Coatings and CP
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Cathodic protection is almost universally applied to buried and immersed structures in the oil and gas industry. Amongst other things it is applied to pipelines, above ground storage tanks, buried storage tanks, and buried pipe works in above ground installations. The amount of cathodic protection current required to stop external corrosion is provided in the various standards. The actual amount of current required is determined by the coating condition (if any) and the environment that the structure is buried or immersed in. The standards provide guidelines for the design of cathodic protection systems by advising the cathodic protection current density required for bare steel and the efficiency of the applied coatings over the design lifetime of the structure. There are two types of cathodic protection used, one being by remote ground beds and the other using linear anodes that continuously follow the contours of the structure to be protected. Anodeflex was developed more than 30 years ago by Raychem and has been in continuous use ever since. The product has improved and matured over the years and the current output ranges have been increased. Anodeflex is an anode that looks like a cable. The outer layer of the cable is actually a conductive anode and provides the cathodic protection current over its entire length. The anode is laid close to the structure in question and provides current directly to the structure. This means that rather than injecting large amounts of current at a location that could be remote from the pipeline defect the current is distributed from the close anode to exactly where it is needed. The anode “cable” is installed within a sock and comes complete with its own backfill and can be laid in the pipeline trench or close to the pipeline.
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