Oil and gas pipeline internal detection device and method based on residual magnetism and eddy current coupling

Abstract

The invention discloses an oil and gas pipeline internal detection device and method based on the coupling effect of residual magnetism and eddy current, and relates to the technical field of pipeline internal detection. A magnetization node is used to perform saturation magnetization on the pipeline to be detected. When the magnetization node stops magnetizing, the magnetization intensity of the pipeline to be detected decreases from the saturation magnetization intensity to the residual magnetization intensity, and is in a residual magnetization state. An induced eddy current field is generated in the pipeline to be detected by the detection node. The defects of the pipeline to be detected are detected based on the coupled magnetic field formed by the residual magnetization intensity and the induced eddy current field. By magnetizing the pipeline to be detected to the magnetic saturation state, the uneven distribution of the relative magnetic permeability of the pipeline can be eliminated, and the probability of missed detection and false detection of pipeline defects caused by the uneven relative magnetic permeability can be reduced. At the same time, the skin effect of the eddy current detection technology can be suppressed, and the effective detection of internal and external surface defects can be realized. The detection node can obtain the composite signal of residual magnetism and eddy current, and the sensitivity of defect perception is improved, thereby improving the eddy current perception ability based on the residual magnetism effect.

Description

Technical Field

[0001] The present invention relates to the technical field of in-pipe inspection, and particularly to an in-pipe inspection device and method for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current. Background Art

[0002] Eddy current non-destructive testing is a commonly used non-destructive testing method, which has the advantages of high sensitivity and non-contact, and detects defects in materials by inducing changes in eddy current. However, when applying eddy current non-destructive testing to oil and gas pipelines with uneven relative magnetic permeability, certain difficulties are faced. Due to the frequent changes in the working conditions of the pipeline and the different technological processes such as quenching and welding during the processing and manufacturing of the pipeline, the relative magnetic permeability of some pipelines is uneven, resulting in abnormal defect response signals and increasing the probability of false defect judgment. At the same time, traditional eddy current in-pipe inspection equipment can only detect inner surface defects of the pipeline and does not have the ability to identify outer surface defects of the pipeline. Summary of the Invention

[0003] The purpose of the present invention is to provide an in-pipe inspection device and method for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current, which uses the residual magnetism effect to eliminate or weaken the unevenness of the relative magnetic permeability of the pipeline, and reduce the missed detection and false detection of defects caused by the uneven relative magnetic permeability. At the same time, by using the in-pipe inspection device for oil and gas pipelines to obtain residual magnetism and eddy current signals simultaneously, the defect recognition ability can be improved, and effective detection of inner and outer surface defects of the pipeline can be realized.

[0004] To achieve the above purpose, the present invention provides the following solutions:

[0005] An in-pipe inspection device for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current, comprising: a magnetization section and a detection section; the magnetization section and the detection section are fixedly connected;

[0006] The magnetization section is located inside the pipeline to be measured; the magnetization section is used to magnetize the pipeline to be measured to saturation and stop magnetization after the pipeline to be measured is in a magnetically saturated state; when the magnetization section stops magnetization, the pipeline to be measured demagnetizes, and the magnetization intensity of the pipeline to be measured drops from the saturation magnetization intensity to the residual magnetization intensity;

[0007] The detection section is located inside the pipeline to be measured; the detection section is used to generate an induced eddy current field in the pipeline to be measured when the magnetization intensity of the pipeline to be measured drops to the residual magnetization intensity, and detect defects of the pipeline to be measured based on the coupling magnetic field formed by the residual magnetization intensity and the induced eddy current field; the defects include inner surface defects and outer surface defects.

[0008] In some embodiments, the magnetization section and the detection section are arranged at intervals.

[0009] In some embodiments, the magnetization section includes a first cylinder and a magnetization device; the magnetization device includes a plurality of magnetization components, each of the magnetization components is mounted on the first cylinder, and the plurality of magnetization components are distributed in a circumferential array around the first cylinder; the magnetization components are used to magnetize the pipeline to be measured.

[0010] In some embodiments, the magnetization component includes a U-shaped magnetic yoke, and the first magnetic pole and the second magnetic pole of the U-shaped magnetic yoke are both in contact with the inner surface of the pipeline to be measured; a coil is mounted on the U-shaped magnetic yoke, and when a direct current is passed through the coil, the pipeline to be measured is magnetized; alternatively, permanent magnets are mounted on both the first magnetic pole and the second magnetic pole to magnetize the pipeline to be measured.

[0011] In some embodiments, the detection section includes a second cylinder and a plurality of detection probes; each of the detection probes is mounted on the second cylinder, and the plurality of detection probes are distributed in a circumferential array around the second cylinder.

[0012] In some embodiments, the detection probe includes a first coil, a detection module, and a second coil, and the detection module is located between the first coil and the second coil; both the first coil and the second coil are in contact with the detection module;

[0013] The first coil and the second coil are used to be passed through an alternating current to generate an induced eddy current field in the pipeline to be measured;

[0014] The detection module is used to detect the coupled magnetic field formed by the residual magnetization intensity and the induced eddy current field and output a voltage signal.

[0015] In some embodiments, both the first coil and the second coil are toroidal coils wound by wires; the detection module includes a PCB circuit board and a plurality of magnetic chips, and the plurality of magnetic chips are fixedly mounted on the PCB circuit board.

[0016] In some embodiments, the detection section further includes a plurality of detection probe brackets; each detection probe bracket corresponds to one detection probe; the detection probe is mounted on the detection probe bracket, and the detection probe bracket is mounted on the second cylinder.

[0017] In some embodiments, the detection section further includes a plurality of wear-resistant pieces; each wear-resistant piece corresponds to one detection probe; the wear-resistant piece is located at the top of the detection probe, and the wear-resistant piece is fixedly mounted on the detection probe.

[0018] An in-pipe detection method for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current works based on the above-mentioned in-pipe detection device for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current, and includes:

[0019] The measured pipeline is saturatedly magnetized by a magnetization section, and the magnetization is stopped after the measured pipeline is in a magnetically saturated state, so that the magnetization intensity of the measured pipeline drops from the saturated magnetization intensity to the residual magnetization intensity; an induction eddy current field is generated in the measured pipeline by a detection section, and defects of the measured pipeline are detected based on the coupling magnetic field formed by the residual magnetization intensity and the induction eddy current field; the defects include inner surface defects and outer surface defects.

[0020] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0021] The present invention provides an in-pipe inspection device and method for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current. The measured pipeline is saturatedly magnetized by a magnetization section. After the magnetization section stops magnetizing, the magnetization intensity of the measured pipeline drops from the saturated magnetization intensity to the residual magnetization intensity and is in a residual magnetism state. An induction eddy current field is generated in the measured pipeline by a detection section, and defects of the measured pipeline are detected based on the coupling magnetic field formed by the residual magnetization intensity and the induction eddy current field. By magnetizing the measured pipeline to a magnetically saturated state, the non-uniform distribution of the relative magnetic permeability of the pipeline can be eliminated, and the probability of missed detection and false detection of pipeline defects caused by the non-uniformity of the relative magnetic permeability can be reduced. At the same time, the skin effect of the eddy current detection technology can be suppressed, and effective detection of inner and outer surface defects can be achieved. The detection section can obtain the composite signal of residual magnetism and eddy current, improve the sensitivity of defect perception, and thus improve the eddy current perception ability based on the residual magnetism effect. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 It is a schematic structural diagram of an in-pipe inspection device for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current provided by Embodiment 1 of the present invention.

[0024] Figure 2 It is a schematic structural diagram of a detection probe provided by Embodiment 1 of the present invention.

[0025] Figure 3 It is a schematic diagram of the detection principle of an in-pipe inspection device for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current provided by Embodiment 1 of the present invention.

[0026] Figure 4 It is a schematic diagram of the working process of an in-pipe inspection device for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current provided by Embodiment 1 of the present invention.

[0027] Figure 5 Schematic diagram of the magnetization intensity - magnetic field intensity change curve provided in Embodiment 1 of the present invention.

[0028] Figure 6 Schematic diagram of the spatial magnetic signal provided in Embodiment 1 of the present invention.

[0029] Figure 7 Schematic diagram of the defect detection principle provided in Embodiment 1 of the present invention; wherein, Figure 7 (a) Schematic diagram of the detection principle under the condition of no remanence; Figure 7 (b) Schematic diagram of the generation of the remanence condition; Figure 7 (c) Schematic diagram of the detection principle under the condition of having remanence.

[0030] Symbol description:

[0031] 1 - magnetization section; 2 - detection section; 3 - first cylinder; 4 - magnetization device; 5 - second cylinder; 6 - detection probe; 7 - first coil; 8 - second coil; 9 - PCB circuit board; 10 - magnetic chip; 11 - first leather cup; 12 - second leather cup; 13 - third leather cup; 14 - fourth leather cup; 15 - odometer wheel. Specific implementation manner

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] The purpose of the present invention is to provide an in - pipeline detection device and method for oil and gas pipelines based on the coupling effect of remanence and eddy current, using the remanence effect to eliminate or weaken the non - uniformity of the relative magnetic permeability of the pipeline, and reducing the missed detection and false detection of defects caused by the non - uniformity of the relative magnetic permeability. At the same time, by using the in - pipeline detection device for oil and gas pipelines to simultaneously obtain remanence and eddy current signals, the defect recognition ability can be improved, and effective detection of internal and external surface defects of the pipeline can be realized.

[0034] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0035] Embodiment 1

[0036] As Figure 1 shown, this embodiment provides an in - pipeline detection device for oil and gas pipelines based on the coupling effect of remanence and eddy current, including: a magnetization section 1 and a detection section 2, and the magnetization section 1 and the detection section 2 are fixedly connected.

[0037] The magnetization section 1 is located inside the pipeline to be measured. The magnetization section 1 is used to magnetize the pipeline to be measured to saturation, magnetize the pipeline to be measured to the magnetic saturation state, and stop magnetization after the pipeline to be measured reaches the magnetic saturation state. When the magnetization of the magnetization section 1 stops, the pipeline to be measured demagnetizes, and the magnetization intensity of the pipeline to be measured decreases from the saturation magnetization intensity to the residual magnetization intensity, so that the pipeline to be measured is in the remanent magnetic state.

[0038] The detection section 2 is located inside the pipeline to be measured. The detection section 2 is used to generate an induced eddy current field in the pipeline to be measured when the magnetization intensity of the pipeline to be measured decreases to the residual magnetization intensity, and detect the defects of the pipeline to be measured based on the coupling magnetic field formed by the residual magnetization intensity and the induced eddy current field. The defects include inner surface defects and outer surface defects.

[0039] In this embodiment, the magnetization section 1 and the detection section 2 are arranged at intervals, that is, there is an appropriate distance between the magnetization section 1 and the detection section 2, ensuring that the magnetization device 4 in the magnetization section 1 will not interfere with the detection probe 6 in the detection section 2, so that the magnetization process will not affect the detection process.

[0040] In this embodiment, the magnetization section 1 includes a first cylinder 3 and a magnetization device 4. The magnetization device 4 is used to magnetize the pipeline to be measured. The magnetization device 4 includes a plurality of magnetization components, and each magnetization component is installed on the first cylinder 3. The plurality of magnetization components are distributed in a circumferential array around the first cylinder 3, and the magnetization components are used to magnetize the pipeline to be measured. Alternatively, the magnetization device 4 of this embodiment may only include one magnetization component, which is circular ring-shaped and sleeved on the first cylinder 3. As an example, the magnetization device 4 in the magnetization section 1 of this embodiment includes sixteen magnetization components arranged equidistantly along the circumferential direction on the first cylinder 3. The sixteen magnetization components can also be arranged in two columns, with eight magnetization components in each column, that is, the magnetization device 4 includes eight magnetization components arranged equidistantly along the circumferential direction on the first cylinder 3 in two columns.

[0041] In this embodiment, the magnetization component includes a U-shaped magnetic yoke. The first magnetic pole and the second magnetic pole of the U-shaped magnetic yoke are both in contact with the inner surface of the pipeline to be measured. A coil is installed on the U-shaped magnetic yoke. When a direct current is passed through the coil, the pipeline to be measured is magnetized; alternatively, permanent magnets are installed on both the first magnetic pole and the second magnetic pole to magnetize the pipeline to be measured.

[0042] When the method of installing a coil on the U-shaped magnetic yoke and magnetizing the pipeline to be measured by passing a direct current through the coil is adopted, the magnetization degree of the pipeline to be measured can be adjusted by adjusting the magnitude of the direct current; when the method of installing permanent magnets on both the first magnetic pole and the second magnetic pole to magnetize the pipeline to be measured is adopted, the magnetization degree of the pipeline to be measured can be adjusted by adjusting the material and volume of the permanent magnets.

[0043] In this embodiment, the detection section 2 includes a second cylinder 5 and a plurality of detection probes 6. Each detection probe 6 is mounted on the second cylinder 5, and the plurality of detection probes 6 are distributed in a circumferential array around the second cylinder 5. As Figure 2 shown, the detection probe 6 includes a first coil 7, a detection

[0044] module, and a second coil 8. The detection module is located between the first coil 7 and the second coil 8, and both the first coil 7 and the second coil 8 are in contact with the detection module. The first coil 7 and the second coil 8 are used to be passed through an alternating current to generate an induced eddy current field in the pipeline to be measured. The detection module is used to detect the coupled magnetic field formed by the residual magnetization intensity and the induced eddy current field. The coupled magnetic field includes the residual magnetic field caused by the residual magnetization intensity and the induced magnetic field caused by the induced eddy current field, and outputs a voltage signal.

[0045] Both the first coil 7 and the second coil 8 are annular coils wound by wires. The detection module includes a PCB circuit board 9 and a plurality of magnetic chips 10. The plurality of magnetic chips 10 are fixedly mounted on the PCB circuit board 9, and the plurality of magnetic chips 10 can be distributed in an array, that is, the detection module includes a PCB circuit board 9 and a plurality of magnetically chips 10 arranged in an array, and the magnetic chips 10 can be soldered on the PCB circuit board 9. For example, the detection module includes five magnetic chips 10. Each magnetic chip 10 can collect the magnetic field change in space and output a voltage signal. Whether there is a defect is judged by the voltage signal. The specific judgment method is as follows: when there is no defect, ideally the amplitude of the voltage signal is a fixed constant. When the amplitude of the voltage signal changes, it means that there is a defect at this time. Equivalent to when the voltage signal changes, it means that a defect is detected. The magnetic chip 10 is preferably TMR2103. TMR2103 adopts a unique push-pull type Wheatstone full-bridge structure design, which includes four non-shielded high-sensitivity TMR sensor elements. When the externally applied magnetic field changes along the sensitive direction parallel to the magnetic chip 10, the Wheatstone full-bridge provides a differential voltage output, and this output has good temperature stability. Arranging the magnetic chips 10 inside the detection module can save space, reduce the undetected gaps in the pipeline to be measured, and not only can detect defects, but also can judge the defect direction according to the time difference of the signals output by the magnetic chips 10.

[0046] In this embodiment, the shortest direction among the first coil 7, the second coil 8, and the detection module is defined as the height direction. One bottom surface of the first coil 7 is attached to one side surface of the detection module, and one bottom surface of the second coil 8 is attached to the other side surface of the detection module. At this time, it is equivalent to vertically placing two excitation coils (that is, the first coil 7 and the second coil 8) inside the detection probe 6 and horizontally placing the detection module, and detecting the change of the spatial magnetic field parallel to the axial direction of the pipeline to be measured through the detection module.

[0047] In this embodiment, the detection section 2 further includes a plurality of detection probe brackets. The detection probe brackets can be made of polyurethane and have a certain flexibility. The bottom of the detection probe brackets is placed on the second cylinder 5. Each detection probe bracket corresponds to a detection probe 6. The detection probe 6 is installed on the detection probe bracket, and the detection probe bracket is installed on the second cylinder 5. That is, the bottom of the detection probe 6 is fixedly connected to the top of the detection probe bracket, and the bottom of the detection probe bracket is fixedly connected to the second cylinder 5. In this embodiment, bolts can be used to fixedly connect the detection probe 6 to the detection probe bracket and fixedly connect the detection probe bracket to the second cylinder 5 respectively.

[0048] In this embodiment, the detection section 2 further includes a plurality of wear-resistant pieces. The wear-resistant pieces can be ceramic wear-resistant pieces. Each wear-resistant piece corresponds to a detection probe 6. The wear-resistant piece is located at the top of the detection probe 6 and is fixedly installed on the detection probe 6. By providing the wear-resistant pieces, it is possible to prevent the detection probe 6 from directly contacting the inner wall of the pipeline to be measured, avoid abrasion of the detection probe 6, and improve the service life of the detection probe 6.

[0049] In this embodiment, there can be twelve detection probes 6. At this time, there are twelve groups of detection probes 6, detection probe brackets, and ceramic wear-resistant pieces connected in the same way, which are evenly distributed on the second cylinder 5 along the circumferential direction. Of course, twelve is only an example of this embodiment and should not be construed as a limitation of the protection scope.

[0050] In order to realize the movement of the magnetization section 1 and the detection section 2 in the pipeline to be measured, the magnetization section 1 of this embodiment further includes a first leather cup 11 and a second leather cup 12. The first leather cup 11 is fixedly connected to one end of the first cylinder 3, and the second leather cup 12 is fixedly connected to the other end of the first cylinder 3. The first leather cup 11 and the second leather cup 12 are in interference fit with the inner wall of the pipeline to be measured. At this time, driven by the transportation medium in the pipeline to be measured, the first leather cup 11 and the second leather cup 12 can drive the first cylinder 3 and the magnetization device 4 to move in the pipeline to be measured, realizing the movement of the magnetization section 1 in the pipeline to be measured.

[0051] Similarly, the detection section 2 of this embodiment further includes a third leather cup 13 and a fourth leather cup 14. The third leather cup 13 is fixedly connected to one end of the second cylinder 5, and the fourth leather cup 14 is fixedly connected to the other end of the second cylinder 5. The third leather cup 13 and the fourth leather cup 14 are in interference fit with the inner wall of the pipeline to be measured. At this time, driven by the transportation medium in the pipeline to be measured, the third leather cup 13 and the fourth leather cup 14 can drive the second cylinder 5, the detection probe 6, the detection probe bracket, and the wear-resistant piece to move in the pipeline to be measured, realizing the movement of the detection section 2 in the pipeline to be measured.

[0052] In order to accurately locate a defect when it is detected, the detection section 2 of this embodiment further includes an odometer wheel 15, which is used to record the mileage of the detection section 2, so that when the detection probe 6 in the detection section 2 outputs an abnormal voltage signal, indicating that there is a defect at this time, the defect location can be located according to the mileage.

[0053] Based on the above structure, as Figure 3 shown, when the in-pipe inspection device for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current of this embodiment performs defect detection on the pipeline to be measured, first, the magnetization section 1 is moved along the scanning direction to the A position section located inside the pipeline to be measured. The magnetization section 1 magnetizes the pipeline to be measured, magnetizing the pipeline to be measured from an unknown magnetization state to a magnetic saturation state, and stopping magnetization after the pipeline to be measured is in the magnetic saturation state. The pipeline to be measured starts to demagnetize, so that the magnetization intensity of the pipeline to be measured decreases from the saturation magnetization intensity to the residual magnetization intensity, that is, the pipeline to be measured is successively in the unknown magnetization, saturation magnetization, and residual magnetization states. Then, under the action of the medium pressure difference, the magnetization section 1 moves to the next pipe section position, driving the detection section 2 to move along the scanning direction to the A position section located inside the pipeline to be measured. The detection section 2 detects the defects of the pipeline to be measured. The defects include inner surface defects and outer surface defects, and the defect detection of each position section of the pipeline to be measured is carried out in turn.

[0054] As Figure 4 shown, the working process of the in-pipe inspection device for oil and gas pipelines based on the coupling effect of residual magnetism and eddy current of this embodiment includes:

[0055] (1) The magnetization section 1 and the detection section 2 enter the pipeline to be measured successively.

[0056] (2) After the magnetization section 1 is located inside the pipeline to be measured, the pipeline to be measured is magnetized to the fully saturated state (i.e., the magnetic saturation state), eliminating the non-uniformity of the relative magnetic permeability of the pipeline to be measured. Specifically, the magnetization section 1 fully magnetizes the pipeline to be measured with unknown magnetization. As the magnetic field strength H of the external space magnetic field applied by the magnetization section 1 increases, the magnetization intensity M inside the pipeline to be measured will increase along the Figure 5 0AB curve in, until reaching the magnetic saturation state B. At this time, even if the magnetic field strength H is further increased, the magnetization state of the pipeline to be measured basically remains unchanged, and all positions of the pipeline to be measured reach the saturated magnetization state (i.e., the magnetic saturation state).

[0057] (3) When the pipeline to be measured reaches the magnetic saturation state, the magnetization section 1 passes through, removes the applied external space magnetic field, and stops magnetization, so that the magnetization intensity of the pipeline to be measured decreases to the residual magnetization intensity. Specifically, after the magnetization section 1 passes through, the external space magnetic field strength of the pipeline to be measured is zero. Due to the hysteresis phenomenon, the magnetization intensity inside the pipeline to be measured is not zero, but equal to the residual magnetization intensity, as Figure 5As shown, when the magnetization section 1 stops magnetization, that is, when the externally applied spatial magnetic field is no longer applied, the magnetization curve does not return along the original initial magnetization curve (OAB curve) starting from point B. This indicates that the change in magnetization intensity M lags behind the change in magnetic field intensity H. This phenomenon is called magnetic hysteresis. When the magnetic field intensity H decreases to zero, the magnetization intensity M is not zero but equal to the residual magnetization intensity M r .

[0058] (4) The detection section 2 enters. The five magnetic chips 10 of the detection probe 6 detect the spatial magnetic field signals at five positions perpendicular to the axial direction of the pipeline to be measured and output analog signals (i.e., voltage signals) of the magnetic field change. One magnetic chip 10 corresponds to one position. The residual magnetism of the pipeline and the eddy current generated by the detection probe 6 couple to generate a coupled magnetic field. Five magnetic chips 10 are arranged perpendicular to the detection direction inside each detection probe 6, and the magnetic chips 10 detect the change in the coupled magnetic field in the pipeline to be measured. When there is no defect in the pipeline to be measured, the detection probe 6 detects that the spatial coupled magnetic field intensity is B Ec +B Mr , B Ec is the magnetic field intensity corresponding to the eddy current field when there is no defect, and B Mr is the magnetic field intensity corresponding to the residual magnetism when there is no defect. When there is a defect in the pipeline to be measured, the detection probe 6 detects that the spatial coupled magnetic field intensity is B Ec +B Ec-crack +B Mr +B Mr-crack , B Ec-crack is the magnetic field intensity corresponding to the eddy current field when there is a defect, and B Mr-crack is the magnetic field intensity corresponding to the residual magnetism when there is a defect. The five magnetic chips 10 respectively detect the magnetic field changes at five adjacent positions and output analog voltage signals through five channels, as Figure 6 shown. It is judged whether there is a defect in the pipeline to be measured according to the change in the spatial coupled magnetic field intensity. That is, if the voltage signals collected by the magnetic chips 10 are abnormal, it means that the spatial coupled magnetic field intensity has changed, indicating that there is a defect at this time.

[0059] (5) Convert the analog signal into a digital signal and calculate the direction of the pipeline crack through the time difference of the signal change. The PC terminal processes and analyzes the multi-channel voltage signals collected to obtain the defect information of the oil and gas pipeline. The defect direction is judged according to the time difference of the signals output from the five channels and the moving speed of the detection probe 6, and the defect depth is judged according to the amplitudes of the signals output from the five channels.

[0060] The defect direction θ can be expressed by the following formula:

[0061]

[0062] where, represents the moving speed of the detection section; Δt represents the time difference of the output signals of the magnetic chips 10; l represents the spacing of the magnetic chips 10.

[0063] It should be noted that since there are 5 magnetic chips 10 in this embodiment, it is possible that the voltage signals of some of the sensors change or the voltage signals of all the sensors change. In this case, the first magnetic chip 10 and the last magnetic chip 10 among the magnetic chips with changed signals are selected, the time difference between the first magnetic chip 10 and the last magnetic chip 10 is calculated as Δt, and the spacing between the first magnetic chip 10 and the last magnetic chip 10 is calculated as l. The depth of the defect can be determined by any existing method according to the amplitudes of the output signals of the five channels, which will not be elaborated here.

[0064] It can be completed by any existing method and will not be elaborated here.

[0065] In this embodiment, after magnetizing the pipeline to be measured to the magnetic saturation state, the magnetization is stopped. At this time, the pipeline to be measured is under the condition of residual magnetism, which can eliminate the influence of the non-uniform relative magnetic permeability on pipeline detection and reduce the missed detection and false detection of defects caused by the non-uniform relative magnetic permeability. In addition, the detection probe 6 of the array sensor is used to detect defects such as cracks in the pipeline. Using an array sensor instead of simply placing the probe in a full circle can save a large amount of space, reduce voids, increase the scanning area in the pipeline, and can calculate the defect direction according to the signal time difference and running speed.

[0066] The primary magnetic field generated by the horizontally placed excitation coil generates an eddy current magnetic field J in the defect-free specimen 1 , generates an eddy current magnetic field J in the inner surface defect specimen 2 , generates an eddy current magnetic field J in the outer surface defect specimen 1 . The eddy current magnetic field of the outer surface defect specimen does not change compared with the eddy current magnetic field of the defect-free specimen. Therefore, a single eddy current detection technology does not have the ability to detect outer surface defects of pipelines. As Figure 7 (a) shows, when there is no residual magnetism condition (that is, when the magnetization intensity of the pipeline to be measured is equal to the residual magnetization intensity), the detection module detects the spatial magnetic field intensity. When there is no defect, the axial magnetic field intensity of the pipeline Bx = 0, and the radial magnetic field intensity of the pipeline By = By Ec , By Ec is the radial magnetic field intensity generated by the magnetic field corresponding to the eddy current field when there is no defect; when there is an inner surface defect, the change amount of the axial magnetic field intensity of the pipeline ΔBx = Bx Ec-incrack , the change amount of the radial magnetic field intensity of the pipeline ΔBy = By Ec - By Ec-incrack , Bx Ec-incrack is the axial magnetic field intensity generated by the magnetic field corresponding to the eddy current field when there is an inner surface defect, By Ec-incrackis the radial magnetic field intensity generated by the magnetic field corresponding to the eddy current field when there is an inner surface defect; when there is an outer surface defect, due to the skin effect, the outer surface defect does not change the eddy current field, so there is no change in the spatial magnetic field intensity, which also means that the outer surface defect cannot be detected. As Figure 7 (b) shows that after the pipeline is saturated magnetized in this embodiment and the magnetization device 4 is withdrawn (moved from position a to position b), at this time, the pipeline at position a is under the condition of residual magnetism and has a residual magnetism Mr. On this premise, as Figure 7 (c) shows, the detection module detects the spatial magnetic field intensity. When there is no defect, the axial coupling magnetic field intensity of the pipeline Bx = Bx Mr , the radial coupling magnetic field intensity of the pipeline By = By Ec +By Mr , Bx Mr is the axial magnetic field intensity generated by the magnetic field corresponding to the residual magnetism when there is no defect, By Mr is the radial magnetic field intensity generated by the magnetic field corresponding to the residual magnetism when there is no defect; when there is an inner surface defect, the change in the axial coupling magnetic field intensity of the pipeline ΔBx = Bx Mr -

[0067] (Bx Mr-incrack +Bx Ec-incrack ), ΔBy = By Ec +By Mr -(By Ec-incrack +By Mr-incrack ), Bx Mr-incrack is the axial magnetic field intensity generated by the magnetic field corresponding to the residual magnetism when there is an inner surface defect, By Mr-incrack is the radial magnetic field intensity generated by the magnetic field corresponding to the residual magnetism when there is an inner surface defect; when there is an outer surface defect, the change in the axial coupling magnetic field intensity of the pipeline △Bx = Bx Mr -

[0068] (Bx Mr-excrack +Bx Ec-excrack ), △By = By Ec +By Mr -(By Ec-excrack +By Mr-excrack ), Bx Mr-excrack is the axial magnetic field intensity generated by the magnetic field corresponding to the residual magnetism when there is an outer surface defect, Bx Ec-excrack is the axial magnetic field intensity generated by the magnetic field corresponding to the eddy current field when there is an outer surface defect, By Ec-excrack is the radial magnetic field intensity generated by the magnetic field corresponding to the eddy current field when there is an outer surface defect, By Mr-excrackIt is the radial magnetic field intensity generated by the residual magnetic field corresponding to the magnetic field when there are external surface defects. It is not difficult to find that when the pipeline is under the condition of residual magnetism, a magnetic field change will also occur when there are external surface defects, which means that the device of this embodiment can be used to detect external surface defects. At the same time, the detected magnetic field change of the coupling between the pipeline residual magnetism and the eddy current field is larger than the magnetic field change generated by a single eddy current field, so it is more sensitive.

[0069] This embodiment provides a device for improving the eddy current detection performance based on the residual magnetic effect, which can improve the sensitivity of pipeline eddy current detection based on the residual magnetic effect, eliminate the non-uniform relative magnetic permeability in the pipeline, and will not be interfered by the magnetic field inside the material, and can measure the magnetic field value and defect signal more accurately. The residual magnetic field is coupled with the eddy current field, solving the defect that the eddy current cannot detect external surface defects due to the skin effect, and the spatial magnetic field change at the defect is larger, improving the internal eddy current detection performance of oil and gas pipeline defects. The array of sensors can collect defect signals in multiple channels, making it easier to quantify defect characteristics.

[0070] Embodiment 2

[0071] This embodiment provides an internal detection method for oil and gas pipelines based on the coupling of residual magnetism and eddy current. It works based on the internal detection device for oil and gas pipelines based on the coupling of residual magnetism and eddy current described in Embodiment 1, and includes: using a magnetization section to saturate the magnetization of the pipeline to be measured, and stopping magnetization after the pipeline to be measured is in a magnetically saturated state, so that the magnetization intensity of the pipeline to be measured drops from the saturated magnetization intensity to the residual magnetization intensity; using a detection section to generate an induced eddy current field in the pipeline to be measured, and detecting the defects of the pipeline to be measured based on the coupling magnetic field formed by the residual magnetization intensity and the induced eddy current field; the defects include internal surface defects and external surface defects.

[0072] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should all be considered as the scope described in this specification.

[0073] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention.

[0074] The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An oil and gas pipeline internal detection device based on residual magnetism and eddy current coupling, characterized in that: include: A magnetizing section and a detecting section; the magnetizing section and the detecting section are fixedly connected; The magnetization node is located in the measured pipeline; the magnetization node is used to saturate magnetize the measured pipeline, and stops magnetizing after the measured pipeline is in a magnetic saturation state; when the magnetization node stops magnetizing, the measured pipeline is demagnetized, and the magnetization intensity of the measured pipeline decreases from the saturation magnetization intensity to the residual magnetization intensity; The detection section is located in the pipeline to be tested; the detection section is used to generate an induced eddy current field in the pipeline to be tested when the magnetization intensity of the pipeline to be tested drops to the residual magnetization intensity, and detect defects of the pipeline to be tested based on the coupled magnetic field formed by the residual magnetization intensity and the induced eddy current field; the defects include inner surface defects and outer surface defects; The magnetization node and the detection node are arranged at intervals.

2. The oil and gas pipeline internal detection device based on residual magnetism and eddy current coupling according to claim 1 is characterized in that: The magnetization section includes a first cylinder and a magnetization device; the magnetization device includes a plurality of magnetization components, each of which is mounted on the first cylinder, and the plurality of magnetization components are distributed in a circumferential array around the first cylinder; the magnetization components are used to magnetize the measured pipeline.

3. The oil and gas pipeline internal detection device based on residual magnetism and eddy current coupling according to claim 2 is characterized in that: The magnetization component includes a U-shaped magnetic yoke, and the first magnetic pole and the second magnetic pole of the U-shaped magnetic yoke are in contact with the inner surface of the measured pipe; a coil is installed on the U-shaped magnetic yoke, and when a direct current is passed through the coil, the measured pipe is magnetized; or, permanent magnets are installed on the first magnetic pole and the second magnetic pole to magnetize the measured pipe.

4. The oil and gas pipeline internal detection device based on residual magnetism and eddy current coupling according to claim 1 is characterized in that: The detection section includes a second cylinder and a plurality of detection probes; each of the detection probes is mounted on the second cylinder, and the plurality of detection probes are distributed in a circumferential array around the second cylinder.

5. The oil and gas pipeline internal detection device based on residual magnetism and eddy current coupling according to claim 4 is characterized in that: The detection probe comprises a first coil, a detection module and a second coil, wherein the detection module is located between the first coil and the second coil; the first coil and the second coil are both attached to the detection module; The first coil and the second coil are used to be supplied with an alternating current to generate an induced eddy current field in the measured pipeline; The detection module is used to detect the coupled magnetic field formed by the residual magnetization intensity and the induced eddy current field, and output a voltage signal.

6. The oil and gas pipeline internal detection device based on residual magnetism and eddy current coupling according to claim 5 is characterized in that: The first coil and the second coil are both annular coils wound by conducting wires; the detection module comprises a PCB circuit board and a plurality of magnetic chips, and the plurality of magnetic chips are fixedly mounted on the PCB circuit board.

7. The oil and gas pipeline internal detection device based on residual magnetism and eddy current coupling according to claim 4 is characterized in that: The detection section also includes a plurality of detection probe brackets; each of the detection probe brackets corresponds to one detection probe; the detection probe is mounted on the detection probe bracket, and the detection probe bracket is mounted on the second cylinder.

8. The oil and gas pipeline internal detection device based on residual magnetism and eddy current coupling according to claim 7 is characterized in that: The detection section also includes a plurality of wear-resistant sheets; each of the wear-resistant sheets corresponds to one detection probe; the wear-resistant sheet is located on the top of the detection probe, and the wear-resistant sheet is fixedly mounted on the detection probe.

9. A method for detecting inside an oil and gas pipeline based on the coupling of residual magnetism and eddy current, based on the detection device for detecting inside an oil and gas pipeline based on the coupling of residual magnetism and eddy current as claimed in any one of claims 1 to 8, characterized in that: include: The measured pipeline is saturated magnetized by using a magnetizing node, and the magnetization is stopped after the measured pipeline is in a magnetic saturation state, so that the magnetization intensity of the measured pipeline decreases from the saturation magnetization intensity to the residual magnetization intensity; an induced eddy current field is generated in the measured pipeline by using a detection node, and defects of the measured pipeline are detected based on the coupled magnetic field formed by the residual magnetization intensity and the induced eddy current field; the defects include inner surface defects and outer surface defects.

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