A calculation method for the failure probability of gas-liquid two-phase flow pipeline caused by internal corrosion

A gas-liquid two-phase flow pipeline is widely applied in oil and gas exploitation, gathering and transportation, so its safe and reliable operation is of vital significance in theory and engineering. Among all types of failures, the internal corrosion is one of the most important reasons for the structural failure of gas-liquid two-phase flow pipeline. In this paper, the pipeline internal corrosion rate prediction model and the structural reliability evaluation method were combined together to calculate the failure probability of gas-liquid two-phase pipeline caused by internal corrosion. Firstly, in view of the flowing characteristics of gas-liquid two-phase flow, the internal corrosion rates of gas-liquid two-phase flow pipeline under different flow patterns were calculated by means of fluid phase equilibrium model, gas-liquid two-phase flow model and corrosion rate prediction model. Then, considering the uncertainty of pipeline operation and manufacturing, the pipeline failure probability of small leak and burst was calculated by Monte Carlo approach based on the limit state function of corrosion defect recommended in the specification Manual for determing the remaining strength of corroded pipelines(ASME B31G-1991), combined with the calculated corrosion rates. Finally, this calculation method for internal corrosion induced failure probability was applied to one certain gas-liquid two-phase flow pipeline. By virtue of this method, the failure probability can be predicted effectively and the transportation safety of oil and gas pipelines can be ensured when there is no valid internal detection data or the actual pipeline transportation process changes.