Non-invasive vibration-based material identification and leakage detection for underground pipelines

Abstract

A nondestructive evaluation system and method are provided for detecting the material type and leakage of an underground service line. An impactor applies a controlled impact to an instrumented rod in contact or proximity with the service line, inducing stress waves that propagate into the service line and surrounding soil. Sensors on the rod and / or on the ground surface detect the resulting waveforms. A processing unit analyzes time and frequency domain characteristics such as wave speed, attenuation, and vibration response to determine service line material and identify anomalies associated with leakage. The system enables accurate, real-time diagnostics of buried pipelines without excavation or fluid interruption.

Description

NON-INVASIVE VIBRATION-BASED MATERIAL IDENTIFICATION AND LEAKAGE DETECTION FOR UNDERGROUND PIPELINESBACKGROUND

[0001] The assessment and maintenance of underground pipelines present substantial challenges due to the difficulty in accessing these structures. Traditional nondestructive evaluation [NDE] techniques, including closed-circuit television (CCTV), ground penetrating radar (GPR), and eddy current analysis, often require intrusive setup or are limited in their ability to detect specific material types or fine leakage conditions, especially in mixed material systems. These existing methods may suffer from low resolution, high operational costs, or environmental sensitivity that compromises their reliability. Accordingly, there remains a need for a non-invasive, reliable, and field-deployable method for both identifying pipeline material and detecting leakage with minimal site disturbance.SUMMARY OF THE EMBODIMENTS

[0002] A nondestructive evaluation system and method are provided for detecting the material type and leakage of an underground service line. An impactor applies a controlled impact to an instrumented rod in contact or proximity with the service line, inducing stress waves that propagate into the service line and surrounding soil. Sensors on the rod and / or on the ground surface detect the resulting waveforms. A processing unit analyzes time and frequency domain characteristics such as wave speed, attenuation, and vibration response to determine service line material and identify anomalies associated with leakage. The system enables accurate, real-time diagnostics of buried pipelines without excavation or fluid interruption.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] FIG. 1 shows a view of the system in use on underground pipelines.

[0004] FIG. 2 left side shows the impact on the instrumented rod, and the right side shows sensors installed on the surface aligned along the buried service line.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0005] FIG. 1 shows a non-destructive system and method that uses stress wave technology to predict the material of pipelines buried beneath the ground surface. FIG. 1shows generally an above-ground area 102, a below-ground area 104, a building structure 110 having an above-ground portion 112 and at least a partially below-ground portion 114. The building structure 110 has an above-ground wall 112a and at least partially belowground wall or foundation 114a.

[0006] In the below-ground area 102, a service line 120 of unknown material may carry fluid to and / or from a building structure 110 and other valves like, for example, a curb stop valve 122, which is a shutoff valve located near a curb, typically between main line (not shown) and the building structure 110. The curb stop valve 122 allows utility workers or plumbers to turn off service to a property without entering the building structure 110. It's usually housed in a curb box for access from the above-ground area 102.

[0007] When using the system, an impactor 150, which could be a type of mechanical hammer that may impact an instrumented rod 160 with a pre-determined force, causing stress waves to travel along the instrumented rod 160 through the ground as exiting stress waves 162 and return from the service line 120 as service line stress waves 164. Once the rod 160 is excited, the resulting stress waves travel through its length, partially transmitting into the pipe network via the curb stop valve 122 or meter connection, and partially reflecting within the rod itself. The reflected waveforms inside the rod 160 are shaped by the mechanical impedance mismatch between the rod 160 and the service line 120, which is governed by the pipe material and geometry. As such, the reflected signal contains valuable information about the pipe's mechanical properties.

[0008] For example, the service line stress waves 164 vibrate differently for pipes of different materials. Service line stress waves propagate along buried pipelines 120 and wave energy leaks into the ground to reach the surface where vibrations are detected by wave-detecting sensors 170, 172. These sensors 170, 172 may be highly sensitive and are capable of capturing both transient and steady-state vibrations, enabling two primary diagnostics: (1) estimation of pipeline material based on wave propagation dynamics, and (2) identification of anomalies that suggest leakage. Since wave propagation changes for pipes of different materials, signal processing done at a CPU 190 (wherein may reside a data acquisition system and comparator), can be used to predict the pipe materials. As noted, same surface sensors, 170 and 174, can capture the waves caused by leakage occurring in pipelines, which may have different characteristics than those caused by merely material properties.

[0009] An impact from an instrumented hammer (manual or automated) 150 on the instrumented extension rod 160 may also serve the purpose of "exciting" the curb stop valve (or other pipe connections that can be easily accessed, such as at meter boxes) 122. Due to the impact, stress waves are generated and travel first along the extension rod 160, where they may be partially reflected within the road 103 and partially transmitted to the buried service line 120. The waves traveling along the service line 120 then leak and dissipate their energy into the surrounding soil below ground to the sensors 170 and 172.

[0010] Different wave propagation mechanisms and consequent vibrations can be leveraged to A) estimate what material the buried pipes are made of, and B) uncover the presence of pipeline leakage.

[0011] ESTIMATION OF PIPE MATERIAL

[0012] Once the impactor 150 hits the instrumented rod 160, the stress waves generated propagate along the rod, the service line 120, and leak their energy into the soil.

[0013] Estimating material using rod vibrations

[0014] A portion of the waves becomes confined within the rod 160, bouncing (reflecting) up and down multiple times, ultimately causing vibrations. These vibrations are detected by rod sensors 161, such as accelerometers and microphones installed on the rod 160. A load cell of the impactor 150 may measure the force impact on the rod 160.

[0015] The strength of the initial reflected wave at the bottom of the rod 160 depends on the ratio of rod stiffness to pipeline stiffness. Normalizing the signal strength by the impact force allows us to predict the material of the pipe 120.

[0016] The vibrations resulting from multiple wave reflections within the rod 160 can be analyzed using modal analysis, time-frequency analysis and other signal processing tools. The stiffness of pipes 120 connected to the curb stop valve 122 or meter in contact with the rod affects its vibration characteristics. For example, a plastic service line will be more compliant, while metal pipes create a stiffer boundary for the rod. Vibrations can be normalized by the force applied during impact, estimated by a dedicated load cell in the instrumented hammer.

[0017] Signal processing techniques are employed to analyze the rod's response, providing modal properties such as frequency response functions, mode shapes, resonance frequencies, and damping characteristics. These properties are influenced by the stiffness of the pipes with which the rod is in contact. These dynamic properties are then utilized to predict the material of the buried pipes.

[0018] Stress waves traveling along the rod 160 also propagate into the service line 120 and leak energy into the soil. Sensors 170, 172 placed at the ground surface can detect oscillations caused by the leaked waves 164. The wave propagation phenomenon is affected by many factors such as pipe geometry, material, depth, soil properties, surface materials [asphalt, concrete, grass, etc.). For instance, waves will travel at different speeds through pipes of different materials. Attenuation of the waves is also affected by different pipe material properties and can be used together with wave speed to identify the pipe material [see US Published Patent Application 2024 / 0410860, Ser. No. 18 / 695,147, filed March 25, 2024, which is incorporated by reference as if fully set forth herein). However, to predict the material the pipe is made of, the entirety of the signal and all its features sensitive to changing pipe materials [not only speed and attenuation) may be used, through careful analysis of stress waves via signal processing.

[0019] For material identification, the system analyzes a variety of vibratory characteristics such as mode shapes, natural frequencies, wave velocities, damping ratios, and frequency-dependent attenuation. These may be derived from time-domain and frequency-domain transformations of the sensor signals. Machine learning or pattern recognition algorithms may also be applied to classify material type against a trained database of known signatures.

[0020] To estimate the buried pipe material, the system may examine waveforms captured both at the instrumented rod and at surface-level sensors. Rod-based measurements may provide information on the mechanical impedance boundary conditions, which differ based on the stiffness, mass density, and cross-sectional geometry of the service line. For instance, copper and galvanized steel lines will yield stiffer boundary reflections compared to plastic lines like PVC or PEX.

[0021] Surface sensor data readings may capture wave transmission effects such as speed, amplitude, and dispersion. Pipe material significantly affects wave propagation speed (e.g., metal vs. plastic), which can be accurately calculated from time-of-arrival differences between sensors at known distances. Attenuation patterns may further help distinguish between high-damping and low-damping materials. These extracted features can be compared to a reference database, which may include simulated and field-tested profiles, to infer the most probable pipe material type.

[0022] In certain implementations, machine learning classifiers trained on labeled waveform data can automatically categorize the detected material. The use of features suchas peak frequency, energy content, and waveform symmetry may improve the accuracy of material estimation, even in noisy or complex subsurface environments.

[0023] Pipeline leakage detection

[0024] As shown in FIG. 2, the surface sensors 170, 172, as well as the instrumented rod sensors 161, are quite sensitive and can detect extremely small vibrations (even in the absence of an impact on the rod), such as those caused by pipeline leakage. It is expected that, in the absence of traffic or other sources of noise, the signals collected by the sensors will have amplitudes within an expected threshold, and the frequency content of the signals will exhibit nominal, expected features. In the presence of leakage (which can be continuous or represented by an outburst of sound energy), the sensors will detect noise that exceeds standard thresholds, and signatures associated with pipe leakage will appear in the sensor signals.

[0025] In FIG. 2, the bottom of the rod 160 is in contact with the curb stop valve 122 that connects service lines 120 from the main to a house; the instrumented rod 160 has sensors 161 that can detect rod vibration; and the sensors 170, 172 installed on the surface have been aligned along the buried service line.

[0026] EMBODIMENTS

[0027] Embodiment 1. A nondestructive evaluation method for determining a leakage in a below ground service line (120) comprising:

[0028] inserting a rod (160) with a wave measurement device therein into an area corresponding to a location of a service line;

[0029] generating a wave in the service line (120) through an exposed portion of the service line using a vibratory shaker or other wave generation device (150);

[0030] detecting, by the wave measurement device (170, 172), at least two substrate waves created by the service line wave passing through the service line and into a substrate;

[0031] identifying, by a data acquisition system, a velocity and an attenuation of the service line wave using the detected at least two substrate waves;

[0032] comparing the velocity and attenuation of the service line wave to a known set of wave velocities and attenuations corresponding to undamaged service lines; and

[0033] identifying damage in the service line by comparing the velocity and attenuation of the service line wave with the known set of wave velocities and attenuations corresponding to undamaged service lines.

[0034] Embodiment 2. The nondestructive evaluation method of embodiment 1, wherein the detecting is done using more than one probe.

[0035] Embodiment 3. The nondestructive evaluation method of embodiment 2, wherein at least two probes are spaced at a distance from one another.

[0036] Embodiment 4. The nondestructive evaluation method of embodiment 3, wherein a first probe and a second probe of the probes detect the substrate wave at different times.

[0037] Embodiment 5. The nondestructive evaluation method of embodiment 2, wherein the wave measurement devices comprise accelerometers.

[0038] Embodiment 6. The nondestructive evaluation method of embodiment 5, wherein the accelerometers are located within a protective sheath.

[0039] Embodiment 7. The nondestructive evaluation method of embodiment 1, wherein the generation of a service line wave is done using a vibratory shaker attached to the service line.

[0040] Embodiment 8. The nondestructive evaluation method of embodiment 1, wherein the service line wave has a frequency of between 0.01 kHz to 1,000 kHz and above.

[0041] Embodiment 9. The nondestructive evaluation method of embodiment 1, wherein an amplitude of the service line is adjusted.

[0042] Embodiment 10. A system for non-invasive detection of material type and leakage in a buried service line (120), comprising: an impactor (150) configured to impart a stress wave into an instrumented rod (160) in contact with a curb stop valve (122) or other pipe access point; a plurality of surface sensors (170, 172) configured to detect stress waves leaking from the buried service line (120); and a data acquisition and processing unit configured to analyze vibrations and waveforms from both the rod (160) and the surface sensors (170, 172) to identify the buried service line material and detect leakage.

[0043] Embodiment 11. The system of embodiment 10, wherein one or more sensors(161) located on the rod (160) detect rod vibrations sensors (161) comprise at least one accelerometer and one microphone.

[0044] Embodiment 12. The system of embodiment 10, wherein the surface sensors(170, 172) are aligned along an expected path of the service line (120) and are capable of detecting vibration signatures indicative of leakage.

[0045] Embodiment 13. The system of embodiment 10, further comprising a load cell coupled to the impactor (150) to measure the force imparted to the rod (160).

[0046] Embodiment 14. A method for identifying pipe material in an underground service line (120), comprising: impacting an instrumented rod (160) coupled to a curb stop valve (122); measuring vibrations within the rod using sensors (161); normalizing vibration signals using an impact force; analyzing the rod vibrations to determine dynamic modal properties indicative of pipe stiffness; and predicting the service line material based on the dynamic modal properties.

[0047] Embodiment 15. The method of embodiment 14, wherein the dynamic modal properties include frequency response functions, resonance frequencies, and damping ratios.

[0048] Embodiment 16. The method of embodiment 14, wherein predicting the pipe material comprises comparing measured properties to stored reference profiles for known pipe materials.

[0049] Embodiment 17. A system for leakage detection in a buried pipeline (120), comprising: a set of geophones or accelerometers (170, 172) placed along the surface above the pipeline; a processor configured to receive vibration signals from the geophones; and a leakage detection module that compares received signals against noise threshold levels to identify anomalies indicative of leakage.

[0050] Embodiment 18. The system of embodiment 17, wherein the leakage detection module uses spectral analysis to identify characteristic frequencies of leakage noise.

[0051] Embodiment 19. The system of embodiment 17, wherein the processor is further configured to ignore transient environmental noise using time-domain filtering.

[0052] While the invention has been described with reference to the embodiments above, a person of ordinary skill in the art would understand that various changes or modifications may be made thereto without departing from the scope of the claims.

Claims

CLAIMS1. A nondestructive evaluation method for determining a leakage in a below ground service line (120) comprising: inserting a rod (160) with a wave measurement device therein into an area corresponding to a location of a service line; generating a wave in the service line (120) through an exposed portion of the service line using a vibratory shaker or other wave generation device (150); detecting, by the wave measurement device (170, 172), at least two substrate waves created by the service line wave passing through the service line and into a substrate; identifying, by a data acquisition system (190), a velocity and an attenuation of the service line wave using the detected at least two substrate waves; comparing the velocity and attenuation of the service line wave to a known set of wave velocities and attenuations corresponding to undamaged service lines; and identifying damage in the service line by comparing the velocity and attenuation of the service line wave with the known set of wave velocities and attenuations corresponding to undamaged service lines.

2. The nondestructive evaluation method of claim 1, wherein the detecting is done using more than one probe.

3. The nondestructive evaluation method of claim 2, wherein at least two probes are spaced at a distance from one another.

4. The nondestructive evaluation method of claim 3, wherein a first probe and a second probe of the probes detect the substrate wave at different times.

5. The nondestructive evaluation method of claim 2, wherein the wave measurement devices comprise accelerometers.

6. The nondestructive evaluation method of claim 5, wherein the accelerometers are located within a protective sheath.

7. The nondestructive evaluation method of claim 1, wherein the generation of a service line wave is done using a vibratory shaker attached to the service line.

8. The nondestructive evaluation method of claim 1, wherein the service line wave has a frequency of between 0.01 kHz to 1,000 kHz and above.

9. The nondestructive evaluation method of claim 1, wherein an amplitude of the service line is adjusted.

10. A system for non-invasive detection of material type and leakage in a buried service line (120), comprising: an impactor (150) configured to impart a stress wave into an instrumented rod (160) in contact with a curb stop valve (122) or other pipe access point; a plurality of surface sensors (170, 172) configured to detect stress waves leaking from the buried service line (120); and a data acquisition and processing unit (190) configured to analyze vibrations and waveforms from both the rod (160) and the surface sensors (170, 172) to identify the buried service line material and detect leakage.

11. The system of claim 10, wherein one or more sensors (161) located on the rod (160) detect rod vibrations sensors (161) comprise at least one accelerometer and one microphone.

12. The system of claim 10, wherein the surface sensors (170, 172) are aligned along an expected path of the service line (120) and are capable of detecting vibration signatures indicative of leakage.

13. The system of claim 10, further comprising a load cell coupled to the impactor (150) to measure a force imparted to the rod (160).

14. A method for identifying pipe material in an underground service line (120), comprising: impacting an instrumented rod (160) coupled to a curb stop valve (122); measuring vibrations within the rod using sensors (161); normalizing vibration signals using an impact force; analyzing the rod vibrations to determine dynamic modal properties indicative of pipe stiffness; and predicting the service line material based on the dynamic modal properties.

15. The method of claim 14, wherein the dynamic modal properties include frequency response functions, resonance frequencies, and damping ratios.

16. The method of claim 14, wherein predicting the pipe material comprises comparing measured properties to stored reference profiles for known pipe materials.

17. A system for leakage detection in a buried pipeline (120), comprising: a set of geophones or accelerometers (170, 172) placed along a surface above the pipeline; a processor (190) configured to receive vibration signals from the geophones; and a leakage detection module that compares received signals against noise threshold levels to identify anomalies indicative of leakage.

18. The system of claim 17, wherein the leakage detection module uses spectral analysis to identify characteristic frequencies of leakage noise.

19. The system of claim 17, wherein the processor is further configured to ignore transient environmental noise using time-domain filtering.

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