WO2023230651A2

WO2023230651A2 - Method and system for assessing pipeline condition

Info

Publication number: WO2023230651A2
Application number: PCT/AU2023/050457
Authority: WO
Inventors: Wei Zeng; Martin Francis LAMBERT; Jinzhe GONG; Si Tran Nguyen NGUYEN; Aaron C. ZECCHIN; Benjamin CAZZOLATO; Angus Ross SIMPSON
Original assignee: The University Of Adelaide
Priority date: 2022-05-30
Filing date: 2023-05-30
Publication date: 2023-12-07
Also published as: WO2023230651A3

Abstract

A method and system for assessing a condition of a pipeline network having a pipeline configuration is disclosed. The method and system comprises generating at a generation location a persistent micro- transient pressure signal in a fluid being conveyed by the pipeline network, measuring at a first measurement location on the pipeline network a first time varying pressure response signal and measuring at a second measurement location on the pipeline network a second time varying pressure response signal, the second measurement location spaced apart from the first measurement location, wherein the generation location, first measurement location and second measurement location define an assessment configuration. The method and system further comprises determining a composite impulse response function (IRF) for the pipeline network based on the first time varying pressure response signal and the second time varying pressure response signal and then assessing the condition of the pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration.

Description

METHOD AND SYSTEM FOR ASSESSING PIPELINE CONDITION

PRIORITY DOCUMENTS

[0001] The present application claims priority from Australian Provisional Patent Application No. 2022901460 titled “METHOD AND SYSTEM FOR ASSESSING PIPELINE CONDITION” and filed on 30 May 2022, the content of which is hereby incorporated by reference in its entirety.

INCORPORATION BY REFERENCE

[0002] The following publications are referred to in the present application and their contents are hereby incorporated by reference in their entirety:

International Patent Application No PCT/AU2009/001051 (W02010017599) titled “METHOD AND SYSTEM FOR ASSESSMENT OF PIPELINE CONDITION” in the name of Adelaide Research & Innovation Pty Ltd;

International Patent Application No PCT/AU2015/000415 (WO2017008098) titled “MULTIPLE TRANSDUCER METHOD AND SYSTEM FOR PIPELINE ANALYSIS” in the name of Adelaide Research & Innovation Pty Ltd; and

International Patent Application No PCT/AU2016/000246 (W02017008100) titled “SYSTEM AND METHOD FOR GENERATION OF A PRESSURE SIGNAL” in the name of The University of Adelaide.

[0003] The content of each of the above applications is incorporated by reference in their entirety.

TECHNICAL FIELD

[0004] The present disclosure relates to assessing the condition of a pipeline network. In a particular form, the present disclosure relates to assessing the condition of a pipeline network employing a persistent pressure signal generated in the fluid carried by the pipeline network.

BACKGROUND

[0005] Water transmission and distribution pipelines are critical infrastructure for modem cities. The internal pipe wall condition of these pipelines is difficult and expensive to assess, particularly after decades of use and many distribution pipelines consist of buried pipe networks that often deteriorate with age. Factors such as the age of pipes, the number of customer complaints and historic burst rates are often used as surrogate measures to indicate the overall condition of the pipeline network as opposed to a detailed knowledge of the pipeline condition. As a result, current pipeline rehabilitation programs often replace infrastructure that is in an acceptable condition and miss pipeline segments that will inevitably fail in the immediate future. Additionally, pipes and pipeline networks may be used to convey any number of types of fluid ranging from petroleum products to natural gas and these pipeline systems can be subject to the same degradation issues.

[0006] Areas of distributed deterioration can impose a number of negative impacts on pipeline operation, such as a decrease in discharge capacity, an increase in energy consumption, and in the case of water distribution pipelines the problem of degraded water quality resulting in public health risks. Moreover, distributed deterioration may also develop to the point of severe obstructions or bursts over time. As a result, it is preferable to detect distributed deterioration in pipeline systems at an early stage, with the intention of conducting targeted maintenance and rehabilitation before a catastrophic structural failure occurs.

[0007] A number of different methodologies have been developed for pipeline condition assessment based on the use of pressure waves generated in the fluid being conveyed by the pipeline. In one approach, the average wave speed of acoustic waves travelling along a section of pipeline bounded by two acoustic sensors is measured. The average wave speed is then used to calculate the average wall thickness of the section of the pipe. However, this approach only estimates the average condition of the whole section and cannot locate shorter deteriorated sections or segments of the pipeline that are otherwise bounded by pipe segments that are in good condition given that the average condition of the whole pipeline would be determined as acceptable. Additionally, this approach has difficulties when a pipeline may be composed of multiple different materials, (eg, where sections of PVC have been used for repairs in a cast iron pipeline) as the determined average condition of the pipeline could be significantly biased by these sections of a different material.

[0008] In another approach, controlled transient pressure waves with a short duration (ie, several to tens of milliseconds), such as would be created by artificially accelerating or decelerating the fluid in the pipeline, have been employed to interrogate a pipeline system. For example, an abrupt closure of an inline or side-discharge valve can introduce a step pressure wave. These pressure waves travel at high speed inside a fluid-filled pipe and reflections occur when the wave encounters any physical anomalies along the pipeline. The pressure wave reflections can be measured by pressure transducers and then interpreted through signal processing methods to assess the condition of the pipe. These techniques are efficient compared to other condition assessment techniques methods because the transient data as measured by the pressure transducers, just lasting a few seconds, can provide information about the wall condition of a pipeline stretching thousands of meters. The technique also has a wide operational range, since it can be applied to various types of pipelines either elevated or buried. [0009] In our earlier PCT Patent Application No. PCT/AU2009/001051 (WO/2010/017599) titled “METHOD AND SYSTEM FOR ASSESSMENT OF PIPELINE CONDITION”, the Applicant here disclosed a method and system for determining the location and extent of multiple variations in pipeline condition based on the use of a short duration transient pressure wave followed by an inverse transient analysis (IT A) which adopted an iterative approach to determine a full condition assessment of a pipeline based on optimisation techniques. While this approach has been very successful, it can become extremely computationally intensive for complex pipeline systems. Another issue with this transient pressure wave approach is that the sharp pressure surge used to generate a response from the pipeline may itself cause an issue with the pipeline. As a consequence, introducing these types of pressure variations into a pipeline may not be indicated, especially in the case of urban pipeline infrastructure. In addition, the spatial resolution of the detection, which is proportional to the sharpness of the wavefront, is relatively low (around 10 m).

[0010] In an approach to deal with the issues with short-duration transient pressure waves, pipeline assessment systems based on the use of a persistent pressure signal have been developed. An example persistent pressure signal is one that is generated in accordance with a pseudo-random binary sequence (PRBS) such as could be generated using a pressure wave generator of the type described in our earlier PCT Application No PCT/AU2016/000246 (WO2017008100). In our earlier PCT Patent Application No. PCT/AU2015/000415 (WO2017008098) titled “MULTIPLE TRANSDUCER METHOD AND SYSTEM FOR PIPELINE ANALYSIS”, the Applicant here disclosed a method and system for assessing the condition of a pipeline by measuring the pressure signal at two closely spaced measurement locations along the pipeline and then determining the system response function for the pipeline based on these two pressure signals.

[001 1 ] While this approach has been successful, the requirement for the measurement locations to be closely spaced (ie, typically 0.5 m - 5 m apart depending on the pipe size and the required spatial resolution) can be difficult to implement as standard access points for a pipeline, such as air valves and hydrants, are normally separated by more substantial lengths of pipeline (eg, 300 m - 1000 m for air valves and 15 m - 120 m for fire hydrants) in water distribution systems. One attempt to address this issue is to insert paired in-pipe fibre optic pressure sensors into the pipeline but this clearly introduces extra complexity to the pipeline assessment task and may not even be practical or feasible given that the pipeline is carrying a pressurised fluid.

[0012] It is against this background that there is a need for a method and system for assessing a pipeline network that avoids the use of closely spaced pressure transducers and is capable of being used in conjunction with the existing access points of network systems. SUMMARY

[0013] In a first aspect, the present disclosure provides a method for assessing a condition of a pipeline network having a pipeline configuration, comprising: generating at a generation location a persistent micro-transient pressure signal in a fluid being conveyed by the pipeline network; measuring at a first measurement location on the pipeline network a first time varying pressure response signal; measuring at a second measurement location on the pipeline network a second time varying pressure response signal, the second measurement location spaced apart from the first measurement location, wherein the generation location, first measurement location and second measurement location define an assessment configuration; determining a composite impulse response function (IRF) for the pipeline network based on the first time varying pressure response signal and the second time varying pressure response signal; and assessing the condition of the pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration.

[0014] In another form, determining the composite IRF comprises: deconvolving the first and second time varying pressure response signals with respect to each other.

[0015] In another form, the pipeline configuration comprises a junction between a first pipeline and a second pipeline and wherein the first measurement location is located on the first pipeline and the second measurement location is located on the second pipeline.

[0016] In another form, the pipeline configuration comprises a first pipeline forming part of a transmission pipe of a water network and wherein the first and second measurement locations are located on the first pipeline.

[0017] In another form, the generation location is the same as either the first measurement location or the second measurement location.

[00 i 8] In another form, the generation location is located externally to a region defined between the first measurement location and the second measurement location.

[0019] In another form, the generation location is located between the first measurement location and the second measurement location. [0020] In another form, characterising the pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration comprises: selecting a pipeline segment of the pipeline network; determining a first time window in the composite IRF corresponding to the selected pipeline segment based on a relationship of the selected pipeline segment with the pipeline configuration and the assessment configuration; and determining one or more anomaly induced wave reflections within the first time window to identify one or more anomalies in the selected pipeline segment.

[0021 ] In another form, a location or locations of the one or more anomalies are determined by a timing analysis of the one or more anomaly induced wave reflections in the composite IRF.

[0022] In another form, the pipeline segment is between the first and second measurement locations.

[0023] In another form, the method further comprises: generating at a second generation location a persistent micro -transient pressure signal in the fluid being conveyed by the pipeline network; measuring at a third measurement location on the pipeline network a third time varying pressure response signal; measuring at a fourth measurement location on the pipeline network a fourth time varying pressure response signal, wherein the second generation location, the third measurement location and the fourth measurement location together define a second assessment configuration, and wherein the selected pipeline segment is between the third and fourth measurement locations; determining a second composite IRF for the pipeline network based on the third time varying pressure response signal and the fourth time varying pressure response signal, the pipeline configuration and the second assessment configuration; and assessing the condition of the selected pipeline segment based on the second composite IRF, the pipeline configuration and the second assessment configuration.

[0024] In another form, assessing the condition of the selected pipeline segment based on the second composite IRF, the pipeline configuration and the second assessment configuration comprises: determining a second time window in the second composite IRF corresponding to the selected pipeline segment based on a relationship of the selected pipeline segment with the pipeline configuration and the second assessment configuration; determining one or more anomaly induced wave reflections within the second time window to identify one or more anomalies in the selected pipeline segment; and comparing the one or more anomaly induced wave reflections determined within the second time window to the one or more anomaly induced wave reflections determined within the first time window. [0025] In a second aspect, the present disclosure provides a system for assessing a condition of a pipeline network having a pipeline configuration, the system including: a persistent micro-transient pressure signal generator for generating at a generation location a persistent micro-transient pressure signal in a fluid being conveyed by the pipeline network; a first pressure measuring device for measuring at a first measurement location on the pipeline network a first time varying pressure response signal; a second pressure measuring device for measuring at a second measurement location on the pipeline network a second time varying pressure response signal, the second measurement location spaced apart from the first measurement location, wherein the generation location, first measurement location and second measurement location define an assessment configuration; an analysis module comprising one or more data processors configmed for: determining a composite impulse response function (IRF) for the pipeline network based on the first time varying pressure response signal and the second time varying pressure response signal; and assessing the condition of the pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration.

[0026] In another form, determining the composite IRF comprises: deconvolving the first and second time varying pressure response signals with respect to each other.

[0027] In another form, the pipeline configuration comprises a junction between a first pipeline and a second pipeline and wherein the first measurement location is located on the first pipeline and the second measurement location is located on the second pipeline.

[0028] In another form, the pipeline configuration comprises a first pipeline forming part of a transmission pipe of a water network and wherein the first and second measurement locations are located on the first pipeline.

[0029] In another form, the generation location is the same as either the first measurement location or the second measurement location.

[0030] In another form, the generation location is located between the first measurement location and the second measurement location.

[0031] In another form, the generation location is located externally to a region defined between the first measurement location and the second measurement location. [0032] In another form, characterising the pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration comprises: selecting a pipeline segment of the pipeline network; determining a first time window in the composite IRF corresponding to the selected pipeline segment based on a relationship of the selected pipeline segment with the pipeline configuration and the assessment configuration; and determining one or more anomaly induced wave reflections within the first time window to identify one or more anomalies in the selected pipeline segment.

[0033] In another form, a location or locations of the one or more anomalies are determined by a timing analysis of the one or more anomaly induced wave reflections in the composite IRF.

[0034] In another form, the pipeline segment is between the first and second measurement locations.

[0035] In another form, the system further comprises: generating at a second generation location a persistent micro -transient pressure signal in the fluid being conveyed by the pipeline network; measuring at a third measurement location on the pipeline network a third time varying pressure response signal; measuring at a fourth measurement location on the pipeline network a fourth time varying pressure response signal, wherein the second generation location, the third measurement location and the fourth measurement location together define a second assessment configuration, and wherein the selected pipeline segment is between the third and fourth measurement locations; determining a second composite IRF for the pipeline network based on the third time varying pressure response signal and the fourth time varying pressure response signal, the pipeline configuration and the second assessment configuration; and assessing the condition of the selected pipeline segment based on the second composite IRF, the pipeline configuration and the second assessment configuration.

[0036] In another form, assessing the condition of the selected pipeline segment based on the second composite IRF, the pipeline configuration and the second assessment configmation comprises: determining a second time window in the second composite IRF corresponding to the selected pipeline segment based on a relationship of the selected pipeline segment with the pipeline configuration and the second assessment configuration; determining one or more anomaly induced wave reflections within the second time window to identify one or more anomalies in the selected pipeline segment; and comparing the one or more anomaly induced wave reflections determined within the second time window to the one or more anomaly induced wave reflections determined within the first time window. [0037] In a third aspect, the present disclosure provides a system for assessing a condition of a pipeline network having a pipeline configuration comprising means for carrying a method in accordance with the first aspect of the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

[0038] Embodiments of the present disclosure will be discussed with reference to the accompanying drawings wherein:

[0039] Figure 1 is a flowchart of a method for assessing the condition of a pipeline network in accordance with an illustrative embodiment of the present disclosure;

[0040] Figure 2 is a system overview diagram of a pipeline network condition assessment system in accordance with an illustrative embodiment of the present disclosure;

[0041] Figure 3 is a figurative view of an example pipeline network having an associated pipeline configuration and depicting an example assessment configmation comprising a generation location and associated spaced apart measurement locations in accordance with an illustrative embodiment;

[0042] Figure 4 is a conceptual view showing the impulse response function (IRF) of a general linear system to a unit impulse;

[0043] Figure 5 is a conceptual view showing the output response signal of the general linear system illustrated in Figure 4 to a complex input signal;

[0044] Figure 6 is a figurative view of an example pipeline network having an associated pipeline configuration and depicting an example assessment configmation comprising a generation location and associated spaced apart measurement locations in accordance with an illustrative embodiment;

[0045] Figure 7 is a flowchart of a method for assessing the condition of a pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration in accordance with an illustrative embodiment;

[0046] Figure 8 is a figurative view of an example pipeline network having an associated pipeline configuration and depicting an example assessment configmation comprising a generation location and associated spaced apart measurement locations in accordance with an illustrative embodiment; [0047] Figure 9 is a figurative view of an example pipeline network having an associated pipeline configuration and depicting an example assessment configmation comprising a generation location and associated spaced apart measurement locations in accordance with an illustrative embodiment;

[0048] Figure 10 is a figurative view of an example pipeline network having an associated pipeline configuration and depicting an example assessment configmation comprising a generation location and associated spaced apart measurement locations in accordance with an illustrative embodiment;

[0049] Figure 11 is a figurative view of a pipeline network having an associated pipeline configuration and assessment configmation similar to Figure 10 except that the generation location and associated spaced apart measmement locations are located on standpipes remote from the pipeline;

[0050] Figure 12 is a flowchart of a method for assessing the condition of a pipeline in accordance with another illustrative embodiment of the present disclosure by adopting a second assessment configuration for comparison with the original assessment configuration;

[005] ] Figure 13 is a figurative view of a pipeline network having multiple measurement locations that may be assessed in accordance with an illustrative embodiment;

[0052] Figure 14 is figurative view of a pipeline network similar in configuration to that depicted in Figure 6 employed for numerical testing;

[0053] Figure 15 is a plot of the dimensionless valve opening parameter over a sample time period that is configured to simulate a persistent micro-transient pressure signal in the fluid being conveyed by the pipeline;

[0054] Figures 16(a) and (b) me plots of the simulated measured first and second time varying pressure response signals for the pipeline system illustrated in Figure 14 where the pressure signal generator at Gi is generating a persistent micro-transient pressure signal such as that illustrated in Figure 15;

[0055] Figures 17(a) and (b) me plots of the determined composite IRFs where the first plot corresponds to the pressure signal generator at Gi generating a persistent micro -transient pressure signal and the second plot corresponds to the pressure signal generator at second generation location G2 generating a persistent micro-transient pressure signal;

[0056] Figure 18 is a figurative view showing the various components of the composite IRF determined in Figures 17(a) and (b) and how they relate to the pipeline configuration and the assessment configuration; [0057] Figure 19 is a combined overlaid plot of the determined composite IRFs illustrated in Figures 17(a) and (b) but with the second plot corresponding to the pressure signal generator at G2 being time reversed;

[0058] Figure 20 is a plot of the simulated composite IRF for the pipeline system in Figure 14 where the pressure signal generator at Gi is generating a persistent micro-transient pressure signal but the pipeline is configured to have a dead-end configmation where in-line valve Vi is set to be closed;

[0059] Figure 21 is a figurative view of a pipeline network for numerically simulating the assessment of a pipe segment in a pipeline network in accordance with an illustrative embodiment;

[0060] Figures 22(a) and (b) are plots of the determined composite IRF for the pipeline network illustrated in Figure 21 where Figure 22(b) is a detailed enlarged view of Figure 22(a);

[0061 ] Figure 23 is a figurative view of a pipeline network for numerically simulating the assessment of a pipe segment in a pipeline network in accordance with an illustrative embodiment;

[0062] Figures 24(a) and (b) are plots of the determined composite IRF for the pipeline network illustrated in Figure 23 where Figure 24(b) is a detailed enlarged view of Figure 24(a);

[0063] Figure 25 is figurative view of an experimental pipeline network adopted to validate pipeline condition network assessment methods in accordance with the present disclosure;

[006 ] Figures 26(a) and (b) are plots of the measured first and second time-varying pressure response signals for the pipeline system illustrated in Figure 25 where Gi is open and generating a persistent microtransient pressure signal;

[0065] Figures 27(a) and (b) are plots of the determined composite IRFs for the pipeline system illustrated in Figure 25 where the first plot corresponds to a persistent micro-transient pressure signal being generated at Gi (ie, Figure 27(a)) and the second plot corresponds to a persistent micro-transient pressure signal being generated at G2 (ie, Figure 27(b)); and

[0066] Figure 28 is a plot comparing the composite IRF of Figure 27(a) with the time-reversed composite IRF of Figure 27(b).

DESCRIPTION OF EMBODIMENTS

[0067] Referring now to Figure 1, there is shown a flowchart of a method 100 for assessing the condition of a pipeline network according to an illustrative embodiment of the present disclosure. Referring also to Figure 2, there is shown a pipeline network condition assessment system 200 for assessing the condition of a pipeline network operable in one example to implement method 100. In this illustrative embodiment, assessment system 200 includes a persistent micro-transient pressure signal generator 220 for generating a persistent micro-transient pressure signal and first and second pressure measurement devices 230, 240 for measuring first and second time varying pressure response signals at their respective locations. System 200 further includes an analysis module 250 comprising at least a data processing module 256 operable to determine a composite impulse response function (IRF) and characterise or assess the condition of the pipeline network as will be discussed below. In one example, analysis module 250 may include one or more of a timing module 252 to control the timing of system 200, a data acquisition module 254 for acquiring the data obtained by the first and second measurement devices 230, 240, and/or a communications module 258 for communicating data and/or results.

[0068] Referring now to Figure 3, there is shown a figurative view of one example pipeline network 300 having an associated pipeline configuration and depicting an example assesement configuration comprising a persistent pressure signal generator and associated spaced apart measurement locations that may be assessed in one example in accordance with the method and system depicted in Figures 1 and 2. The pipeline configmation of pipeline network 300 in this example includes a first pipeline 310 (A to C) and a second pipeline 350 that connects with first pipeline at junction 355 at junction location D. In this example, first pipeline 310 would be characterised as a “main” pipeline and second pipeline would be characterised as a “branch” pipeline.

[0069] A persistent micro-transient pressure signal generator 220 is located at a generation location G which in this example is to the left hand side along main pipeline 310. Further along pipeline 310 is located first pressure measurement device 230 located at first measurement location P₁ Second pressure measurement device 240 is located on branch pipeline 350 at second measurement location P₂ which is spaced apart along the pipeline network 300 (ie, separated by distance L). The locations G, P₁ and P₂ define an assessment configuration that defines the respective positions of persistent micro-transient pressure signal generator 220, and the first and second pressure measurement devices 230, 240 relative to each other and to the pipeline configuration.

[0070] First and second pressure measurement devices 230, 240 are configured to measure first and second time varying pressure response signals respectively resulting from the persistent micro-transient pressure signal generated by persistent micro -transient pressure signal generator 220.

[0071 ] Persistent micro-transient pressure signal generator 220 may be any device capable of generating a persistent micro-transient pressure signal in pipeline 310. A persistent micro-transient pressure signal may be distinguished from a pressure wave, pulse or transient such as would be caused by introducing a one off abrupt change in the flow of any liquid being conveyed in pipeline network 300 by both the intensity and length of the pressure signal. In one example, the persistent micro-transient pressure signal may be a persistent wide band micro-transient pressure signal such as would be generated by opening a discharge valve and allowing it to remain open with a constant opening size with the persistent pressure signal then being generated by turbulence in the fluid as it exits the opening in pipeline network 300. In another example, the persistent pressure signal may be generated by a hydroacoustic pressure signal generator, such as a vibration shaker. In another example, the persistent pressure signal may arise from normal use of the pipeline network or the pipeline environment, such as by the opening of a water tap.

[0072 j In another example, a persistent micro-transient pressure signal may be generated in accordance with a pseudo-random binary sequence (PRBS) such as could be generated using a pressure wave generator of the type described in our earlier PCT Application No PCT/AU2016/000246 (W02017008100).

[0073] In one example, the persistent micro-transient pressure signal is generated for a duration corresponding to at least a multiple of 10 times the period expected for the pressure wave to transit the pipeline network that is to be assessed. As an example, for a wave speed of 1000 m/s and a pipeline network characterised by a length of 1000 m, the wave travelling time would be approximately 1 second and the duration of the persistent micro-transient pressure signal would in this example be configured to be at least 10 seconds (ie, 10 * 1 second). As a general observation, the longer the duration of the persistent micro-transient pressure signal, the more accurate the assessment will be with the tradeoff being that a longer signal requires a larger computer memory to conduct the deconvolution referred to below.

[0074] In other examples, the duration of the persistent micro -transient pressure signal may be selected from the following time ranges, including, but not limited to, greater than 5 s, 5 s - 10 s, 5 s - 10 s, 10 s - 20 s, 20 s - 30 s, 40 s - 50 s, 50 s - 60 s, 60 s- 70 s, 70 s - 80 s, 80 s - 90 s, 90 s - 100 s, or greater than 100 s.

[0075] In one example, the pressure magnitude of the micro -transient pressure signal may range from between 0.01 m to I m head pressure depending on the level of the background hydraulic noise in the pipeline network where as a general principle a higher level of background hydraulic noise in the pipeline network may require micro-transient pressure waves of a larger magnitude.

[0076] In other examples, the pressure magnitude of the micro-transient pressure waves may be selected from the following head pressure ranges, including, but not limited to, greater than 0.01 m, 0.01 m - 0.1 m , 0.1 m - 0.2 m, 0.2 m - 0.3 m, 0.3 m - 0.4 m, 0.4 m - 0.5 m, 0.5 m - 0.6 m, 0.6 m - 0.7 m, 0.7 m - 0.8 m, 0.8 m - 0.9 m, 0.9 m - 1.0 m, or greater than 1 m. [0077] In one example, the micro-transient pressure signal is a wide band signal having a lower frequency boundary of approximately 0 Hz - 20 Hz and an upper frequency boundary of 5 kHz. As a general observation, the upper frequency boundary may be selected depending on the pipe diameter and material of the pipeline network as well as the desired resolution and the characteristic distance covered by the pipeline network. As an example, a higher upper frequency bound may be required to identify an anomaly with less than 1 m spatial resolution within a short distance (such < 200 m) of the generation location.

[0078] In other examples, the upper frequency boundary of the micro-transient pressure waves may be selected from the following frequency ranges, including, but not limited to, greater than 50 Hz, 50 Hz - 500 Hz, 500 Hz - 1000 Hz, 1000 Hz - 1500 Hz, 1500 Hz - 2000 Hz, 2000 Hz - 2500 Hz, 2500 Hz - 3000 Hz, 3000 Hz - 3500 Hz, 3500 Hz - 4000 Hz, 4000 Hz - 4500 Hz, 4500 Hz - 5000 Hz, or greater than 5000 Hz.

[0079] Pressure measurement devices 230, 240 may be any suitable pressure sensing or transducer arrangement capable of measuring fluid pressure at a given location and measuring a time varying pressure response signal corresponding to the pipeline’s response to the persistent micro-transient pressure signal at the given location. Example pressure measurement devices include, but are not limited to, pressure transducers, hydrophones, in-pipe pressure sensors and accelerometers.

[0080] As referred to above, and as shown in Figure 3, pressure measurement devices 230, 240 are spaced apart by distance L. In accordance with the present disclosure, the term spaced apart is taken to mean that the distance L is at least 15 m. For a given pipeline network, the distance will be dependent on the sites of suitable access locations in the pipeline network, this being an advantage of the present method and system. As an example, for a pipeline network comprising a transmission mains, the distance L may range from 300 m - 1000 m due to the increased distance between access locations. This may be contrasted with smaller reticulation pipeline networks where the distance may range from 15 m - 120 m.

[0081 ] In other examples, the distance L between the first and second pressure measurement device may be selected from the following ranges, including, but not limited to, greater than 15 m, 15 m - 25 m, 25 m - 100 m, 100 m - 200 m, 200 m - 300 m, 300 m - 400 m, 400 m - 500 m, 500 m - 600 m, 600 m - 700 m, 700 m - 800 m, 800 m - 900 m, 900 m - 1000 m, or greater than 1000 m.

[0082] Referring back to Figures 1 and 2, at step 110 a persistent pressure signal is generated at generation location G in the fluid being carried or conveyed by pipeline network 300.

[0083] As depicted in Figure 3, in this example locations A, B and C represent boundaries of the pipeline network 300. In one example, the pipeline segment of most interest is the region between measurement locations P₁ and P₂, ie P₁ - P₂, which in this example comprises a portion of main pipeline 310 and branch pipeline 350. In other examples, the pipe segments P₁ - A and P₁ - B may also be assessed. Persistent micro-transient pressure signal generator 220 in this embodiment may be located at any position (between the two boundaries A and B). In one example, persistent micro-transient pressure signal generator 220 is located with pressure measurement device 230 (ie, first measurement location P₁) or pressure measurement device 240 (ie, second measurement location P₂). However, in this analysis, in order to generalise the mathematical model derived blow, G and P₁ are assumed to be separated by a pipe section as depicted in Figure 3.

[0084] It is instructive at this point to review some aspects of the characterisation of linear time-invariant systems as pipeline network 300 may be treated as a linear system to a good approximation. Referring now to Figure 4, there is shown a conceptual view 400 showing the impulse response function 430 of a general linear system 420 to a unit impulse 410. The term “impulse response function” refers to the measured response 430 in the time domain of the output of a system 420 following inputting into the system of a unit impulse signal 410. A unit impulse is an idealised function comprising a pulse having zero width and an infinite height and an integrated area of 1 (ie, unit impulse). In practice, the unit impulse may be approximated by a single spike with a height of “1”.

[0085] Referring now to Figure 5, there is shown a conceptual view 500 showing the output response signal 540 of the general linear system 420 illustrated in Figure 4 to a complex input signal 505. As depicted, a complex input signal 505 may be treated as a sequence of weighted unit impulses, in this case unit impulse 510A, unit impulse 510B and unit impulse 510C; with each weighted unit impulse 510A, 510B, 510C then generating a respective scaled output impulse response function 530A, 530B, 530C following interaction or processing by general linear system 420. The overall response or output 540 of the general linear system 420 to the complex input signal 505 is then the combination of the scaled time- lagged impulse response functions 530A, 530B, 530C.

[0086] The process to obtain the overall output response 540 using the input signal 505 and the impulse response function 430 is referred to as “convolution” and the inverse process to obtain the impulse response function 430 from the input 505 and output signals 540 is referred to as “deconvolution”. The Fourier transform of the impulse response function 430 is referred to as the “transfer function” for a given linear system 420.

[0087] The convolution process as depicted in Figure 5 may be expressed mathematically as:

Equation 1

[0088] where y is the output, x is the input and h is the impulse response function. N is the length of the impulse response function.

[0089] Referring back to Figure 2, The transfer function of the pipe segment from P₁ to P₂ is defined as H_1-2 (jω) and the term 0_o (jω is defined to be the injected persistent micro-transient pressure signal originating from persistent pressure signal generator 220 at location G.

[0090] At steps 120 and 130, a first time varying pressure response signal is measured at first measurement location P, and may be represented by the term (jω) in the frequency domain and a second time varying pressure response signal P₂ (jω is measured at second measurement location P₂. By reference to the pipeline network 300 shown in Figure 3, and in the description below, the superscripts “+” and mean the positive (from left to right or top to bottom) and negative travelling directions respectively (from right to left or bottom to top). As would be appreciated, the use of terms such as “+” and “upstream” and “downstream” or “left” and “right” are used for description purposes without any loss of generality and are not intended to confine the disclosure to the examples illustrated. As would be apparent, any suitable naming convention to indicate the opposite directions may be used and it would be understood that these different naming conventions would be interchangeable.

[0091 ] In this example, the impulse response functions (IRFs) in the frequency domain on the left side and the right side of first pressure measurement device 230 at location P₁ may be defined as R_{L 1} (jω) and

(jω), respectively. Note that transfer function R_{R 1} (jω maps from the positive travelling wave propagating past P₁ to the returning negative travelling wave, and as such it encapsulates the dynamics to the right of P₁. Similarly, transfer function R_{L 1} (jω ) maps from the negative travelling wave propagating past P₁ to the returning positive travelling wave, and as such it encapsulates the dynamics to the left of P₁.

[0092] The IRF on the left (upper) and right (lower) sides of pressure measurement device 240 at location P₂ is defined as R_{L 2} (jω and R_{R 2} (jω). respectively. Noting the IRF R_{L 2} (jω includes the reflections from pipeline segment A-D and pipeline segment D-C. Excluding the reflections from P₁-A in R_L,2 (jω) gives the definition of Since, in this example the pipeline segment that is to be assessed is P₁ - P₂ (or equivalently ft - D - P₂) the time window of interest for these IRFs, therefore, is the round-trip travel time for the transient wave within this section, which is:

T = — Equation 2

[0093] where L is the length of the pipeline segment P₁ - P₂ and a is the average wave speed of this pipeline segment. [0094] In the following, the order of the reflected waves is defined based on the number of times that the injected pressure wave is reflected by any discontinuities or anomalies in the pipe. Normally, wave reflections by an anomaly, such as a deteriorated section, in pipes will be less than 10% of the original amplitude, those reflections by cross-connections will be much larger and those by dead-ends and water tanks will be 95 - 100%. By assuming in this example that anomalies in the pipe induce a 5% wave reflection and cross-connections induce a 50% wave reflection, the amplitude of the wave reflected by anomalies twice (the second-order reflection) will be only 0.25% of the original wave amplitude and thus can be neglected. However, if the first-order anomaly -induced wave reflection is reflected again by a pipeline feature such as a cross-connection, dead-end, tank or a reservoir, the second-order wave reflection will be of the same order of magnitude as the first-order wave reflection and thus cannot be neglected.

[0095] In accordance with Figure 3, the negative travelling pressure wave at P₁ is caused by the wave reflections of P₁ ⁺ by the pipe at the right side of P₁ and is given by: Equation 3

[0096] and thus (jω which is the sum of P

and is:

Equation 4

[0097] At location P₂, the positive travelling pressure wave contains after propagating from P, to

P₂ and the wave reflections of P₂“ by the pipe segment P₂ - A. It follows that: Equation 5

[0098] At location P₁, P is caused by the wave reflections of by the pipe at the right side of P₂ and

as a result is given by: Equation 6

[0099] Substituting Equation 6 into Equation 5 yields: Equation 7

[001(H)] Substituting Equation 7 into Equation 6 yields: _S Equation 8

[00101 ] The sum of Equations 7 and 8 gives the total pressure at P₂ which is

Equation 9

[00102] The pressure P₂ divided by P₁ gives:

Equation 10

[00103] By applying the Taylor series expansion to the denominator of Equation 10, and ignoring the anomaly -induced higher-order wave reflections, this gives:

Equation 11

[00104] At step 140, the composite IRF for the pipeline is determined based on the first and second time-varying pressure response signal P₁ and P₂. As can be seen from Equation 11 , in the frequency domain the term on the right hand side corresponds to a composite IRF corresponding to the different pipeline segments for the assessment configuration and the pipeline configuration of the pipeline network 300 shown in Figure 3.

[00105 ] In one example, in order to determine the composite IRF (ie, in the time domain) it is noted that the division of P₂/P₁ in the frequency domain corresponds to a deconvolution process in the time domain and as such the composite IRF may be determined by carrying out a deconvolution of the first and second time varying pressure response signals with respect to each other.

[00106] In the formalism adapted with respect to Equation 1, the convolution process may be rewritten in matrix form as: y = xh Equation 12

[00107] where signal y is a M x 1 column vector consisting of the output signal (which is the pressure trace P₁ in our case), X is a N x M convolution matrix constructed using the input signal (which is the pressure trace P₂ in our case) and h is a N x 1 column vector representing the impulse response function which is equivalent to the transfer function in the frequency domain. The matrix X and the column vectors y and h are expressed as follows:

Equation 13

Equation 14

Equation 15

[00108] For the deconvolution process, the vector h is determined based on the measured y and X. Since X'¹ does not exist for a non-square matrix, the vector h cannot be solved directly using Equation 12.

[0 109] In one example, the deconvolution is determined using a least squares deconvolution process. In this approach, to best estimate h, the mean square error between y and Xh is written as:

Equation 16

[00110] and by minimizing the mean square error, the impulse response function may be written as: h = (X^TX) ^-1X^Ty Equation 17

[001 1 [] In other embodiments, other deconvolution methods, such as the use of singular-value decomposition, may also be used. In another example, the functions (jω ) and P₂ (jω) may be determined explicitly in the frequency domain based on the first time varying pressure response signal and the second time varying pressure response signal and then transforming the quantity P (jω)/ P₂1jω) back into the time domain.

[001 12] At step 150, the pipeline is assessed based on the determined composite IRF and the assessment configuration. In this example, the composite IRF in the time domain may be interpreted based on the various terms indicated on the right hand side of Equation 11 in the frequency domain. This allows the composite IRF to be analysed to determine features that may be identified as corresponding to anomalies in the pipeline network. [(101 13] In this example, with the generation location G either at, or to the left of P_1; the transfer function H_1-2 physically represents:

1) a time delay by the single-trip travel time from P₁ to P₂ (ie, T/2 in this example),

2) the wave transmission, dissipation and dispersion caused by the pipeline segment P₁-D-P₂, and

3) higher-order wave reflections of the incident wave arriving at P₂.

[001 14] The value of unity in the brackets in Equation 11 relates to the injected persistent microtransient pressure signal after reaching P₂ and significantly all the other terms in the brackets represent the wave reflections by the pipe system. Therefore, the overall time varying pressure response signal reflected by the pipe system from the persistent micro-transient pressure signal, which would be ordinarily mixed with the input persistent pressure signal in the measured first and second time varying pressure response signals, can be separated from the input persistent pressure signal by using Equation 11 in accordance with the present disclosure.

[001 15] It can be seen from Equation 11 that the result of P₂/ P₁ is independent of of pipeline segment G - P₁ and thus the location G of the generator with respect to the left hand side of P₁ may be selected as required. In one example, the location G of the persistent pressure signal generator 220 may be selected to be at the same location as P₁ corresponding to the location of the first pressure measurement device 230 which could correspond to an access point for pipeline 310 such as an air valve or at a hydrant.

[00116] Equation 11 also demonstrates that the anomalies and pipe components on the left side of P₁ do not have any effect on the result of P₂/ P₁. Accordingly, the composite IRF determined in the time domain by the deconvolution of the first and second time varying pressure response signals with respect to each other will only examine the right side of P₁

[00117] Equation 11 will be discussed in detail in the following examples for different pipeline and assessment configmations.

Example 1

Pipeline Configuration - Continuous Single Pipeline

Assessment Configuration - Continuous Pipeline Segment with Generation Location External to Pipeline Segment

[001 18] Referring now to Figure 6, there is shown a figurative view of an example pipeline network 600 having an associated pipeline configuration and depicting an example assessment configuration comprising a generation location and associated spaced apart measurement locations in accordance with another illustrative embodiment. In this example, the pipeline segment to be characterised or assessed is located on a main line 610 and the pipeline configuration to the right side of P₂ does not contain any cross-connections, dead-ends, reservoir or tanks within a distance of the separation distance L that corresponds to the spacing between the first and second pressure measurement devices 230, 240. In this example, R_{R 2} for the duration T will then consist of only anomaly -induced wave reflections. Now by neglecting the higher-order anomaly -induced wave reflections, Equation 11 may be further simplified to: Equation 18

[00119] where H is equivalent to H_1-2 after neglecting the higher-order wave reflections.

[00120] Accordingly, in the time period of (0, T), the physical interpretation of R_{R 1} is that it corresponds to the anomaly-induced wave reflections within the pipe segment P₁ - P₂ and R_RI2 represents any induced reflections by any physical discontinuities to the right side of P₂ within a distance of L (see Equation 2).

[0012] ] Referring now to Figure 7, there is shown a flowchart of a method 700 for assessing the condition of a pipeline network based on the composite IRF, the pipeline configmation and the assessment configuration according to an illustrative embodiment that corresponds to one example implementation of step 150 of Figure 1.

[00122] At step 710, a pipeline segment of the pipeline network is selected to be assessed. In this example, the pipeline segment is selected to be P₁ - P₂. At step 720, a time window in the composite IRF is determined based on a relationship of the selected pipeline segment with the pipeline configuration and the assessment configuration.

[00123] In this example, based on the physical meaning of H. this term delays all the pressure wave reflections by T/2, ie, the single-trip travel time for the transient wave within pipeline segment P₁ - P₂ and as a result the composite IRF determined by the deconvolution process for the time window between T/2 to 37/2 will correspond to the pipeline segment P₁ - P₂.

[00124] At step 730, anomaly induced reflections are determined in the time window to identify anomalies that occur in the selected pipeline segment. In one example, the location of the anomalies may be determined by the timing of the anomaly induced reflections in the time window.

[001 3] In this example, for the pressure reflection in R_{R 1}, the location L_a of the anomaly induced reflection may be calculated relative to to P₁ in accordance with the relationship: Equation 19

[001 6] where t is the corresponding time of the anomaly induced reflection in the composite IRF. Note that the start point and the direction of the distance is determined by the subscript of the IRF. For example, for spikes associated with R_{R 1}, the distance L_a starts from the first measurement location (P₁) and moving to the right.

[00127] For the impulse reflections in R_{R 2}, Equation 19 can also be used for the time window between T/2 to 3T/2, but in this case the calculated distance is from P₂ to the physical anomaly based on the definition of R_{R 2}- as extending from P₂ to B.

Example 2

Pipeline Configuration - Continuous Single Pipeline with a Dead-End at One End Assessment Configuration - Continuous Pipeline Segment with Generation Location External to Pipeline Segment

[00128] As can be seen from Equation 11, if the relationship between the assessment configuration and the pipeline network is such that the pipeline network has a pipeline feature to the left of G as depicted in Figure 3, then this will not affect the form of P₂/P₁ in the frequency domain and hence the composite IRF in the time domain. So as an example, if the pipeline segment is not a pure internal segment such as depicted in Figure 6, but has a dead-end at one end, for example, at A with the generation location G located as shown in Figure 6, the pipe boundary condition will not affect P₂/P₁ according to Equation 11.

[00129] Referring now to Figure 8, there is shown a figurative view of an example pipeline network 800 having an associated pipeline configuration and depicting an example assessment configuration comprising a generation location and associated spaced apart measurement locations in accordance with another illustrative embodiment. In this example, the pipeline configmation comprises an open end at A and a dead-end located in this example just next to the right of second measurement location P₂ at B. Once again the assessment configuration comprises the generation location to the left or at first measurement location P, and the second measurement location P₂ spaced a distance L from P₁.

[00130] In this case, the term R_{R 2} in Equation 11 is equal to 1 and so this equation may be further simplified to:

Equation 20

[09131] It follows from this equation that the magnitude of the impulse responses in the composite IRF will both double. Each anomaly will induce two anomaly induced wave reflections (corresponding to R_{R 1} and R_{L 2}, respectively) in the period between T/2 to 3 T/2 and they will be antisymmetric around the coordinate (7, 0) on the plot of the composite IRF.

[00132] In this example, based on the physical interpretation of H. this term delays all the pressure wave reflections by T/2, ie, the single-trip travel time for the transient wave within pipeline segment P₁ - P₂ and as a result the composite IRF determined by the deconvolution process for the time window between T/2 to 37/2 will correspond to the pipeline segment P₁ - P₂.

[00133] Once again, at step 730 (see Figure 7) anomaly induced reflections are determined in the time window to identify anomalies that occur in the selected pipeline segment. In one example, the location of the anomalies may be determined by the timing of the anomaly induced reflections in the time window. In this example, the location of the anomaly or anomalies can be calculated based on Equationl9.

Example 3

Pipeline Configuration - Continuous Single Pipeline with Pipeline Junction at One End Assessment Configuration - Continuous Pipeline Segment with Generation Location External to Pipeline Segment

[00134] Referring now to Figure 9, there is shown a figurative view of an example pipeline network 900 having an associated pipeline configuration and depicting an example assessment configuration comprising a generation location and associated spaced apart measurement locations according to another illustrative embodiment. In this example, the pipeline configuration comprises a junction or cross-connection J at a distance of L_j (where L_j < L) to the right of second measurement location P₂.

[00135] For a junction or cross-connection just next to the second pressure measurement P₂ (L_j ~

0), the term R_{R 2} in Equation 11 will be a negative constant, say -ij-.The constant rj is the reflection ratio of the transient wave at the cross-connection and it is determined by the size and wave speed of the pipes connected with the cross-connection. Thus, Equation 11 may be simplified as: Equation 21

[00136] This equation shows that the magnitude of the impulse reflections by the anomalies in the pipe segment P₁ - P₂ will be diminished. Each anomaly will induce two anomaly induced reflections with different magnitudes on the time interval (7/2, 37/2) and their locations will be symmetric around the coordinate (7, 0) in the composite IRF.

[00137] In one example, if the pipeline configuration of pipeline network is such that cross- connections or junctions are close to the measurement location (L_j < L) this can cause higher-order wave reflections that may be visible. According to Equation 11, the principal wave reflections will be similar to those observed in an internal pipe segment in a pipeline system such as that illustrated in Figure 3. For the case in Figure 9, the distance between the junction J and P₂ is assumed to be L_j and the persistent microtransient pressure signal generator 220 is assumed to be at P₁.

[00138] The term R_{R 2} R_L in Equation 11 may then be interpreted as 2^nd-order wave reflections

by J and anomalies within the distance of (L - L_j) left of P₂ in the period of interest (7/2 to 37/2). The term R_R,1R_R,2 in Equation 11 may then be interpreted as 2^nd-order wave reflections by J and anomalies within the distance of (L - L_j) to the right of P₁ in the period of interest.

[00139] The term in Equation 11 may then be interpreted as 3rd-order wave reflections

by J (reflected by J twice) and anomalies within the distance of (L - 2L_j) left of P₂ in the period of interest. If (L - L_j) < 0, all the higher-order wave reflections will appear beyond the period of interest and can be neglected. If (L - 2L_j) < 0 but (L - L_j) > 0, then only the 3rd-order wave reflections in

will appear beyond the period of interest and thus can be neglected. Overall, all the visible higher-order wave reflections can be interpreted using Equation 11.

Example 4

Pipeline Configuration - Continuous Single Pipeline

Assessment Configuration - Continuous Pipeline Segment with Generation Location Internal to Pipeline Segment

[00140] Referring now to Figure 10, there is shown a figurative view of an example pipeline network 1000 having an associated pipeline configuration and depicting an example assessment configuration comprising a generation location and associated spaced apart measurement locations according to another illustrative embodiment. In this example, the pipeline configuration is similar to pipeline network 300 depicted in Figure 3 but in this case the assessment configmation differs as the generation location G is located between the first and second measurement locations P₁ and P₂ which are still located a distance L apart. In this embodiment, the aim is to detect anomalies in the pipe segment A- B. The pipe segment P₁- P₂ can be non-uniform. In this arrangement, the deconvolution trace between the pressure signals measured at P₂ and P₁ gives: Equation 22

[0014] ] In this example, based on the physical interpretation of H₂ and H₂ the term delays all

the pressure wave reflections by T_G, which can be calculated by (G;-P₂ - L_G-P ')/a, where L_G-PI is the distance from G to P₁ and L_G_p₂ is the distance from G to P₂. As a result, the composite IRF determined by the deconvolution process for the time window between T_G to T_G + T will correspond to the pipeline segment P₁ - P₂.

[00142] Once again, at step 730 anomaly induced reflections are determined in the time window to identify anomalies that occur in the selected pipeline segment. In one example, the location of the anomalies may be determined by the timing of the anomaly induced reflections in the time window.

[00143] In this example, the possible locations of the anomaly /anomalies can be calculated based on Equationl9.

Example 5

Pipeline Configuration - Continuous Single Pipeline

Assessment Configuration - Continuous Pipeline Segment with Generation Location Internal to Pipeline Segment and Pressure Measurement Devices and Pressure Signal Generator Located on Stand Pipes

[00144] Referring now to Figure 11, there is shown a figurative view of a pipeline network 1100 having an associated pipeline configuration and assessment configuration similar to Figure 10 except that the generation location and associated spaced apart measurement locations are located on standpipes remote from the pipeline. In one example, the standpipe is a hydrant or an air valve having a length of approximately 0.2 m - 1.0 m and a diameter of approximately 50 mm.

[00145] In this example, the transmission ratio defined as the ratio between the magnitude of the transmitted wave and that of the incident wave is for a wave transmitting from the standpipe to the main pipe and s₂ from the main pipe to the standpipe. The term s = s₁s₂ is a constant, ranging from 0.05 to 0.5, and depends on the diameter of the stand pipe where a larger diameter of the standpipe corresponds to a larger value for s .

[001 6] In the example of using pressure sensor 240 at location P₂ and another pressure sensor 1125 at location P_G, the overall sensor configuration can be treated the same as Figure 3 except for the presence of standpipes by assuming G is at the same location with P₁. In this case, following Equation 11, the relationship below applies for the composite IRF in frequency space, ie: 1quation 23

[00147] In this example, based on the physical meaning of H. this term delays all the pressure wave reflections by T/2, ie, the single-trip travel time for the transient wave within pipeline segment P_G - P₂ and as a result the composite IRF determined by the deconvolution process for the time window between 7/2 to T/2 will correspond to the pipeline segment P_G - P₂.

[00148] Once again, at step 730 anomaly induced reflections are determined in the time window to identify anomalies that occur in the selected pipeline segment. In one example, the location of the anomalies may be determined by the timing of the anomaly induced reflections in the time window. In this example, the possible locations of the anomaly /anomalies can be calculated based on Equation 19.

Example 6

Pipeline Configuration - Pipeline Junction

Assessment Configuration - Interrupted Pipeline Segment Connected by a Junction with Generation Location External to Pipeline Segment

[001 9] Referring back to Figure 3, by contrast with the pipeline network 600 and associated assessment configuration, here pipeline network 300 involves an assessment configuration where the pressure measurement locations are on different pipes in pipeline network 300. In this case, the transfer function H_1-2 cannot be simplified to // since strong higher-order wave reflections will be caused by the junction D between the two pressure measurement devices 230, 240. By ignoring other higher-order reflections, Equation 11 can be simplified to: Equation 24

[00150] In this example, based on the physical meaning of H_1-2, this term delays all the pressure wave reflections by 7/2, ie, the single-trip travel time for the transient wave within pipeline segment P₁ - P₂ and as a result the composite IRF determined by the deconvolution process for the time window between 7/2 to T/2 will correspond to the pipeline segment P₁ - P₂.

[00151] Once again, at step 730 anomaly induced reflections are determined in the time window to identify anomalies that occur in the selected pipeline segment. In one example, the location of the anomalies may be determined by the timing of the anomaly induced reflections in the time window. In this example, the possible locations of the anomaly /anomalies can be calculated based on Equationl9. Combining Different Assessment Configurations

[00152] In accordance with the present disclosure, a composite IRF may be determined with a pair of spaced apart pressure measuring devices and a persistent micro-transient pressure signal generator deployed in an assessment configuration. Based on this assessment configmation, the pipeline configuration and the composite IRF, the pipeline network may then be assessed.

[00153] If multiple tests are conducted with different assessment configurations, multiple composite IRFs may be obtained for the same pipeline network. Different assessment configurations may be achieved by either changing the generation location of the persistent micro-transient pressure signal generator or the first and second measurement locations of the first and second pressure measuring devices. In one example, these composite IRFs based on different assessment configmation may be selected to contain the same pipeline segment that may be of interest. By combining these results, the ability to identify the anomaly/anomalies in the pipe segment may be significantly improved due to the reinforcement of the signal from the different composite IRFs.

[00154] Referring now to Figure 12, there is shown a flowchart of a method 1200 for assessing the condition of a pipeline according to another illustrative embodiment of the present disclosme by adopting a second assessment configuration for comparison with the original assessment configmation to assess the condition of a selected pipeline segment.

[00155] At step 1210, and referring again to Figure 3 where P₁ - P₂ has already been selected as a pipeline segment and assessed or characterised based on the assessment configmation as depicted, the persistent micro-transient pressure signal generator is located at a second generation location. In one example, the second generation location is at P₂, or to the right side of P₂, as depicted in Figure 3, and a persistent micro-transient pressure signal is generated at this second location.

[00156] At steps 1220 and 1230, third and fourth time varying pressure response signals me measured at respective third and fourth measurement locations, where these measurement locations me chosen so that the selected pipeline segment is between these measurement locations. The second generation location and third and fourth measurement locations define a second assessment configuration. By reference to Figure 3, in one example the third and fourth measurement locations are chosen to be the same as P₁ and P₂ noting that the pipeline segment P₁ - P₂ is by definition located between these measurement locations. Accordingly, in this case the only difference between this newly defined second assessment configuration and the assessment configuration of Figure 3 is the change of the generation location to the second generation location. [00157] In this case, the second composite IRF in frequency space corresponding to the second assessment configuration will be equivalent to Equation 11 but with the subscripts 1 and 2 and directions left and right exchanged. Equation 11 may be rewritten as follows: Equation 25

[00158] Equation 25 may be simplified by neglecting the higher-order anomaly-induced wave reflections (similar to Equation 18) to:

Equation 26

[00159] At step 1240, the second composite IRF for the pipeline network is determined based on the third time varying pressure response signal and the fourth time varying pressure response signal, the pipeline configuration and the second assessment configuration. In this case, the third time varying pressure response signal corresponds to P_r (in the frequency domain) and the fourth time varying pressure response signal corresponds to P₂ (in the frequency domain) and the division of P₁/P₂ iⁿ the frequency domain corresponds to a deconvolution process in the time domain and as such the composite IRF may be determined by carrying out a deconvolution of the third time varying pressure response signal with respect to the fourth time varying pressure response signal.

[00160] At step 1250, the selected pipeline segment is assessed based on the second composite IRF, the pipeline configuration and the second assessment configuration. Following method 700, a second time window in the second composite IRF corresponding to pipeline segment P₁ - P₂ may be determined. In this example, the time window between T/2 to 3T/2 will consist of any anomaly induced reflections from the pipe segment P₁ - P₂ propagating to P₂ and any anomaly induced reflections by the pipeline section left of P₁ propagating to P₁.

[00161] In this manner, the composite IRF obtained from the original assessment configuration of Figure 3 where G is to the left of, or at, P₁ (ie deconvolution trace of P₂ with respect to P^ and the second assessment configuration where G is to the right, or at, P₂, will share an overlap region covering the pipe segment P₁ - P₂ between the two pressure measurement locations. In this manner, and as will be described below, composite IRFs corresponding to different assessment configurations, depending on the configuration of the pipeline system, may be combined to enhance the assessment capability of the present method.

[00162] In this example, P₂/P₁ corresponding to the first assessment configuration (when the generation location is at the left side of P₁) and P₁/P₂ corresponding to the second assessment configuration in the period between T/2 to 3 T/2 both contain the anomaly induced reflections from the pipe segment P₁ - P₂ but with different wave directions. Accordingly, the respective time windows in the composite IRFs may be compared. In one example, the respective time windows may be combined or overlapped by reversing in time one of the time windows of the composite IRF with respect to the other time window of the other composite IRF where in this case the time window would correspond to the period between T/2 to 3 T/2. Following this approach, anomaly induced reflections from the same anomaly in the two composite IRFs will overlay and match each either functioning as a further anomaly detection check or to reinforce the anomaly signal in the combined and overlay ed time windows.

[00163] Referring now to Figure 13, there is shown a figurative view of a pipeline network 1300 having multiple measurement locations P₁, P₂, P3 and P₄ where a pressure measuring device may be located that may be assessed according to an illustrative embodiment. In this case, the pipeline segment of interest is between P₂ and P₃ (ie, P₂ - P₃).

[00164] In this example, the generation location G of the persistent micro-transient pressure signal generator may potentially be located at four different access points corresponding to the four different measurement locations P_1; P₂, P₃ and P₄ resulting in the eight assessment configurations shown in Table 1 that may be adopted to assess the selected pipeline selected P₂ - P₃. Accordingly, eight different composite IRFs may be obtained that cover the pipeline segment P₂ - P₃ and time windows from each of the composite IRFs that correspond to the pipeline segment P₂ - P₃ may be determined. These time windows may then be shifted and/or time reversed as described above to compare the presence of anomaly induced reflections in the time windows. In other examples, the respective time windows corresponding to the composite IRFS may be combined or overlaid to further assist in the identification of any anomaly induced reflections in the pipeline segment.

TABLE 1

Eight Assessment Configurations

Numerical Case Studies

[00165] Numerical simulations have been conducted on different pipe networks to simulate the performance of pipeline condition assessment methods and systems implemented in accordance with the present disclosure. In these numerical simulations, the method of characteristics (MOC) was adopted to simulate the measured pressure signals resulting from a persistent micro-transient pressure signal in the form of an open valve on the pipeline. A time step of 0.0001 s was used for the first two numerical cases referred to below and 0.001 s for the third numerical case.

Case Sudy 1

Pipeline Configuration - Continuous Single Pipeline

[00166] Referring now to Figure 14, there is shown a figurative view of a pipeline network 1400 having a similar pipeline configmation to that depicted in Figure 6 that has been adopted for numerical simulation of methods for assessing the condition of a pipeline network in accordance with the present disclosure and as described below. In this example, the internal diameter of the pipeline is assumed to be 100 mm except for two 2-metre blocked sections, Bi and B2, which have reduced diameters of 90 and 92 mm respectively. In this example, the transient wave speed is assumed to be 1000 m/s and the Darcy- Weisbach factor is 0.02.

[00167] The length of each pipeline segment is also shown in Figure 14 from which it can be determined that the period of interest is T = 0.12 s. A leak (indicated as Li in Figure 14) with C_dA_L = 2.54 x 10^-5 m² and initial flowrate = 0.87 L/s for the initial pressure head = 60 m (C_d is the discharge efficiency and A_L is the area of the leak orifice) is located between two pressure sensors 1430, 1440 at respective locations P₁ and P₂. In this simulation, two persistent pressure signal generators 1420, 1425 both in the form of a valve with an initial flowrate = 0.024 L/s are located at Gi and G2. In this example, locations Gi and G2 are the same as P₁ and P₂ respectively. The dimensionless valve opening T* is equal to 1 at the initial status when the flowrate is 0.024 L/s.

[00168] In this simulation, an in-line valve (Vi) is modelled to be located at the same place as P₂, and it is fully open. Additionally, another valve (V2) is modelled at the end of the pipeline and is fully closed in this case. Pressure signal generators 1420, 1425 were configmed to produce random valve opening changes following a white noise sequence in all the numerical simulations described below. This arrangement simulates the persistent micro-transient pressure signal that would be generated by a sidedischarge valve with a constant opening in a real pipeline network arising from turbulence in the discharge.

[00 69] Referring now to Figure 15, there is shown a plot 1500 of the dimensionless valve opening parameter r*over a sample time period of 0.2 seconds that is configmed to simulate a persistent micro-transient pressure signal in the fluid being conveyed by the pipeline network 1400 shown in Figme 14.

[00170] In this example, two numerical simulations were conducted. In the first simulation, persistent micro-transient pressure signal generator 1425 at location G2 was inoperative and persistent micro-transient pressure signal generator 1420 at Gi generated a persistent micro-transient pressure signal (see step 110 of Figure 1). In the second simulation, persistent micro-transient pressure signal generator 1420 at location Gi was inoperative and only persistent micro-transient pressure signal generator 1425 at location G2 generated a persistent micro-transient pressure signal.

[00171 ] Referring now to Figures 16(a) and (b), there are shown plots 1600 of the simulated measured first and second time-varying pressure response signals 1610, 1620 (ie, corresponding

and P₂ in the time domain) for the pipeline network 1400 illustrated in Figme 14 (see steps 120 and 130 of Figure 1) where persistent micro-transient pressure signal generator 1420 at location Gi is generating a persistent micro-transient pressure signal such as that illustrated in Figme 13 (see step 110 of Figure 1). As can be seen, the simulated measmed first and second time-varying pressure response signals 1610, 1620 each have a magnitude less than 0.4 m and in of themselves do not appear to present any structural information related to the pipeline. Although not plotted here, the time varying response signals for the case of where pressure signal generator 1425 at location G2 is generating a pressure signal also have the same overall characteristics.

[00172] Referring now to Figures 17(a) and (b), there are shown plots 1700 of the determined composite IRFs where the first plot 1710 (ie, Figure 17(a)) corresponds to Gi generating a persistent micro-transient pressure signal and the second plot 1720 (ie, Figure 17(b)) corresponds to second generation location G2 generating a persistent micro-transient pressure signal (see step 140 of Figure 1). In this example, the first composite IRF is determined by carrying out a deconvolution corresponding to P2/P1 (P₁, P2 are the pressure traces when the generator 1420 at location Gi is operating) which examines the pipeline to the right side of P₁ and the second composite IRF is determined by carrying out a deconvolution corresponding to P₁/P₂ P₁, P2 are the pressure traces when the generator 1425 at location G2 is operating) which examines the pipeline to the left side of P₂.

[00173] As can be seen from inspection, the feature at 0.16 s in Figure 17(a) and the feature at 0.08 s in Figure 17 (b) are induced by the leak between P₁ and P₂. The features in the ellipse in Figure 17(a) are both are as a result of the blockage section B₂, and correspond to R_{R 2}- and R_{R 1} in Equation 18, respectively. Similarly, the features in the ellipse in Figure 17(b) are as a result of the blockage section Bi.

[00 74] Referring now to Figures 18, there is shown a figurative view 1800 showing the various components of the composite IRFs determined in Figures 17(a) and (b) and how they relate to the pipeline configuration and assessment configuration. The composite IRF for the first numerical simulation is for the assessment configuration where the generation location G is at P₁ (ie, Gi) and corresponds to P₂/^i- The composite IRF for the second numerical simulation is for the assessment configuration where the generation location G is at P₂ (ie, G2) and corresponds to P₁/P₂-

[00175] As can be seen, the composite IRF corresponding to P₂/P₁ contains the IRF of the pipe segment P₁ — P₂ from point 3 to point 4, and the IRF from point 5 to point 6 in the time window from T/2 to 3T/2 according to Equation 18. The composite IRF corresponding to P₁/P₂ contains the IRF of the pipe segment P1-P₂ from point 4 to point 3, and the IRF from point 2 to point 1 in the time window from T/2 to 3772 according to Equation 26.

[00176] Both of the above identified time windows of the composite IRFs contain the IRF of pipe segment P, - P₂ but with a different direction. By reversing one of the time windows, the time windows of the respective composite IRFs of pipe segments P, - P₂ may then be combined with each other to determine whether there are matching features which will correspond to anomaly induced reflections in the selected pipe segment. Other features that do not match up in the composite IRF corresponding to P₂/P₁ will be caused by anomalies from point 5 to point 6, while unmatched features in the composite IRF corresponding to P₁/P₂ will be caused by anomalies from point 1 to point 2.

[00177] Referring now to Figure 19, there is shown a plot 1900 of the composite IRFs illustrated in Figure 17 but with the second plot corresponding to signal generator 1425 at location G2 generating a persistent micro-transient pressure signal (ie, corresponding to Figure 17(b)) being time reversed and overlayed on the plot corresponding to signal generator 1420 at location Gi (ie, corresponding to Figure 17(a)). In the combined overlayed plot 1900, the regions in the two composite IRFs for the time period between 172 to 3772 (ie, the dashed boxes in Figures 17(a) and (b)) are selected to highlight the anomalies between P₁ and P₂.

[00178] As can be seen in Figure 19, the anomalies (Li in this case) in the pipe segment P, - P₂ can be identified by the matched spikes in the two composite IRFs as shown in the dashed rectangle 1960. The blockages Bi and B₂ outside of pipeline segment P, - P₂ can be identified by the unmatched features or spike corresponding to composite IRFs that correspond to P₁/P₂ and P₂/P₁, respectively.

Case Study 2

[00179] Pipeline network 1400 was also adopted to simulate the effect of a pipeline network comprising a pipeline configuration where the pipeline network has a dead end by closing in-line valve Vi and an assessment configuration with pressure signal generator 1420 located at Gi generating a persistent micro-transient pressure signal.

[00180] Referring now to Figure 20, there is shown a plot 2000 of the composite IRF(corresponding to the deconvolution of P₂/P₁) for the pipeline system in Figure 14 where the pressure signal generator at Gi is generating a persistent micro-transient pressure signal but the pipeline is otherwise configured to have a dead-end configmation where in-line valve Vi is set to be closed. By comparison with Figure 17(a), it can be seen that the magnitudes of the features in Figure 20 are doubled. The leak induced two spikes, which are antisymmetric around (7.0). These observations establish the validity of Equation 20. Case Study 3

Pipeline Configuration - Continuous Single Pipeline with Pipeline Junction at Both Ends Assessment Configuration - Continuous Pipeline Segment with Generation Location External to Pipeline Segment

[00181 ] Referring now to Figure 21, there is shown a figurative view of a pipeline network 2100 for numerically simulating the assessment of a pipeline segment in a pipeline network according to an illustrative embodiment of the present disclosure. In this example, all the pipes in the pipeline network are uniform with an internal diameter of 200 mm, wave speed of 1000 m/s and a Darcy -Weisbach factor f of 0.02. The length of each pipe is given in Figure 21.

[00182] The assessment configuration in this example includes two persistent micro -transient pressure signal generator 2120, 2125 located at Gi and G2 respectively together with two pressure measuring devices 2130, 2140 located at P₁ and P₂ respectively that are located on one pipeline segment in the network. Two leaks Li and L₂ represented by the asterisks in Figure 21 are assumed to be located between the two pressure measuring devices. The diameter of both leaks is 9 mm with corresponding flow rates of 2.0 L/s.

[00 i 83] In this example, signal generator 2120 at Gi is operative and signal generator 2125 at G2 is non-operative for the simulation. Only this case was analysed, as the second case where the signal generator 2125 is operative would be expected to provide very similar results to those observed for the first case.

[00184] Referring now to Figures 22(a) and (b), there are shown plots 2200 of the composite IRF corresponding to P2/P1 for the pipeline network 2100 illustrated in Figure 21. Figure 22(b) is a detailed enlarged view of the Y-axis scale of Figure 22(a).

[00185] According to Figures 22(a) and (b), the principal wave reflections induced by L₁, L₂ (corresponding to R_{R 1} in Equation 11) and J2 (corresponding to R_{R 2}- in Equation 11) can be clearly identified. The distance of J2 to P₂ is 50 m (Lj) and the distance between P₁ and P₂ is 100 m (Z). Since leak Li is within the distance of 50 m (L- Lj) to P₁ and leak L₂ is within the distance of 50 m (L- Lj) to P₂, 2nd-order wave reflections corresponding to R_R,₂PL,2 and R_R,1R_R,2 in Equation 11 can be also observed in Figure 22. Since L- 2L_j = 0 m, 3rd-order wave reflections corresponding to R_R,₂PL^ iⁿ Equation 11 may be neglected. Case Study 4

Pipeline Configuration - Pipeline Junction

Assessment Configuration- Interrupted Pipeline Segment Connected by a Junction with Generation Location External to Pipeline Segment

[00186] Referring now to Figure 23, there is shown a figurative view of a pipeline network 2300 for numerically simulating the assessment of a pipeline segment in a pipeline network according to an illustrative embodiment of the present disclosure. In this example, pipeline network 2300 has the same pipeline configuration as pipeline network illustrated in Figure 21 but a different assessment configuration in that second measurement location P₂ is on a branch pipeline that joins the main pipeline by junction J₅. Furthermore, the locations of the leaks Li and L2 are also different from those depicted in Figure 21.

[00187] Referring now to Figures 24(a) and (b), there are shown plots 2400 of the composite IRF corresponding to P₂/P₁ for the pipeline network 2300 illustrated in Figure 23. Figure 24(b) is a detailed enlarged view of the Y-axis scale of Figure 24(a).

[00188] According to Figures 24(a) and (b), the principal wave reflections induced by L₁, J₅ (corresponding to

in Equation 11) and J3 (corresponding to R_R-2 in Equation 11) can be clearly identified in the composite IRF. The other two small spikes or features labelled in Figure 24(b) are caused by the transfer function H_1-2. The wave path for the spike labelled as H_1-2 (Li) is P1-J5-L1-J5-P₂. The wave path for the spike labelled as H_1-2 (L2) is P1-L2-J5-P₂.

Experimental Validation

Pipeline Configuration - Continuous Single Pipeline

[00189] Referring now Figure 25, there is shown a figurative view of an experimental pipeline network 2500 adopted to validate pipeline network condition assessment methods in accordance with the present disclosure. In this example pipeline network, the pipeline configmation comprises a pipeline loop connected to the water mains system 2550 having a main pipeline 2510, a first branch line 2580 connected at one end to the water mains system 2550 and at the other end to the main pipeline 2510 at junction J_o. Connected to the other end of main pipeline 2510 at junction J₃ is a second branch pipeline 2585 that functions as a return pipeline and connects to the water mains system 2550.

[00190] In this example, main pipeline 2510 (ie, J0-J3) is formed of copper pipe and has an internal diameter D_o of 22.14 mm where the theoretical wave speed of a pressure wave travelling in the pipe is on = 1319 m/s. First branch pipeline 2580 is formed of polymer pipe and second branch pipeline 2585 is formed of copper pipe. Pipeline network is pressurised by the connected municipal water distribution system (WDS) 2550 and background pressure fluctuations and noise from the WDS will propagate to the main pipeline 2510.

[00191 ] In this example, the assessment configuration comprises two pressure measuring devices 2530, 2540 located at P₁ and P₂ respectively as shown in Figure 25. At the same locations, two persistent micro-transient pressure signal generators in the form of side-discharge valves 2520, 2525 are installed (ie, at Gi and G2). If one of the side-discharge valves is partially opened, a persistent micro-transient pressure signal is generated due to the turbulent flow around and through the valve. As has been discussed previously, these pulsating pressure waves (micro-transient waves) are of a small magnitude compared with conventional transient pressure signals that would typically arise from a sudden valve closure.

[00192] By adjusting the opening of the valve, the magnitude and the frequency content of the persistent micro-transient pressure signal may be adjusted. Between the two generators 2520, 2525, an anomaly in the form of a “leak” is provided by a T-junction with a pinhole at its end that is connected with the main pipeline 2510 as indicated by Li in Figure 25 with the goal being to characterize this anomaly by identifying and locating the anomaly. As can be seen, in this example, there are many joints along the pipeline 2510 and these will also potentially cause wave reflections and interfere with the experimental measurements. In this experimental setup, the sampling rate was 10 kHz.

[00193] In the first test, the persistent micro-transient pressure signal generator in the form of side-discharge valve 2520 located at Gi was opened and the side-discharge valve 2525 located at G2 was closed. Accordingly, the assessment configuration is consistent with that depicted in Figure 6 with G located at P₁.

[00194] Referring now to Figures 26(a) and (b), there are shown plots of the measured first (ie, Figure 26(a)) and second (ie, Figure 26(b)) time varying pressure response signals 2610, 2620 for the pipeline system illustrated in Figure 25 where the side-discharge valve 2520 located at Gi is open and generating a persistent micro-transient pressure signal. As can be seen, the measured response signals 2610, 2620 have an overall magnitude of 0.15 m (as shown in the enlargement window in Figure 26) in addition to low-frequency background pressure fluctuations with a magnitude of 2 m. They also contain hydraulic noise from the real city pipe network 2550 connected with the pipeline network 2500.

[00195 ] In the second test, the side-discharge valve 2525 located at G2 was opened and the sidedischarge valve 2520 located at Gi was closed. Accordingly, the assessment configuration in this second test is consistent with that depicted in Figure 6 with G located at P₂. Once again, the measured time varying pressure response signals for this case were similar in overall characteristics to those depicted in Figures 26(a) and (b).

[00196] Referring now to Figures 27(a) and (b), there are shown plots 2700 of the determined composite IRFs for the pipeline system 2500 illustrated in Figure 25 where the composite IRF 2710 (corresponding to P₂/P₁) results from a persistent micro-transient pressure signal being generated at Gi (ie, Figure 27(a)) and the second composite IRF 2720 (corresponding to P₁/P₂) results from a persistent micro-transient pressure signal being generated at G2 (ie, Figure 27(b));

[00197] The pipeline network 2500 may now be assessed based on the composite IRFs, the pipeline configuration and the two different assessment configmations corresponding to the two different locations of the persistent micro-transient pressure signal generator. In the composite IRFs 2710, 2720 in Figure 27, the first spike or feature in each composite IRF (ie, A in Figure 27(a) and D in Figure 27(b)) indicates the injected pressure signal wave after propagating along the pipeline segment P₁ - P₂ between the two pressure measuring devices and the corresponding time is the single-trip travel time (772) for the micro-transient waves. For the two composite IRFs 2710, 2720, the single-trip travel times are 0.0143 s and 0.0144 s and thus an average of 0.01435 s is chosen. On this basis, for the selected pipeline segment of interest, the relevant time window (ie, from T/2 to 3772) may then be determined as being 0.01435 s to 0.4305 s.

[00198] By inspection, another two anomaly reduced reflections (B and C in Figure 27(a)) can be found at 0.0277 s and 0.0421 s. In accordance with Equation 19, the corresponding distances to P₁ or P₂ may be calculated as 8.80 m and 18.30 m. Based on the magnitude of the anomaly induced wave reflection and the distance calculated, the feature at 0.0421 s is ascribed to the junction J₃, and the feature at 0.0277 s is determined to be induced by the anomaly Li. The distance from the anomaly to P₁ is 8.80 m and includes the length of the short branch in Li, which is about 5 cm, and thus the corrected distance is 8.75 m.

[00199] For the pressure deconvolution trace P₁/P₂ of the second test, Equation 21 may be used to explain the features in the composite IRF. A major reflection (G) can be found at 0.0429 s in Figure 27(b) and it can be ascribed to the junction J₀. Another two anomaly induced reflections (ie, E and F) with different magnitudes can be observed and the corresponding times are 0.0277 s and 0.0297 s which are symmetric around (7.0). Thus, these anomaly induced reflections are both induced by the anomaly Li. The anomaly induced reflection at 0.0297 s with a larger magnitude belongs to wave reflections in R_{R 1} in Equation 21, while the other spike belongs to wave reflections in in the equation. The

corresponding (corrected) distance for the spike at 0.0277 s is 8.75 m to P₁, and that for the spike at 0.0297 s is 10.07 m to P₂ (or 8.74 m to P₁). [00200] Based on the analyses above, the calculated distances were compared with the measured values in Table 2 set out below noting that Lc is the calculated distance to P₁ or P₂ (m), and Lm is the actual measured distance (m).

[0020] ] The small discrepancy shown in the table demonstrates the high accuracy of the assessment method and system in accordance with the present disclosure. Apart from the major spikes that can be easily observed in these composite IRFs, some very small features can be also observed. They are mostly caused by the pipe joints, numerical errors, neglected higher-order wave reflections and other uncertainties associated with the experiments.

TABLE 2

Accuracy analysis of the detection result.

[00202] Referring now to Figure 28, there is shown a plot 2800 overlaying the composite IRF 2810 of Figure 27(a) with the time reversed composite IRF 2720 of Figure 27(b). In this example, to highlight the anomaly between the pressure sensors 2530, 2540 illustrated in Figure 25, the time window selected was from T/2 to T/2 and the time-reversal processing was applied to the composite IRF corresponding to P₁/P₂. In accordance with the theoretical analyses, the overlapping spikes (B in Test 1 and F in Test 2) are caused by the anomaly induced wave reflections in the pipe segment between the pressure sensors 2530, 2540 and thus the anomaly Li can be detected based on the spikes in the dashed rectangle in Figure 28.

[00203] As is apparent from the above test results, method and systems for assessing the condition of a pipeline network in accordance with the present disclosure may be run in parallel with approaches that are based on introducing a short transient pressure pulse especially where the short transient pressure pulse is generated by the abrupt shutoff of an outlet valve as in the field test referred to above. In this case, the persistent micro-transient pressure signal may be obtained from the initial hydroacoustic noise generated by water flowing out of the outlet valve which will occur for a period of time prior to closing the outlet valve. Measurement of the pressure response signals at measurement locations for this time period prior to closing of the outlet valve may then be processed to determine the composite IRF function and the pipeline may be assessed accordingly. This characterisation may then be compared to the results obtained from pressure response measurements obtained after generation of the short term pressure pulse once the outlet valve has been closed.

[00204] As would be appreciated, the methods and systems described above represent a significant advance in assessing the condition of a pipeline and in particular for those pipeline networks where access to the pipeline is limited and/or where the use of short transient pressure pulses may present a risk of causing damage to the pipeline itself. In contrast to this, assessment methods and system in accordance with the present disclosure are based on a persistent micro -transient pressure signal which in one example may be hydro-acoustic noise already emitted by the pipeline. These relatively small pressure variations are unlikely to cause damage to the pipeline. Furthermore, there is no requirement that the pressure sensors need to be closely spaced meaning that already available access points to the pipeline may be utilised such as hydrants and/or air valves. This approach is especially practical in water transmission and distribution systems since distributed access points already exist in these pipeline systems. In one aspect, the measurements from different assessment configmations where the pairs of sensors and the persistent micro-transient pressure signal generator are at different locations with respect to the pipeline segment of interest, may be combined to improve the sensitivity of the assessment method.

[00295] Those of skill in the art would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software or instructions, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. As would be appreciated, the described functionality maybe in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. [00206] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.

[00207] It will be understood that the terms “comprise” and “include” and any of their derivatives (e.g. comprises, comprising, includes, including) as used in this specification, and the claims that follow, is to be taken to be inclusive of features to which the term refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied.

[00208] In some cases, a single embodiment may, for succinctness and/or to assist in understanding the scope of the disclosure, combine multiple features. It is to be understood that in such a case, these multiple features may be provided separately (in separate embodiments), or in any other suitable combination. Alternatively, where separate features are described in separate embodiments, these separate features may be combined into a single embodiment unless otherwise stated or implied. This also applies to the claims which can be recombined in any combination. That is a claim may be amended to include a feature defined in any other claim. Further a phrase referring to “at least one of’ a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.

[00209] It will be appreciated by those skilled in the art that the disclosure is not restricted in its use to the particular application or applications described. Neither is the present disclosure restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the disclosure is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope as set forth and defined by the following claims.

Claims

1. A method for assessing a condition of a pipeline network having a pipeline configuration, comprising: generating at a generation location a persistent micro-transient pressure signal in a fluid being conveyed by the pipeline network; measuring at a first measurement location on the pipeline network a first time varying pressure response signal; measuring at a second measurement location on the pipeline network a second time varying pressure response signal, the second measurement location spaced apart from the first measurement location, wherein the generation location, first measurement location and second measurement location define an assessment configuration; determining a composite impulse response function (IRF) for the pipeline network based on the first time varying pressure response signal and the second time varying pressure response signal; and assessing the condition of the pipeline network based on the composite IRF, the pipeline configuration and the assessment configmation.

2. The method for assessing a condition of a pipeline network of claim 2, wherein determining the composite IRF comprises: deconvolving the first and second time varying pressure response signals with respect to each other.

3. The method for assessing a condition of a pipeline network of claim 1 or 2, wherein the pipeline configuration comprises a junction between a first pipeline and a second pipeline and wherein the first measurement location is located on the first pipeline and the second measurement location is located on the second pipeline.

4. The method for assessing a condition of a pipeline network of claim 1 or 2, wherein the pipeline configuration comprises a first pipeline forming part of a transmission pipe of a water network and wherein the first and second measurement locations are located on the first pipeline.

5. The method for assessing a condition of a pipeline network of any one of claims 1 to 4, wherein the generation location is the same as either the first measurement location or the second measurement location.

6. The method for assessing a condition of a pipeline network of any one of claims 1 to 4, wherein the generation location is located externally to a region defined between the first measurement location and the second measurement location.

7. The method for assessing a condition of a pipeline network of any one of claims 1 to 4, wherein the generation location is located between the first measurement location and the second measurement location.

8. The method for assessing a condition of a pipeline network of any one of claims 1 to 7, wherein characterising the pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration comprises: selecting a pipeline segment of the pipeline network; determining a first time window in the composite IRF corresponding to the selected pipeline segment based on a relationship of the selected pipeline segment with the pipeline configuration and the assessment configuration; and determining one or more anomaly induced wave reflections within the first time window to identify one or more anomalies in the selected pipeline segment.

9. The method for assessing a condition of a pipeline network of claim 8, wherein a location or locations of the one or more anomalies are determined by a timing analysis of the one or more anomaly induced wave reflections in the composite IRF.

10. The method for assessing a condition of a pipeline network of claim 8 or 9, wherein the pipeline segment is located between the first and second measurement locations.

11. The method for assessing a condition of a pipeline network of any one of claims 8 to 10, further comprising: generating at a second generation location a persistent micro-transient pressure signal in the fluid being conveyed by the pipeline network; measuring at a third measurement location on the pipeline network a third time varying pressure response signal; measuring at a fourth measurement location on the pipeline network a fourth time varying pressure response signal, wherein the second generation location, the third measurement location and the fourth measurement location together define a second assessment configuration, and wherein the selected pipeline segment is between the third and fourth measurement locations; determining a second composite IRF for the pipeline network based on the third time varying pressure response signal and the fourth time varying pressure response signal, the pipeline configuration and the second assessment configuration; and assessing the condition of the selected pipeline segment based on the second composite IRF, the pipeline configuration and the second assessment configuration.

12. The method for assessing a condition of a pipeline network of claim 11, wherein assessing the condition of the selected pipeline segment based on the second composite IRF, the pipeline configuration and the second assessment configuration comprises: determining a second time window in the second composite IRF corresponding to the selected pipeline segment based on a relationship of the selected pipeline segment with the pipeline configuration and the second assessment configuration; determining one or more anomaly induced wave reflections within the second time window to identify one or more anomalies in the selected pipeline segment; and comparing the one or more anomaly induced wave reflections determined within the second time window to the one or more anomaly induced wave reflections determined within the first time window.

13. A system for assessing a condition of a pipeline network having a pipeline configuration, the system including: a persistent micro-transient pressure signal generator for generating at a generation location a persistent micro-transient pressure signal in a fluid being conveyed by the pipeline network; a first pressure measuring device for measuring at a first measurement location on the pipeline network a first time varying pressure response signal; a second pressure measuring device for measuring at a second measurement location on the pipeline network a second time varying pressure response signal, the second measurement location spaced apart from the first measurement location, wherein the generation location, first measurement location and second measurement location define an assessment configuration; an analysis module comprising one or more data processors configmed for: determining a composite impulse response function (IRF) for the pipeline network based on the first time varying pressure response signal and the second time varying pressure response signal; and assessing the condition of the pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration.

14. The system for assessing a condition of a pipeline network of claim 13, wherein determining the composite IRF comprises: deconvolving the first and second time varying pressure response signals with respect to each other.

15. The system for assessing a condition of a pipeline network of claim 13 or 14, wherein the pipeline configuration comprises a junction between a first pipeline and a second pipeline and wherein the first measurement location is located on the first pipeline and the second measurement location is located on the second pipeline.

16. The system for assessing a condition of a pipeline network of claim 13 or 14, wherein the pipeline configuration comprises a first pipeline forming part of a transmission pipe of a water network and wherein the first and second measurement locations are located on the first pipeline.

17. The system for assessing a condition of a pipeline network of any one of claims 13 to 16, wherein the generation location is the same as either the first measurement location or the second measurement location.

18. The system for assessing a condition of a pipeline network of any one of claims 13 to 16, wherein the generation location is located externally to a region defined between the first measurement location and the second measurement location.

19. The system for assessing a condition of a pipeline network of any one of claims 13 to 16, wherein the generation location is located between the first measurement location and the second measurement location.

20. The system for assessing a condition of a pipeline network of any one of claims 13 to 19, wherein characterising the pipeline network based on the composite IRF, the pipeline configuration and the assessment configuration comprises: selecting a pipeline segment of the pipeline network; determining a first time window in the composite IRF corresponding to the selected pipeline segment based on a relationship of the selected pipeline segment with the pipeline configuration and the assessment configuration; and determining one or more anomaly induced wave reflections within the first time window to identify one or more anomalies in the selected pipeline segment.

21. The system for assessing a condition of a pipeline network of claim 20, wherein a location or locations of the one or more anomalies are determined by a timing analysis of the one or more anomaly induced wave reflections in the composite IRF.

22. The system for assessing a condition of a pipeline network of claim 20 or 21, wherein the pipeline segment is between the first and second measurement locations.

23. The system for assessing a condition of a pipeline network of claims 20 to 22, further comprising: generating at a second generation location a persistent micro-transient pressure signal in the fluid being conveyed by the pipeline network; measuring at a third measurement location on the pipeline network a third time varying pressure response signal; measuring at a fourth measurement location on the pipeline network a fourth time varying pressure response signal, wherein the second generation location, the third measurement location and the fourth measurement location together define a second assessment configuration, and wherein the selected pipeline segment is between the third and fourth measurement locations; determining a second composite IRF for the pipeline network based on the third time varying pressure response signal and the fourth time varying pressure response signal, the pipeline configuration and the second assessment configuration; and assessing the condition of the selected pipeline segment based on the second composite IRF, the pipeline configuration and the second assessment configuration.

24. The system for assessing a condition of a pipeline network of claim 23, wherein assessing the condition of the selected pipeline segment based on the second composite IRF, the pipeline configuration and the second assessment configuration comprises: determining a second time window in the second composite IRF corresponding to the selected pipeline segment based on a relationship of the selected pipeline segment with the pipeline configuration and the second assessment configuration; determining one or more anomaly induced wave reflections within the second time window to identify one or more anomalies in the selected pipeline segment; and comparing the one or more anomaly induced wave reflections determined within the second time window to the one or more anomaly induced wave reflections determined within the first time window.

25. A system for assessing a condition of a pipeline network having a pipeline configuration comprising means for carrying out the method of any one of claims 1 to 12.