20 Years of Impressed Current Cathodic Protection Retrofit of Offshore Platforms Using MMO Tensioned Anode Strings

摘要

This paper presents the case of a cathodic protection retrofit undertaken on four steel gravity platforms, installed off the coast of West Africa in 86 m deep waters. The platforms, originally protected with galvanic anodes with a design life of 20 years, experienced insufficient protection conditions after only 10 years. A retrofit was planned in 1987 using an impressed current system with LIDA TSA~((TM)1) MMO anodes impressed current system, and the system was successfully commissioned in 1987. Protection conditions were achieved and continuously maintained from start-up for 18 years until 2005. It was decided to extend the life of the four platforms for an additional 20 years and to fully renew the CP system using the same technology. After 18 years of operation the entire CP system was replaced using MMO Anodes tensioned ropes; the new impressed current systems was commissioned in 2005 with a 20 years expected design life.