A simulation software for the cathodic protection (CP) of underground pipeline networks is pre- sented. This software uses an advanced model for the coating quality, taking into account the local soil resistivity, holiday ratio, average holiday size, coating thickness and resistance.
The model considers the ohmic voltage drop in the pipes and integrates aboveground structures like rail bars, sub-stations, electric trains or trams and overhead wires. As a result the model gives the pipe- to-soil potentials along a pipe, the axial currents flowing through the pipes as well as the radial current densities leaving or entering the pipe walls.
The software can deal with all standard kinds of cathodic protection interferences as well as stray cur- rents coming from other CP installations, DC-traction systems, HVDC transmission lines, earthing sys- tems and others. A complex situation with railways interference is investigated and it is found that the numerical calculations are confirmed by qualitative observations.
Failures in oil or gas pipelines can have severe environmental and economic consequences. There- fore, large investments have been made in studies on corrosion prevention for buffed pipes. Important research is being conducted to determine and predict the corrosiveness of the soil, corrosion mechanisms in the ground and to develop effective protection techniques such as coatings for buried metallic struc- tures. Moreover, because of the hidden character of pipelines and their low accessibility, installation, survey, maintenance and repair is intricate, elaborate and expensive.
Numerical modelling can provide some relief by simplifying and optimising installation, maintenance and repair. When used in the planning phase, conceptual mistakes can already be traced before any ac- tual installation, by calculating different set-ups in cheap, harmless and fast simulations. Also, a model can provide reference values for measurements on operational sites, that can help in the tracing and solv- ing of any possible anomaly.
Last but not least, the model technique creates a safe and cost effective on screen 'virtual' test envi- ronment where new corrosion engineers can gain experience without long and expensive 'trial and error' experiments on site.
The development of such a mathematical model has been performed by former researchers of the Vrije Universiteit Bmssel (Belgium) and commercialized under the name CatPro (1). The mathematical details and the validation of the model have been discussed in detail in previous publications 13. In the present paper the basic ideas and all fundamental aspects of the model are explained.