The report discusses cathodic protection (CP) experiences on the world’s longest, most complex crude oil and liquid hydrocarbon transportation system; having 24,738 kilometers (15,372 miles) of pipeline throughout North America. Since initial construction of the first pipeline in 1949, infrastructure has continually been enhanced and improved to meet the needs of the Company’s shippers. The expansion has resulted in areas of the mainline corridor where up to seven (7) parallel pipelines are contained within the same right-of-way (ROW).
The evolution of construction materials over the course of the Company’s long operating history has contributed to the diversity within the ROW. Early coating systems included asphalt, coal tar epoxy, and mummy-wrap. Polyethylene tape coated pipe was installed in the late 1960’s and 1970’s. Since the 1980’s, the Company has favored high performance coatings such as fusion bonded epoxy, dual layer epoxies, and high performance composite/powder (HPCC/HPPC). Presently, the ROW includes an assortment of pipeline vintages with various diameters and coating types which can consequently result in unbalanced CP levels.
This Project includes in-depth research and analysis of various methods, procedures, and materials beneficial in regulating and maintaining appropriate levels of CP in complex multi-pipeline corridors. Associated rectifiers are all furnished with remote monitoring equipment and the majority of test stations have been retrofit with coupons enabling remote surveillance of real time CP/AC potentials and corresponding current densities. All Project pipelines are regularly evaluated using inline inspection tools equipped with technologies to identify metal loss, and some of the pipelines have been inspected using inline tools capable of evaluating CP currents flowing in the pipe wall. These data have been consolidated and used to generate a computational model providing a more accurate representation of CP levels on each pipeline within the shared ROW. The purpose of such a model is to refine testing procedures, develop corrective measures and establish new guidelines for optimizing CP operation and effectiveness within ROWs containing multiple pipelines.
Rationally managing and harmonizing CP levels within such multifaceted arrangements is necessary to accommodate the pipelines having a high current demand, while avoiding the detrimental effects of overprotection on adjacent, newer pipelines with high efficiency coating systems.
This CORROSION 2015 paper has also been highlighted in the September issue of Materials Performance (MP) magazine on page 41.