Pipeline dents can be developed from the pipe resting on rock, a third party machinery strike, rock strikes during backfilling, amongst other causes. The long-term integrity of a dented pipeline segment depends upon parameters including pipe geometry, indenter shape, dent depth, indenter support, secondary features, and pipeline operating pressure history at and following indentation. US DoT and other standards include dent repair and remediation criteria broadly based upon dent depth, dent location (top or bottom side), pressure cycling (liquid or gas), and dent interaction with secondary features (weld, corrosion, cracks). These criteria are simple and easily applied, however, they may not direct maintenance appropriately and be overly conservative or, in some cases, unconservative. Previous IPC papers have discussed the full-scale dent fatigue testing and dent modelling efforts to support integrity management criteria development by collecting material and structural response during dent formation and pressure loading. The present paper will present the results of this extensive dent structural and fatigue life numerical simulation program using a validated finite element (FE) analysis process. The paper describes the numerical simulation technique, as well as, the development of the novel engineering tool for integrity management, eliminating the need for numerical simulation of individual dent features to assess the relative integrity threat they pose. The development of the engineering tool presented in this paper considers the dent formation, re-rounding and through life response to pressure fluctuations to evaluate the fatigue life of dent features. The results of these analyses are used to develop fatigue life trends based on dent shape, restraint condition and operating pressure. These trends were used to develop models to predict dent relative severity and life based upon ILI inspection dent shape data for single peak dents. Dent shape has also been used to determine the restraint condition of a dent and its influence on the dent feature fatigue life. The tools were developed to address many of the uncertainties inherent in existing regulatory repair and remediation criteria. Current and future applications of the integrity assessment model are described along with recommendations for further development and testing to support pipeline integrity management, industry guidelines and standards. The results of this research will be of use in improving integrity management decisions and support further development of industry guides and standards. As such the information presented in this paper will be of interest to pipeline operators, integrity management specialists, in-line inspection (ILI) organizations and regulators. The recommendations presented in this paper may be used to influence the direction of pipeline standards in their direction in the disposition of dent features.

Fracture mechanics methodologies for calculating fatigue lives have been successfully applied by pipeline operators to estimate integrity reassessment intervals. Their application in the definition of pipeline system fatigue lives has been overly conservative in actual practice. The source and magnitude of the conservatism inherent in the calculated fatigue life estimates needs to be identified so operators have a better indicator of when reassessments should take place. The pipe life estimation is especially critical for Electric Resistance Weld (ERW) and Electric Flash Weld (EFW) pipeline systems with longitudinally oriented defects. Prior work on improving fatigue life was initiated through studies completed by Pipeline Research Council International, Inc. (PRCI) to evaluate the sources of differences between fatigue life estimates produced by industry fatigue analysis software and different metallurgists. Two significant sources of conservatism in the fatigue life estimation process were identified: the fatigue crack growth rate (da/dN) and the bulging correction factor applied to axial surface flaws. The experimental and numerical simulation techniques considering the impact of these factors on rate of fatigue crack growth of pipeline axially oriented defects are described in this paper. Finite element modeling was used to simulate pipe bulging in the presence of axial flaws. The effect of the pipe thickness, diameter and flaw geometry was compared with treatments included in existing defect assessment standards. The results illustrate that for longer and deeper flaws existing treatments over represent the local bending due to pipe wall bulging. This results in unnecessarily conservative (shorter) fatigue life estimates. The crack growth rate (da/dN) was measured in a compact tension specimen material fatigue testing program. The test results included a range of ERW and EFW pipe materials with varying vintages and grades. The measured fatigue crack growth rate for the materials tested was found to be lower than that recommended by existing industry standards. This adds to the over conservatism of current approaches. The numerical simulation and materials testing results and related recommendations presented in this paper are compared to existing codified treatments to quantify the level of conservatism inherent in the current state of practice. Recommendations are provided to enhance the precision and better manage conservatism in fatigue crack growth rate calculations. Increased accuracy serves to improve integrity management and would be of interest to pipeline operators, consultants and regulators.

Pipeline defects such as cracks, dents and corrosion often require permanent pressure retaining repairs. Full encirclement metallic repair sleeves with fillet-welded end connections to the pipeline are often used for this purpose. In-service failures have occurred at pressure retaining sleeves as a result of defects associated with the sleeve welds, such as hydrogen-induced cracks, undercut at the fillet welds and inadequate weld size. At present, accurate quantitative fitness for service assessments for circumferential defects in a sleeve fillet welds are difficult to carry out due to a lack of detailed stress intensity factor (SIF) solutions for finite length cracks. The primary objective of the project presented in this paper [1] was to develop flaw acceptance criteria which will fill gaps in the available Engineering Critical Assessment procedures for metallic sleeve repairs on all grades of pipelines. SIF solutions for finite length sleeve-end fillet weld toe and root cracks were generated and used to develop parametric equations suitable for carrying out defect assessments. These equations can be used in the assessment of fatigue crack growth and/or fracture using failure assessment diagram (FAD) methods at sleeve end fillets alongside the results developed for other structural geometries in national standards. The equations were developed based on detailed finite element (FE) analyses of a wide range of sleeve end fillet weld cracking scenarios to estimate the SIFs at both the deepest point and the surface breaking point along the crack front.

Presented Thursday, September 5, 2019 PRESENTER: Vlad Semiga HOST: Rober Lazor, TC Energy MODERATOR: Thomas Marlow, PRCI Expected Benefits/Learning Outcomes: - Attendees will be given an overview of the sleeve end fillet weld stress intensity factors (SIFs) software, which provides a simplified means of estimating the SIFs for a single scenario or for an unlimited number of scenarios defined using a standard batch file format; - the presentation will also include the results of a sensitivity study illustrating the general trends in terms of the SIFs versus the range of inputs used to define an assessment scenario; - and the use of the SIFs in a standard integrity assessment (engineering critical assessment of fitness-for-service assessment) will also be demonstrated. Target Audience: - Pipeline design engineers - Welding specialists and engineers - Integrity management personnel Recommended pre-reading: Project final report: PR-214-174517-Z01 Development of Sleeve End Fillet Weld Stress Intensity Factor Calculator

Note that this version of the final report DOES NOT include the suite of experimental data.