Prediction of corrosion and residual life of submarine pipeline with grey theory

Corrosion is one of the main factors causing failure of submarine pipelines. It is important to measure and predict the corrosion for submarine pipeline's safety. A formula of ultimate pressure of submarine pipeline in the case of both uniform and local corrosions is derived according to ASME B31G. In the formula, the local corrosion is simplified as rectangular flaws with uniform distribution along the longitudinal direction. Grey theory is utilized to predict the development of uniform and local corrosions respectively. Based on result of prediction, the ultimate pressure and residual life of the pipeline are calculated. Due to the complexity of the mechanism of local corrosion affecting the pipeline strength, only the influences of local corrosion along the longitudinal direction on the ultimate pressure of pipeline are considered. How other complex factors such as the width of corrosion, corrosion along the vertical direction and interaction of pits, etc. affecting the ultimate pressure of pipeline are needed to be studied further.