Method for detecting corrosion degree of above-ground metal pipeline and buried metal pipeline

Abstract

The application provides a method for detecting corrosion degree of aboveground metal pipeline and buried metal pipeline. The method for detecting corrosion degree of aboveground pipeline comprises the following steps: a power supply electrode and a measuring electrode circuit are arranged on the inner wall or the outer wall of the pipeline respectively, the potential of the non-corrosion layer of the measuring point of the measuring electrode on the inner wall or the outer wall of the pipeline is measured; based on the potential distribution of the inner wall or the outer wall of the pipeline, the resistance of the corrosion layer of the measuring point of the measuring electrode on the inner wall or the outer wall of the pipeline is measured by using the measuring circuit; based on the resistance of the corrosion layer of the measuring point of the measuring electrode on the inner wall or the outer wall of the pipeline, the thickness of the corrosion layer of the pipeline is measured. The method for detecting corrosion degree of buried metal pipeline comprises the following steps: a power supply electrode and a measuring electrode circuit are arranged on the inner wall of the pipeline, the center of the pipeline is taken as the origin, the axial direction of the pipeline is taken as the z-axis, and the radial direction of the pipeline is taken as the r-axis to construct a pipeline transmission line stratum model, equivalent longitudinal conductance of fluid in the pipeline, the inner wall of the non-corrosion pipeline and the corrosion layer of the inner wall of the pipeline is constructed, the pipeline transmission line equation is determined, and the resistance and the thickness of the corrosion layer of the outer wall of the pipeline are calculated.

Description

Technical Field

[0001] This application relates to the field of pipeline inspection and maintenance technology, and in particular to a method for detecting the corrosion degree of above-ground and buried metal pipelines. Background Technology

[0002] Water resources are a crucial factor influencing human living standards, social stability, and economic development. Urban water supply systems, as the infrastructure for transporting and utilizing water resources, are a marker of a city's development status and capacity, and a fundamental element ensuring urban progress. However, due to various complex factors affecting underground pipelines, defects inevitably occur during operation. Many buried oil and water pipelines operate with these defects, making them highly susceptible to leaks. The most common and serious problem is corrosion, which worsens with age and can even lead to perforation and rupture, resulting in safety accidents.

[0003] Currently, the main methods for detecting corrosion in pipelines, both domestically and internationally, include ultrasonic, magnetic flux leakage, eddy current, and transient electromagnetic methods. However, a common problem with these detection technologies is their low accuracy and reliance on location-based detection, making it difficult to directly measure and estimate the resistance or thickness of the corrosion layer. Inspections and repairs are typically only carried out after a pipeline accident, leading to resource waste, economic losses, and potentially even personal injury, building collapse, and environmental pollution. Summary of the Invention

[0004] In view of this, the purpose of this application is to propose a method for detecting the corrosion degree of above-ground and buried metal pipelines to overcome the above-mentioned problems.

[0005] To achieve the above objectives, a first aspect of this application provides a method for detecting the corrosion degree of above-ground metal pipelines, comprising:

[0006] A power supply electrode and a measuring electrode circuit are respectively installed on the inner wall or outer wall of the pipe to measure the potential of the non-corrosion layer at the measuring electrode measuring point on the inner wall or outer wall of the pipe.

[0007] Based on the potential distribution of the inner or outer wall of the pipe, the resistance of the corrosion layer at the measuring electrode measuring point on the inner or outer wall of the pipe is measured using a measuring circuit.

[0008] The thickness of the corrosion layer in the pipe is measured based on the resistance of the corrosion layer measured by the measuring electrode on the inner or outer wall of the pipe.

[0009] The measuring electrode circuit includes a measuring electrode, a first measuring circuit, and a second measuring circuit. The first measuring circuit and the second measuring circuit are connected in series with the measuring electrode, and the first measuring circuit and the second measuring circuit are connected in parallel. The first measuring circuit includes a first potentiometer and a first ammeter connected in series, and the second measuring circuit includes a second potentiometer and a second ammeter connected in series.

[0010] Optionally, the formula for calculating the potential of the pipe wall is:

[0011] I1R r +I1(R V1 +R I1 )=U

[0012] I2R r +I2(R V2 +R I2 )=U

[0013] Among them, R r To measure the resistance of the corrosion layer at the electrode measurement point, I1 is the reading of the first ammeter, R. V1 R is the resistance of the first potentiometer. I1 The resistance of the first ammeter, I2, is the reading of the second ammeter; R V2 R is the resistance of the second point differential meter. I2 The resistance of the second ammeter is denoted by , and U is the potential of the non-corroded pipe wall.

[0014] Optionally, the formula for calculating the thickness of the corrosion layer on the pipeline is:

[0015]

[0016] Where δ is the thickness of the rust layer, S is the contact area between the measuring electrode and the pipe, and ρ r The resistivity of the corrosion layer on the pipeline.

[0017] A second aspect of this application provides a method for detecting the corrosion degree of buried metal pipelines, comprising:

[0018] A power supply electrode and a measuring electrode circuit are provided on the inner wall of the pipe to measure the measured potential of the non-corrosion layer at the measuring electrode measurement point on the inner wall of the pipe; wherein the measuring electrode circuit includes a measuring electrode, a first measuring circuit and a second measuring circuit, the first measuring circuit and the second measuring circuit are connected in series with the measuring electrode respectively, the first measuring circuit and the second measuring circuit are connected in parallel, the first measuring circuit includes a first potentiometer and a first ammeter connected in series, and the second measuring circuit includes a second potentiometer and a second ammeter connected in series;

[0019] A pipeline transmission line geological model is constructed with the center of the pipeline as the origin, the axial direction of the pipeline as the z-axis, and the radial direction of the pipeline as the r-axis.

[0020] Based on the pipeline transmission line geological model and the flow of fluid and current in the pipeline along the pipeline axis, the equivalent longitudinal conductivity of the fluid in the pipeline, the non-corroded inner wall of the pipeline, and the corrosion layer of the inner wall of the pipeline is constructed.

[0021] Based on the equivalent longitudinal conductivity, the pipeline transmission line equation is determined;

[0022] Calculate the pipeline transmission line equation and determine the calculated potential of the non-corrosion layer of the pipeline wall;

[0023] The partial derivatives of the potential with respect to the formation parameters of the pipeline transmission line formation model are calculated using the Jacobi potential matrix.

[0024] The inversion objective function is determined by the measured potential and the calculated potential.

[0025] Using the pipeline transmission line equation and the partial derivative of the potential with respect to the formation parameters, the resistance of the corrosion layer on the outer wall of the pipeline is calculated by inversion iterative approximation through inversion objective function;

[0026] The thickness of the corrosion layer on the outer wall of the pipe is calculated based on the resistance of the corrosion layer.

[0027] Optionally, the calculation formula for constructing the equivalent longitudinal conductivity of the fluid, the non-corroded pipe wall, and the corroded layer in the pipe based on the pipeline transmission baseline model and the flow of fluid and current in the pipe along the pipe axis is as follows:

[0028] S = S f +S C +S r ,

[0029] in,

[0030] R is the total equivalent longitudinal resistance per unit length in the axial direction;

[0031] The resistance per unit length of the fluid in the axial water supply pipe;

[0032] ρ f The resistivity of the fluid inside the pipe;

[0033] a1 is the inner radius of the pipe corrosion layer;

[0034] R c The resistance per unit length of a non-corroded water supply pipe along the axial direction;

[0035] R r=ρ r / [2πa2(a3-a2)] is the resistance per unit length of the rust layer inside the water supply pipe along the axial direction, σ r =1 / ρ r ;

[0036] a2 is the inner radius of the non-corrosion pipe, and a3 is the outer radius of the non-corrosion pipe;

[0037] σ r The conductivity of the corrosion layer on the pipeline.

[0038] Optionally, based on the equivalent longitudinal conductance, the formula for calculating the pipeline transmission line equation is:

[0039]

[0040]

[0041] Wherein, U represents the potential distribution of the non-corroded water supply pipe wall;

[0042] I represents the current in the non-corrosion-resistant water supply pipe wall;

[0043] T is the lateral resistance of the formation, and α is the formation α coefficient.

[0044] Optionally, the partial derivatives of the potential with respect to the formation parameters of the pipeline transmission line formation model are calculated using the potential Jacobi matrix, including:

[0045] The geological model of the pipeline transmission line is divided into units along the pipeline;

[0046] Based on the pipeline transmission line stratigraphic model divided by the aforementioned units, the form of the Jacobi matrix is ​​determined.

[0047] Determine the location of the measuring electrode in the formation model of the pipeline transmission line;

[0048] Based on the Jacobi matrix form and the location of the measuring electrode in the pipeline transmission line formation model, the partial derivatives of the potential of the transmission line formation model with respect to the formation parameters are determined.

[0049] Optionally, the Jacobi matrix is ​​in the form of:

[0050] ΔU=GΔm,

[0051] Where ΔU is the potential increment and Δm is the perturbation increment of the pipeline transmission line formation model parameters;

[0052]

[0053] Resistance vector of the transmission line stratigraphic model divided into cells;

[0054] The potential of the transmission line stratum model divided into units.

[0055] Optionally, the resistance of the outer corrosion layer of the pipeline can be calculated by using the pipeline transmission line equation and the partial derivative of the potential with respect to the formation parameters through an inversion objective function inversion iterative approximation.

[0056] The formula for calculating the inversion objective function is as follows:

[0057] F(m) = ||UU obs ||

[0058] Among them, U obs To measure the potential of the non-corroded pipe wall;

[0059] U represents the potential of the non-corroded pipe wall.

[0060] Optionally, the inversion iterative approximation formula is:

[0061] d k =-(G k T G k +β k I) -1 G k T f k

[0062] Where d k This represents the increment of formation parameters obtained in the k-th iteration;

[0063] G k T G k This is the product of the partial derivative matrices of the pipeline transmission line equations;

[0064] I is an n-order identity matrix, β k It is a positive real constant.

[0065] As can be seen from the above, the above-ground pipeline corrosion detection method provided by this application can directly measure and calculate the thickness of the corrosion layer on the inner and outer walls of the pipeline through the power supply electrode and measuring electrode circuit. The buried pipeline corrosion detection method establishes a pipeline transmission line stratum model and proposes methods for calculating the transverse resistance of the transmission line stratum model and the equivalent transverse resistance of the corroded pipeline and the fluid inside the pipeline. It uses the pipeline transmission line equation to calculate the potential distribution of the non-corroded pipeline wall, and inverts the resistance and thickness of the corrosion layer on the outer wall of the pipeline based on the pipeline wall potential, thereby achieving the measurement and evaluation of the remaining thickness of the corroded pipeline wall. This allows for timely and accurate understanding of the current pipeline status, enabling a scientific safety assessment of the pipeline based on its current condition and providing relevant maintenance suggestions, reducing the risk of pipeline failure and avoiding unnecessary economic losses. Attached Figure Description

[0066] To more clearly illustrate the technical solutions in this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0067] Figure 1 This is a flowchart of a method for detecting the corrosion degree of above-ground metal pipelines according to an embodiment of this application;

[0068] Figure 2 This is a schematic diagram of the detection mode for above-ground metal pipes and power supply in an embodiment of this application;

[0069] Figure 3 This is a flowchart of a method for detecting the corrosion degree of buried metal pipelines according to an embodiment of this application;

[0070] Figure 4 This is a schematic diagram of a corroded pipe according to an embodiment of this application;

[0071] Figure 5 This is a schematic diagram of the geological formation model of a metal pipeline transmission line according to an embodiment of this application. Detailed Implementation

[0072] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0073] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0074] In the process of measuring the corrosion resistance of above-ground pipelines, when the power supply electrode makes good contact with the pipeline wall, the potential distribution of the pipeline wall is determined. As long as the supply current to the power supply electrode remains constant, the potential difference between a point on the pipeline wall and a point at infinity is a constant. It should be noted that the above-ground pipelines do not simply refer to pipelines existing on the ground, but only to rust-prone metal pipelines whose inner and outer walls can be contacted by the power supply and measuring electrodes. Based on this characteristic, refer to... Figure 1 , Figure 2 The first aspect of this application provides a method for detecting the corrosion degree of above-ground metal pipelines, comprising:

[0075] S101. Power supply electrodes and measuring electrode circuits are respectively installed on the inner or outer wall of the pipe to measure the potential of the non-corrosion layer at the measuring electrode measuring point on the inner or outer wall of the pipe.

[0076] like Figure 2 The measurement method shown is used to measure the resistance of the inner wall of a ground-level metal pipe. Power supply electrode A is used to provide current, and the measuring electrode circuit is used to measure the resistance of the rust layer inside the pipe. The measuring electrode circuit includes measuring electrode B, a first measuring circuit, and a second measuring circuit. The first measuring circuit and the second measuring circuit are connected in series with measuring electrode B, and are also connected in parallel. The first measuring circuit includes a first potentiometer and a first ammeter connected in series, and the second measuring circuit includes a second potentiometer and a second ammeter connected in series. It should be noted that the internal resistances of the first potentiometer V1 and the second potentiometer V2 are different.

[0077] S102. Based on the potential distribution of the inner or outer wall of the pipe, the resistance of the corrosion layer at the measuring point of the measuring electrode on the inner or outer wall of the pipe is measured using a measuring circuit.

[0078] Combination Figure 2When the power supply to electrode A is turned on, switch k is first set to position 1. The first measuring circuit measures and records the readings V1 and I1 of the first potentiometer and the first ammeter. Then the readings of the first potentiometer and the ammeter satisfy...

[0079] I1R r +I1(R V1 +R I1 )=U, (1)

[0080] Among them, R V1 ,R I1 These are the internal resistances of the first potentiometer and the first ammeter, respectively, and U is the potential of the non-corroded metal pipe wall.

[0081] Keeping the power supply to electrode A connected, switch k is then switched to position 2. The first measuring circuit measures and records the readings V2 and I2 of the second potentiometer and the second ammeter. Since the resistances of the first and second potentiometers are large, they have almost no effect on the potential distribution in the pipe. Therefore, the readings of the second potentiometer and the second ammeter satisfy...

[0082] I2R r +I2(R V2 +R I2 )=U, (2)

[0083] Where R V2 ,R I2 These are the internal resistances of the second potentiometer and the second ammeter, respectively.

[0084] Using the above measurement data, solve the potential U and resistance R in the above equation system (1)-(2). r This value represents the accurate potential of the non-corroded pipe wall at the measuring electrode B after eliminating the influence of the electrode measurement environment, and the resistance of the corrosion layer.

[0085] As can be seen from the above measurement method, the above embodiment only addresses the accurate potential of the non-corroded pipe wall at measurement point B of the measuring electrode after eliminating the influence of the electrode measurement environment on the inner wall rust layer. Therefore, [the following is a more detailed explanation of the measurement method and its application]: Figure 2 The power supply motor A and measuring electrode B are set on the outer wall of the pipe, which can also be used to measure the resistance and potential of the corrosion layer on the outer wall of the pipe.

[0086] S103. Measure the thickness of the corrosion layer in the pipeline by measuring the resistance of the corrosion layer at the measuring electrode on the inner or outer wall of the pipeline.

[0087]

[0088] Where δ is the thickness of the rust layer, S is the contact area between the measuring electrode and the pipe wall, and ρ r The resistivity of the corrosion layer on the pipeline.

[0089] Of course, the above refers to above-ground pipelines. However, many pipelines, such as oil pipelines and urban water supply pipelines, are buried deep underground. Measuring the resistance of the outer wall corrosion layer by contacting the measuring electrodes with the pipeline's outer wall is not feasible. To measure the pipeline's outer wall resistance, the ground would need to be excavated to expose the buried pipeline, which would be very labor-intensive and costly. Therefore, the only way to indirectly measure the resistance is by installing power supply and measuring electrode circuits inside the pipeline. While through-casing resistivity logging can successfully measure the equivalent total lateral resistance of the formation, it cannot specifically determine the resistance of the outer wall corrosion layer. This constitutes an underdetermined problem. Based on this, the second aspect of this application, referring to... Figure 3 , Figure 4 , Figure 5 A method for detecting the corrosion degree of buried metal pipelines is provided, comprising:

[0090] S201. A power supply electrode and a measuring electrode circuit are installed on the inner wall of the pipe to measure the actual potential of the non-corrosion layer at the measuring electrode measurement point on the inner wall of the pipe. It is understood that the installation of the power supply electrode and measuring electrode circuit on the inner wall of the pipe can be achieved in any way. It can be done by using a specialized robot to carry the power supply electrode and measuring electrode circuit and attaching it to the inner wall of the pipe, or by other methods that can replace the robot and achieve the same effect, as long as the power supply electrode and measuring electrode circuit are installed on the inner wall of the pipe and make good contact with the inner wall. There are no specific limitations on how the power supply electrode and measuring electrode circuit are installed on the inner wall of the pipe.

[0091] It is understandable that the power supply electrode circuit and measuring electrode circuit installed on the inner wall of the buried metal pipeline are the same as those of the above-ground metal pipeline.

[0092] S202. Construct a geological model of the pipeline transmission line with the pipeline center as the origin, the pipeline axis as the z-axis, and the pipeline radial axis as the r-axis.

[0093] S203. Based on the pipeline transmission line stratum model and the flow of fluid and current in the pipeline along the pipeline axis, construct the equivalent longitudinal conductivity of the fluid in the pipeline, the non-corroded inner wall of the pipeline, and the corrosion layer of the inner wall of the pipeline.

[0094] Furthermore, the equivalent bus conductance is

[0095] S = S f +S C +S r (4)

[0096] in

[0097] R is the total equivalent longitudinal (axial) resistance per unit length.

[0098] The resistance per unit length of the fluid in the axial water supply pipe;

[0099] ρ f The resistivity of the fluid inside the pipe;

[0100] a1 is the inner radius of the pipe corrosion layer;

[0101] R c The resistance per unit length of a non-corroded water supply pipe along the axial direction;

[0102] R r =ρ r / [2πa2(a3-a2)] is the resistance per unit length of the rust layer inside the water supply pipe along the axial direction, σ r =1 / ρ r ;

[0103] a2 is the inner radius of the non-corrosion pipe, and a3 is the outer radius of the non-corrosion pipe;

[0104] σ r The conductivity of the corrosion layer on the pipeline.

[0105] S204. Based on the equivalent longitudinal conductivity, determine the transmission line equation of the pipeline.

[0106] Furthermore, the pipeline transmission line equation can be written as:

[0107]

[0108]

[0109] Equations (5a) and (5b) are called the underground pipeline transmission line equations, where U is the potential distribution of the non-corrosive water supply pipeline wall and I is the current in the non-corrosive water supply pipeline wall. T is the lateral resistance of the formation (the formation resistance per unit length of the pipeline), such as Figure 5 As shown, the transverse resistance per unit length of pipe in the i-th layer along the axial direction (z-axis) is:

[0110]

[0111] Where r is the radial radius of the formation, R str Formation equivalent lateral resistance.

[0112] S205. Calculate the transmission line equation of the pipeline and determine the calculated potential of the non-corrosion layer on the inner wall of the pipeline.

[0113] The solution to the pipeline transmission line equation in the i-th axial stratum is:

[0114]

[0115] Where A i B i The coefficient ξ is undetermined and can be determined using the continuous boundary conditions of interface current and potential. i =T i α i d i (i = 1, 2, ..., n) represents the z-coordinate of the interface of the i-th layer along the axis.

[0116] If we assume the outer formation is a homogeneous, infinitely large formation and the fluid inside the well is a homogeneous fluid, then equation (5) has an analytical solution.

[0117]

[0118] d i (i = 1, 2…n) represents the z-coordinate of the interface of the i-th layer along the axial direction of the pipeline transmission line geological model, T i Let ξ be the transverse resistance of the i-th layer. i =T i α i α i Let α be the coefficient of the i-th stratum, u0 be the potential of the pipe wall at z = 0, and R be the potential of the stratum. r lateral resistance of the corrosion layer on the outer wall of the pipe, R Str This represents the lateral resistance of the formation.

[0119] Equations (7a) and (7b) are the solutions U obtained from equations (1) and (2), which are the measurement potential values ​​of the non-corroded pipe wall at the measurement point of the measuring electrode after eliminating the influence of the electrode measurement environment.

[0120] S206. Calculate the partial derivatives of the potential with respect to the formation parameters of the pipeline transmission line formation model using the potential Jacobi matrix.

[0121] Furthermore, the geological model of the pipeline transmission line is divided into elements along the pipeline. Each small element is defined as having constant parameters, and the model parameter (resistance) vector is... N z U is the total number of parameters, and the p-th observation is U. p (Electric potential), then U p =U p (m), p=1,2…M q M q Let the initial value of the model be the number of observation data. In m 0 Point U p Expanding into a Taylor series and taking the first-order approximation, we have:

[0122]

[0123] Furthermore, based on the unit-divided pipeline transmission line stratigraphic model, the Jacobi matrix form is determined, and the matrix form is as follows:

[0124] ΔU=GΔm (8b)

[0125] ΔU is the potential increment, Δm is the increment of formation parameters around the formation in the pipeline transmission line formation model, and G is the partial derivative of the potential with respect to the formation parameters, also known as the potential gradient.

[0126]

[0127] Furthermore, the location of the measuring electrode in the pipeline transmission line stratum model is determined. Since the application employs a point-based measurement method using the measuring electrode as described above, and based on the pipeline transmission line equation assumptions, the measured value should be the transverse resistance at the measuring electrode's measurement point. Let the location of the measuring electrode be the i-th layer of the stratum, and the potential calculated from equations (5a) and (5b) be U. i The initial lateral resistance of the pipeline transmission line ground model is:

[0128] Based on the above description, there are two unknown parameters, namely... and To determine the partial derivatives of the potential with respect to formation parameters, let... From equation (8c), the G (partial derivative of electric potential with respect to formation parameters) for this measurement method is:

[0129]

[0130] in

[0131]

[0132]

[0133]

[0134]

[0135] If we assume the outer formation is a homogeneous, infinitely large formation and the fluid inside the well is a homogeneous fluid, then we have:

[0136]

[0137]

[0138] In the formula, the subscript i represents the i-th stratum, and G1 and G2 are the derivatives of the potential of the i-th stratum with respect to the lateral resistance of the pipe wall and the lateral resistance of the stratum, respectively.

[0139] S207. Determine the inversion objective function by measuring and calculating the potential.

[0140] Let the inversion objective function be...

[0141] F(m) = ||UU obs || (10)

[0142] Among them U obs The measured potential is the potential of the non-corroded pipe wall actually measured through the power supply electrode and measuring electrode circuit. Figure 1 The potential measured by the measurement mode is obtained by solving equations (1) and (2). U is the calculated potential, which is the non-corroded pipe wall potential calculated by the pipeline transmission line equation.

[0143] S208. Using the pipeline transmission line equation and the partial derivative of the potential with respect to the formation parameters, the resistance of the corrosion layer on the outer wall of the pipeline is calculated by inversion iterative approximation through inversion objective function.

[0144] Let f(m) = UU obs If m k For the k-th inversion iteration approximation of m, the iterative residual vector (in the form of formula (8b)) is minimized.

[0145] d k =-(G k T G k ) -1 G k T f k (11a)

[0146] m k+1 =m k +λ k d k (11b)

[0147] λ k Let G be the step size calculated in the k-th iteration. In equation (5), matrix G sometimes appears. k T G k To improve computational speed and stability, a positive definite diagonal matrix is ​​added to G in cases of singularity or near-singularity. k T G k The matrix is ​​then transformed into a symmetric positive definite matrix with a better condition number (Marquardt method), and the inversion iterative formula is modified as follows:

[0148] d k =-(G k T G k +β k I)-1 G k T f k (11c)

[0149] Where I is an n-order identity matrix, β k It is a positive real constant, which is appropriately selected through trial calculations based on the required calculation accuracy.

[0150] With appropriate iterations, the resistance of the outer rust layer of the metal pipe can be calculated.

[0151] S209. Calculate the thickness of the corrosion layer on the outer wall of the pipe based on the resistance of the corrosion layer. Here, by iteratively calculating the resistance of the corrosion layer on the outer wall of the pipe, the thickness δ of the corrosion layer on the outer wall of the pipe can be calculated by using the formula (3) above for calculating the thickness of the corrosion layer based on the resistance of the corrosion layer.

[0152] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this application (including the claims) is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this application as described above, which are not provided in the details for the sake of brevity.

[0153] Additionally, to simplify the description and discussion, and to avoid obscuring the embodiments of this application, the provided drawings may or may not show well-known power or ground connections to integrated circuit (IC) chips and other components. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the embodiments of this application, and this also takes into account the fact that the details of implementation of these block diagram apparatuses are highly dependent on the platform on which the embodiments of this application will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details (e.g., circuits) have been set forth to describe exemplary embodiments of this application, it will be apparent to those skilled in the art that the embodiments of this application can be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0154] Although this application has been described in conjunction with specific embodiments thereof, many substitutions, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description.

[0155] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A method for detecting the degree of corrosion of above-ground metal pipelines, characterized in that, include: By setting power supply electrodes and measuring electrode circuits on the inner or outer wall of the pipe respectively, the potential of the non-corrosion layer at the measuring electrode measuring point on the inner or outer wall of the pipe is measured. Based on the potential distribution of the inner or outer wall of the pipe, the resistance of the corrosion layer at the measuring electrode measuring point on the inner or outer wall of the pipe is measured using a measuring circuit. The thickness of the corrosion layer in the pipe is measured based on the resistance of the corrosion layer measured by the measuring electrode on the inner or outer wall of the pipe. The measuring electrode circuit includes a measuring electrode, a first measuring circuit, and a second measuring circuit. The first measuring circuit and the second measuring circuit are connected in series with the measuring electrode, and the first measuring circuit and the second measuring circuit are connected in parallel. The first measuring circuit includes a first potentiometer and a first ammeter connected in series, and the second measuring circuit includes a second potentiometer and a second ammeter connected in series.

2. The method according to claim 1, characterized in that, The formula for calculating the electric potential of the pipe wall is as follows: I1R r +I1(R V1 +R I1 )=U I2R r +I2(R V2 +R I2 )=U Among them, R r To measure the resistance of the corrosion layer at the electrode measurement point, I1 is the reading of the first ammeter, R. V1 R is the resistance of the first potentiometer. I1 The resistance of the first ammeter, I2, is the reading of the second ammeter; R V2 R is the resistance of the second point differential meter. I2 The resistance of the second ammeter is denoted by , and U is the potential of the non-corroded pipe wall.

3. The method according to claim 2, characterized in that, The formula for calculating the thickness of the corrosion layer on the pipeline is as follows: Where δ is the thickness of the rust layer, S is the contact area between the measuring electrode and the pipe, and ρ r The resistivity of the corrosion layer on the pipeline.

4. A method for detecting the corrosion degree of buried metal pipelines, characterized in that, include: By setting power supply electrodes and measuring electrode circuits on the inner wall of the pipe, the measured potential of the non-corrosion layer at the measuring electrode measuring point on the inner wall of the pipe is measured. The measuring electrode circuit includes a measuring electrode, a first measuring circuit, and a second measuring circuit. The first measuring circuit and the second measuring circuit are connected in series with the measuring electrode, and the first measuring circuit and the second measuring circuit are connected in parallel. The first measuring circuit includes a first potentiometer and a first ammeter connected in series, and the second measuring circuit includes a second potentiometer and a second ammeter connected in series. A pipeline transmission line geological model is constructed with the center of the pipeline as the origin, the axial direction of the pipeline as the z-axis, and the radial direction of the pipeline as the r-axis. Based on the pipeline transmission line geological model and the flow of fluid and current in the pipeline along the pipeline axis, the equivalent longitudinal conductivity of the fluid in the pipeline, the non-corroded inner wall of the pipeline, and the corrosion layer of the inner wall of the pipeline is constructed. Based on the equivalent longitudinal conductivity, the pipeline transmission line equation is determined; Calculate the transmission line equation of the pipeline and determine the calculated potential of the non-corrosion layer on the inner wall of the pipeline; The partial derivatives of the potential with respect to the formation parameters of the pipeline transmission line formation model are calculated using the Jacobi potential matrix. The inversion objective function is determined by the measured potential and the calculated potential. Using the pipeline transmission line equation and the partial derivative of the potential with respect to the formation parameters, the resistance of the corrosion layer on the outer wall of the pipeline is calculated by inversion iterative approximation through inversion objective function; The thickness of the corrosion layer on the outer wall of the pipe is determined based on the resistance of the corrosion layer.

5. The method according to claim 4, characterized in that, The calculation formula for the equivalent longitudinal conductivity of the fluid, non-corroded pipe wall, and corroded layer in the pipe, based on the pipeline transmission baseline model and the flow of fluid and current along the pipe axis, is as follows: S=S f +S C +S r , in, R is the total equivalent longitudinal resistance per unit length in the axial direction; The resistance per unit length of the fluid in the axial water supply pipe; ρ f The resistivity of the fluid inside the pipe; a1 is the inner radius of the pipe corrosion layer; R c The resistance per unit length of a non-corroded water supply pipe along the axial direction; R r =ρ r / [2πa2(a3-a2)] is the resistance per unit length of the rust layer inside the water supply pipe along the axial direction, σ r =1 / ρ r ; a2 is the inner radius of the non-corrosion pipe, and a3 is the outer radius of the non-corrosion pipe; σ r The conductivity of the corrosion layer on the pipeline.

6. The method according to claim 5, characterized in that, Based on the equivalent longitudinal conductivity, the formula for calculating the pipeline transmission line equation is determined as follows: Wherein, U represents the potential distribution of the non-corroded water supply pipe wall; I represents the current in the non-corrosion-resistant water supply pipe wall; T is the lateral resistance of the formation, and α is the formation α coefficient.

7. The method according to claim 6, characterized in that, The partial derivatives of the potential with respect to the formation parameters of the pipeline transmission line formation model are calculated using the Jacobi potential matrix, including: The geological model of the pipeline transmission line is divided into units along the pipeline; Based on the pipeline transmission line stratigraphic model divided by the aforementioned units, the form of the Jacobi matrix is ​​determined. Determine the location of the measuring electrode in the formation model of the pipeline transmission line; Based on the Jacobi matrix form and the location of the measuring electrode in the pipeline transmission line formation model, the partial derivatives of the potential of the transmission line formation model with respect to the formation parameters are determined.

8. The method according to claim 7, characterized in that, The Jacobi matrix is ​​in the form of: ΔU=GΔm, Where ΔU is the potential increment and Δm is the perturbation increment of the pipeline transmission line formation model parameters; Resistance vector of the transmission line stratigraphic model divided into cells; The potential of the transmission line stratum model divided into units.

9. The method according to claim 8, characterized in that, Using the pipeline transmission line equation and the partial derivative of the potential with respect to the formation parameters, the resistance of the outer corrosion layer of the pipeline is calculated by inversion iterative approximation through inversion objective function; The formula for calculating the inversion objective function is as follows: F(m)=||U-U obs || Among them, U obs To measure the potential of the non-corroded pipe wall; U represents the potential of the non-corroded pipe wall.

10. The method according to claim 9, characterized in that, The inversion iterative approximation formula is: Where d k This represents the increment of formation parameters obtained in the k-th iteration; G k T G k This is the product of the partial derivative matrices of the pipeline transmission line equations; I is an n-order identity matrix, β k It is a positive real constant.

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