Testing of a Dual Field Magnetic Flux Leakage (MFL) Inspection Tool for Detecting and Characterizing Mechanical Damage Features

2008 ◽  
Author(s):  
Alex Rubinshteyn ◽  
Steffen Paeper ◽  
Bruce Nestleroth
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Residual Stresses ◽  
High Field ◽  
Mechanical Damage ◽  
Magnetic Flux Leakage ◽  
Low Field ◽  
Field Unit ◽  
Low Magnetic Field ◽  
Flux Leakage

Battelle has developed dual field magnetic flux leakage (MFL) technology for the detection and characterization of mechanical damage to pipelines. The basic principle involves the use of a high magnetic field between 140 and 180 Oersted (11.1 to 14.3 kA/m) and the use of a low magnetic field between 50 and 70 Oersted (4 to 5.6 kA/m). At high magnetic field levels, the flux leakage signal is primarily influenced by changes in the geometry of a pipe wall. At low magnetic field levels, the MFL signal is due to residual stresses and metallurgical changes as well as geometry changes to the pipe caused by mechanical damage and wall thinning. A decoupling signal processing method developed by Battelle is used to isolate the portion of the mechanical damage signals due to metallurgical damage and residual stresses, which allows the characteristics of a dent-gouge feature to be more clearly differentiated. The decoupling method involves first scaling down the high field signal to the level of the low field signal, and then subtracting it from the low field signal. This produces a decoupled signal that is primarily influenced by the residual stresses and metallurgical changes caused by mechanical damage. Rosen has developed a tool to test the dual field technology and is evaluating tool performance by running the tool in a 30 inch diameter pipeline segment. The tool itself is composed of three separate modules coupled together: a high field unit downstream of a low field unit which is downstream of a caliper arm unit that is used to detect and characterize reductions in the internal diameter. The general and magnetic design of the tool, along with the scaling algorithm is discussed. Results from a pull test in a pipe section with dents whose geometry has been independently characterized are also discussed. This work is partially funded by the U.S. Department of Transportation, Pipeline and Hazardous Materials Safety administration (DOT PHMSA) and the Pipeline Research Council International, Inc. (PRCI).

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

2005 ◽  
Vol 127 (3) ◽  
pp. 274-283 ◽  
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.

ANSYS Simulation Technology of Pipeline Magnetic Flux Leakage Inspection

2013 ◽  
Vol 718-720 ◽  
pp. 1000-1005
Author(s):  
Li Jian Yang ◽  
Sen Lin Zhang ◽  
Song Wei Gao
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Electromagnetic Field ◽  
Magnetic Flux ◽  
Oil And Gas ◽  
Gas Pipeline ◽  
Magnetic Flux Leakage ◽  
Field Calculation ◽  
Inspection Method ◽  
Flux Leakage

In order to solve the need of the oil and gas pipeline defect quantification in the real-time online defecting, magnetic flux leakage inspection method was applied to oil and gas pipeline inspection. According to the basic theory of the electromagnetic field, finite element solution of electromagnetic field and ANSYS electromagnetic field calculation theory, using the function of ANSYS 's simulation and calculation for magnetic field, three-dimensional finite element model of the oil and gas pipeline defect was built up. Through simulating, the relationship between defect signal and defect size was found, the optimal distance of the hall sensor lift-off value was verified, the best magnetization of leakage magnetic field was discussed, and various factors to influence the magnetic flux leakage signal is analyzed.

The 3D Magnetic Field Analysis of Excitation Unit of Drill Pipe MFL Testing Based on ANSYS

2013 ◽  
Vol 694-697 ◽  
pp. 1179-1182
Author(s):  
Yi Lai Ma ◽  
Li Lin ◽  
Kai Wen Jiang ◽  
Xu Lin Zhao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Drill Pipe ◽  
Magnetic Flux Leakage ◽  
Field Analysis ◽  
Ansys Software ◽  
Magnetic Field Analysis ◽  
The Cost ◽  
The Magnetic Field ◽  
Flux Leakage

Magnetic flux leakage is one type of electromagnetic nondestructive testing (NDT) which is widely utilized in the testing the integrity of drill pipe in the field. In this paper, the 3D model of excitation unit is completely built and analyzed by ANSYS software. The magnetic field of drill pipe in the combination of full excitation device is showed by ANSYS software instead of the physic experiments which increases the efficiency tremendously and decreases the cost and achieves the anticipated desire. It is considered that this technique can provide the theoretical basis of drill pipe excitation device and the magnetic flux leakage testing of drill pipe.

Finite Element Analysis and Research on Corrosion Defect of Tank Floor

2016 ◽  
Vol 853 ◽  
pp. 514-518
Author(s):  
Zhi Jun Yang ◽  
De Shu Chen ◽  
Liang Chen ◽  
Yu Zhuo Liu ◽  
Ran An ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Magnetic Flux ◽  
Magnetic Flux Leakage ◽  
Bottom Plate ◽  
Element Analysis ◽  
Corrosion Defect ◽  
Leakage Magnetic Field ◽  
Leakage Field ◽  
Flux Leakage

Storage tank is an essential vessel in petrochemical industry, and the corrosion of tank is an important reason for the safety hazard. The corrosion of tank bottom plate is more serious than the tank wall, and it is not easy to check and repair, when damaged to a certain extent it will cause the leakage of the media, then lead to waste of energy, environmental pollution, at the same time it will cause a major accident. Magnetic flux leakage testing is widely used in the field of tank floor inspection with the advantages of fast scanning speed, accurate results and so on. In this paper, the finite element simulation and analysis of the corrosion defect leakage magnetic field is used to obtain the data, and the characteristic of the leakage magnetic field is extracted. The effect of defect depth and width and shape on the magnetic flux leakage field is studied, and the distribution curve of the magnetic flux leakage field is obtained.

HIGH VERSUS LOW FIELD VISCOMETRIC CHARACTERIZATION OF BIDISPERSE MR FLUIDS

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4922-4928 ◽  
Author(s):  
G. T. NGATU ◽  
N. M. WERELEY
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
High Field ◽  
Magnetic Flux Density ◽  
Flow Curves ◽  
Bingham Plastic ◽  
Low Field ◽  
Mr Fluids ◽  
Low Magnetic Field

Our bidisperse magnetorheological fluids are suspensions of micron (2-10μm) and nanometer (~40nm) scale magnetic iron particles in silicone or hydraulic oil. Earlier studies were conducted to determine the yield stress of these fluids at low magnetic field induction. These studies have shown the absence of saturation yield stress implying the possibility of a higher yield stress by increasing the applied field. In this study, three different bidisperse MR fluids were investigated to determine the maximum available yield stress that can be obtained at or near saturation magnetic flux density. The iron loading in the fluids varied from 50% to 80% by weight. Two types of MR cells, a low field and a high field cells, were used for the investigation. Using a parallel disc rheometer alternatively equipped with one of the two MR cells, the flow curves of the MR fluids were obtained and their yield stress determined. The yield stress of the MR fluids as a function of applied magnetic field was identified using the Bingham-Plastic constitutive model. Results show that the high field cell (maximum 1 Tesla) was able to measure shear stress up to saturation, whereas the low field cell (maximum 0.26 Tesla) could not.

Management of Pipeline Dents and Mechanical Damage in Gas Pipelines

2006 ◽  
Author(s):  
David J. Warman ◽  
Dennis Johnston ◽  
John D. Mackenzie ◽  
Steve Rapp ◽  
Bob Travers
Keyword(s):  
High Resolution ◽  
Magnetic Flux ◽  
Mechanical Damage ◽  
Management Plan ◽  
Magnetic Flux Leakage ◽  
Pipeline System ◽  
Channel Geometry ◽  
Channel Deformation ◽  
Integrity Management ◽  
Flux Leakage

This paper describes an approach used by Duke Energy Gas Transmission (DEGT) to manage dents and mechanical damage as part of its overall Integrity Management Plan (IMP). The approach provides guidance in the process for evaluating deformation anomalies that are detected by high resolution magnetic flux leakage (HR-MFL) and multi-channel geometry in-line inspection tools, the process to determine which deformations will be selected for excavation, the process to conduct pipeline field excavations, assessments, and repairs for pipeline integrity purposes. This approach was developed, tested and fully implemented during pipeline integrity work over a two year program involving over 1,100 miles of HR-MFL and 900 miles of geometry in-line inspection. Integration of data from high resolution ILI tools (HR-MFL and multi-channel deformation tools) was used to identify and characterize dents and mechanical damage in the pipeline system. From subsequent field assessments and correlation with ILI results, the processes were refined and field procedures developed. The new guidance provided in the 2003 edition of ASME B31.8 was used as the governing assessment criteria.

Finite Element Analysis of Magnetization Reversal Effect Based on Ferromagnetic Specimens

2014 ◽  
Vol 620 ◽  
pp. 127-132
Author(s):  
Xiao Wen Xi ◽  
Shang Kun Ren ◽  
Li Hua Yuan
Keyword(s):  
Magnetic Field ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Magnetic Flux ◽  
Magnetization Reversal ◽  
Tensile Load ◽  
Magnetic Flux Leakage ◽  
Element Analysis ◽  
The Magnetic Field ◽  
Flux Leakage

Using large finite element analysis (FEA) software ANSYS, the stress-magnetization effect on 20# steel specimens with different shape notches is simulated under the geomagnetic field and tensile load. With the stimulation, the magnetic flux leakage fields at certain positions of the surface specimen were measured. Through analysis the relationship between the magnetic flux leakage fields of certain points with tensile stress, the results showed that the magnetic field value at certain positions of specimen surface first decreases and then increases along with the increase of stress, which is called magnetization reversal phenomenon; Different gaps and different positions of the specimen show different magnetization reversal rules; By measuring the maximal variation of the magnetic field value △Hmax at certain positions of the surface specimen and by analyzing its change law, we can roughly estimate specimen stress size and distribution regularity of stress. Moreover, this article also discusses the effect of lifts-off of the probe on the law of stress magnetization.

Understanding Magnetic Flux Leakage Signals From Dents

2006 ◽  
Author(s):  
Lynann Clapham ◽  
Vijay Babbar ◽  
Alex Rubinshteyn
Keyword(s):  
Magnetic Flux ◽  
Pipe Wall ◽  
Experimental Studies ◽  
Mechanical Damage ◽  
Magnetic Behaviour ◽  
Magnetic Flux Leakage ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Stress Relieving ◽  
Flux Leakage

The Magnetic Flux Leakage (MFL) technique is sensitive both to pipe wall geometry and pipe wall stresses, therefore MFL inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, the combined influence of stress and geometry make MFL signal interpretation difficult for a number of reasons: 1) the MFL signal from mechanical damage is a superposition of geometrical and stress effects, 2) the stress distribution around a mechanically damaged region is very complex, consisting of plastic deformation and residual (elastic) stresses, 3) the effect of stress on magnetic behaviour is not well understood. Accurate magnetic models that can incorporate both stress and geometry effects are essential in order to understand MFL signals from dents. This paper reports on work where FEA magnetic modeling is combined with experimental studies to better understand dents from MFL signals. In experimental studies, mechanical damage was simulated using a tool and die press to produce dents of varying aspect ratios (1:1, 2:1, 4:1), orientations (axial, circumferential) and depths (3–8 mm) in plate samples. MFL measurements were made before and after selective stress-relieving heat treatments. These annealing treatments enabled the stress and geometry components of the MFL signal to be separated. Geometry and stress ‘peaks’ tend in most cases to overlap — however stress features are most prominent in the dent rim region and geometry peaks over central region. In general the geometry signal scales directly with depth. The stress scales less significantly with depth. As a result deep dents will display a ‘geometry’ signature while in shallow dents the stress signature will dominate. In the finite element analysis work, stress was incorporated by modifying the magnetic permeability in the residual stress regions of the modeled dent. Both stress and geometry contributions to the MFL signal were examined separately. Despite using a number of simplifying assumptions, the modeled results matched the experimental results very closely, and were used to aid in interpretation of the MFL signals.

scholarly journals Detection of Mechanical Damage Using the Magnetic Flux Leakage Technique

2004 ◽  
Author(s):  
Lynann Clapham ◽  
Vijay Babbar ◽  
James Byrne
Keyword(s):  
Magnetic Flux ◽  
Experimental Studies ◽  
Mechanical Damage ◽  
Central Peak ◽  
Magnetic Flux Leakage ◽  
Element Analysis ◽  
Stress Effects ◽  
Stress Relieving ◽  
Stress Dependent ◽  
Flux Leakage

Since magnetism is strongly stress dependent, Magnetic Flux Leakage (MFL) inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, MFL application to mechanical damage detection faces hurdles which make signal interpretation problematic: 1) the MFL signal is a superposition of geometrical and stress effects, 2) the stress distribution around a mechanically damaged region is very complex, consisting of plastic deformation and residual (elastic) stresses, 3) the effect of stress on magnetic behaviour is not well understood. This paper summarizes recent results of experimental and modeling studies of MFL signals resulting from mechanical damage. In experimental studies, mechanical damage was simulated using a tool and die press to produce dents of varying depths in plate samples. Radial component MFL measurements were made before and after selective stress-relieving heat treatments. These annealing treatments enabled the stress and geometry components of the MFL signal to be separated. Geometry and stress effects generate separate MFL peaks — the geometry effects lead to central peak regions while the stress effects produce ‘shoulder’ peaks. In general the geometry peaks tend to scale with depth, while the shoulder peaks remain approximately constant. This implies that deep dents will display a ‘geometry’ signature while shallow or rerounded dents will have a stress signature. Finally, the influence of other parameters such as flux density and topside/bottomside inspection was also quantified. In the finite element analysis work, stress was incorporated by modifying the magnetic permeability in the residual stress regions of the modeled dent. Both stress and geometry contributions to the MFL signal were examined separately. Despite using a number of simplifying assumptions, the modeled results matched the experimental results very closely, and were used to aid in interpretation of the MFL signals.

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