A method for locating corrosion defect points in long-distance pipeline magnetic flux leakage internal detection based on double-side projection correction method

Abstract

The application relates to a long-distance pipeline magnetic flux leakage internal detection corrosion defect point excavation positioning method based on a double-side projection correction method, which comprises the following steps: measuring and collecting field pipeline corrosion point related data; modeling four important parameters of defect point pipeline section elevation, buried depth, magnetic flux leakage detection mileage and reference point ground surface positioning mileage respectively to obtain four models; calculating the ground surface positioning distance of the pipeline defect point from the double-side nearest reference point of the magnetic flux leakage internal detection pipeline defect point by using the double-side projection correction method; and obtaining the specific positioning position of the pipeline defect point by using a ground surface pull rope measurement method. The double-side orthogonal projection correction method has good use effect in the excavation verification and defect repair process of R-N crude oil pipeline corrosion defect points, and can be popularized in the excavation verification and defect repair work of R-N crude oil pipelines and R-K crude oil pipelines in the later period.

Description

Technical Field

[0001] This invention relates to a method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method, which belongs to the field of pipeline internal inspection technology. Background Technology

[0002] Currently, the most commonly used methods for correcting the location error of pipeline corrosion defects based on magnetic flux leakage detection in engineering practice include the surface measuring tape method, the handheld GPS positioning method, the RTK-GPS positioning method, and the gap interpolation method, which are described in detail below:

[0003] Surface measuring tape method

[0004] During the excavation and location of pipeline corrosion defects, the conventional method is to locate the defect points by measuring the relative distance between the mileage of the ground marker for the pipeline leakage magnetic field test and the mileage of ground reference features (such as test piles, valves, tees, etc.) using a ground tape measure. After excavation, the pipeline corrosion defects are then precisely located based on the circumferential weld number and distance in the pipeline welding table.

[0005] Since the zero point of the pipeline magnetic flux leakage detection mileage is generally the first valve at the exit of the ball launch tube, and the zero point of the ground test stake mileage is generally the insulation joint of the pipeline at the exit, when the pipeline traverses complex terrain with U-shaped crossings or C-shaped bends, the distance difference between the unknown pipeline corrosion defect magnetic flux leakage detection mileage and the known ground marker mileage will increase with the increase of pipeline mileage. The surface measuring tape method simulates the one-dimensional pipeline mileage along the pipeline centerline, and cannot accurately simulate the three-dimensional actual pipeline route. Therefore, the surface measuring tape method has a large error and it is difficult to find the corresponding pipeline corrosion defect point in the magnetic flux leakage detection result data table in one go.

[0006] Handheld GPS positioning method

[0007] Because the corrosion defect points provided in the pipeline magnetic flux leakage (MFLL) internal detection report include latitude and longitude location information, handheld GPS positioning is sometimes used to locate pipeline corrosion defects during on-site excavation. There are two main factors affecting the location of pipeline corrosion defects using a handheld GPS locator: First, when there are obstacles, signal towers, high-voltage lines, and fiber optic cables at the pipeline location site, the satellite signal received by the handheld GPS locator is weak or unstable, affecting positioning accuracy. Second, the latitude and longitude format given in the MFLL internal detection report is in 8-degree decimal places, while handheld GPS locators can generally only be set to 6-degree decimal places. If a handheld GPS is used to locate the pipeline corrosion defect points based on the latitude and longitude of the MFLL internal detector, positioning measurement errors can easily occur due to the difference in positioning accuracy between the two positioning systems.

[0008] To avoid errors caused by weak or strong signal interference from handheld GPS locators, a "X" shaped positioning method is typically used on-site. This involves initially locating the corrosion defect near the pipe cover using a handheld GPS locator, then using that point as the center to perform multiple positioning calibrations in the other eight directions of the "X". Finally, the location of the pipeline is combined with the information from a pipeline detector to select a location for excavation. While the "X" shaped positioning method is simple to operate and partially avoids the problem of weak or unstable satellite signal reception from handheld GPS locators, it cannot avoid positioning measurement errors caused by differences in latitude and longitude accuracy between the two positioning systems. Furthermore, if the initial positioning during excavation is inaccurate, it is difficult to calibrate the positioning during the second excavation.

[0009] RTK-GPS positioning method

[0010] The RTK-GPS positioning method uses one receiver as a base station and another as a rover. The base station continuously observes satellite GPS signals to center and level the control point, while simultaneously transmitting the observation data to the rover in real time via radio. The rover receives satellite GPS signals while simultaneously receiving data transmitted from the base station via radio, and then calculates the three-dimensional coordinates and accuracy of the target point in real time based on the principle of relative positioning. The base station control point can be set up at a known or unknown GPS point; however, setting it up at an unknown GPS point is recommended. This is because when choosing an unknown GPS point, the base station can be set up at an ideal location in the center of the survey area at a certain height with a wide field of view. Setting up the base station at a higher position in the center of the survey area not only ensures a longer radio signal transmission distance and better satellite signal reception quality, but also provides better coverage of the entire survey area, reducing the number of base station setups required. When using a rover for observation, a tripod should be used for centering and leveling. Each sampling interval should be 1-5 seconds, the number of observation epochs should be greater than 20, the number of effective satellites should be greater than 5, and the difference in plane coordinates between measurements should not exceed 4 cm. Generally, the positional positioning error of the RTK-GPS method is less than 0.1 m, and the elevation positioning error is less than 0.3 m.

[0011] When using the RTK-GPS positioning method to locate corrosion defects in pipelines via magnetic flux leakage detection, the positioning is generally achieved by combining RTK elevation measurements with pipeline depth measurements using a pipeline detector. Elevation and depth measurements are performed simultaneously, with data recorded point by point. First, the RTK dynamic differential method is used for elevation measurement, taking measurements every 10 meters along the pipeline axis, with 1-meter intervals used at relatively low points. When using the RTK positioning method for elevation measurement, horizontal error must be considered, ensuring that the measurement range fully encompasses the lowest point of the pipeline. Then, the transmitter of the pipeline detector applies a specific frequency electromagnetic wave signal to the pipeline under inspection. The electromagnetic wave signal forms a current loop through the ground and creates an electromagnetic field around the pipeline. A receiver then receives the magnetic field strength around the pipeline, thereby measuring the pipeline depth matching the transmission frequency to determine the precise location of the pipeline.

[0012] Difference interpolation

[0013] The pipeline defect location correction method given in SY / T 6825-2011 "Qualification of Pipeline Internal Inspection Systems" is the gap interpolation method. The basic steps of this method are: first, identify the pipeline defect to be excavated and the detection mileage of the nearest known upstream and downstream reference points in the magnetic flux leakage internal inspection report, and calculate the distance between the defect and the nearest known upstream and downstream reference points. Then, distinguish and calibrate the above-ground distances from the defect to the upstream and downstream reference points. There will be a difference or overlap between the above-ground measured defect location and the location calculated based on the detection mileage. The difference and overlap length are affected by the accuracy of the above-ground measurement; generally, a difference of 0-1% between the above-ground distances from the defect to the two reference points is considered normal. Finally, interpolate the difference value to the detection mileage between the nearest known upstream and downstream reference points, and correct the location error using the same ratio (53% and 47%) according to the "percentage rule".

[0014] This method is based on the surface measuring tape method, which comprehensively considers the leakage magnetic flux detection mileage and the surface measurement mileage when correcting positioning errors. However, the correction percentage data used in the positioning error correction has uncertainty. The elevation and burial depth of each pipe section where the defect point is located are different, and the difference values ​​measured by the measuring tape method vary greatly. The 53% and 47% correction percentages cannot be applied to all engineering cases.

[0015] Due to factors such as undulating terrain above the pipeline, flexible pipeline laying, pipeline bend curvature, and misplacement of the AGM positioning box, there is usually an error between the mileage measured on the ground and the mileage detected by magnetic flux leakage (MFL) testing. During MFL testing, the accuracy of the mileage measurement wheel of the MFL detector is affected by factors such as manufacturing differences, complex working conditions of the pipeline inner wall, detector operating speed, physical properties of the pipeline medium, and changes in elevation along the pipeline. The mileage measurement will also have errors, and the farther the corrosion defect point is from the launching tube, the greater the cumulative error.

[0016] There are two main factors affecting the accuracy of excavation and location of pipeline corrosion defects: surface measurement positioning error and the measurement error of the odometer wheel of the magnetic flux leakage (MFL) detector. The odometer wheel measurement error becomes a fixed error at the end of the MFL detection operation, unless the same MFL detector is used to perform multiple MFL detection operations under similar conditions on the same pipeline for odometer wheel positioning calibration. Therefore, studying the odometer wheel measurement error of the MFL detector is not very meaningful; the focus should be on reducing surface measurement positioning errors. Summary of the Invention

[0017] To address the shortcomings of existing technologies, this invention provides a method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method for detecting internal corrosion defects using magnetic flux leakage.

[0018] This invention compares and analyzes the problems of four pipeline defect point location and correction methods: surface measuring tape method, handheld GPS positioning method, RTK-GPS positioning method, and gap interpolation method. It finds that the surface location error of pipeline defect points mainly comes from the elevation of the defect point pipe section, burial depth, magnetic flux leakage detection mileage, and surface location mileage of the reference point. These four important parameters are modeled and the bilateral orthogonal projection correction method is used to improve the excavation and location accuracy of corrosion defect points detected by magnetic flux leakage in long-distance pipelines.

[0019] Terminology Explanation:

[0020] 1. Elevation: The elevation of a long-distance oil pipeline refers to the absolute elevation of the pipeline, that is, the distance from the pipeline centerline to the reference surface. This reference surface is usually a specific leveling datum, such as sea level or a specific elevation reference surface.

[0021] 2. Burial depth: The burial depth of a long-distance oil pipeline refers to the vertical distance between the bottom of the pipeline and the ground surface when the pipeline is buried underground. It is usually half of the outer diameter of the pipeline plus the sum of the reserved thickness, ground load, groundwater level and underground engineering layout requirements.

[0022] 3. Magnetic flux leakage detection mileage: The magnetic flux leakage detection mileage of long-distance oil pipelines refers to the length range in which magnetic flux leakage detection technology is applied in long-distance oil pipelines.

[0023] 4. Reference point surface positioning mileage: The reference point surface positioning mileage of a long-distance oil pipeline refers to the reference point selected during pipeline design and construction to determine parameters such as pipeline elevation and burial depth. This reference point is usually a point with a known elevation. Then, through measurement and calculation, the pipeline's elevation and burial depth parameters are determined. The surface positioning mileage of this reference point refers to the location coordinates and mileage value of that point.

[0024] The technical solution of this invention is as follows:

[0025] A method for locating corrosion defects in long-distance pipelines using magnetic flux leakage detection based on bilateral projection correction includes:

[0026] Measure and collect relevant data on corrosion points in the pipelines on site;

[0027] The four important parameters of defect point pipe section elevation, burial depth, magnetic flux leakage detection mileage and reference point surface positioning mileage are modeled separately to obtain four models;

[0028] Using the bilateral projection correction method, the ground location distance between the pipeline defect point and the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage is calculated;

[0029] The exact location of the pipeline defect was determined by using a ground measuring tape.

[0030] According to a preferred embodiment of the present invention, the relevant data of the on-site pipeline corrosion points include the clock position, defect type, wall thickness loss ratio, magnetic flux leakage appearance, magnetic flux leakage detection mileage, pipeline burial depth near the defect point, pipeline burial depth of the nearest reference point on both sides of the defect point, and elevation of the nearest reference point on both sides of the defect point.

[0031] According to a preferred embodiment of the present invention, the four important parameters of the defect point pipe section elevation, burial depth, magnetic flux leakage detection mileage, and reference point surface positioning mileage are respectively modeled to obtain four models, including: a model constructed when the elevation increases and the burial depth decreases; a model constructed when the elevation decreases and the burial depth decreases; a model constructed when the elevation increases and the burial depth increases; and a model constructed when the elevation decreases and the burial depth increases.

[0032] According to a preferred embodiment of the present invention, in the four models, line segment X1-X2 represents the actual surface section corresponding to the short-distance defect point pipe segment, line segment Y1-Y2 represents the short-distance defect point pipe segment, and line segment Z1-Z2 represents the short-distance orthogonal projection section; point P is the intersection of the short-distance surface line and the orthogonal projection baseline, point M is the intersection of the short-distance defect point pipe segment and the orthogonal projection baseline, and point Q is the intersection of the short-distance surface line and the short-distance defect point pipe segment; ∠α is the angle between the short-distance surface line and the orthogonal projection baseline, and ∠β is the angle between the short-distance surface line and the short-distance defect point pipe segment; X0 is the actual surface location mileage corresponding to the pipeline defect point detected by magnetic flux leakage, X1 is the actual surface location mileage corresponding to the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and X2 is the actual surface location mileage corresponding to the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage; Y0 is the detection mileage of the pipeline defect point detected by magnetic flux leakage. Mileage: Y1 is the detection mileage of the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and Y2 is the detection mileage of the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage; Z0 is the orthogonal projection mileage of the pipeline defect point detected by magnetic flux leakage, and Z1 is the orthogonal projection mileage of the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and Z2 is the orthogonal projection mileage of the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage; X0-Z0 is the elevation of the pipeline defect point detected by magnetic flux leakage, X1-Z1 is the elevation of the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and X2-Z2 is the elevation of the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage; X0-Y0 is the burial depth of the pipeline defect point detected by magnetic flux leakage, X1-Y1 is the burial depth of the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and X2-Y2 is the burial depth of the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage.

[0033] For cases where the burial depth decreases with increasing elevation and vice versa, the formula for expressing the elevation at the pipeline defect point is as follows:

[0034]

[0035] For cases where the burial depth increases with increasing elevation and vice versa, the formula for expressing the elevation at the pipeline defect point is as follows:

[0036]

[0037] Among them, X1-Z1 and X2-Z2 are obtained by measuring the elevation of the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage, X1-Y1 and X2-Y2 are obtained by measuring the burial depth of the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage, and Y0-Y1 and Y2-Y1 are obtained directly from the magnetic flux leakage detection report data.

[0038] According to a preferred embodiment of the present invention, for the cases of increasing elevation and decreasing burial depth, and increasing elevation and increasing burial depth, the surface positioning distance X0-X1 from the pipeline defect point to the nearest reference point on the left side of the pipeline defect point detected by magnetic flux leakage is expressed by the following formula:

[0039]

[0040] The formula for the distance X2-X0 between the pipeline defect point and the nearest reference point on the right side of the pipeline defect point detected by magnetic flux leakage is:

[0041]

[0042] According to a preferred embodiment of the present invention, for the cases of decreasing elevation and decreasing burial depth, and decreasing elevation and increasing burial depth, the surface positioning distance X0-X2 from the pipeline defect point to the nearest reference point on the right side of the pipeline defect point detected by magnetic flux leakage is expressed by the following formula:

[0043]

[0044] The formula for the distance X1-X0 between the pipeline defect point and the nearest reference point on the left side of the pipeline defect point detected by magnetic flux leakage is:

[0045]

[0046] Among them, X1-Z1 and X2-Z2 are obtained by measuring the elevation of the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage, X0-Z0 is obtained by calculating the elevation of the pipeline corrosion point above, and X1-X2 is obtained by directly measuring the distance to the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage.

[0047] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of a method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method for detecting internal corrosion defects.

[0048] A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of a method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method for detecting internal corrosion defects using magnetic flux leakage.

[0049] A system for locating corrosion defects in long-distance pipelines based on the bilateral projection correction method, comprising:

[0050] The data collection module is configured to measure and collect data related to corrosion points on the pipeline in the field.

[0051] The model building module is configured to model the four important parameters of defect point pipe section elevation, burial depth, magnetic flux leakage detection mileage and reference point ground location mileage respectively, resulting in four models;

[0052] The surface positioning distance calculation module is configured to: calculate the surface positioning distance of the pipeline defect point from the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage using the bilateral projection correction method;

[0053] The specific location acquisition module is configured to obtain the specific location of the pipeline defect point by using the ground measuring tape method.

[0054] The beneficial effects of this invention are as follows:

[0055] The bilateral orthogonal projection correction method has shown good results in the excavation verification and repair of corrosion defects in the RN crude oil pipeline. This method can be promoted in the later stages of excavation verification and defect repair for both the RN and RK crude oil pipelines. When using RTK-GPS positioning combined with surface measuring tape for excavation positioning, the positioning error for 12 corrosion defects in the RK crude oil pipeline ranged from -36.746m to 14.007m, with a total excavation positioning and repair time of 79 days. When using the bilateral orthogonal projection correction method combined with surface measuring tape for excavation positioning, the positioning error for 10 corrosion defects in the RN crude oil pipeline ranged from -6.290m to 7.943m, with a total excavation positioning and repair time of 44 days. Using the bilateral orthogonal projection correction method to locate corrosion defects based on pipeline magnetic flux leakage detection not only significantly improves the accuracy of excavation positioning but also greatly saves on-site construction time and pipeline maintenance costs. Attached Figure Description

[0056] Figure 1 A schematic diagram of the model constructed for increasing elevation and decreasing burial depth;

[0057] Figure 2 A schematic diagram of the model constructed for the reduction of elevation and burial depth;

[0058] Figure 3 A schematic diagram of the model constructed when the elevation and burial depth increase;

[0059] Figure 4 A schematic diagram of the model constructed when the elevation decreases and the burial depth increases. Detailed Implementation

[0060] The present invention will be further defined below with reference to the accompanying drawings and embodiments, but is not limited thereto.

[0061] Example 1

[0062] A method for excavation and location of corrosion defects in long-distance pipelines based on bilateral projection correction for internal detection of magnetic flux leakage includes:

[0063] Measure and collect relevant data on corrosion points in the pipelines on site;

[0064] The four key parameters—defect point pipe section elevation, burial depth, magnetic flux leakage detection mileage, and reference point surface location mileage—were modeled separately, resulting in four models; the diagrams of the four models are shown below. Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown;

[0065] The ground location distance between the pipeline defect point and the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage is calculated using the two-sided projection correction method.

[0066] Based on the relative distance between the mileage of the ground markers used for pipeline magnetic flux leakage detection and the mileage of ground reference features (such as test piles, valves, tees), the location of the defect points requiring repair is determined using a ground measuring tape. After excavation, the pipeline corrosion defects are precisely located according to the circumferential weld numbers and distances in the pipeline welding table, thus obtaining the specific location of the pipeline defect points.

[0067] Example 2

[0068] The difference between the method for locating corrosion defects in long-distance pipelines based on the bilateral projection correction method described in Example 1 and the method for detecting corrosion defects in long-distance pipelines using magnetic flux leakage is as follows:

[0069] Data related to pipeline corrosion points on-site includes clock positions, defect types, wall thickness loss ratios, magnetic flux leakage appearances, magnetic flux leakage detection mileage, surface location mileage, corrosion point burial depth, magnetic flux leakage detection mileage of the 12 pipeline defect points detected by magnetic flux leakage detection on the RK line and 10 pipeline defect points detected by magnetic flux leakage detection on the RN line, and elevations of the nearest reference points on both sides. The magnetic flux leakage detection mileage of the corrosion points and the nearest reference points on both sides of the corrosion points was obtained directly from the magnetic flux leakage detection report data. The pipeline burial depth near the corrosion points and the pipeline burial depth of the nearest reference points on both sides of the defect points were obtained by measuring the average burial depth of the pipeline within ±10m of the target point using a Radiation Pipeline Probe. The elevations of the nearest reference points on both sides of the corrosion points were obtained from the pipeline elevation data along the pipeline route in the pipeline as-built documentation.

[0070] The four important parameters of defect point pipe section elevation, burial depth, magnetic flux leakage detection mileage, and reference point surface positioning mileage were modeled to obtain four models, including: the model constructed when elevation increases and burial depth decreases; the model constructed when elevation decreases and burial depth decreases; the model constructed when elevation increases and burial depth increases; and the model constructed when elevation decreases and burial depth increases.

[0071] In the four models, line segment X1-X2 represents the actual surface section corresponding to the short-distance defect point pipe segment, line segment Y1-Y2 represents the short-distance defect point pipe segment, and line segment Z1-Z2 represents the short-distance orthogonal projection section; point P is the intersection of the short-distance surface line and the orthogonal projection baseline, point M is the intersection of the short-distance defect point pipe segment and the orthogonal projection baseline, and point Q is the intersection of the short-distance surface line and the short-distance defect point pipe segment; ∠α is the angle between the short-distance surface line and the orthogonal projection baseline, and ∠β is the angle between the short-distance surface line and the short-distance defect point pipe segment; X0 is the actual surface location mileage corresponding to the pipeline defect point detected by magnetic flux leakage, X1 is the actual surface location mileage corresponding to the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and X2 is the actual surface location mileage corresponding to the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage; Y0 is the detection mileage of the pipeline defect point detected by magnetic flux leakage, and Y1 is the detection mileage of the pipeline defect point detected by magnetic flux leakage. Y1 is the detection mileage of the nearest reference point to the left side of the pipeline defect detected by magnetic flux leakage, and Y2 is the detection mileage of the nearest reference point to the right side of the pipeline defect detected by magnetic flux leakage; Z0 is the orthogonal projection mileage of the pipeline defect detected by magnetic flux leakage, Z1 is the orthogonal projection mileage of the nearest reference point to the left side of the pipeline defect detected by magnetic flux leakage, and Z2 is the orthogonal projection mileage of the nearest reference point to the right side of the pipeline defect detected by magnetic flux leakage; X0-Z0 is the elevation of the pipeline defect detected by magnetic flux leakage, X1-Z1 is the elevation of the nearest reference point to the left side of the pipeline defect detected by magnetic flux leakage, and X2-Z2 is the elevation of the nearest reference point to the right side of the pipeline defect detected by magnetic flux leakage; X0-Y0 is the burial depth of the pipeline defect detected by magnetic flux leakage, X1-Y1 is the burial depth of the nearest reference point to the left side of the pipeline defect detected by magnetic flux leakage, and X2-Y2 is the burial depth of the nearest reference point to the right side of the pipeline defect detected by magnetic flux leakage.

[0072] For the cases where the burial depth decreases as the elevation increases and vice versa, we can obtain the following results using trigonometric functions:

[0073]

[0074] or

[0075] Dividing the detected mileage Y2-M into segments Y1-M, Y0-Y1, and Y2-Y0, we can obtain:

[0076]

[0077] The formulas for expressing the unknown segments Y1-M and Y0-Z0 can be obtained as follows:

[0078]

[0079]

[0080] Dividing X0-Z0 into X0-Y0 and Y0-Z0, we get:

[0081]

[0082] Divide Y1-Z1 and Y2-Z2 into (X1-Z1)-(X1-Y1) and (X2-Z2)-(X2-Y2);

[0083] Therefore, for the cases where the burial depth decreases with increasing elevation and vice versa, the formula for expressing the elevation at the pipeline defect point is as follows:

[0084]

[0085] By applying theoretical calculations to determine the elevation of the pipeline defect point, it can be compared and calibrated with the actual measured elevation.

[0086] For cases where the burial depth increases with increasing elevation and increases with decreasing elevation, trigonometric functions can be used to obtain:

[0087]

[0088] or

[0089] Dividing the detected mileage Y1-M into segments Y1-Y0, Y0-Y2, and Y2-M yields:

[0090]

[0091] The formulas for expressing the unknown segments Y2-M and Y0-Z0 can be obtained as follows:

[0092]

[0093]

[0094] Dividing X0-Z0 into X0-Y0 and Y0-Z0, we get:

[0095]

[0096] Divide Y1-Z1 and Y2-Z2 into (X1-Z1)-(X1-Y1) and (X2-Z2)-(X2-Y2);

[0097] Therefore, for the cases where the burial depth increases with increasing elevation and the burial depth increases with decreasing elevation, the formula for expressing the elevation at the pipeline defect point is as follows:

[0098]

[0099] X1-Z1 and X2-Z2 are obtained by measuring the elevations of the nearest reference points on both sides of the pipeline defect point detected by magnetic flux leakage. X1-Y1 and X2-Y2 are obtained by measuring the burial depths of the nearest reference points on both sides of the pipeline defect point detected by magnetic flux leakage. Y0-Y1 and Y2-Y1 are obtained directly from the data in the magnetic flux leakage detection report. For the pipeline burial depth X0-Y0 at the pipeline defect point, since the variation in pipeline burial depth within ±10m of the corrosion point is small, the error generally will not exceed ±200mm, and this error can be reduced by measuring the average burial depth of the pipeline within ±5m of the corrosion point. Therefore, the calculated elevation at the pipeline defect point can be obtained through the above formula, and this calculated elevation can also be compared and calibrated with the actual measured elevation.

[0100] For the cases mentioned above, where the burial depth decreases with increasing elevation and vice versa, we can obtain the following results using trigonometric functions:

[0101]

[0102] Dividing X2-P into X1-P, X0-X1, and X2-X0, we get:

[0103]

[0104] The formula for expressing the unknown segment X1-P can be obtained from the above equation:

[0105]

[0106] Therefore, for the cases of increasing elevation and decreasing burial depth, and increasing elevation and increasing burial depth, the formula for the surface positioning distance X0-X1 from the pipeline defect point to the nearest reference point on the left side of the pipeline defect point detected by magnetic flux leakage is:

[0107]

[0108] The formula for the distance X2-X0 between the pipeline defect point and the nearest reference point on the right side of the pipeline defect point detected by magnetic flux leakage is:

[0109]

[0110] For the cases where the burial depth decreases as elevation decreases and the burial depth increases as elevation decreases, we can obtain the following results using trigonometric functions:

[0111]

[0112] Dividing X1-P into X2-P, X0-X2, and X1-X0, we get:

[0113]

[0114] The formula for expressing the unknown segment X2-P can be obtained from the above equation:

[0115]

[0116] The formula for the distance X0-X2 between the pipeline defect point and the nearest reference point on the right side of the pipeline defect point detected by magnetic flux leakage is:

[0117]

[0118] Therefore, for both cases where the elevation decreases and the burial depth increases, the formula for the surface positioning distance X1-X0 between the pipeline defect point and the nearest reference point on the left side of the pipeline defect point detected by magnetic flux leakage is:

[0119]

[0120] X1-Z1 and X2-Z2 are obtained by measuring the elevations of the nearest reference points on both sides of the pipeline defect point detected by magnetic flux leakage, X0-Z0 is obtained by calculating the elevation of the pipeline corrosion point mentioned earlier, and X1-X2 is obtained by directly measuring the distances to the nearest reference points on both sides of the pipeline defect point detected by magnetic flux leakage. Therefore, the surface location distance between the nearest reference points on both sides of the pipeline defect point can be obtained through the above formula.

[0121] The specific application of the method for locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method for internal detection of magnetic flux leakage is as follows:

[0122] During the excavation verification and repair of corrosion defects in the RK crude oil pipeline, the 12 pipeline defect points detected by magnetic flux leakage were located using the RTK-GPS positioning method combined with the surface measuring tape method. The location error data for the excavation verification of the 12 pipeline defect points detected by magnetic flux leakage in the RK crude oil pipeline are shown in Table 1.

[0123] Table 1

[0124]

[0125]

[0126] The positioning error of the 12 pipeline defect detection points in the RK crude oil pipeline using the RTK-GPS positioning method combined with the surface measuring rod method was between -36.746m and 14.007m, which is relatively large.

[0127] During the excavation verification and repair of corrosion defects in the RN crude oil pipeline, the location of 10 pipeline defects detected by magnetic flux leakage was determined using a combination of bilateral orthogonal projection correction and surface measuring. Table 2 shows the location error data for the 10 pipeline defects detected by magnetic flux leakage in the RN crude oil pipeline.

[0128] Table 2

[0129]

[0130] The positioning error of the 10 pipeline defect detection points within the magnetic flux leakage detection system along the RN line, using the bilateral orthogonal projection correction method combined with the surface measuring rod method, ranged from -6.290m to 7.943m. Compared with the RTK-GPS positioning method combined with the surface measuring rod method, the positioning error of the pipeline corrosion points using the bilateral orthogonal projection correction method combined with the surface measuring rod method was significantly reduced.

[0131] This invention applies the bilateral orthogonal projection correction method, which can directly measure the relevant parameters on both sides of the pipeline defect point detected by the magnetic flux leakage, and then calculate the ground location distance between the pipeline defect point and the nearest reference point on both sides by the bilateral orthogonal projection correction method calculation formula.

[0132] By comparing the positioning errors of RTK-GPS positioning method and bilateral orthogonal projection correction method in the excavation verification of corrosion defect points detected in magnetic flux leakage of two foreign long-distance crude oil pipelines, the bilateral orthogonal projection correction method not only has strong feasibility and operability, but also can reduce the difficulty of excavation verification positioning and improve the accuracy of excavation verification positioning of pipeline corrosion defect points detected in magnetic flux leakage.

[0133] Example 3

[0134] A computer device includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method for detecting internal corrosion defects using magnetic flux leakage, as described in Embodiment 1 or 2.

[0135] Example 4

[0136] A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, it implements the steps of the method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method for detecting internal corrosion defects using magnetic flux leakage, as described in Embodiment 1 or 2.

[0137] Example 5

[0138] A system for locating corrosion defects in long-distance pipelines based on the bilateral projection correction method, comprising:

[0139] The data collection module is configured to measure and collect data related to corrosion points on the pipeline in the field.

[0140] The model building module is configured to model the four important parameters of defect point pipe section elevation, burial depth, magnetic flux leakage detection mileage and reference point ground location mileage respectively, resulting in four models;

[0141] The surface positioning distance calculation module is configured to: calculate the surface positioning distance of the pipeline defect point from the nearest reference point on the left side of the pipeline defect point detected by the magnetic flux leakage using the bilateral projection correction method;

[0142] The specific location acquisition module is configured to obtain the specific location of the pipeline defect point by using the ground measuring tape method.

Claims

1. A method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method for internal detection of magnetic flux leakage, characterized in that, include: Measure and collect relevant data on corrosion points in the pipelines on site; Four key parameters—the elevation of the defective pipe section, its burial depth, the magnetic flux leakage detection mileage, and the reference point's surface location mileage—were modeled separately, resulting in four models: one constructed when the elevation increases and the burial depth decreases; another constructed when the elevation decreases and the burial depth decreases; a third constructed when the elevation increases and the burial depth increases; and a fourth constructed when the elevation decreases and the burial depth increases. In these four models, line segment X1-X2 represents the actual surface section corresponding to the short-distance defective pipe section, and line segment Y1-Y2 represents the short-distance defective point. Pipe segment Z1-Z2 represents the short-distance orthogonal projection section; point P is the intersection of the short-distance surface line and the orthogonal projection baseline; point M is the intersection of the short-distance defect point pipe segment and the orthogonal projection baseline; point Q is the intersection of the short-distance surface line and the short-distance defect point pipe segment; X0 is the actual surface location mileage corresponding to the pipeline defect point detected by magnetic flux leakage; X1 is the actual surface location mileage corresponding to the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage; X2 is the distance to the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage. The actual surface positioning mileage corresponding to the nearest reference point; Y0 is the detection mileage of the pipeline defect point detected by magnetic flux leakage, Y1 is the detection mileage of the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and Y2 is the detection mileage of the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage; Z0 is the orthogonal projection mileage of the pipeline defect point detected by magnetic flux leakage, Z1 is the orthogonal projection mileage of the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and Z2 is the orthogonal projection mileage of the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage; X0-Z0 is the elevation of the pipeline defect point detected by magnetic flux leakage, X1-Z1 is the elevation of the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and X2-Z2 is the elevation of the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage; X0-Y0 is the burial depth of the pipeline defect point detected by magnetic flux leakage, X1-Y1 is the burial depth of the nearest reference point to the left of the pipeline defect point detected by magnetic flux leakage, and X2-Y2 is the burial depth of the nearest reference point to the right of the pipeline defect point detected by magnetic flux leakage. For cases where the burial depth decreases with increasing elevation and vice versa, the formula for expressing the elevation at the pipeline defect point is as follows: ； Among them, X1-Z1 and X2-Z2 are obtained by measuring the elevation of the nearest reference point on both sides of the pipeline defect detection point in magnetic flux leakage, X1-Y1 and X2-Y2 are obtained by measuring the burial depth of the nearest reference point on both sides of the pipeline defect detection point in magnetic flux leakage, and Y0-Y1 and Y2-Y1 are obtained directly from the data in the magnetic flux leakage detection report. Using the bilateral projection correction method, the ground location distance between the pipeline defect point and the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage is calculated; For cases where the elevation increases while the burial depth decreases, and vice versa, the formula for the surface positioning distance X0-X1 from the pipe defect point to the nearest reference point on the left side of the pipe defect point detected by magnetic flux leakage is: ； The formula for the distance X2-X0 between the pipeline defect point and the nearest reference point on the right side of the pipeline defect point detected by magnetic flux leakage is: ； Among them, X1-Z1 and X2-Z2 are obtained by measuring the elevation of the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage, X0-Z0 is obtained by calculating the elevation of the pipeline corrosion point in front, and X1-X2 is obtained by directly measuring the distance to the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage. For cases where the elevation decreases and the burial depth decreases, and vice versa, the formula for the surface positioning distance X0-X2 from the pipe defect point to the nearest reference point on the right side of the pipe defect point detected by magnetic flux leakage is: ； The formula for the distance X1-X0 between the pipeline defect point and the nearest reference point on the left side of the pipeline defect point detected by magnetic flux leakage is: ； Among them, X1-Z1 and X2-Z2 are obtained by measuring the elevation of the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage, X0-Z0 is obtained by calculating the elevation of the pipeline corrosion point in front, and X1-X2 is obtained by directly measuring the distance to the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage. The exact location of the pipe defect can be obtained by using a ground measuring tape method. For cases where the burial depth increases with increasing elevation and vice versa, the formula for expressing the elevation at the pipeline defect point is as follows: ； Among them, X1-Z1 and X2-Z2 are obtained by measuring the elevation of the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage, X1-Y1 and X2-Y2 are obtained by measuring the burial depth of the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage, and Y0-Y1 and Y2-Y1 are obtained directly from the magnetic flux leakage detection report data.

2. The method for excavation and location of corrosion defect points in long-distance pipelines based on the bilateral projection correction method for internal detection of magnetic flux leakage, as described in claim 1, is characterized in that... The relevant data on pipeline corrosion points include the clock position, defect type, wall thickness loss ratio, magnetic flux leakage appearance, magnetic flux leakage detection mileage, surface positioning mileage, corrosion point burial depth, magnetic flux leakage detection mileage of the nearest reference point on both sides, and elevation of the nearest reference point on both sides.

3. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method, as described in claim 1 or 2.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for excavating and locating corrosion defect points in long-distance pipelines based on the bilateral projection correction method as described in claim 1 or 2.

5. A system for excavating and locating corrosion defect points in long-distance pipelines based on bilateral projection correction, used to implement the method for excavating and locating corrosion defect points in long-distance pipelines based on bilateral projection correction as described in claim 1 or 2, characterized in that, include: The data collection module is configured to measure and collect data related to corrosion points on the pipeline in the field. The model building module is configured to model the four important parameters of defect point pipe section elevation, burial depth, magnetic flux leakage detection mileage and reference point ground location mileage respectively, resulting in four models; The surface positioning distance calculation module is configured to: calculate the surface positioning distance of the pipeline defect point from the nearest reference point on both sides of the pipeline defect point detected by magnetic flux leakage using the bilateral projection correction method; The specific location acquisition module is configured to obtain the specific location of the pipeline defect point by using the ground measuring tape method.

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