Chapter 30 REVIEW OF PIPELINE INERTIAL SURVEYING FOR GROUND MOVEMENT-INDUCED DEFORMATIONS

This paper provides a state of practice review on the subject of in-line inspection (ILI) of pipelines using strapdown Inertial Measurement Unit (IMU) tools. The paper describes the IMU tool instrumentation (gyroscopes, accelerometers and odometers) and discusses processing of IMU data including basic processing of the raw data and the fundamentals of numerical integration of the gyroscope and odometer data into pipe position or out-of-straightness (OOS) coordinates and numerical differentiation of the gyroscope and odometer data into profiles of vertical, horizontal and total curvature/bending strain. A summary of typical IMU tool sensitivity and accuracy specifications is provided together with some commentary on pipe position accuracy and bending strain accuracy. The paper explains in detail how ground movement-induced or construction imperfection bending strain signatures are distinguished from curvature signatures corresponding to intentional bends in the pipeline (such as cold bends or elbow fittings). The paper also provides a detailed description of ways to best characterize pipeline bending strain features including tabulation of key parameters and spatial plots which graphically display pipeline geometry profiles at features of interest including plan and elevation profile (or out-of-straightness profiles), pipeline orientation (pitch and azimuth) profiles and profiles of vertical, horizontal, and total bending strain. The paper also outlines a framework for prioritization and integrity screening of identified bending strain features, possible responses to these features and a strategy for ongoing inertial survey monitoring of identified bending strain locations.