Cathodic Protection Analysis of Spools With GRP Cover

Cathodic protection (CP) design of pipelines is generally described in internationally recognized standards and recommended practices. However, not all cases can be solved by conventional CP calculations as recommended approaches and methods may not be fully defined in the standards. For instance, Glass fibre Reinforced Polyester (GRP) covers can be applied for mechanical protection (e.g. from trawl and/or dropped object) of subsea pipelines and structures. These GRP covers will restrict the electrical/ionic current lines between the anode and the steel surface to be cathodically protected. For a spool with in-line components requiring a large current (e.g. painted or bare steel) and with a GRP cover it may be difficult to obtain sufficient cathodic protection when applying simple mathematical calculations. This paper describes how the Finite Element Method (FEM) in COMSOL Multiphysics can be applied to show that the potential is acceptable for such cases.