Cathodic protection design optimization of a buried vessel by FEM simulation

Installing linear anode loops around a buried vessel is one of the latest cathodic protection anode arrangements for buried vessels. In this arrangement, besides the physical properties of the environment, for example, soil resistivity and oxygen content, the distance of anode loops to the vessel, number of anode loops, and distance between each loop are three main designing parameters. In the present study, the cathodic protection of a buried vessel (8-m long; 2.5 m in diameter) with complete nonlinear polarization at the protected surface is studied with finite element method simulation. The analyzed variables are the number of anode loops from one to three, the anode-to-vessel distance from 0.2 to 0.6 m, the distance between loops from 0.2 to 1.6 m. Soil resistivity varies from 10 to 500 Ω·m, and oxygen limiting current density changes from 5 to 100 mA/m². Increasing anode-to-vessel distances will reduce the potential differences, and the best condition is the maximum distance, 0.6 m. The optimum number of anode loops is two. Increasing soil resistivity will increase the potential difference, but in an optimum design, its effect is not significant.