CN116297128A - Ground metal pipeline and buried metal pipeline rust degree detection method - Google Patents
Ground metal pipeline and buried metal pipeline rust degree detection method Download PDFInfo
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Abstract
The application provides a method for detecting rust degree of an overground metal pipeline and a buried metal pipeline, wherein the method for detecting rust degree of the overground pipeline comprises the following steps: measuring the potential of a non-rusted layer of a measuring point of the measuring electrode on the inner wall or the outer wall of the pipeline by respectively arranging a power supply electrode and a measuring electrode circuit on the inner wall or the outer wall of the pipeline; measuring the resistance of the rust layer of the measuring point of the electrode measuring electrode by using a measuring circuit based on the potential distribution of the inner wall or the outer wall of the pipeline; measuring the resistance of the rust layer at the measuring point of the electrode based on the inner wall or the outer wall of the pipeline, and measuring the thickness of the rust layer of the pipeline; the method for detecting the rust degree of the buried metal pipeline comprises the following steps: by arranging a power supply electrode and a measuring electrode circuit on the inner wall of a pipeline, respectively taking the center of the pipeline as an origin, taking the axial direction of the pipeline as a z axis, constructing a pipeline transmission line stratum model by taking the radial direction of the pipeline as an r axis, constructing equivalent longitudinal conductance of fluid in the pipeline, the inner wall of a non-rusted pipeline and rusted layers on the inner wall of the pipeline, determining a pipeline transmission line equation, and calculating the resistance and thickness of rusted layers on the outer wall of the pipeline.
Description
Technical Field
The application relates to the technical field of pipeline detection and maintenance, in particular to an on-ground metal pipeline and a buried metal pipeline rust degree detection method.
Background
The water resource is an important factor affecting the human living standard, the social stability and the economic development, and the urban water supply system is taken as an infrastructure for human to convey and utilize the water resource, is a sign of the urban development state and the accommodation capacity, and is a basic factor for guaranteeing the urban development. However, because the urban underground pipeline is affected by various complex factors, various defects can be inevitably caused in the operation period of the pipeline, a large number of buried oil and water supply pipelines are in a damaged working state, leakage of oil and water supply pipelines is extremely easy to cause, the most common and serious problem is corrosion phenomenon, corrosion can be continuously aggravated along with the increase of the service time of the pipeline, even perforation and rupture of the pipeline can be caused, and safety accidents occur.
At present, the method for detecting the rust in the pipelines at home and abroad mainly comprises ultrasonic waves, magnetic leakage, vortex, transient electromagnetic and the like, but one common problem of the detection technologies is that the detection precision of the rust in the pipelines is not high, the localization is high, and the direct measurement and estimation of the resistance of the rust layer or the thickness of the rust layer are difficult to realize. The pipeline is generally inspected and maintained only after the safety accident occurs, so that the resource waste and economic loss are caused, and even the problems of personal injury, building collapse, environmental pollution and the like are possibly caused.
Disclosure of Invention
In view of the foregoing, it is an object of the present application to provide a method for detecting rust of an above-ground metal pipe and a buried metal pipe, which overcomes the above-mentioned problems.
In view of the above object, a first aspect of the present application provides a method for detecting rust of an overground metal pipe, including:
the method comprises the steps that a power supply electrode and a measuring electrode circuit are respectively arranged on the inner wall or the outer wall of a pipeline, and the potential of a non-rusted layer of a measuring point of the measuring electrode on the inner wall or the outer wall of the pipeline is measured;
measuring the resistance of the rust layer of the measuring point of the electrode measuring electrode of the inner wall or the outer wall of the pipeline by using a measuring circuit based on the potential distribution of the inner wall or the outer wall of the pipeline;
measuring the thickness of the pipeline corrosion layer based on the resistance of the corrosion layer of the measuring point of the measuring electrode of the inner wall or the outer wall of the pipeline;
the measuring electrode circuit comprises a measuring electrode, a first measuring circuit and a second measuring circuit, the first measuring circuit and the second measuring circuit are respectively connected with the measuring electrode in series, the first measuring circuit and the second measuring circuit are connected in parallel, the first measuring circuit comprises a first potentiometer and a first ammeter which are connected in series, and the second measuring circuit comprises a second potentiometer and a second ammeter which are connected in series.
Optionally, the calculation formula for measuring the electric potential of the pipe wall is:
I 1 R r +I 1 (R V1 +R I1 )＝U
I 2 R r +I 2 (R V2 +R I2 )＝U
wherein R is r To measure the resistance of the rust layer of the electrode measuring point, I 1 First ammeter reading, R V1 R is the resistance of the first potentiometer I1 Resistance of the first ammeter, I 2 Reading for a second ammeter; r is R V2 Resistance of second point level difference meter, R I2 And U is the potential of the pipeline wall of the non-rusting layer for the resistance of the second ammeter.
Optionally, a calculation formula for measuring the thickness of the pipeline corrosion layer is as follows:
wherein delta is the thickness of the rust layer, S is the contact area between the measuring electrode and the pipeline, and ρ is r Is the resistivity of the rust layer of the pipeline.
In a second aspect of the present application, a method for detecting rust of a buried metal pipe is provided, including:
a power supply electrode and a measuring electrode circuit are arranged on the inner wall of the pipeline, and the measured potential of a non-rust layer at a measuring point of the measuring electrode on the inner wall of the pipeline is measured; the measuring electrode circuit comprises a measuring electrode, a first measuring circuit and a second measuring circuit, wherein the first measuring circuit and the second measuring circuit are respectively connected with the measuring electrode in series, the first measuring circuit and the second measuring circuit are connected in parallel, the first measuring circuit comprises a first potential difference meter and a first ammeter which are connected in series, and the second measuring circuit comprises a second potential difference meter and a second ammeter which are connected in series;
respectively taking the center of the pipeline as an origin, taking the axial direction of the pipeline as a z axis, and constructing a pipeline transmission line stratum model by taking the radial direction of the pipeline as an r axis;
based on the pipeline transmission line stratum model, the fluid in the pipeline and the current in the pipeline flowing along the axial direction of the pipeline, constructing equivalent longitudinal conductance of the fluid in the pipeline, the non-rusted pipeline inner wall and the rusted layer on the pipeline inner wall;
determining the pipeline transmission line equation based on the equivalent longitudinal conductance;
calculating the pipeline transmission line equation and determining the calculated potential of the non-rusting layer of the pipeline wall;
calculating the partial derivative of the potential of the pipeline transmission line stratum model to stratum parameters through a potential Jacobi matrix;
determining an inversion objective function from the measured potential and the calculated potential;
calculating the resistance of the rusted layer on the outer wall of the pipeline by inverting iterative approximation through an inversion objective function by utilizing the pipeline transmission line equation and the partial derivative of the potential to the stratum parameter;
and calculating the thickness of the pipeline outer wall corrosion layer according to the resistance of the pipeline outer wall corrosion layer.
Optionally, the calculation formula for constructing equivalent longitudinal conductance of the fluid in the pipeline, the non-rusted pipeline wall and the rusted layer in the pipeline based on the pipeline transmission bottom line model, the fluid in the pipeline and the current in the pipeline flowing along the axial direction of the pipeline is as follows:
S＝S f +S C +S r ，
wherein,,
r is the total equivalent longitudinal resistance of the axial unit length;
ρ f is the resistivity of the fluid in the pipeline;
a 1 is the inner radius of the pipeline rust layer;
R c a resistance per unit length of the water supply pipe which is non-rusted along the axial direction;
R r ＝ρ r /[2πa 2 (a 3 -a 2 )]for the resistance per unit length of the rust layer in the water supply pipe in the axial direction, sigma r ＝1/ρ r ；
a 2 Is the radius of the inner wall of a non-rusted pipeline, a 3 Is the radius of the outer wall of the non-rusted pipeline;
σ r is the conductivity of the rust layer of the pipeline.
Optionally, the determining the equation of the pipeline transmission line based on the equivalent longitudinal conductance is calculated as:
wherein U is the potential distribution of the wall of the non-rust water supply pipeline;
i is the current in the non-rusting water supply pipe wall;
Optionally, calculating the partial derivative of the electric potential of the pipeline transmission line stratum model to the stratum parameter through an electric potential Jacobi matrix comprises:
performing unit division on the pipeline transmission line stratum model along the pipeline;
determining the Jacobi matrix form based on the unit-divided pipeline transmission line stratum model;
determining the position of the pipeline transmission line stratum model where the measuring electrode is positioned;
and determining partial derivatives of electric potential of the transmission line stratum model to stratum parameters based on the Jacobi matrix form and the position of the pipeline transmission line stratum model where the measuring electrode is positioned.
Optionally, the Jacobi matrix is in the form of:
ΔU＝GΔm，
wherein DeltaU is an electric potential increment, deltam is a pipeline transmission line stratum model parameter perturbation increment;
Optionally, calculating the resistance of the outer rust layer of the pipeline by inverting iterative approximation of an inversion objective function by using the pipeline transmission line equation and the partial derivative of the potential to the stratum parameter;
the calculation formula of the inversion objective function is as follows:
F(m)＝||U-U obs ||
wherein U is obs For the measured non-rusting pipe wall potential;
u is the non-rusting pipe wall potential.
Optionally, the inversion iterative approximation formula is:
d k ＝-(G k T G k +β k I) -1 G k T f k
wherein d is k The stratum parameter increment obtained for the kth iteration;
G k T G k a partial derivative matrix product of a pipeline transmission line equation;
i is an n-order identity matrix, beta k Is a positive real constant.
According to the above, the method for detecting the corrosion degree of the overground pipeline can directly measure and calculate the thickness of the corrosion layer of the inner wall and the outer wall of the pipeline through the power supply electrode and the measuring electrode circuit, and the method for detecting the corrosion degree of the buried pipeline is provided, a calculation method for the transverse resistance of the transmission line stratum model, the equivalent transverse resistance of the corrosion pipeline and the fluid in the pipeline is provided through establishing the pipeline transmission line stratum model, the calculation of the potential distribution of the non-corrosion pipeline wall is realized by means of a pipeline transmission line equation, the resistance and the thickness of the corrosion layer of the outer wall of the pipeline are inverted based on the pipeline wall potential, the measurement and the evaluation of the residual thickness of the corrosion pipeline wall are realized, the state of the current pipeline is accurately mastered in time, scientific safety evaluation is made on the pipeline through the state of the current pipeline, relevant maintenance suggestions are given, the failure risk of the pipeline is reduced, and unnecessary economic loss is avoided.
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In order to more clearly illustrate the technical solutions of the present application or related art, the drawings that are required to be used in the description of the embodiments or related art will be briefly described below, and it is apparent that the drawings in the following description are only embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort to those of ordinary skill in the art.
FIG. 1 is a flow chart of a method for detecting rust of an overground metal pipeline according to an embodiment of the application;
FIG. 2 is a schematic diagram of an above-ground metal pipeline and a power supply detection mode according to an embodiment of the present application;
FIG. 3 is a flowchart of a method for detecting rust of a buried metal pipeline according to an embodiment of the present application;
FIG. 4 is a schematic view of a rusted pipe according to an embodiment of the present application;
fig. 5 is a schematic diagram of a metal pipeline transmission line formation model according to an embodiment of the present application.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail below with reference to the accompanying drawings.
It should be noted that unless otherwise defined, technical or scientific terms used in the embodiments of the present application should be given the ordinary meaning as understood by one of ordinary skill in the art to which the present application belongs. The terms "first," "second," and the like, as used in embodiments of the present application, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", etc. are used merely to indicate relative positional relationships, which may also be changed when the absolute position of the object to be described is changed.
In the process of measuring the corrosion resistance of the overground pipeline, when the power supply electrode is in good contact with the pipeline wall, the potential distribution of the pipeline wall is determined, and as long as the power supply current of the power supply electrode is unchanged, the potential difference between a point position of a certain point on the pipeline wall and an infinity point position is constant. The above-mentioned above-ground pipe does not simply refer to a pipe existing on the ground, but merely refers to a metal-based pipe which may rust by contacting the inner wall and the outer wall of the pipe with a power supply electrode and a measurement electrode. According to this feature, referring to fig. 1 and 2, in a first aspect of the present application, there is provided a method for detecting rust of an overground metal pipe, including:
s101, respectively arranging a power supply electrode and a measuring electrode circuit on the inner wall or the outer wall of the pipeline, and measuring the potential of a non-rusted layer of a measuring point of the measuring electrode on the inner wall or the outer wall of the pipeline.
The measuring method shown in fig. 2 is to realize the inner wall of the overground metal pipeline, the power supply electrode A is used for providing current, the measuring electrode circuit is used for measuring the resistance of the rust layer in the pipeline, wherein the measuring electrode circuit comprises a measuring electrode B, a first measuring circuit and a second measuring circuit, the first measuring circuit and the second measuring circuit are respectively connected in series with the measuring electrode B, and simultaneously connected in parallel, the first measuring circuit comprises a first potential difference meter and a first ammeter which are connected in series, the second measuring circuit comprises a second potential difference meter and a second ammeter which are connected in series, and the first potential difference meter V is that 1 With a second potentiometer V 2 Is different.
S102, measuring the resistance of the rust layer of the measuring point of the electrode measuring point by using a measuring circuit based on the potential distribution of the inner wall or the outer wall of the pipeline.
Referring to FIG. 2, the power supply electrode A is powered on, the switch k is first turned on to the 1 position, the first measuring circuit measures, and the readings V of the first potentiometer and the first ammeter are recorded 1 And I 1 The first potentiometer and ammeter readings satisfy
I 1 R r +I 1 (R V1 +R I1 )＝U， (1)
Wherein R is V1 ,R I1 The internal resistances of the first potentiometer and the first ammeter are respectively shown, and U is the potential of the non-rusted metal pipeline wall.
Keeping the power-on state of the power supply electrode A unchanged, combining the switch k to the position of 2, measuring by the first measuring circuit, and recording the readings V of the second potentiometer and the second ammeter 2 And I 2 Because the first potentiometer and the second potentiometer have large resistance and have little influence on the potential distribution of the pipeline, the readings of the second potentiometer and the second ammeter meet the requirement
I 2 R r +I 2 (R V2 +R I2 )＝U， (2)
Wherein R is V2 ,R I2 The internal resistances of the second potentiometer and the second ammeter are respectively.
Solving the electric potential U and the electric resistance R in the above equation sets (1) - (2) by using the above measurement data r The value is the accurate potential and the resistance of the rusting layer of the non-rusting pipeline wall of the measuring point B of the measuring electrode after the influence of the electrode measuring environment is eliminated.
According to the measuring method, in the above embodiment, only the accurate potential of the non-rusted pipeline wall and the resistance of the rusted layer of the pipeline inner wall at the measuring point of the measuring electrode B after the environmental influence is eliminated by the rusted layer of the pipeline inner wall is measured, so that the power supply motor A and the measuring electrode B in FIG. 2 are arranged on the pipeline outer wall, and the measurement of the resistance and the potential of the rusted layer of the pipeline outer wall can be realized.
S103, measuring the resistance of the rust layer of the electrode measuring point based on the inner wall or the outer wall of the pipeline, and measuring the thickness of the rust layer of the pipeline.
Wherein delta is the thickness of the rust layer, S is the contact area between the measuring electrode and the wall of the pipeline, and ρ r Is the resistivity of the rust layer of the pipeline.
Of course, the above is directed to an above-ground pipeline, but many similar oil and urban water supply pipelines are deeply buried underground, the above measuring electrode contacts the outer wall of the pipeline to measure the corrosion layer resistance of the outer wall of the pipeline, if the outer wall resistance of the pipeline is to be measured, the ground needs to be excavated to expose the buried pipeline, the workload becomes great, and the cost is high, the above measuring electrode is only indirectly realized by arranging a power supply electrode and a measuring electrode circuit on the inner wall of the pipeline, at this time, the equivalent total transverse resistance of the stratum can be successfully measured by casing resistivity logging, but the corrosion layer resistance of the outer wall of the pipeline cannot be specifically obtained, which constitutes an underdetermined problem, and in this way, according to a second aspect of the application, referring to fig. 3, 4 and 5, a buried metal pipeline corrosion degree detecting method is provided, which comprises:
s201, a power supply electrode and a measuring electrode circuit are arranged on the inner wall of the pipeline, and the measured potential of a non-rust layer at a measuring point of the measuring electrode on the inner wall of the pipeline is measured. It will be appreciated that the arrangement of the power supply electrode and the measuring electrode circuit on the inner wall of the pipe may be achieved in any manner, and the power supply electrode and the measuring electrode circuit may be attached to the inner wall of the pipe by a special robot, or may be provided by other means which may replace the robot and which may perform the same function as the robot, as long as the power supply electrode and the measuring electrode circuit may be arranged on the inner wall of the pipe and in good contact with the inner wall of the pipe, and the manner of how to arrange the power supply electrode and the measuring electrode circuit on the inner wall of the pipe is not particularly limited.
It is to be understood that the power supply electrode circuit and the measuring electrode circuit provided on the inner wall of the buried metal pipe are identical to the power supply electrode and the measuring electrode circuit of the above-ground metal pipe.
S202, respectively taking the center of a pipeline as an origin, taking the axial direction of the pipeline as a z axis and taking the radial direction of the pipeline as an r axis to construct a pipeline transmission line stratum model.
S203, constructing equivalent longitudinal conductance of the fluid in the pipeline, the non-rusted pipeline inner wall and the rusted layer on the pipeline inner wall based on the pipeline transmission line stratum model, the fluid in the pipeline and the current in the pipeline flowing along the axial direction of the pipeline.
Further, the equivalent bus conductance is
S＝S f +S C +S r ， (4)
Wherein the method comprises the steps of
R is the total equivalent longitudinal (axial) resistance per axial unit length;
ρ f is the resistivity of the fluid in the pipeline;
a 1 is the inner radius of the pipeline rust layer;
R c a resistance per unit length of the water supply pipe which is non-rusted along the axial direction;
R r ＝ρ r /[2πa 2 (a 3 -a 2 )]for the resistance per unit length of the rust layer in the water supply pipe in the axial direction, sigma r ＝1/ρ r ；
a 2 Is the radius of the inner wall of a non-rusted pipeline, a 3 Is the radius of the outer wall of the non-rusted pipeline;
σ r is the conductivity of the rust layer of the pipeline.
S204, determining a pipeline transmission line equation based on the equivalent longitudinal conductance.
Further, the pipeline equation may be written as
Equations (5 a) and (5 b) are referred to as underground pipeline transmission line equations, U is the non-corrosive water supply pipeline wall potential distribution, I is the current in the non-corrosive water supply pipeline wall,
t is the formation transverse resistance (the formation resistance corresponding to the unit length of the pipeline), as shown in FIG. 5, the transverse resistance corresponding to the unit length of the pipeline in the axial (z-axis) ith layer is
Wherein R is the radial radius of the stratum, R str Formation equivalent lateral resistance.
S205, calculating a pipeline transmission line equation, and determining the calculated potential of the non-rusting layer on the inner wall of the pipeline.
Then the solution of the pipeline transmission line equation in the axial ith formation is
Wherein A is i 、B i For the undetermined coefficients, ζ can be determined using continuous boundary conditions at interface current and potential i ＝T i α i ，d i (i=1, 2 … n) is the z coordinate of the axial i-th layer interface.
If the outer stratum is a uniform infinite stratum and the fluid in the well is uniform, the equation (5) has an analytical solution
d i (i=1, 2 … n) is the z coordinate, T, of the axial ith layer interface of the pipeline transmission line stratum model i Is the i-th layer transverse resistance, xi i ＝T i α i ，α i Alpha coefficient of the ith stratum, u 0 For z=0 potential of the pipe wall, R r Pipeline outer wall rust layer transverse resistance R Str Is the formation lateral resistance.
Equations (7 a) and (7 b) are solutions U obtained in equations (1) and (2), and are measurement potential values of non-rusted pipeline walls of measurement points of the measurement electrodes after the influence of the electrode measurement environment is eliminated.
S206, calculating partial derivatives of the electric potential of the pipeline transmission line stratum model to stratum parameters through an electric potential Jacobi matrix.
Further, the pipeline transmission line stratum model is divided into units along the pipeline, and each small unit model parameter is set to be constant, and the model parameter (resistance) vector is set to be
N z The p-th observation data is U as the total parameter number p (potential), then there is U p ＝U p (m)，p＝1,2…M q ，M q For observing the number of data, the initial value of the model is set as
At m 0 Point U p Expanded into Taylor series and taken to be of first order approximation
Further, based on the pipeline transmission line stratum model of unit division, determining a Jacobi matrix form, wherein the matrix form is
ΔU＝GΔm (8b)
ΔU is the potential delta, Δm is the tubing string formation model formation parameter surrounding delta, and G is the potential partial derivative of the formation parameter, also known as the potential gradient. Then
Further, the position of the formation model of the pipeline transmission line where the measuring electrode is located is determined, and since in the above description, a point measurement mode of the measuring electrode is adopted in the application, it is assumed by the pipeline transmission line equation that the measured value measured in this mode should be the transverse resistance at the measuring point of the measuring electrode. Assuming that the position of the measuring electrode is the ith layer of the stratum, the potential calculated by equation (5 a) (5 b) is U i The initial value transverse resistance of the stratum model of the pipeline transmission line is
From the above description, there are two unknown parameters, respectively
And->
Then it is desirable to determine the partial derivative of the potential with respect to the formation parameter to provide/>
The G (potential partial derivative of formation parameter) of the present measurement from equation (8 c) is
Wherein the method comprises the steps of
If the outer stratum is a uniform infinite stratum, the fluid in the well is uniform, and the fluid is
Wherein the subscript i denotes the ith formation, G 1 、G 2 The derivatives of the stratum potential of the ith layer and the transverse resistance of the outer wall of the pipeline and the transverse resistance of the stratum are respectively obtained.
S207, determining an inversion objective function through actual measurement potential and calculation potential.
Let the inversion objective function be
F(m)＝||U-U obs || (10)
Wherein U is obs The measured potential, i.e. the measured potential of the non-rusted pipeline wall through the power supply electrode and the measuring electrode circuit, i.e. the measured potential through the measuring mode of fig. 1 and obtained by solving equations (1) and (2), and U is the calculated potential, i.e. the calculated potential of the non-rusted pipeline wall through the pipeline transmission line equation.
S208, calculating the resistance of the rusted layer on the outer wall of the pipeline by inversion iteration approximation through inversion objective function by utilizing the pipeline transmission line equation and the partial derivative of the potential to the stratum parameter.
Let f (m) =u-U obs If m k For the kth inversion iteration approximation of m, the objective function is minimized to an iteration residual vector (in the form of equation (8 b)) of
d k ＝-(G k T G k ) -1 G k T f k (11a)
m k+1 ＝m k +λ k d k (11b)
λ k Step size calculated for the kth iteration. In the formula (5), a matrix G may sometimes appear k T G k To add positive diagonal matrix to G for improved speed and stability of computation k T G k By the method, the matrix is changed into a symmetrical positive definite matrix (Marquardt method) with better condition number, and the inversion iteration formula is modified into
d k ＝-(G k T G k +β k I) -1 G k T f k (11c)
Wherein I is an n-order identity matrix, beta k Is a positive real constant and is properly selected by trial calculation according to the calculation accuracy requirement.
The resistance of the outer rust layer of the metal pipeline can be calculated through proper iteration
S209, calculating the thickness of the pipeline outer wall corrosion layer according to the resistance of the pipeline outer wall corrosion layer. Here, by iteratively calculating the resistance of the outer rust layer of the pipeline, the thickness δ of the outer rust layer of the pipeline can be calculated by the above formula for knowing the resistance of the rust layer and calculating the thickness of the rust layer, i.e., formula (3).
Those of ordinary skill in the art will appreciate that: the discussion of any of the embodiments above is merely exemplary and is not intended to suggest that the scope of the application (including the claims) is limited to these examples; the technical features of the above embodiments or in the different embodiments may also be combined within the idea of the present application, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present application as described above, which are not provided in detail for the sake of brevity.
Additionally, well-known power or ground connections to Integrated Circuit (IC) chips and other components may or may not be shown within the provided figures, in order to simplify the illustration and discussion, and so as not to obscure the embodiments of the present application. Furthermore, the devices may be shown in block diagram form in order to avoid obscuring the embodiments of the present application, and this also takes into account the fact that specifics with respect to implementation of such block diagram devices are highly dependent upon the platform on which the embodiments of the present application are to be implemented (i.e., such specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the application, it should be apparent to one skilled in the art that embodiments of the application can be practiced without, or with variation of, these specific details. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.
While the present application has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations of those embodiments will be apparent to those skilled in the art in light of the foregoing description.
The present embodiments are intended to embrace all such alternatives, modifications and variances which fall within the broad scope of the appended claims. Accordingly, any omissions, modifications, equivalents, improvements and/or the like which are within the spirit and principles of the embodiments are intended to be included within the scope of the present application.
Claims (10)
1. The method for detecting the rust degree of the overground metal pipeline is characterized by comprising the following steps of:
measuring the potential of a non-rusted layer of a measuring point of a measuring electrode on the inner wall or the outer wall of the pipeline by respectively arranging a power supply electrode and a measuring electrode circuit on the inner wall or the outer wall of the pipeline;
measuring the resistance of the rust layer of the measuring point of the electrode measuring electrode of the inner wall or the outer wall of the pipeline by using a measuring circuit based on the potential distribution of the inner wall or the outer wall of the pipeline;
measuring the thickness of the pipeline corrosion layer based on the resistance of the corrosion layer of the measuring point of the measuring electrode of the inner wall or the outer wall of the pipeline;
the measuring electrode circuit comprises a measuring electrode, a first measuring circuit and a second measuring circuit, the first measuring circuit and the second measuring circuit are respectively connected with the measuring electrode in series, the first measuring circuit and the second measuring circuit are connected in parallel, the first measuring circuit comprises a first potentiometer and a first ammeter which are connected in series, and the second measuring circuit comprises a second potentiometer and a second ammeter which are connected in series.
2. The method of claim 1, wherein the calculation formula for measuring the electrical potential of the conduit wall is:
I 1 R r +I 1 (R V1 +R I1 )＝U
I 2 R r +I 2 (R V2 +R I2 )＝U
wherein R is r To measure the resistance of the rust layer of the electrode measuring point, I 1 First ammeter reading, R V1 R is the resistance of the first potentiometer I1 Resistance of the first ammeter, I 2 Reading for a second ammeter; r is R V2 Resistance of second point level difference meter, R I2 And U is the potential of the pipeline wall of the non-rusting layer for the resistance of the second ammeter.
3. The method of claim 2, wherein the calculation formula for measuring the thickness of the pipe rust layer is:
wherein delta is the thickness of the rust layer, S is the contact area between the measuring electrode and the pipeline, and ρ is r Is the resistivity of the rust layer of the pipeline.
4. The method for detecting the rust degree of the buried metal pipeline is characterized by comprising the following steps of:
measuring the measured potential of a non-rust layer at a measuring point of a measuring electrode on the inner wall of the pipeline by arranging a power supply electrode and a measuring electrode circuit on the inner wall of the pipeline; the measuring electrode circuit comprises a measuring electrode, a first measuring circuit and a second measuring circuit, wherein the first measuring circuit and the second measuring circuit are respectively connected with the measuring electrode in series, the first measuring circuit and the second measuring circuit are connected in parallel, the first measuring circuit comprises a first potential difference meter and a first ammeter which are connected in series, and the second measuring circuit comprises a second potential difference meter and a second ammeter which are connected in series;
respectively taking the center of the pipeline as an origin, taking the axial direction of the pipeline as a z axis, and constructing a pipeline transmission line stratum model by taking the radial direction of the pipeline as an r axis;
based on the pipeline transmission line stratum model, the fluid in the pipeline and the current in the pipeline flowing along the axial direction of the pipeline, constructing equivalent longitudinal conductance of the fluid in the pipeline, the non-rusted pipeline inner wall and the rusted layer on the pipeline inner wall;
determining the pipeline transmission line equation based on the equivalent longitudinal conductance;
calculating the pipeline transmission line equation, and determining the calculated potential of the non-rusted layer on the inner wall of the pipeline;
calculating the partial derivative of the potential of the pipeline transmission line stratum model to stratum parameters through a potential Jacobi matrix;
determining an inversion objective function from the measured potential and the calculated potential;
calculating the resistance of the rusted layer on the outer wall of the pipeline by inverting iterative approximation through an inversion objective function by utilizing the pipeline transmission line equation and the partial derivative of the potential to the stratum parameter;
and determining the thickness of the pipeline outer wall corrosion layer according to the resistance of the pipeline outer wall corrosion layer.
5. The method of claim 4, wherein the calculation formula for constructing equivalent longitudinal conductance of the fluid in the pipeline, the non-rusted pipeline wall and the rusted layer in the pipeline based on the pipeline transmission bottom line model, the fluid in the pipeline and the current in the pipeline flowing along the axis direction of the pipeline is as follows:
S＝S f +S C +S r ，
wherein,,
r is the total equivalent longitudinal resistance of the axial unit length;
ρ f is the resistivity of the fluid in the pipeline;
a 1 is the inner radius of the pipeline rust layer;
R c a resistance per unit length of the water supply pipe which is non-rusted along the axial direction;
R r ＝ρ r /[2πa 2 (a 3 -a 2 )]for the resistance per unit length of the rust layer in the water supply pipe in the axial direction, sigma r ＝1/ρ r ；
a 2 Is the radius of the inner wall of a non-rusted pipeline, a 3 Is the radius of the outer wall of the non-rusted pipeline;
σ r is the conductivity of the rust layer of the pipeline.
6. The method of claim 5, wherein the determining the conduit transfer line equation based on the equivalent longitudinal conductance is calculated as:
wherein U is the potential distribution of the wall of the non-rust water supply pipeline;
i is the current in the non-rusting water supply pipe wall;
7. The method of claim 6, wherein calculating the partial derivatives of the electrical potentials of the piped-line formation model to the formation parameters by an electrical potential Jacobi matrix comprises:
performing unit division on the pipeline transmission line stratum model along the pipeline;
determining the Jacobi matrix form based on the unit-divided pipeline transmission line stratum model;
determining the position of the pipeline transmission line stratum model where the measuring electrode is positioned;
and determining partial derivatives of electric potential of the transmission line stratum model to stratum parameters based on the Jacobi matrix form and the position of the pipeline transmission line stratum model where the measuring electrode is positioned.
8. The method of claim 7, wherein the Jacobi matrix is in the form of:
ΔU＝GΔm，
wherein DeltaU is an electric potential increment, deltam is a pipeline transmission line stratum model parameter perturbation increment;
9. The method of claim 8, wherein the pipeline outer rust layer resistance is calculated by inverting an iterative approximation by inverting an objective function using the pipeline transmission line equation and the partial derivative of the potential to formation parameters;
the calculation formula of the inversion objective function is as follows:
F(m)＝||U-U obs ||
wherein U is obs For the measured non-rusting pipe wall potential;
u is the non-rusting pipe wall potential.
10. The method of claim 9, wherein the inversion iteration approximation formula is:
wherein d is k The stratum parameter increment obtained for the kth iteration;
G k T G k a partial derivative matrix product of a pipeline transmission line equation;
i is an n-order identity matrix, beta k Is a positive real constant.
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