Interference corrosion test device of direct current stray current to pipeline
Technical Field
The invention relates to the field of petrochemical industry, in particular to a device for testing interference corrosion of direct-current stray current on a pipeline.
Background
With the large-scale construction of high-voltage/extra-high-voltage transmission lines and electrified railway systems, the interference of stray current to buried pipelines and the corrosion and safety problems of the pipelines caused by the interference are increasingly prominent.
The insulating nature of anticorrosive coating of buried pipeline is better, and the stray current who gets into the pipeline from soil can follow the anticorrosive coating of pipeline damage, peel off defect such as the outflow after the transmission of certain distance, and at this moment, will cause the corruption in the part of the outflow position of electric current. The corrosion caused by the stray current belongs to electrochemical corrosion, and the corrosion causes great loss of production materials (such as oil and gas pipelines) and also can cause production loss; therefore, a certain basis can be provided for evaluating the influence and harm of the stray current on the pipeline by carrying out the interference corrosion test on the pipeline.
In the prior art, the technical scheme related to the pipeline corrosion test under the direct current interference comprises the following steps: the patent of carrying out direct current stray current through simulating actual industrial environment and testing the corrosion rate of metal materials: "an experimental apparatus (application No. 2013102425139) for simulating stray current corrosion in soil"; patent simulating the effect of stress and stray current coupling on the peeling of pipe coatings: "a buried steel pipeline coating stripping and corrosion test system under the coupling effect of stress and stray current (application number: 2013103001961)"; the patent for realizing the test of the electrochemical corrosion behavior of the pipeline steel under the interference of the direct-current stray current comprises the following steps: "electrochemical test system for evaluating corrosion of oil and gas pipelines under interference of direct current stray current (application number: 2014206230939)".
The inventor finds that at least the following defects exist in the prior art through research:
the experimental method obtained in the prior art cannot obtain comprehensive data of the influence of stray current on the stripped coating of the pipeline.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide a device for testing the interference corrosion of a pipeline by direct current stray current, so that the corrosion condition of the pipeline under the direct current interference can be measured, and the change of a microenvironment in a gap can be monitored in real time.
In order to achieve the aim, the invention provides a device for testing the interference corrosion of a pipeline by direct-current stray current, which comprises an environment simulation unit and a circuit unit;
the shell of the environment simulation unit comprises a bottom plate and a cover plate; pipeline steel in contact connection with the bottom plate and an insulating layer in contact connection with the cover plate are arranged in a cavity formed by the shell; a gasket is arranged between the pipeline steel and the insulating layer, so that a spacing gap with a preset distance is kept between the pipeline steel and the insulating layer; the cavity formed by the shell further comprises a solution area, and the insulating layer is provided with a through hole so as to communicate the solution area with the interval gap; the environment simulation unit also comprises a stress applying component for applying stress to the pipeline steel and a stress acquisition component for acquiring stress data borne by the pipeline steel;
the circuit unit comprises an interference simulation sub-circuit and a measurement sub-circuit; the interference simulation sub-circuit for generating the direct current stray current comprises a direct current power supply and an auxiliary electrode; the auxiliary electrode is arranged in the solution area and is connected with the direct current power supply circuit; the measuring sub-circuit for acquiring experimental data comprises a reference electrode, a voltmeter and a micro-electrode group which are connected in series; the reference electrode is arranged at the through hole; the microelectrode group comprises a plurality of potential microelectrodes and is used for acquiring experimental data in the gap through a plurality of microelectrode jacks arranged on the cover plate and the insulating layer, and the microelectrode jacks are respectively arranged at positions with different distances from the through hole; the voltmeter is used for respectively acquiring potential difference data between the plurality of potential microelectrodes and the reference electrode.
Further, in the above technical solution, the stress applying part includes a fixing frame provided with a fixing plate; the fixing frame is arranged below the shell, and the pipeline steel extending out of the shell penetrates through the through hole in the fixing plate; and a loading bolt for stretching the pipeline steel is arranged at one end of the pipeline steel, which passes through the through hole.
Further, in the above technical scheme, the insulating layer includes organic glass.
Further, in the above technical scheme, the microelectrode unit further comprises a pH microelectrode and/or a chloride ion concentration microelectrode.
Further, in the above technical scheme, the thickness of the gasket is adjustable.
Further, in the above technical solution, the number of the microelectrode insertion holes is three.
Further, in the above technical scheme, the distances between the plurality of microelectrode insertion holes are equal.
Further, in the technical scheme, the PH value microelectrode comprises a CF/WO-PH microelectrode prepared by a sol-gel method; the chloride ion concentration microelectrode comprises an Ag/AgCl microelectrode prepared by a silver wire electrochemical method; the potential microelectrode includes a potential microelectrode prepared by platinum wire type redox.
Further, in the above technical scheme, the gasket is made of PTFE.
Further, in the above technical solution, the reference electrode includes a saturated calomel electrode SCE.
Advantageous effects
According to the interference corrosion test device for the pipeline by the direct-current stray current, the state of the pipeline after an insulating coating is stripped and damaged is simulated by a mode of constructing a gap between an insulating layer and pipeline steel by arranging a gasket, and different stress conditions of the pipeline steel are simulated by a stress applying component; then, an interference simulation sub-circuit is arranged to simulate the interference environment of the direct-current stray current on the pipeline after the insulating coating is stripped; in addition, in the invention, a plurality of microelectrode insertion holes penetrating into the interval gaps are also arranged on the cover plate and the insulating layer; through the measuring sub-circuit, experimental data such as potential difference, pH value, chloride ion concentration and the like between the through hole on the insulating layer and each microelectrode can be respectively obtained.
Because the distance between each microelectrode and the through hole at the simulated damage position is different, the invention can obtain experimental data of different positions of the insulating layer, thereby simulating the influence degree and the influence mode of the microelectrode on different positions in the gap for peeling the insulating layer of the pipeline after the microelectrode is interfered by direct current stray current. That is to say, the invention can monitor the local environment and the tube body corrosion electrochemical behavior of different positions under the direct current interference pipeline steel stripping coating in real time, thereby providing richer and more effective experimental data for researching the effect of parameters such as cathodic protection, external soil environment, direct current interference, strength, frequency, size of damaged points and the like on the pipeline steel corrosion behavior under the stripping coating.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood and to make the technical means implementable in accordance with the contents of the description, and to make the above and other objects, technical features, and advantages of the present invention more comprehensible, one or more preferred embodiments are described below in detail with reference to the accompanying drawings.
Drawings
FIG. 1 is a schematic structural diagram of a device for testing the interference corrosion of a pipeline by direct stray current according to the present invention.
Detailed Description
The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.
Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.
Spatially relative terms, such as "below," "lower," "upper," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the object in use or operation in addition to the orientation depicted in the figures. For example, if the items in the figures are turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the elements or features. Thus, the exemplary term "below" can encompass both an orientation of below and above. The article may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative terms used herein should be interpreted accordingly.
In this document, the terms "first", "second", etc. are used to distinguish two different elements or portions, and are not used to define a particular position or relative relationship. In other words, the terms "first," "second," and the like may also be interchanged with one another in some embodiments.
As shown in fig. 1, according to an embodiment of the present invention, an apparatus for testing interference and corrosion of a pipeline by a dc stray current includes an environmental simulation unit and a circuit unit;
the shell of the environment simulation unit comprises a bottom plate 01 and a cover plate 02; pipeline steel 03 in contact connection with the bottom plate 01 and an insulating layer 04 in contact connection with the cover plate 02 are arranged in a cavity formed by the shell; a gasket 05 is arranged between the pipeline steel 03 and the insulating layer 04 so as to keep a spacing gap 06 with a preset distance between the pipeline steel 03 and the insulating layer 04; the cavity formed by the shell further comprises a solution area 07, and the insulating layer 04 is provided with a through hole 08 to communicate the solution area 07 with the spacing gap 06; the environment simulation unit also comprises a stress applying component for applying stress to the pipeline steel 03 and a stress acquisition component for acquiring stress data borne by the pipeline steel 03;
the circuit unit comprises an interference simulation sub-circuit and a measurement sub-circuit; the interference simulation sub-circuit for generating the direct current stray current comprises a direct current power supply 09 and an auxiliary electrode 10; the auxiliary electrode 10 is arranged in the solution area 07 and is connected with a direct current power supply 09 in a circuit manner; the measuring sub-circuit for acquiring experimental data comprises a reference electrode 11, a voltmeter 12 and a micro-electrode group 13 which are connected in series; the reference electrode 11 is arranged at the through hole 08; the microelectrode group 13 comprises a plurality of potential microelectrodes and is used for acquiring experimental data in the spacing gap 06 through a plurality of microelectrode jacks arranged on the cover plate 02 and the insulating layer 04, and the microelectrode jacks are respectively arranged at positions with different distances from the through hole 08; the voltmeter 12 is used for respectively acquiring potential difference data between the plurality of potential microelectrodes and the reference.
In the embodiment of the invention, the environment simulation unit is a part for simulating the state after the insulating coating of the pipeline is stripped and damaged, and the shell of the environment simulation unit is composed of a bottom plate 01 and a cover plate 02, so that a cavity is formed; the cavity comprises two parts, wherein one part is used for arranging pipeline steel 03, a gasket 05 and an insulating layer 04; the other part is used for forming a solution area 07; in addition, a stress applying component is arranged below the shell; in practical applications, the stress applying component may include a fixing frame, and the fixing frame is composed of a base 21 and a fixing plate 22; thus, after the pipeline steel 03 extending out of the shell passes through the through hole in the fixing plate 22, stress can be applied to the pipeline steel 03 by rotating the carrier bolt 23 in a manner of stretching the pipeline steel 03; in addition, in order to acquire the stress data of the stress applied to the pipeline steel 03 in real time, a stress acquisition component 24 is also arranged; in particular, the stress-gathering component may be a load cell; thus, by acquiring the collected data of the sensor, the stress data of the pipeline steel 03 can be measured.
The pipeline steel 03 in the embodiment of the invention is used for simulating the pipe wall of an oil-gas pipeline, and the insulating layer 04 is used for simulating an insulating coating of the pipeline; the gasket 05 is arranged between the pipeline steel 03 and the insulating layer 04 to keep a spacing gap 06 with a preset distance between the pipeline steel 03 and the insulating layer 04, so that a gap formed between the stripped pipeline insulating coating and the pipe wall of the oil and gas pipeline is simulated; in practical applications, the gasket 05 in the embodiment of the present invention may be made of PTFE; the solution area 07 simulates different environments of the oil and gas pipeline in the existing place through the composition of different solutions, and in addition, the insulating layer 04 is also provided with a through hole 08 to simulate the damaged position of the pipeline after the insulating coating is stripped.
The circuit unit in the embodiment of the invention can simulate the direct current stray current on the oil-gas pipeline through the interference simulation sub-circuit on one hand, and can also obtain experimental data through the measurement sub-circuit on the other hand; the interference simulation sub-circuit can generate direct current stray current through the direct current power supply 09 and the auxiliary electrode 10 can generate direct current stray current in the solution area 07, and the direct current stray current can be transmitted to the gap 06 through the through hole 08;
the reference electrode 11, the voltmeter 12 and the micro-electrode group 13 of the measuring sub-circuit are connected in series and used for measuring potential data from the through hole 08 to each micro-electrode in the micro-electrode group 13; the microelectrode unit 13 in the embodiment of the present invention may include a plurality of potential microelectrodes (for example, 3 microelectrodes) respectively disposed at different distances from the through hole 08, so as to simulate different positions of the pipeline stripping coating, that is, by respectively obtaining potential data of different microelectrodes, real-time monitoring of local environments at different positions and electrochemical behaviors of corrosion of the pipe body under the pipeline steel stripping coating interfered by the direct current can be achieved. Wherein, the reference electrode 11 may include a Saturated Calomel Electrode (SCE);
in practical application, the insulating layer in the embodiment of the invention can be organic glass; in order to obtain experimental data such as a pH value and a chloride ion concentration in the gap 06, the microelectrodes in the microelectrode group 13 in the embodiment of the present invention may further include a plurality of microelectrodes such as a pH value microelectrode and a chloride ion concentration microelectrode; specifically, the pH microelectrode can be a CF/WO-pH microelectrode prepared by a sol-gel method; the chloride ion concentration microelectrode can be an Ag/AgCl microelectrode prepared by a silver wire electrochemical method; the potential microelectrode may be a potential microelectrode prepared by platinum wire type redox.
Furthermore, in order to calculate and determine the variation trend of the influence degree of the local environment at different positions under the steel stripping coating of the direct current interference pipeline and the corrosion electrochemical behavior of the pipe body, the distances among the microelectrode insertion holes in the embodiment of the invention can also be set to be equal.
In summary, in the embodiment of the present invention, the spacers are provided to form the gaps between the insulating layer and the pipeline steel, so as to simulate the state of the pipeline insulating coating after peeling and breaking, and simulate the pipeline steel receiving different stress conditions by the stress applying member; then, an interference simulation sub-circuit is arranged to simulate the interference environment of the direct-current stray current on the pipeline after the insulating coating is stripped; in addition, in the invention, a plurality of microelectrode insertion holes penetrating into the interval gaps are also arranged on the cover plate and the insulating layer; through the measuring sub-circuit, experimental data such as potential difference, pH value, chloride ion concentration and the like between the through hole on the insulating layer and each microelectrode can be respectively obtained.
Because the distance between each microelectrode and the through hole at the simulated damage position is different, the invention can obtain experimental data of different positions of the insulating layer, thereby simulating the influence degree and the influence mode of the microelectrode on different positions in the gap for peeling the insulating layer of the pipeline after the microelectrode is interfered by direct current stray current. That is to say, the invention can monitor the local environment and the tube body corrosion electrochemical behavior of different positions under the direct current interference pipeline steel stripping coating in real time, thereby providing richer and more effective experimental data for researching the effect of parameters such as cathodic protection, external soil environment, direct current interference, strength, frequency, size of damaged points and the like on the pipeline steel corrosion behavior under the stripping coating.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. Any simple modifications, equivalent changes and modifications made to the above exemplary embodiments shall fall within the scope of the present invention.