FBG Fiber Optic Sensors for Non-Invasive Pipe Wall Thickness Measurement
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Solution Overview
Problem
Existing methods for monitoring corrosion in pipes, such as those using fiber optics, do not effectively employ Fiber Bragg Grating (FBG) sensors for uniform and localized wall thickness measurement, and are often invasive or susceptible to mechanical shock and corrosive fluids.
Innovation Solution
A system utilizing FBG fiber optic sensors embedded in a composite material mounted on the exterior of pipes to measure strain, which is then converted into wall thickness measurements using a light source, light sensor, and digital processor, allowing for non-invasive and accurate determination of wall thickness and metal loss features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If external fiber optic sensors are mounted on pipe exterior, then non-invasive measurement is achieved, but sensor protection from mechanical shock and corrosive fluids becomes problematic
Solution Approach 1:
The patent applies composite materials by embedding the fiber optic sensor within a composite mounting material that is adhered to the pipe exterior. This composite material serves as a protective enclosure, shielding the sensor from mechanical shock and corrosive fluids while enabling non-invasive strain measurement through the composite structure.
Solution Approach 2:
The composite mounting material acts as an intermediary between the fiber optic sensor and the pipe exterior. It transfers strain from the pipe to the sensor while simultaneously protecting the sensor from harmful environmental factors, thus mediating both measurement and protection functions.
2Reliability
If FBG sensors are embedded in composite material, then sensor protection is improved, but mounting complexity increases
Solution Approach 1:
The patent merges the sensor protection function and the mounting function into a single integrated composite structure. The fiber optic sensor is embedded within the composite material during its formation, eliminating the need for separate protective housings and simplifying the overall mounting process despite the multi-functional requirement.
3Measurement precision
If multiple FBG sensors are used for localized measurements, then measurement precision is improved, but signal processing complexity increases
Solution Approach 1:
The patent segments the measurement function by using multiple discrete FBG sensors at different locations along the pipe. Each sensor provides localized strain measurement data, and the system processes signals from each sensor independently to determine wall thickness at specific positions, enabling precise localized characterization of corrosion features.
Solution Approach 2:
The patent applies local quality by positioning FBG sensors at specific locations where localized corrosion is suspected or where uniform wall thickness measurement is required. Each sensor provides specialized measurement data for its specific location, allowing the system to characterize both uniform and localized corrosion features with appropriate measurement precision at each position.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides high-resolution, non-invasive, and durable measurements of pipe wall strain and thickness, resistant to mechanical shock and corrosive fluids, enabling effective monitoring of corrosion and metal loss without compromising signal quality.
Implementation Method 1
A number of applications employ fiber optics to monitor the strain generated within reinforced concrete due to build up of corrosion products. Others relate to the impact of corrosion on metal coated fibers or fibers doped with compounds that fluoresce in the presence of a target chemical species.
Implementation Method 2
A light source and a light sensor are coupled to the optical fiber. The light sensor converts light reflected back from the FBGs into electrical signals that a digital processor converts into strain measurements.
Data Source
AI summary
A system and method are provided for determining wall thickness of a structure such as a metallic pressurized pipe. The system includes an optical fiber having a plurality of Fiber Bragg Gratings (FBGs), and a mounting for securing the FBGs over discrete portions of the exterior surface of the pipe such that strain in the pressurized pipe wall is transmitted to the FBGs. The system further includes a light source and a light sensor coupled to an end of the optical fiber. The light sensor converts light reflected back from the FBGs into electrical signals that a digital processor converts into strain measurements. The FBGs are mounted around portions of the pipe expected to have significant metal loss as well as portions of the pipe expected to have negligible metal loss. The method includes at least one of comparing relative strains at locations with negligible metal loss to those with significant metal loss to accurately determine the thickness of the wall with metal loss; compensating for temperature effects by considering relative strains at areas of the pipe with and without metal loss; and measuring axial strain on the pipe with one or more of the FBGs to correct for at least one of bending and torsion effects on hoop strain.