WO2017017671A1

WO2017017671A1 - A wide bandwidth guidedwave (gw) probe for tube and pipe inspection system

Info

Publication number: WO2017017671A1
Application number: PCT/IL2016/050791
Authority: WO
Inventors: Eyal Conforti; Adam Baer; Dov Furman; Asaf EILAM
Original assignee: Acousticeye Ltd.
Priority date: 2015-07-26
Filing date: 2016-07-20
Publication date: 2017-02-02

Abstract

The present disclosure is in the technical field of tube and pipe inspection relating to the field of non-destructive testing. Some embodiments of the present disclosure achieve large bandwidth by precise location of the transducers on the circumference of the tube.

Description

A WIDE BANDWIDTH GUIDEDWAVE (GW) PROBE FOR TUBE AND PIPE

INSPECTION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is related to US patent application number US 14/641,418 that claims priority to the United States provisional patent application serial number 61/950,158 filed on March 9, 2014 and is related to a Patent Cooperation Treaty application (PCT) application number PCT/IL2013/000054 that was filed in the Israeli Receiving Office on Jun. 10, 2013, the contents of each of these are incorporated herein by reference.

FIELD OF INVENTION:

[0002] The present disclosure relates to the field of non-destructive testing and more particularly, the present disclosure is in the technical field of tube and pipe inspection.

DESCRIPTION OF BACKGROUND ART

[0003] There are several techniques, presently in use, for conducting tube or pipe inspections. These techniques can be divided into two main groups: traversing and non -traversing. The non- traversing methods employ a probe, which can inspect only the portion of the tube in its immediate vicinity. In order to inspect an entire tube, a traversing probe can be used. The traversing probe can be tethered to a cable by which the probe is pushed all the way down from one end of the tube to the other and then pulled back. Traversing methods are slow, prone to wear and tear of the probe, and eventual failure. One example of a traversing inspection method is Eddy Current Testing, and related methods such as Remote Field Testing and Magnetic Flux Leakage testing. All these traversing methods are electromagnetic methods, having varying degrees of accuracy. Another example is the widely known as IRIS (Internal Rotating Inspection System), which is based on ultrasound. IRIS is based on use of a probe that scans the tube wall in a spiral manner using an ultrasound beam propagating in water. It is much slower than the electromagnetic methods and requires cleaning the tube wall down to the metal, which is an expensive process. Throughout this disclosure, the terms tube and pipe can be used interchangeably and the term tube can be used as representative term for both terms. [0004] Non-traversing methods are based on inserting a probe a relatively short distance into a tube under test, and then applying a physical method for inspecting the entire tube from this location. As a non-limiting example of such a method is Acoustic Pulse Reflectometry (APR). In the APR method, an acoustic signal (which could be, for example, but not limited to a pulse or a pseudo noise signal, swept sine, etc.) is propagated through the air inside the tube. Any changes in the cross sectional profile of the tube creates reflections, which propagate back toward to the probe where they can be converted to electronic signal, recorded and later analyzed. APR gives good results in detecting anomalies on the interior surface or cross-sectional profile of a tube, such as blockages, through holes, and circumferential changes in cross section of a tube. APR has several advantages: APR is fast, it can accurately assess blockages, and it is very sensitive to through-holes, for example. A reader who wishes to learn more about APR systems is invited to read US patent number 7,677,103, or US pre-granted publication number US2011- 0166808, or US patent 8,960,007.

[0005] An inspection method, which is known widely as the Guided-Wave (GW) method, is based on propagating mechanical waves within the tube wall itself. These waves can be, for example but not limited to, a torsional or longitudinal or flexural wave, and the excitation signal can be for example, but not limited to, a pulse or a pseudo noise signal, swept sine, etc. The torsional waves are marked with the letter 'T'; the longitudinal waves are marked with the letter 'L'; the flexural waves are marked with the letter 'F. Torsional waves are those in which particle displacement is in the circumferential direction, but the wave propagates down the axis of the tube. Longitudinal waves are those in which the particle displacement is in the axial direction, similarly to the direction of propagation of the wave. Particle displacement in torsional waves and longitudinal waves is independent of the azimuthal angle, therefore they are axisymmetric. Each type of the above waves are associated with:

• An infinite number of higher order axisymmetric modes,

depending on the number of nodal surfaces through the thickness of the tube wall, denoted T(0,m), m=l,2,3,... for torsional modes and L(0,m), m=l,2,3... for longitudinal modes; These modes have different cut-on frequencies and different dispersion curves. • A doubly infinite number of non-axisymmetric modes, denoted F_T(n,m) - where «=1,2,3... and m=l,2, ... . for flexural modes associated with torsional waves, and Fi(n,m) - where n=l,2,3... and m=\,2,3.... for flexural modes associated with longitudinal waves. These modes have different cut-on frequencies and different dispersion curves.

[0006] Different modes of excitation are well known to a person having ordinary skill in the art and will not be further described. A reader who wishes to learn more about mechanical waves is invited to read technical documents such as but not limited to the article "Flexural torsional guided wave mechanics and focusing in pipe", Journal of Pressure Vessel Technology Vol. 127, November 2005, pp. 471-478 written by Zongqi Sun, Li Zhang, Joseph L. Rose, for example.

[0007] Interfacing to the tube can be done from the interior of the tube by inserting a GW probe with one or more GW transducers in one of the openings of the tube. Alternatively the interfacing can be done from the external side of the tube by associating one or more GW transducers with the outer circumference of the tube.

[0008] The GW technique is sensitive to the degree of material loss. Any changes in the tube wall properties or dimensions will create a reflection, which can be recorded and analyzed. GW is fast and sensitive to flaws on both the outside and inside surfaces of the tube. Typically GW inspection systems have limited bandwidth (BW).

SUMMARY OF THE DISCLOSURE

[0009] In order to detect small defects, excitation of high frequencies having short wavelengths is needed. For example, mechanical waves with frequencies above 200 KHz may be needed in order to detect defects of length 2-3 millimeters. Further, in order to achieve high resolution and accurate sizing GW systems need to be broadband from low frequencies up to high frequencies, for example from 20 kHz up to 400 kHz. One of the challenges in obtaining large bandwidth is in exciting only the desired modes. However, the scattering caused by defects excites many unwanted modes. Therefore another challenge in achieving a large bandwidth is to filter out these unwanted modes. Some embodiments of the present disclosure achieve large bandwidth by precise location of the transducers on the circumference of the tube.

[0010] It is well known to a person with ordinary skill in the art that exciting mechanical waves in tubes is associated with excitation of a plurality of modes such as T, L and F_L and F_T, etc. Some of these modes interfere with the desired measurement and are therefore termed "unwanted modes". The unwanted modes may be generated in the inspected tube in addition to the wanted modes.

[0011] For example in order to use mode T(0,1) as the wanted mode, an embodiment of the system can transmit substantially the same signal simultaneously from all transducers on a ring of N transducers. The transducers can be distributed substantially evenly on the circumference. However, in such a case, a plurality of unwanted modes will be excited. The dominant unwanted modes interfering with the measurement may include: F_T(N,1); F_T(2N,1)... ; F_L(N,1); F_L(2N,1);... ; etc. . For example, using six transducers on each ring can excite unwanted modes F_T (6,1), F_L(6,1), F_T(12,1), F_L(12,1), T(0,2), F_L(6,2),... etc. If these modes are not suppressed relatively to the wanted signal, the interpretation of the measured signal will be ambiguous and defects may be masked. The cut-on frequency of these unwanted modes is generally monotonic with the index 'N' given above. In the present disclosure and the claims the terms measure, inspect, monitor, test, check, etc. can be used interchangeably.

[0012] We found that the amplitudes of the unwanted modes can be reduced considerably by bringing an absorbing material into contact with the surface of the tube. We have found that this has a much higher attenuating effect on the unwanted modes than on the wanted modes, therefore it leads to a large increase in Signal to Noise Ratio (SNR). One example is applying pliable material of approximately few centimeters in length, for example plasticene, to the external surface of the tube, over the zone of the GW probe. The range of the few centimeters can be 2-8 cm, for example. In some cases a ring of pliable material can be placed over 5 centimeters of the tube, in the region of the GW probe between the zone of guided-wave transducers. Wherein the zone of guided-wave transducers comprises two rings of transducers. An alternate embodiment may use a foam filled ring or a ring of rubber segments, fitted onto the tube, which in one embodiment would be inflatable in order to press it firmly to the tube wall. Such a ring of absorbing material could also be permanently affixed to the wall of the tube.

[0013] Alternatively, the absorbing material could be pressed against the inside wall of the tube. In one embodiment, the absorbing material could be affixed to a segment of the GW probe, which would come into action whenever a measurement is carried out. In such embodiment the absorbing material would be coupled to the tube wall either through its own elasticity or through a mechanism such as inflation with compressed air. The segment of the GW probe with the absorbing material could be located towards the front end of the probe, towards its rear end, or between rings of transducers.

[0014] The above-described deficiencies of GW methods, do not limit the scope of the inventive concepts of the present disclosure in any manner. The deficiencies are presented for illustration only.

[0015] In the following description, for purposes of explanation, numerous specific details are set forth to assist in the understanding of the various embodiments and aspects of inventions presented within this document. It will be apparent, however, to one skilled in the art that embodiments of the invention may be practiced without some or all of these specific details. In other instances, structures and devices are shown in block diagram form to avoid obscuring the flexibility and variability of the embodiments of the invention. References to numbers without subscripts or suffixes are understood to reference all instances of subscripts and suffixes corresponding to the referenced number. Moreover, the language used in this disclosure has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter, resort to the claims being necessary to determine such inventive subject matter.

[0016] Reference in the specification to "one embodiment" or to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment of the invention, and multiple references to "one embodiment" or "an embodiment" should not be understood as necessarily all referring to the same embodiment.

[0017] Although some of the following description is written in terms that relate to software or firmware, embodiments may implement the features and functionality described herein in software, firmware, or hardware as desired, including any combination of software, firmware, and hardware. In the following description, the words "unit," "element," "module" and "logical module" may be used interchangeably. Anything designated as a unit or module may be a standalone unit or a specialized or integrated module. A unit or a module may be modular or have modular aspects allowing it to be easily removed and replaced with another similar unit or module. Each unit or module may be any one of, or any combination of, software, hardware, and/or firmware, ultimately resulting in one or more processors programmed to execute the functionality ascribed to the unit or module. Additionally, multiple modules of the same or different types may be implemented by a single processor. Software of a logical module may be embodied on a computer readable medium such as a read/write hard disc, CDROM, Flash memory, ROM, or other memory or storage, etc. In order to execute a certain task a software program may be loaded to an appropriate processor as needed. In the present disclosure the terms task, method, process can be used interchangeably.

[0018] These and other aspects of the disclosure will be apparent in view of the attached figures and detailed description. The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure, and other features and advantages of the present disclosure will become apparent upon reading the following detailed description of the embodiments with the accompanying drawings and appended claims. [0019] Furthermore, although specific exemplary embodiments are described in detail to illustrate the inventive concepts to a person skilled in the art, such embodiments are susceptible to various modifications and alternative forms. Accordingly, the figures and written description are not intended to limit the scope of the inventive concepts in any manner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Some examples of embodiments of the present disclosure will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

[0021] FIG. 1 illustrates relevant elements in an axial cross-section view of an example of a GW probe for tube inspection, wherein absorbing material is associated to the external wall of a tube while it is checked; and

[0022] FIG. 2 illustrates relevant elements in an axial cross-section view of an example of a GW probe for tube inspection, wherein absorbing material is associated to the probe.

DETAILED DESCRIPTION OF DIFFERENT EMBODIMENTS

[0023] Turning now to the figures in which like numerals represent like elements throughout the several views, different embodiments of a tube inspection system, as well as features, aspects and functions that may be incorporated into one or more such embodiments, are described. For convenience, only some elements of the same group may be labeled with numerals. The purpose of the drawings is to describe different embodiments and not for production. Therefore, features shown in the figures are chosen for convenience and clarity of presentation only. It should be noted that the figures are for illustration purposes only and are not necessarily drawn to scale. Moreover, the language used in this disclosure has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter, resort to the claims being necessary to determine such inventive subject matter.

[0024] Fig. 1 illustrates an example of a hand-held probe 100 of an example of a Broadband- GW-Tube Inspection (BBGWTI) system. The hand-held probe 100 can comprise a housing 10 to which a guided-wave-transducer mechanism can be either permanently affixed or detachably affixed. An example of the guided-wave-transducer mechanism can be a transducer cylinder 12. In other embodiments, not shown in the figures, the guided-wave-transducer mechanism can comprise two separate rings; each ring can comprise a plurality of transducers. Each ring can be placed adjacent to each other, along the external circumference of the tube. Other embodiments may use other types of guided-wave-transducer mechanisms. The transducer cylinder 12 can be inserted into a near-end of a tube to be inspected 14. The hand-held probe 100 can include or be coupled with a plurality of different sizes of transducer cylinders 12, wherein each transducer cylinder could fit a different internal diameter of an inspected tube 14.

[0025] An example of a transducer cylinder 12 can comprise a zone of GW transducer mechanism 18, having two or more rings 16a and 16b where each ring can comprise a plurality of GW transducers 16 and a pressing mechanism 17. The plurality of GW transducers 16 are used for generating the guided waves in the tube under inspection 14 and for obtaining the reflected waves.

[0026] The first ring 16a can be referred to as a transmitting ring while the other ring 16b can be referred to as the receiving ring. In other possible embodiments the first ring 16a can be used as the receiving ring, while the other ring 16b can be used as the transmitting ring. In some embodiments a plurality of measuring cycles can be implemented one after the other. In each cycle the task of the rings can be changed. In the first cycle the first ring 16a can be used as the transmitting one, while in the second cycle it can be used as the receiving one, etc.

[0027] In some embodiments each ring, 16a and 16b represent multiple rings, the main ring 16a or 16b and one or more subrings (for convenience and simplicity the subrings are not shown in the figures). Each subring comprises a similar number of transducers as its associated main ring 16a (N transducers) or 16b (M transducers). The subrings can be used to distinguish between left and right (back and forward) propagating waves. The technique of determining the direction is known to a person with ordinary skill in the art. Processing the signal from the subrings can be done in a similar way as it is disclosed for the main rings 16a and 16b and therefore will not be further discussed. [0028] In addition FIG. 1 illustrates absorbing material in shape of substantially a ring 30 that is placed around the surface of the tube 14 creating a substantially ring 30 of few centimeters. The substantial ring 30 can be in the range of two to ten centimeters, for example. In one embodiment a ring of five centimeters was used, for example. In one embodiment the absorbing material can be pliable material such as plasticene, for example. In other embodiments rubber can be used, etc. The ring of the absorbing material 30 can be placed in association with the zone of GW transducer mechanism 18.

[0029] FIG. 2 illustrates similar elements as FIG. 1 but in FIG. 2 the location of the absorbing material 30 is different than in FIG. 1. In the example of FIG. 2, the absorbing material is placed around the surface of the transducer cylinder 12 in association with the zone of GW transducer mechanism 18. The absorbing material 30 creates a shape that is substantially ring of few centimeters around the transducer cylinder 12. The ring 30 can be in the range of two to ten centimeters, for example. In one embodiment five centimeters were used, for example. In one embodiment the absorbing material can be pliable material such as plasticene. In other embodiments rubber can be used, etc.

[0030] In some embodiments the absorbing material 30 would be inflatable in order to be pressed firmly to the tube wall. Such a ring of absorbing material could also be permanently affixed to the wall of the tube. In alternate embodiment, the absorbing material 30 could be pressed against the inside wall of the tube. In other embodiment, the absorbing material 30 can be affixed to a segment of the GW probe, which would come into action whenever a measurement is carried out. In such embodiment the absorbing material 30 would be coupled to the tube wall 14 either through its own elasticity or through a mechanism 17 such as inflation with compressed air. The segment of absorbing material 30 can be located towards the beginning of the probe, or towards its end, or between rings of transducers, for example.

[0031] Another example may use a foam filled ring 30 fitted onto the tube 14, which in one embodiment would be inflatable in order to press the ring 30 firmly to the tube wall. In some embodiments the foam filled ring 30 can be permanently affixed to the wall of the tube 14. In other embodiments, the absorbing material 30 can be pressed against the inside wall of the tube 14. Yet in some embodiment, the absorbing material 30 could be affixed to a segment of the GW probe 12, which would come into action whenever a measurement is carried out. In such embodiment the absorbing material 30 can be coupled to the tube wall 14 either through its own elasticity or through a mechanism 17 such as inflation with compressed air. The segment of absorbing material 30 could be located towards the beginning of the transducer cylinder 12, towards its end, or between rings of transducers 16.

[0032] The above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments may be used in combination with each other. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description.

[0033] The scope of the invention therefore should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein".

Claims

CLAIMS What is claimed is:

1. A method for inspecting the condition of a tube, the method comprising the actions of: a. employing a guided-wave-transducer mechanism (GWTM) that is configured to be associated with an inspected tube, wherein the GWTM has a zone of guided- wave transducers (GWTs), wherein the zone of guided-wave transducers comprises one or more rings, each ring has a plurality of guided-wave transducers (GWTs) distributed along the circumference of that ring;

b. employing absorbing material in association with the inspected tube; c. exciting mechanical waves by the GWTs of the first ring such that at least a portion of the mechanical waves propagates in the wall of the tube and along the tube axis; and

d. executing the a measuring cycle of the tube.

2. The method of claim 1, wherein the action of executing the a measuring cycle of the tube, further comprising:

e. converting mechanical waves, by each of the 'M' GWTs of the second ring, to an electronic signal that is transferred from each GWTs of the second ring toward a processor;

d. processing, at the processor, the converted 'M' electronic signals for providing a measured signal in which a wanted mode is enhanced;

wherein 'N' and 'M' are integer numbers equal or greater than two.

3. The method of claim 1, wherein the absorbing material comprises pliable material.

4. The method of claim 1, wherein the absorbing material comprises plasticene.

5. The method of claim 1, wherein the absorbing material comprises rubber.

6. The method of claim 1 , wherein the absorbing material comprises a foamed polymer.

7. The method of claim 1, wherein the action of employing absorbing material in association with the inspected tube further comprises associating the absorbing material to the external side of the wall of the tube in association with the zone of guided-wave transducers.

8. The method of claim 1, wherein the action of employing absorbing material in association with the inspected tube further comprises associating the absorbing material to the internal side of the wall of the tube.