Experimental Study and Finite Element Modelling of the Cathodic Protection Influence on Parallel Pipelines During Maintenance Operations

Dense buried pipelines network, such as in implemented in parallel, can be installed in different process and storage mills, such as geological gas and hydrocarbon storages. Their corrosion resistance is ensured by a combination of organic coating and cathodic protection (CP). For maintenance operation on a specific pipeline, the CP can be turned off for safety reasons. Thus, the operated pipeline can be affected by CP influence from other surrounding protected ones. This phenomenon is supported in the field by different pigging inspections, highlighting local corrosion induced by output stray current on coating defects. In the literature, many studies focused on CP influences by finite and/or boundary element modeling. However, usually the foreign structures considered (under influence) are limited to bare steel or fully coated pipeline. Moreover, most of these studies are not confronted with experimental works. To our knowledge, the actual influence between the different pipelines is not much documented in the literature and not quantified. In this study, an experiment consisting in 3.00 x 1.80 x 0.80 m sand tank, equipped with 4 full scale parallel pipelines, with 17 model defects were realized. The model defects reproduce uniformly degraded coating and local defects. The experimental work allows i) measuring the DC influence under different CP configurations, and ii) providing stray current data for finite element modelling (FEM). The FEM was performed in a two steps i) a CP distribution in terms of current demand and electric field on protected pipelines, and ii) application of this electric field to the foreign pipeline. The good agreement obtained allows a validation the proposed approach and globally assess the riskier scenario in terms of nature of the defect, applied CP and soil environment.
Product Number: 51324-20713-SG
Author: Erwan Diler; Yves Zannier; Alexandre Billot; Flavien Vucko; Tiphaine Lutzler
Publication Date: 2024