OPTIMIZATION OF PARAMETERS OF ELECTRIC FIELD OF GAS PRODUCT AND OIL PIPES CATHODIC PROTECTION

Abstract

The relevance of the research is caused by discrepancies in design of cathodic protection of pipelines. Electric current, flowing from anodic protection to the ground, spreads there and then enters the protected pipeline polarizing its cathode. Certain assumptions are taken to describe the patterns of change imposed by the potential and strength of the polarizing current along the length of the pipeline at a cathodic protection. There are significant differences between design and actual parameters of protection in settlements of cathodic protection of pipelines. The main aim of the research is to propose an algorithm for solving a boundary value problem for the potential of the electric field of cathodic protection of an underground pipeline by a vertical depth anode based on the method of fictitious sources. Objects: gas and oil pipelines, for which protection against electrochemical corrosion is a necessary condition for ensuring an optimum period of their operation. Methods. Based on the method of fictitious sources the authors have proposed the algorithm for solving the boundary-value problem for capacity of the electric field of cathodic protection of underground pipeline vertical deep anode. Application of the method is justified by the principle of electrostatic analogy for spatial task of electric field distribution. Results. To apply the established relation to this problem in half, the method of mirror reflections is used additionally in the algorithm that allows transferring the task from half to space. The C++ computing code is developed for numerical calculations of electric fields in the systems of cathodic protection of pipelines via deep anodes subject to the restrictions on the electric potential of the protected structure and the density of current, flowing from the anode. The computer model allows conducting a set of numerical experiments for selection of geometric and electrochemical parameters of designed deep anode, to improve the reliability of cathodic protection for underground structures and increase the duration of their service life. The paper introduces the graphs illustrating the features of current density distributions along the depth of anode and the protective capacity of the pipeline, with changes in the external environment for a certain period of operation. It was shown that at decrease in insulation resistance the increase in cathodic station current is required for maintaining the necessary protective pipeline capacity. Current density at the «anode–ground» boundary increases that leads in its turn to more intensive anode dissolution. The paper introduces the examples of numerical results obtained based on real data conditions. The analysis of the results confirms the effectiveness, stability and versatility of the algorithm developed.

Keywords

• deep anode
• cathodic protection
• computer simulation
• method of fictitious sources
• potential
• electric field
• electric current