L51884 Assessing the Remaining Strength of Corrosion Defects in Low Toughness Linepipe Materials

One of the principal causes of failures of transmission pipelines is volumetric metal loss due to corrosion. Various methods such as ASME B31.G, RSTRENG and the LPC methods have been developed to assess the severity of corrosion defects. The methods have developed to the extent that they are recognized by standardization bodies and regulators. However, all the methods have been developed and validated on high toughness materials. There is a concern that these methods may give non-conservative results if they are used for low toughness materials. If this is the case, guidance is required on the limits of applicability of the current methods, and new methods are required for application to low toughness materials.

To investigate these issues, contractor objectives and scope were: To test a range of representative defects in low toughness linepipe; to assess the failure mode of these defects; to determine if current assessment methods can be applied to low toughness materials; and to identify the factors influencing the failure of corrosion defects in low toughness line pipe.