This is a case history of a large diameter pipeline with fusion bonded epoxy coating that experienced AC corrosion after being in operation within six (6) years while the existing 67-year-old large diameter pipeline with coal tar enamel coating experienced no AC corrosion. An AC study was completed after installation of the newer pipeline but showed no immediate threat. This paper presents a post mortem assessment after 17 years of what is required and the importance of not taking adequate data when AC load factors were not posing a threat condition. If it were not for the operator's due diligence to run an in-line-inspection device, this ongoing condition would have gone unnoticed. This paper provides the understanding of the need for complete information, data required for AC modeling, corrosion threats and mitigation. AC mitigation modeling was in already in place which could have been used effectively. The first AC modeling was developed by Dr. John Dabkowski for the Pipeline Research Council International (1) (PRCI).
(1)Pipeline Research Council International (PRCI) - 3141
Steady State Conditions, Fault Conditions, Alternating Current (AC) Current Density, Mitigation, Interference, Fusion Bonded Epoxy (FBE), Coat Tar Enamel (CTE), High Consequence Areas (HCAs).