巴西专利BR112016026957B1 methods of detecting defects in ferromagnetic materials

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专利摘要:
SYSTEM AND METHOD OF MEASUREMENT OF DEFECTS IN FERROMAGNETIC MATERIALS. The present invention relates to defects in ferromagnetic materials that are detected and characterized by analyzing the magnetic fields of items to discover portions of the magnetic fields that differ in the characteristic forms of residual magnetic fields generated by non-defective portions of the items. The portions of the magnetic fields that differ in characteristic shapes correspond to locations of defects. Residual magnetic fields correspond to portions of items far from defects. Defect characterization may include a volume of material lost due to each defect and/or the width and/or depth of each defect.
公开号:BR112016026957B1
申请号:R112016026957-8
申请日:2015-05-15
公开日:2021-05-11
发明作者:Almir D. Davis；William J. Trinkle；Donald Gustafson；Philip S. Babcock Iv；Richard T. Berthold
申请人:The Charles Stark Draper Laboratory, Inc；
IPC主号:

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CROSS REFERENCE TO RELATED ORDERS
[001] This application claims the benefit of US Provisional Patent Application No. 61/994,961, filed May 18, 2014, entitled "System and Method of Measuring Defects in Ferromagnetic Materials", the entire contents of which are hereby incorporated by reference. here, for all purposes. TECHNICAL FIELD
[002] The present invention relates to a defect detection in ferromagnetic materials and, more particularly, to a defect detection in ferromagnetic materials using a magnetometer. BACKGROUND TECHNIQUE
[003] Ferromagnetic materials, such as iron, nickel, steel and other materials, are used for making many items such as tubes, profiles and hulls of oceanic vessels. As used herein, a "ferromagnetic material" includes both a ferromagnetic and a ferrimagnetic material. In many cases, these materials are subject to corrosion and/or erosion. As used here, corrosion means a loss of material as a result of a chemical reaction, most commonly oxidation. As used herein, an erosion means a loss of material as a result of a mechanical process, such as abrasion. For example, sand produced in an oil or gas well can cause abrasion inside a pipeline carrying oil or gas from the well. A loss of material due to corrosion and/or erosion is collectively referred to herein as a "defect". As used herein, the term defect also includes a crack or a void or an inclusion of foreign matter, such as might occur during manufacture or later. If allowed to occur beyond a critical point, corrosion or erosion can compromise the structural integrity of an item, possibly resulting in a catastrophic failure, such as an oil spill, a building collapse, or a ship sinking.
[004] Various apparatus and methods have been used in the prior art in attempts to detect defects in ferromagnetic materials and items made from ferromagnetic materials. Some of these apparatus and methods require the removal of insulation and the etching of corrosion inhibiting surface treatments to gain direct access to a surface of the ferromagnetic material. In some cases, the surface must be polished to create a pristine interface to a sensor or a wave propagation from the sensor. These steps are costly, time consuming and often compromise thermal insulation and/or surface treatments.
[005] All prior art apparatus and methods for detecting defects in ferromagnetic materials known to the inventors involve introducing energy into the material. For example, acoustic sensors send a sound wave to the material and measure the signal that returns. Guided wave and topographic sensors similarly send electromagnetic waves into the material and detect reflections or wave transport times. In a different view of printing energy for the item being measured, Rohrback Cosaco Systems, Inc. produces a line of sand erosion detection probes under the trade name "Quicksand". These probes do not directly measure the erosion of pipes, etc. Instead, these probes are a sacrifice in that they detect erosion of portions of the probes themselves. Systems based on these probes assume that tubes and other items erode at approximately the same rate as the sacrificial portions of the probes. Furthermore, the probes rely on fluid flow through the tube, therefore requiring energy to be introduced into the tube in the form of a fluid flow. These systems can detect erosion only within a pipe. These systems cannot detect defects elsewhere, such as inside the pipe wall or on an outer surface of a pipe, nor can they infer the condition of a pipe due to erosion before the sensor is in place.
[006] Some prior art apparatus and methods involve magnetometry in attempts to detect defects in ferromagnetic materials. For example, U.S. Patent Nos. 8,542,127 and 8,447,532, both to Valerian Goroshevskiy, et al., disclose the use of an inverse magnetorestrictive Villari effect. This inverse magneto-restrictive Villari effect involves changes in the magnetic susceptibility of the material under an applied mechanical stress. If a tube has a defect, the magnetic susceptibility of the tube when the tube material is mechanically stressed, for example when the tube is pressurized, will be different from when the tube is not mechanically stressed. Goroshevskiy's patents are based on detecting this change in magnetic susceptibility as a pressure in the tube changes. Thus, energy must be introduced into the tube in the form of pressurizing the bottom of the tube. Some items, such as tubes, remain unused, and therefore not pressurized, for periods of time during which defects can develop. Other structures, such as ship hulls or structural elements, do not lend themselves to a known pressurization cycle. However, without pressurization, Goroshevskiy's devices and methods cannot detect these defects. Furthermore, Goroshevskiy can only determine a defect location along the length of a pipe; Goroshevskiy cannot determine the location of the defect circumferentially around the tube. SUMMARY OF MODALITIES
[007] An embodiment of the present invention provides a system for detecting defects in a ferromagnetic material. The system includes a plurality of magnetometers. A plurality of magnetometers are arranged around a surface of the ferromagnetic material. A plurality of magnetometers detect a magnetic field generated by the ferromagnetic material. The plurality of magnetometers generate magnetic field data, based on the detected magnetic field. Each magnetometer of the plurality of magnetometers is fixed in position relative to the ferromagnetic material. The system also includes a magnetic field mapper. The magnetic field mapper generates two-dimensional map data points from the magnetic field data. Each data point corresponds to a respective location on the surface of the ferromagnetic material. Each data point represents an intensity of the magnetic field detected near the location. "Close" in this context means close enough that a defect location can be determined in both the x and y directions, that is, longitudinally along the ferromagnetic material and laterally through the material. In some modes, close means 5 to 10 inches (12.7 to 25.4 cm). The system also includes a pattern combiner. The pattern combiner identifies, on the map, a plurality of data points that conform to a predefined spatial pattern of magnetic field strength. The pattern combiner extracts a location close to the surface of the ferromagnetic material that corresponds to the plurality of data points. The extracted location is a defect location.
[008] The system can also include a defect size estimator. The defect size estimator estimates a volume of material missing from the ferromagnetic material at the location close to the surface of the ferromagnetic material. The missing volume estimate is based on the amplitude of a trace represented by data in the plurality of data points.
[009] The defect size estimator can estimate an area of missing material, based on the length of two spatial directions of a trace represented by data in the plurality of data points.
[0010] The defect size estimator can estimate a depth of missing material, based on the estimated volume of missing material and the length in two spatial directions of a trace represented by data in the plurality of data points.
[0011] The system may also include a residual magnetic field strength calculator. The residual magnetic field strength calculator determines the magnitude of the magnetic field generated by the ferromagnetic material at a location far from the location near the surface of the ferromagnetic material. The amplitude of the magnetic field is based on at least one of the map data points. The system can also include a defect size estimator. The defect size estimator estimates a volume of material missing from the ferromagnetic material at the location close to the surface of the ferromagnetic material. The volume estimation is made according to the data amplitude in the plurality of data points and the magnitude of the magnetic field generated by the ferromagnetic material at the location distant from the location near the surface of the ferromagnetic material.
[0012] The defect size estimator can estimate an area of missing material, based on the length in two spatial directions of a trace represented by the data in the plurality of data points.
[0013] The defect size estimator can estimate a depth of missing material, based on the estimated volume of missing material and the length in two spatial directions of a trace represented by the data in the plurality of data points.
[0014] Each magnetometer of the plurality of magnetometers may include three orthogonally oriented magnetometers. Each data point on the map can represent the strength of the magnetic field detected in each of the three orthogonal directions. The pattern combiner can identify, for each of the three orthogonal directions, a plurality of data points that conform to a predefined spatial pattern of magnetic field strength and a location near the surface of the ferromagnetic material that corresponds to the plurality of data points. The pattern combiner in this way can identify three locations close to the surface of the ferromagnetic material. The system can also include a combiner. The combiner can calculate a refined location close to the surface of the ferromagnetic material from the three identified locations and extract the refined location.
[0015] The pattern combiner can calculate a plurality of spatial derivative values from the map data points. The pattern combiner can identify the plurality of data points that conform to the predefined spatial pattern of magnetic field strength from the plurality of spatial derivative values.
[0016] The plurality of data points that conform to the predefined spatial pattern of magnetic field strength may correspond to a loss of a portion of the ferromagnetic material due to corrosion or erosion.
[0017] The plurality of data points that conform to the pre-defined spatial pattern of magnetic field strength corresponds to a crack in the ferromagnetic material.
[0018] Another embodiment of the present invention provides a method for detecting defects in a ferromagnetic material. The method includes detecting a magnetic field generated by the ferromagnetic material. The data points of a two-dimensional map are generated by the ferromagnetic material. The data points of a two-dimensional map are generated from the detected magnetic field. Each data point corresponds to a respective location on the surface of the ferromagnetic material. Each data point represents the strength of the magnetic field detected near the location. On the two-dimensional map, a plurality of data points are identified. The plurality of data points conform to a predefined spatial pattern of magnetic field strength. A location close to the surface of the ferromagnetic material is extracted. The location corresponds to the plurality of data points. The location corresponds to a defect.
[0019] Magnetic field detection may include arranging a plurality of magnetometers around a surface of the ferromagnetic material. Each magnetometer of the plurality of magnetometers is fixed in position relative to the ferromagnetic material.
[0020] Magnetic field detection may include physically scanning the ferromagnetic material with at least one magnetometer by moving at least one magnetometer relative to the ferromagnetic material.
[0021] The movement of at least one ferromagnetic material relative to the ferromagnetic material may include arranging a one-dimensional array of at least two magnetometers along an oriented shape substantially perpendicular to a geometric axis of the ferromagnetic material. The one-dimensional arrangement of at least two magnetometers can be moved along the geometric axis of the ferromagnetic material.
[0022] Optionally, a volume of material missing from the ferromagnetic material at the location close to the surface of the ferromagnetic material can be estimated. The estimate can be based on the amplitude of a trace represented by data in the plurality of data points.
[0023] Optionally, the amplitude of the magnetic field generated by the ferromagnetic material at a location distant from the location close to the surface of the ferromagnetic material can be determined, based on at least one of the map data points. A volume of material missing from the ferromagnetic material at the location close to the surface of the ferromagnetic material can be estimated, according to the data amplitude in the plurality of data points and the magnitude of the magnetic field generated by the ferromagnetic material at a location distant from the nearby location. of the surface of the ferromagnetic material.
[0024] Optionally, an area of missing material can be estimated. The estimate can be based on the length in two spatial directions of a trace represented by data in the plurality of data points.
[0025] A circumference depth of the missing material can be estimated. The estimate can be based on the estimated volume of missing material and length in two spatial directions of a trace represented by data in the plurality of data points.
[0026] Magnetic field detection may include magnetic field detection with a plurality of magnetometers. Each magnetometer of the plurality of magnetometers may include three orthogonally oriented magnetometers. The generation of the data points can include generating the data points so that each data point on the map represents the strength of the magnetic field detected in each of three orthogonal directions. Identifying the plurality of data points that conform to a predefined spatial pattern may include, for each of the three orthogonal directions, identifying a plurality of data points that conform to a predefined spatial pattern of intensity. magnetic field and a location near the surface of the ferromagnetic material that corresponds to the plurality of data points, thereby identifying three locations near the surface of the ferromagnetic material. Furthermore, a refined location close to the surface of the ferromagnetic material can be calculated from the three identified locations. Location extraction can include refined location.
[0027] A plurality of spatial derivative values can be calculated from the map data points. Identifying the plurality of data points that conform to a predefined spatial pattern may include identifying a plurality of data points that conform to the predefined spatial pattern of magnetic field strength from the plurality of values of spatial derivative.
[0028] Identifying the plurality of data points that conform to a predefined spatial pattern may include identifying a plurality of data points that correspond to a loss of a portion of the ferromagnetic material due to corrosion or erosion.
[0029] Identifying the plurality of data points that conform to a predefined spatial pattern may include identifying a plurality of data points that correspond to a crack in the ferromagnetic material.
[0030] Yet another embodiment of the present invention provides a computer program product for detecting defects in a ferromagnetic material. The computer program product includes a non-transient computer readable medium. A computer-readable program code is stored in the medium. The computer readable program code includes a detection module, a data point generator module, a fault identifier module and a fault location extraction module.
[0031] The detection module receives magnetic field data from a plurality of magnetometers arranged around a surface of the ferromagnetic material. A plurality of magnetometers detect a magnetic field generated by the ferromagnetic material. The plurality of magnetometers also generate magnetic field data. Magnetic field data is based on the detected magnetic field. Each magnetometer of the plurality of magnetometers is fixed in position relative to the ferromagnetic material.
[0032] The data point generator module generates data points from a two-dimensional map from the detected magnetic field. Each data point corresponds to a respective location on the surface of the ferromagnetic material. Each data point represents an intensity of the magnetic field detected near the location.
[0033] The defect identifier module identifies, in the two-dimensional map, a plurality of data points that conform to a predefined spatial pattern of magnetic field strength. The defect location extraction module extracts a location close to the surface of the ferromagnetic material that corresponds to the plurality of data points. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] The invention will be more fully understood with reference to the Detailed Description of Specific Modalities in conjunction with the Drawings, of which:
[0035] Figure 1 is a perspective view of a hypothetical tube and a cross-sectional view of a portion of the tube as known in the prior art.
[0036] Figure 2 is a perspective view of a hypothetical curved tube as known in the prior art.
[0037] Figure 3 schematically illustrates a magnetic field produced by a hypothetical magnetic dipole, as known in the prior art.
[0038] Figure 4 contains graphs of hypothetical example intensities Bx, By and Bz detected by a magnetometer along the three axes along a line in figure 3.
[0039] Figure 5 schematically illustrates a hypothetical plate of ferromagnetic material, as known in the prior art.
[0040] Figure 6 schematically illustrates the plate of Figure 5 as many small aligned magnetic dipoles, as interpreted in accordance with the embodiments of the present invention.
[0041] Figure 7 schematically illustrates the plate of figure 5 with a defect on its surface.
[0042] Figure 8 schematically illustrates a hypothetical tube, showing an artifact of helical thickness from its fabrication, as known in the prior art.
[0043] Figure 9 schematically illustrates the tube of Figure 8 after being conceptually cut and unwound, as known in the prior art.
[0044] Figure 10 contains a graph of a component of a magnetic field around a real tube having a defect in its outer surface, according to an embodiment of the present invention.
[0045] Figure 11 is a side view of a magnetometric sensor unit, according to an embodiment of the present invention.
[0046] Figure 12 schematically illustrates a set of magnetometric sensor units affixed to a tube, according to an embodiment of the present invention.
[0047] Figure 13 schematically illustrates a set of magnetometric sensor units affixed to a tube, according to an embodiment of the present invention.
[0048] Figure 14 is a schematic perspective view of an array of magnetometric sensors arranged circumferentially around a tube, according to an embodiment of the present invention.
[0049] Figure 15 is a schematic perspective view of a pair of circuit boards, carrying magnetometers, as in each element of the magnetometric sensor array of Figure 14, according to an embodiment of the present invention.
[0050] Figure 16 is a schematic perspective view of magnetometric sensor rings arranged around a tube, according to an embodiment of the present invention.
[0051] Figures 17 and 18 include graphs of magnetometric data along two respective dimensions of an actual tube, according to an embodiment of the present invention.
[0052] Figures 19 and 20 contain graphs of derivatives calculated from the graphs of figures 17 and 18, respectively, according to an embodiment of the present invention.
[0053] Figure 21 is a graph of magnetic field strength for three simulated defects, all of the same diameter but different depths, according to an embodiment of the present invention.
[0054] Figure 22 is a graph of magnetic field strength for three simulated defects, all having the same depth but different diameters, according to an embodiment of the present invention.
[0055] Figure 23 is a graph of magnetic field strength along an x-axis near a defect in a tube, according to an embodiment of the present invention.
[0056] Figure 24 is a graph of magnetic field strength along a z-axis near a defect in a tube, according to an embodiment of the present invention.
[0057] Figure 25 is a graph of the magnetic field strength of Figure 23, after a normalization, according to an embodiment of the present invention.
[0058] Figure 26 is a schematic perspective illustration of a tube and a standoff between a detector and a tube defect, according to an embodiment of the present invention.
[0059] Figure 27 is a graph illustrating differences in signal strength from a defect inside a tube and a signal strength from a defect in an outside of the tube, according to an embodiment of the present invention .
[0060] Figure 28 is a surface graph of a result of a subtraction, showing an axis of the magnetic field, according to a temporal analysis, according to an embodiment of the present invention.
[0061] Figures 29 and 30 are schematic perspective views of apparatus for implementing physical scans of items, according to respective embodiments of the present invention.
[0062] Figure 31 is a schematic block diagram of a remote magnetometric sensor in wireless communication with a base station, according to an embodiment of the present invention. DETAILED DESCRIPTION OF SPECIFIC MODALITIES
[0063] The embodiments of the present invention allow the detection of defects in items containing ferromagnetic materials without requiring energy to be introduced into the materials and without necessarily removing thermal insulation, surface treatments and the like of the materials or items. The ferromagnetic materials in the items generate magnetic fields. The embodiments of the present invention detect and characterize defects in items by analyzing the magnetic fields of the items to find portions of the magnetic fields that differ in characteristic ways from residual magnetic fields generated by non-defective portions of the items. The portions of the magnetic fields that differ in characteristic shapes correspond to locations of defects. Residual magnetic fields correspond to portions of items far from defects. Defect characterization may include a volume of material lost due to each defect and/or the width and/or depth of each defect. A challenge to any magnetometric approach is that the item's intrinsic residual magnetic field is typically inhomogeneous, reflective of material and manufacturing variations across the item. A key challenge of these methods is to separate the defect's magnetic "signature" from the intrinsic "noise" in the item's residual field. Overview
[0064] In some modalities, a two-dimensional array of magnetometric sensors is arranged parallel to an external surface of an item to be analyzed. The array of magnetometric sensors collects data allowing the creation of a two-dimensional map of magnetometric data (magnetic field map). In this context, a "carpet" of magnetometric sensors wrapped around a circular cross-section tube or other non-flat item is considered to be two-dimensional.
[0065] In some embodiments, an item is physically scanned along one dimension by a one-dimensional array of magnetometric sensors, thereby creating a two-dimensional map of magnetometric data. In some embodiments, an item is scanned, spirally rotated, or otherwise scanned along more than one dimension by a single magnetometric sensor or a small group of magnetometric sensors to create a two-dimensional map of magnetometric data.
[0066] The ferromagnetic material in the item generates a magnetic field. Magnetic fields are vector quantities characterized by strength and direction. The magnetometric data map (magnetic field map) represents the strength of the magnetic field at each of many points above the surface of the item. A magnetic field map can identify one, two, or three components of the three-dimensional magnetic field strength vector.
[0067] In some embodiments, magnetometric data is essentially searched for any one of several predefined patterns (shapes). A region in which the strength of the magnetic field or any of the components of the three-dimensional magnetic field varies spatially according to one of the predefined patterns corresponds to a location of a defect. According to one of these predefined patterns, along a straight line, the magnetic field starts at the residual level and then increases in intensity to a peak, relative to the residual level, then decreases in intensity to a valley below of the residual level, and then returns to the residual level, somewhat similar to the shape of a sine wave cycle.
[0068] According to another one of these predefined patterns, along the straight line, the magnetic field starts at the residual level and then increases in intensity to a peak, relative to the residual level, then decreases in intensity to a trough below the residual level, and then increases in intensity to a second peak, relative to the residual level, and then returns to the residual level, somewhat similar to the shape of a one-and-a-half cycle wave cosine.
[0069] As mentioned, the residual magnetic field corresponds to portions of an item far from any defect. However, the residual field has many features, as the item is not perfectly homogeneous, which can mask the presence of a defect signature. By seeking magnetic field measurements for defect signatures, we can identify the location of defects as compared to non-defect traces at the residual level. We refer to this type of analysis, in which the magnetic fields of the defect(s) is (are) distinguished from the residual level, as the means for detecting defects, as a "spatial analysis".
[0070] In some embodiments, magnetometric data for the item is captured when the item is new or at some other reference point in time. The magnetometric data is stored and then later the magnetometric data is captured again for the same portion of the item, and the two sets of data are compared. Differences between the two data sets represent candidate defects. We refer to this type of analysis, in which datasets captured at different times for determining differences between datasets as a "temporal analysis". Candidate defects can then be analyzed for defect signatures, as in spatial analysis.
[0071] In some embodiments, multiple arrays of magnetometric sensors are attached to an item to be analyzed and remain attached to the item essentially for the life of the item or another extended period of time. Each arrangement like this is affixed to a discreet location on the item. Each arrangement may include an energy collector for the provision of electrical power to operate the arrangement. Arrangements can be interconnected over a wired or wireless network. The network can employ a message sending protocol, a routing algorithm, a clock management and other aspects that allow a linear network, which includes hundreds of nodes with more than ten hops to operate, while consuming very little power. is, it is capable of being powered by energy collectors.
[0072] The magnetometric sensor arrays send data, through the network, to a base station, which analyzes the data for the detection of defects. The base station can be coupled to a distributed control system, a plant management system or another external system. The external system can query the base station about defects or command the base station to initiate a defect detection. Optionally or alternatively, the base station can notify the external system of defects without an inquiry from the external system. Similarly, the base station can sound an alarm, such as turning on a light, sounding a horn, sending an email message or initiating a phone call, and playing a pre-recorded or synthesized voice message if it detects a malfunction. .
[0073] As mentioned, an array of magnetometric data can be attached to an item for the collection of magnetometric data, or the items can be physically scanned by the movement of the magnetometric sensors in relation to the items for the collection of magnetometric data. In any case, magnetometric data can be analyzed temporally or spatially to detect defects. Defects
[0074] As mentioned, defects can be material losses due to corrosion and/or erosion. Examples and modalities are described here in the context of tubes. However, these modalities and examples apply to other types of items such as flat sheets, ship hulls, storage tanks/vessels, profiles, columns, etc.
[0075] Figure 1 is a schematic illustration of a hypothetical tube 100 and a cross section (Section AA) of tube 100. Almost any tube is subject to the development of defects as a result of corrosion or erosion on the outer surface of the tube, as exemplified at 102, for example, as a result of acid rain, chemical spill, or accidental or malicious physical damage. Most pipes are also subject to the development of defects on the inner surfaces of pipes, as exemplified in 104, 106 and 108. For example, sand produced in an oil or gas well is typically transported along the bottom of a pipe and , therefore, can cause abrasion to the bottom of the tube, as exemplified in 104. The areas of the inner wall of a tube, where the top surface of liquid within the tube meets the inner wall of the tube, exemplified in 106 and 108, are common locations for corrosion. A pipe can also develop defects within the pipe wall thickness, as exemplified in 110.
[0076] Erosion often occurs within and slightly downstream of a bend in a pipe 200, at a location indicated by the dashed line 202 in Figure 2. Turbulence due to the change in flow direction creates candidate sites for corrosion. Arrows indicate a flow direction within pipe 200. Enlargements or restrictions in pipes (not shown) not only create potential sites for erosion, they also tend to create turbulence downstream and therefore tend to cause defects adjacent to the turbulent regions. Magnetometers and Defect Detection
[0077] Figure 3 schematically illustrates a magnetic field produced by a hypothetical magnetic dipole 300. The magnetic field lines, exemplified by the line 302, represent the magnetic field. The magnetic dipole 300 sits in a 304 plane and for simplicity only the magnetic field lines 300 in the 304 plane are shown.
[0078] Vector magnetometers measure the vector components of a magnetic field. That is, a vector magnetometer measures the strength of a magnetic field that is directed along an axis of the magnetometer. A three-axis magnetometer 306 measures a magnetic field strength along three X, Y, and Z axes. If magnetometer 306 translates along a line 308 parallel to magnetic dipole 302, magnetometer 306 will detect a magnetic field varying along it. from line 308. For example, the X-axis sensor measures various field strengths, which represent the X components of the magnetic vectors represented by the arrows at A, B, C, D, E, F, G, and H. Figure 4 contains graphs of hypothetical example field strengths Bx, By, and Bz detected by magnetometer 306 along the three axes along line 308. Note that graph Bx resembles a cosine curve and graph Bz resembles a sine curve . These shapes are characteristic of a magnetic field in the vicinity of a discrete magnetic dipole.
[0079] Figure 5 schematically illustrates a hypothetical plate of ferromagnetic material 500. Plate 500 can be considered to be composed of many small aligned magnetic dipoles, exemplified by magnetic dipoles 602 and 604, as illustrated schematically in Figure 6. The lines of magnetic field extend from each small magnetic dipole to its front and rear neighbors, largely in straight lines, and the magnetic field lines exit plate 500 at its ends 502 and 504, essentially as illustrated in figure 3. Little or none of the magnetic field lines exit the plate 500 through its top, bottom or sides.
[0080] However, if the plate has a defect, some material will be lost, as exemplified in Figure 7 by a defect 700 on the surface of a 702 block. Consequently, one or more of the small magnetic dipoles, such as the 602 or magnetic dipoles 604, are lost, and the resulting asymmetrical arrangement of the remaining magnetic dipoles results in some magnetic field lines exiting the block through the top, bottom and/or sides of block 702. Therefore, a signature of a defect, ie. , a missing volume of ferromagnetic material, can be thought of as being approximated by an equal volume of oppositely oriented magnetic dipoles. Even if only internal, ie non-surface, magnetic dipoles are lost, the resulting asymmetrical arrangement of the remaining magnetic dipoles will result in some magnetic field lines exiting the block through the top, bottom and/or sides of block 702.
[0081] The local magnetic field in the vicinity of the lost magnetic dipoles is similar to the magnetic field described above with respect to figures 3 and 4. Consequently, the location of the defect can be found by locating a portion of the magnetic field produced by the plate 702 which has a format similar to the format of the Bx or By graph in Figure 4. Thus, the general formats of the Bx and By graphs can be used as magnetic defect signatures. Tube Defect Detection
[0082] A tube is manufactured in several ways. Each method leaves behind inhomogeneous traces in composition, thickness, temperature history or some other artifact. All of these have the potential to make the intrinsic residual magnetic field not smooth, but have traits of size and complexity so that the defect signature is found to be not straightforward. A common pipe manufacturing artifact is a spiral (helical) pattern of thickness over the length of the pipe. Figure 8 schematically illustrates a tube 800, which shows an artifact of helical thickness like this 802 from its fabrication. Conceptually, tube 800 can be cut along a line 804 parallel to its longitudinal geometric axis and then unrolled onto a flat plate 900, as schematically illustrated in Figure 9. This plate 900 can be analyzed, as described above, with respect to figures 3 to 7.
[0083] Figure 10 contains a graph of the x component of the magnetic field around a 4.5 inch (114.3 mm) diameter tube having a defect of 1 inch x 1 inch x 0.06 inches (25, 4mm x 25.4mm x 1.5mm) on its outer surface. The graph is displayed as a distorted surface 1000. A radial distance from the surface 1000 from a longitudinal geometric axis 1002 of the tube indicates an strength of the x component of the magnetic field.
[0084] Tube manufacturing processes leave artifacts behind in the magnetic field. The helical pattern often observed in the field, due to fabrication processes, trace 802 (figures 8 and 9) is evident in figure 10, in which a crest of magnetic field strength spatially corresponds to the helical fabrication trace, as indicated by the line dashed helical 1004.
[0085] Also evident in Figure 10 is a peak 1006 in magnetic field strength. Furthermore, as indicated by the dotted line 1008, the shape of the surface near peak 1006 is similar to the shape of the By curve in Figure 4 and is therefore characteristic of a defect.
[0086] Similar analyzes can be performed using the y component of the magnetic field around the tube and the z component of the magnetic field. A correlation of defect locations found by the three analyzes provides a more accurate defect location than the analysis of only one component of the magnetic field. Sensor Arrangement
[0087] Figure 11 schematically illustrates an embodiment of the present invention. In this embodiment, a magnetometric sensor unit 1100 is secured around a tube 1102. The magnetometric sensor unit 1100 includes two semicircular portions (half-shells) that are hinged together. The hinge is located on the rear side of the magnetometric sensor unit 1100 and thus is not visible in figure 11. A releasable hitch 1104 mechanically attaches two half shells to each other, thereby clamping the magnetometric sensor unit 1100 around of tube 1102. Coupling 1104 secures magnetometric sensor unit 1100 to tube 1102 tightly enough to prevent a rotation of magnetometric sensor unit 1100 around tube 1102 or a translation of magnetometric sensor unit 1100 along tube 1102 , in response to forces expected to be encountered in normal use, such as in an industrial installation. The coupling 1104 can be keyed to prevent unauthorized removal or tampering with the magnetometric sensor unit 1100. The magnetometric sensor unit 1100 can be constructed to meet ATEX/UL directive standards regarding protection against a explosion as well as it's weather proof.
[0088] Advantageously, since the magnetometric sensor unit 1100 does not need to be in contact with the item being measured, it can be affixed to pipe 1102 over any existing pipe covering, such as thermal insulation or a pipe surface treatment , without removing the tube cover. Additional thermal insulation or other covering can be applied over an installed magnetometric sensor unit 1100, if desired.
[0089] A portion 1105 of the outer housing of magnetometric sensor unit 1100 is shown removed in Figure 11 to reveal an array 1106 of magnetometric sensors. Each magnetometric sensor in array 1106 can be a three-axis magnetometric sensor. As seen through opening 1105 in the outer housing, magnetometric sensors 1106 are arranged around tube 1102 in rings. Each ring includes a number of magnetometric sensors spaced evenly around the ring. These inner rings are spaced longitudinally along tube 1102 at regular intervals, essentially creating a regular two-dimensional array of magnetometric sensors arranged parallel to the outer surface of tube 1102 and spaced a fixed distance, possibly zero, from tube 1102. core circuit 1108 includes an antenna 1110 and circuits that control magnetometric sensors 1106, collect data from magnetometric sensors 1106, and communicate with other magnetometric sensor units and/or a base station (not shown) through a communication network wireless.
[0090] A set of energy collectors 1112 generates electricity from a temperature difference between the tube 1102 and the environment. Optionally or alternatively, 1112 energy collectors can include photovoltaic cells and/or any other suitable energy collection technology. Optionally or alternatively, a primary battery, with or without an energy collector, can be used if the power and lifetime requirements are such that this is a viable alternative. Rechargeable batteries 1114 can be included to store collected energy, until needed by the 1108 core circuit board. The 1112 energy collectors can be arranged in a ring as shown.
[0091] A magnetometer spacing 1106 can be selected to obtain a desired magnetometer density, such as a magnetometer spacing of around 0.3 inches (7.6 mm), i.e. the spacing between magnetometric sensors of three adjacent axes. The spacing between magnetometers can be selected based on the minimum size defect to be detected. The spacing between magnetometers should be selected so that the smallest defect to be detected is covered by a sufficient number of three-axis magnetometric sensors to be able to detect the shape of the defect signature in the magnetic field map.
[0092] Figure 12 schematically illustrates an assembly of magnetometric sensor units 1200 affixed to a tube 1102. As shown in Figure 12, several magnetometric sensor units 1200 can be securely packaged along all or a portion of the length of the tube. 1202. In this mode, each energy slip ring, exemplified by energy slip rings 1204, 1206, and 1206, powers two magnetometric sensor units, one on each side of the energy slip ring. As shown schematically in Figure 13, a set of magnetometric sensor units 1300 can be affixed to a tube 1302 and spaced apart from each other along the tube 1302.
[0093] Figure 14 is a detailed view of a magnetometric sensor arrangement 1400, according to another embodiment. In this embodiment, the magnetometric sensor array 1400 is disposed circumferentially or partially around a tube 1402 as in Figures 11 to 13. The array 1400 includes several array modules, exemplified by array modules 1404, 1406, and 1408. However, for clarity, only eight array modules are shown in Figure 14. Each array module 1404 to 1408 can be detachably affixed to a pair of circumferential mounting rings 1410 and 1412. Optionally or alternatively, the array of modules 1404 to 1408 can be packaged within a protective housing, as discussed with respect to Figures 11 to 13. In some embodiments, additional array modules are affixed to mounting rings 1410 and 1412 so that tube 1402 is enveloped. by arrangement modules. However, in other embodiments, array modules 1404 through 1408 may only cover a portion of the circumference of tube 1402. In some embodiments, array modules 1404 through 1408 may be attached via detachable electrical plugs that facilitate field replacement of the array modules 1404 through 1408. In some embodiments, array modules 1404 through 1408 are interchangeable wired.
[0094] Arrangement 1400 may be driven by a power collector 1414 and may include a core circuit board 1416. Arrangement 1400 includes a wireless transceiver and an antenna (not shown).
[0095] In some embodiments, each array module 1404 to 1408 includes a pair of circuit boards 1500 and 1502, as shown in Figure 15. Each circuit board of the pair of circuit boards 1500 to 1502 includes a row of magnetometers. three-axis, exemplified by the 1504, 1506, and 1508 magnetometers. In some embodiments, each circuit board includes 16 three-axis magnetometers 1504 to 1508.
[0096] Each magnetometric sensor 1504 to 1508 within the 1500 to 1502 to 1408 array module includes three magnetometers (equivalently a three-axis magnetometric sensor). The three magnetometers can be mutually oriented orthogonally, or they can be oriented according to some other known arrangement. A magnetometer orientation here refers to the primary sensitivity geometric axis of the magnetometer. In some arrays, each array module 1404 to 1408 (figure 14) includes an array, such as a 16x1 array (as in figure 15) or a 16x16 array of three-axis magnetometric sensors. Pattern Combination for Defect Signature Finding
[0097] As mentioned, in some modalities, the magnetometric data are searched for any predefined spatial patterns (signatures) that indicate a defect. Patterns can be sinusoidal, and the length (wavelength) of the sine wave can be proportional to the size of the defect. In this sense, the wavelengths of sinusoids are generally unknown a priori. As described above, magnetometric sensor rings 1600 are arranged around the circumference of a tube 1602 to create a regular two-dimensional array of magnetometric sensors arranged parallel to the outer surface of tube 1602, as illustrated schematically in Figure 16. This arrangement of magnetometric sensors produces magnetometric data. Figure 17 includes a graph of this magnetometric data from a real tube. The data in Figure 17 is plotted of component magnetic field strengths detected by x-oriented magnetometers, ie, along the length of the tube. Figure 18 graphs the component magnetic field strengths detected by z-oriented magnetometers, that is, normal (or nearly normal) to the tube surface. A graph (not shown) plots the component magnetic field strengths detected by y-oriented magnetometers, that is, perpendicular to x-oriented and y-oriented magnetometers.
[0098] Each magnetometric sensor (in a sensor unit 1100) (figure 11) is arranged in a given angular position ("clock position"), exemplified in 1604 (figure 16), around the ring 1600. In the mode that generated the data for figures 17 and 18, each ring includes 18 magnetometric sensors. However, other numbers of sensors can be used. Each horizontal line generally, exemplified by lines 1700, 1702, and 1704, represents data from the x-component detection magnetometer at a discrete angular position around the tube. Thus, the vertical axis represents the angular position around the tube. The horizontal axis represents the distance along the length of the tube. Thus, points along each line 1700 to 1704 represent magnetic field strengths along the length of the tube. Similarly, Figure 18 shows the z component of the magnetic field in positions co-located with the data in Figure 17. Helical variations in the magnetic field due to tube fabrication processes are evident, as indicated in 1710, 1712, 1800, and 1802 Defect signatures are present in 1714, 1716, 1804 and 1806. How this defect is detected is described below.
[0099] The data collected from the magnetometers need to be processed so that they are continuously differentiable in spatial dimensions along the tube and around the tube. Standard approximations are used for filling gaps in the sensor data and smoothing and interpolating the data so that spatial partial derivatives can be calculated.
[00100] Along each line 1700 to 1704 in the graph of figure 17, and similarly along each line in the other two component directions (as in figure 18, which shows one or more of the vector components of the field magnetic), spatial derivatives (inclines or rates of change) are calculated. Figures 19 and 20 are graphs of the derivatives calculated from Figures 17 and 18, respectively. The motivation for calculating derivatives is that, while the magnetic signature of the defect and the residual magnetic field are similar in magnitude, the defects tend to be smaller in extent and have sharper rises and falls. Hence, a derivative tends to amplify this higher frequency behavior, and the defect stands out in amplitude and wavelength compared to the traces of the residual field derivative. As can be seen in Figure 20, for example, most traces have a moderate amplitude (hence, moderate slopes in the magnetic field signal). These are the traits that are not in the defect areas. The light gray lines 2000 in the center of figure 20 are the two lines that cross the defect. It is seen that, in this derivative graph, these features stand out in the magnitude of the non-defect (residual) areas, providing additional information for a detection algorithm to operate.
[00101] An automatic pattern combiner searches the resulting derivatives for portions that match one or more of several sine or cosine models. Each model corresponds to a different spatial wavelength. Many models are used because, as mentioned, the spatial extent of the defect, hence the spatial wavelength of the sine and cosine of the defect, are not known a priori. The model with the wavelength that has the strongest correlation with the magnetic field data is used for defect detection and characterization.
[00102] The defect locations evaluated in the three separate analyses, that is, for the x, y and z components of the magnetic field, are merged to produce a final defect location and a confidence level. Defect Characterization
[00103] Once the location of a defect has been found, the defect can be characterized in terms of volume (amount of material lost) and surface extent (on the tube surface or parallel to the tube surface, if the defect is internal to the tube). In some cases, assumptions are made about the general shape of a defect. For example, the defect can be assumed to be generally circular or elliptical on a surface of a tube or to have a vertical profile of some kind. With these types of assumptions, the area and depth of the defect can be approximated.
[00104] The z component of the measured magnetic field is normal to the surface of the ferromagnetic material being measured, as shown in figure 21 for a tube. The amplitude of the z component of the magnetic field is proportional to the amount of ferromagnetic material lost due to the defect. Thus, for defects having identical diameters, the z component of the magnetic field is also proportional to the depth of the defect. The graph in Figure 21 represents three simulated defects, all of the same diameter on the tube surface (four times the wall thickness of a tube). Curve 2100 represents a defect whose depth is 30% of the pipe wall thickness. Curve 2102 represents a defect whose depth is 15% of the pipe wall thickness. Curve 2104 represents a defect whose depth is 7% of the pipe wall thickness. As can be seen from the graph, the amplitude of the z component of the magnetic field is related to the depth of the defect. The amplitude of the z component is more proportional to the volume of material lost, and for a set of assumptions on typical defect growth shapes, the defect depth can be inferred. This result can be seen in all three magnetic field axes. Thus, given a magnetic field component amplitude, the volume of the defect can be determined, assuming the magnetization of the material is known, as further described below. This information, combined with a defect area and a depth profile, allows the determination of an approximate defect depth.
[00105] However, for a given defect depth, the amplitude of any of the components of the magnetic field increases with an increase in the defect surface area. This is to be expected, as the signal amplitude is proportional to the volume of the defect, and as the surface area increases to a specified depth, the volume of the defect also increases. In Figure 22, the graph represents the z component of the magnetic field for three simulated defects, all having the same depth (15% of the tube wall thickness). Curve 2200 represents a defect whose diameter is 2 inches (50.8 mm). Curve 2202 represents a defect whose diameter is 1 inch (25.4 mm). Curve 2204 represents a defect whose diameter is 0.5 inches (12.7 mm). As can be seen, with a constant defect depth, the amplitude of the z component of the magnetic field increases with the surface area of a defect, due to the increasing defect volume. However, the increase follows a predictable curve (since it represents volume) shown in 2206. Consequently, this increase can be accounted for in a mathematical model. The distance from the valley on the graph to the peak on the graph, denoted as "extent" 2208, is proportional to the extent of the defect along the direction of the magnetometers that created the graph.
[00106] Defect signal strengths are proportional to both the amount of material missing and the level of magnetization of the material. Thus, the determination of a tube magnetization is useful for the determination of the volume of material missing and, thus, is useful for the defect area and depth characterizations. The determination of the magnetic field should not be made at the location of the defect but should be made at a nearby non-defect location. This local "residual" tube magnetization measurement allows for the normalization of defect signals, thereby effectively calibrating defect volume and depth calculations. Having located the defects as described above, a defect detection system measures the tube's residual magnetization level, that is, a magnetization level in an area that does not include a defect.
[00107] Figure 23 is a graph of magnetic field strength along the x-axis (longitudinal through the tube) near a defect in a tube. All three graphs represent the same tube defect, and all three graphs show the signature of a defect. However, before data for each graph was collected, the tube was magnetized to a different degree. For the 2300 graph, the tube was magnetized with a coil operated at an intensity of 690 A/m (amps/meter). For graph 2302, the tube was magnetized at 460 A/m. For graph 2304, the tube was magnetized at 230 A/m. As can be seen from the graphs, the defect signals increase in direct proportion to a tube magnetization.
[00108] One modality for measuring the intensity of the local residual field in the tube is shown graphically in figure 24. For tubes that have leak paths (often because they are inhomogeneous due to manufacturing processes), the magnetic field z ( radial with respect to the central geometric axis of the tube) has an inclination for the length of the tube. This slope is proportional to the magnetic field strength. The slope traces in figure 24 correspond to the magnetization cases shown in figure 23, with the smaller slope corresponding to the 230 A/m case and the larger slope corresponding to the 690 A/m case. Under these conditions, the z component of the magnetic field provides an independent measure of the residual magnetic field strength in the tube.
[00109] The graphs in figure 23 were normalized, according to the level of residual magnetization, producing graphs in figure 25, which are numbered to correspond to the graphs in figure 23. As can be seen by comparing figures 23 and 25, a signal amplitude can be made largely independent of a tube magnetization level by normalizing according to the tube's residual magnetization level. In this way, magnetic measurement ranges can be converted to volume and area, with a depth calculation following.
[00110] Other methods of determining the residual magnetization level of a tube are devised. For example, a tube can be magnetized to a known level when the tube is installed, or the tube can be magnetized to an arbitrary level and the level of magnetization can be measured. In either case, this magnetization level can be stored in memory accessible by a base station, and used later when defects have been detected and volume and depth information is desired. Optionally or alternatively, even if information about a previous tube magnetization level was not stored, once defects had been detected, magnetometric sensors could be used to measure a residual tube magnetization in one or more areas away from all defects detected using the slant method, above or other independent measurement approaches.
[00111] As used here, a "standoff" means a distance between a defect and a magnetometer, as illustrated schematically in Figure 26. Theory and tests show that a signal strength drops according to a law of inverse squared when near a magnetic dipole. If the sensor has a standoff similar to the distance to the dipole's characteristic length, the dipole will appear as two independent poles, and the signal strength will drop as an inverse squared. As standoff increases, the dipole range appears to decrease and becomes a point source. Under these conditions, theory and tests show that the signal strength falls according to an inverse-cube law. Thus, small defects have more signal loss as distance (standoff) moves beyond the defect size, while a large defect continues to "enjoy" an inverse squared degradation of its signal for longer standoffs. For example, for a 1-inch (25.4 mm) square defect, a signal loss is greater than nearly an order of magnitude when the standoff is increased by 0.25 inches (6.4 mm) to 2.25 inches (51.2 mm). Residual tube magnetization traces fall in intensity more slowly due to their greater spatial extent. Nevertheless, the apparatus and methods described here reliably detect defects expected to be found without a conventional pipe, such as those in oil and gas pipelines, refineries, etc.
[00112] Defects in a tube wall thickness or an inner wall are necessarily farther away from magnetometers than defects in an outer tube wall. However, simulations and tests indicate only less signal loss from an internal defect versus an external defect, as indicated in the graphs in Figure 27. Much of the signal amplitude reduction is due to the increased standoff implied by an internal defect , as opposed to an external defect. Graph 2700 is for an external defect and graph 2702 is for an internal defect.
[00113] As shown in the preceding discussion, many of the parameters in the detected signals have multiple dependent sources. These dependencies must be understood and managed when performing a detection and characterization of a defect. A relationship is that of a sensor spacing. As implied in figures 14 and 15, a close spacing of the magnetometric sensors (magnetometer) is of interest. Magnetometer spacing refers to how small a defect (as measured along the surface) can be detected and characterized. Since the detection method is based on finding correlations with sine and cosine waves, there needs to be a sufficient number of magnetometers along the sine wave to determine that it is truly a sine wave. In practice, sensors spaced from 0.3 inches to 0.4 inches (7.6 to 10.2 mm) can be used to detect defects of around 1 inch (25.4 mm) in a close standoff (1 inch (25.4 mm or less) As standoff increases or surface dimensions decrease, the ability to reliably detect a defect decreases, with an increasing probability of missed or missed detections. false alarms. Temporal Defect Detection
[00114] As mentioned, in some embodiments of the present invention, instead of seeking magnetometric data for defect signatures, two sets of data collected at different times are compared for the detection of defects. For example, a dataset can be collected when an item is new or at some other point in time. The second set of data is collected later. The two sets are spatially correlated, and then magnetic field strengths in the second data set are subtracted from spatially corresponding magnetic field strengths in the first data set. These subtractions are performed by axis. Figure 28 is a surface graph of the result of this subtraction, showing the x-axis of the magnetic field. A defect signature is clearly visible, as emphasized by the 2800 dashed line. The shape of the 2800 line is similar to the shape of the By curve in Figure 4, and therefore is characteristic of a defect. In practice, the defect is found following this temporal subtraction by the basic method of spatial analysis (adjusting one of sine and cosine waves to confirm that the remaining signal is a signature of a defect. As described above, with respect to a spatial defect detection, spatial information about defects detected on each of the three axes can be combined to produce more accurate defect detection information.The above approaches to defect characterization (volume, area and depth) can be applied after this temporal method. Physical Scan of an Item for Defects
[00115] As mentioned, the magnetometric data about an item can be obtained by a fixed set of magnetometric sensors arranged around an item. Optionally or alternatively, the item can be physically scanned by a smaller set of magnetometric sensors than would otherwise be required to obtain magnetometric data without a scan. The item can be scanned along its longitudinal axis or along any other suitable direction. Figure 29 is a perspective illustration of a physical scanner 2900. An item 2902, such as a tube, can be scanned by the scanner 2900. A single magnetometric sensor, a small group of magnetometric sensors, or a one-dimensional array of magnetometric sensors 2904 is supported by a scanner arm with one, two or three degrees of freedom 2906. A first linear motor 2908 positions the magnetometric sensor array 2904 vertically at a suitable distance from item 2903. A second linear motor 2910 positions the magnetometric sensor array 2904 along a geometric axis perpendicular to the sweep axis. A third linear motor 2912 translates the magnetometric sensor array 2904 along the sweep axis. Once a sweep has been completed, the item can be rotated around the sweep axis, and another sweep can be performed. This process can be repeated, until all desired portions of the item have been scanned.
[00116] In another embodiment, illustrated in perspective in Figure 30, a ring of magnetometric sensors is translated by the physical scanner 3002. In other embodiments, the scan can be two-dimensional. For example, with a suitable physical scanner, the item can be spirally scanned, scanned with exploratory scan, or scanned according to another path.
[00117] Data collection control functions from magnetometers, magnetic field mapper, pattern combiner and base station and other functions described here can be performed by a processor executing instructions stored in memory, as illustrated schematically in figure 31.
[00118] Although the invention is described through the example modalities described above, modifications and variations of the illustrated modalities can be made, without deviating from the inventive concepts set out here. Furthermore, the exposed aspects, or portions thereof, may be combined in ways not listed above and/or not explicitly claimed. Therefore, the invention is not to be seen as being limited to the disclosed embodiments.
[00119] Although aspects of modalities may be described above with reference to flowcharts and/or block diagrams, functions, operations, decisions, etc. of all or a portion of each block, or a combination of blocks, can be combined, separated into separate operations, or performed in other orders. All or a portion of each block or a combination of blocks can be implemented as computer program instructions (such as software), hardware (such as combinatorial logic, application-specific integrated circuits (ASICs), programmable gate arrays field (FPGAs) or other hardware), firmware or combinations thereof. Modalities can be implemented by a processor executed or controlled by instructions stored in memory. The memory can be random access memory (RAM), read-only memory (ROM), flash memory or any other memory, or a combination thereof, suitable for storing control software or other instructions and data. . Instructions defining the functions of the present invention can be delivered to a processor in many ways, including, but not limited to, information permanently stored on tangible, non-writable storage media (e.g., read-only memory devices on a computer, such as such as a ROM, or devices that can be read by a computer I/O accessory, such as CD-ROM or DVD disks), an information alterably stored on tangible recordable storage media (eg, floppy disks, a removable flash memory and hard drives) or information transported to a computer via a means of communication, including wired or wireless computer networks. Furthermore, although embodiments can be described in relation to various illustrative data structures, systems can be realized using a variety of data structures.

权利要求:
Claims (19)
[0001]
1. Method for detecting defects in a ferromagnetic material, the method characterized in that it comprises: arranging a plurality of magnetometers (1504, 1506, 1508) on a surface of the ferromagnetic material, wherein each magnetometer of the plurality of magnetometers (1504, 1506, 1508) is fixed in position with respect to the ferromagnetic material; using the plurality of magnetometers (1504, 1506, 1508) to detect a magnetic field generated by the ferromagnetic material at a first point in time; generating data points from a first two-dimensional map of the detected magnetic field, each data point corresponding to a respective location on the surface of the ferromagnetic material and representing intensity of the detected magnetic field near the location at the first point in time; use the plurality of magnetometers (1504, 1506, 1508) to detect the magnetic field generated by the ferromagnetic material at a second point in time, later than the first point in time, generate data points from a second two-dimensional map of the magnetic field detected, each data point corresponding to a respective location on the surface of the ferromagnetic material and representing intensity of the detected magnetic field near the location at the second point in time; subtracting the second two-dimensional map data points from the spatially corresponding point data of the first two-dimensional map, thereby producing a two-dimensional difference map; identifying, in the two-dimensional difference map, a plurality of data points that conform to a predefined spatial pattern of magnetic field strength; and extracting a location close to the surface of the ferromagnetic material that corresponds to the plurality of data points.
[0002]
2. Method according to claim 1, characterized in that the subtraction is performed by axis.
[0003]
3. Method according to claim 1, characterized in that it further comprises estimating a missing material volume of the ferromagnetic material at the location close to the surface of the ferromagnetic material, based on the amplitude of a trace represented by data in the plurality of points of data.
[0004]
4. Method according to claim 3, characterized in that it further comprises estimating a depth of missing material, based on the estimated volume of missing material and the length in two spatial directions of a trace represented by data in the plurality of points of data.
[0005]
5. Method according to claim 1, characterized in that it further comprises: determining the amplitude of the magnetic field generated by the ferromagnetic material at a location distant from the location close to the surface of the ferromagnetic material, based on at least one of the points of map data; and estimate a missing material volume of the ferromagnetic material at the location close to the surface of the ferromagnetic material, according to data amplitude in the plurality of data points and the amplitude of the magnetic field generated by the ferromagnetic material at a location distant from the location near the surface of the ferromagnetic material.
[0006]
6. Method according to claim 5, characterized in that it further comprises estimating an area of the missing material, based on length in two spatial directions of a trace represented by data in the plurality of data points.
[0007]
7. Method according to claim 5, characterized in that it further comprises estimating a depth of missing material, based on the estimated volume of missing material and the length in two spatial directions of a trace represented by data in the plurality of points of data.
[0008]
8. Method according to claim 1, characterized in that identifying the plurality of data points that conform to a predefined spatial pattern comprises fitting at least one of a sine curve and a cosine curve to the plurality of points of data.
[0009]
9. Method according to claim 1, characterized in that it further comprises: calculating a plurality of spatial derivative values from the two-dimensional difference map data points; and wherein: identifying the plurality of data points that conform to a predefined spatial pattern comprises identifying a plurality of data points that conform to the predefined spatial pattern of magnetic field strength from the plurality of spatial derivative values .
[0010]
10. Method according to claim 1, characterized in that identifying the plurality of data points that conform to a pre-defined spatial pattern comprises identifying a plurality of data points that correspond to a loss of a portion of the ferromagnetic material due to corrosion or erosion.
[0011]
11. Method according to claim 1, characterized in that identifying the plurality of data points that conform to a pre-defined spatial pattern comprises identifying a plurality of data points that correspond to a crack in the ferromagnetic material.
[0012]
12. Method according to claim 1, characterized in that arranging the plurality of magnetometers (1504, 1506, 1508) comprises arranging the plurality of magnetometers (1504, 1506, 1508) on a cylindrical surface surrounding an outer surface of the ferromagnetic material.
[0013]
13. Method according to claim 1, characterized in that arranging the plurality of magnetometers (1504, 1506, 1508) comprises arranging the plurality of magnetometers (1504, 1506, 1508) on a cylindrical surface, so that the plurality of magnetometers (1504, 1506, 1508) define a cylindrical lumen sized to receive the ferromagnetic material.
[0014]
14. Method according to claim 1, characterized in that arranging the plurality of magnetometers (1504, 1506, 1508) comprises arranging the plurality of magnetometers (1504, 1506, 1508) as a two-dimensional array of magnetometers wrapped around of the ferromagnetic material.
[0015]
15. The method of claim 1, wherein arranging the plurality of magnetometers (1504, 1506, 1508) comprises arranging the plurality of magnetometers (1504, 1506, 1508) as a plurality of magnetometer rings, including space the plurality of magnetometer rings longitudinally along the ferromagnetic material so that each ring of the plurality of magnetometer rings surrounds the ferromagnetic material.
[0016]
16. Method according to claim 1, characterized in that: each magnetometer of the plurality of magnetometers (1504, 1506, 1508) comprises three orthogonally oriented magnetometers; generating the data points comprises generating the data points such that each data point of the respective first and second two-dimensional maps represents detected magnetic field strength in each of three orthogonal directions; and identifying the plurality of data points that conform to the predefined spatial pattern comprises, for each of the three orthogonal directions, identifying a plurality of data points that conform to a predefined spatial pattern of magnetic field strength and a location near the surface of the ferromagnetic material that corresponds to the plurality of data points, thereby identifying three locations near the surface of the ferromagnetic material; the method further comprising: calculating a refined location close to the surface of the ferromagnetic material from the three identified locations; and where: extracting the location comprises extracting the refined location.
[0017]
17. The method of claim 1, characterized in that arranging the plurality of magnetometers (1504, 1506, 1508) comprises arranging the plurality of magnetometers (1504, 1506, 1508) on a surface that extends less than circumferentially around an outer surface of the ferromagnetic material.
[0018]
18. Method according to claim 1, characterized in that arranging the plurality of magnetometers (1504, 1506, 1508) comprises organizing the plurality of magnetometers (1504, 1506, 1508) as a two-dimensional array of magnetometers.
[0019]
19. Method for detecting defects in a ferromagnetic material, the method characterized in that it comprises: detecting a magnetic field generated by the ferromagnetic material at a first point in time; generating data points from a first two-dimensional map of the detected magnetic field, each data point corresponding to a respective location on the surface of the ferromagnetic material and representing intensity of the detected magnetic field near the location at the first point in time; detect the magnetic field generated by the ferromagnetic material at a second point in time, later than the first point in time, generate data points from a second two-dimensional map of the detected magnetic field, each data point corresponding to a respective location on the surface of the ferromagnetic material and representing the intensity of the magnetic field detected near the location at the second point in time; subtracting the data points from the second two-dimensional map from the spatially corresponding data points from the first two-dimensional map, thereby producing a two-dimensional map of difference; identifying, in the two-dimensional difference map, a plurality of data points that conform to a predefined spatial pattern of magnetic field strength; and extracting a location close to the surface of the ferromagnetic material that corresponds to the plurality of data points; wherein detecting the magnetic field comprises detecting the magnetic field with a plurality of magnetometers (1504, 1506, 1508), each magnetometer of the plurality of magnetometers (1504, 1506, 1508) comprising three orthogonally oriented magnetometers; generating the data points comprises generating the data points such that each data point of the respective first and second two-dimensional maps represents detected magnetic field strength in each of three orthogonal directions; and identifying the plurality of data points that conform to the predefined spatial pattern comprises, for each of the three orthogonal directions, identifying a plurality of data points that conform to a predefined spatial pattern of magnetic field strength and a location near the surface of the ferromagnetic material that corresponds to the plurality of data points, thereby identifying three locations near the surface of the ferromagnetic material; the method further comprising: calculating a refined location close to the surface of the ferromagnetic material from the three identified locations; and where: extracting the location comprises extracting the refined location.

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BR122018009767B1|2021-07-20|

CN108663431B|2019-11-19|

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法律状态:
2020-03-24| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

2021-03-02| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

2021-05-11| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 15/05/2015, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

申请号 | 申请日 | 专利标题

US201461994961P| true| 2014-05-18|2014-05-18|

US61/994,961|2014-05-18|

PCT/US2015/031092|WO2015179237A1|2014-05-18|2015-05-15|System and method of measuring defects in ferromagnetic materials|BR122018009767-1A| BR122018009767B1|2014-05-18|2015-05-15|SYSTEM AND METHOD FOR DETECTING DEFECTS IN A FERROMAGNETIC MATERIAL AND NON TRANSIENT COMPUTER-READABLE MEDIA|

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