Abstract
Measurements of the rate of corrosion in concrete sewers need to take into consideration the humidity in the environment, and, thus, its accurate measurement becomes critically important. Introducing a novel approach to do so, tailored fiber Bragg grating (FBG)-based humidity sensors have been evaluated in situ to examine their durability, time response, and stability when used in measurements over an extended period of time under the aggressive gaseous environment of a gravity sewer, experiencing high levels of both humidity and hydrogen sulfide gas. The critical humidity monitoring element in the probe is based on a moisture-sensitive polyimide coated FBG, using the calibrated and reproducible peak wavelength shift in response to moisture variation, in this case operationally in the sewer. To optimize the device for this environment, two different designs of the probe assembly were configured using different material, thus aiming to provide durability in the harsh environment in the long term. The aim of the probe design evaluated was to achieve good sensitivity to humidity as well as to protect the sensing elements from the aggressive environment and which had rendered ineffective the electrical sensors placed in the sewer and used for cross comparison. A full evaluation of the packaged sensors in situ was undertaken over a period of five months, during which the sensors were constantly subjected to high, but varying levels of humidity and wet hydrogen sulfide gas. The results are highly encouraging, showing superior performance of the configured fiber optic sensors used over a conventional electrical sensor when the results of the cross-comparison study of the performance were evaluated. These outcomes show a promising future for optical fiber sensors to be employed for measurement of humidity in the long term in harsh environmental applications such as this.
Highlights
ACCELERATED corrosion in the major infrastructure assets worldwide is an important problem which must be tackled rapidly in order to avoid long term damage and expensive replacement strategies
All of the qualities observed from the optical fiber sensors are paramount to achieve sensitive, accurate and effective data in order to assess the sewer corrosion condition, allow for better maintenance and reduce cost to both operator and consumer as well as be readily configurable in an optical fiber sensor network
The stage of the research work will focus on the physical durability of the sensor system: it will be important to analyze the material properties of the specific PI grade used under the influence of H2S and see whether this could be improved by implementing the material or using another material
Summary
ACCELERATED corrosion in the major infrastructure assets worldwide is an important problem which must be tackled rapidly in order to avoid long term damage and expensive replacement strategies. Fiber optic-based sensor systems, as discussed below, play a full role in providing a response to the needs that such a choice provides, possessing a number of advantages over conventional electrical/electronic sensors in general: such as immunity to electromagnetic interference, chemical inertness, light weight and low mass (which facilitates ‘drying’ after use), a multiplexing capability, high thermal stability and remote sensing ability. All of these make them well suited to both general and remote sensing for this application. The data obtained are reviewed in detail and the conclusions that could be reached discussed, together with recommendations for further work that arise from the study
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
