In Line Inspection of Axial Strain, Technique, Case Studies and Best Practices
Proceedings Publication Date
Axial strain imposed on pipelines due to landslide loading is a major integrity concern in areas of instability for pipeline operators. While many threats including bending strain can be monitored by inline inspection, axial strain has required localized strain monitoring at known high-risk sites. Currently, (Inertial Measurement Unit) IMU inline inspections allow for the delimitation of areas of localized bending strains and run-to-run movement analysis, but do not detect either tensile or compressive loading. Applying sensor technology used for stress measurement in other industries, an in-line inspection tool has been developed specifically to detect and monitor areas of increased axial strain. Operators now can measure axial strain in pipelines without the need to expose the pipeline for the installation of surficial pipe monitoring systems (primarily strain gauges) or destructive testing. The key advantage of the new technology is that current methods of stress/strain measurement (including the installation of strain gauges) only detect strain changes going forward from the date of installation at a location of potential hazard. This in-line inspection technique measures total strain at the time of inspection. This paper gives a brief introduction to the technique and the technology implementation. Axial strain inspection case studies are reviewed for pipelines that have been subjected to landslides moving parallel and perpendicular to the pipeline. In addition, the paper presents an operator’s experience with the new tool measurements, recommending best practices to utilize the axial strain data from an operator’s point of view.