Real time Continuous Structural Integrity Monitoring of Flexible Risers with Optical Fiber Sensors

摘要

Even though the armor layers play a major role in the structural integrity of flexible risers, operators and service providers worldwide are still in search of reliable inspection or monitoring techniques capable of detecting the presence of cracks or other defects in the metallic wires that compose the internal and external armor layers of the pipe. In the present contribution, we report the effort undertaken by Petrobras in order to face this challenge. Novel inspection and monitoring systems, based on acoustic emission, measurement of residual magnetic field, optical sensing, or employing visual monitoring cameras, are being developed and tested. Among these techniques, the one relying on optical fiber sensors has provided the best results so far. The use of fiber Bragg grating sensors for directly measuring strains in each wire of the external traction layer offers an accurate and reliable real-time, continuous monitoring technique, providing the operator with valuable information and early warning if any deviation from the expected wire's structural behavior is detected. The paper describes the technique and presents results from full scale laboratory tests as well as from the first field trial conducted in an offshore platform operated by Petrobras in Campos Basin.