本文選題：川氣東送管道 + 陰極保護�。� 參考：《西南石油大學》2015年碩士論文

【摘要】：川氣東送管道是繼西氣東輸管道又一條貫穿我國東西部地區(qū)的天然氣管道大動脈,其安全運營至關重要。管道運營2年后對防腐層進行檢漏和修復時,發(fā)現防腐層破損處管道均已出現不同程度的腐蝕,陰極保護系統(tǒng)并未起到很好地保護作用。因此弄清楚川氣東送管道的陰極保護狀況,并對陰極保護效果進行檢測與有效性評價非常重要。 論文針對川氣東送管道的陰極保護現狀,通過建立陰極保護電位數學模型,選擇了基于邊界元的數值模擬軟件Beasy CP開展檢查片現場檢測方案分析,同時利用極化曲線設計檢查片,從而進行檢查片現場試驗,最后基于檢查片檢測數據和陰極保護準則來分析與評價川氣東送管道陰極保護的有效性,并對陰極保護不合格管段提出針對性的整改措施。主要研究成果如下： (1)建立埋地管道陰極保護電位分布模型,通過對比常用數值解法,最終選擇了基于邊界元法的數值模擬軟件Beasy CP開展研究,為檢查片檢測方案分析奠定了基礎。 (2)根據建立的電位數學模型,考慮了川氣東送管道陰極保護系統(tǒng)的具體參數,運用軟件Beasy CP模擬檢查片形狀、檢查片面積、檢查片位置、管道防腐層破損率及土壤電阻率對管道與檢查片電位的影響,分析了檢查片現場檢測方案,并提出了對檢查片設計與現場試驗時的建議。 (3)基于檢查片的設計原理,總結了檢查片檢測的適用范圍,確定了川氣東送管道檢查片的5個試驗周期。測試了X70鋼在不同pH值的土壤溶液中的極化曲線,根據鋼質檢查片消耗電流的大小值計算鋼質檢查片面積,進而確定了檢查片的規(guī)格尺寸。同時對檢查片進行IR降預測,從而驗證了陰保檢查片面積大小不會影響真實電位的測量,最終確定了川氣東送管道檢查片組的設計方案。 (4)根據檢查片方案分析與設計進行檢查片現場試驗,制作檢查片組,布置了沿線40個檢查片試驗的檢測點,對檢查片進行埋設、定期開挖、通斷電電位測量、清洗、掃描電鏡(SEM)及XPS能譜分析,形成了一套基于檢查片的陰極保護檢測實施規(guī)程。 (5)基于檢查片檢測數據對川氣東送管道陰極保護進行有效性分析、評價與建議。 1)根據檢查片檢測數據分析了管道沿線39個檢測點的土壤腐蝕性分布,通過腐蝕產物的宏、微觀分析,從腐蝕產物的角度說明了陰極保護對管道腐蝕的抑制作用。 2)基于保護度評估了管道陰極保護效果,其合格率為44%。并將保護度與通斷電電位相聯(lián)系,得出了川氣東送管道的平均IR降為220mV,即保護電位(Uon)準則應取-1070mV (CSE);而當真實電位(Uoff)達到-850mV (CSE)時,其對應的最小陰極保護度不會低于65%,提供了陰極保護日常管理維護的依據。 3)以陰極保護檢查片的年腐蝕速率、通電電位和瞬時斷電電位三大準則為判據,分析和評價了川氣東送管道沿線39個檢測點的陰極保護狀況,其陰極保護合格率為74.4%,同時判斷出了10處陰極保護失效管段。 4)用風險評價和危險矩陣方法,繪制了以環(huán)境腐蝕性對“不保護度”作的危險矩陣圖,評估了各個檢測管段的風險等級,結果表明,無試驗管段位于最高風險區(qū)(V),且5、22、27和30號管段位于次高風險區(qū)(Ⅳ)。 5)分析影響川氣東送管道陰極保護的因素,提出了對陰極保護不合格管段具有針對性的整改措施,并通過管道電位監(jiān)測和現場開挖驗證了檢查片檢測技術的可靠性。
[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.
【學位授予單位】：西南石油大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TE88

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