Patent ID: 12196714

DETAILED DESCRIPTION

The following detailed description is directed to technologies for providing high-resolution assessment of the condition of pipes of a fluid distribution down to the individual pipe stick. Water distribution mains may degrade in several ways. For example, metal pipe walls may corrode and become thinner and weaker (less stiff). Asbestos cement pipes lose calcium and the wall loses strength in time. The wall of pre-stressed concrete pipes gets weaker if the steel wires break. These degradations may cause hydraulic failure of the distribution system.

As described in, e.g., U.S. patent application Ser. No. 09/570,922, filed May 15, 2000, and issued as U.S. Pat. No. 6,561,032; U.S. patent application Ser. No. 11/156,573, filed Jun. 21, 2005, and issued as U.S. Pat. No. 7,328,618; and U.S. patent application Ser. No. 11/952,582, filed Dec. 7, 2007, and issued as U.S. Pat. No. 7,475,596, the disclosures of which are incorporated herein by this reference in their entireties, methods for assessing the condition of, e.g., predicting the stiffness and/or wall thickness of, pipes of a water or other fluid distribution system may rely on measuring the propagation velocity of sound (referred to herein as “acoustical propagation velocity”) in a given pipe segment. The acoustical propagation velocity may be determined by placing two acoustic or vibration sensors on the pipe, on associated appurtenances, or in contact with the fluid at known locations bracketing the pipe segment under test and generating an out-of-bracket sound. The sound propagates along the pipe segment reaching first the near acoustic sensor, i.e. the sensor closest to the sound generator, and then the far acoustic sensor. The signals from the two sensors are recorded, and signal processing is applied to estimate the time delay between the sound reaching the near and far sensors (i.e., the time it takes for the sound to travel from one sensor to the other).

With a known distance between the two acoustic sensors and the estimated time delay, the acoustical propagation velocity of the sound in the pipe segment under test may be determined. The measured acoustical propagation velocity may then be compared with a reference speed of sound for that specific pipe class and material, with any differences used to determine the condition of the target pipe segment. While these methods generally work well, only a general condition of the pipe segment bracketed by the two sensors as a whole is assessed, and not changes in condition of the pipe along the length of the segment on a local scale. Different sections of the pipe segment may be in different condition.

According to embodiments described herein, systems and methods for estimating the acoustical propagation velocity in one or more sections of a pipe segment may be implemented, providing pipe condition information with greater resolution. The concept relies on the fact that water pipes are traditionally made of several individual sections of pipe, or “pipe sticks,” with uniform and known length, such as around 20 ft., connected together to form the pipe segment. Each pipe joint between two adjacent pipe sticks presents a local increase in pipe diameter and wall thickness that results in a local variation of the acoustic impedance. This local change causes reflections of the sound induced in the pipe during condition testing to occur. A single acoustic sensor on the pipe can detect the reflections from two or more of these pipe joints, and by utilizing signal processing techniques described herein the timing of the reflections as detected by the acoustic sensor can be extracted from the recorded signals and the time between two consecutive reflections can be measured. Knowing the length of a pipe stick and the time delay between two consecutive reflections, the acoustical propagation velocity of the acoustic wave for a given pipe stick can be determined, and the condition of that particular pipe stick ascertained.

FIG.1and the following description are intended to provide a general description of suitable environments in which the embodiments described herein may be implemented. In particular,FIG.1shows an environment100for assessing the condition of pipes of a fluid distribution down to the level of the individual pipe stick, according to embodiments described herein. The environment100includes a portion of a pipe102of a fluid network, such as a main in a water or other fluid distribution system. According to embodiments, the pipe102comprises multiple pipe sticks104A-104E (referred to herein generally as “pipe stick104”). The pipe sticks104A-104E may generally be of uniform length and construction, and are connected together by pipe joints, such as joints106A-106D (referred to herein generally as “joint106”). The joints106may be integral to each pipe stick104, as shown in the figure, or comprise a separate pipe coupling or fitting. The fluid network may be partially or wholly subterraneous, or portions of the fluid network may be subterraneous, while other portions of the fluid network may be non-subterraneous (i.e., above ground). For example, the pipe102may be partially or wholly subterraneous, while valves, hydrants, and other appurtenances connected to the pipe may be accessible below ground and/or located above ground.

The environment100further includes at least one vibration or acoustic sensor108in acoustical communication with the pipe102. For purposes of this disclosure, a component or device being “in acoustical communication with” a pipe represents the component being directly or indirectly coupled to the pipe in such a way that vibrations, acoustical impulses, or other variations in pressure traveling through the pipe wall and/or the fluid in the pipe can be produced or sensed by the component. In some embodiments, the acoustic sensor108may comprise transducers or accelerometers attached directly to the outer wall of the pipe102or to a valve, hydrant or other appurtenance of the fluid distribution system in fluid communication with the pipe. The transducers or accelerometers may measure the instantaneous acceleration of the pipe wall or appurtenance from vibrations caused by the sound pressure in the pipe102. The measured acceleration of the wall constitutes an indirect measurement of sound pressure in the pipe102. In further embodiments, the acoustic sensor108may include hydrophones, transducers, accelerometers, or any combination of these and other sensors known in the art for measuring vibrations or acoustic signals.

Acoustical waves are introduced into the pipe102by an excitation source110at an “out-of-bracket” position, i.e., outside of a target pipe segment112for condition assessment. In some embodiments, the acoustical waves may comprise one or more acoustical impulses114, vibrations, or pressure waves generated in the fluid path of the pipe102. The excitation source110may represent any means suitable for the creation of an acoustical excitation in the pipe102, including a manually actuated device, such as manual excitation by a human using a hammer to strike the pipe wall, an above-ground appurtenance, or the ground above the subterraneous pipe. The excitation source may also represent a mechanical device, such as a motorized hammer or piston. In further embodiments, a continuous acoustic excitation source110with abroad frequency range (e.g., at least 100 Hz) may be utilized, such as a speaker, hydrophone, or fluid flow. According to further embodiments, the excitation source110is located outside the immediate proximity of the acoustic sensor108, e.g. at least 10 meters of separation, to avoid the sensor sensing multiple modes of vibration from the excitation.

When an acoustical wave, such as acoustic impulse114, are introduced in the pipe102by the excitation source110, the wave propagates longitudinally along the length of the pipe102at various speeds depending on the condition of each pipe stick104, as discussed above. The joints106between each pipe stick104cause reflections of the acoustic impulse114, such as reflection116B from joint106B, reflection116C from joint106C, and reflection116D from joint106D (referred to herein generally as “reflections116”), that travel longitudinally in the opposite direction from the acoustic impulse114.

The acoustic sensor108senses the acoustical impulse114and the reflections116in the pipe102and produces a signal representing the sensed pulses. A pipe assessment system130may then process and analyze the signal data from the acoustic sensor108to assess the condition of the target pipe segment112, or more specifically the condition of the individual pipe sticks, such as pipe sticks104C and104D, contained within the target segment. According to embodiments, the pipe assessment system130extracts timing information regarding the acoustical impulse114and reflections116from the signal data from the acoustic sensor108. For example, the pipe assessment system130may utilize signal processing techniques described herein to determine the timing of the arrival of the acoustical impulse114(as shown at122A) and reflections116B-D (as shown at122B-D, respectively) at the longitudinal position of the acoustic sensor108along the pipe102, as shown in the graph120ofFIG.1.

From these timings, a time delay between arrival at the acoustic sensor108of consecutive reflections may be computed, such as time delay124C between arrival of reflections116B and116C and time delay124D between arrival of reflections116C and116D. Utilizing the computed time delays124C and124D and the known lengths126C and126D of the pipe sticks104C and104D, respectively, the acoustic propagation velocities within each pipe stick may be computed and the condition of the pipe sticks104C and104D estimated. It will be appreciated that the target pipe segment112may encompass any number of pipe sticks104of which the pipe assessment system130may estimate the condition, depending on the frequencies and maximum propagation length of the acoustical wave. Attenuation of the reflections116traveling along the pipe102may practically limit the total length of the segment to 200 m for accurate condition assessment.

Generally, the pipe assessment system130represents a collection of computing resources for the processing and analysis of the signal data received from one or more acoustic sensors108and the determination of pipe condition. According to embodiments, the pipe assessment system130may comprise one or more computer devices and/or computing resources connected together utilizing any number of connection methods known in the art. For example, the pipe assessment system130may comprise a mobile computer device, such as a laptop or tablet, deployed in the field in proximity to the target pipe segment112. Alternatively or additionally, the pipe assessment system130may comprise laptop or desktop computers; tablets, smartphones or mobile devices; server computers hosting application services, web services, database services, file storage services, and the like; and virtualized, cloud-based computing resources, such as processing resources, storage resources, and the like, that receive the signal data from the acoustic sensors108through one or more intermediate communication links or networks.

According to embodiments, the pipe assessment system130includes one or more processor(s)132. The processor(s)132may comprise microprocessors, microcontrollers, cloud-based processing resources, or other processing resources capable of executing instructions and routines stored in a connected memory134. The memory134may comprise a variety non-transitory computer-readable storage media for storing processor-executable instructions, data structures and other information within the pipe assessment system130, including volatile and non-volatile, removable and non-removable storage media implemented in any method or technology, such as RAM; ROM; FLASH memory, solid-state disk (“SSD”) drives, or other solid-state memory technology; compact disc ROM (“CD-ROM”), digital versatile disk (“DVD”), or other optical storage; magnetic hard disk drives (“HDD”), hybrid solid-state and magnetic disk (“SSHD”) drives, magnetic tape, magnetic cassette, or other magnetic storage devices; and the like.

In some embodiments, the memory134may include an acoustic analysis module136for performing the acoustic analysis of the signal data from the acoustic sensors108to perform high-resolution assessment of the pipe102down to the individual pipe stick104, as described herein. The acoustic analysis module136may include one or more software programs, components, and/or modules executing on the processor(s)132of the pipe assessment system130. The acoustic analysis module136may further include hardware components specifically designed to perform one or more steps of the routines described herein. According to further embodiments, the memory134may store processor-executable instructions that, when executed by the processor(s)132, perform some or all of the steps of the routines200and500described herein for providing high-resolution assessment of the condition of pipes of a fluid distribution down to the individual pipe stick, as described in regard toFIGS.2and5.

The pipe assessment system130may be in direct communication with the acoustic sensor(s)108over a wired connection or may be indirectly connected to the sensors through one or more intermediate communication links and/or computing devices. For example, a laptop may be connected to the acoustic sensor(s)108via one or more radio-frequency (“RF”) links to receive signal data from the sensors in real-time. In other embodiments, the signal data from an acoustic sensor108may be received by an individual computing device (referred to as a “node”) and sent to a central analysis computer for processing and analysis. In such embodiments, it may be necessary to ensure that the clocks of the individual nodes are synchronized or share a highly accurate time source in order to ensure accurate timing accompanies the signal data from respective acoustic sensor(s)108.

According to some embodiments, the processor(s)132are operatively connected to acoustic sensor(s)108through a sensor interface138. The sensor interface138allows the processor(s)132to receive the signals from the sensors representative of the sensed acoustical waves and reflections116in the pipe102. For example, the sensor interface138may utilize one or more analog-to-digital converters (“ADCs”) to convert an analog voltage output of the acoustic sensor(s)108to a digital value that is sampled by the processor(s)132at a specific sampling rate sufficient to represent the acoustical waves and reflections116in the signal data. According to some embodiments, a sampling rate around 10 kHz may be utilized to capture data representing the frequencies of interest in the pulses. In further embodiments, a sound processing unit or “sound card” of the laptop computer may be utilized to provide the sampling functionality.

It will be appreciated that the structure and/or functionality of the pipe assessment system130may be different than that illustrated inFIG.1and described herein. For example, one or more of the processor(s)132, memory134, sensor interfaces138, and/or other components and circuitry described may be integrated within a common integrated circuit package or distributed among multiple integrated circuit packages in one or more computing devices. In some embodiments, some or all of the processing and analysis described herein may be implemented as software applications on mobile computing platforms, such as a smartphone or laptop with cellular networking capability. Similarly, the illustrated connection pathways are provided for purposes of illustration and not of limitation, and some components and/or interconnections may be omitted for purposes of clarity. It will be further appreciated that pipe assessment system130may not include all of the components shown inFIG.1, may include other components that are not explicitly shown inFIG.1, or may utilize architectures completely different than those shown inFIG.1.

FIG.2illustrates one routine200for performing high-resolution assessment of the condition of pipes of a fluid distribution down to the individual pipe stick, according to some embodiments. In some embodiments, parts of the routine200may be performed by the acoustic analysis module136executing on a laptop computer in direct connection with an acoustic sensor108associated with a target pipe segment112containing one or more pipe sticks, such as pipe sticks114C and114D shown inFIG.1, for condition assessment. In other embodiments, the routine200may be performed by some combination of the processor(s)132, computing devices, components, and modules of the pipe assessment system130in conjunction with parameters, data, and/or instructions provided with maintenance personnel associated with the fluid distribution system.

The routine200begins at step202, where an acoustic sensor108is placed at one end of the target pipe segment112encompassing the pipe sticks104for condition assessment. The acoustic sensor108may be placed on an exposed section of the pipe102and/or a readily accessible appurtenance, such as a valve, hydrant, or the like. The acoustic sensor108may be connected to the pipe assessment system130either wirelessly or wired, or the acoustic sensor may be indirectly connected to the pipe assessment system through one or more intermediate computing devices or nodes connected to the pipe assessment system via a network.

Next, the routine200proceeds from step202to step204, where an excitation of the pipe102by an excitation source110is performed while signal data from the acoustic sensor108is recorded by the pipe assessment system130. According to embodiments, the location of the excitation along the pipe102is out-of-bracket of the target pipe segment112at some distance from the acoustic sensor108, e.g. at least 10 meters from the sensor, to avoid the sensor sensing multiple modes of vibration from the excitation. As described above, the excitation introduces an acoustical wave into the pipe102that propagates longitudinally along the length of the pipe and it is observed by the acoustic sensor108. In addition, the sound wave travels further through the pipe102and is reflected by the joints106connecting adjacent pipe sticks104. The reflections116propagate in the pipe102in opposite direction reaching the acoustic sensor108after a certain time delay.

From step204, the routine200proceeds to step206, where the pipe assessment system130processes the signal data recorded from acoustic sensor108to extract timing information regarding the arrival of the reflections116at the sensor. For example, the pipe assessment system130may utilize a variety of signal processing techniques based on pulse reflectometry to ascertain the times of arrival at the acoustic sensor108of the reflection116B from the joint106B, the reflection116C from the joint106C, and the reflection116D from the joint106D. For example, the pipe assessment system may utilize signal conditioning and auto-correlation processes such as those described herein in regard toFIGS.5and6.

The routine200proceeds from step206to step208, the pipe assessment system130utilizes the timing information to measure time delays between the arrival of consecutive reflections116at the acoustic sensor108. For example, the pipe assessment system130may measure the time delay124C between arrival of reflections116B and116C and time delay124D between arrival of reflections116C and116D. Next, as step210, the pipe assessment system130utilizes the computed time delays and the known lengths of the pipe sticks to compute an acoustical propagation velocity associated with each pipe stick104in the target pipe segment112. For example, the pipe assessment system130may determine the acoustical propagation velocity cnin pipe stick n, such as pipe sticks104C and104D using the computed time delays Δtn, such as time delays124C and124D, and the respective lengths ln, such as lengths126C and126D, utilizing the following formula:

cn=2⁢lnΔ⁢tn

The routine200then proceeds from step210to step212, where the pipe assessment system130associates the acoustical propagation velocities cncomputed for each pipe stick104with a condition of the pipe stick. For example, the acoustical propagation velocity computed for the pipe stick104may be compared with a reference speed of sound for that specific pipe class and material, with any differences used to determine the condition of the section. From step212, the routine200ends.

FIG.3shows additional aspects of utilizing pulse reflectometry in the environment100described above to assess the condition of pipes in a fluid distribution system down to the individual pipe stick. Conventional methods of utilizing pulse reflectometry generally rely on the sound being induced in a unique direction, so that all the reflections are coming from object(s) under test. As described above in regard toFIG.1, when an acoustical wave, such as acoustic impulse114, is introduced in the pipe102by the excitation source110, the impulse propagates along the length of the pipe102upstream to the acoustic sensor108and beyond, denoted as PuinFIG.3. The reflections116from upstream joints between pipe sticks104, such as pipe joints106B and106C, travel back to the acoustic sensor108in the opposite direction, denoted as Ru(1) and Ru(2), respectively. The acoustic sensor108senses the reflections Ru(1) and Ru(2) and the timings of the arrival of these reflections at the sensor can be determined by the pipe assessment system130from the signal data received from the sensor.

It will be appreciated, however, that the acoustic impulse114will also propagate through the pipe102in the downstream direction as well, denoted inFIG.3as Pd. Reflections116from any downstream joints, such as pipe joints106M and106N, will also travel back to and be sensed by the acoustic sensor108, as denoted by Rd(1) and Rd(2), respectively. Because the reflections Rd(1) and Rd(2) travel a similar distance to reflections Ru(1) and Ru(2), they will present similarly in the signal data to the useful ones. The periodicity of the reflections Rd(1) and Rd(2) will also be similar to the useful reflections Ru(1) and Ru(2), as the downstream pipe sticks104are very likely of the same type and length as the upstream pipe sticks for which condition assessment is desired. Thus the presence of downstream reflections116, such as reflections Rd(1) and Rd(2), may limit the ability of the pipe assessment system130to extract accurate timing information regarding the useful reflections Ru(1) and Ru(2) needed for accurate estimation of condition of the target pipe sticks104. To address this problem, signal data from additional acoustic sensor(s)108and/or recordings from additional excitation locations may be utilized to reduce the influence of undesirable downstream reflections in the signal data, as shown inFIGS.4A and4Band described below.

In some embodiments, the environment100may further include an additional acoustic sensor108B placed in acoustical communication with the pipe102and connected to pipe assessment system130, as shown inFIG.4A. The target pipe segment112containing the pipe sticks, such as pipe stick104C and104D, for condition assessment is bracketed by the first and second acoustic sensors108A and108B. As described above in regard toFIG.3, an acoustic impulse114introduced in the pipe102by the excitation source110propagates upstream and downstream along the length of the pipe (e.g., Puand PdfromFIG.3), reaching the first acoustic sensor108A and then the second acoustic sensor108B. Reflections116of the acoustic impulse114from upstream joints106B-106D associated with the pipe sticks104C,104D for which condition assessment is desired (e.g., Ru(1) and Ru(2)) propagate in the opposite direction back to the first acoustic sensor108A. Reflections116of the acoustic impulse114from any downstream joints, such as joint106M, propagate back to the first acoustic sensor108A and then to second acoustic sensor108B.

The signal recorded from the first acoustic sensor108A should have an impulse response function h1(t) of:
h1(t)=p(t)+ru(t)+rd(t)
where p(t) is a portion of the signal contributed by the generated acoustic impulse114, ru(t) is a portion of the signal contributed by the reflections116from upstream joints (the “useful” reflections), and rd(t) is a portion of the signal contributed by the reflections from downstream joints (the “undesirable” reflections). Similarly, the impulse response function h2(t) for the signal recorded at the second acoustic sensor108B may be expressed as:
h2(t)=α(p(t)+rd(t))
where p(t) and rd(t) are the same signal components as in h1and α is an attenuation factor to account for attenuation of the pulses travelling to the far sensor.

The representation of the signal of interest ru(t) for the extraction of the timing information to perform condition assessment of the pipe sticks104B and104C, therefore, may be obtained by normalizing the signals h1(t) and h2(t) and then subtracting the two signals, i.e.:

ru(t)=h1(t)-h2(t)α
with the component rd(t) representing the signal contributed by the undesirable reflections removed. This assumes a same attenuation factor α for both the acoustical impulse114and the downstream reflections116. In some embodiments, the attenuation factor may be determined directly by a comparison of the acoustic impulse as received by the respective acoustic sensors108A and108B. In other embodiments, the attenuation may be predetermined through experimentation based on the length L, type, material, and/or expected condition of the target pipe segment112or through other acoustic attenuation models known in the art.

According to further embodiments, to reduce the influence of undesirable downstream reflections affecting the extraction of the timing information, the generation of the acoustic impulse114and recording of signal reflections116may be performed in two directions, as shown inFIG.4B. The pipe102is excited by the excitation source110at a first out-of-bracket location402A and the signal data is recorded at the acoustic sensor108positioned at a first end of the target pipe segment112, as described above. The impulse response function h(t) for the resulting signal recorded at the acoustic sensor108during the first excitation is expressed as:
h(t)=p1(t)+ru(t)+rd(t)
where p1(t) is a portion of the signal contributed by the generated acoustic impulse114at the first position, ru(t) is a portion of the signal contributed by the reflections116from upstream joints (the useful reflections), e.g., joints106B-106D, and rd(t) is a portion of the signal contributed by the reflections from downstream joints (the undesirable reflections), e.g. joint106M, as described above.

The acoustic sensor108may then be moved to the other end of the target pipe segment112, and the pipe excited at a second out-of-bracket location402B generating acoustical impulses traveling in opposite directions (with reference to the directions labeled “upstream” and “downstream” herein) from those generated at the first location402A. The impulse response function g(t) for the signal recorded at the acoustic sensor108during the second excitation can be expressed as:
g(t)=p2(t)+su(t)+sd(t)
where p2(t) is a portion of the signal contributed by the acoustic impulse114generated at the second location402B, su(t) is a portion of the signal contributed by the reflections116from upstream joints (the reflections of interest), e.g., joints106D-106B, and sd(t) is a portion of the signal contributed by the reflections from downstream joints (the undesired reflections), e.g. joint106F.

Therefore, the section of interest from the two recordings taken during excitation at the two out-of-bracket locations402A and402B is represented by components ru(t) and su(t), respectively, and it will be appreciated that the component ru(t) should be substantially similar to the time-reversed component su(t) over the target pipe segment112. In other words:
ru(t)≈su(−t)
Expressing these components in terms of the distance x from the first end of the target pipe segment112(i.e., the location of the acoustic sensor108for the first excitation) and the speed of sound c instead of time t, we get:

ru(t)=ru(2⁢xc)⁢su(-t)=su(2⁢Lc-2⁢xc)⁢ru(2⁢xc)≈su(2⁢Lc-2⁢xc)

According to some embodiments, the similar components of interest ru(t) and su(−t) characterizing the target pipe segment112under test can be extracted by cross-correlating the impulse response function h(t) in the signal data recorded during the excitation at the first location402A with the time-reversal of the impulse response function g(t) in the signal data recorded during the excitation at the second location402B. It is noted that the cross-correlation of h(t) with time-reversed g(t), is mathematically equivalent with the convolution of the two signals. An alternative way to emphasize the component of interest in the signal data is to simply add the impulse response h(t) with the time-reversed impulse response g(t), or g(−t), after aligning h(t) and g(−t) utilizing the propagation delay of the acoustic impulse114along the segment under test. This should result in the amplitude of the peaks in the signal data representing the reflections of interest being doubled. It will be further appreciated that the method of utilizing two excitations at two out-of-bracket locations402A and402B described in regard toFIG.4Bcould be combined with the method of utilizing two acoustic sensors108A and108B described in regard toFIG.4Ato further reduce the influence of undesirable downstream reflections affecting the extraction of the timing information.

In order to isolate the component(s) of interest for the extraction of timing information utilizing the methods described above, the impulse response functions, e.g., h1(t), h2(t), g(t), etc., need to be accurately estimated. According to some embodiments, the impulse response could be given by the transfer function between the signal recorded at the acoustic sensor(s)108and a prototypical acoustic impulse created by the excitation(s). For example, a reference bank of prototypical acoustic impulses created by different excitation sources110on pipes102of different types may be maintained in the memory134of the pipe assessment system130. The acoustic analysis module136may select a prototypical acoustic impulse from the reference bank based on a type of the pipe102, e.g., concrete or metal, and/or a type of the excitation source110, e.g., hammer on pipe surface vs. ground impact, and used in the transfer function to derive an impulse response function from the signal(s) recorded at the acoustic sensor(s)108.

In other embodiments, it can be assumed that the auto-correlation of the signal(s) represented in the signal data is representative of the underlying impulse response. While the auto-correlation of the signal(s) may not yield an exact representation of the impulse response, it emphasizes the reflections caused by different pipe appurtenances, including pipe joints106. However, using the auto-correlation signal to estimate the impulse response may present oscillations caused by the band-limited nature of the signal that do not represent the structure of the pipe. Utilizing an auto-correlation envelope removes these inherent oscillations, however, and presents the signal variation of interest for extracting the timing information. It will also be necessary to remove the contribution of the generated acoustic impulse114, which will be dominant in the auto-correlation function. From the auto-correlation envelope (also referred to herein as “acoustic profiles”), time delay estimates may be found using the cross-correlation of the two signals, the time-of-flight estimate, or other methods known in the art.

FIG.5illustrates another routine500for performing high-resolution assessment of the condition of pipes down to the individual pipe stick utilizing signal data from additional acoustic sensor(s)108and/or recordings from additional excitation locations to reduce the influence of undesirable downstream reflections in the signal data, according to some embodiments. In some embodiments, parts of the routine500may be performed by the acoustic analysis module136executing on a laptop computer in direct connection with one or more acoustic sensors, such as acoustic sensors108A and108B, associated with a target pipe segment112. In other embodiments, the routine500may be performed by some combination of the processor(s)132, computing devices, components, and modules of the pipe assessment system130in conjunction with parameters, data, and/or instructions provided with maintenance personnel associated with the fluid distribution system.

The routine500begins at step502, where two acoustic sensors108A and108B are placed at either end of a target pipe segment112containing one or more pipe sticks, such as pipe sticks114C and114D shown inFIG.1, for condition assessment. The acoustic sensors108A and108B may be placed directly on an exposed section of the pipe and/or any readily accessible appurtenance, such as valves, hydrants, or the like. As described above, the acoustic sensors108A and108B may be connected directly to the pipe assessment system130, either wirelessly or wired, or the acoustic sensors may be indirectly connected to the pipe assessment system through one or more intermediate computing devices or nodes connected to the pipe assessment system via a network.

According to some embodiments, one or more of the acoustic sensors108A and108B may already be in place, attached to the pipe102, valves, or hydrants as part of a leak detection and condition monitoring system for the fluid distribution system. In further embodiments, the fluid distribution system may be a served by a GIS or geospatial mapping system that contains the locations of all pipes, valves, hydrants, meters, etc. in the fluid distribution system. The GIS or geospatial mapping system may allow the selection of the target pipe segment112of the pipe102to be bracketed by the acoustic sensors108A and108B, the appurtenances bracketing the segment of pipe to which to attach the sensors, the target pipe segment112and/or pipe sticks104for which condition assessment is desired, the associated excitation locations402A and402B along the pipe102, and the like. From these selections, parameters such as type and lengths of the target pipe sticks104, distances from the acoustic sensors108A and108B to the pipe joints106, precise GPS coordinates of excitation locations402, and the like can be provided to the pipe assessment system130and/or field personnel performing the condition assessment(s), as described herein.

Next, the routine500proceeds from step502to step504, where the pipe102is excited by an excitation source110at a first out-of-bracket location while signal data from the two acoustic sensors108A and108B is recorded by the pipe assessment system130. According to embodiments, the location of the first excitation may be located out-of-bracket from the target pipe segment112bracketed by the first acoustic sensor108A (also referred to herein as the “near acoustic sensor”) and the second acoustic sensor108B (also referred to herein as the “far acoustic sensor”), such as location402A shown inFIG.4B. In some embodiments, the location of the excitation source110is located some distance, e.g., at least 10 meters, from the near acoustic sensor108A, to avoid the sensor sensing multiple modes of vibration from the excitation. Excitation of the pipe102at this first excitation location402A may be performed by tapping an outer wall of the pipe102or appurtenance using a hammer or other impact device, by pounding the ground above the crown of the subterraneous pipe, or by some other excitation means.FIG.7shows an example of a signal702recorded from one of the acoustic sensors108A,108B during such an excitation.

From step504, the routine500proceeds to step506, where the pipe assessment system130extracts an acoustic profile (also referred to as “first acoustic profile” or “acoustic profile—direction1”) from the signal data recorded at the acoustic sensors108A and108B utilizing the signal processing techniques described herein. For example, the pipe assessment system130may utilize the routine600shown inFIG.6to extract the acoustic profile from the corresponding signals reflected in the signal data recorded at the first and second acoustic sensors108A and108B. At step602, the pipe assessment system130normalizes the two signals to account for amplitude differences in the signals recorded from the near acoustic sensor108A and the far acoustic sensor108B from attenuation as the acoustic impulses114and reflections116travel longitudinally along the length of the pipe.

From step602, the routine600proceeds to step604, where the pipe assessment system130measures a propagation delay between the signal recorded at the first acoustic sensor108A and the signal recorded at the second acoustic sensor108B. The propagation delay may be measured utilizing conventional methods known in the art or any of the methods described in the patents incorporated herein by reference. For example, the propagation delay between the two signals may be measured by finding the time delay value corresponding to a peak in the cross-correlation function between the two signals. In further embodiments, the propagation delay between the two signals may be measured utilizing the time-of-flight method, the cross-phase method, or other methods known in the art to find the time delay between two signals.

The routine600proceeds from step604to step606, where the pipe assessment system130aligns the signal from the second acoustic sensor108B with the signal from the first acoustic sensor108A based on the measured propagation delay. The routine600then proceeds to step608, the pipe assessment system130subtracts the normalized and aligned signal from the second (far) acoustic sensor108B from the signal from the first (near) acoustic sensor108A resulting in a signal with the contribution of any undesirable downstream reflections (i.e., rd(t)) removed, as discussed above in regard toFIG.4A. It will be appreciated in methods of condition assessment where only one acoustic sensor108is utilized with each excitation, such as those described above in regard toFIGS.1,2, and4B, the pipe assessment system130may skip steps602through608of the routine600and utilize the recorded signal directly from the single sensor, such as the signal702shown inFIG.7, to determine the acoustic profile.

At step610, the pipe assessment system130computes the auto-correlation function for the resulting signal from step608(or the recorded signal from a single acoustic sensor108). The signal graph800A ofFIG.8shows an exemplary auto-correlation signal802. According to some embodiments, the pipe assessment system130then computes an envelope of the auto-correlation function using, e.g., a Hilbert transform, as shown at step612, as further shown in the signal graph800B. From step612, the routine600proceeds to step614, where the pipe assessment system130applies a de-trending filter to remove the contribution of the original acoustical wave (i.e., p(t)), such as the acoustical impulse114, and emphasize the signal components caused by reflections116. The influence of the acoustic impulse114is shown at the large peak806inFIG.8, while the smaller peaks808A-808D likely represent reflections of the impulse. For example, a high-pass filter with a cutoff frequency of 25 Hz could be used to remove the main trend in the auto-correlation envelope. The resulting de-trended auto-correlation envelope signal is then used to produce the acoustic profile.

In further embodiments, the routine600proceeds from step614to step616, where the pipe assessment system130trims the length of the acoustic profile signal (de-trended auto-correlation envelope) down to a time period containing the reflections of interest (i.e., ru(t)) from which the timing information for condition assessment of the pipe sticks104within the target pipe segment112may be obtained. For example, the acoustic profile may be trimmed to a time window starting at the acoustic impulse114and of sufficient length to include all reflections from upstream pipe joints106in the target pipe segment112, i.e. the length of time necessary for the impulse to travel from the near acoustic sensor108A to the far acoustic sensor108B and back (dt=2L/c).

From step616, the routine600ends with the extracted acoustic profile signal passed back to step506in routine500. It will be appreciated that other signal processing techniques known in the art in addition to or as an alternative to the steps of routine600may be utilized to extract an acoustic profile from the recorded signals that allows accurate timing information to be extracted for performing condition assessment of the pipe sticks104. It is intended that all such signal processing techniques be included in the scope of this application.

Returning toFIG.5, the routine500continues from step506to step508, where it is determined whether a second excitation in the opposite direction is to be used. As discussed above in regard toFIG.4B, the generation of the acoustical wave and recording of signal reflections116may be performed in two locations402A and402B in opposite directions to further reduce the contribution of undesirable downstream reflections (i.e., rd(t)) affecting the extraction of the timing information. If a second excitation is to be used, the routine500proceeds to step510, where the pipe102is excited by an excitation source110at the second out-of-bracket location402B while signal data from the two acoustic sensors108A and108B is recorded by the pipe assessment system130. According to embodiments, excitation of the pipe102at the second excitation location402B is performed in substantially the same fashion as excitation at the first location402A to produce comparable resulting signal(s) from the acoustic sensor(s)108. It will be noted for the second excitation at location402B the second acoustic sensor108B represents the “near” acoustic sensor and the first acoustic sensor108A represents the “far” acoustic sensor.

From step510, the routine500proceeds to step512, where the pipe assessment system130extracts a second acoustic profile (also referred to as “acoustic profile—direction2”) from the signal data recorded at the acoustic sensors108A and108B utilizing the same or similar signal processing techniques of routine600described above in regard toFIG.6. Because the second excitation location402B is located at the opposite end of the target pipe segment112from the first excitation location402A, the resulting second acoustic profile signal is time reversed at step514before combining the two profile signals, as discussed above in regard toFIG.4B. The second acoustic profile is then shifted to align the signal with the first acoustic profile signal using the propagation delay between the signal recorded at the first acoustic sensor108A and the signal recorded at the second acoustic sensor108B from the first excitation at step604of routine600, for example.

The routine500proceeds from step514to step516, where the first acoustic profile (related to the excitation at the first excitation location402A) and the second acoustic profile (related to the excitation at the second excitation location402B) are combined to enhance the component of the signal contributed by the reflections116from the upstream pipe joints106B-106D of the pipe sticks104C and104D in the target pipe segment112for condition assessment. As further discussed above in regard toFIG.4B, the first and second acoustic profiles may be combined by simply adding the first acoustic profile signal with the time-reversed and shifted second acoustic profile signal in order to double the amplitude of the peaks in the signal data representing the reflections of interest. In other embodiments, the first and second acoustic profiles may be combined by calculating the convolution of the two profile signals (without time-reversal or shifting of the second profile signal).

Next, the routine500proceeds from step516, or if an excitation at a second excitation location402B is not utilized, from step508, to step518, where the pipe assessment system130identifies periodic patterns in the peaks of the (combined) acoustic profile signal. The peaks in the profile signal (e.g., de-trended auto-correlation envelope) that follow a predictable periodicity are expected to represent reflections116(i.e. ru(t)) from upstream pipe joints in the target pipe segment112, such as joints106B-106D shown inFIGS.1,3,4A and4B. The expected frequency of the period patterns will be based on the length of the pipe sticks140C,104D and an estimate of the propagation velocity.FIG.9shows an example of a detrended acoustic profile (auto-correlation envelope) signal904with peaks904A-904K that occur in periodic patterns and likely represent the reflections116of interest from consecutive joints106B-106D.

According to some embodiments, the pipe assessment system130may apply a bandpass filter to the acoustic profile with a frequency range based on the uniform length l126C,126D of the pipe sticks104C,104D, e.g.:

fp⁢a⁢t⁢t⁢e⁢r⁢n∼c2⁢l
where c is an estimate of the propagation velocity, such as that determined in step604of routine600. The resulting passband signal will contain only peaks of interest representing reflections116from joints106B-106D in the target pipe segment112. In other embodiments, the pipe assessment system130may analyze portions of the acoustic profile signal corresponding in time to different sections of the target pipe segment112and extract a dominant frequency (e.g., via a Fourier transform) within the expected frequency range for the pipe in each section. The dominant frequency in each section can then be utilized to isolate the peaks of interest. Alternatively, the pipe assessment system130may iteratively apply an algorithm or set of rules to remove one or more peaks from the acoustic profile signal and evaluate the periodicity of the remaining peaks until the predicted patterns (expected frequency) emerges.

From step518, the routine500proceeds to step520, where the pipe assessment system130records the time delay Δtn124C,124D between consecutive local maxima (peaks with the periodic patterns) in the acoustic profile. From these time delays124C,124D, the acoustical propagation velocity cnin each pipe stick104C,104D within the target pipe segment112can be estimated using the formula:

cn=2⁢lnΔ⁢tn
where lnrepresents the length(s), such as lengths126C and126D, of pipe stick n. The pipe assessment system130may then associate the acoustical propagation velocities cncomputed for each pipe stick104C,104D with a condition of that pipe stick, as shown at step522. For example, the acoustical propagation velocity computed for the pipe stick104may be compared with a reference speed of sound for that specific pipe class and material, with any differences used to determine the condition of the section.

From step522, the routine500ends. It will be appreciated that the routines500and600shown inFIGS.5and6and described herein may be utilized to perform high-resolution assessment of the condition of pipes102down to the individual pipe stick104in systems containing one or two acoustic sensors108and utilizing one or two excitations, with the applicable steps skipped or repeated as necessary depending on the configuration of the testing system. The various steps may further be performed at different times and in different order than shown, based on the hardware utilized to excite the pipe102and record the signal data from the acoustic sensor(s)108. For example, field personnel may excite the pipe102at multiple, various excitation locations402associated with multiple target pipe segments112while recording signal data from appropriately placed acoustic sensors108. The signal data associated with the multiple target pipe segments112may be stored on the laptop and later transmitted over a network to a server computer in the pipe assessment system130, where the acoustic analysis module136performs condition assessment for one or more pipe sticks104contained in each target pipe segment. It is intended that all such variations in the inclusion/exclusion of and order of steps performed of the routines be included in this application.

While the embodiments described above and shown in the figures describe and depict a discrete acoustical impulse114propagating through the pipe102and reflections116therefrom, this is done for clarity of illustration and explanation, and it will be appreciated that the techniques and methodologies described herein are generally applicable to signals reflecting any sound comprising one or more acoustical impulses, vibrations, or pressure waves generated in the fluid path of the pipe by the excitation, including an acoustical wave generated from a continuous broad-band sound source. Further, while the figures and associated description show and describe a target pipe segment112containing three pipe joints106B-106D connecting two pipe sticks104C and104D for assessment, this is merely for clarity of explanation, and it will be appreciated that a target pipe segment112may contain any number of pipe sticks104, limited only by an amount of attenuation of the signals within the pipe segment reaching the acoustic sensor(s)108.

While the description focuses on measuring time delays between consecutive reflections, this analysis could be performed in the frequency domain as well. Further, while the described methods assess condition of individual pipe sticks104, the use of pulse reflectometry described allows for condition assessment at a resolution larger than one stick. For instance, the target pipe segment112may be analyzed for the periodicity of the auto-correlation envelope. A Fourier transform may show a dominant frequency caused by reflections116from pipe joints106within the target pipe segment112that informs on the average speed of sound for that segment.

Based on the foregoing, it will be appreciated that technologies for providing higher resolution assessment of the condition of pipes of a fluid distribution system by in-bracket excitation of the pipes in multiple locations are presented herein. The above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of the present disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the present disclosure. All such modifications and variations are intended to be included within the scope of the present disclosure, and all possible claims to individual aspects or combinations and sub-combinations of elements or steps are intended to be supported by the present disclosure.

The logical steps, functions or operations described herein as part of a routine, method or process may be implemented (1) as a sequence of processor-implemented acts, software modules or portions of code running on a controller or computing system and/or (2) as interconnected machine logic circuits or circuit modules within the controller or other computing system. The implementation is a matter of choice dependent on the performance and other requirements of the system. Alternate implementations are included in which steps, operations or functions may not be included or executed at all, may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present disclosure.

It will be further appreciated that conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more particular embodiments or that one or more particular embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment.