地下管線陰極防蝕電流失效檢測

Inspection on Underground Pipeline for Failure of Cathodic Protection

邱德俊(Der-Jiunn Chiou) ； 林秉賢(Bing-Sian Lin) ； 許峰彰(Feng-Jang Shiu)

《石油季刊》 46卷1期 (2010/03) Pp. 77-86

https://doi.org/10.30128/JP.201003.0007

摘要

地下管線和其他管線或其他結構物的接觸，常常衍生出對各個管線或結構物管理及操作上的不良影響。特別是地下輸油氣管線，由於地下輸油、氣管線所使用的管線材質絕大部份是鋼管。為了避免其在土壤中的自然腐蝕，這些鋼管的外層會包覆柏油或聚乙烯等絕緣包覆材料，利用完全隔絕周圍環境的方式 避免腐蝕，在此同時輸送油、氣的管線也同時採用電化學陰極防蝕來保護管線，共同對抗腐蝕。
在擁擠的道路下方，這些長途油氣管線常常和其他管線或結構物碰觸、擠壓造成絕緣包覆破裂，使得管線鋼管暴露在土壤中及與其他管線或結構物的接觸和遮蔽。一旦管線暴露在土壤中，腐蝕因子立刻攻擊鋼管，使其產生腐蝕、減薄。若管線和其他結構物或鋼管形成遮蔽搭接或電氣連通，即使在有陰極防蝕系統保護之下管線仍會產生腐蝕，甚至加速腐蝕。
在台灣，管線擁擠的埋設方式是無可避免的方式，如何在管線已產生絕緣包覆破損或與其他結構物產生搭接形成電氣連通時，立即找出其問題點成了預防管線腐蝕洩漏的最佳方式。本文中，作者利用傳統的緊密電位法及管線地表電流量測結果對管線和外界結構物的搭接進行分析，找出搭接位置，克服了以往無法判斷異常原因的困擾，可以在搭接的問題一開始出現時，提供立即解決的能力。

關鍵字

陰極防蝕 ； 極化 ； 緊密電位

並列摘要

The electrical contact of pipeline with third party underground structure will definitely cause many serious problems. It was raise some troubles on management and operation. Most of underground pipeline were made form steel. For the reason of against on natural corrosion in soil environment, to wrap asphalt or PE coating is the basic necessity. At the mean time, we should install a cathodic protection system for pipeline. It's the best method on anti-corrosion for underground pipelines. The system can protect pipeline in electrochemistry for twenty years or longer. Pipeline receives adequate cathodic current into surface of pipe for soil by way of auxiliary anode. The whole system is a closed electrical loop.
Pipeline buried under the ground were laid beside or underneath other pipeline or structure often. The coating sometimes could be destroys by third party pipeline or structure under vibration or movement by heavy vehicle and construction. Once the coating damage, the steel surface will be exposes in soil environment. Corrosion will take place immediately. If we can't find that and correct the defect, the weight losing and pitting will undergo in silent. Pipeline also will be electrical contact with other pipe or structure. After that, even if we provide more negative current, it's no any help on anti-corrosion.
In Taiwan, pipelines all were buried under congested road. That electrical contact with other pipelines or structures for pipeline is inevitable. How do we locate it is a serious object. In this article, the combination of two different inspect methods has been used for the solution. The close interval potential survey was used for finding an abnormal section of pipeline. The pipeline current measurement was being demarcated the worst area on cathodic protection current distribution. We analyzed all the data to locate the most possible contact point.

並列關鍵字

Cathodic Protection ； Polarization ； Closed Interval Protection Survey