External Corrosion Detection of Oil Pipelines Using Fiber Optics

High-sensitivity fiber Bragg grating strain sensor of the substrate type

Strain measurement has important applications in mechanical engineering, civil engineering, aerospace, earthquake monitoring, and other fields. Aiming at the problem of low sensitivity of existing fiber Bragg grating (FBG) strain sensors, a high-sensitivity FBG strain sensor of the substrate type with a sensitization structure is proposed. The sensitivity of the sensor is analyzed theoretically, the sensor is simulated by Solidworks and ANSYS software, and the structural parameters are optimized. According to the simulation results, the real sensor is developed, and the strain test system is built to test the performance of the sensor. The results show that the strain sensitivity of the sensor is 3.21p m/µε, which is about 2.7 times that of the bare FBG strain sensor, which is basically in line with the theoretical value. The fitting linear correlation coefficient is 0.9999, and the repeatability error is 3.9%FS. The research results provide a reference for developing the same type of sensors and further improving the sensitivity of fiber strain sensors.

Cost-Effective Corrosion Detection Sensor for Above-Ground Oil and Gas Flowlines

A sensor for monitoring of the external corrosion of small-diameter aboveground oil and gas pipelines (called flowlines), based on fiber-optic strain sensing, is proposed. The working principle of our proposed sensor relies on the use of a pre-stressed sacrificial structure made of the same material as the pipeline and monitoring changes in the measured strain that occur due to deterioration caused by corrosion to the structure. We present the development of analytical equations that allow designing the sensor structure to achieve the desired strain values. The analysis was verified using commercial finite element analysis (FEA) software. The proposed sensor is simple and cost-effective and can be easily manufactured. It can be deployed on existing overground pipelines without any modification to the pipeline structure. While it is not capable of measuring the corrosion rate continuously, it can provide a measurement of the average corrosion rate over the life span of its sacrificial metal structure.

Recent Advances in Nondestructive Method and Assessment of Corrosion Undercoating in Carbon-Steel Pipelines

Carbon-steel pipelines have mostly been utilized in the oil and gas (OG) industry owing to their strength and cost-effectiveness. However, the detection of corrosion under coating poses challenges for nondestructive (ND) pipeline monitoring techniques. One of the challenges is inaccessibility because of the pipeline structure, which leads to undetected corrosion, which possibly leads to catastrophic failure. The drawbacks of the existing ND methods for corrosion monitoring increase the need for novel frameworks in feature extraction, detection, and characterization of corrosion. This study begins with the explanations of the various types of corrosion in the carbon-steel pipeline in the OG industry and its prevention methods. A review of critical sensors integrated with various current ND corrosion monitoring systems is then presented. The importance of acoustic emission (AE) techniques over other ND methods is explained. AE data preprocessing methods are discussed. Several AE-based corrosion detection, prediction, and reliability assessment models for online pipeline condition monitoring are then highlighted. Finally, a discussion with future perspectives on corrosion monitoring followed by the significance and advantages of the emerging AE-based ND monitoring techniques is presented. The trends and identified issues are summarized with several recommendations for improvement in the OG industry.

Sensing System Based on FBG for Corrosion Monitoring in Metallic Structures

As corrosion has slow development, its detection at an early age could be an alternative for reducing costs of structural rehabilitation. Therefore, the employment of structural health monitoring (SHM) systems, sensing configurations collecting data over time allowing for observing changes in the properties of the materials and damage emergence, for monitoring corrosion can be a good strategy to measure the damage and to decide the better moment for intervention. Nonetheless, the current corrosion sensor technology and the high costs of the sensing system implementation are limiting this application in the field. In this work, an optical fiber Bragg grating (FBG)-based sensing system is proposed for monitoring the thickness loss of a 1020 carbon steel metal plate subjected to controlled corrosion. The natural frequency of the plate was collected as a function of the corrosion time over 3744 h. To validate the experimental results, ultrasound measures and electrochemical tests were also carried out under similar conditions. The experimental results show adequate reliability, indicating the suitable functionality of the proposed system for monitoring the thickness loss caused by corrosion in metallic structures, in comparison with traditional methods, as ultrasonic and electrochemical measures.

Investigating the effects of environment, corrosion degree, and distribution of corrosive microbial communities on service-life of refined oil pipelines

Although the potential corrosive microbial communities of the refined oil pipelines can cause pipeline failure which directly threatens on soil and water environment, few studies have been published in this field. Therefore, the long-distance on-site internal corrosion detection and high-throughput sequencing techniques were employed in this study to investigate the distribution shifts of the corrosive microbial communities on the inner wall of a refined oil pipeline and its impact on the internal corrosion. The microorganisms colonizing on the inner wall of the pipeline showed significant distribution differences between the axial direction of the relative elevation and radial direction of the cross-section. On the inner wall, the high diversity and the abundance of the corrosive microbial communities induced serious microbiologically influenced corrosion (MIC), while the chemical corrosion and the synergy of the corrosive microbial communities accelerated the internal corrosion of the refined oil pipeline. A corrosion zone model has been proposed, which divides the pipeline cross-section into the sediment, the water-oil interface, the gas-oil interface, and the oil fully immersed zones. Therefore, the relationships between the environment, corrosion degree, and distribution characteristics of the corrosive microbial communities in the pipeline were analyzed. This research exhibited the importance of the distribution characteristics of the corrosive microorganisms on the inner wall of the refined oil pipelines. Its internal corrosion behavior was accurately explored, while providing a basis for controlling the corrosive microbial communities.

Biocompatible and Biodegradable Polymer Optical Fiber for Biomedical Application: A Review

This article discusses recent advances in biocompatible and biodegradable polymer optical fiber (POF) for medical applications. First, the POF material and its optical properties are summarized. Then, several common optical fiber fabrication methods are thoroughly discussed. Following that, clinical applications of biocompatible and biodegradable POFs are discussed, including optogenetics, biosensing, drug delivery, and neural recording. Following that, biomedical applications expanded the specific functionalization of the material or fiber design. Different research or clinical applications necessitate the use of different equipment to achieve the desired results. Finally, the difficulty of implanting flexible fiber varies with its flexibility. We present our article in a clear and logical manner that will be useful to researchers seeking a broad perspective on the proposed topic. Overall, the content provides a comprehensive overview of biocompatible and biodegradable POFs, including previous breakthroughs, as well as recent advancements. Biodegradable optical fibers have numerous applications, opening up new avenues in biomedicine.

Concept of an In-Plane Displacement Sensor Based on Grating Interferometry with a Stepwise Change of Sensitivity

Grating Interferometry, known in the relevant literature as the High Sensitivity Moiré Interferometry, is a method for in-plane displacement and strain measurement. The sensitivity of this method depends on the spatial frequency of the diffraction grating attached to the object under test. For typical specimen grating, with high spatial frequency of 1200 lines per mm, the basic sensitivity is 0.417 µm per fringe. A concept of in-plane displacement sensor based on Grating Interferometry with a stepwise change in sensitivity is presented. It is realized by using the specimen grating with lower spatial frequency. In this case, the grating has more higher diffraction orders and by selecting them appropriately, the sensitivity (chosen from 1.25 μm, 0.625 μm, or 0.417 μm) and the resulting measurement range (chosen from about 600 μm, 300 μm, or 200 μm) can be adjusted to the requirements of a given experiment. A special method of filtration is required in this case. Achromatic configuration with illumination grating was chosen due to its low sensitivity to vibration.

Study of a Long-Gauge FBG Strain Sensor with Enhanced Sensitivity and Its Application in Structural Monitoring

A long-gauge fiber Bragg grating (FBG) strain sensor with enhanced strain sensitivity is proposed, which is encapsulated with two T-shaped metal blocks. Its fabrication method is described briefly, and the strain sensitivity can be flexibly adjusted through changing its packaging method. A series of experiments are carried out to study the packaging and its sensing properties. The experimental results show that the strain and temperature sensitivity coefficient of the sensor are three times larger than the common FBG sensors. The linearity coefficients of the FBG sensor are larger than 0.999, and the relative error of the repeatability of all sensor samples is less than 1%. Through the stability test on the actual bridge, it is revealed that the long-term stability of the sensor is excellent, and the maximum error is less than 1.5%. In addition, the proposed FBG strain sensors are used to conduct a shear strengthening experiment on a reinforced concrete (RC) beam to verify its working performance. The experimental results show that the strain change and crack propagation of the RC beam are well monitored by the sensors during the loading process.