CN104532264B - Damage and Evaluation of Cathodic Protection method and device outside a kind of pipeline - Google Patents
Damage and Evaluation of Cathodic Protection method and device outside a kind of pipeline Download PDFInfo
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- CN104532264B CN104532264B CN201410814200.0A CN201410814200A CN104532264B CN 104532264 B CN104532264 B CN 104532264B CN 201410814200 A CN201410814200 A CN 201410814200A CN 104532264 B CN104532264 B CN 104532264B
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Abstract
The invention belongs to Corrosion monitoring technical field, there is provided and damage and Evaluation of Cathodic Protection method outside a kind of pipeline, step is as follows, and 1）Pigging；2）It will be damaged outside pipeline and Evaluation of Cathodic Protection device be put into pipeline；3）Measure pipeline potential difference data；4）Make L U curve maps；5）Draw the outer damage status of pipeline and cathodic protection effect state.Present invention also offers evaluating apparatus, including first probe at both ends, the second probe are symmetricly set on, acquisition and recording device, battery section, the mileage wheel being sequentially connected between the first probe and the second probe；First probe, second probe is connected by connecting cable with acquisition and recording device, battery section respectively with acquisition and recording device and mileage wheel cable connection.The present invention solves the problems, such as the problem of detection pipeline is realized in the case of it can not manually patrol along the line, alleviates heavy dependence import instrument and higher testing cost, increases detection reliability with reducing operator's cost.
Description
Technical field
The invention belongs to Corrosion monitoring technical field, and in particular to damage and Evaluation of Cathodic Protection side outside a kind of pipeline
Method and device.
Background technology
The oil gas main pipeline for having more than 1,000,000 Km in the world at present puts into operation, to ensure the outer protection effect of pipeline,
It is widely used external anti-corrosion layer and adds cathode protection technology, and as the international technical requirements and standard generally approved and performed.For
Ensure that oil-gas pipeline long-life, safety are on active service, strengthen the evaluative meaning of the external anti-corrosion layer and cathodic protection effect to in-service pipeline
It is great.
Operation for in-service cathodic protection pipeline detects, it is external in 70~eighties of last century once using aircraft remote measurement and
Satellite communication remote measurement, data acquisition are with high costs.Pipeline anticorrosion coating and cathodic protection effect detection technology mainly have at present：Along the line
Pipe to soil potential mensuration, polarized probe method, external anti-corrosion layer ohmic leakage method（Impressed current is divided to be measured with gap current）, in multifrequency pipe
Current method（PCM methods）, Pearson came detection method（Audio leak detecting）, close spacing current potential（CIPS）With alternating current-direct current ground potential gradient
（ACVG and DCVG）Detection method, and transceiver etc. is gathered in test pile installation data, it is then using more and ripe method
PCM methods, CIPS+DCVG methods and test pile pipe to soil potential method etc..
The outer detection method of above pipeline is required to patrol survey along the line, and supplemented by artificial gait's behavior master, motor vehicle, labor intensity is big,
It is high to operating personnel's technical requirements, and efficiency is low, and human error is big, or even practises fraud, field instrumentation automatic data collection remote measurement
Limited measurement point can only be installed（General test stake）.Direct measurement pipe to soil potential needs GPS Synchronization Controls current interrupter to measure
To eliminate IR drops, referring to the A of CN 102337542.The instrument for the pipeline external surface Intelligent Measurement applied at present is mostly import, detection
It is costly（Up to 7000~8000 yuan/Km, relatively low domestic anticorrosive coat breaking point individual event detects about 4000 yuan/Km）, easily by it is artificial,
Such environmental effects.When Pipeline Crossing Program extreme terrain such as mountain range, rivers and lakes or city and Environmentally Sensitive Area or crossing-river tunnel,
And when meeting with harsh weather, artificial inspection can not be realized.
It is ultrasonic wave and leakage field robot technology that Inner Examination Technology on Pipeline is most widely used, auxiliary to have vortex, laser, TV
With electromagnetic detection etc..External U.S. GE, Russian NGKS companies, PI Corp. of Britain and Japanese NKK companies have released more advanced
Pipeline non-destructive testing robot, domestic Magnetic Flux Leakage Inspecting have realized industrial applications, and ultrasound detection is still in exploring, referring to China
Patent ZL 200510130338.X, Shengli Petroleum Administration Bureau take the lead spend 5 years complete submarine pipeline in see crawl device and inspection
Examining system is in the success of pilot scale in 2010.
The defects of leakage field and ultrasonic technique energy effective detection pipeline wall thickness, inside and outside wall corrosion damage and inner surface deform（It is super
Sound is combined with inner diameter measurement can the damage of indirect detection pipe outer wall）, it is impossible to it is accurate that pipeline external surface situation and external anti-corrosion layer leakage are provided
Point, can not reflect cathodic protection current distribution general picture and with the presence or absence of with the metalwork such as Outer Tube overlap joint, insulating joint（Method
It is blue）The information such as insulating properties, drainage battery.
Pipeline external damage is to cause one of pipe leakage, the subject matter for threatening safety.Currently examined around pipe damage
In terms of survey：The outer detection method mature and reliable of pipeline, it is widely used, but the problem of operating along on the spot and be costly is present.Pipeline
Interior detection method relies primarily on device with fluid motion, and intelligent high, manual request is low, avoids subjectivity, but require in pipeline
The transmission and reception of electricity, magnetic, sound or laser are realized in narrow and small complex space, pipeline requires shadow again to the complicated of robot micro-structural
Ring its reliability.
The advantages of being detected inside and outside extraction duct, the shortcomings that respective is avoided, design one kind can work in pipeline and need not patrol
Line can realize that the evaluation method of outer detection target has preferable production requirement and realistic meaning again.
Hyundai electronicses information technology fast development, the test of ultra-weak electronic signal, measurable voltage it have been fully able to complete
Minimum magnitude Da Nafu（10-9Volt）, measure microvolt level thermocouple sensor signal it is very universal.To multiple sensor
Signal realizes online switching at a high speed, collection and storage；It is very ripe for the application of pipeline internal walking system, such as by micromechanics with
The method that electronic information technology combines can realize the pit detection in pipeline, referring to Chinese patent ZL201110079540.X, CN
102135221 B etc..
The content of the invention
The purpose of the present invention is to overcome prior art to realize the problem of detecting pipeline in the case of it can not manually patrol along the line.
Therefore, the invention provides damage and Evaluation of Cathodic Protection method outside a kind of pipeline, comprise the following steps：
Step 1）Pigging：Pipeline is handled with wiper, and dries up tube wall, wiper must add when wax is more serious
Steel loading brush, prepared for measurement；
Step 2）It will be damaged outside pipeline and Evaluation of Cathodic Protection device be put into pipeline；
Step 3）Measure pipeline potential difference data：In pipe full commercial crude, pure oil product or other nonconductive inerts
In the case of medium, with ＜ 1m/s low flow velocities convey driving device, device walk while, acquisition and recording device record first probe and
Real-time potential difference between second probe, the real-time distance of mileage wheel tape deck walking, acquisition and recording device and mileage wheel combine
Complete pipeline distance and the corresponding data relation between potential difference；
Step 4）Make L-U curve maps：Device is taken out into pipeline after completion measuring section, current potential is extracted from acquisition and recording device 5
Difference data, time and the potential difference data of the segment pipe are obtained, from the take-off time of mileage wheel 8 and range data of device, will managed
The continuity point that road measures is made on distance L- potential difference U coordinate figures, obtains L-U curve maps；
Step 5）Obtain the outer damage status of pipeline and cathodic protection effect state：Determined according to the change of the L-U slopes of curve
Damage and cathodic protection effect state outside pipeline；
Damaged outside described pipeline and cathodic protection effect state there are following 8 kinds,（1）Ideal protection：The L-U slopes of curve
Change steadily tapers into, then judges that pipeline does not have outer damage, cathodic protection normal condition；
（2）Impaired loci be present：L-U curves are mutated downwards, are that coating has certain impaired loci or pipeline and outer metal on pipeline
Shunted after in electrical contact；
（3）It is under proteciton：Section normal gradient is obviously reduced slope over 10 earlier above after L-U curves, presses close to transverse axis, represents that pipeline is present
State under proteciton；
（4）Electric current inlet and outlet piping：The slope that some sections of L-U curves is on the occasion of with integrated curved slope on the contrary, being electric current stream
Go out pipeline conditions, the anode region that corrosive pipeline be present；Some sections of L-U curves are negative tiltedly larger, are coating aging badly broken area；It is bent
Some sections of line is parallel with transverse axis, and the section, which belongs to, to be shielded；
（5）DC influence：L-U curves translate one section to upper right side, are introduced into pipeline for stray electrical current, are flowed again from another region
Go out pipeline；One section of L-U curves lower section translation to the left, first flows out pipeline, again from another region flow ipe for stray electrical current；
（6）AC influence：, around near symmetrical fluctuation form above and below integrated curved, depositing for pipeline occurs in L-U curves section
In the state that alternative stray current influences；
（7）Pipe ends are protected：Transverse axis is worn under L-U curves, applies state under cathodic protection simultaneously for pipe ends；
（8）Drainage battery protection state：The negative tiltedly increase of L-U curves, and under wear transverse axis after stretched to the lower right of transverse axis, be
Pipeline is locally mounted with drainage（Ground connection）State during anode cell.
Present invention also offers damaging outside pipeline and Evaluation of Cathodic Protection device, including it is symmetricly set on the of both ends
One probe, the second probe, acquisition and recording device, battery section, mileage wheel between the first probe and the second probe；
First probe, the second probe are connected by connecting cable with acquisition and recording device, and the battery section is respectively with adopting
Collect logger and mileage wheel cable connection.
Also include the first leather cup and the second leather cup located at the first probe both ends, the 3rd leather cup located at the second probe both ends
With the 4th leather cup；
First leather cup passes through insulated connecting rod and second by flexible connecting rod and the first probe connection, the first probe
Leather cup is connected, and the 3rd leather cup is connected by insulated connecting rod with the second probe, the 4th leather cup passes through the elastic extension bar of company and the
Two probe connections.
Universal joint is provided between the acquisition and recording device and mileage wheel.
First probe and the second probe are using inertia ripple metal material not living.
First probe and the second probe are equipped with 1 spring contact up and down on four direction.
The beneficial effects of the invention are as follows：
1st, storage cathodic protection potential difference signal mode is measured in pipeline using " crawl device " mode in pipeline, instead of people
Work external pelivimetry curtage out of office or electromagnetic field signal（Containing external excitation）, it is especially suitable under artificial line walking hard situation to pipeline
Outer wall damages and the detection of cathodic protection effect evaluation；
2nd, the measurement, storage and calculating analysis of the continuous cathodic protection potential difference of pipeline are completed；
The 3rd, the distribution along the line of pipeline cathode protection electric current is described；
4th, the relation to be decayed according to pipeline mileage and potential difference signal provides the various states of coated pipeline, as coating damage,
The outer metal shunt point of current leakage point, interference corrosion point, cathodic protection system and high resistance（Vacantly, frozen soil, antecedent soil moisture area
Section, casing section etc.）And analysis drainage point etc., provide foundation for rear decision-making.
It is described in further details below in conjunction with accompanying drawing.
Brief description of the drawings
Fig. 1 is damage and Evaluation of Cathodic Protection schematic device outside inventive pipeline；
Fig. 2 is potential difference measurement principle schematic of the present invention；
Fig. 3 is pipeline cathode protection CURRENT DISTRIBUTION schematic diagram；
Fig. 4 is the unilateral axial cathodic protection current of pipeline and radial current relation schematic diagram；
Fig. 5 is the current relationship figure that measurement apparatus moves inlet and outlet piping section after a segment distance；
Fig. 6 is the contact potential schematic diagram between two probes and tube wall contact point；
Fig. 7 is pipeline potential difference with distance（L-U）The desired characteristics curve map of change；
Fig. 8 is coating impaired loci on pipeline（Or pipeline and the rear shunting in electrical contact of outer metal）Potential difference indicatrix
Figure；
The potential difference characteristic curve diagram under state under proteciton for pipeline be present in Fig. 9；
Figure 10 is pipeline distance and potential difference relation curve（L-U）The signal of pipeline is entered and flowed out to middle pipeline radial current
Figure；
Figure 11 flows in and out the potential difference characteristic curve diagram under pipeline for DC stray current；
Figure 12 is the potential difference characteristic curve diagram under the influence of alternative stray current；
Figure 13 is that pipe ends apply cathodic protection simultaneously（Strengthen protection）Under potential difference characteristic curve diagram；
Figure 14 is pipeline locally installation drainage（Ground connection）Potential difference characteristic curve diagram during anode cell.
In figure：1st, the first leather cup；2nd, insulated connecting rod；3rd, the first probe；4th, the second leather cup；5th, acquisition and recording device；6th, it is electric
Chi Jie；7th, flexible connecting rod；8th, mileage wheel；9th, the second probe；10th, the 3rd leather cup；11st, the 4th leather cup；12nd, universal joint；13rd, manage
Road.
Embodiment
Embodiment 1：
Damage and Evaluation of Cathodic Protection device outside a kind of pipeline are present embodiments provided, including is symmetricly set on both ends
First probe 3, second probe 9, located at first probe 3 and second probe 9 between acquisition and recording device 5, battery section 6, mileage
Wheel 8；First the 3, second probe of probe 9 is connected by connecting cable with acquisition and recording device 5, battery section 6 respectively with acquisition and recording device 5
With the cable connection of mileage wheel 8.
As shown in Fig. 2 the potential difference of measurement segment pipe of two probes i.e. between the first probe 3 and the second probe 9, the electricity
Potential difference accesses pre-amplifier unit for differential input, carries out small-signal（Microvolt level）Pretreatment（Filtering, measuring and amplifying）, then
Continue to amplify by general-purpose operation device（Millivolt level）Signal, by multicircuit switch, by the analog signal after amplification through modulus
Converter ADC is changed into data signal, and data signal is sent into memory and preserved, and above-mentioned signal path has been coordinated by singlechip controller
Into.
First probe 9 realizations of the 3, second probe are in electrical contact with inner-walls of duct, and collection capacity, which is popped one's head in, sees the current potential of pipeline section
Difference, the cathodic protection DC potential difference between the first probe 3 and the second probe 9 are sent into acquisition and recording device 5 by connecting cable,
Acquisition and recording device 5 completes preposition processing, signal amplification, multi-path choice, analog-to-digital conversion and the stored record of weak electrical potentials difference signal,
Battery section 6 is acquisition and recording device 5 and mileage wheel 8 supplies dc source, the tape deck progressive position mileage of mileage wheel 8 and recordable damage
Hinder position.Acquisition and recording device 5 is XWD1-102 potential difference recorders in the present embodiment.
Embodiment 2：
On the basis of embodiment 1, in addition to the first leather cup 1 and the second leather cup 4 located at the first 3 both ends of probe, it is located at
3rd leather cup 10 and the 4th leather cup 11 at the second 9 both ends of probe；
First leather cup 13 be connected by flexible connecting rod 7 with the first probe, first pops one's head in 3 by insulated connecting rod 2 and the
Two leather cups 4 are connected, and the 3rd leather cup 10 is connected by insulated connecting rod 2 with the second probe 9, the 4th leather cup 11 passes through even elastic extension bar
It is connected with the second probe 9.
First leather cup 1 and the 4th leather cup 11 are used to seal front and rear medium, and pressure difference-powered, the He of the second leather cup 4 is provided for device
3rd leather cup, 10 further sealing pipeline, while strengthen at the uniform velocity advancing and contacting effect for the first probe 3 and the second 9 vibration dampings of probe
Fruit, flexible connecting rod 7 play cushioning effect, increase device advance stability and at the uniform velocity property, and insulated connecting rod 2 is by the first 3 Hes of probe
Second probe 9 is electrically insulated with device, prevents the interference to gathering signal and gathers the distortion of signal.
Embodiment 3：
The present embodiment is on the basis of embodiment 2, there is provided is damaged outside a kind of pipeline as shown in Figure 1 and cathodic protection is imitated
Fruit evaluating apparatus, universal joint 12 is provided between acquisition and recording device 5 and mileage wheel 8, improves device and certain curvature pipeline is led to
Cross ability；First probe 3 and the second probe 9 use elastomer structure, prevent probe contacts and inner-walls of duct rigidity CONTACT WITH FRICTION,
Meanwhile acquisition and recording device 5, battery section 6 and the sealed pressure-resistant treatments of connecting cable joint at different levels of the present embodiment device.
Example IV：
In order to ensure the insulation between the first probe 3 and the second probe 9, both ends measuring probe uses torpescence antifriction metal (AFM)
Material copper beryllium alloy makes, and probe is eliminated " thermoelectrical potential " in the case where the continuous pressure-bearing of inner-walls of duct is slided, level pressure at the uniform velocity transport Stream
Body, four spring contacts are respectively set on the first probe 3 and the second probe 9, probe each 1 of direction up and down, four contacts with
Measurement apparatus is electrically insulated, and, as signal all the way, will add up to four road potential difference signals, each road letter between two equidirectional contacts of probe
Number continuous acquisition, switched and switched by high-speed transitions, four road signal curves are easy to Macro or mass analysis, especially for two probe water
The analysis of potential difference signal between flat contact.
Embodiment 4：
Damage and Evaluation of Cathodic Protection method outside a kind of pipeline are present embodiments provided, is comprised the following steps：
Step 1）Pigging：Pipeline is handled with wiper, and dries up tube wall, wiper must add when wax is more serious
Steel loading brush, prepared for measurement；
Step 2）It will be damaged outside pipeline and Evaluation of Cathodic Protection device be put into pipeline；
Step 3）Measure pipeline potential difference data：In pipe full commercial crude, pure oil product or other nonconductive inerts
In the case of medium, driving device is conveyed with ＜ 1m/s low flow velocities, while device is walked, the probe 3 of the record of acquisition and recording device 5 first
And the second real-time potential difference between probe 9, the real-time distance of the tape deck of mileage wheel 8 walking, acquisition and recording device 5 and mileage wheel
8 combine completion pipeline distance and the corresponding data relation between potential difference；
Step 4）Make L-U curve maps：Device is taken out into pipeline after completion measuring section, current potential is extracted from acquisition and recording device 5
Difference data, time and the potential difference data of the segment pipe are obtained, from the take-off time of mileage wheel 8 and range data of device, will managed
The continuity point that road measures is made on distance L- potential difference U coordinate figures, obtains L-U curve maps；
Step 5）Evaluate the outer damage status of pipeline and cathodic protection effect state：Determined according to the change of the L-U slopes of curve
Damage and cathodic protection effect state outside pipeline.
Step 5）Damaged outside described pipeline and cathodic protection effect state there are following 8 kinds,（1）Ideal protection：L-U curves
The change of slope steadily tapers into, then judges that pipeline does not have outer damage, cathodic protection normal condition；
（2）Impaired loci be present：L-U curves are mutated downwards, are that coating has certain impaired loci or pipeline and outer metal on pipeline
Shunted after in electrical contact；
（3）It is under proteciton：Section normal gradient is obviously reduced slope over 10 earlier above after L-U curves, presses close to transverse axis, represents that pipeline is present
State under proteciton；
（4）Electric current inlet and outlet piping：The slope that some sections of L-U curves is on the occasion of with integrated curved slope on the contrary, being electric current stream
Go out pipeline conditions, the anode region that corrosive pipeline be present；Some sections of L-U curves are negative tiltedly larger, are coating aging badly broken area；It is bent
Some sections of line is parallel with transverse axis, and the section, which belongs to, to be shielded；
（5）DC influence：L-U curves translate one section to upper right side, are introduced into pipeline for stray electrical current, are flowed again from another region
Go out pipeline；One section of L-U curves lower section translation to the left, first flows out pipeline, again from another region flow ipe for stray electrical current；
（6）AC influence：, around near symmetrical fluctuation form above and below integrated curved, depositing for pipeline occurs in L-U curves section
In the state that alternative stray current influences.
（7）Pipe ends are protected：Transverse axis is worn under L-U curves, applies state under cathodic protection simultaneously for pipe ends；
（8）Drainage battery protection state：The negative tiltedly increase of L-U curves, and under wear transverse axis after stretched to the lower right of transverse axis, be
Pipeline is locally mounted with drainage（Ground connection）State during anode cell.
The basis of the present invention：
1st, pipeline axial direction resistance R：
……………（1）
ρ --- ----pipeline material resistivity, general 0.1~0.3 Ω mm2/m。
L------- duct lengths, m.
SIt is horizontal--- ----pipeline radial cross-sectional area, mm2。
2nd, pipeline cathode protection system electrical circuit simplifies relational expression：
…………………（2）
I------- pipeline cathode protections confluence electric current, A.
U------- DC voltages, V.
R --- ----total loop resistance, Ω.
3rd, in cathodic protection system unilateral pipeline protective current IIt is unilateral：
……………………（3）
SAppearance--- ----pipeline external surface accumulates face area, m2。
J------- pipe protection current densities, μ A/m2。
D------- outer diameter tubes, m.
LIt is unilateral--- ----pipeline one side length（It is then homogeneous tube section that cathodic protection station, which build pipe end in,）, m.
In Fig. 3,4, IIt is unilateral= I1+ I2+ ……In-1+ In
I1、 I2、 ……In-1、 InThe soil electric current of the visualization of --- ----flowed out from anode, that is, flow back to pipeline
" radial current ".
I, I ' --- ----from cathodic protection confluence（That is cathode connection point）Both sides soil flowing into pipeline into negative electrode protect
Protect the electric current of confluence.
Therefore nearer apart from confluence, electric current is bigger, bigger in the potential difference of equidistant pipeline enclosure.
4th, 2 points of the maximum potential difference U on a determining deviation L interior conduits axial direction：
………………（4）
D------- internal diameter of the pipeline, mm.
According to the common anticorrosive coat used when preceding pipeline, the protecting current density that pipeline needs is generally less than 100 μ A/m2,
Widely used 3PE pipelines are then generally below 10 μ A/m2, within a general 10A of pipe protection electric current, design effective protection pipe
Within road length 100Km, Φ 610 × 11mm pipe protections length for example with 3PE is 80Km, it is necessary to unilateral protective current
1.55A, then it is 60 μ Ω that 10m, which grows the canal electrical resistance, and the maximum potential difference near confluence is 93 μ V.
Therefore according to pipe protection current density, canal electrical resistance rate（20# steel is 0.135 Ω mm2/m）, anticorrosion structure chi
The order of magnitude that very little and Protection parameters calculate maximum potential difference U is microvolt level, equivalent to the low-temperature zone induced signal of thermocouple,
So the resolution ratio of measurement apparatus input signal is defined as microvolt level（1μV）.
5th, that the combined potential to be formed is contacted with inner-walls of duct is poor for the first probe 3 and the second probe 9 during unprotect electric current：
In pipeline not logical cathodic protection current, the first probe 3 and the second probe 9 and inner-walls of duct category different metal（It is lazy
Property metal and mild steel）, because the electron work functon of different metal is different with free electron density, contact when contacting with each other be present
Potential and thermoelectric force.
In Fig. 6, the first probe 3 is with tube metal because of work function（Or work function）Contact potential is caused by difference：
………………（5）
The work function of --- ----tube metal, the first probe 3.
--- ----electronic charge, 1.6 × 10-19Coulomb.
Pipeline and probe 9 between contact potential be：
The work function of --- ----probe 3.
In Fig. 6, probe 3 is with tube metal because thermoelectric force caused by temperature difference is：
………………（6）
--- ----Boltzmann constant, K=1.38 × 10-23J/K。
The probe of --- ----the first 3 and the temperature at inner-walls of duct contact point.
The electron density of 3 metals of probe of --- ----the first, the free electron density of various metals have the identical order of magnitude
（1028/m3）.
The electron density of --- ----tube metal.
Pipeline and second probe 9 between thermoelectric force be：
The probe of --- ----the second 9 and the temperature at inner-walls of duct contact point.
When not logical cathodic protection current, combined potentials that the first probe 3 and the second probe 9 contact with inner-walls of ductFor
Four sums of the above：
………………（7）
The probe 9 of the probes of ∵ first 3 and second uses same material metal,,。
∴………………（8）
（7）Formula illustrate, first probe 3 and second probe 9 contacted with inner-walls of duct caused by combined potentialIn two touch
Point contact potential is equal in magnitude, in opposite direction, so combined potentialThe difference of the thermoelectric force of two contacts is depended mainly on,（8）
In formula, combined potentialIt is unrelated with pipeline steel, it is only relevant with the temperature difference at the contact point of the first probe 3 and the second probe 9, surveying
Measure within the limited distance of device such as 10m,, the temperature difference can be ignored, when probe is using close with tube metal free electron
Similar in degree during metal,,Close to zero,For 10-4The order of magnitude, thereforeXiang Ji
This is equal to zero, in pipeline not logical protective current, combined potentialIt is remote not reach the microvolt that thermocouple exports under high temperature difference environment
Level potential difference signal, the i.e. signal of measurement device are mainly derived from cathodic protection current caused electric signal on pipeline.
In Fig. 5, when two probes of A, B of device（It is first the 3, second probe 9 of probe in the present invention）It is mobile（I.e.
Or）When, the difference of potential difference between probeFor
--- ----two probe is between pipeline A, B and A ', B ' potential difference, V.
--- --- ----electric current flows through the electric current of cross-section of pipeline at B ', A ', A.
--- ----it is respectively the electricity that pipeline external surface consumes between A ' B ', BA ', AB, AA '
Stream, A.
The resistance of pipeline, Ω between --- ----probe A, B.
In the figure 7, slope of curve K physical significance is the difference of the potential difference after probe A, B displacement Δs LWith
The ratio between：
……………（9）
--- ----probe A, B movementsSame probe A afterwards（Or B）Between front and rear point（I.e.Or）Outside pipeline
Protecting current density needed for surface, μ A/m2。
Formula（9）In two probe between pipeline resistanceIt is certain value, so slope of curve K reflects the same probe of pipeline
The real protection current density of mobile point-to-point transmission pipe surface（Or）.
Embodiment 5：
Before using present apparatus detection, when wax is more serious, preferably existed to measuring pipeline section pigging with wiper first
Wiper installs steel brush increase treatment effect additional.Measurement apparatus is from pipe head after pigging is complete（Service end）It is sent into, it is former with commodity
Oily, pure oil product, purified natural gas or other nonconductive inert media are power, it is ensured that feed status is steady, at the uniform velocity and low speed,
If the wall condition such as tube wall incrustation, wax and seriously corroded is poor, static detection can be pinpointed at interval of 5m or 15m, effectively to reduce
Contact impact disturbs, the complete full journey of measurement apparatus " walking ", from the port of export（Receive ball end）Take out, adopted from memory and the reduction of mileage wheel 8
Collect data, according to pipeline distance-potential difference figure（L-U）Feature curve analysis pipeline coatings damage status and cathodic protection effect.
Below by way of the pipeline distance-potential difference figure measured（L-U）Indicatrix, to pipeline coatings damage and cathodic protection
The evaluation method of effect is explained.
Fig. 7 reflects from cathodic protection current confluence（Cathode line and pipeline tie point）The reason of the potential difference of pipeline along rising
Think indicatrix, i.e. damage, the ungreat mutation of soil resistivity along the line is not present in homogeneous coated pipeline（Along the line soil resistivity compared with
It is homogeneous）, cathodic protection current field areas the basic metal structures for influenceing protective current flowing are not present, and pipeline does not pass through
Situations such as sleeve pipe.The curve is the basic indicatrix of analysis conduit potential difference change, illustrates pipeline distance under normal circumstances
Anode bodies are nearer, are protected that degree is higher, and the protecting current density of acquisition is bigger, and potential difference slope of a curve is bigger, in Fig. 6
Originate slope over 10More than interlude, interludeMore than latter end。
It is probably to be applied at this that Fig. 8 reflections pipeline somewhere, which has the reason for indicatrix that current convergence flows into phenomenon, formation,
Layer is damaged, or external metallization component（Sleeve pipe containing almost exposed outer surface）Electrically overlap joint etc. be present with protective conduit, lead
Current convergence is caused to flow into, its indicatrix shows as slope mutation, potential differenceHigher, current leakage is more serious, pipeline coatings
Potential difference curve behind damage position has the feature for continuing to press close to L axles.
Fig. 9 reflects the indicatrix of pipeline pipeline section under proteciton, shows as the slope over 10 and is obviously reduced compared with leading portion normal gradient,
And this section of curve presses close to L axles, and the protective current absolute value of inflow is smaller, therefore, the pipe of the later pipeline in M2 regions should be checked
Current potential, determine potentiostat output current.
Figure 10 reflects electric current flowing into pipeline and flows out the indicatrix of pipeline, and A, B, C and D share four region curves in figure
Tiltedly change, illustrate the anode region that electric current flows out pipeline from these regions, corrosive pipeline be present, while in Field potentials such as X, Y, Z
Drop bigger, the protective current of consumption is more, and M sections are parallel with L axles, and the section, which belongs to, to be shielded, such as conduit crossing, curve after M sections
Slope diminishes, and the protecting current density of flowing into pipeline is substantially insufficient, and Figure 10 category puts into operation the test curve of time longer old pipeline, applies
Layer Aging Damage is more serious.
Figure 11 reflection DC stray currents flow in and out the potential difference indicatrix of a segment pipe, direct current stray electrical in figure
Stream enters pipeline from X regions, flows out pipeline from Y regions, and equivalent to the electric current for adding cathodic protection, curvilinear characteristic is " raising "
Potential difference signal, similarly, stray electrical current is from M regions flowing into pipeline, from n-quadrant outflow pipeline equivalent to " having forced down " potential difference
Value, for example DC loop be present in conduit region by interference section, the user's electric utility of direct current gasification railway in pipeline
When, part " raising " or " forcing down " curve occurs in potential difference（Curve may no to scale during serious interference）Spy
Sign.
Figure 12 reflection alternative stray currents pass in and out the potential difference indicatrix of a segment pipe, and alternating current then increases into pipeline
Big potential difference, outflow pipeline then reduce potential difference, and this feature curve and AC signal amplitude of variation, frequency are closely related, interference
Curve may no to scale when serious.
Respectively there is an indicatrix that a cathodic protection system protects the pipeline at the both ends of Figure 13 reflection pipelines, M regions in figure
For " centre " of duplicate protection（It is not necessarily the midpoint area of duct length）Area is superimposed, potential difference passes through L axles and non-protected electricity
Stream is zero, but flow direction of the electric current in pipeline changes, equivalent to the positive and negative probe for having exchanged measurement apparatus（Potential difference is just
Negative pole only has relative meaning）, the probe A current potential on the left of M regions>Probe B current potential, then on the contrary, in curve map on the right side of M regions
On reflect M regions before and after potential difference symbol it is opposite.
Figure 14 reflection pipelines locally install drainage sacrificial anode（Equivalent to electrolytic grounding cell）When potential difference indicatrix.
Measurement apparatus is anode cell electric current I ' and the additional protection electricity of pipeline close in anodic process from protection station to the movement of drainage anode
It is in opposite direction to flow I, the potential difference after superposition diminishes simultaneously reversely（General drainage area I '》I）, in anode cell connecting pipe wiring point
Characteristics of Mutation, anode cell electric current I ' and the additional protective current I directions phase of pipeline on the right side of M points is presented in position M, potential difference
Together, the unexpected Reverse recovery of potential difference influences zone state to drainage anode, will appear from after the M of wiring point position away from anode cell direction
Maximum, with more remote from anode cell, potential difference influenceed by anode cell it is smaller, it is normal when curvilinear regression is without drainage battery
State.
The category feature curve of the above 8（Fig. 7~14）Reflection is basic characteristic feature form, and these forms are to form reality
The basic ingredient of curve, actual curve form will become complicated because of various combinations, but these grown form Producing reasons are point
The key of pipeline actual state and cathodic protection current situation is analysed, effectively excluding all kinds of interference superposed signals of potential difference signal is
Complete the important leverage of measurement, and between popping one's head in ultra-weak electronic signal measure be related to measurement apparatus method of the present invention analysis into
Lose, safeguard is taken to its major influence factors：
First, instrument performance in ensuring equipment：Electronic instrument meets the pouring of conduit running, instrument input impedance is high,
The μ V levels of resolution ratio 1, from less temperature drift and high string common-mode rejection ratio（SMR、CMR）, high reliability integrated transporting discharging, suppression
High-frequency noise interference component processed etc..
Second, the requirement of process portion：The insulation between the first probe 3 and the second probe 9 is ensured, using inertia torpescence
Metal material makes probe, probe is eliminated " thermoelectrical potential " in the case where the continuous pressure-bearing of inner-walls of duct is slided, level pressure at the uniform velocity transport Stream
Body, four spring contacts are respectively set on the first probe 3 and the second probe 9（Pop one's head in each 1 of direction up and down）, four contacts with
Measurement apparatus is electrically insulated, and two probes are equidirectional（That is, 12. -12 points of clock, 6. -6 points, 9. -9 points, 3. -3
Point）As signal all the way between contact, four road potential difference signals are added up to, each road signal continuous acquisition, are switched by high-speed transitions
Switching, four road signal curves are easy to Macro or mass analysis, especially between two probe water-level contacts（I.e. 9. -9 points, 3. -3 points）
The analysis of potential difference signal.For the new pipeline that puts into operation, its inwall can simplify measurement without the medium sediment such as pipe scale, corrosion product
Device, acquisition and recording device 5 are not required to multiple signals conversion portion, and four contacts of the first probe 3 and the second probe 9 are passed through into insulation
Connecting rod 2 insulate with device, and signal can meet to analyze all the way for collection.
Third, rational e measurement technology method requirement.Implement energization and power operation to cathodic protection system and change to protect
Protect the operation of size of current；Whole verification and microcosmic explication de texte can be carried out to the signal that measurement apparatus gathers；Secondly use
Two sets of measurement apparatus complete the data reappearance analysis with a Detection task, integrated；3rd is that same pipeline is established
The history detection archives of " longitudinal direction ", the detection data after particularly newly-built pipeline puts into operation act on " benchmark "；4th is to carry out
" transverse direction " detection analysis file of equal service condition pipeline, the data comparison for the pipeline such as buried while be on active service parallel.
The part and the well-known components and common structure of the structure category industry or conventional hand that the present embodiment does not describe in detail
Section, is not described one by one here.
It is exemplified as above be only to the present invention for example, do not form the limitation to protection scope of the present invention, it is all
It is to be belonged to the same or analogous design of the present invention within protection scope of the present invention.
Claims (1)
1. damage and Evaluation of Cathodic Protection method outside a kind of pipeline, it is characterised in that comprise the following steps：
Step 1）Pigging：Pipeline is handled with wiper, and dries up tube wall, when wax is serious, wiper installs steel brush additional,
Prepared for measurement；
Step 2）It will be damaged outside pipeline and Evaluation of Cathodic Protection device be put into pipeline；
Damaged outside the pipeline and Evaluation of Cathodic Protection device includes being symmetricly set on the first of both ends and popped one's head in（3）, second
Probe（9）, located at the first probe（3）With the second probe（9）Between the acquisition and recording device that is sequentially connected（5）, battery section（6）, it is inner
Journey wheel（8）；
First probe（3）, second probe（9）Pass through connecting cable and acquisition and recording device（5）It is connected, the battery section（6）
Respectively with acquisition and recording device（5）With mileage wheel（8）Cable connection；
Step 3）Measure pipeline potential difference data：In pipe full commercial crude, pure oil product or other nonconductive inert media
In the case of, the evaluating apparatus is driven with the conveying of ＜ 1m/s low flow velocities, while device is walked, acquisition and recording device（5）Record the
One probe（3）With the second probe（9）Between real-time potential difference, mileage wheel（8）The real-time distance of tape deck walking, collection note
Record device（5）With mileage wheel（8）With reference to completion pipeline distance and the corresponding data relation between potential difference；
Step 4）Make L-U curve maps：Device is taken out into pipeline after completion measuring section, from acquisition and recording device（5）Middle extraction potential difference
Data, time and the potential difference data of the segment pipe are obtained, from the mileage wheel of device（8）Take-off time and range data, it will manage
The continuity point that road measures is made on distance L- potential difference U coordinate figures, obtains L-U curve maps；
Step 5）Draw the outer damage status of pipeline and cathodic protection effect state：According to L-U curves with the presence or absence of saltus step, slope
Change determines to damage outside pipeline and cathodic protection effect state；
Damaged outside described pipeline and cathodic protection effect state there are following 8 kinds,
（1）Ideal protection：The change of the L-U slopes of curve steadily tapers into, then judges that pipeline does not have outer damage, cathodic protection is just
Normal state；
（2）Impaired loci be present：L-U curves are mutated downwards, are that coating is present beyond certain impaired loci or pipeline and this pipeline on pipeline
External metallization component it is in electrical contact after shunt；
（3）It is under proteciton：Section normal gradient is obviously reduced slope over 10 earlier above after L-U curves, presses close to transverse axis, represents that pipeline is present and owes to protect
Shield state；
（4）Electric current inlet and outlet piping：The slope that some sections of L-U curves is on the occasion of with integrated curved slope on the contrary, being electric current effuser
Road state, the anode region of corrosive pipeline be present；Some sections of L-U curves are negative tiltedly larger, are coating aging badly broken area；Curve
A little sections are parallel with transverse axis, and the segment pipe does not have exchanging electrical current with extraneous；
（5）DC influence：L-U curves translate one section to upper right side, are introduced into pipeline for stray electrical current, are flowed out again from other regions
Pipeline；One section of L-U curves lower section translation to the left, first flows out pipeline, again from other region flow ipes for stray electrical current；
（6）AC influence：, around near symmetrical fluctuation form above and below integrated curved, for pipeline existing and handing over occur in L-U curves section
Flow the state that stray electrical current influences；
（7）Pipe ends are protected：Transverse axis is worn under L-U curves, is applied with state during cathodic protection simultaneously for pipe ends；
（8）Drainage battery protection state：The negative tiltedly increase of L-U curves, and under wear transverse axis after stretched to the lower right of transverse axis, be pipeline
Part is mounted with state during drainage anode cell.
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| CN104897856A (en) * | 2015-06-01 | 2015-09-09 | 广东省特种设备检测研究院 | Sample pipe for verifying testing capability of erosion resistant layer detector, and verifying method |
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| CN105586596A (en) * | 2016-03-28 | 2016-05-18 | 沈阳龙昌管道检测中心 | Pipeline corrosion and protection experiment system |
| CN106370716A (en) * | 2016-08-22 | 2017-02-01 | 合肥德泰科通测控技术有限公司 | Deeply-buried pipeline online long-distance detection flaw detection system |
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| CN109989068B (en) * | 2017-12-29 | 2020-11-10 | 北京中盈安信技术服务股份有限公司 | Method and device for extracting cathodic protection pipe section |
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| CN109628938A (en) * | 2018-12-29 | 2019-04-16 | 江苏科盾检测技术有限公司 | A kind of gas pipeline cathodic protection detection device |
| CN111876786B (en) * | 2020-06-19 | 2022-07-05 | 中国石油天然气股份有限公司 | Remote monitoring method and device for cathode protection of buried pipeline |
| CN112522713A (en) * | 2020-12-24 | 2021-03-19 | 西南石油大学 | Long-distance pipeline protection device for crossing highway |
| CN115821270A (en) * | 2022-10-31 | 2023-03-21 | 浙江浙能天然气运行有限公司 | Internal detection method for oil and gas pipeline cathode current protection detection |
| CN117821984B (en) * | 2024-03-04 | 2024-05-24 | 成都秦川物联网科技股份有限公司 | Intelligent gas pipeline cathode protection intelligent detection method and Internet of things system |
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| DE3721205A1 (en) * | 1987-06-26 | 1989-01-05 | Pfaudler Werke Ag | METHOD FOR DETERMINING DAMAGE TO A CORROSION PROTECTIVE LAYER AND MEASURING DEVICE FOR CARRYING OUT THIS METHOD |
| CN101451812B (en) * | 2007-12-07 | 2012-03-07 | 中国石化集团胜利石油管理局钻井工艺研究院 | Detection device for detecting deformation of oil gas delivery conduit |
| CN201662525U (en) * | 2010-04-12 | 2010-12-01 | 天津市水利科学研究院 | Cathode protection monitoring probe and cathode protection monitoring probe monitoring system |
| BRPI1102062A2 (en) * | 2011-05-27 | 2014-02-04 | Inst Pesquisas Tech | METHOD AND EQUIPMENT FOR IDENTIFYING AND MEASURING ALTERNATED CHAIN INTERFERENCE IN BURIED DUCTS |
| CN102829331A (en) * | 2012-08-09 | 2012-12-19 | 北京中盈安信技术服务有限公司 | Efficient safety maintenance management method for oil and gas pipelines |
| CN204455294U (en) * | 2014-12-24 | 2015-07-08 | 中国石油天然气股份有限公司 | A kind of pipeline damages outward and Evaluation of Cathodic Protection device |
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