Use of Inertial Measurement Unit In-Line Inspection Data to Support Code Stress Compliance and Integrity Evaluations

Abstract

Pipelines are an essential segment of infrastructure required to transport a variety of products to markets in our economies. The integrity and safe operation of those pipeline necessitates that pipeline operators have a thorough understanding of their pipeline systems, their configuration, and the changing operating condition within their pipeline networks. Inertial measurement unit (IMU), a technology that can measure the angular rate and acceleration and when combined with global positioning and navigation equipment such as pipeline above ground markers, can calculate position and orientation with 6 degrees of freedom: x, y, z, and pitch, roll, and yaw. IMU launched within the pipeline via in-line inspection tool trains, can be used to develop accurate three-dimensional geometry of the pipelines they inspect. This information can be used to confirm the geometry of the pipeline (i.e. degree of roping, bend angle, bend radius, and other abnormalities observed within the generated centerline from the inspection based on conventional construction practices). Therefore, the application of IMU technology within pipeline design and integrity work can be a useful tool in providing the necessary input information which can support ongoing studies such as verification of maximum operating thermal differentials which can be imposed on a pipeline to remain compliant with governing pipeline codes, and/or the information can be used to perform gap analysis studies with other integrity records (alignment sheets, as-built pipe tallies), or to support other pipeline integrity evaluations. When IMU data is processed with mathematical techniques essential information from IMU data can be obtained such as bend angle, bend radius, and degree of installed curvature. A case study showing the results of the application of processed IMU data for as-built evaluation is presented and its use to help support a variety of decision making is discussed. The IMU data is a key data input when constructing detailed finite element models for on-going stress analysis studies.