A probe and electromagnetic measuring method for electromagnetic measurement of the depth of soil covering of underwater pipelines

Abstract

A kind of probe for underwater pipeline depth electromagnetic method measurement and electromagnetic measurement method.The present application applies a three-component orthogonal coil group installed in a non-metallic material shell as a measurement sensor of electromagnetic signal, and a three-dimensional electronic compass, together with an embedded circuit board to form a measurement probe, for electromagnetic measurement of the position and depth of covering of underwater steel pipelines and cables.The probe is lowered into the water through a telescopic connecting rod, and is connected to a main device on the equipment of a mother ship by a umbilical cable, which is responsible for parameter setting and display and storage of measurement results.During the detection process, the probe is towed vertically along the pipeline by the mother ship in the form of a towfish, and the azimuth angle data measured by the compass are uploaded to the main device, which calculates the position of the target pipeline and the thickness of the covering layer.The present application can be widely applied to the measurement of the position and depth of covering of underwater steel pipelines and cables in rivers and oceans.

Description

Technical Field

[0001] This invention relates to an electromagnetic detection method for the thickness of the soil cover layer on underwater pipelines and cables. It belongs to the field of underwater pipeline detection technology and integrates sensor fabrication, electromagnetic measurement methods, mathematical calculation methods, and embedded systems. Background Technology

[0002] Electromagnetic positioning of conventionally buried metal pipelines is a mature technology. Its principle is as follows: a signal transmitter applies a detection signal to the buried pipeline, or the pipeline itself carries a power frequency signal. A signal receiver uses a peak / valley detection mode to locate the pipeline's route and direction on the ground and measure its burial depth. Two vertically arranged horizontal coils of the receiver measure the intensity difference of the induced signal, and the distance from the pipeline center to the center of the bottom coil of the receiver can be calculated using a simple formula. Conventional electromagnetic positioning and burial depth measurement methods are widely used in the inspection of buried pipelines on land, and have advantages such as simple measurement methods and low construction costs. However, this measurement method requires that the two vertical coils be perpendicular to the pipeline and directly above it during the measurement process; the accuracy of the measurement position is crucial for accurately measuring the pipeline's location and burial depth.

[0003] Shallow-profile sonar is a primary method for surveying submarine pipelines. However, it faces challenges such as difficulty in accurately identifying target pipelines when multiple pipelines or adjacent structures are present, difficulty in signal identification at greater depths, and inability to detect submarine cables due to their small size. Furthermore, electromagnetic measurement techniques for underwater pipeline detection suffer from difficulties due to the complex and variable underwater environment, making it challenging to ensure that two vertical coils are perpendicular to and directly above the pipeline, resulting in insufficient measurement accuracy or low detection efficiency. Therefore, reducing the technical requirements for underwater measurement equipment's detection attitude, minimizing application complexity, and improving detection efficiency are crucial for expanding the application of electromagnetic methods for underwater pipeline surveying. Summary of the Invention

[0004] The purpose of this invention is to address the problems of inaccurate pipeline location detection and excessively high requirements for equipment attitude during the current electromagnetic method for measuring the soil cover depth of underwater pipelines. This invention provides an electromagnetic measurement method for the soil cover depth of underwater pipelines, employing a combination of a three-component orthogonal coil group and an electronic compass. This avoids the influence of the detection equipment's orientation in the water on the measurement, thereby accurately determining the location and soil cover depth of the underwater pipeline.

[0005] Technical solution of the present invention

[0006] A probe for electromagnetic measurement of underwater pipeline overburden depth includes a probe housing, a built-in circuit board, a three-dimensional electronic compass, and a three-component orthogonal coil group. Both the three-dimensional electronic compass and the three-component orthogonal coil group are connected to the circuitry on the built-in circuit board. The long axis of the probe body, the Y-axis of the orthogonal three-component coils, and the forward direction of the three-dimensional electronic compass are arranged on a straight line, with the forward direction being the positive direction of the Y-axis. The X-axis of the compass overlaps with the X-axis of the coils; the Z-axis of the compass overlaps with the Z-axis of the coils, with the upward direction being the positive direction. The built-in circuit board includes a signal conditioning circuit connected to the three-component orthogonal coil group. The signal conditioning circuit and the three-dimensional electronic compass are respectively connected to a microprocessor, which is connected to a host device via a serial port and an umbilical cable. The built-in signal conditioning circuit on the circuit board amplifies and filters the induced electrical signal from the three-component orthogonal coil group, performs AD conversion, and then uploads it along with the three-dimensional electronic compass data to the host device via the umbilical cable.

[0007] This invention also provides an electromagnetic measurement method for the soil cover depth of underwater pipelines, comprising:

[0008] First, apply an AC detection current to the target pipeline, place the probe described above on the telescopic linkage of the mother ship, and have the mother ship tow it from one side of the pipeline to the other side in a direction roughly perpendicular to the pipeline. During this process, the three-component orthogonal coil group in the probe receives the electromagnetic signal of the pipeline.

[0009] The electromagnetic signals collected by the second and third component orthogonal coil groups are processed by the signal conditioning circuit in the built-in circuit board, and then converted by A / D. The composite vector of the alternating electromagnetic field on the pipeline is calculated using formula (1):

[0010] (1)

[0011] In the formula, E x This represents the induced electromotive force in the X direction of the three-component orthogonal coil group. E y This represents the induced electromotive force in the Y direction of the three-component orthogonal coil group. E z This is the induced electromotive force in the Z direction of the three-component orthogonal coil group;

[0012] Third, the heading angle Azimuth is measured by the three-dimensional electronic compass inside the probe. When the probe is directly above the pipeline, that is, when the three-component orthogonal coil group measurement values ​​are used to calculate the composite vector using formula (1). E When the value is at its maximum, the angle α between the target pipeline and the magnetic north direction is calculated using formula (2):

[0013] (2)

[0014] in:A 探头 The angle between the projection of the probe axis onto the pipeline plane and the pipeline axis; Azimuth is the angle between the major axis of the probe and the magnetic north direction (i.e., the compass heading angle).

[0015] Because the vector is directly above the pipeline E The direction is perpendicular to the pipeline and horizontal, by E and E y It can be calculated A 探头

[0016] (3)

[0017] By combining the satellite positioning module on the mother ship's main equipment, the displacement of the probe during the towing process is recorded in real time. The maximum value of the vector formed by the combination of the three components of the probe's orthogonal coils is calculated using formula (4). E max up to 0.707 E max The distance the position moves X is the projected length relative to the vertical plane of the target pipeline. A :

[0018] (4)

[0019] in: X To the maximum value of the vector E max up to 0.707 E max The displacement value of the probe at that time.

[0020] The distance between the probe and the bottom of the water was measured by the depth sensor on the telescopic linkage used by the mother ship to tug the fish when the probe was directly above the pipeline. h 水 The burial depth of the target pipeline is calculated using formula (5). d and output display,

[0021] (5)

[0022] in: X A Maximum value of probe composite vector E max up to 0.707 E max

[0023] The projected length of the center distance of the location onto the vertical plane of the target pipeline. h 水 This is the distance between the probe and the bottom of the water when the probe is directly above the pipeline.

[0024] Advantages and positive effects of the present invention:

[0025] The electromagnetic measurement method for underwater pipeline cover depth provided by this invention effectively eliminates the influence of probe attitude on pipeline positioning and cover depth measurement when the probe is fixed to the telescopic linkage of the mother ship and the mother ship tows a fish for detection. This results in more accurate pipeline positioning and cover thickness measurement results. Furthermore, it avoids the difficulties in detection construction caused by maintaining probe attitude during the detection process, significantly improving the work efficiency of the detection process.

[0026] The positive effects of the electromagnetic measurement method of this invention are as follows: First, by measuring the location and overburden depth of underwater pipelines through a three-component orthogonal coil group of the probe, when there are accompanying pipelines or other ferromagnetic objects near the target pipeline, a reasonable signal application method can be used to make the signal of the target pipeline the strongest, while minimizing the detection signal on other pipelines or structures, thus distinguishing and suppressing the interference of other underground structures on the measurement process. In contrast, the shallow marine profiling method cannot selectively perform measurements. Therefore, when there are dense underground pipelines or other structures, the measurement results of the shallow marine profiling method have significant deviations, and it may even be impossible to effectively distinguish them to obtain correct measurement results.

[0027] Secondly, the method for calculating the synthesized vector of the electromagnetic field induced electromotive force of underwater pipelines using a three-component orthogonal coil array in this invention can solve the problem of accurately locating the probe directly above the underwater pipeline. Furthermore, the maximum value of the synthesized vector... E max up to 0.707 E max By combining the center distance of the probes at two locations with the technology of calculating the projected length of the probe on the vertical plane of the pipeline using a horizontal electronic compass, the soil cover depth on the target pipeline can be accurately measured, thus improving the accuracy of the measurement results.

[0028] Third, recording all detection data and calculation results during the detection process can eliminate the error effects caused by various interferences. This invention integrates electromagnetic measurement equipment structure and methods, signal conditioning methods, measurement result calculation methods, embedded systems, and other technologies. This makes the detection method and the resulting instrument system possess high detection accuracy and a simple and effective measurement method.

[0029] The advantages of this invention are: 1. It can directly detect the inherent power frequency signal on underwater pipelines, achieving a simple and rapid detection effect; it can also be used as an active electromagnetic measurement method by applying a specific frequency signal to the pipeline to be detected, effectively improving the target resolution capability in complex underground environments. 2. The method of obtaining the composite vector of the induced electromotive force of the pipeline electromagnetic field using three-component orthogonal coils can quickly locate the precise position of the pipeline. 3. The method of combining the composite vector of the three-component orthogonal coils with the horizontal electronic compass calculation method can obtain the maximum value of the composite vector of the three-component coils of the probe.E max up to 0.707 E max The distance between the two locations relative to the true center of the electromagnetic field signal of the pipeline. The detection device based on the measuring probe developed in this invention has the characteristics of simple structure, safety and reliability, and ease of use. Attached Figure Description

[0030] Figure 1 Schematic diagram of electronic compass heading angle and the angle between the probe and the target pipeline.

[0031] Figure 2 Schematic diagram of electromagnetic towed fish detection.

[0032] Figure 3 Probe structure diagram.

[0033] Figure 4 Functional framework diagram of the probe.

[0034] In the picture:

[0035] 1-Target pipeline, 2-Probe body, 3-Three-component orthogonal coil group, 4-Working mother ship, 5-Telescopic link, 6-Three-dimensional electronic compass, 7-Built-in circuit board, 8-Carbon fiber probe shell. Detailed Implementation

[0036] Example 1: Shallow Seabed Pipeline Positioning and Measurement System

[0037] The shallow seabed pipeline positioning and measurement system consists of a probe and a measurement host, which are connected by an umbilical cable.

[0038] The probe provided by this invention for electromagnetic measurement of underwater pipeline overburden depth is as follows: Figure 3 As shown, the device includes a carbon fiber probe housing 8, a three-component orthogonal coil assembly 3, an internal circuit board 7, and a three-dimensional electronic compass 6. Both the three-component orthogonal coil assembly and the three-dimensional electronic compass are connected to the internal circuit board (see [reference]). Figure 4 The built-in circuit board uses an STM32F103CB microprocessor as the main control unit, including a signal conditioning circuit and an AD conversion module connected to the three-component orthogonal coil group. The three-dimensional electronic compass is also connected to the microprocessor; the microprocessor is connected to the host device via a serial port and an umbilical cable. The signal processing circuit on the circuit board amplifies and filters the measurement signal from the coil, performs AD conversion, and then sends it along with the measurement data from the three-dimensional electronic compass to the STM32F103CB microprocessor, which then transmits it to the host device on the mother ship via the umbilical cable. The long axis of the probe body, the Y-axis of the orthogonal three-component coil, and the forward direction of the three-dimensional electronic compass are arranged on a straight line, with the forward direction of measurement being the positive direction of the Y-axis; the X-axis of the compass overlaps with the X-axis of the coil; the Z-axis of the compass overlaps with the Z-axis of the coil and is upward as the positive direction; (see...) Figure 1 , Figure 3 The main measuring unit on the mother ship uses an STM32F103RC microprocessor as its control core, forming a measuring device for high-precision positioning and overburden thickness of shallow seabed pipelines.

[0039] The system's function is as follows: Under mining conditions where the target pipeline crosses the shallow seabed, the inspection personnel apply an AC signal to the target pipeline, and the mother ship moves the probe using a towed measuring method. The detection data is transmitted in real time to the measuring host on the mother ship (see...). Figure 2 As the probe moves from one side of the pipeline to the other, the measurement host performs calculations based on the received data and displays the results on the monitor. After the detection is completed, the measurement host outputs the location of the target pipeline and the depth of the soil cover, and stores all the detection data.

[0040] I. Hardware Implementation:

[0041] 1. Measuring probe (see...) Figure 3 The probe is 300mm long and 60mm in diameter; the probe housing is a high-strength carbon fiber probe shell; 3 is the three-component orthogonal electromagnetic coil group inside the probe; 7 is the built-in circuit board; 6 is the three-dimensional electronic compass; the three-component orthogonal coil group is connected to the circuit on the built-in circuit board; the built-in circuit board is based on an STM32F103CB microprocessor, and the chip resources are the same as those of the main measuring host. After all the induced electromotive forces of the coils are amplified and filtered by the circuit, the microprocessor is responsible for uploading the measurement data and the three-dimensional electronic compass data to the main measuring host of the mother ship via the umbilical cable (see...). Figure 2 ).

[0042] Secondly, the measurement host is constructed using an STM32F103RC microprocessor to complete functions such as real-time calculation of detection results, data storage of results, power management, setting of detection and display parameters, and operation.

[0043] The microprocessor on the built-in circuit board of the measurement host and probe has the following resources:

[0044] A. The clock frequency is 72MHz.

[0045] B. It has 3 SPI serial ports and 5 UART serial ports.

[0046] C. Flash-256K, RAM-48K.

[0047] The main measuring unit is connected to an external 7.0-inch high-definition color LCD screen with a resolution of 800x480 via a UART port.

[0048] II. Basis and Principle for Calculating the Soil Cover Depth of Underwater Pipelines in this Invention

[0049] The major axis of the probe body, the Y-axis of the orthogonal three-component coil, and the forward direction of the three-dimensional electronic compass are arranged on a straight line. Definition:

[0050] The compass roll axis is the Y-axis and the forward direction is positive; the compass pitch axis is the X-axis and the rightward direction is positive; the compass heading axis is the Z-axis and the upward direction is positive.

[0051] Ex, Ey, Ez The upward induced electromotive force along the X, Y, and Z axes in a three-component orthogonal coil group, unit: volt;

[0052] E The vector value of the induced electromotive force of the three-component orthogonal coil, in volts;

[0053] Emax The maximum value of the synthesized vector induced electromotive force in a single detection, in volts;

[0054] A The angle between the projection of the probe's major axis onto the target pipeline plane and the target pipeline's axial direction;

[0055] Azimuth The heading angle measured by the electronic compass;

[0056] X For the composite vector from the maximum value E max up to 0.707 E max The probe displacement value at the location, in meters;

[0057] X A The projected length of the X distance in the plane perpendicular to the target pipeline, in meters;

[0058] h 水 This is the distance between the probe and the bottom of the water when the probe is directly above the pipeline, in meters.

[0059] d The thickness of the cover layer is the distance between the center of the pipeline and the bottom of the water. Subtracting the pipeline radius gives the thickness of the cover layer, in meters.

[0060] here:

[0061] Because the target pipeline carries a sinusoidal signal current, a columnar electromagnetic field (such as...) is formed on the pipeline with the pipeline as the center. Figure 2 As shown), during the process of the mother ship towing the probe closer to the target pipeline, the induced electromotive force of each of the three orthogonal coil groups is combined into a vector. E As given in formula (1).

[0062] (1)

[0063] A 探头 The angle between the projection of the probe axis onto the pipe plane and the pipe axis; Azimuth is the angle between the probe's major axis and magnetic north (the compass heading angle).

[0064] Because the vector is directly above the pipe E The direction is perpendicular to the pipe and horizontal, by E and E y It can be calculated A 探头

[0065] (3)

[0066] When the resultant vector of the three-component orthogonal coil group reaches its maximum, that is, directly above the target pipeline (e.g.) Figure 2 According to the Biot-Savart law, the induced electromotive force of a coil is inversely proportional to the distance between the coil and the center of the pipe. Therefore:

[0067]

[0068] here: I The signal current value in the target pipe. K The coefficients are related to factors such as the dielectric constant and magnetic permeability of the surrounding environment of the pipeline, and are considered to be within a detection profile. KI It remains unchanged. When the probe shifts... X When the distance reaches one side of the pipeline, the composite vector measured by the three-component orthogonal coil is:

[0069]

[0070] like E for E max of Then:

[0071]

[0072] Then we have:

[0073]

[0074] Right now: X A = d + h 水 The burial depth of the target pipeline is calculated as follows:

[0075] (5)

[0076] in:

[0077] X A The composite vector measured by the probe is the maximum value. E max Location to E max / 2≈0.707 E max The distance the value moves is the projected length in the plane perpendicular to the target pipeline; h 水 This is the distance between the probe and the bottom of the water when the probe is directly above the pipeline. The burial depth of the target pipeline is calculated using formula (5) and displayed.

[0078] III. Implementation of the detection method:

[0079] 1) Implementation of methods for locating and measuring the depth of cover of shallow-sea subsea pipelines.

[0080] like Figure 1 and Figure 2 As shown, firstly, an AC signal is applied to the target pipeline 1, with signal frequencies of 8kHz and 32.8kHz, or 50Hz from the target cable itself. Preliminary information on the horizontal position of the target pipeline is initially established along the route of the mother ship. The probe gradually approaches the pipeline from one side using a towing method from the mother ship, transmitting the detection data to the main unit of the equipment on the mother ship in real time. After crossing a certain distance across the pipeline, a data acquisition is completed. The probe uploads the induced electromotive force of the three-component orthogonal coil and the heading angle data from the electronic compass. The main unit receives the detection data from the probe and the position data from the satellite antenna via the umbilical cable. Formulas (1), (2), (3), (4), and (5) are used to calculate the composite vector of the induced electromotive force of the probe's three-component orthogonal coil group and the maximum value of the composite vector of the probe's three-component coils during the acquisition process. E max up to 0.707 E max The displacement distance relative to the pipeline in the vertical direction is measured to determine the pipeline's position, the angle between the target pipeline and magnetic north, and the thickness of the overburden layer above the pipeline. Combined with the GNSS satellite positioning module on the mothership, the pipeline's position coordinates are calculated.

[0081] 2) The technical specifications of the measuring host are as follows:

[0082] Data recording method SD card, interface: USB Data Channel Three electromagnetic induction intensity measurement channels, one electronic compass input channel. Detection function Measurement of underwater pipeline location, pipeline orientation angle, and overburden thickness. Data measurement cycle 50ms Data record capacity Stores 65,535 sets of azimuth, burial location and depth data Data shows Color LCD screen, 800x480 Measurement accuracy ±(5%d+0.2m) is the measured burial depth value.

[0083] 3) Verification data of actual application effect

[0084] Serial Number Pipeline burial depth (meters) <![CDATA[ E max (V)]]> Distance X (meters) α (degree) <![CDATA[h 水 (meters) Measure and calculate burial depth (meters) Deviation rate 1 0.6 137.62 1.81 4.3 1.21 0.59 -1.67% 2 1.00 97.62 2.21 4.3 1.2 1.00 0% 3 2.13 73.07 3.71 8.8 1.52 2.15 0.94% 4 3.24 48.99 5.17 8.5 1.88 3.23 -0.31% 5 4.43 36.29 7.52 27.4 2.21 4.47 0.90% 6 5.78 28.58 10.71 31.5 3.3 5.83 0.87%

Claims

1. A method of electromagnetic measurement of the burial depth of an underwater pipeline, characterized in that, The utility model relates to a kind of underwater pipeline depth electromagnetic method measuring probe, including: 1, AC detection current is applied to target pipeline, the probe for underwater pipeline depth electromagnetic method measurement is placed on telescopic connecting rod on mother ship and is towed by mother ship in the way of drag fish from one side of pipeline to the other side along the direction perpendicular to pipeline, three-component orthogonal coil group in probe receives electromagnetic signal of pipeline during the process; 2, electromagnetic signal collected by three-component orthogonal coil group is handled after signal conditioning circuit in built-in circuit board, then A / D conversion is carried out, and the synthetic vector of alternating electromagnetic field on pipeline is calculated using formula (1): (1) wherein E x is the induced electromotive force in the X direction of the three-component orthogonal coil set, E y is the induced electromotive force in the Y direction of the three-component orthogonal coil set, E z is the induced electromotive force in the Z direction of the three-component orthogonal coil set; The third, the three-dimensional electronic compass in the probe measures the azimuth angle. When the probe is located directly above the pipeline, the synthetic vector of the three-component orthogonal coil group is measured and calculated by formula (1) E When the maximum value is obtained, the angle α between the target pipeline and the magnetic north direction is calculated by formula (2): (2) wherein: A 探头 is the angle between the projection of the probe axis on the pipeline plane and the pipeline axis; Azimuth is the angle between the long axis of the probe and the magnetic north direction, i.e. the heading angle of the compass; Since the direction of the pipeline positive direction vector E is perpendicular to the pipeline and horizontal, by E and E y one can calculate A 探头 (3) Combining with the satellite positioning module on the main engine of the mother ship, the displacement of the probe during the towing process of the mother ship is recorded in real time; the maximum value of the three-component orthogonal coil combination of the probe is calculated by formula (4) E max to 0.707 E max The projection length X of the moving distance of the position relative to the vertical plane of the target pipeline A : (4) wherein: X is the maximum value of the vector E max to 0.707 E max the displacement value of the probe; The water depth sensor on the telescopic link used in combination with the mother ship to measure the distance between the probe and the water bottom when the probe is located directly above the pipeline h 水 The target pipeline burial depth value is calculated by applying formula (5) d and outputted and displayed, (5)。 2. The electromagnetic surveying method of claim 1, wherein, The utility model relates to a kind of underwater pipeline depth electromagnetic method measuring probe, including probe shell, built-in circuit board, three-dimensional electronic compass and a three-component orthogonal coil group, three-dimensional electronic compass and three-component orthogonal coil group are connected with the circuit in built-in circuit board;The long axis of probe body, orthogonal three-component coil Y axis, three-dimensional electronic compass forward direction are arranged on a straight line, and the measurement forward direction is the positive direction of Y axis;The X of compass and coil X axis line overlap;The Z of compass and coil Z axis line overlap and upward is positive direction;Built-in signal conditioning circuit in circuit board amplifies and filters the induced electric signal of three-component orthogonal coil group, after AD conversion, three-dimensional electronic compass data are uploaded to equipment host computer.

3. The electromagnetic surveying method of claim 2, wherein, The utility model relates to a kind of underwater pipeline depth electromagnetic method measuring probe, including signal conditioning circuit connected with three-component orthogonal coil group in built-in circuit board, signal conditioning circuit and three-dimensional electronic compass are connected with microprocessor respectively, and microprocessor is connected with equipment host computer through serial port and umbilical cable.

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