AU2020104206A4

AU2020104206A4 - Leak detection and location system

Info

Publication number: AU2020104206A4
Application number: AU2020104206A
Authority: AU
Inventors: Carl Buckeridge; William Smith
Original assignee: Leakster Pty Ltd
Current assignee: Leakster Pty Ltd
Priority date: 2018-08-17
Filing date: 2020-12-21
Publication date: 2021-03-11
Anticipated expiration: 2027-08-15

Abstract

A fluid leak detection system to detect the fluid leak in a conduit containing fluid, the system including at least one wave emitter to introduce at least one excitation wave into at least the fluid in the conduit, at least one detector to detect at least noise in the fluid in the conduit, and at least one processor to compare the noise detected to the at least one excitation wave introduced to detect any altered waves in the fluid indicative of a leak.

Description

LEAK DETECTION AND LOCATION SYSTEM TECHNICAL FIELD

[0001] The present invention relates generally to the field of fluid dynamics and particularly to a leak detection and location system based on sound or wave propagation in a fluid that does not utilise an echo.

BACKGROUND ART

[0002] It is known that conduits carrying fluids can develop leaks in many forms. Leaks in underground conduits such as water supply mains can be difficult to locate and expensive if left untended as the leak tends to develop as a point of weakness eventually resulting in catastrophic failure of the conduit which is typically the first time a leak is identified.

[0003] Traditional methods of leak detection in underground or buried conduits include tracking water losses with flow measurements and consumption or using microphones above ground. These methods are extremely time consuming and labour intensive as well as being generally imprecise in identifying the particular location of the leak.

[0004] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

[0005] The present invention is directed to a pipe leak detection and location system, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

[0006] With the foregoing in view, the present invention in one form, resides broadly in a fluid leak detection system to detect a fluid leak at a fluid/solid boundary, the system including at least one wave emitter to introduce at least one excitation wave into at least the fluid, at least one detector to detect at least noise in the fluid, and at least one processor to compare the noise detected to the at least one excitation wave introduced to detect any altered waves in the fluid indicative of a leak.

[0007] The present invention operates on the principle that when a leak forms, cavitation at the leak site causes a sound wave in the water. The detector in the conduit detects this sound wave. The present invention uses an emitter to introduce at least one excitation wave or ping into the fluid. The pressure wave from the ping causes a change in the sound wave being made at the leak. The altered sound is then detected at the detector and/or an altered vibration can be detected in the conduit wall. The sound alteration can be by one or more effects:

• Suppressing the existing cavitation. • Exciting the cavitation frequencies to a higher state by compressing the vortices • Creating new vortices and new cavitation frequencies by inducing a transient pressure drop at borderline regions.

[0008] The distance to the leak can then be measured by recording the time delay from the transmission of the ping (pulse) to the detection of the altered leak noise or vibration based on the speed of transmission of sound in the particular medium of the fluid and/or the wall material. For example, the speed of sound in water is about 1500 meters per second. If there is a 1 second lapse from the time of transmission of the ping to the detection of an altered noise, then the distance to the leak is about 750 meters.

[0009] Typically, the comparison of the noise detected will include the comparison of the noise detected when the at least one excitation wave is being emitted to the noise detected when the at least one excitation wave is not being emitted. In other words, the comparison will typically include a comparison of the noise present when the ping is on to the noise when the ping is off.

[0010] The system of the present invention will find application in many fields and circumstances including

• Fixed pipe network monitoring;

• Portable condition monitoring;

• Intrinsically safe petrochemical pipeline monitoring;

• Stealthy sonar addition to passive array (single pulsed pressure method);

• Hull leak detection;

• Dam leak detection including mine tailing dams;

• Boiler pressurized water or cooling or feedwater pipes;

• Reactor cooling water pipes;

• Oil well monitoring; and

• Erosion detection from cavitation Detection of cavitation induced by erosion/corrosion

• Detection of turbulent flow in air and gas leaks.

• Ranging of air and gas leaks via sound suppressing wave transmission

[0011] A fluid/solid boundary will exist in a variety of locations and configurations and the system of the present invention may be used with pipes or conduits through which fluids flow or in which a fluid exists, or other substances such as ships hulls and dam walls.

[0012] Without wishing to be limited by theory, the inventors understand that when cavitation occurs in a fluid, it causes a sound wave with a frequency related to the rotational velocity of the vortex and a frequency related to the formation and dissipation of the individual cavities.

[0013] Introducing one or more soundwaves into the fluid in the conduit typically interferes with the cavitation produced by the leak and to the interference or altered noise is detectable by the at least one detector. Further, the time delay between the emission/introduction of the sound wave into the fluid and the detection of the altered soundwave can be used to provide a ranging calculation based on the speed of sound in the particular fluid. This allows not only detection of a leak but also quite precise measurement of the location of the leak, typically in distance terms relative to the detector rather than the emitter.

[0014] The system of the present invention detects and isolates the frequencies of sound caused by this cavitation. The system emits a sound or pressure wave that interferes with the cavitation that causes the noise. The time delay between emitting a sound or pressure wave up until the noise is modified is used to provide ranging calculations from the speed of sound in that fluid.

[0015] The nearest prior art is likely to be legacy sonar systems which transmit a sound wave and read back a reflected wave or echo then perform a range calculation. These legacy sonar systems do not work on leaks because the there are no features of the leak to reflect a sound wave frequency back to the point of emission.

[00161 In contrast, the present invention functions to temporarily stifle, excite or induce noise frequency bands of the cavitation caused by a leak or push them into higher frequencies by compressing the vortices which then spin around a tighter circumference but conserve enough momentum to retain linear velocity (Same velocity in a smaller radius = higher rpm and higher frequency). Alternatively, the system of the present invention may induce new transient frequencies in transitional regions.

[0017] The present invention is therefore directed to the introduction of at least one excitation wave or ping into at least the fluid and/or the conduit itself and then the detection of an altered characteristic in relation to the wave, noise or vibration in the conduit which would occur if a leak is present. Importantly, the present invention is not dependent upon a return signal is the characteristics of a leak such that there is typically not a sufficient return signal to allow detection. Instead, the present invention uses the detection of an altered characteristic, typically travelling in the same direction as the at least one excitation wave or ping.

[0018] As mentioned above, the present invention may include the introduction of vibrations induced vibrations or sound waves or created in a wall of the conduit. This can occur as result of the at least one excitation wave introduced into the fluid and/or a separate emitter to introduce vibration may be provided.

[0019] The system of the present invention may provide superior leak detection functionality when the fluid in the conduit is not flowing. However, the system of the present invention can be optimised for use in situations where the fluid is flowing in the conduit and may be optimised for high flow rates and/or high velocity flow which typically involves increased pressures making the introduction of the at least one excitation wave more difficult, or requiring more power to create an effective at least one excitation wave.

[0020] The at least one excitation wave will typically be created depending upon properties of the fluid including, but not limited to the pressure, velocity (whether expressed as a vector or a scalar) the Reynolds number of the fluid or a portion of fluid, if flowing and the flow rate. Typically, the introduction of the at least one excitation wave will create changes in the pressure in the fluid as a result of the soundwave pressure front.

[0021] The typical cavitation frequencies affected by the at least one excitation wave will be between 10 and 20 kHz and typically around 14 to 15 kHz at least for smaller leaks although different sized leaks may result in different cavitation frequencies. Not all turbulence will be sufficient to cause cavitation. For cavitation to occur, the pressure needs to drop below the vapour pressure of the fluid plus the static pressure. A leak in a sealed conduit however will generally be from a higher-pressure environment to an atmospheric pressure environment which generally creates ideal conditions for cavitation to exist when a leak is present.

[0022] Again, without wishing to be limited by theory, when centrifugal forces in the vortex are sufficient to overcome the static plus vapour pressure, then noise emitting cavitation occurs. If the energy to maintain the cavity is marginal, then the system of the present invention can completely suppress it with the ping. If the centrifugal force is sufficient to maintain enough pressure to counteract the static pressure plus vapour pressure plus ping pressure, then the vortex will be compressed to a tighter diameter causing faster revolution and hence higher frequency. Note that a rotational vortex that lacks energy to cavitate may be induced into a high frequency transient cavitation with the passage of the low-pressure side of a ping wave. This has been observed in tests and forms the basis for submarine detection via a single pressure wave in a non cavitating propeller.

[0023] The present invention includes at least one emitter and the purpose of the emitter is to generate a sound wave or ping in order to alter the characteristics of any cavitation voids present in the fluid due to the presence of a leak and preferably, to collapse, excite or induce at least some of the cavitation voids under the increased and decreased pressure of the at least one excitation wave. Typically, the emitter will be configured to emit a sound wave or ping in fluids having pressures up to approximately 1000 kPa. The emitter will typically be able to withstand spikes in fluid pressure of up to 3000 kPa.

[0024] The emitter will preferably be able to emit at least one excitation wave at a variety of frequencies as may be required by different fluids and/or the pressure in the fluid being tested. In a particularly preferred form, the at least one emitter will have sufficient energy to propagate a sound wave over significant distance. The distance will normally be the test distance and the test distance may vary from a number of meters for some uses up to 1000 m for other uses. Note that ranges are likely to exceed this distance when the technology is perfected. 5 km on long pipe runs is a realistic target. In open ocean, this distance could be much longer.

[0025] The at least one excitation wave or ping is preferably an ultrasonic wave, a particularly preferred frequency for which is approximately 425 Hz in water for example. The frequency of the excitation wave or ping may vary for different fluids and will typically be optimised for the particular fluid being tested.

[0026] As mentioned above, in use, the introduction of the at least one excitation wave will typically modify or eliminate one or more bands of noise generated by the leak. Therefore, the system of the present invention will typically analyse the difference in noise detected between when the excitation wave is introduced and when the excitation wave is not present in order to detect differences between the two situations indicative of a leak. Typically, the system of the present invention will do this by signal or data analysis and it is particularly preferred that for rear series analysis is undertaken, preferably fast Fourier transform analysis.

[0027] The system of the present invention may be used to match the leak noise data with a wall vibration data and detect changes in wall vibration data that may be indicative of the presence of a leak due to changes in the wall vibration from the emitter to the leak and between the leak and the detector. As mentioned above, a separate emitter may be provided within the system of the present invention to introduce a wall vibration and/or the soundwave emitter used to introduce the at least one excitation wave into the fluid may also introduce a vibration in the conduit wall.

[0028] The emitter of a preferred embodiment will preferably have a diaphragm which is movable in order to introduce the at least one excitation wave. The diaphragm will typically enable Uni axial transmission of the at least one excitation wave. Preferably, the emitter will create a sinusoidal (There are merits for a sawtooth wave however this makes a large number of higher terms in a Fourier series) waveform with minimal side bands. The emitter will preferably be capable of variable power output as required by the fluid and/or the test distance.

[0029] In keeping with the present invention, the creation of a return wave (or echo) is far less important than the creation of an optimum excitation wave as the detector/receiver used in the present invention means that the invention does not operate on the principles of reflection of the excitation wave. Specifically, the purpose of the excitation wave is to change the noise emitted by cavitation. The system then detects this change. The energy requirements are much less.

[0030] It is preferred that the emitter will propagate the wave in a single direction only.

[0031] Typically, the detector is spaced from the emitter (although they may be provided at the same position, for example is provided in the same unit). In a particularly preferred embodiment, the detector will be located on one side of the leak and the emitter will be located on the opposite side of the leak from the detector.

[0032] The emitter may be of any type. In one particularly preferred form, the emitter will typically create an excitation wave pulse or ping by applying a negative voltage at a solenoid to move the diaphragm, which is typically associated with a magnet or similar in order to seat the diaphragm hard against a preferred ferrite core in the solenoid. The application of a positive voltage will then typically drive the diaphragm forward in order to create the at least one excitation wave pulse or ping. Clearly the opposite voltage configuration could also be used if desired. The invention preferably does not rely on the particular mechanism for creating the excitation wave pulse or ping merely that an excitation wave pulse or ping be introduced and then the system can monitor for altered noise as a result.

[0033] The emitter may be located relative to the conduit in any location in order to allow the at least one excitation wave to be generated, preferably emitted substantially in line with the conduit.

[0034] The system of the present invention also includes at least one detector in order to detect noise in the fluid in the conduit. The at least one detector can be provided in any location relative to the emitter. As mentioned above, the detector and emitter may be in the same position, or the detector may be on one side of the leak and the emitter on the other side of the leak, or the detector and emitter may be located at different locations on the same side of the leak. Of course, the operator will not necessarily know, although they may suspect, the location of the leak and therefore, in usual operation, the at least one emitter will be provided relative to one portion of the conduit and the at least one detector will be provided relative to the conduit spaced apart from the emitter in order to define a test length. The operator can then test that length and subsequent lengths in order to test the conduit. The operator will typically use an overlapping test length in order to ensure that if a leak is present, it can be detected. The operator will typically move the emitter and detector along the conduit as a result to test different test lengths.

[0035] The detector may be of any type. In a particularly preferred embodiment, the detector may be or include a hydrophone.

[0036] It is preferred that the emitter and detector will be provided as a single unit in order to accomplish both functions with a single unit. However, the at least one emitter and at least one detector may be provided as separate devices.

[0037] In use, the at least one detector will typically be mounted substantially coaxially with the length of the conduit.

[0038] As mentioned above, one or more additional emitters and one or more additional detectors may be provided in order to introduce a vibration wave into one or more walls of the conduit. A single emitter may introduce both the excitation wave ping into the fluid and create a vibration wave in one or more walls of the conduit. If a single emitter is used for both purposes, it is preferred that one or more detectors are used to detect both the noise in the fluid and the vibration in the conduit.

[0039] The system of the present invention will also include at least one processor. The processor will typically provide a control and/or analysis function to the present invention. The processor will normally operate software adapted to control the emitter and the parameters of the at least one excitation wave. The particular parameters of operation may be user-defined and/or provided as a part of the software operating system to allow the software to control the parameters and/or any optimisation of the parameters may be required.

[0040] The at least one processor will preferably receive the data in relation to the noise in the conduit when the ping is off, the noise in the conduit when the ping is on and/or in relation to the at least one excitation wave itself in order to take this data into account in the analysis. The at least one processor will preferably receive information from both the emitter and the detector.

[0041] A software application is preferably provided in order to undertake the analysis. This offer application is preferably provided to control the system and the components within the system. A software application may be provided for each function are preferably, a single software application is provided for control and analysis of the system overall.

[0042] As will be relatively clear at this point, the analysis of the information is particularly important in order to not only locate the presence of a leak but also to locate, if possible the position or location of the leak relative to one or more components of the system.

[0043] The data analysis will normally begin with data which is received by the processor. The data received by the processor will typically include noise data and/or vibration data. The data will typically include noise data and/or vibration data when the at least one excitation wave pulse or ping is on or being introduced and when the at least one excitation wave pulse or ping is off.

[0044] The data in relation to the noise which is collected is typically then analysed in comparisons made in order to determine whether a leak is present or not. The data may require some analysis before the comparison can actually be made in order to ensure that the data which is being compared is the relevant data. In this respect, the data will typically undergo Fourier analysis typically being analysed according to a fast Fourier transform in order to create a fast Fourier transform dataset. Once this has been achieved, a baseline or threshold is preferably provided and applied to the fast Fourier transform dataset. The baseline or threshold will typically be chosen by the user and/or the software application and will preferably be adjustable depending upon the system parameters and also the parameters of the fluid.

[0045] The system will preferably note how the dataset between 10 to 20 kHz changes after the ping transitions from off to on, and from on to off.

[0046] When the ping transitions from off to on the system will typically start a timer to note the time taken for the amplitude of a variety of frequencies to decrease to a fraction of the baseline or threshold. The fraction of the baseline will typically be chosen by the user and/or the software application and will preferably be adjustable depending upon the system parameters and also the parameters of the fluid.

[0047] When the ping transitions from on to off the relevant data will preferably be processed in order to note the time taken for the amplitude of a variety of frequencies to increase to a fraction of the baseline or threshold. The fraction of the baseline will typically be chosen by the user and/or the software application and will preferably be adjustable depending upon the system parameters and also the parameters of the fluid.

[0048] For each ping transition from off to on, and from on to off, once the chosen user and/or software application fraction of the baseline or threshold has been satisfied, the system will typically stop a clock or timer. If a leak is not detected over a number of cycles, the system will typically determine the leak is not present, continue monitoring for a preset time and then terminate unless a leak is detected.

[0049] The system will preferably process the noted timeframes to minimise any spikes or spurious data points. The system will typically process the noted timeframes by averaging their values.

[0050] The location of the leak can be calculated based on the speed of the wave in the particular fluid. For example, the speed of a wave in water is approximately 1500 m/s. The time from the processed noted timeframes and the speed of the wave propagation in the fluid can then be used to calculate a distance to the leak from the detector.

[0051] A similar process to that described above will typically be used if the data provided is data in relation to the vibration induced in a wall of the conduit.

[0052] Further, results produced from the analysis of the fluid can be used in combination with the results produced in relation to the vibration to give a more accurate identification of whether a leak is present and/or a more precise location for the leak over the length of the conduit being tested.

[0053] In another form, the present invention resides in a fluid leak detection method to detect the fluid leak at a fluid/solid boundary, the method including the steps of:

• Collect data points in the form of a voltage feed back from a hydrophone with respect to time for at least one excitation wave introduced into at least the fluid and at least one resultant noise characteristic;

• Apply Fourier series calculations to the data points;

• Apply iterations of Fourier series calculations to samples of the data points in order to isolate particular frequencies for analysis to identify where in a time domain that particular frequencies appear and disappear;

• Calculate a time delay and distance from ping transmission or stoppage to leak noise abnormality or normalization; and

• Calculate distance.

[0054] In a preferred form, the method may further include the steps of:

• Average data within a time span corresponding to a selectable maximum size wavelength so as to effectively filter out the effects of lower frequencies.

• From this average, calculate the difference from average of all subsequent data points.

• From these data point difference values, to filter out values above and below selectable percentages of the maximum value. For example, the top 2% and bottom 10% of differences may be ignored. This leaves a remaining data set

• Analyse the remaining data set to isolate patterns of minima and maxima

• Analyse the patterns of minima and maxima for equi-spaced data. Note that this can be a best fit search or a Fourier series calculation on the data set.

• Calculate frequencies and magnitudes of the equi-spaced patterns and save these numbers.

• Repeat the procedure along the time span comparing the resultant frequencies and magnitudes for either:

o Frequency shifts

o Frequency band loss (snubbing)

• Calculate the time delay and distance from ping transmission or stoppage to leak noise abnormality or normalization.

• Calculate distance.

[0055] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0056] 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 the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

[0057] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[0058] Figure 1 is a schematic illustration of a length of pipe with a fluid inside and showing a leak with the leak pressure waves illustrated as well as the pipe vibrations.

[0059] Figure 2 is a schematic illustration showing an emitter and receiver according to the present invention provided on the conduit as illustrated in Figure 1 and showing the introduction of at least one excitation ping signal.

[0060] Figure 3 is a more detailed review of a portion of the pipe illustrated in Figure 2 showing the interaction of the leak pressure waves and the ping signal adjacent to the transmitter.

[00611 Figure 4 is a more detailed view of a second portion of the pipe illustrated in Figure 2.

[0062] Figure 5 is a more detailed view of a third portion of the pipe illustrated in Figure 2.

[0063] Figure 6 is a view similar to that illustrated in Figure 5 but in relation to the vibrations in the pipe rather than the waves in the fluid according to a preferred embodiment of the present invention.

[0064] Figure 7 is an axonometric view of a test rig according to a preferred embodiment of the present invention.

[0065] Figure 8 is an axonometric view of the control and analysis equipment associated with the test rig is illustrated in figure 7 according to a preferred embodiment.

[0066] Figure 9 is a plan view of an emitter and fluid entry which is a part of the test rig illustrated in Figure 7.

[0067] Figure 10 is a plan view of a detector which is a part of the test rig illustrated in Figure 7.

[0068] Figure 11 is an axonometric view of a simulated leak forming part of the test rig illustrated in Figure 7.

[0069] Figure 12 is an amplitude versus time graph showing the detector signal at 18kHz according to a preferred embodiment of the present invention, including the thresholds that are typically used at 18kHz to calculate the distance from the detector to the leak.

[0070] Figure 13 is an amplitude versus time graph showing the detector signal after the emitter has transitioned from ping on to ping off in the presence of a leak, including the thresholds that are typically used at 18kHz to calculate the distance from the detector to the leak. The Figure highlights one of the values that the system would, for this example, suggest the leak distance after applying the below algorithm.

[0071] Figure 14 is an amplitude versus time graph showing the detector signal after the emitter has transitioned from ping off to ping on in the presence of a leak, including the thresholds that are typically used at 18kHz to calculate the distance from the detector to the leak. The Figure highlights one of the values that the system would, for this example, suggest the leak distance after applying the below algorithm.

[0072] Figure 15 is a representation of the nominated leak distance points for numerous samples at various frequencies, and the average of the nominated leak distances.

DESCRIPTION OF EMBODIMENTS

[0073] According to a particularly preferred embodiment of the present invention, a leak detection system is provided and a leak detection system is also provided with location functionality in order to determine the location of the leak relative to it least one component of the system.

[0074] Figure 1 is a schematic illustration of a length of pipe 10 with a fluid inside and showing a leak 11 with the leak pressure waves illustrated as well as the pipe vibrations. Figure 2 is a schematic illustration showing an emitter 12 and receiver 13 according to the present invention provided on the pipe 10 as illustrated in Figure 1 and showing the introduction of an excitation ping signal. This setup will be discussed further below in relation to the test rig illustrated in Figure 7.

[0075] Figure 3 is a more detailed review of a portion of the pipe illustrated in Figure 2 showing the interaction of the leak pressure waves (travelling right to left) with the ping signal (travelling left to right) adjacent to the transmitter.

[0076] Figure 4 is a more detailed view of a second portion of the pipe illustrated in Figure 2 in and around the leak. This figure shows the ping signal reaching the leak and in this embodiment, neutralising the first pressure wave downstream of the leak as the ping signal passes the leak point.

[0077] Figure 5 is a more detailed view of a third portion of the pipe illustrated in Figure 2 showing the removal of a signal band in the noise downstream of the leak and also showing the vibrations in the pipe wall. Figure 6 is a view similar to that illustrated in Figure 5 but in relation to the vibrations in the pipe rather than the waves in the fluid according to a preferred embodiment of the present invention.

[0078] Figure 7 is an axonometric view of a test rig according to a preferred embodiment of the present invention. The test rig includes an elongate pipe 10 with an emitter assembly 12 at one end and a detector 13 at the opposite end. Between the emitter assembly 12 and detector 13 is a valve 14 used to simulate a leak. Figure 8 shows the control and analysis equipment associated with the test rig is illustrated in Figure 7 according to a preferred embodiment.

[0079] Figure 9 is a plan view of a hydrophone emitter 12 and fluid entry 15 which is a part of the test rig illustrated in Figure 7. Figure 10 shows a hydrophone detector 13 which is a part of the test rig illustrated in Figure 7. Figure 11 shows the valve 14 for simulating a leak is the test rig illustrated in Figure 7.

[0080] The fluid leak detection system to detect the fluid leak in a conduit containing fluid, the system if the preferred embodiment includes a hydrophone wave emitter to introduce an excitation wave or ping into the fluid in the conduit, a hydrophone detector to detect noise in the fluid in the conduit, and a processor to control the operation of the emitter and detector and compare the noise detected to the excitation wave introduced to detect any altered waves in the fluid indicative of a leak in the conduit.

[0081] Typically, the comparison of the noise detected will include the comparison of the noise detected when the at least one excitation wave is being emitted to the noise detected when the at least one excitation wave is not being emitted. In other words, the comparison will typically include a comparison of the noise present when the ping is on to the noise when the ping is off.

[0082] The present invention is therefore directed to the introduction of at least one excitation wave or ping into at least the fluid and/or the conduit itself and then the detection of an altered characteristic in relation to the wave, noise or vibration in the conduit which would occur if a leak is present. Importantly, the present invention is not dependent upon a return signal is the characteristics of a leak such that there is typically not a sufficient return signal to allow detection. Instead, the present invention uses the detection of an altered characteristic, typically travelling in the same direction as the at least one excitation wave or ping.

[0083] As mentioned above and shown in the Figures, the invention may include the introduction of vibrations induced or created in a wall of the pipe 10. This can occur as result of the excitation wave introduced into the fluid and/or a separate emitter to introduce vibration may be provided.

[0084] The typical cavitation frequencies affected by the at least one excitation wave will be between 10 and 20 kHz and typically around 14 to 15 kHz at least for smaller leaks although different sized leaks may result in different cavitation frequencies. All turbulence will be sufficient to cause cavitation. For cavitation to occur, the pressure needs to drop below the vapour pressure of the fluid. A leak in a sealed conduit however will generally be from a higher-pressure environment to an atmospheric pressure environment which generally creates ideal conditions for cavitation to exist when a leak is present.

[0085] The present invention includes a hydrophone emitter 12 to generate a sound wave or ping in order to alter the characteristics of any cavitation voids present in the fluid due to the presence of a leak and preferably, to collapse at least some of the cavitation voids under the increased pressure of the at least one excitation wave. Typically, the emitter will be configured to emit a sound wave or ping in fluids are pressures up to approximately 1000 kPa. The emitter will typically be able to withstand spikes in fluid pressure of up to 3000 kPa.

[0086] The emitter will preferably be able to emit the excitation wave or ping at a variety of frequencies as may be required by different fluids and/or the pressure in the fluid being tested. In a particularly preferred form, the at least one emitter will have sufficient energy to propagate a sound wave over significant distance. The distance will normally be the test distance and the test distance may vary from a number of meters for some uses up to 1000 m or 1500 m for other uses.

[0087] The excitation wave or ping is preferably an ultrasonic wave, a particularly preferred frequency for which is approximately 800 Hz in water for example. The frequency of the excitation wave or ping may vary for different fluids and will typically be optimised for the particular fluid being tested.

[0088] As mentioned above, in use, the introduction of the excitation wave will typically modify or eliminate one or more bands of noise generated by the leak as is illustrated in Figure 5 in particular. Therefore, the system of the present invention will typically analyse the difference in noise detected between when the ping is present and when the excitation wave is not present in order to detect differences between the two situations, comparing the two sets of data to arrive at a result indicative of a leak. Typically, the system of the present invention will do this by signal or data analysis and it is particularly preferred that for rear series analysis is undertaken, preferably fast Fourier transform analysis.

[0089] The system of the present invention may be used to match the leak noise data with a wall vibration data and detect changes in wall vibration data that may be indicative of the presence of a leak due to changes in the wall vibration from the emitter to the leak and between the leak and the detector. As mentioned above, a separate emitter may be provided within the system of the present invention to introduce a wall vibration and/or the soundwave emitter used to introduce the at least one excitation wave into the fluid may also introduce a vibration in the conduit wall.

[0090] The emitter of the preferred embodiment will preferably have a diaphragm which is movable in order to introduce the at least one excitation wave. The diaphragm will typically enable Uni axial transmission of the at least one excitation wave. Preferably, the emitter will create a flattened waveform with minimal side bands for scatter. The emitter will preferably be capable of variable power output as required by the fluid and/or the test distance.

[0091] In keeping with the present invention, the creation of a return wave is far less important than the creation of an optimum excitation wave as the detector/receiver used in the present invention means that the invention does not operate on the principles of reflection of the excitation wave. It is preferred that the emitter will propagate the wave in a single direction only in the conduit.

[0092] Typically, the detector 13 is spaced from the emitter 12 (although they may be provided at the same position, for example is provided in the same unit). In a particularly preferred embodiment shown in eth Figures and in the test rig in Figure 7, the detector 13 is located on one side of the leak 11 and the emitter 12 will be located on the opposite side of the leak 11 from the detector 13.

[0093] The emitter may be of any type. In one particularly preferred form, the emitter will typically create an excitation wave pulse or ping by applying a negative voltage at a solenoid to move the diaphragm, which is typically associated with a magnet or similar in order to seat the diaphragm hard against a preferred ferrite core in the solenoid. The application of a positive voltage will then typically drive the diaphragm forward in order to create the at least one excitation wave pulse or ping. Clearly the opposite voltage configuration could also be used if desired. The invention preferably does not rely on the particular mechanism for creating the excitation wave pulse or ping merely that an excitation wave pulse or ping be introduced and then the system can monitor for altered noise as a result.The emitter 12 may be located relative to the conduit 10 in any location in order to allow the at least one excitation wave to be generated, preferably emitted substantially in line with the length of the conduit 10.

[094] The detector 13 can be provided in any location relative to the emitter 12. As mentioned above, it is preferred that the detector 13 is spaced apart from the emitter 12, typically with the detector 13 on one side of the leak and the emitter 12 on the other side of the leak 11. Of course, the operator will not necessarily know, although they may suspect, the location of the leak and therefore, in usual operation, the emitter 12 is provided relative to one portion of the conduit 10 and the detector 13 will be provided relative to the conduit 10 spaced apart from the emitter 12 in order to define a test length. The operator can then test that length, and subsequent lengths, in order to test the conduit. The operator will typically use an overlapping test length in order to ensure that if a leak is present, it can be detected. The operator will typically move the emitter and detector along the conduit as a result to test different test lengths.

[095] The detector may be of any type. In a particularly preferred embodiment, the detector may be or include a hydrophone.

[096] It is possible that the emitter and detector will be provided as a single unit in order to accomplish both functions with a single unit. It makes the calculation easier if they are in the same unit. It makes it easier for the process to send & receive data between hydrophone and pinger. However, as illustrated that the emitter 12 and detector 13 provided as two separate devices in order to define a test length as mentioned above

[097] In use, the detector 13 will typically be mounted substantially coaxially with the length of the conduit 10.

[098] As mentioned above, one or more additional emitters and one or more additional detectors may be provided in order to introduce a vibration wave into one or more walls of the conduit. A single emitter may introduce both the excitation wave ping into the fluid and create a vibration wave in one or more walls of the conduit. If a single emitter is used for both purposes, it is preferred that one or more detectors are used to detect both the noise in the fluid and the vibration in the conduit.

[099] The processor will typically provide a control and/or analysis function to the present invention. The processor will normally operate software adapted to control the emitter and the parameters of the at least one excitation wave so that the excitation wave is optimised to interfere with the noise. The particular parameters of operation may be user-defined and/or provided as a part of the software operating system to allow the software to control the parameters and/or any optimisation of the parameters may be required.

[0100] A preferred embodiment of the signal processing is illustrated in Figures 12 to 23 (and which was also used to test the efficacy of the operation of the system).

[0101] The processor will preferably receive the data in relation to the noise in the conduit 10 when the ping is off, the noise in the conduit 10 when the ping is on and/or in relation to the excitation wave or ping itself in order to take this data into account in the analysis. The processor will preferably receive information from both the emitter 12 and the detector 13.

[0102] A software application is preferably provided in order to undertake the analysis. This offer application is preferably provided to control the system and the components within the system. A software application may be provided for each function are preferably, a single software application is provided for control and analysis of the system overall.

[0103] As will be relatively clear at this point, the analysis of the information is particularly important in order to not only locate the presence of a leak but also to locate, if possible the position or location of the leak relative to one or more components of the system.

[0104] The data analysis will normally begin with data which is received by the processor, an example of which is illustrated in Figure 12. The data received by the processor will typically include noise data and/or vibration data. The data will typically include noise data and/or vibration data when the excitation wave pulse or ping is on and when the excitation wave pulse or ping is off. Figure 13 shows an example of the data feed when a leak is present and the ping has transitioned from on to off and Figure 14 shows an example of the data feed when a leak is present and the ping has transitioned from off to on.

[0105] The data in relation to the noise which is collected is typically then analysed in comparisons made in order to determine whether a leak is present or not. The data may require some analysis before the comparison can actually be made in order to ensure that the data which is being compared is the relevant data. In this respect, the data will typically undergo Fourier analysis typically being analysed according to a fast Fourier transform in order to create a fast Fourier transform dataset. Once this has been achieved, a baseline or threshold is preferably provided and applied to the fast Fourier transform dataset. The baseline or threshold will typically be chosen by the user end/or the software application and will preferably be adjustable depending upon the system parameters and also the parameters of the fluid. This is illustrated in Figure 12.

[0106] Once the baseline or threshold has been applied to the dataset, frequencies above or below the threshold, depending on the ping transition state will typically be nominated as the distance from the detector to the leak.

[0107] This system will then preferably process the nominated information, typically by averaging all nominated values as shown in Figure 15, to calculate a final value.

[0108] The system will typically apply other methods, such as determining if the standard deviation of the nominated values if above a specified value to determine if no leak is present.

[0109] Once a final value has been detected the location of the leak can be calculated based on the speed of the wave in the particular fluid. For example, the speed of a wave in water is approximately 1500 m/s. The time from the clock or timer and the speed of the wave propagation in the fluid can then be used to calculate a distance to the leak from the detector.

[0110] A particularly preferred example of the algorithm that is followed by the processor of the present invention is as follows:

Power up * Are all components connected to the device - throw error 1 • Is the device connected to water - throw error 2 * FREQINTERVAL - 2kHz (adjustable) • THRESHOLDPINGON-+ (adjustable TBA as part of testing, and less than 1.0) • THRESHOLDPINGOFF-+ (adjustable TBA as part of testing, and less than 1.0) S# of loops - 5 (adjustable) • SAFETYMARGIN - (adjustable TBA as part of testing) • DEVIATIONSAFETYMARGIN - (adjustable TBA as part of testing)

Get baseline data • Average the amplitudes of a few seconds worth of samples in FREQINTERVAL increments between 10kHz and 22kHz (adjustable) • Save result as FREQTIME=o * Set COUNTER -0

Do the following # of loops times Get ping on data (PINGON loop) • Start timer & ping (START_TIMERo) o If Current timer - STARTTIMERo > 170 milliseconds (adjustable) then • stop STARTTIMER & ping • break PINGON loop o Else • Get the amplitudes of FREQINTERVAL frequencies between 10kHz and 22kHz (adjustable) • For each FREQINTERVAL frequency, find the first two (adjustable) consecutive amplitudes are below THRESHOLDPINGON x FREQTIME=o then o DistanceCOUNTER AT FREQINTERVALON= (STARTTIMERTIME=CURRENT_TIME - STARTTIMERo) / 1500 o COUNTER++ 0

Get ping off data (PINGOFF loop) • Start timer (STOPTIMERo) • If Current timer - STOPTIMERo > 170 milliseconds (adjustable) then o Stop STOPTIMER o Breakloop • Else o Get the amplitudes of FREQINTERVAL frequencies between 10kHz and 22kHz (adjustable) o For each FREQINTERVAL frequencies first the first amplitude that is above THRESHOLD PING OFF x FREQTIME=othen

• DistanceCOUNTER AT FREQ_INTERVALOFF = (STOPTIMERTiME=CURRENTTIME STOPTIMERo) / 1500 (for water) • COUNTER++

Process data • If COUNTER > SAFETYMARGIN o Find average of Distance o Find standard deviation of Distance o If standard deviation > DEVIATIONSAFETYMARGIN then • No leak found - Throw error 3 o Else • Display the distance * Else o No leak found - Throw error 3

[0111] As indicated above, the excitation wave is optimised to interfere with the noise. To this end, the emitter 12 has a unique control methodology and unique features are required for the signal conditioning and signal processing as described below.

[0112] The emitter 12 is designed to send a lengthy pressure wave, with long wavelength instead of a frequency, in order to make the induced effects last long enough to be detectable. There is no requirement to use an echo, as instead the system detects the noise from cavitation that is induced in the pipes, fittings and cracks and detects the changes to noises made by cavitation around geometric features such as cracks, t-pieces, etc.

[0113] Known pingers typically are designed with piezo or magnetostrictive metal materials, and have very short strokes of a few microns. These are completely incompatible with generating long wavelengths unless the transmitter is made a ridiculous length. Instead, the emitter 12 has a long 3mm stroke and will pump a sustained pressure wave. In 40mm diameter pipes this pressure wave is approximately 1.5 meters long.

[0114] The pressure wave provides a more sustained change of state at the leak site, than sound waves. This allows the microcontroller to take many samples while the interference occurs, and the interfered state is then more obvious when signals are processed.

[0115] The system may utilize a bobbin as a backstop during an over pressure event. Further, the system utilizes a spring force in the emitter diaphragm that equalizes with the water pressure such that relatively little force is required to displace the diaphragm and pump a signal.

[0116] The system incorporates a purge mechanism that bleeds air from the very face of the diaphragm. This mechanism minimizes trapped air that can shorten the length of the pressure wave generated.

[01171 In use, the system detects the need for a purge by sending a low power pulse to the transmitter and measure the peak to peak values at the hydrophone. A weak or short response indicates the presence of air pockets and then the processor automatically activates the purge valve.

[0118] In testing, noise is easily detected at the start and end of each pressure wave. The pressure wave behaves like a solid mass that bounces inside the pipe. This wave does not reflect off surfaces. The start and end of the pressure wave creates easily detectable sounds when passing features such as joins, fittings, and leaks. The spacing between these sounds indicates the length of the pressure wave. Any gas pockets in front of the diaphragm will shorten the length of the pressure wave and corrupt the timing of the start and end noise patterns.

[0119] The system can use frequencies however typically instead sends a single pulse half cycle. This technique eliminates a lot of noise bouncing around inside the pipe which complicates the signal processing,

[0120] The system also induces cavitation. The effect of the pressure wave causes cavitation at geometries such as edges, bends, tee fittings and leak fractures. The pressure wave front and rear cause the formation of distinct cavitation which we can detect and range from.

[0121] The current embodiment describes a method of analysing the results to pin point the location of a leak. The system can also ustilise Al methodologies. For example, one application would be to feed in a long stream of high resolution training data gained from either a hydrophone in the water or a vibration sensor on the pipe wall with leaks at known locations. With enough training data, the system would learn, over time, to interpolate and extrapolate leak locations and leak types. This data collection can be used with a sustained pressure wave and segmented as follows. • The data is segmented into say 75 readings (collected at high frequency). • The Al analysis is carried out on each segment of data. • Segments of data known to contain leaks are flagged. • Segments with different types of leaks are flagged. • The Al system sequentially compares each segment to the library of leaks. • The leaks segments identified with a match then go through another program to correlate the time of collection with a location from the sensor.

[0122] Any segments of data indicating possible leaks can be further analyzed by capturing a shorter duration of higher resolution data around the time of return corresponding to particular anomalies. This higher resolution data can then be collected at optimal gain and analyzed for particular frequencies or via Al for a more definitive leak diagnosis. Noting that there is a limit on the volume of data that can be collected and analysed, this technique works within memory and data transfer limits.

[0123] A method of detecting a leak using the system can be performed by sequentially sweeping the pipe. While able to store enough data to sweep a large distance of say 1000 meters, the system can also sweep a high resolution of each 10-meter segment using the above methodology. The sequential sweeping in the context of leak detection is unique because there is little successful work in this field, and none of which is in conjunction with pressure waves.

[0124] One embodiment provides a method for synchronizing two or more controllers in instruments remotely. A pair or a network of instruments can be utilized as an ultrasonic flow meter. This method of measurement is known in the art, but requires two sets of transmitter/receivers connected to a single microprocessor that measures the difference in time delay after sending a sound in each direction along a short section of pipe. A unique method can be provided for remotely synchronizing two separate microprocessors separated by much greater distance so that the established state of art may be used for measuring fluid velocity. The system can detect pressure by measuring the DC offset in the diaphragm. When utilized with the above velocity measurement and known or deduced pipe elevations, the system can interactively compute the pressure head, velocity head and height of a network and interpolate these results between the nodes where sensors are located. The head expressions are evaluated using the known Bernoulli equation. However, no system exists that displays this data in real time on a network, and the foregoing new instrument is configured to make this feasible.

[0125] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0126] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[01271 In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims

1. A fluid leak detection system to detect a fluid leak at a fluid/solid boundary, the system including: at least one wave emitter to introduce at least one excitation wave into at least the fluid, at least one detector to detect at least noise in the fluid, and at least one processor to analyse the difference in noise detected between when an excitation wave is introduced in the fluid and when the excitation wave is not present in the fluid in order to detect a leak, and when a leak is detected, determine the time delay between emitting the excitation wave until the noise is modified to calculate the location of the leak in distance terms relative to the detector.

2. A fluid leak detection system as claimed in claim 1 wherein at least one detector and at least one emitter are located at the same position.

3. A method for detecting a fluid leak, the method involving: analysing the difference in noise detected between when an excitation wave is introduced in the fluid and when the excitation wave is not present in the fluid in order to detect a leak, and when a leak is detected, determining the time delay between emitting the excitation wave until the noise is modified to calculate the location of the leak in distance terms relative to a detector.

4. A method for detecting a fluid leak as claimed in claim 3 wherein the excitation wave is optimised to interfere with the noise.

5. A method for detecting a fluid leak as claimed in claim 3 or claim 4 wherein there is no need to detect echo of the excitation wave.

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