Corrosion of steel pipes is a critical issue in oil and gas industry. As the service life of pipes increases, the pipes roughness increases due to the accumulation of different corrosive elements around the internal surface of the pipes. This project aims to investigate the effect of the age of pipes on the performance of natural gas transmisson pipeline network system (TPNS). A simulation model was develop in MATLAB programming code based on Newton Raphson method to detemine the unknown pressure and flow parameters.