A realistic implementation of an all-fiber CO2 sensor, using 74 cm of hollow core photonic crystal fiber (HC-PCF) as the cavity for light/gas interaction, has been implemented. It is based on CO2 absorbance in the 2 µm region. The working range is from 2% to 100% CO2 concentration at 1 atm total pressure and the response time obtained was 10 min. Depending on the concentration level, the sensor operates at one of three different wavelengths (2003.5 nm, 1997.0 nm and 1954.5 nm) to maintain a high sensitivity across all the working range.
Thorough the last two decades, oil and gas reservoirs discovered and developed in deep and ultra deep waters have continuously posed challenges to petroleum exploration and production activities in offshore basins. Maintaining optimum flow rates of oil and gas from subsea wellheads to surface processing facilities demands new technological solutions for petroleum companies operating in such frontiers. Integrity assurance of structures, equipment, and flow lines plays a major role in maximizing offshore production systems availability while at the same time keeping safety, operational, and environmental risks at minimum levels. In this scenario, implementation of permanent health monitoring solutions must take into account the environment of oil and gas production facilities, where installations in hazardous classified areas require explosion and fire-proof instrumentation. In this context, optical fiber sensors offer an attractive alternative to electrical sensing technologies, which, until now, have been the primary choice by maintenance personnel at offshore production units.
This paper aims to report the results of an experimental study on the application of piezoelectric dynamic strain sensors for crack length measurement in fracture mechanics specimens. The performance of the piezoelectric sensors was assessed through fatigue crack propagation tests in compact tension (CT) specimens. Sensors of polarized polyvinilidene fluoride polymer (PVDF) were bonded to the back face of CT specimens, in the same manner as the electrical resistance strain gages installed for crack length measurement in the back face strain technique. The results showed that, mainly due to its high sensitivity to strain, the use of piezoelectric materials as dynamic strain sensors can contribute to the experimental investigation in the field of fracture mechanics.
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