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Tech Note:

This page is updated regularly as new reports are released. Newest items are listed first.
Please contact us at  techinfo@fox-tek.com if a technical area is not listed, or the report is not available on line.

    “Sensor System Monitors Corrosion Damage”

W.D. Morison


Reprinted from the September 2006 edition of Materials Performance


“Primer on FT Sensors”
FOX-TEK Report 117-041008

“Long Gage-Length Fiber Optic Sensors For Monitoring Pipeline Integrity”

R.C. Tennyson, W.D. Morison

Smart Structures and Materials and NDE for Health Monitoring and Diagnostics Conference
San Diego, CA

Abstract

This paper describes the use of FOX-TEK's long gage-length FT fiber optic sensors (FOS) for monitoring the integrity of pipelines and refinery components. Site assessment protocols and installation methods are described, in addition to the different FOS configurations required to monitor component integrity. It is shown how sensor information can also be used for process control, involving the monitoring of line temperature, pressure, and pipe wall thinning. Models are described that allow the operator to interpret field data to detect corrosion rates, pipe bending, movement and buckling.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.


    “Fiber-optic Monitoring Focuses on Bending, Corrosion”

R.C. Tennyson, W.D. Morison, T. Miesner


Reprinted with revisions to format, from the February 20, 2006 edition of OIL & GAS JOURNAL

Copyright 2006 by PennWell Corporation


“Solving Common Corrosion Problems with Non-Intrusive Fiber Optic Corrosion and Process Monitoring Sensors”

W. D. Morison, T. Cherpillod, I. Al-Taie, S. Mutairi

3rd Middle East Nondestructive Testing Conference & Exhibition,
Manama, Bahrain, 27-30 November, 2005

Abstract

Some of the most common corrosion problems in refineries can be addressed with the help of non-intrusive corrosion and process monitoring tools. One of such tool is the long gage length FT fiber-optic sensor system which, in addition to monitoring wall loss, can also monitor pressure and temperature profiles. Being non-intrusive, the sensors can be installed without shutting down the equipment. For crude unit overhead piping suffering HCl condensation corrosion, the operators can rely on the wall loss measurements and temperature profile to adjust process parameters to minimize condensation or to inject optimum amounts of neutralizers or filming amines. For ammonium bi-sulphide corrosion, the changes in temperature profiles can be used to determine the amounts and frequency of wash water injection. In other equipment, which is affected by turbulence-enhanced erosion/corrosion, fiber optic sensors can be used to measure wall loss in real time to increase safety and to allow more efficient planning of turnarounds.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.


“Monitoring Bridge Structures Using Long Gage-Length Fiber Optic Sensors”

R.C.Tennyson, N.Banthia, E.Rivera, S.Huffman, I.Sturrock

Caltrans Bridge Research Conference 2005
Sacramento, CA, 31 October - 1 November, 2005

Abstract

Fiber optic sensors (FOS) provide many advantages over traditional electrical-based sensors, primarily because they are non- conductive and immune to electromagnetic interference. Since they operate on light waves, lead length and sensor location relative to high EMF sources are not an issue. FOS are capable of measuring structural displacements, strains, pressure, vibration and temperature. There are three types of sensor systems on the market, each of which operates on a different principal.

"Point" sensors such as fiber Bragg gratings (FBG) measure a change in the reflection wavelength due to straining of the grating. This wavelength shift is directly related to the refractive index of the grating, its grid spacing and the applied strain. Fabry Perot sensors measure a change in a gap length between opposing optical fibers mounted in a capillary tube. The change in gap length is directly related to the applied strain as well. Both sensors are used for static and dynamic measurements over small gage lengths (~ 1cm).

They are similar in size to electrical-based resistance strain gages and are used to measure local strains/temperatures.

Distributed sensors such as Raman and Brillouin systems operate on the concept of measuring a change in light wave scattering at different frequencies due to displacements within an optical fiber. Raman scattering is used primarily to measure temperature distributions along an optical fiber at pre-defined gage lengths that can vary from one to several meters in length. Brillouin scattering can measure thermal as well as mechanical strains along the fiber over comparable gage lengths. These distributed sensing systems employ only a single fiber, and can interrogate the fiber over distances as great as 30 km.

Long gage-length FOS measure average displacement over gage lengths that can vary between 10cm ~ 100m long. These displacements are converted to average strains by dividing the displacement by the sensor's gage length. They have an advantage over "point" sensors since they are not significantly affected by local stress concentrations. Accuracy of these sensors is based on the monitoring instrument (FT 3405, manufactured by FOX-TEK) that has a displacement resolution of about 5 microns. Thus the strain resolution is equal to "5/sensor gage length (m) = microstrain".

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.


“Pipeline Integrity Assessment Using Fiber Optic Sensors”

R.C.Tennyson, W.D.Morison, T.Miesner

Proceedings of the ASCE Pipeline 2005 Conference
Houston, TX, August 21-24, 2005
Paper #9149

Abstract

This paper describes the application of fiber optic sensors (FOS) to integrity assessment of pipelines. FOS provide a solution for monitoring time-dependent defects including internal corrosion, external corrosion, and stress corrosion cracking. They can also monitor pipe movement, pipe stress, and buckling strains due to slope instability, ground settling, and currents acting on exposed river and stream crossings. FOS are an ideal component of direct assessment protocols – improving safety while also significantly lowering costs. Both laboratory and field test data are presented to demonstrate the capability of FOS.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.


“Application of Fiber Optic Sensors for Impact Damage Detection on Spacecraft”

R.C. Tennyson, W.D. Morison, E. Christiansen

5th International Workshop on Structural Health Monitoring, held at Stanford University, Stanford, September 2005.

Abstract

A description of the design and application of a new fiber optic impact damage detection system for spacecraft. Two fiber optic sensor configurations are explored, one employing optical fibers woven into an adhesive mesh bonded to a thin polymer membrane, and the other containing optical fibers woven into a shield fabric. Results are presented based on hypervelocity impact (HVI) tests conducted at the NASA Johnson Space Center’s light gas gun facility. The purpose of this system is to provide a real-time warning of an impact penetration, its location on the spacecraft and the damage size.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.


“Monitoring pipeline integrity using fiber optic sensors”
RC Tennyson; WD Morison; T. Cherpillod
NACE Corrosion 2005

Abstract

Fiber optic sensing is a new technology with applications to monitoring pipeline integrity. Because they are non-electrical, immune to electromagnetic interference and have low line losses, they are ideal sensors for monitoring pipelines over long distances. This paper presents result on the application of FT fiber optic sensors for monitoring pipeline corrosion, including internal wall thinning and external stress corrosion crack (SCC) growth.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.

“Fiber optic structural health monitoring system for pipelines”
RC Tennyson; WD Morison
ISIS SHM - Sept 22-23, 2004

Abstract

The detection and monitoring of pipeline corrosion remains a major problem in the oil and gas industry. Corrosion is the leading cause of pipeline failures, either in the form of external stress corrosion cracking (SCC) or internal wall thinning. This paper describes a new technology for monitoring the growth of SCC and internal corrosion, based on "FT" fiber optic sensing (FOS). Results are presented demonstrating in field tests that a structural health monitoring (SHM) system can reliably detect internal erosion/corrosion of a pipe. In addition, FT coil sensors are shown to be capable of monitoring stress corrosion cracks as they penetrate the pipe's wall. Essential to the SHM system is the inclusion of structural models that incorporate the sensor data and convert that to useful engineering parameters such as residual wall thickness and crack depth.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.

“Application of Brillouin fiber optic sensors to monitor pipeline integrity”
RC Tennyson; WD Morison; B. Colpitts; A. Brown.
IPC - 2004 - Calgary AB.

Abstract

This paper describes the application of Brillouin fiber optic sensors to monitor pipeline integrity in terms of third party intrusion, leak detection and ground movement. Brillouin sensors provide a means for continuous monitoring of strain and temperature distributions over distances of about 25 km. The optical fibers can be bonded to the pipeline or buried in close proximity to the pipe. Third party intrusion is detected by strain anomalies caused by vehicles or persons in close proximity to the sensor located at some depth below the surface. Leaks from oil or gas pipelines are detected by thermal anomalies in the temperature profiles. Pipeline movement can also be detected by using this system for existing and new pipeline installations. Applications include northern pipelines, high consequence areas, river crossings and fault lines.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.

“Safety monitoring technique for steel beams using "FT" fiber optic sensors”
HS Park, HS Jung, JM Baek
ISIS Paper - September 2004

Abstract

Fiber optic sensors have been considered as one of the major sensors for structural health monitoring due to their durability and independence from EMI. However, most existing fiber optic sensors used for this purpose can only cover a relatively small range of structural members resulting in many difficulties when determining safety of large scale structures using these point sensors. Utilization of the long gauge "FT" sensors in health monitoring systems can overcome the inherent drawbacks of point based sensors. In this paper, a new safety evaluation technique using average strains from FT sensors is suggested and results are presented from experiments conducted on a standard W-shape steel beam.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.

“Fiber optic sensors for operational efficiency in the oil, gas and petrochemical industries”
W.D. Morison, R.C. Tennyson
CHEMINDIX 2004 - Bahrain September 2004

Abstract

The operational efficiency of the oil, gas and petrochemical (OGP) industries can be improved by minimizing the duration of shutdowns for repair or replacement components that have been damaged by corrosion, erosion, or crack growth. Real-time knowledge of the state of health of these components allows the operator of the facility to replace only those components that would not function safely until the next scheduled shutdown. Unfortunately, conventional sensor technology cannot provide this capability. This paper summarizes the results of several studies involving the application of the "FT" fiber optic sensor system that can function in harsh industrial environments and provide real-time measurements of wall thickness loss, crack growth and operational parameters including internal pressure and temperature.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.

“Application of fiber optic sensors to monitor pipeline corrosion”
R.C. Tennyson, W.D. Morison, T. Cherpillod, W. Revie
NACE Conference on Corrosion 2004, paper # 04739, New Orleans, April 2004

Abstract

A new technology has been developed and field tested to monitor pipeline corrosion. This technology utilizes "FT" fiber optic sensors (FOS) bonded to the exterior surface of the pipe. The sensors measure changes in the strain field which occur as the pipe wall deteriorates with time. These sensors vary in configuration, depending on the application. Local stress corrosion crack (SCC) growth can be monitored using a novel fiber optic "coil" sensor, whereas general internal wall corrosion/erosion can be detected with hoop or spiral wrap sensors which can extend over distances of 100 m or more. This paper presents both laboratory and field test results on crack growth and internal corrosion/erosion of pipelines. FOS technology coupled with structural modeling software provide a means by which continuous, remote monitoring of pipeline corrosion is possible.

Copyright restrictions prevent the full paper from being made available online. If you would like a complete copy, please contact FOX-TEK.