Experimental flow loop study on fiber Bragg grating (FBG) sensor placement for monitoring severe internal metal loss in wrapped pipelines

The safe operation of oil and gas pipelines relies on reliable detection and monitoring of internal metal loss. This study numerically and experimentally investigates the performance of fiber Bragg grating (FBG) sensors for monitoring severe localized internal metal loss in a pipeline section, with a focus on optimal sensor placement. A defective metallic pipe segment with a wall thickness of 10 mm and localized internal metal loss of 8.3 mm was evaluated under simulated operational conditions in a flow loop setup. FBG sensors were tested and installed in three configurations: directly on the bare pipe, at the interface between the pipe and a composite wrap, and on the external surface of the wrap. An additional nearby FBG served as a reference to account for temperature and flow/pressure-induced variations. Results show that the sensor placed at the interface, bonded to the bare pipe, and protected by the wrap, exhibited the highest strain sensitivity due to metal loss. This demonstrates the potential of FBG-based sensing as a non-intrusive, real-time solution for monitoring pipeline integrity.