A trenchless geophysical method for detecting weld locations in a direct buried heating pipeline

Abstract

The application provides a trenchless geophysical prospecting method for a welding joint position of a heat supply direct-buried pipeline, comprising the following steps: step 1: using a weak magnetic detection device to measure the magnetic field intensity along the route of the heat supply direct-buried pipeline, and each probe measures a set of magnetic field intensity data; step 2: performing percentage accumulation calculation on all the magnetic field intensity data measured by the probes, and calculating a percentage accumulation graph, wherein the abscissa of the percentage accumulation graph is the measurement distance, the ordinate is the percentage, and the recessed position in the percentage accumulation graph is the welding joint position. The application utilizes the characteristics that the magnetic memory area of the welding joint position is prominent due to stress concentration and welding process, and the metal content of the welding joint position is different from the homogenized pipeline in the pipeline, and the pipeline weak magnetic data is regularly abnormal due to other factors, and utilizes the weak magnetic detection technology to accurately locate the welding joint position in the premise of not digging.

Description

Technical Field

[0001] This invention belongs to the field of trenchless geophysical exploration technology for direct-buried heating pipelines, and specifically relates to a trenchless geophysical exploration method for the location of weld joints in direct-buried heating pipelines. Background Technology

[0002] In northern my country, heating in winter is provided by centralized heating. At the same time, urban construction is also progressing rapidly. Due to factors such as construction workers' lack of knowledge about the laying of heating pipelines, changes in the foundation of the heating pipelines, aging of the heating pipelines, unstable foundations during pipeline laying, quality problems of the heating pipelines themselves, weld failures at connection points, or heavy pressure on the ground where the heating pipelines are located, heating pipeline leaks and failures occur from time to time.

[0003] The primary pipeline network of urban heating systems generally uses directly buried heating pipes. The pipeline consists of iron pipes and an outer waterproof and thermal insulation layer, with each section being 12 meters long. During construction, the iron pipes are welded sequentially; the weld joint is called the weld joint. A waterproof interface device is installed outside the weld joint, covering the weld joint, the iron pipes on both sides of the weld joint, and the waterproof and thermal insulation layer.

[0004] Statistics show that over 95% of heating pipeline leaks occur at the weld joints. There are two main reasons for this: First, the pipelines are buried underground, and due to thermal expansion and contraction, stress accumulates at the weld joints, making them prone to leaks. Second, compared to the waterproof and insulation layers of each pipe section, the connection between the joint device and the waterproof and insulation layer is more susceptible to external environmental influences, leading to leaks, water seepage, and corrosion of the weld joint.

[0005] When a heating pipeline leaks and requires repair, the usual practice is to first locate the weld joints on both sides of the water seepage point on the road surface, and then excavate for repairs. This method is far less expensive than excavating the entire length of the buried heating pipeline. However, early heating pipeline construction data was incomplete or missing, making it difficult to determine the exact location of the weld joints. Summary of the Invention

[0006] This invention addresses the technical problems existing in the prior art by providing a trenchless geophysical exploration method for locating weld joints in directly buried heating pipelines. It utilizes the characteristic that the amount of ferromagnetic material at the weld joint differs from that on both sides of the iron pipe, and employs weak magnetic detection technology to accurately locate the weld joint position through geophysical exploration without excavation.

[0007] The technical solution adopted in this invention is: a trenchless geophysical exploration method for the location of weld joints in directly buried heating pipelines, comprising the following steps:

[0008] Step 1: Use a weak magnetic field detection device to measure the magnetic field strength along the route of the direct-buried heating pipeline. Each probe will measure a set of magnetic field strength data. The weak magnetic field detection device has multiple sets of probes, three in each set, which will detect the magnetic field strength along the X-axis, Y-axis and Z-axis respectively. The Z-axis is perpendicular to the ground, the X-axis is along the direction of travel of the pipeline, and the Y-axis is perpendicular to the direction of the pipeline.

[0009] Step 2: Perform percentage stacking calculation on all magnetic field strength data measured by the probe to obtain a percentage stacking map. The horizontal axis of the percentage stacking map is the measurement distance, and the vertical axis is the percentage stacking unit. The recessed positions in the percentage stacking map are the weld joint positions.

[0010] Preferably, in step 2, the depression location is defined as multiple curves simultaneously exhibiting a concave portion at the same abscissa, and the ordinate value corresponding to the lowest point of the concave portion is 0. Generally, the number of such multiple curves is the same as the number of probe groups.

[0011] Furthermore, in step 1, the measured distance along the route of the direct-buried heating pipeline is no less than 24 meters;

[0012] Step 3: Based on the spacing of the weld joint positions obtained in Step 2, the actual weld joint positions are determined by the host computer software.

[0013] Preferably, the measured distance along the route of the direct-buried heating pipeline is no more than 50 meters.

[0014] Preferably, the weak magnetic field detection device has four sets of probes.

[0015] Working Principle: Directly buried heating pipelines typically use iron pipes, which are ferromagnetic materials. At the weld joint, stress concentration and the magnetic memory region characteristic created by the welding process, along with variations in metal content compared to the homogeneous middle section of the pipeline, cause abnormal patterns in the pipeline's weak magnetic field data. Generally, the magnetic field strength at the weld joint is slightly lower than that in the middle of the pipe section. Since the magnetic field of a metal pipeline is a three-dimensional field surrounding the pipeline, a single weak magnetic field probe cannot reflect the overall magnetic field changes. The acquisition probe consists of three weak magnetic fluxgate sensors in the X, Y, and Z directions. The acquisition unit consists of four probes arranged in a plane, continuously collecting the pipeline's magnetic field along the pipeline route directly above the ground. The 12 sets of collected pipeline weak magnetic data are calculated as percentages and plotted into a curve. Areas with obvious dips in the graph correspond to the weld joint locations.

[0016] To reduce misjudgment of weld locations, the measurement distance of the direct-buried heating pipeline route should be appropriately increased to include multiple welds within that distance. For example, a measurement distance of 50 meters should contain 4 or 5 welds. Interference can be eliminated by determining the spacing of weld locations based on the percentage stacking chart. The spacing of weld locations is generally the distance of one pipe section, approximately 12 meters.

[0017] Compared with the prior art, the beneficial effects of this invention are:

[0018] 1. This invention employs a trenchless weak magnetic geophysical exploration method. It uses weak magnetic detection equipment to measure the magnetic field strength along the route of the direct-buried heating pipeline on the ground, and performs percentage accumulation calculation on the detection results of multiple probes to find the accurate location of the weld joint. The influence of misjudgment is eliminated by the spacing of the weld joint positions, and the positioning accuracy reaches 100%.

[0019] 2. This invention employs a trenchless geophysical exploration method to accurately detect weld locations, eliminating the need for road excavation, saving time and labor, and significantly reducing the cost of weld location locating. This invention contributes to the improvement of heating pipeline data and facilitates the quick and easy location of heating pipeline leaks. Attached Figure Description

[0020] Figure 1 This is a flowchart of an embodiment of the present invention;

[0021] Figure 2 This is a percentage stacked chart of an embodiment of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Embodiments of the present invention provide a trenchless geophysical exploration method for the location of weld joints in directly buried heating pipelines, such as... Figure 1 As shown, it includes the following steps:

[0024] Step 1: Use a weak magnetic field detection device to measure the magnetic field strength along the route of the buried heating pipeline at a distance of 32 meters. The weak magnetic field detection device has four sets of probes, three in each set, to detect the magnetic field strength along the X, Y, and Z axes respectively. The Z-axis is perpendicular to the ground, the X-axis is along the pipeline's direction, and the Y-axis is perpendicular to the pipeline. Each probe obtains one set of magnetic field strength data, resulting in 12 sets of data. The data is uploaded to a host computer connected to the weak magnetic field detection device.

[0025] Step 2: The host computer software performs percentage stacking calculations on the 12 sets of magnetic field strength data measured by the probe, and obtains a percentage stacking chart, as shown below. Figure 2As shown, the horizontal axis of the percentage stacking chart represents the measured distance, and the vertical axis represents the percentage stacking unit. Three distinct depressions can be observed on the percentage stacking chart, approximately at 3 meters, 15 meters, and 27 meters. At each depression, the vertical axis values ​​of four curves are simultaneously 0. The horizontal axis corresponding to each depression with a vertical axis value of 0 represents a weld joint location. Three weld joint locations have been preliminarily identified, as follows: Figure 2 The location indicated by the arrow shown in the image.

[0026] Step 3: Based on the spacing of the three weld locations obtained in Step 2, the true weld locations are selected. The typical spacing between weld locations should be the length of one pipe section, i.e., 12 meters. Therefore, 12 ± 1 meters is used as the selection criterion. The spacing of the three weld locations is 12 meters and 12 meters respectively. After analysis by the host computer software, all three weld locations are confirmed to be true weld locations.

[0027] The present invention has been described in detail above through embodiments, but the content described is only an exemplary embodiment of the present invention and should not be considered as limiting the scope of the present invention. The scope of protection of the present invention is defined by the claims. Any technical solutions designed by those skilled in the art using the technical solutions described in the present invention, or designed by those skilled in the art under the inspiration of the technical solutions of the present invention, within the substance and protection scope of the present invention, to achieve the above-mentioned technical effects, or any equivalent changes and improvements made to the scope of the application, should still fall within the patent protection scope of the present invention.

Claims

1. A trenchless geophysical exploration method for the location of weld joints in directly buried heating pipelines, characterized in that: Includes the following steps: Step 1: Use a weak magnetic field detection device to measure the magnetic field strength along the route of the direct-buried heating pipeline, and obtain a set of magnetic field strength data for each probe; The weak magnetic field detection equipment has multiple sets of probes, three in each set, which detect the magnetic field strength along the X-axis, Y-axis and Z-axis respectively. The Z-axis is perpendicular to the ground, the X-axis is along the direction of travel of the pipeline, and the Y-axis is perpendicular to the direction of the pipeline. Step 2: Perform percentage stacking calculation on all magnetic field strength data measured by the probe to obtain a percentage stacking map. The horizontal axis of the percentage stacking map is the measurement distance, and the vertical axis is the percentage stacking unit. The recessed positions in the percentage stacking map are the weld joint positions. In step 2, the depression location is where multiple curves simultaneously show a concave portion at the same horizontal coordinate, and the vertical coordinate value corresponding to the lowest point of the concave portion is 0. In step 1, the measurement distance along the route of the direct-buried heating pipeline shall not be less than 24 meters; Step 3: Based on the spacing of the weld joint positions obtained in Step 2, determine the actual weld joint positions through analysis.

2. The trenchless geophysical exploration method for the weld location of directly buried heating pipelines as described in claim 1, characterized in that: The measured distance along the route of the direct-buried heating pipeline shall not exceed 50 meters.

3. The trenchless geophysical exploration method for the weld location of directly buried heating pipelines as described in claim 1, characterized in that: The weak magnetic field detection device has four sets of probes.

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