EP4680955A1 - Procédé d'inspection d'élément métallique de béton précontraint d'une canalisation, et dispositif d'inspection - Google Patents

Procédé d'inspection d'élément métallique de béton précontraint d'une canalisation, et dispositif d'inspection

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Publication number
EP4680955A1
EP4680955A1 EP24712466.2A EP24712466A EP4680955A1 EP 4680955 A1 EP4680955 A1 EP 4680955A1 EP 24712466 A EP24712466 A EP 24712466A EP 4680955 A1 EP4680955 A1 EP 4680955A1
Authority
EP
European Patent Office
Prior art keywords
magnetic field
inspection device
excitation
pipeline
alternating
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.)
Pending
Application number
EP24712466.2A
Other languages
German (de)
English (en)
Inventor
Andrey Danilov
Patrik Rosen
Sergio PLASCENCIA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rosenxt Holding AG
Original Assignee
Rosenxt Holding AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Rosenxt Holding AG filed Critical Rosenxt Holding AG
Publication of EP4680955A1 publication Critical patent/EP4680955A1/fr
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws

Definitions

  • the present invention relates to a method for inspecting a metallic concrete tensioning element, for example a concrete tensioning wire, which is embedded in a spiral shape in a water-carrying pipeline, and thus in its concrete.
  • the invention also relates to an inspection device with which such a method can be carried out.
  • Concrete pipelines are often used to transport water, which have a cylindrical metal layer or a metal cylinder that is coated with concrete on the inside and outside.
  • the concrete is reinforced by one or more concrete tensioning elements that are designed as wire or wire strands.
  • Such concrete tensioning elements absorb the tensile stresses acting in the concrete and significantly increase the strength of the pipeline.
  • the distance between the excitation unit and the sensor of two to three pipe diameters means that the device's ability to pass through the pipeline is very limited.
  • EP 2458376 A2 it is also known to use two sensors close to the wall to measure a resulting magnetic field that varies due to a defect. This type of measurement is also very susceptible to interference.
  • an associated inspection device cannot be used due to the sensors being arranged close to the wall in pipes with so-called butterfly valves, which are often used.
  • the object of the present invention is to increase the accuracy of investigations into the integrity of concrete prestressing elements and to create a corresponding device for this purpose. The object is achieved by a method according to claim 1 and by an inspection device according to claim 16.
  • a first alternating magnetic field is generated with at least one first excitation unit of an inspection device, preferably comprising a first excitation coil.
  • a second alternating magnetic field is generated with at least one second excitation unit of the inspection device, which is spaced apart from the first excitation unit and preferably comprises a second excitation coil, wherein the first and second magnetic fields have opposite directions.
  • At least one position between the first and the second excitation unit is used to record measurement data based on the resulting magnetic field using at least one magnetic field sensor of the inspection device, which is evaluated with regard to the size and/or phase of the resulting magnetic field.
  • this data produces a characteristic signal in the event of a defect in the concrete tensioning element, which is used to determine whether the defect is present.
  • the excitation units are spaced apart from one another in the longitudinal direction of the inspection device.
  • Concrete tensioning elements are cord-shaped concrete tensioning elements in the form of wire or strands made of several wires.
  • the two opposing alternating fields are so opposite that they cancel each other out, at least in part.
  • the resulting magnetic field is the result of the superposition of the direct alternating fields acting directly from the excitation units in the area of the magnetic field sensor and the fields induced by metallic parts of the pipeline. The latter are created in particular due to interactions in the metal cylinder, if present, and in the concrete tensioning element.
  • the invention is based on the finding that currents are generated in the circumferential direction in the concrete tensioning element, thus in turn generating an alternating magnetic field.
  • the sensor signal contains three components.
  • a first component ⁇ ⁇ ⁇ results from the alternating magnetic fields generated directly by the excitation units.
  • a further component ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ results from eddy currents induced in the cylindrical metal of the pipeline.
  • the individual signal components result from different physical effects.
  • the amplitudes and phase values in relation to the phase of the alternating magnetic field generated by the excitation units vary for ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ and ⁇ ⁇ ⁇ ⁇ ⁇ depending on the distance of the sensor from the excitation unit and the excitation frequency of the generated magnetic field.
  • the phase of ⁇ ⁇ ⁇ depends in particular on the thickness of the metallic layer and the excitation frequency, while the amplitude of ⁇ ⁇ ⁇ also varies with the excitation frequency and the distance between the magnetic field sensor and the excitation unit.
  • the phase and amplitude of ⁇ ⁇ ⁇ ⁇ ⁇ depend significantly more on the excitation frequency than ⁇ ⁇ ⁇ ⁇ ⁇ . If there is no metal cylinder, ⁇ ⁇ ⁇ is zero.
  • ⁇ ⁇ ⁇ The different dependencies on the excitation frequency and the distance between the magnetic field sensor and the excitation unit enable the phase to be adjusted using the measurement setup and the frequency to be selected specifically for the pipe wall.
  • the optimal setup must be determined for each pipe by means of calibration in combination with the design of the excitation units, which in particular have coils, their excitation frequency and the distance between the excitation units and the magnetic field sensor(s). For this purpose, a series of measurements can be carried out in advance or a database with calibration data can be used.
  • ⁇ ⁇ can be easily determined if ⁇ ⁇ ⁇ is aligned orthogonally to ⁇ ⁇ ⁇ ⁇ ⁇ .
  • ⁇ ⁇ ⁇ ⁇ ⁇ and ⁇ ⁇ ⁇ ⁇ ⁇ should run as oppositely as possible, although good measurement results can already be achieved at angles of around 50°. It also follows from the above geometric relationship that the dependence of the phase change on the amplitude contribution ⁇ ⁇ becomes greater with lower ⁇ ⁇ . By using two excitation units that generate opposing alternating magnetic fields, ⁇ ⁇ is now reduced.
  • the method according to the invention when carrying out the method according to the invention or using a setup according to the invention, sensitivity improvements in the measurement by a factor of 10 to 40 result compared to the state of the art, taking into account that the use of two excitation units results in further advantages in detecting the defect.
  • the defect signal is given a special shape by the use of two coils, which makes its detection considerably easier.
  • the method according to the invention and the structure of an inspection device described below allow the measurement setup to be significantly shortened by at least a factor of two in some places. At the same time, the method is significantly more sensitive in terms of detecting break points.
  • the magnetic fields generated are opposite to one another when the associated excitation units are designed in such a way that the vectors of the magnetic field strength or flux density describing the alternating magnetic fields are opposite to one another or at least approximately opposite to one another (angular deviation in particular ⁇ 30°, preferably less than 10°, from a direct alignment in the opposite direction).
  • the alternating magnetic fields also called “magnetic fields” are generated in an axial direction and in exact opposition to one another. With regard to the generation of the opposing magnetic fields by the excitation units, these should ideally differ in phase by 180°.
  • Deviations of no more than 20° are also still suitable for enabling defects in the concrete prestressing element.
  • Coils are used in particular to generate the alternating electromagnetic fields. These are preferably arranged axially, ie in the longitudinal direction of an inspection device with windings guided symmetrically around its longitudinal axis or longitudinal center axis. The coil axis is then located in particular in the longitudinal center axis of the inspection device. Hall sensors or GMR sensors can be used in particular as magnetic field sensors. If the magnetic field sensor has a coil, its coil axis is preferably parallel and in particular congruent with the longitudinal center axis.
  • An inspection device for inspecting a metallic concrete tensioning element of a pipeline, in particular a water-carrying pipeline, has at least one first excitation unit, preferably comprising a first excitation coil, for generating a first alternating magnetic field, and at least one second excitation unit, spaced apart from the first excitation unit and preferably comprising a second excitation coil, for generating a second alternating magnetic field, wherein the excitation units are designed and controllable in such a way that the first and second magnetic fields have opposite directions.
  • the excitation units are spaced apart from one another in the longitudinal direction of the inspection device, which during operation corresponds approximately to a longitudinal axis of the pipeline to be inspected.
  • the inspection device according to the invention has at least one magnetic field sensor arranged between the first and second excitation units for recording a resulting magnetic field. It is understood that in such an inspection device, the is designed to be suitable for use in pipelines and has the appropriate electrics or electronics for this purpose. The magnetic field sensor is also linked to this electronics to record the data.
  • the inspection device according to the invention is equipped with other conventional means for autonomous travel in a pipeline, which can include energy storage means, data storage means and in particular also means for determining the position of the device in a pipeline.
  • the device is designed in particular as an autonomous inspection device in such a way that it can travel through a pipeline without a cable connection for energy and/or data communication and thus without being tied down.
  • the excitation units advantageously generate magnetic fields whose amplitudes do not differ by more than 10%, preferably by no more than 5%. Amplitudes that are as equal as possible optimally cancel each other out. It can therefore be advantageous according to the invention if the magnetic fields generated differ slightly by no more than 10% and preferably no more than 5%, but do not have the same amplitude. This is based on the knowledge that the smaller the difference between the resulting magnetic fields generated by the two excitation units, the better the disturbance caused by a defect in the concrete prestressing element can be measured, but at the same time the phase signal becomes undefined if the values are too small.
  • the frequency and distance can be selected for each pipe, for which purpose a corresponding calibration database can be used.
  • the alternating magnetic fields with opposite directions are largely axially aligned, i.e. generated in the axial direction, for example by windings of a coil running around a longitudinal center axis of the inspection device, which can also have a magnetic core accommodating the longitudinal center axis or the longitudinal center axis.
  • Such a setup is particularly advantageous for spirally arranged concrete tensioning elements, which can be viewed as a structure running in the axial direction, since the coils can be built sufficiently large and in particular can have a diameter of up to 75% of the diameter of the pipeline in question.
  • the measurement data recorded by the magnetic field sensor are either stored directly in the inspection device, for example in the form of a pig, and further processed there.
  • the data can be read out of the inspection device after completion of a measurement run and evaluated in a standard computer device.
  • Such an electronic data processing device has, among other things, the usual means such as a processor, transient and permanent memory, input and output interfaces and means for controlling the program sequences for evaluating the data.
  • the IT device is designed to evaluate the measurement data in terms of amplitude and phase.
  • the IT device can also be part of the inspection device, so that the detected defects and any associated raw data can be read out.
  • the inspection device can have means for determining the position and location of the inspection device.
  • the location and position data for example from gyros or an odometer, can be linked to the measurement data from the magnetic field sensor in order to identify the position of a defect.
  • a defect in the concrete tensioning element is detected on the basis of two successive and in particular different extremes of the amplitude and/or the phase of the resulting field.
  • Such a vibration-like signal shape allows easier detection of the fracture in the presence of noise and is also easier to detect in the measurement data than the signals generated in the prior art.
  • vibration-like signals can be detected using a wavelet analysis based on the Haar wavelet.
  • a wavelet analysis allows a possible elongation of the signal shape to be taken into account, for example due to several successive disturbances or fractures of the concrete prestressing element.
  • the received data is analyzed for wavelets that occur when the inspection device moves past the fracture point of the concrete prestressing element, whereby a wavelet is usually considered to be a wave-like oscillation of a signal, i.e. the assumption of a minimum with a direct transition to a maximum or vice versa.
  • the measurement data are advantageously recorded by the magnetic field sensor centrally between the excitation units, whereby central means, for example, in a side view of the excitation units and the distance that can then be recognized due to the spacing of the excitation units in the longitudinal direction of the inspection device.
  • This location provides the optimal conditions for detecting a measurement signal generated due to a disturbance.
  • it can make sense to place the magnetic field sensor off-center between the excitation units.
  • a central arrangement means an arrangement in a middle area between the excitation units and in particular an arrangement that includes the exact middle between the excitation units.
  • Magnetic parts of the inspection device and/or inaccuracies in manufacturing can strengthen or weaken one of the excitation units, resulting in uneven winding of the excitation unit.
  • This imbalance can be corrected at least partially by shifting the sensor position of the magnetic field sensor in the longitudinal direction.
  • the inspection device moves autonomously through the pipeline while the measurement data is being recorded. Due to the fact that this is not tied to cables, large distances can be covered. Since with a corresponding setup of the inspection device according to the invention, energy consumption can also be optimized due to the signal being much more easily recognizable than in the prior art, large distances of more than one kilometer of pipeline can also be inspected without being tied down.
  • the movement of the inspection device is particularly passive due to the flow in the pipeline, in particular the water.
  • the excitation units are arranged one behind the other in the longitudinal direction of the inspection device and in particular symmetrically around the longitudinal center axis, whereby an alternating magnetic field is generated across the entire circumference. They can be controlled in parallel via the same electronics or can have their own control units that are synchronized with one another.
  • the invention uses the knowledge that, depending on the frequency for generating the first and second alternating magnetic fields and the distance between the two excitation units at the location of the measurement data acquisition, a phase difference can be created between the signal component determined from the direct signal, that of any cylinder present, and the signal component resulting from the at least one concrete prestressing element.
  • the frequency sensibly the phase and/or amplitude of the measurement signal is influenced mainly by the signal resulting from the concrete prestressing element. Measurements at different frequencies therefore have a different sensitivity for different structural elements in the pipeline wall. Since the measurement can be carried out at different frequencies at the same time, it is advantageous in a further embodiment of the invention to use more than two frequencies for the measurement.
  • a pulse with a broader frequency spectrum can then be used as the excitation signal.
  • the resulting signal can be cleaned up in particular of structural influences on the pipeline. If signal changes occur simultaneously at different frequencies, one of which is more sensitive to fractures than the other, this is an indication of structural changes in the pipeline. For example, for pipelines with metal cylinders with a wall thickness of 2 mm, frequencies of 20 Hz and 200 Hz can be used. measured, whereby fractures of the concrete tensioning element can essentially only be detected at 20 Hz due to the skin effect in the metal cylinder. If changes in the signal occur simultaneously at both 20 Hz and 200 Hz, there is a structural change in the pipeline that is not due to a fracture of the concrete tensioning element.
  • any structural changes can be identified based on their characteristic signals in the resulting magnetic field.
  • the signal shapes found in this way can be stored in a database for improved detection of corresponding structural changes or structures and used for future structure detection.
  • coils that are wound symmetrically around the longitudinal center axis are used as excitation units.
  • these can preferably be operated in a range of 10 to 800 Hz and thus at low frequencies.
  • the maximum wall thickness is 1 mm.
  • a frequency of less than 200 Hz is used.
  • the alternating magnetic fields are preferably generated with frequencies greater than 100 Hz, preferably greater than 1000 Hz.
  • An upper limit for the excitation frequency is in particular 1000 kHz.
  • the alternating magnetic fields are excited continuously, both when using one or more frequencies.
  • the alternating magnetic fields can be excited with frequency bursts, so that sufficient information about the resulting magnetic field can be collected even with short measurement recordings.
  • these can be generated simultaneously and/or one after the other.
  • a lock-in amplifier is preferably used on the electronics side to evaluate the frequency-specific signals of the resulting magnetic field.
  • the frequencies of the alternating magnetic fields for pipelines with metal cylinders with a wall thickness of 2 mm are in the range of 20 to 50 Hz.
  • this additional frequency is preferably between 100 Hz and 800 Hz. Due to the alternating magnetic fields generated in the axial direction, the resulting magnetic field is particularly not sensitive to a lift-off of a magnetic field sensor from a wall of the pipeline. Therefore, the resulting magnetic field is measured in particular in the middle of the pipeline, which means that a magnetic field sensor can be built sufficiently large and significantly larger than in the state of the art.
  • a measurement in the middle of the pipeline corresponds to an arrangement of a magnetic field sensor, for example in Form of a coil, symmetrical around a longitudinal center axis of the inspection device.
  • the axial arrangement of the sensor allows the use of a significantly larger sensor design. Accordingly, the diameter of the sensor or sensor coil can be significantly increased. This enables the compensation of fluctuations due to inhomogeneities in the pipe wall or significantly reduces these disruptive influences as well as any speed-related interference components of the measurement signal.
  • the resulting magnetic field can be measured with another sensor located outside the center of the pipe. This can be positioned close to the wall to obtain additional information about the integrity of the pipe.
  • axial and radial components can be measured. The recording of two or three components of the resulting magnetic field can contain combined information about the integrity of the pipe.
  • the resulting magnetic field is recorded with several magnetic field sensors that are arranged one behind the other in the longitudinal direction of the inspection device and in particular axially on the inspection device, and thus at several positions located one behind the other.
  • This not only enables the measurement of the amplitude and phase of the magnetic field, but also its variation. along the pipeline axis.
  • the data used can be used, for example, to determine first or multiple derivatives of the amplitude and phase function.
  • the combined evaluation of the discovered features for the amplitude and phase function and their variation along the longitudinal axis makes it possible to reduce the number of possible incorrect determinations due to inhomogeneities in the pipeline.
  • the data of a magnetic field sensor can be evaluated in which the at least approximate balance between the alternating fields generated by the excitation units is best suited for the evaluation. Since the balance between the excitation units or the alternating magnetic fields generated by them can change due to a variety of influences on the pipeline or the inspection device, it can be advantageous to switch to a sensor and its data other than the one located exactly in the middle between the excitation units.
  • the magnetic field sensor or sensors are arranged in a region arranged centrally between the excitation units, which corresponds to 50% of the distance between the excitation units. Accordingly, the measurement data are recorded in this region in particular.
  • the magnetic field sensor or sensors of an inspection device according to the invention are thus arranged between the sensors spaced apart from one another in the longitudinal direction, with the inspection device in particular being designed to move in a Pipeline of diameter D and the distance between the excitation units is ⁇ 2*D and in particular ⁇ 1.5*D.
  • the distance is also advantageous, particularly in the case of inspection devices that can be driven passively using corresponding cups or disks, ⁇ 2*diametercup/disk and in particular ⁇ 1.5*diametercup/disk.
  • magnetic field sensors can be arranged centrally in the longitudinal direction and correspondingly receiving a central longitudinal center axis of the inspection device
  • magnetic field sensors can also be arranged offset in the longitudinal direction and/or in the radial direction between the excitation units.
  • the use of several sensors offset from one another in the radial direction to measure the resulting magnetic field is particularly advantageous against the background of the knowledge that, depending on the structure of the wall of the pipeline, the position of a fracture point of the concrete tensioning element in the circumferential direction can influence the axial symmetry of the magnetic field.
  • the concrete tensioning element is wound in the form of a wire spirally around the metallic, cylindrical core of the pipeline, with a distance between the windings of several cm and the associated continuous reductions in the currents occurring, asymmetrical components of the magnetic field arise in the vicinity of the defect.
  • the occurrence and change of such asymmetrical components can be detected by appropriately radially offset sensors.
  • the alternating fields generated by the excitation units are weakened by means of two shielding elements in the direction of the at least one magnetic field sensor.
  • the shielding elements are arranged in particular in the form of disks, once in front of and once behind the magnetic field sensor(s) in the direction of the respective excitation unit.
  • the shielding element is made in particular of a conductive or magnetic material.
  • the sensitivity of the measurement data can be increased and, in addition, the distance between the excitation units can be reduced accordingly, which in turn improves the resolution of the measurements.
  • the shielding elements can impair the device's ability to pass through pipes due to their weight and the comparatively large diameter required.
  • flexible shielding elements are advantageous to a certain extent for improving the ability to pass through bends, for example in the form of shielding elements that can be stretched out or retracted like an umbrella.
  • alternating magnetic fields of different frequencies are generated one after the other and/or simultaneously and the measurement data resulting from this are recorded by the at least one magnetic field sensor.
  • This is based on the knowledge that the balance between the alternating magnetic fields generated can be changed, for example, by a movement of the inspection device or by changes in the in the pipeline wall.
  • Such disturbances in the equilibrium result in changes in the amplitude and phase of the signal in the measurement data, which can then be misinterpreted as a fracture signal of the concrete tensioning element.
  • Such misinterpretations can be detected by measuring at different excitation frequencies and excluded internally.
  • Changes due to fractures in the concrete tensioning element are significantly different in signal form at different frequencies than changes due, for example, to disturbances in the equilibrium caused by the tool movement or the wall structure. Measurements at different frequencies lead to different error signals at the same defect location. This gives a defect a specific pattern that is made up of signals at different frequencies and is thus different from noise. As part of the invention, it was found that a combined measurement at different frequencies not only enables better detection of the defect, but also a better estimate of the number of fractures. When using different frequencies, a main frequency can be selected as the frequency that, based on any calibration data, produces the strongest interference signal in the event of a fracture of the concrete prestressing element, for example the frequency that produces the strongest phase change.
  • a further frequency can then be selected that is lower than the main frequency, for example a frequency that mainly results in an amplitude difference in the measurement signal.
  • at least one second frequency can also be selected to be higher than the main frequency in order to amplify skin effects of any metal cylinder that may be present and thus exclude interaction with the concrete prestressing element.
  • the same excitation units or several pairs of excitation units that operate at different frequencies can be used on the same inspection device. Of course, it is also possible to combine inspection runs that have taken place one after the other at different frequencies.
  • an interference signal is advantageously reduced by subtracting the scaled amplitude values from the phase values.
  • associated optimal scaling factors for the amplitude signal as well as any parameters of the measuring system such as the excitation frequency can be determined during a calibration process. This is again based on the knowledge that the interference signal resulting from a fracture of the concrete prestressing element has different amplitudes and phases.
  • a setup is advantageous in which, in addition to a single Sensor that is designed symmetrically to the longitudinal center axis, for example accommodating it, additionally has a plurality of two, three, four or more sensors evenly distributed over the circumference.
  • the sensors distributed in the circumferential direction around the longitudinal center axis can also partially intersect it or can at least partially cover each other when viewed in the longitudinal direction.
  • the use of an inspection device in which the distance between the excitation units is variably adjustable is particularly advantageous. This allows the inspection device to be adapted to different pipelines.
  • the adaptability arises, for example, due to an exchangeable central body, due to exchangeable modules of the central body on which the sensors are or can be attached, or also due to a corresponding fastening system, for example based on a thread or a plug-in system, via which the distance between the excitation units can be adjusted in the longitudinal direction. Further advantages and details of the invention can be found in the following description of the figures.
  • Fig.1 shows an object according to the invention in a perspective view
  • Fig.2 shows the object according to Fig.1 in a side view
  • Fig.3 shows the object according to Fig.1 in an operating position in a water-carrying pipeline
  • Fig.4 shows an illustration of signal generation
  • Fig.5 shows the proportions of the measurement data when there is a defect in the concrete prestressing element
  • Fig.6 shows a sensor setup with resolution of the position in the circumferential direction
  • Fig.7 shows a further illustration of the sensor setup for resolution in the circumferential direction
  • Fig.8 shows the phase values at different frequencies, phases and amplitude data in the area of a defect and in the presence of interference.
  • Fig.9 shows an illustration of phase and amplitude functions in the vicinity of a defect and in the presence of significant interference
  • Fig.10 shows a further embodiment according to the invention
  • Fig.11 shows the object according to Fig.10 in a vertical longitudinal section
  • Fig.12 to Fig.14 show various measurement results for a number of tests.
  • Individual technical features of the exemplary embodiments described below can also be combined with previously described exemplary embodiments and the features of one of the independent claims and any further claims to form objects according to the invention. Where appropriate, elements that are at least partially functionally equivalent are provided with identical reference numbers.
  • An inspection device 2 has a first excitation unit 4 with a first excitation unit 4 formed concentrically to the longitudinal center axis 24 with a first excitation coil 6 running symmetrically around a longitudinal center axis of the inspection device 2.
  • a second excitation unit 8 is arranged offset in the longitudinal direction of the inspection device and has a second excitation coil 10 that is also arranged symmetrically around the longitudinal center axis 24 of the device 2 (Fig.1).
  • the two excitation units 4, 8 are controlled and operated by electronics in the central body 22 of the inspection device 2, indicated by a dashed box 25.
  • the excitation coils 6, 10 generate alternating magnetic fields that are opposite one another in the axial direction, ie in the direction of the longitudinal center axis 24.
  • a magnetic field sensor 12 with a coil 14 that also runs symmetrically around the longitudinal center axis 24 and whose diameter in the direction the longitudinal center axis 24 is 75% to 100% of the diameter of the excitation coils 6 or 10.
  • Shielding elements 20 are arranged close to the excitation units 4, 8. As in other embodiments, these can generally be placed directly on the respective excitation unit, so that any inductive field resulting from an influence of the shielding elements is weakened as much as possible due to the distance then existing to the magnetic field sensor.
  • the inspection device 2 is equipped with a series of centering elements 18 in the form of spring-loaded arms with rollers at the ends, which center the device 2 as far as possible in the middle of the pipeline as it travels through it.
  • the inspection device 2 can be coupled to other functional components of an inspection pig via connection areas 16 and, for example, pulled through a pipeline by the latter.
  • the inspection device itself can also be designed as a pig with corresponding cups or disks for passive propulsion in a pipeline.
  • the water-carrying pipeline 26 to be inspected (Fig. 3) has an interior that is almost completely filled by the inspection device 2 in the longitudinal direction, ie in the direction of the longitudinal center axis 24.
  • the pipeline 26 comprises a metallic, cylindrical layer in the form of a metal cylinder 28, which is covered on the inside by an inner concrete layer 30 and on the outside by an outer concrete layer 32.
  • a concrete tensioning element 34 in the form of a concrete tensioning wire is present in the outer concrete layer 32.
  • This concrete tensioning wire is arranged close to the cylindrical metal layer 28, but does not touch it. Nevertheless, due to the small distance between the metal cylinder 28 and the concrete tensioning element 34, a sufficient current flow for the measurement is possible.
  • connection points of the concrete tensioning wire can still be present at the ends of the respective pipeline segment of the pipeline 26.
  • a characteristic signal is produced as shown in Fig.4 with two consecutive extremes.
  • the current flow induces a magnetic field which is detected by the magnetic sensor.
  • the opposing alternating magnetic fields compensate for the effects at the location of the magnetic field sensor. Due to a defect 36, no current flow is possible in this area and thus no or a different electromagnetic signal is generated, so that the magnetic fields generated by the currents in the concrete prestressing element do not compensate for each other at the level of the magnetic field sensor, and therefore at its longitudinal position.
  • This imbalance in the resulting magnetic field indicated primarily by a current 40, is measured at the location of the magnetic field sensor. The result is a positive extremum, marked by point B. This signal weakens again as the pipe moves along. At the moment when the defect is positioned at the same height as the magnetic field sensor 12, symmetry is again established and a zero crossing occurs at point C.
  • the signal resulting from the defect 36 and the other resulting signals due to the two generated and opposing magnetic fields differ in amplitude and phase (Fig. 5).
  • S' and S'' denote the signals induced by the first excitation unit 4 and by the second excitation unit 8.
  • the index "i” denotes the sum of the alternating fields insensitive to the defect, induced and directed in opposite directions.
  • the index "s” marks the signal components that are measured at the location of the sensor due to the interaction of the generated alternating magnetic fields with the concrete prestressing element.
  • the component ⁇ ⁇ ⁇ is negligible and is therefore not shown, since the defect prevents the current from spreading through the concrete prestressing element. Furthermore, ⁇ ⁇ ⁇ is slightly smaller than ⁇ ⁇ ⁇ , which is advantageous for the phase relationship.
  • the excitation frequency is selected so that the phase difference between the vectors Si and Ss is close to 90°. According to the present configuration, the component ⁇ ⁇ ⁇ is not compensated so that a corresponding defect or an associated phase angle can be easily derived from the measurement data.
  • a possible sensor setup of the magnetic field sensors for determining the circumferential position of a defect is shown schematically in Fig.6.
  • a plurality of five magnetic field sensors 12 are located between the excitation units 4 and 8.
  • the outer circumference of the respective coils of the magnetic field sensors 12 is shown, which are shown schematically in Fig.7 viewed in the longitudinal direction.
  • the middle coil is used to determine the defect position in the axial direction, i.e. in the direction of the longitudinal center axis.
  • the analysis of the relative signal changes in the four other coils or magnetic field sensors 12 enables the position in the circumferential direction to be determined. For example, a comparison of the signals between the upper and lower magnetic field sensors 12 can be used to limit the position of the defect to the upper or lower half of the pipeline.
  • Fig.8 illustrates the resulting different phase values of the measurement signal resulting from the resulting magnetic field at different excitation frequencies and in the presence of a strong interference signal.
  • the solid lines in Fig.8a, 8b, 8c show the signal for a concrete prestressing element that is defective in the test setup.
  • the dashed lines show the phase values for an intact concrete prestressing element.
  • the alternating magnetic fields were determined at a frequency of 50 Hz, in the figure according to Fig.8b at a frequency of 200 Hz.
  • Fig.8c shows the differences between the measured values at 50 Hz and 200 Hz.
  • Fig. 9 shows examples of the phase-amplitude functions in the vicinity of a defect and in the case of significant interference.
  • the solid curve shows the phase values and the dashed curve shows the amplitude values. The curves again apply to a setup of a pipeline with a diameter of 440 mm.
  • the increase in the phase value in the middle of the recorded signal corresponds to the defect.
  • the amplitude function is scaled, whereby the scaling coefficient was chosen so that after scaling on the intact pipe sections, the amplitudes of the phase-amplitude functions are the same or at least similar. Outside the defect area, the amplitude and phase function correlate with each other so that a scaling coefficient can be obtained from this.
  • This correlation can be used to reduce the influence of interference, whereby the correlation can vary, for example, depending on the pipe wall, the excitation frequency and the distance between the excitation coils.
  • a further embodiment of an inspection device according to the invention can be used in particular for pipelines carrying water or other media that are provided with butterfly valves, wherein the inspection device 2 has a central body 22 that has a plurality of support elements 42 that are arranged in an articulated and/or fixed manner on the central body 22 (Fig. 10). If the support elements 42 are not arranged in an articulated manner or do not have bendable sections, the support elements 42 are designed to be at least sufficiently flexible so that when they hit a butterfly valve, the effective cross section of the inspection device 2 is reduced to less than half the diameter of the pipeline.
  • a propulsion element 44 is arranged, which is clamped in the medium and causes propulsion and entrainment of the device due to the pressure exerted by the medium.
  • This propulsion element 44 also has a plurality of segments 48 spanned by tension rods 46, which can also be bent due to the articulated arrangement of the tension rods 46 on the central body 22, which also reduces the effective cross-section of the inspection device 2 (viewed in the longitudinal direction of the same).
  • Curves 50 can be arranged at the end of the support elements, which touch the inside of the pipeline to be inspected as gently as possible.
  • odometers 52 can be arranged at the end of the individual support elements 42.
  • a first excitation coil 6 of a first excitation unit 4 is arranged, wound centrally around the longitudinal axis 24. This is located in relation to the longitudinal axis or longitudinal center axis 24 at the level of the front support elements.
  • second excitation coil 10 is arranged at the rear end of the inspection device 2, approximately at the level of the rear support elements 42.
  • An outer wall 54 of the central body 22 is preferably made of a non-magnetizable material, in particular of a plastic composite material.
  • a sensor coil 14 of a magnetic field sensor 12 is arranged centrally between the two excitation coils 6 and 10, again symmetrically around the longitudinal axis 24. This records measurement data based on the resulting magnetic field, which is evaluated in terms of size and/or phase.
  • the dashed line in Figures 12 to 14 comes from a setup with three wire breaks in the concrete prestressing element, the solid line from a setup with six wire breaks and the dash-dotted line from a setup with nine wire breaks.
  • the wire breaks follow one another immediately.
  • the recorded amplitude of the signal (Fig. 14) has recognizable extrema in the area of the breaks.
  • Fig. 12 shows the imaginary part of the evaluated signal, which, like the real part of the evaluated signal (Fig. 13), has the previously described form with a further extrema following a first extrema.

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Abstract

L'invention concerne un procédé d'inspection d'un élément métallique de béton précontraint d'une canalisation, en particulier d'une canalisation d'eau, le procédé comprenant les étapes suivantes : la génération d'un premier champ magnétique alternatif au moyen d'au moins une première unité d'excitation d'un dispositif d'inspection, cette unité d'excitation comprenant de préférence une première bobine d'excitation, et la génération d'un second champ magnétique alternatif au moyen d'au moins une seconde unité d'excitation du dispositif d'inspection, cette seconde unité d'excitation étant distante de la première unité d'excitation et comprenant de préférence une seconde bobine d'excitation, ayant des directions opposées ; et pendant le déplacement du dispositif d'inspection le long de l'élément de béton précontrainte, l'enregistrement de données mesurées sur la base du champ magnétique résultant à au moins une position entre les première et seconde unités d'excitation au moyen d'au moins un capteur de champ magnétique du dispositif d'inspection, lequel capteur comprenant de préférence une bobine de capteur ; et l'analyse des données mesurées relatives à l'amplitude et/ou à la phase du champ magnétique résultant. L'invention concerne également un dispositif d'inspection permettant d'inspecter un élément métallique de béton précontraint d'une canalisation, en particulier d'une canalisation d'eau.
EP24712466.2A 2023-03-15 2024-03-15 Procédé d'inspection d'élément métallique de béton précontraint d'une canalisation, et dispositif d'inspection Pending EP4680955A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
BE20235189A BE1031434B1 (de) 2023-03-15 2023-03-15 Verfahren zur Inspektion eines metallischen Betonspannelementes einer Rohrleitung sowie Inspektionsvorrichtung
PCT/EP2024/057059 WO2024189226A1 (fr) 2023-03-15 2024-03-15 Procédé d'inspection d'élément métallique de béton précontraint d'une canalisation, et dispositif d'inspection

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EP4680955A1 true EP4680955A1 (fr) 2026-01-21

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EP (1) EP4680955A1 (fr)
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CN119395130B (zh) * 2024-12-31 2025-04-18 联桥网云信息科技（长沙）有限公司 一种快速pccp管道断丝电磁无损检测方法
CN119738468B (zh) * 2025-03-05 2025-05-23 中国石油大学(华东) 一种铝合金结构表面分叉裂纹检测装置及其三维表征方法
CN121253001B (zh) * 2025-12-04 2026-02-17 中国石油大学(华东) 基于交流电磁场的管道轴向区域应力定量评估系统及方法

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Publication number Priority date Publication date Assignee Title
US6127823A (en) 1997-10-08 2000-10-03 Atherton; David L. Electromagnetic method for non-destructive testing of prestressed concrete pipes for broken prestressing wires
CA2361813A1 (fr) 2001-01-29 2002-07-29 Peter O. Paulson Analyse electromagnetique a basse frequence de fils de mise en tension du beton precontraint
US7002340B2 (en) * 2003-03-25 2006-02-21 Atherton David L Method for inspecting prestressed concrete pressure pipes based on remote field eddy current/transformer coupling and use of non-coaxial coils
US20130024135A1 (en) * 2011-07-22 2013-01-24 Blum Dieter W Method And Apparatus For Ferromagnetic Cable Inspection
EP3149519A4 (fr) * 2014-07-12 2017-12-20 Halliburton Energy Services, Inc. Utilisation d'un réseau de capteurs entre deux émetteurs dans un environnement de diagraphie à courant de foucault
CN114894884B (zh) * 2022-04-02 2025-12-23 中国水利水电科学研究院 一种基于双激励线圈的pccp断丝检测系统及方法

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