This paper will detail the thirty year history of the use of linear anode anodes to protect older generation pipelines with aging coatings. The presentation will discuss the original polymeric linear anode and the product's history of evolution to today's MMO coated titanium wire anode. The paper will then discuss aging pipelines and the problem that creates for the effective application of cathodic protection. The paper will briefly discuss recoating as an option before diving into the application of linear anodes including installation methodologies and design considerations. The paper will then present some case stories and examples of successful installations.
There is a long and successful history of using linear anodes to cathodically protect older generation pipelines with aging coatings. The use of linear anodes to address poor cathodic protection distribution has proven to be easier and more cost effective than large scale recoating projects. While the use of linear anodes is common in the United States, there are many similar vintage pipelines in Europe, the Middle East and Asia which struggle with the same challenges and for whom this technology should be of great interest.
The first linear anode product appeared in the mid to late 1990s. It was a revolutionary anode concept – a flexible long length anode cable intended to operate at low current outputs. This first generation linear anode included several key features that remain the standard for today's linear anodes: packaged sock diameter, fabric housing, and braiding to protect the fabric housing and help ensure even coke compaction. There were also some unique flaws in the first generation linear anode. The anode material itself was a conductive polymer formulation that doubled as the insulation on the anode lead wire.
This dual role of anode and cable insulation was a major flaw. Notably, the use of a polymeric anode while extremely creative, was a very poor choice of anode material. The polymeric anode is subject to cracking at any area of localized high current output. Since the anode also doubled as cable insulation, when the anode cracked, the conductor was exposed and quickly went into solution yielding to an open circuit anode failure.
