Cathodic protection system design framework for the petrochemical industry

Abstract

The aim is to establish a cathodic protection (CP) system design framework for the petrochemical industry in South Africa. The CP system design framework is destined to be used as a guideline when designing CP systems for structures such as tanks, underground pipelines, and plant areas within the petrochemical industry. The necessary understanding regarding corrosion and corrosion mitigation in the form of CP is compiled and presented in the form of literature study chapters. Standards published by standards organizations such as the National Association of Corrosion Engineers (NACE) and the International Organisation for Standardisation (ISO) contribute greatly towards the proposed CP system design framework. The empirical equations and certain approaches taken towards CP system design as presented in these standards and in other sources of literature are used to structure the design framework. It is important to note that an empirical approach is used in the CP system design framework. Based on the design framework, the CP systems for the protection of a small tank farm and an underground pipeline are designed and documented. For verification purposes both these CP systems are implemented within BEASY™ CP and Corrosion. This software package, based on the Boundary Element Method (BEM) is used to visually evaluate the performance of the designed CP systems and to verify the design framework. An iterative approach is used throughout the verification process in order to adjust the design framework based on the results generated from the simulations. The validation of the design framework is based on a comparison of the results obtained from the simulation of the CP system of the underground pipeline network and actual measurements of potential at available test points installed on the underground pipeline network. The correlation between the actual measured results and the simulated results proved that the design framework can be successfully implemented for the design of CP systems. The accuracy of the simulated results for a pipeline that has been in service for 15 years were also satisfactory and extends the use of the CP system design framework to simulate and determine the life expectancy of a given CP system based on the initial design parameters. The cost of a given CP system will greatly influence the decision on the type of system to be installed. Although the dissertation mainly focuses on the technical challenges associated with CP system design, the important cost drivers for CP system design are highlighted throughout.