Redesign of ICCP System for Ladinda FSO for Effective Corrosion Protection

摘要

The Impressed Current Cathodic Protection (ICCP) System is a corrosion control method where there is a flow of electrons to a metal structure, thus protecting it. As a ship owner, the EMP Malacca Strait SA used a coating method combined with the ICCP system to control corrosion on the Ladinda FSO. However, nowadays, the Ladinda FSO is known to carry a decreased volume of oil cargo due to declining oil production. This results in a change in the wetted area on the tanker’s hull in the design conditions of the ICCP system from early 1983 to the current conditions (2010) that affect the current magnitude of the protection given. This leads to an overprotection that destroys the coating layer. To avoid over-protection on the hull of the Ladinda FSO, an analysis and redesign of the ICCP system has been conducted. In the redesign of the cathodic protection system on the Ladinda FSO, the NACE Standard RP 0176- 2003 “Corrosion Control of Steel Fixed Offshore Structures Associated with Petroleum Production” was used as a basic reference in the design. The first step was to make the initial ICCP system design and then rebuild the initial ICCP system design for cathodic protection according to recent conditions. Next, the new design was analyzed and the results are the recommendations. The monitoring system was also redesigned to maintain proper control at a range of –1100 mV to –800 mV vs. Ag/AgCl/seawater. The new design will needs two transformer rectifier units as the power supply, which will give sufficient voltage to drive six titanium anodes coated with mixed metal oxide (MMO). The capacity of each transformer rectifier is 236.25 kV.A with a DC current of 21 A and DC voltage of 9 V. Four potential test boxes featuring Ag/AgCl reference electrodes and the “Protection Current Control Program” as the control system and monitoring system are added in this new ICCP system design.