A new approach to assess the remaining strength of corroded steel pipes. (November 2018) - Mokhtari, Mojtaba
Abstract: Burst capacity models and Finite Element Methods (FEM) are the most common methodologies to assess the remaining strength of corroded oil and gas pipelines. These methodologies are shown as potentially excessively conservative or to present considerable scatter in their predictions, in part because they idealize the actual shape of complex pitting by simple approximations. The new approach introduced herein employs improved Finite Element modelling of isolated complex-shaped pit geometries, uses volume loss in the burst capacity models for the first time and is validated against several existing test results. In addition, the present study assesses the accuracy of FEM–based predictions based on the simplified pit geometries and also the precision of well-known burst capacity models. A burst capacity model is proposed herein which is practical, easy to use, more accurate and more stable than all earlier well-known models. Highlights: Burst pressures of pipes with complex pits are estimated using different methods. Good estimates are obtained with complex pits idealized to semi-elliptical shapes. The volume of complex pits is a key parameter for burst pressure calculation. Burst capacity models are modified using volume loss in their equations. The modification resulted in an easy-to-use, very accurate and very stable model.