Strain monitoring of drilling riser in deepwater based on fiber Bragg gratings

It is very important to monitor the lateral and axial strains of drilling riser for evaluation its health in deepwater. An optical fiber strain sensing system based on optical fiber Bragg gratings (FBGs) used for monitoring the strain of drilling riser is presented. The optical fiber strain sensors are made by embedding FBGs into thin columned fiber reinforced polymer which protect FBGs from seawater corrosion. Four optical fiber strain sensors are installed parallel to the riser axis and arranged at 90° angles around the riser by a home-made metal belt, at the same time, twelve resistance strain gauges are pasted near the sensors around the drilling riser at 30° angles as reference sensors. A scaled drilling riser about 1 meter long and 0.245m diameter is pressed in the lateral and axial direction in the range of 0-400KN, the experimental results show that the relative error between optical fiber strain sensors and resistance strain gauges is less than 6%.