CN107643321A - Multifrequency alternating-current field fingerprint technique metal pipeline corrosion detecting technology based on phase identification - Google Patents
Multifrequency alternating-current field fingerprint technique metal pipeline corrosion detecting technology based on phase identification Download PDFInfo
- Publication number
- CN107643321A CN107643321A CN201710788090.9A CN201710788090A CN107643321A CN 107643321 A CN107643321 A CN 107643321A CN 201710788090 A CN201710788090 A CN 201710788090A CN 107643321 A CN107643321 A CN 107643321A
- Authority
- CN
- China
- Prior art keywords
- voltage
- pipeline
- current
- pair
- frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Abstract
A kind of metallic conduit defect detecting technique based on multifrequency alternating-current field fingerprint technique, apply the ac-excited electric current of frequency from high to low to tested pipeline, electric current is set gradually to be permeated from pipeline outer wall to inner-walls of duct in the presence of Kelvin effect, the presence of defect can change the amplitude and phase of measured signal, and depth of defect can be solved by the maximum phase angle for choosing a series of voltage signal.The present invention can measure absolute deficiency depth, without measuring reference voltage, primary voltage and original wall thickness, have good anti-drift, suitable for long-term on-line monitoring.
Description
Technical field
Field involved in the present invention is mainly oil gas metallic conduit defects detection and on-line monitoring, specifically, is related to
A kind of detection of oil gas metallic conduit depth of defect and on-line monitoring technique.Concrete technical scheme is：In tested metallic conduit
The both ends in region to be measured, two current injection electrodes of fixed installation spaced apart so that the electric current in pipeline region to be measured point
Cloth is uniformly distributed as far as possible；Then measuring electrode is fixedly mounted according to certain rule in pipeline region to be measured, along pipeline axial direction upper two
Individual adjacent electrode forms a measuring electrode pair；Tube metal region between electrode pair can be equivalent to a resistance, because
This can produce a voltage in the presence of exciting current, between electrode pair；To tested metallic conduit injected frequency from high to low
One group of ac-excited electric current, measure and record the magnitude of voltage under the current excitation of each different frequency；Due to there is skin
Effect, when injecting high frequency pumping electric current, electric current on pipeline by integrated distribution in the shallow-layer close to pipeline outer wall, with swashing
Encourage the reduction of power frequency, the electric current on pipeline gradually will permeate from pipeline outer wall to inner-walls of duct, therefore different frequency electric current
Corresponding measurement voltage is different.Because the presence of defect can change the amplitude of measurement voltage, while also can be more significantly
Change the phase of measurement voltage, therefore the phase angle of each magnitude of voltage can be calculated, be designated asΨ f , then look for out a maximum
Phase angleΨ fmax , then utilizeΨ fmax The depth of defect can be obtained.
Traditional DC fields fingerprint technique（Direct Current Field Signature Method, DCFSM）Substantially
It is a kind of relative wall thickness's detection technique, i.e., the original thickness of tested pipeline must be accurately measured, then according to voltage signal
The situation of change of relative wall thickness is judged in change, if after the maintenance of DCFSM circuit systems is changed, must remeasure tested
The actual wall thickness value of pipeline, for buried pipeline or submarine pipeline, this is clearly difficult to realize.Secondly, DCFSM technologies
At the beginning of system is installed, it is necessary to accurate measurement simultaneously records raw voltage values, afterwards instrument system it is whole during one's term of military service, survey
The voltage measured is required for carrying out ratio computing with primary voltage；And long-term on-line monitoring equipment is used as, the aging of component,
Change of working environment etc. can all cause instrument system that obvious drift occurs, therefore DCFSM operation principle determines its nothing
Method overcomes measurement error caused by drift.Furthermore traditional DCFSM is additionally provided with reference plate, it is disposed with reference plate with reference to electricity
Pole, only it is electrically connected by exciting current cable between reference plate and tested pipeline, is filled out between reference plate and tested pipeline
Filled with insulating materials；Research shows that the temperature difference between reference plate and tested pipeline can cause very big measurement error, and industry is now
Field typically reduces the error caused by the temperature difference by the method for temperature adjustmemt, but if temperature sensor damages, for underground pipe
Road, especially submarine pipeline etc. are difficult or can not repair the working environment of temperature sensor, and whole DCFSM systems no longer will can
Normal work.
Therefore, effective benefit of the invention is：The absolute measurement to depth of defect can be achieved in the present invention first, i.e., no longer
Need the original wall thickness value of measurement tested pipeline；Secondly the present invention need not set reference plate, caused by avoiding temperature change
Adverse effect；Furthermore the present invention need not measure primary voltage, only by the phase information of measurement signal in itself can solve by
Survey the depth value of defect.
Background technology
Corrosion is to cause the most important factor of oil gas metallic conduit leakage, China's gas oil pipe leakage Frequent Accidents, because
A kind of safe efficient, reliable metal pipeline corrosion detecting technology of this exploitation seems most important.And with Integrity Management
Concept is goed deep into, and the detection technique of off-line type will necessarily be substituted by online real time monitoring.Petrochemical industry is wide at present
A kind of corrosion monitoring technology of general use --- the field fingerprint technique based on direct current potential drop method, its operation principle are as follows：
1st, in two exciting current electrodes of both ends fixed installation spaced apart in tested metallic conduit region to be measured, this is passed through
Two electrodes inject the continuous current excitation electric current of certain amplitude to tested pipeline；Measurement is fixedly mounted in tested pipeline region to be measured
Electrode matrix, the adjacent electrodes in upper two of axial direction form a pair of measuring electrodes pair；One piece and tested pipeline material identical are set
Homogeneity reference plate, reference electrode is set on reference plate, reference plate is electrically connected with tested pipeline by current cable, reference plate with
Insulating materials is filled between tested pipeline, prevents both from the electrical connection outside cable connection point occurs.
2nd, the tube metal body between a pair of measuring electrodes pair can be considered as an equivalent electric resistance body, once measured zone
Measuring electrode matrix determine after, the length and width of equivalent electric resistance body will all keep constant, only corrode the defects of it is caused
The resistance that can change equivalent electric resistance body, therefore the effect of the torrent electric current in constant amplitude is thinned in the thickness of equivalent electric resistance body
Under, the voltage signal situation of change of measuring electrode pair is to represent the situation of change of measured zone wall thickness.
3rd, at the beginning of the installation of DCFSM systems, the original wall thickness value of record tested region need to be measured, is designated asWT(t 0 ).Also simultaneously
The initial reference voltage for recording measurement reference electrode will be measured, be designated asV ref （t 0 ）, and the initial measurement electricity of measuring electrode pair
Pressure, is designated asV i （t 0 ）,.In instrument system during one's term of military service, tested pipeline is corroded, and will now be measured on obtained pipeline
It is tested voltage and reference voltage and is designated as respectivelyV i （t x ）WithV ref （t x ）, recycle below equation to calculate corrosion depth：
FC i (t x ）=((V i (t x )/V i (t 0 ))/Vref(t x )/V ref (t 0 )-1)×1000 （1）
In formula：
V i （t 0 ）,V i （t x ）- initial time and the tested voltage at corrosion moment；
V ref （t 0 ）,V ref （t x ）- initial time and the reference voltage at corrosion moment；
D(t x )=WT(t 0 )-WT(t 0 )×1000/(FC i (t x )+1000) （2）
In formula：D(t x The depth of)-defect；WT(t 0 The original wall thickness of)-tested pipeline；
By formula（1）Calculated accordingly as can be seen that DCFSM need to introduce reference voltage, and need to enter with primary voltage
Row ratio computing；And DCFSM belongs to long-term on-line monitoring equipment, in practical engineering application, with the aging of instrument system with
And various drifting problems, including baseline drift and null offset will necessarily occur for change of equipment working environment etc., instrument system
Deng, that is to say tested voltage and reference voltage all and meanwhile increase or reduce identical amplitude.By formula（1）Understand, with reference to electricity
Pressure and tested voltage increase or reduced same numerical value simultaneously, and final ratio will change, therefore drift can refer to field
The testing result of line method causes very big error.By formula（2）Understand, DC fields fingerprint technique also needs to standard when calculating depth of defect
Really the original wall thickness of measurement tested pipeline, the measurement error of original wall thickness can also adversely affect to the calculating of depth of defect,
Once its circuit system is damaged and carried out after changing, it is necessary to remeasure the actual wall thickness value of tested pipeline as original
Wall thickness value, for buried pipeline or submarine pipeline, this work is very difficult to realization；
This patent is directed to one kind and is based on frequency-changing AC field fingerprint technique metallic conduit defect detecting technique, and the technology no longer needs
Measure reference voltage, it is not necessary to measure primary voltage, it is not necessary to measure the original wall thickness of tested pipeline, only pass through voltage signal
Phase carries out calculating assessment to depth of defect, can effectively eliminate system drifting, temperature change, original wall thickness measurement mistake
The influence to measurement such as difference.
The content of the invention
The present invention can not measure absolute deficiency depth primarily directed to DC fields fingerprint technique traditional at present, need to introduce ginseng
Examine voltage and lacked so as to cause that easily very big measurement error etc. can be introduced by the temperature difference of drift interference, reference plate and tested pipeline
A kind of point, it is proposed that multifrequency alternating-current field fingerprint metallic conduit defect detecting technique.Specifically, the technology is first in tested pipeline
The both ends in region to be measured, two current injection electrodes of fixed installation spaced apart, in pipeline region to be measured according to certain
Measuring electrode matrix is fixedly mounted in rule, and axially upper two adjacent electrodes form a pair of measuring electrodes pair；Electricity is injected by electric current
Pole applies a series of ac-excited electric current of frequencies from high to low to tested pipeline, makes electric current from pipeline outer wall using Kelvin effect
Gradually permeate, measure and voltage caused by recording the exciting current under different frequency to inner-walls of duct, obtain each voltage
Phase angle, be designated asΨ f , utilize the phase angle of maximumΨ fmax The defects of tested region can be obtained depth.
So-called Kelvin effect refers to, when alternating current passes through conductor, distribution of the electric current in conductors cross is uneven
Even, the highest current density of conductive surface, and the frequency of alternating current is higher, this trend is more obvious, and the phenomenon is referred to as becoming
Skin effect (skin effect), Kelvin effect is also referred to as kelvin effect.This electric current is referred to as skincurrent, its skin depthδBy
Formula（3）Determine：
δ=1/(πμ r μ 0 σf)½ （3）
Formula（3）Inμ r For the relative permeability of tested pipeline material,μ 0 For air permeability,σFor tested pipeline material
Electrical conductivity,fIt is the frequency of exciting current.By formula（3）Know, with the reduction of exciting current frequency, the skin that becomes of skincurrent
DepthδIt will increase, skincurrent gradually will permeate from metallic conduit outer wall to metal pipe internal wall, and this will cause electric current to flow through
The depth increase of regional metal block, it that is to say that electric current flows through the equivalent resistance in region and reduced, in the exciting current of identical amplitude
Under effect, the voltage between measuring electrode will be gradually reduced, while the phase angle of corresponding voltage will also change.It is if tested
Pipeline existing defects, then defect can significantly change the phase angle of voltage, therefore the present invention utilizes the maximum of voltage phase angleΨ fmax Solve the depth of tested region defectd, concrete scheme step is as follows：
（1）A pair of current injection electrodes are installed at the both ends in metallic conduit region to be measured, in pipeline arrangement measurement in region to be measured
Electrode matrix, along pipeline axial direction, two adjacent measuring electrodes form a pair of measuring electrodes pair；All electrodes are fixedly mounted on
On tested pipeline, therefore the on-line monitoring to tested pipeline defect can be realized as steps described below：
（2）By current injection electrode, to the ac-excited electric current of tested pipeline injected frequency from high to low, the skin effect that becomes is utilized
Should, the electric current on metallic conduit is gradually permeated from the shallow-layer of pipeline outer wall to inner-walls of duct, measure and record each excitation frequency
The voltage of a pair of measuring electrodes pair, is designated as under rateV f ；
（3）Calculate each voltageV f Phase angle, be designated asΨ f ；
（4）Search out the phase angle of maximumΨ fmax , the defects of tested pipeline can be calculated using following formulad：
d=-2.004Ψ fmax +10.5。
Beneficial effects of the present invention：Apply a series of ac-excited electric currents of frequency from high to low, measurement to tested pipeline
One group of voltage is obtained, the depth of defect is solved using maximum voltage phase angle, the present invention no longer needs to measure primary voltage, no longer
Reference plate is set, absolute wall thickness's loss measurement can be carried out, the defects of being highly suitable for monitoring metallic conduit on-line for a long time.
Brief description of the drawings
Fig. 1 DC fields fingerprint technique schematic diagrams
Fig. 2 multifrequency alternating-current field fingerprint technique schematic diagrams
The phase angle of Fig. 3 difference defects.
Embodiment
Details are as follows for one embodiment of the present of invention：
The present invention is the metallic conduit defect detecting technique of multifrequency alternating-current field fingerprint technique, and specific implementation step is as follows：
（1）It is 10mm to choose an endwall thickness, caliber 219mm, the ordinary carbon steel pipeline that length is 1000mm as measurand,
A pair of current excitation electrodes are welded in pipe ends, in the duct heart outer wall welded and installed measuring electrode matrix, measured on axial direction
Electrode spacing is 35mm；
（2）Distinguish the defects of working depth is 1mm, 2mm, 3mm, 4mm, 5mm and 6mm in inner-walls of duct corresponding to measuring electrode,
The size of defect is 35mm × 35mm；
（3）According to the material property of tested pipeline, the frequency of exciting current is adjusted, according to the calculation formula of skincurrent so that
The skin depth of skincurrent using 0.1mm to wait increment incremented by successively, i.e., sets 100 Frequency points altogether from 0.1mm to 10mm；
（4）Magnitude of voltage of 6 pairs of measuring electrodes under the exciting current of different frequency is measured successively；
（5）The phase angle of every group of voltage is calculated respectivelyΨ f , but utilize maximum phase angleΨ fmax And lacked according to final calculate
The defects of formula of sunken depth is calculated depth is as shown in the table：
Claims (3)
- A kind of 1. frequency-changing AC potential drop metallic conduit defect detecting technique based on phase identification, in metallic conduit region to be measured A pair of current injection electrodes of both ends installation spaced apart, in pipeline region to be measured arrangement measuring electrode matrix；Along pipe Road axial direction, two adjacent measuring electrodes form a pair of measuring electrodes pair；All electrodes are fixedly mounted on tested pipeline, because This can realize the detection to tested pipeline defect as steps described below：（1）By current injection electrode, to the ac-excited electric current of tested pipeline injected frequency from high to low, the skin effect that becomes is utilized Should, the CURRENT DISTRIBUTION on metallic conduit is gradually permeated from the shallow-layer of pipeline outer wall to inner-walls of duct, measure and record each sharp The voltage between certain a pair of measuring electrode pair under frequency is encouraged, and is designated asV f ；（2）Calculate each voltageV f Phase angle, be designated asΨ f ；（3）Search out the phase angle of maximumΨ fmax , the defects of tested pipeline can be calculated using following formulad：d=-2.004Ψ fmax +10.5。
- 2. according to claim point 1, the present invention can be used for offline inspection, it can also be used to monitor on-line, and according to accuracy of detection Requirement, the frequency of exciting current can make corresponding adjustment.
- 3. according to claim point 1, excitation current source is made up of high-precision AC current source, the voltage between measuring electrode pair by High-precision AC voltage tester measurement obtains.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710788090.9A CN107643321B (en) | 2017-09-05 | 2017-09-05 | Multi-frequency alternating current field fingerprint method metal pipeline corrosion detection technology based on phase identification |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710788090.9A CN107643321B (en) | 2017-09-05 | 2017-09-05 | Multi-frequency alternating current field fingerprint method metal pipeline corrosion detection technology based on phase identification |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN107643321A true CN107643321A (en) | 2018-01-30 |
| CN107643321B CN107643321B (en) | 2020-03-24 |
Family
ID=61110914
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710788090.9A Active CN107643321B (en) | 2017-09-05 | 2017-09-05 | Multi-frequency alternating current field fingerprint method metal pipeline corrosion detection technology based on phase identification |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN107643321B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108680607A (en) * | 2018-08-30 | 2018-10-19 | 四川大学 | Pipeline crack corrosion monitoring process based on multi-communication potential drop |
| CN108845000A (en) * | 2018-08-20 | 2018-11-20 | 四川大学 | A kind of method of pulsed field fingerprint technique measurement defect of pipeline |
| CN110133054A (en) * | 2019-06-14 | 2019-08-16 | 中国特种设备检测研究院 | A kind of metallic conduit characteristic analysis system |
| CN110133053A (en) * | 2019-06-14 | 2019-08-16 | 中国特种设备检测研究院 | A kind of Metal pipeline corrosion monitoring method and system |
| CN110220947A (en) * | 2019-06-14 | 2019-09-10 | 中国特种设备检测研究院 | A kind of corrosive pipeline degree determines method |
| CN110470726A (en) * | 2019-08-14 | 2019-11-19 | 中国特种设备检测研究院 | Steel pipe defect inspection method and device based on multifrequency electromagnetism |
| CN114090942A (en) * | 2021-11-11 | 2022-02-25 | 四川大学 | High-temperature refining pipeline online monitoring method based on multi-sensor fusion |
| CN116256305A (en) * | 2022-03-14 | 2023-06-13 | 中国特种设备检测研究院 | Corrosion monitoring system and method |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102243197A (en) * | 2011-04-25 | 2011-11-16 | 中国地质大学（武汉） | Nondestructive testing method based on skin effect resistance |
| CN102759567A (en) * | 2012-07-18 | 2012-10-31 | 南昌航空大学 | Eddy current testing recognition and evaluation method for defects of inner wall and outer wall of steel pipe under direct current magnetization |
| CN102954998A (en) * | 2011-08-26 | 2013-03-06 | 中国石油天然气股份有限公司 | Steel pipeline wall thickness abnormal change noncontact detection method |
| CN103267723A (en) * | 2013-04-16 | 2013-08-28 | 四川大学 | Detection method for metal pipes and container pitting based on field signature method |
| CN103472098A (en) * | 2013-04-16 | 2013-12-25 | 四川大学 | Method for measuring residual thickness of metal pipeline or metal pressure container after local corrosion |
| CN106153713A (en) * | 2016-06-28 | 2016-11-23 | 中国计量大学 | A kind of metallic conduit defect in inner surface detection device |
| CN106501318A (en) * | 2016-11-07 | 2017-03-15 | 四川大学 | A kind of metallic conduit defect detecting technique based on frequency-changing AC fall-of-potential method |
-
2017
- 2017-09-05 CN CN201710788090.9A patent/CN107643321B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102243197A (en) * | 2011-04-25 | 2011-11-16 | 中国地质大学（武汉） | Nondestructive testing method based on skin effect resistance |
| CN102954998A (en) * | 2011-08-26 | 2013-03-06 | 中国石油天然气股份有限公司 | Steel pipeline wall thickness abnormal change noncontact detection method |
| CN102759567A (en) * | 2012-07-18 | 2012-10-31 | 南昌航空大学 | Eddy current testing recognition and evaluation method for defects of inner wall and outer wall of steel pipe under direct current magnetization |
| CN103267723A (en) * | 2013-04-16 | 2013-08-28 | 四川大学 | Detection method for metal pipes and container pitting based on field signature method |
| CN103472098A (en) * | 2013-04-16 | 2013-12-25 | 四川大学 | Method for measuring residual thickness of metal pipeline or metal pressure container after local corrosion |
| CN106153713A (en) * | 2016-06-28 | 2016-11-23 | 中国计量大学 | A kind of metallic conduit defect in inner surface detection device |
| CN106501318A (en) * | 2016-11-07 | 2017-03-15 | 四川大学 | A kind of metallic conduit defect detecting technique based on frequency-changing AC fall-of-potential method |
Non-Patent Citations (4)
| Title |
|---|
| FANGJI GAN等: "Inner defect depth detection using a multifrequency alternating current potential drop technique", 《AIP ADVANCES》 * |
| FANGJI GAN等: "Investigation of pitting corrosion monitoring using field signature method", 《MEASUREMENT》 * |
| 李宇庭等: "场指纹法无损监测技术综述", 《仪器仪表学报》 * |
| 李宇庭等: "基于交流场指纹法的金属管道缝隙腐蚀监测方法", 《仪器仪表学报》 * |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108845000A (en) * | 2018-08-20 | 2018-11-20 | 四川大学 | A kind of method of pulsed field fingerprint technique measurement defect of pipeline |
| CN108680607A (en) * | 2018-08-30 | 2018-10-19 | 四川大学 | Pipeline crack corrosion monitoring process based on multi-communication potential drop |
| CN110220947B (en) * | 2019-06-14 | 2021-11-30 | 中国特种设备检测研究院 | Method for determining corrosion degree of pipeline |
| CN110133053A (en) * | 2019-06-14 | 2019-08-16 | 中国特种设备检测研究院 | A kind of Metal pipeline corrosion monitoring method and system |
| CN110220947A (en) * | 2019-06-14 | 2019-09-10 | 中国特种设备检测研究院 | A kind of corrosive pipeline degree determines method |
| CN110133054A (en) * | 2019-06-14 | 2019-08-16 | 中国特种设备检测研究院 | A kind of metallic conduit characteristic analysis system |
| CN110133053B (en) * | 2019-06-14 | 2024-02-02 | 中国特种设备检测研究院 | Metal pipeline corrosion monitoring method and system |
| CN110133054B (en) * | 2019-06-14 | 2024-02-02 | 中国特种设备检测研究院 | Metal pipeline characteristic analysis system |
| CN110470726A (en) * | 2019-08-14 | 2019-11-19 | 中国特种设备检测研究院 | Steel pipe defect inspection method and device based on multifrequency electromagnetism |
| CN110470726B (en) * | 2019-08-14 | 2023-03-07 | 中国特种设备检测研究院 | Steel pipeline defect detection method and device based on multi-frequency electromagnetism |
| CN114090942A (en) * | 2021-11-11 | 2022-02-25 | 四川大学 | High-temperature refining pipeline online monitoring method based on multi-sensor fusion |
| CN114090942B (en) * | 2021-11-11 | 2023-04-21 | 四川大学 | High-temperature smelting pipeline online monitoring method based on multi-sensor fusion |
| CN116256305A (en) * | 2022-03-14 | 2023-06-13 | 中国特种设备检测研究院 | Corrosion monitoring system and method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN107643321B (en) | 2020-03-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107643321A (en) | Multifrequency alternating-current field fingerprint technique metal pipeline corrosion detecting technology based on phase identification | |
| EP2800963B1 (en) | Monitoring a conductive fluid conduit | |
| Raja et al. | Influence of crack length on crack depth measurement by an alternating current potential drop technique | |
| CN103472098A (en) | Method for measuring residual thickness of metal pipeline or metal pressure container after local corrosion | |
| CN108845000A (en) | A kind of method of pulsed field fingerprint technique measurement defect of pipeline | |
| CN106501318A (en) | A kind of metallic conduit defect detecting technique based on frequency-changing AC fall-of-potential method | |
| Li et al. | Novel method for sizing metallic bottom crack depth using multi-frequency alternating current potential drop technique | |
| CN108562616A (en) | A kind of outer detection method of natural gas line | |
| Dzhala et al. | Determination of components of transient resistance of underground pipeline | |
| Faraj et al. | Investigate of the effect of width defect on eddy current testing signals under different materials | |
| CN108680607A (en) | Pipeline crack corrosion monitoring process based on multi-communication potential drop | |
| WO2009157773A1 (en) | Method and system for determination of coating performance | |
| US4982163A (en) | Method and a device for the determination of the condition of the insulation of an object coated with an electric insulation | |
| Zheng et al. | Numerical simulation of a U-shaped ACFM inducer | |
| CN104995489A (en) | Method for operating a magnetic-inductive flow meter | |
| US11630081B2 (en) | Method for non-destructively examining an anode of an aluminium electrolysis cell | |
| RU2708682C1 (en) | Contact sensor of specific electric conductivity of liquid | |
| KR100508877B1 (en) | method for detecting the coating defect and corrosion points of the pipelines in soil using the electrochemical impedance spectroscopy | |
| CN109085407B (en) | Method for measuring electromagnetic influence of overhead transmission line on buried metal pipeline | |
| Jarvis et al. | Current deflection NDE for pipeline inspection and monitoring | |
| CN105548281B (en) | A kind of nondestructive detection system and method based on Kelvin effect resistance excess noise | |
| Ouadah et al. | Pipelines corrosion due to the electromagnetic pollution caused by the high voltage power lines | |
| Gan et al. | New feature for evaluation of subsurface defects via multi-frequency alternating current field signature method | |
| RU2157424C1 (en) | Cathode protection system and diagnostics of pipe-lines | |
| CN105629134B (en) | A kind of method that state is insulated between detection dissimilar metal |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |