Research On Key Technologies Of Impressed Current Cathodic Protection System For FPSO

FPSO is located in a sea area far away from the coast for long-term operations.It cannot be repaired and maintained regularly in the dock like ordinary ships,and serious corrosion phenomena are prone to occur.Therefore,corrosion protection is particularly important for the long-term normal operation of the FPSO.The corrosion protection of FPSO generally adopts a combined corrosion protection method of coating and cathodic protection,and cathodic protection is divided into sacrificial anode and impressed current.Cathodic protection of impressed current has many advantages over sacrificial anode,so in this paper,a detailed study of the impressed current method will be carried out,including the research on the auxiliary anode of key components and the optimization study of the layout of the auxiliary anode of the impressed current cathodic protection system for FPSO.The auxiliary anode is an important underwater component of the FPSO cathodic protection system,and its performance directly affects whether the cathodic protection system can reliably protect the hull for a long time.In this paper,the research on the material and structure design of the auxiliary anode was carried out.Aging test for hypochlorous acid resistance was carried out on the packaging material of the auxiliary anode,scouring resistance test was carried out on the coating material of the auxiliary anode,and an enhanced life test was carried out on the electrode material.The reliability of the auxiliary anode material was verified through the above series of tests.At the same time design and verify the structure of the auxiliary anode,including watertight design,packaging design,etc.The watertightness test and insulation test were carried out on it.The test results showed that the watertightness and insulation performance of the auxiliary anode met the design requirements.Finally,a set of long-life and high-reliability engineering-available MMO anode solutions encapsulated in corrosion-resistant rubber and fiber-reinforced composite materials was determined.Based on the numerical simulation technology of impressed current cathodic protection and the auxiliary anode scheme determined by the above study,the protection of the FPSO hull structure during the 30-year full-life period is numerically calculated.Set the relevant corrosion protection parameters according to the cathodic protection specifications and the actual operation sea conditions of the FPSO,and simulate the changes of the protection potential of the hull structure of the FPSO during the whole life.According to the numerical simulation calculation results,the layout position and number of auxiliary anodes in the FPSO hull structure and the output current of each anode are optimized.Finally,a set of auxiliary anode layout scheme that can ensure the normal operation of FPSO and the annual output current of each anode during the design life were determined.The protection potential of the target FPSO hull structure is always between the designed protection potential of-800 mV and-1100 mV for 30 years with this system.The hull potential has been in good condition throughout the protection period.The calculation results show that the designed impressed current cathodic protection system can play a good role in corrosion protection,ensuring the normal operation of the FPSO during the 30-year life span.The research results of this paper can provide reference for the design of cathodic protection of FPSO,and have certain practical value in engineering.