A Compensation Method for Spiral Error of Pipeline Bending Strain In-Line Inspection

The in-line inspection tool with an inertia measurement unit (IMU tool) is used to measure the centerline coordinate and bending strain for the oil and gas pipeline. In order to prevent the partial wear during inspection, the tool is used to install the supporting wheel at a regular angle to rotate circumferentially. However, the spiral errors are produced during the course of inspection and thus affect the accuracy of centerline and bending strain. To improve the inspection precision and reduce the incidences of spiral error, this article presents a spiral error compensation method not only to improve the inspection precision of centerline mapping, but also to calibrate and compensate for the bending strain of pipeline. The field pull through test was carried out in a section of oil pipeline, and the results showed that the spiral error could practically be eliminated, with the maximum repetition error reducing from 0.17 to 0.06 m, and the precision of pipeline bending strain descending effectively from 0.04 to 0.02 %. The proposed method proved to be effective for improving the inspection accuracy of pipeline displacement and strain inspection.