Grounding arrangement in direct electrical heating systems

FE computations are performed to investigate the current load on anodes and pipeline in the current transfer zone (CTZ) of a Direct Electrical Heated flowline. It is shown that there may be great differences in the current load on the anodes, and that there is a significant increase in the current density towards edges and corners. A simple model based on laboratory measurements show that these current densities may cause a very uneven net charge transfer on the anodes, which may indicate accelerated corrosion. In addition, current densities in coating holidays are investigated, showing that the pipeline may be exposed to high crack currents just outside the CTZ. FE analysis can be used to design the grounding arrangement such that anode loads and crack currents are within acceptable levels.