Ultrasonic guided wave online monitoring device and method suitable for high-temperature pipeline

Abstract

The invention relates to the technical field of nondestructive testing of high-temperature pipelines, and particularly discloses an ultrasonic guided wave online monitoring device suitable for high-temperature pipelines, which comprises a laser ring array, a laser guided wave excitation module, a fiber grating sensor network, an optical fiber sensing and receiving module and a central controller, the laser guided wave excitation module and the optical fiber sensing receiving module are controlled by a central controller; the laser guided wave excitation module is connected with the laser annular array; the optical fiber sensing receiving module is connected with the optical fiber grating sensor network, the optical fiber grating sensor network is arranged on the outer wall of a pipeline, and each optical fiber grating sensor in the optical fiber grating sensor network comprises a plurality of measuring points; the central controller is electrically connected with the optical fiber sensing and receiving module and the laser guided wave excitation module. According to the invention, the degree of manual intervention in a high-temperature environment is reduced, the operation and maintenance cost and the safety risk are reduced, the monitoring automation level is improved, and the distributed real-time online monitoring of the health of the high-temperature pipeline structure is realized.

Description

Technical Field

[0001] This invention belongs to the field of non-destructive testing technology for high-temperature pipelines, specifically relating to an ultrasonic guided wave online monitoring device and method suitable for high-temperature pipelines. Background Technology

[0002] In high-end industrial fields such as aerospace, supercritical thermal power, nuclear power, and metallurgy, core equipment such as high-temperature pipelines, combustion chambers, and reactors operate under high-temperature conditions of 200℃-500℃ for extended periods. They also face complex environments including high pressure, strong corrosion, and strong electromagnetic interference. The inner walls of these equipment are highly susceptible to various forms of damage, such as oxidation corrosion, fatigue crack propagation, and wall thinning. Failure to provide timely monitoring and early warning can easily lead to major safety accidents such as media leaks and explosions. Therefore, developing a non-contact high-temperature pipeline monitoring technology is crucial. Ultrasonic guided wave technology, with its unique advantages such as long propagation distance, low attenuation, and sensitivity to cross-sectional changes, has been widely applied in the non-destructive testing and health monitoring of tubular structures. Ultrasonic guided waves are generated by the mechanical vibration of an excitation source. As the vibration propagates in the waveguide, reflection, transmission, and mode conversion may occur at the interface of the elastic medium, allowing the ultrasonic waves generated by the same source to form different wave forms through waveform transformation, thereby expanding the application range of ultrasonic waves. Guided waves carry characteristic information about the excitation source and the material itself. Combined with the variation law of sound wave intensity, the size, location and other physical parameters of internal defects in the pipeline structure can be accurately inferred. Therefore, ultrasonic guided wave technology is often used for corrosion monitoring of high-temperature pipelines.

[0003] Currently, existing ultrasonic guided wave monitoring technology still has significant limitations: the operating temperature of electromagnetic ultrasonic transducers is limited by the Curie temperature of permanent magnets, and high-temperature environments can lead to changes in coil impedance and increased thermal noise, resulting in a significant decrease in signal strength and signal-to-noise ratio; the performance of piezoelectric materials and coupling agents in conventional piezoelectric ultrasonic transducers degrades sharply or even fails completely above 300°C. Although thermal insulation design can enable them to operate briefly at higher temperatures (such as 500°C), the unreliability and variability of the coupling state severely affect signal consistency and measurement accuracy, making it difficult to meet the practical needs of long-term online monitoring. Therefore, existing monitoring technologies based on contact ultrasonic guided wave transducers are limited by the transducer's own temperature resistance, signal stability, and coupling reliability, and can usually only be carried out offline after the equipment is shut down and cooled down. This cannot meet the core requirements of long-term, real-time, and online monitoring of high-temperature pipelines, which not only significantly increases equipment maintenance costs and safety risks but also fails to capture the dynamic development process of damage in real time.

[0004] In summary, the development of a new ultrasonic guided wave online monitoring device and method can fundamentally avoid the direct damage to transducers and coupling instability caused by high temperatures, thereby achieving high-precision, high-reliability, and real-time online monitoring of high-temperature pipeline damage. This has significant theoretical and engineering application value in the field of pipeline defect detection. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the existing technology and provide an ultrasonic guided wave online monitoring device and method suitable for high-temperature pipelines. It achieves non-contact detection in high-temperature environments through laser excitation without the need for coupling agent, and fiber optic sensing avoids electromagnetic interference. It can collect ultrasonic guided wave signals from high-temperature pipelines and signal changes caused by pipeline cracks or corrosion, and reduces the degree of manual intervention in high-temperature environments.

[0006] To achieve the above objectives, one of the technical solutions of the present invention is: an online monitoring device for ultrasonic guided waves in high-temperature pipelines, comprising a laser ring array, a laser guided wave excitation module, a fiber optic grating sensor network, a fiber optic sensing and receiving module, and a central controller. The laser guided wave excitation module and the fiber optic sensing and receiving module are controlled by the central controller. The laser guided wave excitation module is connected to the laser ring array, and the laser guided wave excitation module sends a signal, causing the laser ring array to emit pulsed laser light onto the pipeline surface to excite Lamb wave ultrasonic guided waves. The fiber optic sensing and receiving module is connected to the fiber optic grating sensor network, which is disposed on the outer wall of the pipeline. Each fiber optic grating sensor in the fiber optic grating sensor network contains multiple measuring points for sensing ultrasonic guided wave signals propagating in the pipeline and transmitting the optical signals to the fiber optic sensing and receiving module for photoelectric conversion and signal amplification. The central controller is electrically connected to both the fiber optic sensing and receiving module and the laser guided wave excitation module, and is used to receive and process ultrasonic guided wave signals, control laser excitation parameters, and realize damage monitoring and location.

[0007] In a preferred embodiment of the present invention, the laser ring array includes a base, a bracket, a fixing slider, a laser emitting probe, a positioning bolt, and a set screw.

[0008] In a further preferred embodiment, the laser emission probe is connected to the bracket via a fixed slider. The relative height between the probe and the pipe is adjusted by a positioning bolt, and the incident angle and the relative distance between the probes on the bracket are adjusted by a set screw, so as to achieve multi-angle and multi-position excitation of different modes of Lamb waves.

[0009] In a preferred embodiment of the present invention, the fiber Bragg grating sensor is a high-temperature resistant fiber Bragg grating sensor with a maximum temperature tolerance of 500-800℃, suitable for online health monitoring of pipelines in normal or high-temperature environments.

[0010] In a preferred embodiment of the present invention, each fiber Bragg grating sensor in the fiber Bragg grating sensor network is arranged along the axial direction of the pipe and uniformly distributed at 30-60° intervals along the circumference of the pipe. Each fiber Bragg grating sensor has a fiber Bragg grating (FBG) measuring point arranged every 10-30 cm along the axial direction of the pipe. The number of measuring points is dynamically configured according to the length of the pipe to achieve full coverage ultrasonic guided wave signal acquisition along the entire length of the pipe.

[0011] In a preferred embodiment of the present invention, the fiber optic sensing receiving module is synchronously connected to multiple fiber optic grating sensors in the fiber optic grating sensor network, enabling simultaneous acquisition and demodulation of ultrasonic guided wave signals from all measuring points, thereby achieving multi-channel, high-precision, and time-synchronized signal acquisition.

[0012] In a preferred embodiment of the present invention, the central controller includes a user control interface, a signal processing module, and an image display module; the signal processing module is used to sequentially perform low-pass filtering, effective time-domain segment extraction, and signal truncation processing on the raw signal from the fiber optic sensor receiving module to extract time-domain features; the signal processing module is also used to compare the currently acquired damaged signal with the pre-stored undamaged baseline signal to calculate the damage index of each measuring point, whereby the damage index is a quantified value of the time-domain feature difference between the damaged signal and the baseline signal; the image display module is used to display the damage index distribution map, ultrasonic guided wave propagation image, and pipeline health status assessment results in real time.

[0013] In a preferred embodiment of the present invention, the central controller presets a damage index threshold, classifies and evaluates the degree of damage to the high-temperature pipeline based on the difference between the damage index of each measuring point and the threshold, and outputs an alarm or maintenance suggestion.

[0014] In a preferred embodiment of the present invention, the central controller is further used to control the excitation parameters of the laser waveguide excitation module, including the laser pulse frequency, amplitude and period, so as to realize active modulation and optimized excitation of different modes of Lamb waves.

[0015] In a preferred embodiment of the present invention, the laser ring array, laser waveguide excitation module, fiber optic grating sensor network, fiber optic sensing receiver module, and central controller form a closed-loop monitoring system in spatial layout. The laser excitation point and the fiber optic sensing point are distributed in a non-overlapping manner in the circumference of the pipeline to avoid the direct coupling effect of excitation interference on the sensing signal.

[0016] To achieve the above objectives, the second technical solution of the present invention is: an application of an ultrasonic guided wave online monitoring device suitable for high-temperature pipelines.

[0017] In a preferred embodiment of the present invention, the device is suitable for high-temperature pipelines, and is particularly suitable for online non-destructive testing and structural health monitoring of long-distance transmission pipelines in industries such as nuclear power, petrochemicals, and power, where the operating temperature ranges from room temperature to 500°C.

[0018] To achieve the above objectives, the third technical solution of the present invention is: a monitoring method based on the above-mentioned online monitoring device, comprising the following steps:

[0019] (1) Baseline signal acquisition: Under the condition of no damage to the high temperature pipeline, the laser waveguide excitation module is controlled by the central controller to emit a five-cycle sinusoidal modulation excitation signal; the laser beam irradiates the pipeline surface at a set angle through the ring array structure, and excites the Lamb wave to propagate along the pipe wall; the ultrasonic waveguide response signal is synchronously sensed by all measuring points in the fiber optic grating sensor network, and the fiber optic sensing receiving module transmits the acquired signal as a baseline signal set and stores it in the central controller.

[0020] (2) Acquisition of the signal to be measured: During the operation of the high-temperature pipeline, repeat the operation of step (1) to acquire the ultrasonic guided wave response signal under the current state as the signal set to be measured;

[0021] (3) Preprocessing of raw signals: The baseline signal set obtained in step (1) and the signal set to be tested obtained in step (2) are respectively subjected to low-pass filtering using the following filtering formula to suppress high-frequency noise and retain effective guided wave components: , where a k b k Here, x(n) represents the filter coefficients, x(n) represents the input signal, and y(n) represents the filtered signal.

[0022] (4) Truncate the filtered signal to the same duration: Truncate all signals obtained in step (3) to the same duration. The truncation formula is as follows: Where, x cut (t) represents the truncated signal, t is the continuous time, and the starting time is t_t. s Based on the arrival time of the first wave of the signal, the termination time t e Using the shortest signal duration among all measurement points as the benchmark, the truncated baseline signal set and the signal set to be measured are obtained.

[0023] (5) Damage Index Calculation: Calculate the Damage Index (DI) for each measuring point:

[0024] Where DI is the damage index of the i-th measurement point, representing the relative energy change of the signal at that measurement point relative to the baseline, and u(i) is the damage signal at the current measurement point. b (i) represents the corresponding baseline signal;

[0025] (6) Damage localization and assessment: The damage index threshold is set to 3σ, where σ is the standard deviation of DI of all measurement points in the baseline signal set. If the DI of any measurement point is greater than 3σ, it is determined that there is damage in the area where the measurement point is located. By comparing the DI values ​​of multiple measurement points and combining the spatial distribution of measurement points, the axial and circumferential coordinates of the damaged area are located.

[0026] (7) Results output: The damage index distribution map, the location of the exceeding measurement point, and the damage assessment results are output through the central controller.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. This invention achieves non-contact detection in high-temperature environments through laser excitation without the need for coupling agent, effectively solving the core limitations of existing contact ultrasonic guided wave monitoring technology; it avoids the signal deviation problem caused by the failure of coupling agent in piezoelectric transducers, and gets rid of the temperature resistance limitation of electromagnetic ultrasonic transducers, and can stably adapt to the long-term monitoring needs of high-temperature pipelines of 200-500℃.

[0029] 2. This invention employs fiber optic sensing technology that integrates fiber optic grating sensing to construct a three-dimensional sensing network for the circumferential and axial directions of the pipeline, which has excellent anti-electromagnetic interference capabilities; it can accurately collect signal changes caused by ultrasonic guided waves and damage in high-temperature pipelines, and achieve omnidirectional and multi-point synchronous acquisition of signals based on distributed sensing characteristics.

[0030] 3. By acquiring the guided wave response characteristics in the fiber optic measurement point network, this invention can complete the two-dimensional axial and circumferential positioning of damage, thereby realizing a comprehensive real-time online assessment of pipeline damage status.

[0031] 4. Each transmitting probe of the laser excitation array of the present invention can be independently controlled in terms of its installation attitude and position by adjusting the positioning components, so that the ultrasonic guided wave excitation mode is designable; it can flexibly excite multi-mode ultrasonic guided waves, adapt to pipes of different specifications and structures, and greatly expand the scope of application of the technology.

[0032] 5. This invention significantly reduces the degree of human intervention in high-temperature environments, reduces operation and maintenance costs and safety risks, and improves the level of monitoring automation; it realizes distributed real-time online monitoring of the structural health of high-temperature pipelines without the need for shutdown for cooling, ensuring the safe and stable operation of equipment. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall structure of the laser-excited fiber optic sensing-based high-temperature pipeline ultrasonic guided wave online monitoring device of the present invention.

[0034] In the diagram: 1-Laser waveguide excitation module, 2-Central controller, 3-Fiber optic sensor receiving module, 4-Laser ring array, 5-High temperature pipeline, 6-Fiber grating sensor network;

[0035] Figure 2 This is a schematic diagram of the laser ring array structure of the online monitoring device of the present invention.

[0036] In the diagram: 11-positioning bolt, 12-set screw, 13-fixing slider, 14-laser emitting probe, 15-bracket, 16-base;

[0037] Figure 3 Here is an example diagram of the ultrasonic guided wave signal of the pipeline collected by the fiber optic sensing receiving module of the present invention. (1) is measured at measuring point 1, and (2) is measured at measuring point 2.

[0038] Figure 4 This is a comparison chart of signal impairment indices collected from different measuring points on a fiber Bragg grating sensor in the online monitoring device of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0040] Example 1

[0041] A schematic diagram of the overall structure of an ultrasonic guided wave online monitoring device suitable for high-temperature pipelines is shown below. Figure 1 As shown, the system includes a laser waveguide excitation module 1, a central controller 2, an optical fiber sensor receiving module 3, a laser ring array 4, and a fiber optic grating sensor network 6. The laser waveguide excitation module 1 is connected to the laser ring array 4. The central controller 2 controls the laser waveguide excitation module 1 to emit signals and the optical fiber sensor receiving module 3 to receive signals. The laser ring array 4 receives signals and emits laser light to illuminate the surface of the high-temperature pipe 5 to excite Lamb wave ultrasonic guided waves. The central controller 2 can control and adjust the frequency, amplitude, and number of cycles of the excitation signal emitted by the laser waveguide excitation module 1.

[0042] The fiber optic sensing receiving module 3 is connected to the fiber Bragg grating sensor network 6, which is disposed on the outer wall of the pipe. The fiber Bragg grating sensor network 6 comprises eight fiber Bragg grating sensors arranged parallel to each other along the pipe's axial direction. Each fiber Bragg grating sensor is evenly distributed at 45° intervals along the pipe's circumference, with eight measuring points per sensor. The distance between adjacent measuring points is 20 cm, resulting in a total of 64 measuring points in the fiber Bragg grating sensor network 6. These points are used to sense the ultrasonic guided wave signals propagating in the pipe and transmit the optical signals to the fiber optic sensing receiving module 3 for photoelectric conversion and signal amplification. The fiber optic sensing receiving module 3 is synchronously connected to the eight fiber Bragg grating sensors in the fiber Bragg grating sensor network 6, enabling simultaneous acquisition and demodulation of ultrasonic guided wave signals from all measuring points, achieving multi-channel, high-precision, and time-synchronized signal acquisition. The central controller 2 is electrically connected to both the fiber optic sensing receiving module 3 and the laser guided wave excitation module 1, and is used to receive and process ultrasonic guided wave signals, control laser excitation parameters, and achieve damage monitoring and localization.

[0043] The optical fibers are laid parallel to the pipe axis, and each fiber is distributed at equal angular intervals in the circumferential direction to ensure uniform coverage of the measuring points on the pipe wall without any omissions. Each measuring point senses the reflection, scattering, and mode conversion signals caused by defects during the propagation of the guided wave in real time, and converts them into changes in optical wavelength. The optical fiber sensing and receiving module 3 then completes the photoelectric conversion and signal amplification.

[0044] Figure 2 The diagram shows the structure of the laser ring array 4, including: a base 16, a bracket 15, a fixed slider 13, a laser emitting probe 14, positioning bolts 11, and set screws 12. The base 16 is welded and fixed to the bracket 15, making the bracket 15 vertically positioned on the outer surface of the high-temperature pipe 5. The fixed slider 13 is slidably installed along the axial direction of the bracket 15. The laser emitting probe 14 is fixed to the fixed slider 13 by the positioning bolts 11. By adjusting the tightening position of the positioning bolts 11, the radial distance between the laser emitting probe 14 and the surface of the high-temperature pipe 5 can be changed. The fixed slider 13 is tightened and fixed to the bracket 15 by the set screws 12, used to adjust the swing angle of the laser emitting probe 14 on the bracket 15, as well as the relative positions between all the laser emitting probes 14. This allows for controllable adjustment of the laser beam incident angle and incident position, enabling the excitation of ring array ultrasonic guided waves with different spacing and angle combinations, thereby greatly expanding the flexibility and coverage of the detection scheme.

[0045] In the fiber Bragg grating sensor network 6, each fiber Bragg grating sensor is a single-mode fiber with multiple fiber Bragg gratings (FBGs) etched onto it. Each FBG is an independent sensing unit, responding to local strain changes caused by ultrasonic guided waves, with its reflection spectrum center wavelength shifting with strain. The fiber optic sensing receiving module 3 uses a commercial fiber Bragg grating demodulator for signal acquisition, possessing multi-channel synchronous acquisition capability, a sampling frequency of not less than 1 MHz, and a resolution better than 1 pm. The central controller 2 is an embedded industrial control unit, with a built-in data acquisition card, signal processing unit, and storage module, supporting real-time reception and storage of time-domain waveform data from the fiber optic sensing receiving module 3. The fiber Bragg grating sensor is a high-temperature resistant sapphire fiber Bragg grating sensor, with a maximum withstand temperature of 500℃.

[0046] The central controller includes a user control interface, a signal processing module, and an image display module. The signal processing module sequentially performs low-pass filtering, effective time-domain segment extraction, and signal truncation on the raw signal from the fiber optic sensor receiving module to extract time-domain features. The signal processing module also compares the currently acquired damaged signal with a pre-stored undamaged baseline signal to calculate the damage index at each measuring point; the damage index is a quantified value of the time-domain feature difference between the damaged signal and the baseline signal. The image display module displays the damage index distribution map, ultrasonic guided wave propagation image, and pipeline health status assessment results in real time. The central controller presets a damage index threshold. The central controller also controls the excitation parameters of the laser guided wave excitation module.

[0047] The laser ring array, laser waveguide excitation module, fiber optic grating sensor network, fiber optic sensing and receiving module, and central controller form a closed-loop monitoring system in terms of spatial layout. The laser excitation points and fiber optic sensing points are distributed in a non-overlapping manner around the pipe.

[0048] A ring laser array is used to non-contactly excite the outer surface of the pipe, generating Lamb waves (ultrasonic guided waves) that propagate along the pipe wall. The excitation signal is precisely controlled by a central controller, outputting a five-cycle sinusoidal modulated pulse. The center frequency is dynamically adjusted according to the pipe material and thickness to ensure that the energy is concentrated on the dominant mode of the guided wave. The laser array consists of multiple laser emitting probes. By adjusting the positioning bolts and set screws, the radial distance, circumferential angle, and swing posture of each probe can be independently controlled, enabling flexible excitation of multi-mode guided waves and improving the diversity and coverage of defect responses.

[0049] Example 2

[0050] A monitoring method based on the online monitoring device in Embodiment 1 includes the following steps:

[0051] (1) Baseline signal acquisition: Under the condition of no damage to the high temperature pipeline, the laser guided wave excitation module is controlled by the central controller to emit a five-cycle sinusoidal modulation excitation signal with a signal frequency of 50 kHz. The laser excites Lamb waves on the pipeline surface and propagates along the pipe wall. The laser beam irradiates the pipeline surface at a set angle through the ring array structure, and excites Lamb waves to propagate along the pipe wall. The ultrasonic guided wave response signal is synchronously sensed by a total of 64 measuring points of 8 fiber optic grating sensors. The fiber optic sensing receiving module collects the signal as a baseline signal, transmits it, and stores it in the central controller.

[0052] (2) Acquisition of the signal to be measured: During the operation of the high-temperature pipeline, repeat the operation of step (1) to acquire the ultrasonic guided wave response signal under the current state as the signal set to be measured;

[0053] (3) Preprocessing of raw signals: The baseline signal set obtained in step (1) and the signal set to be tested obtained in step (2) are respectively subjected to low-pass filtering using the following filtering formula to suppress high-frequency noise and retain effective guided wave components: , where a k b k Here, x(n) represents the filter coefficients, x(n) represents the input signal, and y(n) represents the filtered signal.

[0054] (4) Truncate the filtered signal to the same duration: To unify the comparison benchmark, all signals obtained in step (3) are truncated to the same duration. The truncation formula is as follows: Where, x cut (t) represents the truncated signal, t is the continuous time, and the starting time is t_t. s Based on the arrival time of the first wave of the signal, the termination time t e Using the shortest signal duration among all measurement points as the benchmark, the truncated baseline signal set and the signal set to be measured are obtained.

[0055] (5) Damage Index Calculation: Calculate the Damage Index (DI) for each measuring point:

[0056] Where DI is the damage index of the i-th measurement point, representing the relative energy change of the signal at that measurement point relative to the baseline, and u(i) is the damage signal at the current measurement point. b (i) represents the corresponding baseline signal;

[0057] (6) Damage localization and assessment: The damage index threshold is set to 3σ, where σ is the standard deviation of DI of all measurement points in the baseline signal set. If the DI of any measurement point is greater than 3σ, it is determined that there is damage in the area where the measurement point is located. By comparing the DI values ​​of multiple measurement points and combining the spatial distribution of measurement points, the axial and circumferential coordinates of the damaged area are located.

[0058] (7) Results output: The damage index distribution map, the location of the exceeding measurement point, and the damage assessment results are output through the central controller.

[0059] Figure 3 The figure shows an example of ultrasonic guided wave signals collected from a pipeline by a fiber optic grating sensor network. (1) The signal was measured at measuring point 1, and (2) The signal was measured at measuring point 2. The figure includes a baseline signal, a damage signal, and a scattered signal. The baseline signal is the signal collected under undamaged pipeline conditions, the damage signal is the signal collected under conditions where the pipeline has cracks or defects, and the scattered signal is the difference between the damage signal and the baseline signal.

[0060] Figure 4 This is a comparison chart of signal impairment indices collected from different measurement points on the fiber of one of the fiber Bragg grating sensors of the present invention.

[0061] Example 3

[0062] An application of an ultrasonic guided wave online monitoring device for high-temperature pipelines is disclosed. This online monitoring device is suitable for high-temperature pipelines, especially for online non-destructive testing and structural health monitoring of long-distance transport pipelines operating in the nuclear power, petrochemical, and power industries with operating temperatures ranging from room temperature to 500°C.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An online ultrasonic guided wave monitoring device suitable for high-temperature pipelines, characterized in that, The system includes a laser ring array, a laser waveguide excitation module, a fiber optic grating sensor network, a fiber optic sensing and receiving module, and a central controller. The laser waveguide excitation module and the fiber optic sensing and receiving module are controlled by the central controller. The laser waveguide excitation module is connected to the laser ring array. The fiber optic sensing and receiving module is connected to the fiber optic grating sensor network. The fiber optic grating sensor network is disposed on the outer wall of the pipe, and each fiber optic grating sensor in the fiber optic grating sensor network contains multiple measuring points. The central controller is electrically connected to both the fiber optic sensing and receiving module and the laser waveguide excitation module.

2. The ultrasonic guided wave online monitoring device for high-temperature pipelines as described in claim 1, characterized in that, The laser ring array includes a base, a bracket, a fixed slider, a laser emitting probe, positioning bolts, and a set screw.

3. The ultrasonic guided wave online monitoring device for high-temperature pipelines as described in claim 2, characterized in that, The laser emission probe is connected to the bracket via a fixed slider. The relative height of the probe to the pipe is adjusted by a positioning bolt, and the incident angle and the relative distance between the probes on the bracket are adjusted by a set screw.

4. The ultrasonic guided wave online monitoring device for high-temperature pipelines as described in claim 1, characterized in that, The fiber Bragg grating sensor is a high-temperature resistant fiber Bragg grating sensor with a maximum temperature tolerance of 500-800℃.

5. The ultrasonic guided wave online monitoring device for high-temperature pipelines as described in claim 1, characterized in that, The fiber Bragg grating sensor network is arranged parallel to the pipe axis. Each fiber Bragg grating sensor in the network is evenly distributed at 30-60° intervals along the circumference of the pipe. Each fiber Bragg grating sensor has a fiber Bragg grating measuring point arranged every 10-30 cm along the pipe axis.

6. The ultrasonic guided wave online monitoring device for high-temperature pipelines as described in claim 1, characterized in that, The fiber optic sensing receiver module is synchronously connected to multiple fiber optic grating sensors in the fiber optic grating sensor network.

7. The ultrasonic guided wave online monitoring device for high-temperature pipelines as described in claim 1, characterized in that, The central controller includes a user control interface, a signal processing module, and an image display module. The signal processing module sequentially performs low-pass filtering, effective time-domain segment extraction, and signal truncation on the raw signal from the fiber optic sensor receiving module to extract time-domain features. The signal processing module also compares the currently acquired damaged signal with a pre-stored undamaged baseline signal to calculate the damage index at each measuring point; the damage index is a quantified value of the time-domain feature difference between the damaged signal and the baseline signal. The image display module displays the damage index distribution map, ultrasonic guided wave propagation image, and pipeline health status assessment results in real time. The central controller presets a damage index threshold. The central controller also controls the excitation parameters of the laser guided wave excitation module.

8. The ultrasonic guided wave online monitoring device for high-temperature pipelines as described in claim 1, characterized in that, The laser ring array, laser waveguide excitation module, fiber optic grating sensor network, fiber optic sensing and receiving module, and central controller form a closed-loop monitoring system in terms of spatial layout. The laser excitation points and fiber optic sensing points are distributed in a non-overlapping manner around the pipe.

9. An application of the ultrasonic guided wave online monitoring device for high-temperature pipelines as described in any one of claims 1-8.

10. A monitoring method based on the ultrasonic guided wave online monitoring device for high-temperature pipelines according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Baseline signal acquisition: Under the condition of no damage to the high temperature pipeline, the laser waveguide excitation module is controlled by the central controller to emit a five-cycle sinusoidal modulation excitation signal; the laser beam irradiates the pipeline surface at a set angle through the ring array structure, and excites the Lamb wave to propagate along the pipe wall; the ultrasonic wave response signal is synchronously sensed by all measuring points of the fiber optic grating sensor network, and after being collected by the fiber optic sensing receiving module, it is transmitted as a baseline signal set and stored in the central controller. (2) Acquisition of the signal to be measured: During the operation of the high-temperature pipeline, repeat the operation of step (1) to acquire the ultrasonic guided wave response signal under the current state as the signal set to be measured; (3) Preprocessing of raw signals: Low-pass filtering is performed on the baseline signal set obtained in step (1) and the test signal set obtained in step (2) using the following filtering formula: , where a k b k Here, x(n) represents the filter coefficients, x(n) represents the input signal, and y(n) represents the filtered signal. (4) Truncate the filtered signal to the same duration: Truncate all signals obtained in step (3) to the same duration. The truncation formula is as follows: Where, x cut (t) represents the truncated signal, t is the continuous time, and the starting time is t_t. s Based on the arrival time of the first wave of the signal, the termination time t e Using the shortest signal duration among all measurement points as the benchmark, the truncated baseline signal set and the signal set to be measured are obtained. (5) Damage Index Calculation: Calculate the Damage Index (DI) for each measuring point: Where DI is the damage index of the i-th measurement point, representing the relative energy change of the signal at that measurement point relative to the baseline, and u(i) is the damage signal at the current measurement point. b (i) represents the corresponding baseline signal; (6) Damage localization and assessment: The damage index threshold is set to 3σ, where σ is the standard deviation of DI of all measurement points in the baseline signal set. If the DI of any measurement point is greater than 3σ, it is determined that there is damage in the area where the measurement point is located. By comparing the DI values ​​of multiple measurement points and combining the spatial distribution of measurement points, the axial and circumferential coordinates of the damaged area are located. (7) Results output: The damage index distribution map, the location of the exceeding measurement point, and the damage assessment results are output through the central controller.

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