Pipeline defect ultrasonic guided wave detection device and method based on piezoelectric transduction principle

Abstract

The application discloses a pipeline defect ultrasonic guided wave detection device and method based on a piezoelectric transduction principle, which comprises a plurality of ultrasonic guided wave excitation and receiving modules which are hingedly connected to each other through connecting pieces with concave-convex structures to form an array ring arranged around the circumference of a pipeline to be detected; a single ultrasonic guided wave excitation and receiving module comprises a connecting piece, a transducer module, and a first fine-tuning elastic pre-pressing assembly connected between the connecting piece and the transducer module; a sensitive piezoelectric transducer unit is arranged at the bottom end of the transducer module and connected with the transducer module through a second fine-tuning elastic pre-pressing assembly; the first fine-tuning elastic pre-pressing assembly is adjusted to tightly fix the transducer module to the pipeline to be detected; and the second fine-tuning elastic pre-pressing assembly is adjusted to fine-tune the pre-pressing force between the sensitive piezoelectric transducer unit and the pipeline to be detected.

Description

Technical Field

[0001] This invention is an ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle, which relates to the fields of piezoelectric transducers, oil and gas pipeline safety and non-destructive testing. Background Technology

[0002] As one of the main modes of international freight transport, pipeline transportation is favored for its advantages such as economy, reliability, and safety. Especially in oil and gas transportation, pipeline transportation is more reliable than water and rail transportation, can transport larger volumes, and has lower costs and energy consumption.

[0003] However, as oil and gas pipelines age, the steel pipe structure degrades and develops defects, constantly threatening pipeline safety. Among the various defects affecting pipeline safety, corrosion and mechanical damage are the two most common types. In long-distance pipeline systems, the systems are vast and complex, making traditional pipeline inspection techniques inadequate. Therefore, conducting safety performance inspections without disrupting normal pipeline operation is crucial.

[0004] Existing ultrasonic guided wave testing equipment for pipeline defects uses airbag loading, which requires the design of airbags of different sizes for pipelines of different diameters, increasing the system cost;

[0005] Meanwhile, existing equipment mostly detects damage by receiving axisymmetric echoes, but cannot receive bending mode echoes. Summary of the Invention

[0006] The technical problem this invention aims to solve is to provide a pipeline ultrasonic guided wave non-destructive testing device based on the piezoelectric transduction principle. It employs dry coupling to excite ultrasonic guided waves, enabling non-destructive testing of defects in operating oil and gas pipelines. It offers advantages such as fewer measuring points, a large detection range, and high screening efficiency. Utilizing the long propagation distance and low attenuation of guided waves, it achieves rapid detection of buried pipelines and pipelines in inaccessible locations. Analysis of the received signals can identify pipeline corrosion defects, welds, pipeline supports, bends, etc. Through condition-based inspection planning, accurate and timely suggestions can be provided for pipeline maintenance. It has significant advantages in achieving large-scale screening of operating pipelines, improving inspection efficiency, and reducing inspection costs.

[0007] In addition, the device adopts a modular design concept, which can efficiently excite detection signals of multiple frequencies and modes, and has wide applicability to pipes of various diameters and materials. The device excites and receives the echo signals of pipe defects through dry coupling, which greatly reduces the cost of pipe inspection.

[0008] To achieve the above-mentioned technical objectives, the present invention employs the following technical means:

[0009] An ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle includes multiple ultrasonic guided wave excitation and receiving modules hinged together by connectors with concave and convex structures to form an array ring arranged circumferentially around the pipeline to be inspected; each ultrasonic guided wave excitation and receiving module includes:

[0010] A connector having at least one first lug forming a female portion on one side and at least one second lug forming a male portion on the other side, the first lug and the second lug being hinged together.

[0011] The transducer module is connected to the connector via a first fine-tuning elastic preload assembly;

[0012] A sensitive piezoelectric transducer unit is disposed at the bottom of the transducer module and is connected to the transducer module through a second fine-tuning elastic preload assembly;

[0013] By adjusting the first fine-tuning elastic preload component, the transducer module is tightly fixed to the pipeline to be tested;

[0014] By adjusting the second fine-tuning elastic pre-pressure component, the pre-pressure between the sensitive piezoelectric transducer unit and the pipeline to be tested can be finely adjusted.

[0015] The first fine-tuning elastic preload assembly includes:

[0016] Fine-tuning bolts;

[0017] The connector has a through hole for the fine-tuning bolt to pass through, and the transducer module housing has a threaded hole that mates with the fine-tuning bolt.

[0018] A fine-tuning spring is sleeved around the fine-tuning bolt and located between the connector and the transducer module housing.

[0019] The sensitive piezoelectric transducer unit includes a sensitive piezoelectric transducer unit housing, a transducer unit top cover, a sensitive piezoelectric ceramic, a piezoelectric ceramic insulating sleeve, an impedance matching layer, a backing energy-absorbing layer, and a sensitive piezoelectric transducer unit RF adapter, wherein the piezoelectric ceramic insulating sleeve is disposed between the sensitive piezoelectric ceramic and the sensitive piezoelectric transducer unit housing.

[0020] The transducer module housing has multiple mounting slots evenly spaced along the axial direction of the pipe to be tested inside, for installing the sensitive piezoelectric transducer unit. Each mounting slot contains one of the sensitive piezoelectric transducer units.

[0021] The second fine-tuning elastic preload assembly includes:

[0022] A pressure equalization plate for the sensitive piezoelectric transducer unit is bridging the top of every two sensitive piezoelectric transducer units and is fixedly connected to the top of the sensitive piezoelectric transducer unit.

[0023] A preloaded spring sleeve, the bottom end of which is fixedly connected to the equalizing plate of the sensitive piezoelectric transducer unit, and the top end is open;

[0024] A preload spring, one end of which is disposed inside the preload spring sleeve, and the other end of which extends through the upper opening of the preload spring sleeve and abuts against the inner wall of the transducer module housing;

[0025] The sensitive piezoelectric transducer unit is installed in the mounting slot with its bottom end exposed.

[0026] The pressure fine-tuning screw is fixed to the bottom of the transducer module housing through bolt holes opened at the bottom of the transducer module housing;

[0027] The transducer module housing has a limiting protrusion at the upper part of the mounting groove to limit the travel of the sensitive piezoelectric transducer unit. By adjusting the pressure fine-tuning screw, the sensitive piezoelectric transducer unit can have a floating travel along the radial direction of the pipeline within the transducer module housing, which is used to achieve uniform pre-pressure recording of the sensitive piezoelectric transducer unit and protection of the sensitive piezoelectric ceramic.

[0028] The preloaded spring sleeve has a groove at the bottom to facilitate wiring of the sensitive piezoelectric transducer unit.

[0029] The sensitive piezoelectric ceramic material is PZT-5H;

[0030] The impedance matching layer is made of alumina ceramic.

[0031] The piezoelectric ceramic insulating sheath is made of alumina ceramic.

[0032] The backing energy-absorbing layer is a 1:1 mixture of high-purity nano-tungsten powder and two-component DG301 epoxy resin. It absorbs the resonance generated in the housing of the sensitive piezoelectric transducer unit due to the vibration of the sensitive piezoelectric ceramic caused by the positive and negative piezoelectric effects. At the same time, it enables the sensitive piezoelectric ceramic to stop vibrating quickly after being excited or receiving a signal, thus avoiding the reduction of the spatial resolution of the excitation signal and the echo signal due to crystal resonance.

[0033] The piezoelectric ceramic insulating sleeve transmits the vibration on the back of the sensitive piezoelectric ceramic to the backing energy-absorbing layer based on the impedance matching principle with the sensitive piezoelectric ceramic, thereby realizing unidirectional excitation waveguide of the sensitive piezoelectric ceramic.

[0034] Rubber anti-slip pads are provided at the contact points between the transducer module housing and the pipeline.

[0035] The housing of the sensitive piezoelectric transducer unit is made of 304 stainless steel and the interior is coated with polyurethane insulating paint.

[0036] This invention further discloses a working method for the ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle, comprising the following steps:

[0037] S1. Select the appropriate number of sensitive piezoelectric transducer units and the type and size of sensitive piezoelectric ceramics according to the required guided wave mode. Select the appropriate type of preload spring according to the characteristics of the required excitation signal. Determine the required number of ultrasonic guided wave excitation and receiving modules according to the diameter of the pipe being tested.

[0038] S2. Fix the sensitive piezoelectric transducer unit to the sensitive piezoelectric transducer unit equalizing plate and assemble the transducer module. Fix the transducer module to the connector to form an ultrasonic guided wave excitation and receiving module. The connectors with concave and convex structures are hinged to each other to form an array ring device arranged around the pipeline to be tested in the circumferential direction.

[0039] S3. Based on the characteristics of the required excitation signal, set the appropriate maximum pre-pressure value of the sensitive piezoelectric transducer unit by adjusting the pressure fine-tuning screw;

[0040] S4. Adjust the fine-tuning bolt in conjunction with the fine-tuning spring to ensure that the transducer module is tightly attached to the surface of the pipeline to be tested. Adjust the transducer module to ensure good coupling between the sensitive piezoelectric transducer unit and the pipeline to be tested.

[0041] By adjusting the extension distance of the pressure fine-tuning screw, the maximum pre-pressure limit of the sensitive piezoelectric transducer unit is adjusted, and all sensitive piezoelectric transducer units are in a uniformly stressed suspension state, thereby ensuring that all sensitive piezoelectric transducer units have consistent dry coupling performance.

[0042] By combining multiple turns of the aforementioned sensitive piezoelectric transducer units, delayed unidirectional excitation and phased array focusing functions can be achieved.

[0043] Beneficial effects:

[0044] Compared with the prior art, the present invention provides an ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle, which has the following beneficial effects:

[0045] First, this equipment, through a three-level adaptive dry coupling mechanism, can adapt to pipes of different diameters, thus having wide applicability. By adjusting the ultrasonic guided wave excitation and receiving modules, it can be applied to pipes of various diameters and materials. By changing the type and size of the sensitive piezoelectric ceramic, the required specific mode of guided wave can be excited. The excitation method based on pre-pressure and dry coupling further improves the consistency of ultrasonic guided wave excitation and reduces the detection cost of ultrasonic guided waves in pipelines, resulting in good economic benefits.

[0046] Second, in this equipment, by simply adjusting the installation direction of the sensitive piezoelectric transducer unit in the mounting slot, it can be used to receive bending modes reflected by non-axisymmetric defects, thereby enhancing the equipment's detection performance for non-axisymmetric defects.

[0047] Third, the device adopts a modular design concept, which can efficiently excite detection signals of multiple frequencies and modes, and has wide applicability to pipes of various diameters and materials. The device excites and receives the echo signals of pipe defects through dry coupling, which greatly reduces the cost of pipe inspection.

[0048] Fourth, the transducer module housing of the present invention has a limiting protrusion at the upper part of the mounting groove to limit the travel of the sensitive piezoelectric transducer unit. By adjusting the pressure fine-tuning screw, the sensitive piezoelectric transducer unit can have a floating travel of 3mm along the radial direction of the pipe within the transducer module housing, thereby achieving uniform pre-pressure loading on the sensitive piezoelectric transducer unit and protection of the sensitive piezoelectric ceramic. Attached Figure Description

[0049] Figure 1 This is a rendering of an ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle proposed in this invention.

[0050] Figure 2 The present invention provides an isometric ultrasonic guided wave excitation and receiving module for an ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle. Figure 1 ;

[0051] Figure 3 The present invention provides an isometric ultrasonic guided wave excitation and receiving module for an ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle. Figure 2 ;

[0052] Figure 4 The present invention provides an isometric ultrasonic guided wave excitation and receiving module for an ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle. Figure 1 Cross-sectional view;

[0053] Figure 5 This is a schematic diagram of the floating pre-compression dry coupling mechanism of the sensitive piezoelectric transducer unit of an ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle proposed in this invention.

[0054] Figure 6 This is a schematic diagram of the structure of the sensitive piezoelectric transducer unit of the present invention;

[0055] Figure 7 This is a cross-sectional schematic diagram of the connection structure between the transducer module housing and the sensitive piezoelectric transducer unit.

[0056] Figure 8 A schematic diagram of the connection structure between the bottom of the transducer module housing and the pressure fine-tuning screw;

[0057] In the diagram: 1. Ultrasonic guided wave excitation and receiving module; 2. Connection module; 3. Transducer module; 4. Sensitive piezoelectric transducer unit; 5. Connector; 6. Fine-tuning bolt; 7. Connecting bolt; 8. Transducer module housing top cover; 9. Transducer module housing; 10. Transducer module housing rear cover; 11. Transducer module housing bottom cover; 12. Rubber anti-slip pad; 13. Transducer module RF adapter; 14. Fine-tuning spring; 15. Pressure fine-tuning screw; 16. Sensitive piezoelectric transducer unit equalizing plate; 17. Preload spring sleeve; 18. Preload spring. 19. Spring; 20. Transducer top cover fixing screw; 21. Transducer rear cover fixing screw; 22. Preloaded spring sleeve fixing screw; 23. Sensitive piezoelectric transducer unit fixing hole; 24. Sensitive piezoelectric transducer unit fixing screw; 25. Sensitive piezoelectric transducer unit housing; 26. Transducer unit top cover; 27. Backing energy absorption layer; 28. Piezoelectric ceramic insulating sleeve; 29. ​​Sensitive piezoelectric ceramic; 30. Impedance matching layer; 31. Sensitive piezoelectric transducer unit RF adapter; 32. Slotted screw; 33. Sensitive piezoelectric transducer unit connection hole. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Guided wave technology has significant advantages in pipeline damage detection. On the one hand, guided waves can achieve rapid screening of large areas of oil and gas pipelines, and the signals received by the receiving probe contain a wealth of information about the overall structure between the excitation and reception points. On the other hand, the guided wave sound field covers the entire wall thickness, enabling the detection of internal and surface defects in components. Furthermore, it can detect hard-to-reach areas, offering high detection efficiency without requiring complete removal of the cladding layer, thus demonstrating promising application prospects.

[0060] This invention is based on the piezoelectric effect, using a sensitive transducer to excite and receive guided wave echo signals from pipe defects through dry coupling. The modular design of this invention makes the device highly adaptable to pipes of various diameters and materials, significantly reducing testing costs compared to traditional adhesive-based guided wave detection technology. Furthermore, the device configuration can be flexibly adjusted according to the guided wave modes and detection methods required for the actual testing.

[0061] The ultrasonic guided wave detection device for pipeline defects, by arranging the device at a single location on an unshielded pipe section, can achieve wide-range screening and classification of pipeline anomalies and defects. The modulated signal is generated by a signal generator, amplified by a high-voltage signal amplifier, and transmitted to the pipeline to be inspected through the dry coupling between the ultrasonic guided wave detection device and the pipeline. The echo signal generated by the defect or pipeline anomaly is received by the ultrasonic guided wave detection device, and the pipeline defects and anomalies are screened and classified by analyzing the echo signal.

[0062] Please see Figure 1-8 An ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle is proposed. It consists of multiple ultrasonic guided wave excitation and receiving modules 1. Each ultrasonic guided wave excitation and receiving module 1 consists of a connection module 2, a transducer module 3, and a sensitive piezoelectric transducer unit 4.

[0063] The connecting module 2 has axial rigidity and circumferential flexibility. Multiple connecting parts 5 are connected and extended circumferentially by meshing with each other through axial connecting bolts 7. The fine-tuning bolts 6 and fine-tuning springs 14 connect the transducer module 3 and the connecting parts 5 in the radial direction of the pipeline to form an ultrasonic guided wave excitation and receiving module 1 with only the degree of freedom of movement in the radial direction of the pipeline.

[0064] The pre-compression spring sleeve 17 and the sensitive piezoelectric transducer unit 4 are connected to the pressure equalization plate 16 of the sensitive piezoelectric transducer unit by M1.6 bolts. The pre-compression spring 18 is placed inside the pre-compression spring sleeve 17. The pre-compression spring is used to press the upper cover 8 of the transducer module housing. By setting a reasonable pressure fine-tuning screw 15 protrusion distance, when the sensitive piezoelectric transducer unit 4 is in dry coupling contact with the outer wall of the pipeline to be tested, a certain degree of retraction will occur, so that each sensitive piezoelectric transducer unit 4 bears a uniform pre-compression, while protecting the sensitive piezoelectric transducer unit 4 from excessive pressure that could damage the sensitive piezoelectric ceramic 28.

[0065] The signal line of the sensitive piezoelectric transducer unit 4 is led out from the transducer module RF adapter 13 at the rear cover 10 of the transducer module housing through the wire groove opened at the bottom of the pre-compression spring sleeve 17.

[0066] The second fine-tuning elastic pre-compression assembly, consisting of a sensitive piezoelectric transducer unit 4, a sensitive piezoelectric transducer unit equalizing plate 16, a pre-compression spring sleeve 17, and a pre-compression spring 18 placed inside, is placed in the transducer module housing 9. The transducer module housing upper cover 8, transducer module housing rear cover 10, and transducer module housing lower cover 11 are fixed by the transducer upper cover fixing screw 19, the transducer rear cover fixing screw 20, and the pressure fine-tuning screw 15, respectively. A rubber anti-slip pad 12 is provided at the contact position between the transducer module housing lower cover 11 and the pipeline to further ensure good fixation of the device on the pipeline to be tested.

[0067] The sensitive piezoelectric transducer unit 4 is the core part of the device, which realizes the excitation and reception of guided wave signals based on the piezoelectric effect. The housing 24 of the sensitive piezoelectric transducer unit is made of 304 stainless steel and is coated with polyurethane insulating paint inside, which has good strength to protect the sensitive piezoelectric ceramic 28 and shield external interference signals.

[0068] A piezoelectric ceramic insulating sleeve 27 is provided between the sensitive piezoelectric ceramic 28 and the housing 24 of the sensitive piezoelectric transducer unit; the backing energy-absorbing layer 26 is made of tungsten powder mixed with two-component DG301 epoxy resin, which absorbs the resonance generated in the housing 24 of the sensitive piezoelectric transducer unit due to the vibration of the sensitive piezoelectric ceramic 28 caused by the positive and negative piezoelectric effects, and at the same time makes the sensitive piezoelectric ceramic 28 stop vibrating quickly after being excited or receiving a signal, so as to avoid the crystal resonance reducing the spatial resolution of the excitation signal and the echo signal.

[0069] The housing 24 of the sensitive piezoelectric transducer unit is connected to the top cover 25 of the transducer unit by M1.6 flathead screws. The top cover 25 of the transducer unit has four sensitive piezoelectric transducer unit connection holes 32 for securing the sensitive piezoelectric transducer unit 4 to the sensitive piezoelectric transducer unit equalizing plate 16 by the sensitive piezoelectric transducer unit fixing screws 23.

[0070] Arrange the assembled device circumferentially on the pipeline to be tested, adjust the fine-tuning screw 6 to make the transducer module 3 fit tightly against the outer wall of the pipeline to be tested, make the sensitive piezoelectric transducer unit 4 tangent to the outer wall of the pipe, and keep the connector 5 in a taut state to check the coupling status between the impedance matching layer and the outer wall of the pipeline.

[0071] The signal generator and the signal amplifier are connected by wires, and the signal amplifier is connected to the RF adapter 13 of the transducer module corresponding to the sensitive piezoelectric transducer unit 4 used for signal excitation. The RF adapter 13 of the transducer module corresponding to the sensitive piezoelectric transducer unit 4 used for signal reception is connected to the signal receiving end, thus completing the construction of the pipeline ultrasonic guided wave detection system based on the piezoelectric transduction principle.

[0072] The mounting slot is a square mounting slot. By adjusting the mounting direction of the sensitive piezoelectric transducer unit in the mounting slot, it can be used to receive the bending mode reflected by the non-axisymmetric defect, thereby enhancing the equipment's detection performance for non-axisymmetric defects.

[0073] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle, characterized in that, Multiple ultrasonic wave excitation and receiving modules (1) are hinged to each other through connectors with concave and convex structures to form an array ring arranged around the circumference of the pipe to be tested; a single ultrasonic wave excitation and receiving module (1) includes: a connector (2) having at least one first lug forming a mother part on one side and at least one second lug forming a male part on the other side, the first lug and the second lug being hinged together. The transducer module (3) is connected to the connector (2) via a first fine-tuning elastic preload assembly; A sensitive piezoelectric transducer unit (4) is disposed at the bottom of the transducer module (3) and is connected to the transducer module (3) through a second fine-tuning elastic pre-compression component; By adjusting the first fine-tuning elastic preload component, the transducer module (3) is tightly fixed to the pipeline to be tested; By adjusting the second fine-tuning elastic pre-pressure component, the pre-pressure between the sensitive piezoelectric transducer unit (4) and the pipeline to be tested can be fine-tuned; The first fine-tuning elastic preload assembly includes: a fine-tuning bolt (6); The connector (2) has a through hole for the fine-tuning bolt (6) to pass through, and the outer shell of the transducer module (3) has a threaded hole that mates with the fine-tuning bolt (6). A fine-tuning spring (14) is sleeved around the outer periphery of the fine-tuning bolt (6) and located between the connector (2) and the housing of the transducer module (3); The sensitive piezoelectric transducer unit (4) includes a sensitive piezoelectric transducer unit housing (24), a transducer unit top cover (25), a sensitive piezoelectric ceramic (28), a piezoelectric ceramic insulating sleeve (27), an impedance matching layer (29), a backing energy-absorbing layer (26), and a sensitive piezoelectric transducer unit radio frequency adapter (30), wherein the piezoelectric ceramic insulating sleeve (27) is disposed between the sensitive piezoelectric ceramic (28) and the sensitive piezoelectric transducer unit housing (24); The transducer module (3) has multiple mounting slots evenly spaced along the axial direction of the pipe to be tested inside the housing for installing the sensitive piezoelectric transducer unit (4), and each mounting slot has one sensitive piezoelectric transducer unit (4) installed in it. The second fine-tuning elastic preload assembly includes: A pressure equalization plate (16) for sensitive piezoelectric transducer units is bridging the top of each pair of sensitive piezoelectric transducer units (4) and is fixedly connected to the top of the sensitive piezoelectric transducer units (4). The preloaded spring sleeve (17) is fixedly connected at its bottom end to the pressure equalization plate (16) of the sensitive piezoelectric transducer unit, and has an opening at its top end; The preload spring (18) has one end set inside the preload spring sleeve (17) and the other end extends out through the upper opening of the preload spring sleeve (17) and abuts against the inner wall of the outer shell of the transducer module (3); The sensitive piezoelectric transducer unit (4) is installed in the mounting slot with its bottom end exposed. The pressure fine-tuning screw (15) is fixed to the bottom of the transducer module (3) housing through the bolt hole opened at the bottom of the housing; The transducer module (3) housing has a limiting protrusion at the upper part of the mounting groove to limit the travel of the sensitive piezoelectric transducer unit (4). By adjusting the pressure fine-tuning screw (15), the sensitive piezoelectric transducer unit (4) has a floating travel along the radial direction of the pipe in the transducer module (3) housing, which is used to achieve uniform pre-pressure loading on the sensitive piezoelectric transducer unit (4) and protection of the sensitive piezoelectric ceramic (28).

2. The ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle according to claim 1, characterized in that, The preloaded spring sleeve (17) has a groove at the bottom to facilitate the wiring of the sensitive piezoelectric transducer unit (4).

3. The ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle according to claim 1, characterized in that, The sensitive piezoelectric ceramic (28) is made of PZT-5H material; The impedance matching layer (29) is made of alumina ceramic; The piezoelectric ceramic insulating sheath (27) is made of alumina ceramic; The backing energy-absorbing layer (26) is a 1:1 mixture of high-purity nano tungsten powder and two-component DG301 epoxy resin. It absorbs the resonance generated in the housing (24) of the sensitive piezoelectric transducer unit due to the vibration of the sensitive piezoelectric ceramic (28) caused by the positive and negative piezoelectric effects. At the same time, it makes the sensitive piezoelectric ceramic (28) stop vibrating quickly after it is excited or receives the signal, so as to avoid the crystal resonance reducing the spatial resolution of the excitation signal and the echo signal. The piezoelectric ceramic insulating sheath transmits the vibration on the back of the sensitive piezoelectric ceramic to the backing energy-absorbing layer based on the impedance matching principle with the sensitive piezoelectric ceramic (28) to achieve unidirectional excitation waveguide for the sensitive piezoelectric ceramic (28).

4. The ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle according to claim 1, characterized in that, The transducer module (3) has a rubber anti-slip pad at the contact point between the outer shell and the pipe.

5. The ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle according to claim 1, characterized in that, The housing of the sensitive piezoelectric transducer unit (4) is made of 304 stainless steel and the interior is coated with polyurethane insulating paint.

6. The ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle according to claim 1, characterized in that, The mounting slot is a square mounting slot. The mounting direction of the sensitive piezoelectric transducer unit (4) in the mounting slot is adjusted to receive the bending mode reflected by the non-axisymmetric defect.

7. A method for operating the ultrasonic guided wave detection device for pipeline defects based on the piezoelectric transduction principle as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Select the appropriate number of sensitive piezoelectric transducer units (4) and the type and size of sensitive piezoelectric ceramics (28) according to the waveguide mode to be excited. Select the appropriate type of preload spring (18) according to the characteristics of the signal to be excited. Determine the required number of ultrasonic waveguide excitation and receiving modules (1) according to the diameter of the pipe to be tested. S2. Fix the sensitive piezoelectric transducer unit (4) to the sensitive piezoelectric transducer unit equalizing plate (16) and assemble the transducer module (3). Fix the transducer module (3) to the connector (2) to form an ultrasonic guided wave excitation and receiving module (1). The connector (2) with concave and convex structure is hinged to each other to form an array ring device arranged around the circumference of the pipeline to be tested. S3. Based on the characteristics of the required excitation signal, set the appropriate maximum pre-pressure value of the sensitive piezoelectric transducer unit (4) by adjusting the pressure fine-tuning screw (15); S4. Adjust the fine-tuning bolt (6) in conjunction with the fine-tuning spring (14) to tightly attach the transducer module (3) to the surface of the pipeline to be tested, and adjust the transducer module (3) to ensure good coupling between the sensitive piezoelectric transducer unit (4) and the pipeline to be tested. By adjusting the extension distance of the pressure fine-tuning screw (15), the maximum pre-pressure limit of the sensitive piezoelectric transducer unit (4) is adjusted and all sensitive piezoelectric transducer units (4) are in a uniformly stressed suspension state, thereby ensuring that all sensitive piezoelectric transducer units (4) have consistent dry coupling performance. By combining the multiple turns of the sensitive piezoelectric transducer unit (4), delayed unidirectional excitation and phased array focusing functions can be achieved.

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