PSI - Issue 44

Mariano Ciucci et al. / Procedia Structural Integrity 44 (2023) 347–354 Mariano Ciucci et al. / Structural Integrity Procedia 00 (2022) 000–000

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4.4.1. Technology, functional and operating characteristics The FBG/FSI fiber optic sensors are multifunctional transducers capable of detecting vibrations, deformations, temperatures, length variations, dynamic pressures, 2D and 3D geometry variations and accelerations at high sampling rate, with high accuracy and over a long distance, along a single-mode optical fiber interfaced with the structure or component to be monitored. Thanks to the metrological, operational and functional characteristics in line with the needs of reliability, accuracy, durability, multifunctionality and remote control required by the high-quality standards of industrial metrology, the FBG / FSI fiber optic sensors find wide application in various sectors such as that of transport, infrastructure, mining, Oil & Gas and renewable energy. The FBG / FSI fiber optic sensors are totally immune to electromagnetic interference, are ATEX certified, do not require a power supply, as they have limited weight and dimensions, they are considered non-invasive measurement systems. The material with which they are made makes them chemically inert: they are in fact insensitive to oxidative and erosive phenomena, guaranteeing correct functioning in environmental and operating conditions even if immersed in a liquid. They allow the transmission of measurement data over long distances with low signal loss. Measuring chains that are kilometers long can be easily structured, with basic wiring and extremely lean control hardware (Fig. 5). They are ideal devices for measuring deformations and temperature variations with a high resolution: 40 for deformations and 0.01 ° C for temperatures. They can be installed inside parts and structures in composite material directly during the rolling phase. Standard FBG sensors can work immersed in a liquid and in environments with temperatures between -180 ° C and 400 ° C. Finally, it is taken into account that these technologies do not require calibration and are certified to last up to 25 years without the need for recalibration. Fiber optics sensors key operational and functional characteristics are: • FBG/FSI sensors thermal range from -180°C to 600°C • Strain sensitivity: +/- 0,4 microstrain • Thermal sensitvity: +/- 0,01 °C • Optical sensors with NO insertion error [125 µm external diameter] • Total EMI immunity. Fiber optics FBG/FSI sensors are chemically inert, insensitive to oxidation and erosion • Stable embedded sensors array installation inside carbon fiber components • Compact and lightweight interrogator/data logging unit • Up to 200 kHz sampling rate for each installed optical sensor • No periodic calibration needed • Competitive solution in terms of installation and usability of the data respect to measurement systems based on resistance strain gauges and thermocouples • Fiber Optics Sensors interrogator units can be manufactured according to ATEX hazardous environments standards. 5. Active protection systems These systems do not control any process but actually come into play when it is not possible to control a process through normal means. They are usually installed as protective measures(see Fig. 6). The smart implementation of active protection systems requires them to be connected to a smart net of communication and activation systems. Eventually, active protection systems may be installed for the shut-off or for safety condition of plants also for earthquakes. The design and maintenance of active protection systems present a special challenge created by the infrequent need for these systems to act; on the other hand, they must be available to operate whenever needed.

Fig. 6. active protection systems.