Engineering Critical Assessment of Dents and Dents With Cracks Using Inline Inspection Data

Dented pipes with typical strain measurements greater than 6% are considered unacceptable, and further assessment using the finite element (FE) procedure is conducted. FE procedures are conducted using specific dent profiles based on the shape of indenters. The actual shape of a real dent differs from the simplified dent shapes that are assumed in engineering critical assessment, thereby compromising the accuracy, especially if there are two side-by-side dents. Several papers used simplified indenter profiles to generate strain and critical damage values. Such a simplified profile can generate non-conservative results, especially if there is an interaction with a nearby dent or residual stresses from the weld. These drawbacks are resolved using an innovative workflow outlined in this paper. This paper elaborates on developing an approach by creating the dent surface from the ILI measurement data to evaluate the dented pipes. The results illustrate the importance of using accurate ILI measurement data to obtain dent strains and dent-based damage. Residual stress from the presence of weld adjacent to the dent can also be used conveniently by these approaches and is more amenable for the wider types of analyses. Approaches outlined in the paper will also illustrate how to analyze the dented pipes with cracks conveniently. The presence of cracks at the dent would significantly increase the stress intensity factor. Crack assessment for dents with cracks is a tedious FE procedure, which can be simplified using the polynomial stress distribution. Stresses from a dented profile with the cracks are obtained using this analysis which can thereby be used for crack assessment. Stress intensity factors of the cracks in the dent can be obtained using these approaches and can be further used for crack assessment. Finally, the remaining life of dented pipes with and without cracks is presented using the FE analyses results.