Justin M. Crapps

Strain Capacity Prediction of Strain-Based Pipelines

Strain-based design (SBD) is used to complement conventional allowable stress design for pipelines operated in environments with potentially large ground movements such as those found in permafrost and seismically active regions. Reliable and accurate prediction of tensile strain capacity (TSC) plays a critical role in strain-based design. As reported previously over the past 6+ years, a comprehensive experimental and numerical program was undertaken to characterize the TSC of welded pipelines, develop a finite element analysis (FEA) approach and equations capable of predicting TSC, and establish a strain-based engineering critical assessment (SBECA) methodology. The previous FEA model and TSC equations were validated against about 50 full-scale pipe strain capacity tests and are accurate within the validated variable ranges. In the current paper, enhancements of the previous model and equations are described. The enhancements include incorporation of advanced damage mechanics modeling into TSC prediction, development of a new TSC equation, expansion of variable ranges and functionality upgrades. The new model and equation are applicable over larger ranges of material properties and flaw sizes. The new FEA model is also used to establish surface flaw interaction rules for SBD. The new FEA model is validated against more than 40 full-scale non-pressurized and pressurized tests and underpins the development of the new TSC equation. The equation is validated against a total of 93 full-scale tests (FST). In addition to the enhancements, sample applications of the TSC model and equation are presented in the paper, for example, an investigation of the effects on strain capacity of Luders strain and ductile tearing. Challenges in predicting TSC are also addressed.Copyright

Pipeline In-Line Inspection Enhancement Opportunities

Pipeline in-line inspections (ILI) are one of the primary methods used to assess the integrity of operating oil and gas pipelines. These inspections can be complicated to conduct due to a variety of reasons ranging from operational limits (high/low flow velocity, wall thickness, pipeline extreme depth or pressure, etc.) to limits inherent to the inspection technology. Often these complexities are overcome with tools customized to a specific pipeline. Although this has been effective for singular pipeline inspections, a more industry-wide approach should be considered to develop broader solutions. This paper discusses the opportunities to enhance ILI and suggests a ranking of priorities for technology development.Copyright