Crack-detection ILI tools that rely on shear-wave UT have improved significantly in both detection probability and sizing accuracy. The Quest Integrity Group employs realistic fracture-mechanics’ models that use 3-D elastic-plastic finite-element analysis. The combination of advanced modelling and reliable ILI provides a superior alternative to hydrostatic testing for ensuring pipeline integrity.

ILI tools that measure wall loss with compression-wave UT provide superior results compared to MFL tools. The former outputs a digital map of individual thickness readings, which is ideally suited to effective area assessment methods such as RSTRENG and the API 579 Level 2 remaining strength factor (RSF) calculation. Quest Integrity has developed software that can rapidly process large quantities of ILI wall-loss data and evaluate the maximum allowable operation pressure (MAOP) at discrete locations. The ranking of these MAOP values serves as a rational and rapid means for prioritizing the severity of corrosion throughout the line.

Dents that are introduced during fabrication, installation, or by a third party are the most common source of failure in pipelines. Traditional assessments are based on a simplistic characterization of the dent (such as the ratio of the dent depth to the pipe diameter), combined with a simple empirical equation. An advanced dent assessment that combines a detailed mapping of the dent from ILI data (either UT or a caliper pig) with 3-D elastic-plastic finite-element analysis is also described in the paper. A dimensionally-accurate 3-D model of the dented pipe is subjected to cyclic loading, and remaining life is computed through a proprietary low-cycle-fatigue damage model. This advanced methodology can be applied to interacting anomalies such as dent/gouge and dent/crack combinations.