out the cathodic protection status of the gas pipeline from east to west, and to detect and evaluate the effectiveness of cathodic protection.
In view of the current situation of cathodic protection in the pipeline for East Sichuan gas transmission, the paper selects the numerical simulation software Beasy CP based on the boundary element to carry out the analysis of the inspection scheme of the inspection film by setting up the mathematical model of the cathodic protection potential. At the same time, the check sheet is designed by using the polarization curve to carry out the field test of the check sheet. Finally, the inspection data is based on the inspection piece. The cathodic protection criterion is used to analyze and evaluate the effectiveness of the cathodic protection of the East Sichuan gas transmission pipeline, and to put forward the corrective measures for the unqualified cathodic protection tubes. The main research results are as follows:
(1) the distribution model of buried pipeline cathodic protection potential is established. By comparing the common numerical methods, the numerical simulation software Beasy CP based on boundary element method is selected to carry out the research, which lays the foundation for the analysis of inspection scheme.
(2) according to the established potential mathematical model, the specific parameters of the cathodic protection system of the Sichuan Gas East pipeline are considered, and the software Beasy CP is used to simulate the shape of the film, check the area of the sheet, check the position of the sheet, the damage rate of the pipe anticorrosion layer and the soil resistivity on the potential of the pipeline and check sheet, and analyze the on-site inspection scheme of the check sheet, and propose the method. Suggestions for the design of the check sheet and the field test are made.
(3) based on the design principle of the check sheet, the scope of application of check sheet detection is summarized, and the 5 test cycles of the Sichuan Gas East pipeline inspection piece are determined. The polarization curve of the X70 steel in the soil solution with different pH values is tested. The area of the steel check sheet is calculated according to the value of the consumption current of the steel inspection sheet, and the specifications of the check sheet are determined. At the same time, the IR drop prediction is also used to verify that the area size of the negative check sheet will not affect the measurement of the real potential. Finally, the design of the Sichuan Gas East pipeline inspection sheet group is determined.
(4) according to the analysis and design of the checkout program, the inspection film field test is carried out, the inspection sheet group is made, and the test points of the 40 check sheets are arranged along the line, the inspection film is buried, the electric potential measurement is regularly excavated, the cleaning, the scanning electron microscope (SEM) and the XPS spectrum are separated and analyzed, and a set of cathodic protection detection implementation rules based on the inspection sheet is formed. Cheng.
(5) based on the inspection data, the effectiveness analysis, evaluation and suggestions for cathodic protection of the gas pipeline from Sichuan to East are put forward.
1) according to the inspection data of the inspection piece, the soil corrosivity distribution of the 39 detection points along the pipeline was analyzed. Through the macro and micro analysis of the corrosion products, the inhibition effect of the cathodic protection on the corrosion of the pipeline was explained from the angle of corrosion products.
2) based on the protection degree, the cathodic protection effect of pipeline is evaluated. The qualified rate is 44%. and the protection degree is connected with the through electric potential. The average IR of the East Sichuan gas pipeline is reduced to 220mV, that is, the protection potential (Uon) criterion should be -1070mV (CSE), and when the real potential (Uoff) reaches -850mV (CSE), the corresponding minimum cathodic protection degree will not be low. At 65%, it provides the basis for daily management and maintenance of cathodic protection.
3) the cathodic protection of 39 detection points along the East Sichuan gas pipeline was analyzed and evaluated by the three criteria of the annual corrosion rate of the cathodic protection check sheet, the electric potential and the instantaneous electric potential, and the cathodic protection rate of the cathodic protection was 74.4%. At the same time, 10 cathodic protection failure tubes were judged.
4) using risk assessment and risk matrix method, we draw a hazard matrix map of environmental corrosivity to "non protection", and evaluate the risk grade of each detection section. The results show that the non test pipe segment is located at the highest risk area (V), and the 5,22,27 and No. 30 pipe segments are located in the sub high risk zone (IV).
5) analyze the factors that affect the cathodic protection of the East Sichuan gas pipeline, and put forward the corrective measures for the unqualified cathodic protection, and verify the reliability of the inspection technology through the pipeline potential monitoring and the site excavation.
【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】：TE88

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