WO2017011871A1 - Apparatus and method for identifying defects in conduits - Google Patents

Abstract

H:\kmh\Interwoven\NRPortbl\DCC\KMH\10514824_1.docx-19/07/2016 ABSTRACT An apparatus (1) for identifying defects in a liquid-carrying conduit (6). The apparatus (1) includes a probe (2) adapted to dissipate at least one electrical signal therefrom, a flexible cable (3) attached to said probe (2), adapted to position/move said probe within said conduit (6), and, adapted to conduct electrical signals to and from said probe (2); probe position monitoring means, adapted to provide position data indicative of a position of said probe (2) within said conduit (6); an electrode (4), adapted to be positioned external to said conduit (6), to receive any electrical signal(s) dissipated from said probe (2), and, a processor (10), adapted to process said electrical signal(s) received by said probe (2) in connection with said position data of said probe (2) to thereby provide an output signal indicative of the position of any defect in said conduit (6).

Description

APPARATUS AND METHOD FOR IDENTIFYING DEFECTS

IN CONDUITS

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an apparatus and method for identifying defects in a conduit, and in particular, to an apparatus and method for identifying leaks or cracks in a non-conductive, liquid-carrying conduit, such as a sewer pipe.

[0002] The present invention also relates to a unique probe which is used in conjunction with processing circuitry/algorithms to identify various parameters, such as the position and nature of any conduit defect, such that appropriate remedial action may be instigated.

DESCRIPTION OF THE PRIOR ART

[0003] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

[0004] The identification of defects in conduits such as sewer pipes can be difficult, time consuming, and costly. This is primarily due to the usual underground location of such conduits which makes them difficult to access. Sometimes leaks in pipes may exist for a prolonged period before detection of conduit defects is identified. This can potentially create quite hazardous situations

[0005] In recent times, various apparatus and method have been developed which seek to address these issues.

[0006] For example, camera based inspection systems have been developed to provide a visual display of the condition of a conduit. This may be appropriate in some circumstances, however, if the conduit is carrying effluent or other cloudy products, then visual identification may of course be difficult or impossible, and it is a subjective process that relies on the camera operator's interpretation of the images.

[0007] A description of various prior art systems, including the FELL system is described in a paper entitled "A New Development in Locating Leaks in Sanitary Sewers" by Sanjeev Gokhale and Jeffrey A. Graham, the disclosures of which are incorporated entirely herein by this reference thereto.

[0008] The focused electrode leak location (FELL) system measures electrical current flow between a probe that travels in a pipe and a surface electrode. Any pipe defect which allows a liquid to flow into or out of the pipe will cause a spike in the electrical signal, which thereby enables identification of the location of the defect. Furthermore, the paper describes that the intensity of the measured current can be correlated to the magnitude of the defect. This system operates by providing a probe which is positioned within and moved along the pipe and which dissipates an electrical field. A surface electrode is also placed into the ground at the surface. The apparatus works on the basis that the pipe is constructed of non-conducting material and contains liquid such as sewerage or water. In an unbroken pipe, little or no electric current flow occurs between the probe and the surface electrode. However, if there is a defect in the pipe which allows the flow of fluid either into or out of the pipe, this provides an electrical pathway through the wall of the otherwise non-conducting pipe and through the ground to the surface electrode. Signals can be analysed such that variation in the electric current is monitored. When the electrode comes close to the defect in the pipe, the electric current between the probe and the surface electrode increases and is at a maximum when the probe is aligned with the defect.

[0009] Various other attempts have been made to improve the identification of defects, for example, in US Patent No. 6301954, the disclosures of which are incorporated herein by this reference thereto. US 6301954 describes a system which includes a probe which is positioned within a conduit, and which has a plurality of probe sections. All sections have voltage applied thereto to dissipate an electrical signal, whilst a central section also measures the leakage current. The central section is divided into a plurality of radially extending segments such that axial and radial location of a defect may be measured. Whilst this device seeks to provide a more precise location of the defect in a sewer pipe it is complex in design, requires sophisticated processing circuitry, and as such is not necessarily commercially viable.

SUMMARY OF THE INVENTION

[0010] The present invention seeks to overcome the disadvantages of the prior art by providing an alternative apparatus and method for accurately and quickly identifying defects in a liquid-carrying conduit.

[0011] The present invention also seeks to overcome the disadvantages of the prior art by providing a unique probe design which differs significantly from the prior art.

[0012] In one broad form, the present invention provides an apparatus for identifying defects in a liquid-carrying conduit, said apparatus including: a probe adapted to dissipate at least one electrical signal therefrom, a flexible cable attached to said probe, adapted to position/move said probe within said conduit, and, adapted to conduct electrical signals to and from said probe; probe position monitoring means, adapted to provide position data indicative of a position of said probe within said conduit; an electrode, adapted to be positioned external to said conduit, to receive any electrical signal(s) dissipated from said probe, and, a processor, adapted to process said electrical signal(s) received by said probe in connection with said position data of said probe to thereby provide an output signal indicative of the position of any defect in said conduit.

[0013] Preferably, said probe includes a first portion, adapted to dissipate a first electrical signal therefrom; and a second portion, electrically insulated from said first portion, adapted to dissipate a second electrical signal therefrom.

[0014] Also preferably, said probe position monitoring means is associated with a reel onto which said cable is spooled.

[0015] Also preferably, said reel includes a sensor, counter, or like device to detect the extent of cable spooled from said reel. [0016] Preferably, said processor processes derived quantities, such as differentials between said first and second electrical signals dissipated from said first and second portions of said probe to locate the position of any defect in said conduit.

[0017] Also preferably, said processor uses shape matching algorithms to estimate size and/or other parameters of any identified defects.

[0018] Preferable, the first portion of said probe is adapted to receive a fraction of the dissipated second electrical signal, and the processor further processes said fraction of the dissipated second electrical signal for determining electrical properties of fluid surrounding the probe.

[0019] In a further broad form, the present invention provides a method of identifying defects in a liquid-carrying conduit, said method including the steps of: positioning/moving a probe in said conduit via a flexible cable attached to said probe, said probe being adapted to dissipate at least one electrical signal(s) therefrom; monitoring position/movement of said probe to produce position data; supplying an electrical signal to said probe via said cable; receiving said electrical signal(s) dissipated from said probe via an electrode positioned external of said conduit; and processing any received signal(s) in correlation with said position data to provide an output signal indicative of the position of any defect in said conduit.

[0020] Preferably, said probe includes a first portion, adapted to dissipate a first electrical signal therefrom; and, a second portion, electrically insulated from said first portion, adapted to dissipate a second electrical signal therefrom.

[0021] Preferably, said processing step includes processing derived quantities, such as differentials between said first and second electrical signals dissipated from said first and second portions of said probe, respectively, to locate the positon of any defect in said conduit.

[0022] Also preferably, said processing step includes using shape matching algorithms to estimate size and/or other parameters of any defects identified. [0023] Preferably, the first portion of said probe is adapted to receive a fraction of the dissipated second electrical signal, and said processing step includes processing said fraction of the dissipated second electrical signal for determining electrical properties of fluid surrounding the probe.

[0024] In yet a further broad form, the present invention provides a probe for identifying defects in a liquid-carrying conduit, said probe adapted to dissipate at least one electrical signal therefrom; wherein in use, said probe is moved in said electrical conduit via a flexible cable attached thereto, whilst the dissipation of said electrical signals from said probe sections is monitored and processed with probe position data to thereby provide an output signal indicative of the position of any defect in said conduit.

[0025] Preferably, said probe includes a first portion, adapted to dissipate a first electrical signal therefrom; and, a second portion, electrically insulated from said first portion, adapted to dissipate a second electrical signal therefrom.

[0026] Preferably, each of said first and second portions is substantially coaxially aligned.

[0027] Also preferably, each of said first and second portions is substantially cylindrical in shape.

[0028] Preferably, said first and second signals dissipated from said first and second portions, respectively are AC voltages with magnitudes typically considered as "Extra Low Voltage", for example about 10V, and frequencies in the range where the physical effects are dominantly electromagnetic conduction rather than radiation, for example about 10Hz to 10kHz, and preferably about 500Hz.

[0029] Preferably, the first portion of said probe is adapted to receive a fraction of the dissipated second electrical signal.

[0030] Also preferably, the second portion of said probe is adapted to receive a fraction of the dissipated first electrical signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will become more fully understood from the following detailed description of preferred but non-limiting embodiments thereof, described in connection with the accompanying drawings, wherein:

[0032] Fig. 1 illustrates a schematic view of the apparatus of the present invention;

[0033] Fig. 2 illustrates the fundamental operation of the apparatus shown in Fig. 1;

[0034] Fig. 3 illustrates side and end views of an exemplary embodiment of the probe;

[0035] Fig. 4 illustrates how the electrical connection of the probe segments may typically be achieved;

[0036] Fig. 5 shows a graph illustrating leakage conductance from a single probe section as a function of distance;

[0037] Fig. 6 shows how a shape matching algorithm may be used to match the measured parameters from the single section probe;

[0038] Fig. 7 shows a graph illustrating leakage conductance from a two section probe;

[0039] Fig. 8 shows a processing approach for a two section probe;

[0040] Fig. 9 illustrates graphically how questionable data may be identified from the leakage current measurements; and

[0041] Fig. 10 illustrates a schematic block diagram illustrating the main components and processing of the apparatus/method of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0042] Throughout the drawings, like numerals will be used to identify similar features, except where expressly otherwise indicated. [0043] In Fig. 1 is shown the apparatus 1 for identifying defects in a liquid-carrying conduit. The apparatus 1 includes a probe 2, a flexible cable 3 which is attached to the probe, and a surface electrode 4. The probe 2, the details of which will be described hereinafter is inserted into a liquid-carrying conduit 6.

[0044] The probe may be positioned by the known method of attaching a flexible cable 3 to the probe 2 and then spooling it out into the conduit 6 via a spooling apparatus 7. This may, for example, operate by a cable reel being used to spool out the cable 3, the cable reel including a cable distance sensor such that the length of cable and consequently the position of the probe within the conduit is known by providing appropriate position data corresponding thereto.

[0045] The apparatus also provides a power supply 8 which is adapted to supply electrical signals to the probe 2, along with electrical meters 5 to measure current flow resulting from said signals.

[0046] The probe 2, as illustrated in Fig. 1 is divided into a first portion and a second portion which is electrically insulated from the first portion. As can be seen in the drawings, the probe portions are substantially coaxially aligned and may typically be substantially cylindrical in shape.

[0047] The first portion 21 of the probe 2 is adapted to dissipate a first electrical signal therefrom whilst a second portion 22 of the probe 2 is adapted to dissipate a second electrical signal therefrom which may be different/distinguishable from the first electrical signal. For example, voltage signals of different frequencies may be dissipated from the first and second portions of the probe 2, or alternatively pulses may be intermittently dissipated from first and second portions of probe 2 (e.g. first portion 21 and second portion 22 dissipating one or more pulses at non-overlapping time intervals), or alternatively the first and seconds portions may be driven with identical signals. In a preferred example embodiment, the properties of the electrical signal dissipated from first portion 21 are unrelated to, or independent from, the properties of the electrical signal dissipated from second portion 22 of probe 2. When the probe travels near a defect 9 in the conduit 6, the first and second electrical signals result in current flowing from the first and second portions 21 and 22 of the probe 2 to an electrode 4. The electrode 4 is adapted to be positioned external to the conduit, for example, in the ground surface.

[0048] A processor 10 is adapted to detect and process any electrical signals, received by the electrode 4 and transmitted from the first and second sections 21 and 22 of the probe 2 as will be described hereinafter. These signals, in correlation with position data of the probe 2 (or alternatively, of the first portion 21 and second portion 22 of probe 2) provided by the known position of the flexible cable therefore provides an output signal indicative of the position of the defect 9 in the conduit 6.

[0049] Referring now to Fig. 2, the basic operation of the apparatus of the present invention is described.

[0050] Fig. 2(a) illustrates a pipe 6 which does not have a defect therein. No current flow will occur from within the conduit to the electrode 4.

[0051] As the probe 2 is advanced towards the defect 10 as shown in Fig. 2(b), the electrode 4 will firstly detect a larger current through the leading portion 21 of the probe 2, whilst very little current will be detected through the trailing portion 22 of the probe 2.

[0052] As the probe 2 is advanced further and is aligned with the defect 10, as shown in Fig. 2(c), approximately equal currents will be detected through both the leading and trailing portions of the probe 2.

[0053] As the probe is advanced still further and has passed the position of the defect 10 as shown in Fig. 2(d), relatively smaller current will be detected through the leading portion 21 of the probe 2 whilst a relatively larger current will be detected through the trailing portion 22 of the probe 2.

[0054] As will be appreciated by persons skilled in the art this unique two- sectioned probe therefore provides an accurate method of indicating the position of any defect in the conduit.

[0055] Additional sections may be incorporated in the probe, for further accuracy, as will be appreciated by persons skilled in the art. [0056] Figs. 3 and 4 illustrate some of the features of a preferred but non limiting exemplary embodiment of a two section probe in accordance with the present invention, Fig. 3 illustrating side and end views of a probe, whilst Fig. 4 shows how the electrical wiring connects from the cable to each of the sections of the probe.

[0057] The probe forms a critical part of the electric test circuit, and as it is moved through the pipe under test the current flow through the probe varies in relation to the integrity of the pipe walls. Since the pipe walls are constructed from material which is nominally an electrical insulator, very little current will flow unless there is a defect in the pipe wall, so the electrical insulation properties are compromised.

[0058] This essential function may be performed by a probe which acts as a simple 'point source' (i.e. only one portion), however the drawback to this approach is that localising defects can be difficult because the water in the pipe is conductive, and the probe may 'see' the effects of a defect some distance before and after the actual location of the defect. The outcome being that instead of a single sharp 'spike' in the measured current at the location of the defect, a gradual rise and fall are observed, although the peak is still at the location of the defect.

[0059] This effect is due to current flowing along the pipe. The ideal situation is that the current measured to indicate pipe wall integrity is restricted to only flow perpendicular to the probe, so only defects in the adjacent walls will be 'seen'. This is the approach taken by previous systems, where additional 'sections' (or portions) at either end of the probe are used to 'restrict' the electric field around a smaller 'middle section', and only the current through this middle section is measured.

[0060] The system of the present invention takes a different and unique approach to improve the ability to localise defects, instead of trying to improve the 'peakiness' of the measured current directly, more advanced signal processing is used to identify and localise defects using the 'less sharp' results obtained without the 'electric field restriction' of the previous systems. Therefore, unlike previous systems, the system of the present invention does not rely on generating a highly localized electric field. Instead, any type of electric field, including that generated from a simple "point source" electrode, may be exploited to generate data which, after processing, indicates the location of a pipe defect with high accuracy.

[0061] Importantly, previous systems attempted to suppress electric field lines which were not essentially orthogonal to a longitudinal axis of the probe, such as electric field lines through the conductive fluid in the pipe. This however, is not the case of the present system, where any electric field line, along any direction, which causes current to flow between probe 2 (or first portion 21, or second portion 22) and surface electrode 4, may be used to generate data which, after processing, indicates the location of a pipe defect with high accuracy.

[0062] As will become apparent to persons skilled in the art, there are multiple methods that could be used to detect and localise the defects (some of them have been previously listed), and many of them will work with a variety of probe designs (including a 'single portion' / 'point source'). However, this exemplary embodiment uses a probe with two sections, as some of the algorithms use differences between current through sections to better localise defects.

[0063] Referring to Figs. 3 and 4, this two section probe design consists of two equally sized cylindrical 'electrode portions' 21 and 22, with an insulating barrier between them 23. 'End caps' 24 are used to seal the interior of the probe and prevent water ingress, and a flexible cable 3 is attached to provide both the measurement signals to the electrodes, and a mechanical coupling to move the probe through the pipe under test. Contained within the flexible cable 3 there are a number of electrical conductors, or 'cores', 26 and 27 that are connected to the electrodes 21 and 22 on the interior of the probe. Alternatively, a single electrical conductor may be connected to both first and second portions 21, 22 or probe 2 and filters (e.g. electronic analog or digital filters) may be used to discriminate the electrical signal dissipated from first portion 21 from the electrical signal dissipated from second portion 22.

[0064] The specific details of the probe design, such as diameter and length are dependant on the target pipe size. Different sized probes are required for different sized pipes. The probe may be structured such that its dissipated electric field is approximately omnidirectional (e.g. as in a "point source"), or alternatively such that the dissipated electric field is biased towards one or more directions.

[0065] While this two portion design is used as an exemplary embodiment, the basic approach may be extended to probes with only one electrode portion (although not all of the signal processing algorithms would be applicable), and also to probes with more than two electrode portions. The key difference between this approach and previous systems is that the current flowing through each portion must be measured, and is then used to provide additional input information to the later signal processing stages that identify and localise defects.

[0066] An example of the measured results from a single probe section is shown in Fig. 5. Note that this figure shows the results presented as a plot of leakage conductance versus distance, but other presentations are also possible, for instance leakage current versus distance, or impedance versus distance.

[0067] While an experienced operator may be able to directly interpret these results to locate defects, additional processing may be performed on the results to identify and categorise defects in the conduit without relying on the assessment of an operator.

[0068] An example of the processing that may be performed is peak detection, where the location of peaks in the results corresponds to the location of defects in the conduit, and the magnitude of peaks in the results is related to the size of the defects.

[0069] A further example is using shape matching algorithms to match a template response to patterns in the measured results, as illustrated in Fig. 6. The template response may be determined through analytical modelling, and parameterised corresponding to aspects of defects in the conduit including but not limited to diameter, and length.

[0070] Instances of the template response in the results may be matched by varying the parameters, and the values corresponding to the 'best fit' used to identify and categorise defects in the conduit. [0071] Using multiple sections in the probe provides additional information that enables other processing for identifying defects. An example of the measured results when using a probe with two sections is shown in Fig. 7.

[0072] An example of a processing approach that may be applied to a system using a probe with two sections is using the point at which the trailing section of the probe begins to supply more current than the leading section. This point can be found calculating the difference between the currents flowing through the leading and trailing electrode portions. This approach is shown in Fig. 8. This approach may further involve calculating higher derivatives (e.g. first and second derivatives) of the measured signals with respect to distance, allowing one to obtain the location of the maxima (and minima) of the measured signals. This data could then be utilized to pinpoint defect locations. For instance, in the example plot illustrated in Fig. 8, a location of a defect would be characterized by the point at which the difference between the signals measured from the leading and trailing probe sections equals zero, occurring at a 'greater' distance than a maximum of the leading portion signal, but at a 'lower' distance than a maximum of the trailing portion signal.

[0073] In addition to identifying defects in the conduit, further processing of the measured results may be used to identify questionable data. An example of this is shown in Fig. 9, where the sharp 'step changes' indicate problematic results. Such step changes are not expected in typical results and may indicate problems such as slippage of the distance measurement hardware, or other errors in test configuration like air pockets. This type of processing is more difficult when only a single electrode portion is used, whereas measurements from additional electrode portions provide a means of 'sanity checking' the measurements from other portions.

[0074] Other types of processing include 'quality indicator' methods for determining the integrity of the probe and the quality of the probe measurements. One example 'quality indicator' method relies on measuring or monitoring electrical properties of material or fluid around the probe, such electrical properties including, but not being limited to, impedance, resistivity, or conductivity of the fluid, or combinations thereof. This enables the identification of problems which may lead to invalid measurements. An example of such problems includes the probe passing through an air pocket, which can be detected because the impedance between the probe portions typically increases when the probe is in the air. Furthermore, since fluid resistivity may fluctuate across different tests, the proposed 'quality indicator' method allows for adjustment of the results from different tests to a common scale. This is an improvement over the previous systems which simply report the measured current, and are therefore unable to directly compare measurement results from different tests due to variations of the conductivity of the fluid around the probe.

[0075] In one example, measuring or monitoring the resistivity of the fluid surrounding the probe involves passing a current between the portions of the probe within the pipe rather than from the probe to the earth electrode outside the pipe. The signal dissipated from one portion is received at another probe portion (e.g. from the trailing probe section to the leading probe section, and vice versa). Since the probe portions are insulated from each other, the signal received by one portion from another portion must travel through the fluid surrounding the probe (i.e. the signal path is from one probe portion, through the fluid, to the other probe portion). Each probe portion may be equipped with circuitry for receiving the dissipated signal from the other probe portion. The received signal may then propagate, through the cable attached to the probe, to the processor, where it is detected and processed to determine electrical properties of the fluid surrounding the probe, such as, but not limited to, impedance, resistivity, or conductivity of the fluid, or combinations thereof. In one example, the determined electrical property is the 'loop impedance' between the first and second probe portions, giving an indication of the resistivity of the fluid around said probe portions. In some example embodiments, the cable attached to the probe is provided with two or more conductors for conducting electrical signals to and from the probe (e.g. electrical signals being supplied to the probe portions and electrical signals being received by the probe portions for measuring electrical properties of fluid surrounding the probe).

[0076] The above-described 'quality indicator' method may be run selectively following a user's input, or it may run at predetermined time intervals, or it may run continuously during operation of the present invention. For example, a fraction of the signal dissipated from one probe portion may be continuously received by the other probe portion, while the remainder of the dissipated signal is received by the surface electrode for detecting pipe defects. In various embodiments, the fraction of the signal dissipated from one probe portion and received by the other probe portion is greater than 0 and less than, or equal, to 1. While the 'quality indicator' method has been described in an exemplary embodiment in relation to a two-portion probe, the basic approach may be extended to probes with more than two electrode portions, with electrical properties of fluid surrounding the probe being measured between any combination of two adjacent or non- adjacent probe portions.

[0077] Fig. 10 illustrates an overall schematic diagram showing the process and main components of the apparatus/method of the present invention.

[0078] It will be understood that the process of the present invention includes the following main steps:

1. Generation of test signal

2. Collect physical measurements (raw results e.g. A/D converter count values):

a. Voltage driving each probe section

b. Current through each probe section

c. Rotary Encoder / Cable Counter revolutions

3. Convert Raw Results into meaningful format/units

a. A/D converter count values -> electrical quantities (e.g. ' 1057' ->

2.3V)

b. Revolution counts -> total distance

4. Calculating derived quantities

a. Voltage and current values -> Leakage Impedance/Conductance

5. 'Feature Identification & Classification' processing

a. Defect Identification

b. "Pipe Construction" Identification (e.g. joints & tee-offs) c. "Bad data" Identification (& compensation/correction)

6. Presentation of processed results and Identified Features

more detailed description and alternatives of these main steps will now be

1. Signal Generation

[0080] The system preferably uses AC voltages as the test signal. The device may for example use a "Full-bridge D-class amplifier" to generate a sine wave of approximately 500Hz, and amplitude of up to approximately 10V peak-to-peak, but both of these figures are 'nominal values' that may be changed without significantly altering the functioning of the system.

[0081] This is implemented by the block labelled "Signal Generation" in Figure 10. 2. Physical Measurement Collection

[0082] This step incorporates functionality from most of the blocks in the "Measurement Circuitry/Hardware" and "Physical Measurement Interfaces" section of Figure 10.

[0083] Circuitry is used to convert physical quantities into digital values for use in the later stages. The majority of this process (e.g. circuit designs, A/D converter operation, etc.) would be well understood by persons skilled in the art.

[0084] The system of the present invention uses a probe with a different arrangement of electrode portions. In the present invention two equal sized portions are used, but it is also possible to use a probe with three or more portions. The key difference is that the additional portions are only used to provide additional input information for further signal processing. This of course requires the current flowing through every portion to be measured.

[0085] In addition to the measurements of electrical parameters, the system also determines the location of the probe in the pipe by measuring how much cable has been deployed from the reel. This uses well known techniques such as using rotary encoders to detect rotation of the reel, or a roller as the cable is deployed.

[0086] The system may alternatively also use an integrated GPS receiver to automatically add location information to the test results.

3. Conversion to Meaningful Units

[0087] This step is required to turn the raw measurements (e.g. the output of the A/D converters) into meaningful values. Largely this involves applying the correct scaling factors (which are dependent on the design of the system), although other 'calibration values' may be applied to correct for non-ideal effects. It is implemented in the "Measurement Conversion & Collection" block in Fig. 10.

4. Calculating Derived Quantities

[0088] Some later processing stages might operate on values that are derived from the measured quantities, rather than the measurements themselves (e.g. using impedance instead of current). The derivation is governed by the physical relationships (e.g. impedance = voltage divided by current) of the quantities desired.

[0089] Preferably the derived quantities are impedance (optionally including phase angle), and, conductance (being the reciprocal of impedance), however, other quantities may also be used.

[0090] This is also implemented in the "Measurement Conversion & Collection" block in Fig. 10.

5. Feature Identification & Classification

[0091] The present invention is capable of automatically identify various 'features' in the captured data, where a 'feature' is some aspect of the pipe or test that the user is interested in. The 'features' include, but are not limited to:

• Pipe defects (e.g. cracks, holes, leaks, etc.) • Regular joints between sections of a pipe

• Tee-offs / joints to other pipes

• Possible errors in the test procedure (i.e. 'bad data')

[0092] The primary goal is to identify the locations of these 'features', but the 'features' may also be further classified, or additional information determined, such as whether a defect is a crack or a hole, and how big it is.

[0093] There are a number of possible approaches, and some of these approaches may be applicable to the detection of multiple feature types. The detection methods include:

• Using derived quantities, such as current differentials between the front and back probe sections to locate the 'centre' of a defect

• Using 'shape matching' methods to locate defects and estimate parameters such as size by using modelling results as a 'template shape' and finding instances of that shape in the results

• Locating pipe joints by identifying (regularly) repeating patterns in the results, and potentially estimating the length of each pipe section

• Using results that do not match expectations (such as step changes in results) to identify possible test errors

• Measuring electrical properties of the fluid surrounding the probe to check the probe integrity, to identify problems leading to invalid measurements, and to provide normalizing data for directly comparing measurements obtained through different tests. Such electrical properties include, but are not limited to, impedance, resistivity, or conductivity of the fluid, or combinations thereof.

[0094] Other methods for identifying features are also possible, as will be appreciated by persons skilled in the art. [0095] The approach of the present invention is that the signal processing is either done by the unit itself, either after a test is completed or in real-time during the execution of a test, or the test results will be loaded onto a personal computer with software to perform the processing. In either case the processing is not required to be performed on a 'remote device' that has the capability to transmit the results back to the instrument for display. If the processing is performed on a separate PC, the results will be displayed on that PC. To support this approach there is a facility provided on the device to store and retrieve results, which may also be used to transfer results to a separate PC. This stage is implemented with the "Feature Detection & Classification" and "Storage" blocks in Figure 10.

6. Results Presentation

[0096] In the present invention, the output information may be provided by plotting 'derived quantities' (e.g. impedance or conductance) rather than the measured current itself. Another approach is to only show the 'features' identified by the previous step, this presentation may be varied according to the 'classification' of those features. Alternatively, some combination of these can be used, with the identified features being overlayed onto a plot of either the measured results, or derived quantities. This allows expert operators to verify that the automated detection algorithms have identified all the 'features' in the results. This is implemented in the "Results Presentation" block in Figure 10.

[0097] It will be appreciated by persons skilled in the art that numerous variations and modifications may be envisaged to the invention broadly hereinbefore described. All such variations and modifications should be considered to fall within the spirit and scope of the invention.

Claims

CLAIMS:

1. An apparatus for identifying defects in a liquid-carrying conduit, said apparatus including:

a probe adapted to dissipate at least one electrical signal therefrom,

a flexible cable attached to said probe, adapted to position/move said probe within said conduit, and, adapted to conduct electrical signals to and from said probe;

probe position monitoring means, adapted to provide position data indicative of a position of said probe within said conduit;

an electrode, adapted to be positioned external to said conduit, to receive any electrical signal(s) dissipated from said probe, and,

a processor, adapted to process said electrical signal(s) received by said probe in connection with said position data of said probe to thereby provide an output signal indicative of the position of any defect in said conduit.

2. An apparatus as claimed in claim 1, wherein said probe includes:

a first portion, adapted to dissipate a first electrical signal therefrom; and, a second portion, electrically insulated from said first portion, adapted to dissipate a second electrical signal therefrom.

3. An apparatus as claimed in claims lor 2, wherein said probe position monitoring means is associated with a reel onto which said cable is spooled.

4. An apparatus as claimed in claim 3, wherein said reel includes a sensor, counter, or like device to detect the extent of cable spooled from said reel.

5. An apparatus as claimed in any one of claims 2 to 4, wherein said processor processes derived quantities, such as differentials between said first and second electrical signals dissipated from said first and second portions of said probe to locate the position of any defect in said conduit.

6. An apparatus as claimed in any one of claims 1 to 5, wherein said processor uses shape matching algorithms to estimate size and/or other parameters of any identified defects.

7. An apparatus as claimed in claim 2, wherein the first portion of said probe is adapted to receive a fraction of the dissipated second electrical signal, and wherein the processor further processes said fraction of the dissipated second electrical signal for determining electrical properties of fluid surrounding the probe.

8. A method of identifying defects in a liquid-carrying conduit, said method including the steps of:

positioning/moving a probe in said conduit via a flexible cable attached to said probe, said probe being adapted to dissipate at least one electrical signal(s) therefrom; monitoring position/movement of said probe to produce position data;

supplying an electrical signal to said probe via said cable;

receiving said electrical signal(s) dissipated from said probe via an electrode positioned external of said conduit; and

processing any received signal(s) in correlation with said position data to provide an output signal indicative of the position of any defect in said conduit.

9. A method of identifying defects in a conduit as claimed in claim 8, wherein said probe includes:

a first portion, adapted to dissipate a first electrical signal therefrom; and, a second portion, electrically insulated from said first portion, adapted to dissipate a second electrical signal therefrom.

10. A method of identifying defects in a conduit as claimed in claim 9, wherein said processing step includes processing derived quantities, such as differentials between said first and second electrical signals dissipated from said first and second portions of said probe, respectively, to locate the positon of any defect in said conduit.

11. A method of identifying defects in a conduit as claimed in any one of claims 8 to 10, wherein said processing step includes using shape matching algorithms to estimate size and/or other parameters of any defects identified.

12. A method of identifying defects in a conduit as claimed in claim 9, wherein the first portion of said probe is adapted to receive a fraction of the dissipated second electrical signal, and wherein said processing step includes processing said fraction of the dissipated second electrical signal for determining electrical properties of fluid surrounding the probe.

13. A probe for identifying defects in a liquid-carrying conduit, said probe adapted to dissipate at least one electrical signal therefrom;

wherein in use, said probe is moved in said electrical conduit via a flexible cable attached thereto, whilst the dissipation of said electrical signals from said probe sections is monitored and processed with probe position data to thereby provide an output signal indicative of the position of any defect in said conduit.

14. A probe as claimed in claim 13, including:

a first portion, adapted to dissipate a first electrical signal therefrom; and, a second portion, electrically insulated from said first portion, adapted to dissipate a second electrical signal therefrom.

15. A probe as claimed in claim 14, wherein each of said first and second portions is substantially coaxially aligned.

16. A probe as claimed in claim 14 or 15, wherein each of said first and second portions is substantially cylindrical in shape.

17. A probe as claimed in any one of claims 14 to 16, wherein said first and second signals dissipated from said first and second portions, respectively are AC voltages with magnitudes considered as "extra low voltages", for example about 10V, and frequencies in the range where the physical effects are dominantly electromagnetic construction rather than radiation, for example, about 10Hz to 10kHz, and preferably about 500Hz.

18. A probe as claimed in any one of claims 14 to 17, wherein the first portion of said probe is adapted to receive a fraction of the dissipated second electrical signal.

19. A probe as claimed in any one of claims 14 to 18, wherein the second portion of said probe is adapted to receive a fraction of the dissipated first electrical signal.