51313-02333-Modeling of Potential Distribution of Subsea Pipeline Under CP by Finite Element Method

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Product Number: 51313-02333-SG

ISBN: 02333 2013 CP

Author: Paolo Marcassoli

Publication Date: 2013

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This paper deals with the evaluation of the subsea pipeline integrity through the combination of potential profile electric field gradient and the modeling of the electric field by Finite Element Method (FEM) originated by the bracelet galvanic anodes. The potential profile as well as the electric field gradient measured during a survey provide the representation of the CP level and the location of anodes and coating defects. Nevertheless by overlapping the electric field calculated by a dedicated FEM modeling a more accurate interpretation is achieved in order to estimate the critical coating defect size and to evaluate the effect of the presence of multiple defects. FEM modeling was based on a simplified 2D domain reproducing the main geometrical physical and the electrochemical parameters such as sea depth mud burial depth seawater and mud resistivity and current density and potential distribution. Boundary conditions were defined by assuming constant potential at galvanic anode electrical insulation of the coating and by considering Butler-Volmer equation for steel surface at coating defects. Coating defect size sea depth mud burial depth were considered in a generalized parametric equation. An example of the application of the model is shown on the basis of results obtained by an inspection campaign