Cathodic protection survey data from a major gas transmission pipeline is reviewed to determine the accuracy of the original design calculations. The calculations used to predict cathodic protection requirements are discussed to show the advantages and limitations of different methods. The analysis shows that the design calculations can predict overall trends, but significant variations can exist locally due to variations in the pipeline and its environment. Observed coating conductance values and recommendations for improved methods are given to aid in the design of future pipeline cathodic protection systems.
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