Characterisation of metal loss defects from magnetic flux leakage signals with discrete wavelet transform

A result of a research partnership between Catholic University of Rio de Janeiro – PUC-Rio, PETROBRAS and PIPEWAY is presented: The development of an innovative sensor head for high resolution MFL Pigs, the GMD sensor, Geometric Magnetic and Discriminator. This head makes high resolution magnetic pipeline readings using the MFL - Magnetic Flux Leakage technique, with the addition of geometric readings and the outside/inside defects discriminations. This technique makes possible, with only one crown of GMD sensors, the caliper, metal loss and outside/inside discrimination pipeline inspection. Technical aspects of the development, e.g.: the construction details of the sensor, evaluation tests and laboratory results are also presented.

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The Design of a Mechanical Damage Inspection Tool Using Dual Field Magnetic Flux Leakage Technology

Journal of Pressure Vessel Technology ◽

10.1115/1.1989349 ◽

2005 ◽

Vol 127 (3) ◽

pp. 274-283 ◽

Cited By ~ 2

Author(s):

J. Bruce Nestleroth ◽

Richard J. Davis

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

High Magnetic Field ◽

Mechanical Damage ◽

Magnetic Flux Leakage ◽

Metal Loss ◽

Unexpected Result ◽

Lower Field ◽

Study Results ◽

Flux Leakage

This paper describes the design of a new magnetic flux leakage (MFL) inspection tool that performs an inline inspection to detect and characterize both metal loss and mechanical damage defects. An inspection tool that couples mechanical damage assessment as part of a routine corrosion inspection is expected to have considerably better prospects for application in the pipeline industry than a tool that complicates existing procedures. The design is based on study results that show it is feasible to detect and assess mechanical damage by applying a low magnetic field level in addition to the high magnetic field employed by most inspection tools. Nearly all commercially available MFL tools use high magnetic fields to detect and size metal loss such as corrosion. A lower field than is commonly applied for detecting metal loss is appropriate for detecting mechanical damage, such as the metallurgical changes caused by impacts from excavation equipment. The lower field is needed to counter the saturation effect of the high magnetic field, which masks and diminishes important components of the signal associated with mechanical damage. Finite element modeling was used in the design effort and the results have shown that a single magnetizer with three poles is the most effective design. Furthermore, it was found that for the three-pole system the high magnetization pole must be in the center, which was an unexpected result. The three-pole design has mechanical advantages, including a magnetic null in the backing bar, which enables installation of a pivot point for articulation of the tool through bends and restrictions. This design was prototyped and tested at Battelle’s Pipeline Simulation Facility (West Jefferson, OH). The signals were nearly identical to results acquired with a single magnetizer reconfigured between tests to attain the appropriate high and low field levels.

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Oblique Field Magnetic Flux Leakage Inline Survey Tool: Implementation and Results

2010 8th International Pipeline Conference, Volume 1 ◽

10.1115/ipc2010-31313 ◽

2010 ◽

Author(s):

James Simek ◽

Jed Ludlow ◽

Phil Tisovec

Keyword(s):

Experimental Data ◽

Magnetic Flux ◽

Full Range ◽

Magnetic Flux Leakage ◽

Metal Loss ◽

Data Sets ◽

Data Set ◽

Survey Tool ◽

Oblique Field ◽

Flux Leakage

InLine Inspection (ILI) tools using the magnetic flux leakage (MFL) technique are the most common type used for performing metal loss surveys worldwide. Based upon the very robust and proven magnetic flux leakage technique, these tools have been shown to operate reliably in the extremely harsh environments of transmission pipelines. In addition to metal loss, MFL tools are capable of identifying a broad range of pipeline features. Most MFL surveys to date have used tools employing axially oriented magnetizers, capable of detecting and quantifying many categories of volumetric metal loss features. For certain classes of axially oriented features, MFL tools using axially oriented fields have encountered difficulty in detection and subsequent quantification. To address features in these categories, tools employing circumferential or transversely oriented fields have been designed and placed into service, enabling enhanced detection and sizing for axially oriented features. In most cases, multiple surveys are required, as current tools do not incorporate the ability to collect both data sets concurrently. Applying the magnetic field in an oblique direction will enable detection of axially oriented features and may be used simultaneously with an axially oriented tool. Referencing previous research in adapting circumferential or transverse designs for inline service, the concept of an oblique field magnetizer will be presented. Models developed demonstrating the technique are discussed, shown with experimental data supporting the concept. Efforts involved in the implementation of an oblique magnetizer, including magnetic models for field profiles used to determine magnetizer configurations and sensor locations are presented. Experimental results are provided detailing the response of the system to a full range of metal loss features, supplementing modeling in an effort to determine the effects of variables introduced by magnetic property and velocity induced differences. Included in the experimental data results are extremely narrow axially oriented features, many of which are not detected or identified within the axial data set. Experimental and field verification results for detection accuracies will be described in comparison to an axial field tool.

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Characterization of Mechanical Damage Through Use of the Tri-Axial Magnetic Flux Leakage Technology

Volume 2: Integrity Management; Poster Session; Student Paper Competition ◽

10.1115/ipc2006-10454 ◽

2006 ◽

Author(s):

Vanessa Co ◽

Scott Ironside ◽

Chuck Ellis ◽

Garrett Wilkie

Keyword(s):

Magnetic Flux ◽

Mechanical Damage ◽

Magnetic Flux Leakage ◽

Metal Loss ◽

Field Investigations ◽

Non Destructive ◽

Flux Leakage

Management of mechanical damage is an issue that many pipeline operators are facing. This paper presents a method to characterize dents based on the analysis of the BJ Vectra Magnetic Flux Leakage (MFL) tool signals. This is an approach that predicts the severity of mechanical damage by identifying the presence of some key elements such as gouging, cracking, and metal loss within dents as well as multiple dents and wrinkles. Enbridge Pipelines Inc. worked with BJ Services to enhance the knowledge that can be gained from MFL tool signals by defining tool signal subtleties in dents. This additional characterization provides information about the existence of gouging, metal loss, and cracking. This has been accomplished through detailed studies of the ILI data and follow-up field investigations, which validate the predictions. One of the key learnings has been that the radial and circumferential components of the MFL Vectra tool are highly important in the characterization and classification of mechanical damage. Non-destructive examination has verified that predictions in detecting the presence of gouging and cracking (and other defects within dents based on tool signals) have been accurate.

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Magnetic Flux Leakage Image Enhancement using Bidimensional Empirical Mode Decomposition with Wavelet Transform Method in Oil Pipeline Nondestructive Evaluation

Journal of Magnetics ◽

10.4283/jmag.2019.24.3.423 ◽

2019 ◽

Vol 24 (3) ◽

pp. 423-428

Author(s):

Liang Chen ◽

Jingcheng Li ◽

Yakai Zeng ◽

Yongqiang Chen ◽

Wei Liang

Keyword(s):

Wavelet Transform ◽

Magnetic Flux ◽

Nondestructive Evaluation ◽

Image Enhancement ◽

Magnetic Flux Leakage ◽

Transform Method ◽

Oil Pipeline ◽

Mode Decomposition ◽

Bidimensional Empirical Mode Decomposition ◽

Flux Leakage

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API 579 Level 3 Assessment of Dents Using High-Resolution ILI Data

Volume 2: Structures, Safety and Reliability ◽

10.1115/omae2011-50349 ◽

2011 ◽

Cited By ~ 1

Author(s):

Chas Jandu ◽

Mike Taylor ◽

Suji Narikotte

Keyword(s):

High Resolution ◽

Magnetic Flux ◽

Single Channel ◽

Mechanical Damage ◽

Magnetic Flux Leakage ◽

Metal Loss ◽

Operating Pressure ◽

Data Set ◽

Level 3 ◽

Flux Leakage

In-line Inspection (ILI) surveys are periodically performed to determine the condition of the pipeline. Typical ILI surveys involve Magnetic Flux Leakage primarily to determine metal loss and simple single channel Calliper surveys to determine any signs of geometry imperfections. Additional surveys such as high-resolution multi-channel Calliper deformation tools are occasionally used to accurately record imperfections to enable a more accurate assessment of the integrity of the pipeline containing the imperfection. Such tools have had limited employment, and therefore little experience exists of using the data obtainable for the detailed assessment of defects. This paper presents a study of such a case. As part of an In-line Inspection (ILI) of an offshore pipeline, a high-resolution deformation survey recorded numerous dent anomalies which had potentially resulted from a single dragged anchor incident before the pipeline was trenched. This data set was correlated to Magnetic Flux Leakage inspection data to confirm external mechanical damage. Pipeline sections having anomalies that were either found close to girth welds, or had associated corrosion defects were automatically selected for repair. The remaining anomalies were assessed in order to determine their acceptability for the maximum allowable operating pressure using the approaches detailed in API-579. Due to the sharp nature of some of the dents, elastic-plastic finite element analyses (FEA) were performed using denting profiles generated from the calliper data of the ILI run. API-579 level 3 assessments were then carried out using the FEA results. This paper details the high-resolution deformation tool findings and the approach used in order to assess the fitness-for-purpose of the pipe with the recorded anomalies.

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