Abstract

Safety diagnosis of large structures such as storage tanks in industrial facilities is very important. In this study, we have proposed a method for monitoring damage in a composite storage tank using a fiber optic time-differential Brillouin optical correlation domain analysis (TD-BOCDA) sensor. A simulated damage with a thickness of 3 mm ground out from 12 mm with an area of 500 × 400 mm was applied to the inner surface of the storage tank, and the Brillouin frequency distribution was measured for 1 day to analyze the change in strain distribution over the damaged area. The maximum strain over the damaged area in the absence of sunlight was ∼92 με, which was similar to the elastically calculated value of the composite storage tank, even when considering the error due to temperature difference on the measurement day. The spatial resolution of the TD-BOCDA used in the experiment was 2 cm, and the width of the actual simulated damage was 50 cm. The full width at half maximum (FWHM) of strain variation for the three sensing fibers passing over this area was measured as 48, 50, and 64 cm, respectively, which are very similar to the width of the actual simulated damage. We expect to monitor the stiffness reduction damage of the composite storage tank in the field by measuring the strain distribution using the TD-BOCDA sensor system.