CN111398554A - Method and device for determining residual service life of metal pipeline - Google Patents
Method and device for determining residual service life of metal pipeline Download PDFInfo
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Abstract
The invention discloses a method and a device for determining the residual service life of a metal pipeline, and relates to the field of pipeline protection. The method can obtain the pipeline parameters, the discharge factors, the current density of the interference current at each defect on the metal pipeline and the allowable corrosion thickness threshold of the metal pipeline, determine the residual service life of each defect according to the obtained pipeline parameters, the discharge factors, the current density at each defect and the allowable corrosion thickness threshold, and further determine the residual service life of the metal pipeline according to the residual service life of at least one defect. When the method provided by the invention is used for determining the residual service life of the metal pipeline, the pipeline parameters, the discharge factor, the current density of each defect and the allowable corrosion thickness threshold value of the metal pipeline are comprehensively considered, and compared with an empirical determination method in the related art, the method provided by the invention has the advantages that the determined residual service life is higher in precision and higher in determination efficiency.
Description
Technical Field
The invention relates to the field of pipeline protection, in particular to a method and a device for determining the residual service life of a metal pipeline.
Background
Ultra High Voltage (UHV) generally refers to voltages above ± 800 kv. The ultra-high voltage direct current transmission technology is widely applied to the field of power transmission due to the advantages of large capacity, small loss, high stability, lower cost and the like. The extra-high voltage direct current transmission line comprises two grounding electrodes and a positive and negative transmission line. The two grounding electrodes are buried underground, and when the ultrahigh voltage direct current transmission line breaks down, the two grounding electrodes discharge electricity, so that certain interference can be caused to metal pipelines adjacent to the two grounding electrodes, and the service life of the metal pipelines is shortened.
In the related art, the service life of the metal pipeline is usually determined by an empirical determination method, and remedial measures are taken according to the determination result to ensure the normal operation of the metal pipeline. Wherein, the empirical determination means that the service life of the current metal pipeline is estimated according to the service life of the past metal pipeline.
However, the empirical determination method has low determination accuracy.
Disclosure of Invention
The invention provides a method and a device for determining the residual service life of a metal pipeline, which can solve the problem of low determination precision in the related technology. The technical scheme is as follows:
in one aspect, a method for determining the remaining service life of a metal pipe is provided, wherein at least one defect is present on the metal pipe; the method comprises the following steps:
acquiring pipeline parameters of the metal pipeline, wherein the pipeline parameters comprise: the density of the pipe, the relative atomic mass of the pipe, and the valence electrons of the pipe;
obtaining the current density of interference current at each defect on the metal pipeline, wherein the interference current is generated by a grounding electrode of a direct current transmission line;
obtaining an allowable corrosion thickness threshold value of each defect on the metal pipeline;
determining a discharge factor according to the average discharge time of the grounding electrode of the direct current transmission line to the metal pipeline;
for each defect, determining the residual life of each defect according to the pipeline parameters, the discharge factor, the current density of the defect and the allowable corrosion thickness threshold, wherein the residual life of each defect is positively correlated with the density of the pipe, the valence electron of the pipe, the allowable corrosion thickness threshold and the discharge factor, and negatively correlated with the relative atomic mass of the pipe and the current density;
determining the remaining service life of the metal pipe according to the remaining life of the at least one defect.
Optionally, the obtaining a current density of an interference current at each defect on the metal pipe includes:
for each defect, acquiring an upstream current and a downstream current of the defect, wherein the upstream current flows towards the defect, and the downstream current flows away from the defect;
and determining the current density at the defect according to the difference value of the upstream current and the downstream current and the defect area at the defect.
Optionally, two sides of each defect on the metal pipeline are respectively provided with a current loop, and the current loops are connected with a current detector; for each defect, the obtaining the upstream current and the downstream current at the defect comprises:
and acquiring the upstream current and the downstream current of the defect detected by the current detector.
Optionally, the obtaining a permissible corrosion thickness threshold at each defect on the metal pipe includes:
obtaining the residual wall thickness of each defect;
obtaining the minimum wall thickness of each defect for safe operation;
for each defect, determining a difference between the remaining wall thickness at the defect and the minimum wall thickness as an allowable erosion thickness threshold at the defect.
Optionally, the obtaining the minimum wall thickness for safe operation at each defect includes:
acquiring the maximum operating pressure, the outer diameter and the minimum yield strength of the metal pipeline and the strength design coefficient of each defect;
for each defect, determining a minimum wall thickness at the defect based on the maximum operating pressure, the outer diameter, the minimum yield strength, and the design factor for strength at the defect, the minimum wall thickness being positively correlated with the maximum operating pressure and the outer diameter and negatively correlated with the minimum yield strength and the design factor for strength at the defect.
Optionally, the minimum wall thickness C at the first defect of the at least one defectminSatisfies the following conditions: cmin＝(P×D)/(2××e)；
Wherein P is the maximum operating pressure, D is the outer diameter, is the minimum yield strength, and e is a strength design factor at the first defect;
wherein the first defect is any one of the at least one defect.
Optionally, in the at least one defect, the remaining lifetime T at the first defect satisfies:
T＝(ρ×F×n×K×Ccorr)/(M×i)；
wherein rho is the density of the pipe, F is a Faraday constant, n is valence electron of the pipe, K is the discharge factor, CcorrA corrosion allowable thickness threshold at the first defect, M being the relative atomic mass of the pipe, i being the current density at the first defect;
wherein the first defect is any one of the at least one defect.
Optionally, the determining the remaining service life of the metal pipe according to the remaining life of the at least one defect includes:
and determining the shortest residual life of the at least one defect as the residual service life of the metal pipeline.
Optionally, the discharge factor K satisfies K ═ 365 × g/t;
wherein g is a safety factor, g ranges from 2 to 2.5, t is the average discharge time of the direct current transmission line, and t ranges from 6.5 days to 7.5 days.
In another aspect, a device for determining the residual service life of a metal pipeline is provided, wherein the metal pipeline is buried underground, and at least one defect is present on the metal pipeline; the device comprises:
a first obtaining module, configured to obtain a pipe parameter of a metal pipe, where the pipe parameter includes: the density of the pipe, the relative atomic mass of the pipe, and the valence electrons of the pipe;
the second acquisition module is used for acquiring the current density of interference current at each defect on the metal pipeline, wherein the interference current is generated by a direct current transmission line;
the third acquisition module is used for acquiring the allowable corrosion thickness threshold value of each defect on the metal pipeline;
the first determining module is used for determining a discharge factor according to the average discharge time of the direct-current transmission line to the metal pipeline;
a second determining module for determining, for each of the defects, a remaining life of each of the defects according to the pipe parameter, the discharge factor, the current density at the defect, and the allowable corrosion thickness threshold, the remaining life of each of the defects being positively correlated with the density, the valence electron, the allowable corrosion thickness threshold, and the discharge factor, and negatively correlated with the relative atomic mass and the current density;
and the third determining module is used for determining the residual service life of the metal pipeline according to the residual service life of at least one defect.
Optionally, the second obtaining module includes:
the first acquisition submodule is used for acquiring an upstream current and a downstream current of each defect, wherein the upstream current flows towards the defect, and the downstream current flows away from the defect;
and the first determining submodule is used for determining the current density of the defect according to the difference value of the upstream current and the downstream current and the defect area of the defect.
Optionally, two sides of each defect on the metal pipeline are respectively provided with a current loop, and the current loops are connected with a current detector; the first obtaining sub-module is configured to:
and acquiring the upstream current and the downstream current of the defect detected by the current detector.
Optionally, the third obtaining module includes:
the second obtaining submodule is used for obtaining the residual wall thickness of each defect;
the third obtaining submodule is used for obtaining the minimum wall thickness of each defect in safe operation;
a second determination submodule for determining, for each defect, a difference between a remaining wall thickness at the defect and the minimum wall thickness as an allowable corrosion thickness threshold at the defect.
Optionally, the third obtaining sub-module is configured to:
acquiring the maximum operating pressure, the outer diameter and the minimum yield strength of the metal pipeline and the strength design coefficient of each defect;
for each defect, determining a minimum wall thickness at the defect based on the maximum operating pressure, the outer diameter, the minimum yield strength, and the design factor for strength at the defect, the minimum wall thickness being positively correlated with the maximum operating pressure and the outer diameter and negatively correlated with the minimum yield strength and the design factor for strength at the defect.
Optionally, the minimum wall thickness C at the first defect of the at least one defectminSatisfies the following conditions: cmin＝(P×D)/(2××e)；
Wherein P is the maximum operating pressure, D is the outer diameter, is the minimum yield strength, and e is a strength design factor at the first defect;
wherein the first defect is any one of the at least one defect.
Optionally, in the at least one defect, the remaining lifetime T at the first defect satisfies:
T＝(ρ×F×n×K×Ccorr)/(M×i)；
wherein rho is the density of the pipe, F is a Faraday constant, n is valence electron of the pipe, K is the discharge factor, CcorrA corrosion allowable thickness threshold at the first defect, M being the relative atomic mass of the pipe, i being the current density at the first defect;
wherein the first defect is any one of the at least one defect.
Optionally, the third determining module is configured to determine that the remaining life of the at least one defect is shortest as the remaining service life of the metal pipe.
Optionally, the discharge factor K satisfies K ═ 365 × g/t;
wherein g is a safety factor, g ranges from 2 to 2.5, t is the average discharge time of the direct current transmission line, and t ranges from 6.5 days to 7.5 days.
The technical scheme provided by the invention has the beneficial effects that at least:
the invention provides a method and a device for determining the residual service life of a metal pipeline. The method can obtain the pipeline parameters, the discharge factors, the current density of the interference current at each defect on the metal pipeline and the allowable corrosion thickness threshold of the metal pipeline, determine the residual service life of each defect according to the obtained pipeline parameters, the discharge factors, the current density at each defect and the allowable corrosion thickness threshold, and further determine the residual service life of the metal pipeline according to the residual service life of at least one defect. When the method provided by the embodiment of the invention determines the residual service life of the metal pipeline, the pipeline parameters, the discharge factor, the current density at each defect and the allowable corrosion thickness threshold value of the metal pipeline are comprehensively considered, and compared with an empirical determination method in the related art, the method provided by the embodiment of the invention has the advantages that the determined residual service life has higher precision and the determined efficiency is higher.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a flowchart of a method for determining a remaining service life of a metal pipeline according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for obtaining current density according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a metal pipe according to an embodiment of the present invention;
FIG. 4 is a flowchart of a method for obtaining an allowable etch thickness threshold according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a device for determining the remaining service life of a metal pipeline according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a second obtaining module according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a third obtaining module according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
When an extra-high voltage direct current transmission line is arranged around a metal pipeline buried underground, due to the characteristics of large current and intermittence in extra-high voltage direct current transmission, certain interference can be caused to the metal pipeline, the corrosion of the metal pipeline is accelerated, and the service life of the metal pipeline is shortened. Therefore, the method for determining the service life of the metal pipeline provided by the embodiment of the invention can be used for determining the service life of the metal pipeline suffering from the extra-high voltage direct current interference, so that a protection strategy of the interfered metal pipeline is formulated, and the normal operation of the metal pipeline is ensured.
Fig. 1 is a flowchart of a method for determining a remaining service life of a metal pipeline, according to an embodiment of the present invention, where the metal pipeline is buried underground, at least one defect may exist on the metal pipeline, and the at least one defect may be caused by an interference current generated by a ground electrode of a direct current transmission line (for example, an extra-high voltage direct current transmission line). As can be seen with reference to fig. 1, the method may comprise:
The pipeline parameters may include: the density of the pipe, the relative atomic mass of the pipe, and the valence electrons of the pipe. Wherein the relative atomic mass of the pipe may be the relative atomic mass of the elements of the pipe which are most susceptible to corrosion under the influence of the disturbing current. The valence electrons of the pipe can be the valence electrons of elements in the pipe which are most easily corroded under the influence of interference current after corrosion.
By way of example, assuming that the metal pipe is made of X65 steel, the pipe thus obtained may have a density of X65 steel, which may be 7.85g/cm, for example3(g/cc). Since the iron element in the steel is easy to corrode under the extra-high voltage direct current interference, the relative atomic mass of the pipe can be the relative atomic mass of the iron element, namely 56. Since the iron element is usually present in the form of divalent iron ions after corrosion, the valence electron of the pipe may be 2.
And 102, acquiring the current density of the interference current at each defect on the metal pipeline.
The interference current can be generated by a grounding electrode of a direct current transmission line. The current density at each defect may refer to the ratio of the current flowing through the defect to the defect area at the defect.
Fig. 2 is a flowchart of a method for obtaining a current density according to an embodiment of the present invention, and referring to fig. 2, the method may include:
at step 1021, for each defect, an upstream current and a downstream current at the defect are obtained.
Wherein the upstream current may flow in a direction close to the defect, and the downstream current may flow in a direction away from the defect.
Optionally, when the upstream current and the downstream current of each defect are obtained, current loops may be respectively disposed on two sides of each defect on the metal pipe, and the current loops may be connected to the current detector. For each defect, when the grounding electrode of the direct current transmission line discharges, the upstream current and the downstream current detected by the current detectors on the two sides of the defect can be obtained.
For example, when the remaining service life of the metal pipe needs to be detected, a copper sulfate reference electrode may be inserted into the earth's surface first, and the insertion depth may be 5 cm. Then the positive pole of the multimeter is connected with the metal pipeline, and the negative pole is connected with the copper sulfate reference electrode. When the voltage of the metal pipeline is detected to exceed 10V (volt) through the multimeter, the discharge of the grounding electrode of the direct current transmission line can be determined, and at the moment, the upstream current and the downstream current of each defect can be obtained.
Each current loop may include two arc-shaped current loop main bodies, so that the current loop is conveniently sleeved on the metal pipeline.
Referring to fig. 3, a defect position of each defect in the metal pipe may be detected by the current gradient detector, and then the earth surface on both sides of the defect may be excavated according to the detected defect position of the defect, so as to expose the metal pipe. Then, current loops can be respectively arranged on two sides of the defect of the exposed metal pipeline, wherein the current loop on one side is connected with the current detector 01, and the current loop on the other side is connected with the current detector 02. Assuming that the flow direction of the disturbance current in the metal pipe is direction X, the current loop to which the current detector 01 is connected is located upstream of the defect, and the current detector 01 can be used to detect the upstream current at the defect. The current loop to which the current detector 02 is connected is located downstream of the defect where the current detector 02 can be used to detect the downstream current.
Assuming that the overall length of the metal pipeline is 400km (kilometers), a plurality of insulating flanges are arranged on the metal pipeline at intervals, the metal pipeline can be divided into a plurality of regions through the plurality of insulating flanges, and the lengths of the plurality of regions can be the same or different. Suppose that one of the regions is 10km long (the regions are provided with insulating flanges at both ends), and that the region is subject to extra-high voltage dc interference. And N is 10 defects (N is a positive integer) exist on the region, the upstream current and the downstream current of each defect can be obtained by adopting the method.
Wherein, the defect area of the defect position can be detected by adopting equipment such as a Pipeline Current Mapper (PCM) and the like through an alternating current potential gradient method. For a first defect of the at least one defect, the current density I at the first defect, determined from the difference between the upstream current and the downstream current, and the defect area, may satisfy:
I＝(Iu-Id) formula/S (1)
Wherein, IuIs the upstream current at the first defect, IdIs the downstream current at the first defect and S is the defect area at the first defect. The first defect may be any one of the at least one defect.
For example, assume that there are 10 defects on a metal pipe, and the defect areas S of the 10 defects detected by the ac potential gradient method are: 1.5cm2(square centimeter) and 10cm2、3.5cm2、2.2cm2、1.7cm2、6.5cm2、4.5cm2、1cm2、0.8cm2、5.5cm2. The difference between the upstream current and the downstream current at each of the 10 defects is: 0.009A (Ampere), 0.05A, 0.0098A, 0.02002A, 0.01989A, 0.00975A, 0.04005A, 0.0089A, 0.024A, 0.0297A. Then, according to the above formula (1), the current densities I at the 10 defects are determined as follows: 0.006A/cm2(ampere/square centimeter) 0.005A/cm2、0.0028A/cm2、0.0091A/cm2、0.0117A/cm2、0.0015A/cm2、0.0089A/cm2、0.03A/cm2、0.025A/cm2、0.0054A/cm2。
And 103, acquiring an allowable corrosion thickness threshold value of each defect on the metal pipeline.
In an embodiment of the invention, the allowable corrosion thickness threshold at each defect is the difference between the remaining wall thickness at the defect and the minimum wall thickness at the defect for safe operation.
Because the shapes, sizes and corrosion thicknesses of the defects on the metal pipeline to be corroded are different, the allowable corrosion thickness threshold value of each defect is different. Assuming that the thickness etched at a defect is small, the allowable etch thickness threshold at that defect is large. Given the greater thickness of the etch at a defect, the threshold allowable etch thickness at that defect is less.
Fig. 4 is a flowchart of a method for obtaining an allowable corrosion thickness threshold according to an embodiment of the present invention, and referring to fig. 4, the method may include:
and step 1031, obtaining the residual wall thickness of each defect.
The remaining wall thickness at each defect can be detected by an in-pipe detector. The in-pipe detector may be placed inside a metal pipe, and the in-pipe detector may crawl inside the metal pipe to detect the remaining wall thickness at each defect on the metal pipe.
For example, assume that there are 10 defects on a metal pipe and the remaining wall thickness C at the 10 defects is detected by an in-pipe detectornowRespectively as follows: 1.24cm (centimeter), 1.27cm, 1.26cm, 1.25cm, 1.29cm, 1.2cm, 1.22cm, 1.21cm, 1.28 cm.
And step 1032, acquiring the minimum wall thickness of each defect for safe operation.
In order to ensure the safe operation of the metal pipeline, the wall thickness of the metal pipeline is greater than or equal to the minimum wall thickness. This minimum wall thickness can be obtained by:
step 10321, obtain a maximum operating pressure, an outside diameter, a minimum yield strength, and a design factor of strength at each defect for the metal pipe.
The maximum operating pressure, the outer diameter and the minimum yield strength of the metal pipe can be obtained from the design data of the metal pipe. The strength design factor of the metal pipeline can be determined according to the regional grade of the metal pipeline. The district level may be divided according to the density of buildings in the district grading unit, and the district level may include four levels from a first-class district to a fourth-class district. Wherein, the first-level area means: an area with 12 or less than 12 individual buildings in which people live. The second level area is: there are more than 12, and less than 80 independent buildings where people live. The third-level area is as follows: areas, industrial areas or areas where pipelines are laid within 90m from outdoor sites where people gather, where there are 80 or more than 80 individual buildings for human residence but there are not four levels of area conditions. The fourth-level area is: urban central areas with high traffic or underground utilities.
According to the national standard GB50251, the intensity design coefficient of a first-level area is 0.72, the intensity design coefficient of a second-level area is 0.6, the intensity design coefficient of a third-level area is 0.5, and the intensity design coefficient of a fourth-level area is 0.4. When a defect of the metal pipeline is located in the first-level region, the strength design coefficient of the defect is 0.72. When a certain defect of the metal pipeline is positioned in a third-level area, the strength design coefficient of the defect is 0.5.
For each defect, a minimum wall thickness at the defect is determined based on the maximum operating pressure, the outer diameter, the minimum yield strength, and the strength design factor at the defect, step 10322.
Wherein a minimum wall thickness C at the first defect of the at least one defectminPositively correlated with the maximum operating pressure P and the outside diameter D, with the minimum yield strength and the firstThe intensity design factor e at a defect is inversely related. The first defect is any defect of the at least one defect. Illustratively, the minimum wall thickness C at the first defectminCan satisfy the following conditions:
Cmin(P × D)/(2 ×× e) formula (2)
Where P is the maximum operating pressure, D is the outside diameter, is the minimum yield strength, and e is the strength design factor at the first defect.
For the same metal pipe, the maximum operating pressure P, the outside diameter D and the minimum yield strength are the same everywhere, while the design factor of strength e varies depending on the area where the defect is located. Therefore, among at least one defect on the same metal pipe, the minimum wall thickness C of each defect in the same areaminSame, minimum wall thickness C at each defect in different regionsminWill vary depending on the intensity design factor e.
For example, assuming that a metal pipe is made of X65 steel, the maximum operating pressure P of the metal pipe is 9.5MPa (megapascal), the outer diameter D of the metal pipe is 457mm (millimeter), the minimum yield strength of the pipe is 450MPa, 10 defects are present on the metal pipe, and the first four defects of the 10 defects are located in a first level area, and the last six defects are located in a second level area. The design factor of intensity e at the first four defects is 0.72 and the design factor of intensity e at the last six defects is 0.6. The minimum wall thickness C of the first four defects of the 10 defects can be calculated by equation (2)minAll 0.67cm, minimum wall thickness C at the last six defectsminAre all 0.80 cm.
As can be seen from the above steps, the allowable etching thickness threshold CcorrCan satisfy the following conditions:
Ccorr＝Cnow-Cmin＝Cnow- (P × D)/(2 ×× e) formula (3)
For example, assume that there are 10 defects on a metal pipe, andresidual wall thickness C at the 10 defectsnowRespectively as follows: 1.24cm, 1.27cm, 1.26cm, 1.25cm, 1.29cm, 1.2cm, 1.22cm, 1.21cm, 1.28 cm. Minimum wall thickness C at the first four defectsmin0.67cm, minimum wall thickness C at the last six defectsminIs 0.80 cm. The allowable etch thickness threshold C for each of the 10 defects may be determined according to equation (3)corrRespectively as follows: 0.57cm, 0.60cm, 0.59cm, 0.45cm, 0.49cm, 0.40cm, 0.42cm, 0.41cm, and 0.48 cm.
And 104, determining a discharge factor according to the average discharge time of the direct-current transmission line to the metal pipeline.
In the embodiment of the invention, the discharge factor K can satisfy:
k ═ 365 × g/t equation (4)
Wherein 365 may refer to days included per year, g is a safety factor, g may range from 2 to 2.5, t is an average discharge time of the dc transmission line, and t may range from 6.5 days to 7.5 days. The average discharge time may refer to an average discharge time accumulated per year for a ground electrode of the dc transmission line.
For example, assuming that the safety factor g is 2 and the average discharge time t of the dc transmission line is 7.5 days, the discharge factor K is obtained according to the formula (4): k730/7.5 97.33.
And step 105, determining the residual life of each defect according to the pipeline parameters, the discharge factor, the current density of the defect and the allowable corrosion thickness threshold value for each defect.
In an embodiment of the invention, the remaining lifetime at each defect is positively correlated with the density of the pipe, the valence electron of the pipe, the allowable corrosion thickness threshold at the first defect, and the discharge factor, and negatively correlated with the relative atomic mass of the pipe and the current density at the defect.
For example, the remaining lifetime T at the first defect of the at least one defect may satisfy:
T＝(ρ×F×n×K×Ccorr) /(M × i) formula (5)
Wherein rho is the density of the pipe, F is FaradayConstant, n is valence electron of the tube, K is discharge factor, CcorrIs the allowable corrosion thickness threshold at the first defect, M is the relative atomic mass of the pipe, and i is the current density at the first defect.
Optionally, for convenience of statistics, when the remaining life T1 of the first defect is calculated according to the obtained data, rounding may be performed on the calculation result, that is, the remaining life T of the first defect may satisfy:
T＝INT[(ρ×F×n×K×Ccorr)/(M×i)]formula (6)
And, in order to ensure the normal operation of the metal pipe, the value may be rounded down. For example, assuming that the remaining life T of the first defect is calculated to be 4.6 years by formula (5), the remaining life T of the first defect can be determined to be 4 years by rounding down the remaining life T.
As an example, assume that the density ρ of the metal pipe tubing is 7.85g/cm3The Faraday constant F is 9.65 × 104C/mol (charge/mol), 10 defects exist on the metal pipeline, and the discharge factor of the 10 defects, the current density of each defect and the allowable corrosion thickness threshold of each defect are as shown in the above steps 101 to 104, then the residual life T of each defect of the 10 defects is obtained according to the formula (6)1To T10Respectively for 7 years, 10 years, 17 years, 5 years, 3 years, 26 years, 3 years, 1 year and 7 years.
And 106, determining the residual service life of the metal pipeline according to the residual service life of the at least one defect.
In the embodiment of the invention, the shortest residual life in the residual life of the at least one defect can be determined as the residual service life of the metal pipeline. That is, the remaining service life T of the metal pipe0Can satisfy the following conditions:
wherein N is the number of the defects on the metal pipeline, TxIs the remaining lifetime at the xth defect of the N defects, and x is a positive integer no greater than N. min means taking T1To TNMinimum value of (1).
By way of example, assume that there are 10 defects on the metal pipe and that the remaining life T at each of the 10 defects1To T10Respectively for 7 years, 10 years, 17 years, 5 years, 3 years, 26 years, 3 years, 1 year and 7 years. The remaining service life T of the metal pipe can be found to be 1 year according to equation (7).
Furthermore, according to the determination result, corresponding remedial measures can be taken for the defect with short residual life, so that the normal operation of the metal pipeline is ensured.
In the embodiment of the invention, the metal pipeline is prepared by wrapping a layer of anticorrosive coating on the outer side of the metal pipeline body. Because the detection cost to the metal pipeline body is higher, so in order to save cost, the detection to the anticorrosive coating is once every two years usually, and the detection to the metal pipeline body is once every five years. The detection result of the anticorrosive coating can be obtained by an alternating current potential gradient method, and generally comprises the following steps: number of defects, defect location, and defect area. The detection result of the metal pipe body can be obtained by detecting a detector in the pipe, and generally comprises: the remaining wall thickness at each defect. The method for determining the residual service life of the metal pipeline provided by the embodiment of the invention can determine the residual service life of the metal pipeline by adopting the detection result of the anticorrosive layer and the detection result of the metal pipeline body. The anticorrosive coating is detected once every two years, and the metal pipeline body is detected once every five years, so that when the method for determining the metal pipeline provided by the embodiment of the invention is used for determining the residual service life, the detection result of the anticorrosive coating and the detection result of the metal pipeline body at the last time can be used for determining, and the detection cost is saved.
It should be noted that, the order of the steps of the method for determining the remaining service life of the metal pipeline provided in the embodiment of the present invention may be appropriately adjusted, for example, the execution order of the steps 101 to 104 may be adjusted according to the situation, for example, the step 104 may be executed before the step 103, and the steps 101 to 104 may also be executed simultaneously. Any method that can be easily conceived by those skilled in the art within the technical scope of the present disclosure is covered by the protection scope of the present disclosure, and thus, the detailed description thereof is omitted.
In summary, the embodiments of the present invention provide a method for determining a remaining service life of a metal pipe, where the method may obtain pipe parameters, a discharge factor, a current density of an interference current at each defect on the metal pipe, and a corrosion allowable thickness threshold of the metal pipe, determine the remaining service life of each defect according to the obtained pipe parameters, discharge factors, current densities at each defect, and corrosion allowable thickness thresholds, and further determine the remaining service life of the metal pipe according to the remaining service life of at least one defect. When the method provided by the embodiment of the invention determines the residual service life of the metal pipeline, the pipeline parameters, the discharge factor, the current density at each defect and the allowable corrosion thickness threshold value of the metal pipeline are comprehensively considered, and compared with an empirical determination method in the related art, the method provided by the embodiment of the invention has the advantages that the determined residual service life has higher precision and the determined efficiency is higher.
The method for determining the residual service life of the metal pipeline provided by the embodiment of the invention can be used for determining the residual service life of the metal pipeline and determining the residual service life of each defect in the metal pipeline, and comprehensively considers two factors of corrosion and hoop stress when determining the residual service life of each defect and determining the residual service life of the metal pipeline, so that the determination precision is high. The residual service life determined by the method provided by the embodiment of the invention can be used for making a protection strategy of the interfered metal pipeline, so that the blindness of protecting the metal pipeline is avoided, and the safe operation of the metal pipeline is ensured.
Fig. 5 is a schematic structural diagram of an apparatus for determining a remaining service life of a metal pipeline, which may be buried in the ground and may have at least one defect, according to an embodiment of the present invention. As can be seen with reference to fig. 5, the apparatus may comprise:
a first obtaining module 501, configured to obtain a pipe parameter of a metal pipe, where the pipe parameter includes: the density of the pipe, the relative atomic mass of the pipe, and the valence electrons of the pipe.
A second obtaining module 502, configured to obtain a current density of an interference current at each defect on the metal pipe, where the interference current is generated by a ground electrode of the dc transmission line.
And a third obtaining module 503, configured to obtain a corrosion allowable thickness threshold at each defect on the metal pipe.
The first determining module 504 is configured to determine a discharge factor according to an average discharge time of the ground electrode of the dc transmission line to the metal pipe.
And a second determining module 505, configured to determine, for each defect, a remaining life of each defect according to the pipe parameter, the discharge factor, the current density at the defect, and the allowable corrosion thickness threshold, where the remaining life of each defect is positively correlated with the density, the valence electron, the allowable corrosion thickness threshold, and the discharge factor, and negatively correlated with the relative atomic mass and the current density.
A third determining module 506, configured to determine a remaining service life of the metal pipe according to the remaining life of the at least one defect.
In summary, the present invention provides an apparatus for determining a remaining service life of a metal pipe, in which a first obtaining module, a second obtaining module, and a third obtaining module are used to obtain a pipe parameter, a current density, and an allowable corrosion thickness threshold of the metal pipe. The discharge factor is determined by a first determination module, and the remaining life of the defect in the metal pipe and the remaining service life of the metal pipe are determined by a second determination module and a third determination module, respectively. The device provided by the embodiment of the invention can determine the residual service life of the metal pipeline, can also determine the residual service life of each defect in the metal pipeline, and has higher determination precision. In addition, the residual service life determined by the device provided by the embodiment of the invention can be used for making a protection strategy of the disturbed metal pipeline, so that the safe operation of the metal pipeline is ensured.
Fig. 6 is a schematic structural diagram of a second obtaining module according to an embodiment of the present invention. Referring to fig. 6, the second obtaining module 502 includes:
the first obtaining submodule 5021 is used for obtaining, for each defect, an upstream current and a downstream current at the defect, wherein the upstream current flows in a direction close to the defect, and the downstream current flows in a direction far away from the defect.
The first determining sub-module 5022 is used for determining the current density at the defect according to the difference between the upstream current and the downstream current and the defect area at the defect.
Optionally, two sides of each defect on the metal pipeline are respectively provided with a current loop, and the current loops are connected with a current detector; the first acquisition submodule 5021 may be configured to:
and acquiring the upstream current and the downstream current of the defect detected by the current detector.
Fig. 7 is a schematic structural diagram of a third obtaining module according to an embodiment of the present invention. Referring to fig. 7, the third obtaining module 503 may include:
a second obtaining sub-module 5031 for obtaining the remaining wall thickness at each defect.
A third obtaining sub-module 5032 for obtaining a minimum wall thickness for safe operation at each defect.
A second determining sub-module 5033 for determining, for each defect, the difference between the remaining wall thickness and the minimum wall thickness at the defect as the allowable corrosion thickness threshold at the defect.
Optionally, the third obtaining sub-module 5032 may be configured to:
and acquiring the maximum operating pressure, the outer diameter, the minimum yield strength and the strength design coefficient of each defect of the metal pipeline.
For each defect, determining a minimum wall thickness at the defect based on the maximum operating pressure, the outer diameter, the minimum yield strength, and the design factor for the strength at the defect, the minimum wall thickness being positively correlated with the maximum operating pressure and the outer diameter and negatively correlated with the minimum yield strength and the design factor for the strength at the defect.
Optionally, the minimum wall thickness C at the first defect of the at least one defectminSatisfies the following conditions: cmin＝(P×D)/(2××e)。
Where P is the maximum operating pressure, D is the outside diameter, is the minimum yield strength, and e is the strength design factor at the first defect.
Wherein the first defect is any one of the at least one defect.
Optionally, in the at least one defect, the remaining lifetime T at the first defect satisfies:
T＝(ρ×F×n×K×Ccorr)/(M×i)。
wherein rho is the density of the pipe, F is the Faraday constant, n is the valence electron of the pipe, K is the discharge factor, CcorrIs the allowable corrosion thickness threshold at the first defect, M is the relative atomic mass of the pipe, and i is the current density at the first defect.
Wherein the first defect is any one of the at least one defect.
Optionally, the third determining module 506 is configured to determine that the remaining life of the at least one defect is the shortest remaining service life of the metal pipe.
Optionally, the discharge factor K satisfies K ═ 365 × g/t.
Wherein 365 may mean days per year, g is a safety factor, g may range from 2 to 2.5, t is an average discharge time of the dc transmission line, and t may range from 6.5 days to 7.5 days.
In summary, the device for determining the remaining service life of the metal pipeline provided by the embodiment of the present invention may be used to determine not only the remaining service life of the metal pipeline, but also the remaining service life of each defect in the metal pipeline, and when determining the remaining service life of each defect and determining the remaining service life of the metal pipeline, two factors of corrosion and hoop stress are taken into consideration, so that the determination accuracy is high. The residual service life determined by the device provided by the embodiment of the invention can be used for making a protection strategy of the interfered metal pipeline, so that the blindness of protecting the metal pipeline is avoided, and the safe operation of the metal pipeline is ensured.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described apparatuses, modules and sub-modules may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The invention is not to be considered as limited to the particular embodiments shown and described, but is to be understood that various modifications, equivalents, improvements and the like can be made without departing from the spirit and scope of the invention.
Claims (10)
1. The method for determining the residual service life of the metal pipeline is characterized in that the metal pipeline is buried underground, and at least one defect is formed on the metal pipeline; the method comprises the following steps:
acquiring pipeline parameters of the metal pipeline, wherein the pipeline parameters comprise: the density of the pipe, the relative atomic mass of the pipe, and the valence electrons of the pipe;
obtaining the current density of interference current at each defect on the metal pipeline, wherein the interference current is generated by a grounding electrode of a direct current transmission line;
obtaining an allowable corrosion thickness threshold value of each defect on the metal pipeline;
determining a discharge factor according to the average discharge time of the grounding electrode of the direct current transmission line to the metal pipeline;
for each defect, determining the residual life of each defect according to the pipeline parameters, the discharge factor, the current density of the defect and the allowable corrosion thickness threshold, wherein the residual life of each defect is positively correlated with the density of the pipe, the valence electron of the pipe, the allowable corrosion thickness threshold and the discharge factor, and negatively correlated with the relative atomic mass of the pipe and the current density;
determining the remaining service life of the metal pipe according to the remaining life of the at least one defect.
2. The method of claim 1, wherein said obtaining a current density of a disturbance current at each defect on the metal pipe comprises:
for each defect, acquiring an upstream current and a downstream current of the defect, wherein the upstream current flows towards the defect, and the downstream current flows away from the defect;
and determining the current density at the defect according to the difference value of the upstream current and the downstream current and the defect area at the defect.
3. The method according to claim 2, wherein a current loop is respectively arranged on two sides of each defect on the metal pipeline, and the current loop is connected with a current detector; for each defect, the obtaining the upstream current and the downstream current at the defect comprises:
and acquiring the upstream current and the downstream current of the defect detected by the current detector.
4. The method of claim 1, wherein said obtaining a threshold allowable corrosion thickness at each defect on the metal pipe comprises:
obtaining the residual wall thickness of each defect;
obtaining the minimum wall thickness of each defect for safe operation;
for each defect, determining a difference between the remaining wall thickness at the defect and the minimum wall thickness as an allowable erosion thickness threshold at the defect.
5. The method of claim 4, wherein said obtaining a minimum wall thickness for safe operation at each defect comprises:
acquiring the maximum operating pressure, the outer diameter and the minimum yield strength of the metal pipeline and the strength design coefficient of each defect;
for each defect, determining a minimum wall thickness at the defect based on the maximum operating pressure, the outer diameter, the minimum yield strength, and the design factor for strength at the defect, the minimum wall thickness being positively correlated with the maximum operating pressure and the outer diameter and negatively correlated with the minimum yield strength and the design factor for strength at the defect.
6. Method according to claim 5, wherein of said at least one defect a minimum wall thickness C at a first defectminSatisfies the following conditions: cmin＝(P×D)/(2××e)；
Wherein P is the maximum operating pressure, D is the outer diameter, is the minimum yield strength, and e is a strength design factor at the first defect;
wherein the first defect is any one of the at least one defect.
7. The method according to any one of claims 1 to 6, wherein, among the at least one defect, the residual life T at the first defect satisfies:
T＝(ρ×F×n×K×Ccorr)/(M×i)；
wherein rho is the density of the pipe, F is a Faraday constant, n is valence electron of the pipe, K is the discharge factor, CcorrA corrosion allowable thickness threshold at the first defect, M being the relative atomic mass of the pipe, i being the current density at the first defect;
wherein the first defect is any one of the at least one defect.
8. The method of any one of claims 1 to 6, wherein determining the remaining useful life of the metal pipe from the remaining life of the at least one defect comprises:
and determining the shortest residual life of the at least one defect as the residual service life of the metal pipeline.
9. The method according to any one of claims 1 to 6,
the discharge factor K satisfies that K is (365 × g)/t;
wherein g is a safety factor, g ranges from 2 to 2.5, t is the average discharge time of the direct current transmission line, and t ranges from 6.5 days to 7.5 days.
10. The device for determining the residual service life of the metal pipeline is characterized in that the metal pipeline is buried underground, and at least one defect is formed on the metal pipeline; the device comprises:
a first obtaining module, configured to obtain a pipe parameter of a metal pipe, where the pipe parameter includes: the density of the pipe, the relative atomic mass of the pipe, and the valence electrons of the pipe;
the second acquisition module is used for acquiring the current density of interference current at each defect on the metal pipeline, wherein the interference current is generated by a direct current transmission line;
the third acquisition module is used for acquiring the allowable corrosion thickness threshold value of each defect on the metal pipeline;
the first determining module is used for determining a discharge factor according to the average discharge time of the direct-current transmission line to the metal pipeline;
a second determining module for determining, for each of the defects, a remaining life of each of the defects according to the pipe parameter, the discharge factor, the current density at the defect, and the allowable corrosion thickness threshold, the remaining life of each of the defects being positively correlated with the density, the valence electron, the allowable corrosion thickness threshold, and the discharge factor, and negatively correlated with the relative atomic mass and the current density;
and the third determining module is used for determining the residual service life of the metal pipeline according to the residual service life of at least one defect.
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