Abstract
The gas production in Northern Mexico has experienced significant growth in the last years. The fields are now exploited by a number of gas producers increasing the complexity of the Cathodic Protection(CP) systems. We report a case of study of a one year old 10” pipeline segment which was damaged by interference current discharge causing a significant number of gas leaks, and over 14 deep corrosion pits. The pipeline was fully removed and reconstructed along the discharge zone of over 2 miles. A CIS study was performed on the pipeline to find a zone of current pick up nearby an anode bed in service to other pipelines. This anode bed caused the pick up of current for over a year, and the CIS study also allowed to reveal the discharge zone.
A thorough documentation of this case study was possible due to the development of the CIS, as well as the access to the construction work during the repairs of the pipeline to the actual pits, and the assessment of the state of the Fusion Bonded Epoxy (FBE) and its defects. The calculations regarding the amount of current pick up and discharge, the metal losses associated to the interference and the correlation to the actual pits was made possible. This work lead to the establishment of recommendations for the CP design, construction and commissioning in the area, the coatings inspection, the CIS methodology and the needs of consideration of the many CP systems operating in this heavily congested zone of Northern Mexico.
