| JP08110329 | APPARATUS AND METHOD FOR INSPECTING PINHOLE |
| JP61213647 | DETECTOR FOR WATER LEAKAGE |
| JP2006218372 | MEMBRANE SEPARATION APPARATUS |
WRIGHT, Matthew Alexander Philip (9 Russell Close, Bracknell, Berkshire RG12 7FE, GB)
HARRINGTON, Mark Anthony (34 Saint Michael's Road, Sandhurst, Berkshire GU47 8HE, GB)
SCOTT, Peter Leslie (Federated House, London RoadDorking, Surrey RH4 1SZ, GB)
TRL LIMITED (Crowthorne House, Nine Mile RideWokingham, Berkshire RG40 3GA, GB)
DEPARTMENT FOR TRANSPORT (Great Minster House, 76 Marsham Street, London SW1P 4DR, GB)
IAQUINTA, Jean (5 Allfrey Grove, Spencers WoodReading, Berkshire RG7 1FH, GB)
WRIGHT, Matthew Alexander Philip (9 Russell Close, Bracknell, Berkshire RG12 7FE, GB)
HARRINGTON, Mark Anthony (34 Saint Michael's Road, Sandhurst, Berkshire GU47 8HE, GB)
SCOTT, Peter Leslie (Federated House, London RoadDorking, Surrey RH4 1SZ, GB)
| CLAIMS 1 . A method for detecting defects and/or blockages in conduits comprising: (a) identifying a section of conduit for testing, (b) emitting an acoustic wave within the test section of conduit at one end thereof, and (c) measuring reflected/transmitted acoustic waves within the test section of the conduit wherein the method further comprises locating the emitter at an input end of the test section of conduit in an enclosure body between step (a) and step (b) and orienting the emitter so as to direct the acoustic wave towards a finish end of the test section of conduit, wherein the acoustic wave is a deterministic signal. 2. The method of claim 1 , wherein the stimulus is a long duration signal (compared to the duration of a pulse), such as a maximum length sequence (which is a type of pseudo-random noise) or an exponential swept sine (where the frequency of the sine wave changes exponentially). 3. The method of any one of claims 1 or 2, wherein the deterministic signal is subjected to mathematical post processing to recover an impulse. 4. The method of any one of claims 1 to 3, wherein the input end of the test section of conduit is sealed around or behind the emitter to prevent a significant proportion of the waves originating from both the front and the back of the emitter to interfere with each other. 5. The method of any one of claims 1 - 4, wherein the emitter comprises an acoustic speaker or other suitable emitter, such as an ultrasound or infrasound emitter. 6. The method of any one of claims 1 - 5, wherein one or more detectors are located proximal to the input end of the test section of conduit. 7. The method of 1 - 6, wherein the finish end of the test section of conduit is sealed to isolate the internal space of the test section of conduit and/or close the finish end. 8. The method of 1 - 7, wherein one of more detectors is located proximal to the finish end of the test section of conduit. 9. The method of any one of claims 6 or 8, wherein the detectors comprise one or more microphones or a cluster thereof, or one or more other suitable detectors, such as ultrasound or infrasound detectors. 10. The method of any one of claims 1 - 9, wherein the method utilises a feedback of the section of conduit in response to the acoustic stimulus to detect defects and/or blockages. 1 1 . The method of claim 10, wherein the method comprises analysis of the response to the stimulus (generated with certain parameters and measured in a certain configuration) of sections of conduit (having certain characteristics) in order to identify the condition. 12. The method of claim 1 1 , wherein the analysis of the response of the conduit is based on derived quantities comprising any of the impulse response and/or resonant/anti-resonant frequencies of the conduit. 13. The method of claim 10 - 1 1 , wherein the response or derived quantity obtained with the finish end open is compared to the derived quantity with the finish end closed. 14. The method of claim 10 - 1 1 , wherein the impulse response of the conduit is examined by analysing positive and negative spikes. 15. The method of claim 14, wherein the configuration of the conduit is known and used to eliminate spikes due to said configuration. 16. The method of claim 10 - 1 1 , wherein the response or derived quantity obtained is compared to a predetermined response or derived quantity obtained in the same configuration and with the same parameters for the same section of conduit at an earlier date, or for a different section of conduit known to have comparable characteristics/condition, or even a theoretical model of the section of conduit; 17. The method of claim 16, wherein a database is filled with the results of tests performed on conduits and linked to a unique identifier of the conduit to be used as predetermined responses. 18. The method of claim 16, wherein the database comprises parameters of the stimulus used to obtain the database entry. 19. The method of claim 10 - 1 1 , wherein the response of the conduit is analysed by numerically carrying out a bore reconstruction of the conduit by using, for example, a layer by layer reconstruction algorithm on the input impulse response. 20. An apparatus for detecting defects and/or blockages in conduits comprising: « an emitter for emitting an acoustic wave within a test section of a conduit at one end thereof, and • one or more detectors for measuring reflected/transmitted waves within the test section of conduit, wherein the emitter is provided in an enclosure body for location at an input end of the test section of conduit and for orienting so as to direct the acoustic wave towards a finish end of the test section of conduit, wherein the emitter is configured to produce a deterministic signal. 21 . The apparatus of claim 18, wherein the apparatus comprises a signal processor for processing the signal measured by one or more detectors to get an impulse response (or derived quantities). 22. The apparatus of claim 19, wherein the signal processor comprises a database of predetermined impulse responses (or derived quantities) along with the parameters and configuration used to measure them and it is linked with a record of known conduit characteristics/conditions. |
BACKGROUND
Technical Field
The present invention relates generally to the field of detecting defects and/or blockages in conduits. More particularly, but not exclusively, the present invention concerns a method, system and apparatus for detecting defects and/or blockages in a system or part of a system for collecting and disposing of water. The water may be collected and disposed from paved streets, parking areas, roads and pavements.
In recent years, an increase in the frequency and intensity of rainfall and snow events has been documented, particularly in the UK, which is associated with flooding in general, but also disruptions on the road network. The failures in the road network due to flooding often occur because the drains installed beneath, beside or close to the roads are partially or fully blocked or damaged and are therefore, unable to cope with the large volume of water they have to evacuate.
On the motorways and trunk road network the assessment of drains which are more than five metres long is conducted approximately every ten years. This assessment is expensive and time consuming, principally because it involves manual/visual inspections and traffic management or lane closures. Such a regime may be suitable to identify major structural failures, but it is not appropriate to detect problems that would require immediate treatment, such as blockages or building-up of debris.
The usual inspection procedure involves the use of close circuit television cameras, where equipment has to be introduced and manoeuvred into and along a section of a drain that would have previously been jetted (e.g., flushed through with water). The corresponding images are displayed for an operator to analyse and take still photographs of any features of interest. To the knowledge of the inventors this method has not been fully automated, which means that it still requires someone to look at the images, and so it is time consuming and subject to errors in addition to being difficult to implement where drains are not straight. Also, it is common for the camera to get stuck such that it cannot fully survey a drain and in some cases is unable to be removed the way it came.
It is an object of the present invention to address one or more of the problems of the known methods as discussed herein or otherwise.
Therefore, it is an object of the present invention to provide an improved arrangement for detecting defects and/or blockages in conduits.
SUMMARY OF INVENTION
One aspect the invention provides a method for detecting defects and/or blockages in conduits comprising:
(a) identifying a section of conduit for testing,
(b) emitting an acoustic wave within the test section of conduit at one end thereof, and
(c) measuring reflected/transmitted acoustic waves within the test section of the conduit.
The emitted acoustic wave is also referred to as the acoustic stimulus or simply the stimulus for the purpose of this invention.
In this method, when the acoustic wave propagating in an air-filled section of conduit encounters a change in a cross-sectional area, this change causes partial reflection and partial transmission of the wave. The reflected wave and the transmitted wave encounter more cross-section area changes along the conduit and more reflections and transmissions occur. The reflected wave and transmitted wave therefore, carry information that can be exploited to detect blockages and/or defects affecting the cross-sectional area of the conduit.
The acoustic stimulus may be emitted proximal to an input end of the test section of conduit using an emitter. Preferably, the emitter is located at the input end of the test section of conduit.
The input end of the test section of conduit may be sealed around or behind the emitter to prevent a significant proportion of the waves originating from both the front and the back of the emitter to interfere with each other. The input end may therefore, comprise a seal. At least a proportion of the acoustic wave is directed from the input end of the test section of conduit or from an area proximal thereto, towards a finish end of the test section of conduit.
Preferably, the emitter is oriented so as to direct the acoustic wave towards the finish end of the test section of conduit.
The emitter may comprise an acoustic speaker or other suitable emitter, such as an ultrasound or infrasound emitter.
The reflected/transmitted waves may be measured between the input end and finish end of the test section of conduit with one or more detectors. Preferably, one or more detectors are located proximal to the input end of the test section of conduit.
Preferably, the detector(s) are placed close to the emitter downstream of any seal if there is one.
The reflected/transmitted waves may also be measured proximal to, or at the finish end of the test section of conduit.
The detector may comprise one or more microphones or a cluster thereof, or one or more other suitable detectors, such as ultrasound or infrasound detectors.
The test section of conduit may be part or whole of a conduit comprising any route or system or part thereof for conveying things such as a pipe, drain or channel, tube or duct, or an underground tunnel or passage.
Preferably, the conduit comprises any system or part of a system that collects and disposes of water from paved streets, parking areas, roads and pavements. The conduit may be a storm drain.
The method may utilise a feedback of the section of conduit in response to the acoustic stimulus to detect defects and/or blockages.
The stimulus may take any form, since it is the transformation brought about by the conduit that is of interest.
The method aims to measure the response of a conduit when excited by an "impulse", which has an infinitely high amplitude and infinitesimal duration, with equal energy at all frequencies. Due to an impulse being a mathematical construct which is impossible to produce an approximation must be used. A pulse (i.e., a quick increase of energy level above an arbitrary base line energy state followed by a rapid decrease) is the simplest approximation of an impulse and commonly used as the stimulus for measurements of the impulse response of systems. A pulse suffers from a poor signal to noise ratio due to it having a finite amplitude and a finite duration and so having little energy.
Preferably, therefore, the stimulus comprises a much longer and well defined signal subjected to post-processing in order to achieve a "mathematical equivalent" to an impulse. Preferably, signal processing techniques comprise, for example, deconvolution of the stimulus in the frequency domain with an inverse filter. With this type of stimulus, the signal-to-noise ratio is dramatically increased by adjusting the duration of the signal without the need to increase the amplitude (therefore, minimising distortion, etc.). The result is a clear response with minimal disturbance from external factors (for example, traffic induced noise and vibrations, wind, etc.).
Preferably, therefore, the stimulus comprises a long deterministic signal. By
"deterministic signal" we mean a signal in which each value of the signal is fixed and can be determined by a mathematical expression, rule, or table. A properly chosen deterministic signal contains substantially more energy than a simple pulse, with a shape easily detectable from background noise.
Preferably, the deterministic signal comprises, for example, a maximum length sequence (which is a type of pseudo-random noise) or an exponential swept sine (where the frequency of the sine wave changes exponentially).
Preferably, the deterministic signal is subjected to mathematical postprocessing to simulate an impulse.
The method may derive an impulse response of the tested section of conduit by combining the reflected/transmitted waves with the acoustic stimulus.
The parameters that define the acoustic stimulus may be:
(a) for maximum length sequences, the length of the register used to generate the sequence, the seed of each register Boolean and the output frequency;
(b) for an exponential swept sine, the start and end frequencies, the fade in and fade out and the output frequency. The method may include steps for isolating the internal space of the test section of conduit from adjacent sections before the emitting and measuring steps. Isolating the internal space of the test section of conduit may be by any suitable method.
The emitter may be mounted in an enclosure body for insertion into the test section of conduit, or may be held at the input end of the section of conduit. The enclosure body may comprise an inflatable tube adapted to be inflated to fill the space between the enclosure body and an inner conduit wall.
A similar arrangement may be provided at the finish end of the test section of conduit, with or without detectors.
A measuring configuration for use in the method may, therefore, comprise a number of the detectors located/oriented accordingly and the use of means to isolate the internal space of the test section of conduit and/or close the finish end, for example, by use of means to fill the space between the enclosure body and an inner conduit wall.
The acoustic stimulus may be sound, ultrasound or infrasound.
The preferred frequencies of the acoustic stimulus are in the range of OHz to approximately 96000Hz. It may be preferable to have mainly plane waves in the section of conduit, in which case the optimal frequency range of the stimulus depends on the size/shape of the test section of conduit and on environmental conditions (in particular the air temperature) that affect the speed of sound. For example, in the case of a thirty centimetre diameter air filled section of conduit at about twenty degrees centigrade the frequency of the acoustic stimulus may be limited to approximately 670 Hertz. However, it may be desirable to include higher frequencies when the method is to be used to identify minor blockages or defects.
The blockage may be a partial or a complete blockage.
The method may comprise analysis of the response to the stimulus (generated with certain parameters and measured in a certain configuration) of sections of conduit (having certain characteristics) in order to identify the condition.
The response of the conduit may be analysed directly (i.e., without additional processing). Preferably, the analysis of the response of the conduit may be based on derived quantities. The derived quantities may include the impulse response and the resonant/anti-resonant frequencies of the conduit.
The response of the conduit may be analysed in one of the following ways:
(a) by examination of the impulse response and analysing positive and negative spikes, which are indicative of a decrease and an increase in the cross- sectional area of the conduit, respectively;
(b) by comparing a derived quantity obtained with the finish end of the section of conduit open to the derived quantity obtained with the finish end of the section of conduit closed (for example, using an inflatable object or a compressible rubber plug to fill the cross-section of the conduit), and the differences between the open-ended and close-ended configurations would indicate a blocked conduit;
(c) by comparing the general shape of the impulse response (or any other derived quantity, for instance the resonance and anti-resonance frequencies) with a predetermined impulse response (or derived quantities) obtained in the same configuration and with the same parameters for the same section of conduit at an earlier date, or for a different section of conduit known to have comparable characteristics/condition, or even a theoretical model of the section of conduit;
(d) by numerically carrying out a bore reconstruction of the conduit by, for example, using a layer by layer reconstruction algorithm on the input impulse response.
Where analysis comprises option (a), preferably, the conduit characteristics
(such as the location of inlets) will be known and available in a digital form so that they may be accounted for in the spike detection analysis. The method may therefore comprise creating and storing known conduit characteristics linked to a unique conduit identifier.
Where analysis comprises option (c), preferably, the predetermined impulse response (or derived quantities) along with the parameters and configuration used to measure it may be linked to a unique conduit identifier. The method may therefore comprise creating or storing one or more predetermined impulse responses (or derived quantities) along with the parameters used to measure them and a unique conduit identifier. The unique conduit identifier may be an identification number stored in the database and present at the conduit in the form of a human readable label, a barcode or a radio-frequency identification (RFId) tag. The unique identifier may also be derived from positioning information, such as GPS coordinates.
The identified test section of conduit may be approached via access points.
The test section of conduit may be between two of such spaced-apart access points. The access points may comprise a man-hole, utility hole, maintenance hole, access or inspection chamber or other suitable access point. Depending on the condition and on the nature of the internal surface of the conduit, the test section of conduit may be up to several hundred meters in length.
Preferably, the test section of conduit is between approximately five metres and approximately 150 metres in length.
According to another aspect of the present invention there is provided an apparatus for detecting defects and/or blockages in conduits comprising:
· an emitter for emitting an acoustic wave within a test section of a conduit at one end thereof, and
• one or more detectors for measuring reflected/transmitted waves within the test section of conduit.
The emitted acoustic wave is also referred to as the acoustic stimulus or simply the stimulus for the purpose of this invention.
The emitter may comprise an acoustic speaker or other suitable emitter, such as an ultrasound or an infrasound emitter.
The detector may comprise one or more microphones or cluster thereof, or one or more other suitable detectors, such as ultrasound or infrasound detectors.
In one configuration the apparatus may be placed at the input end of the test section of conduit.
In a preferred configuration the apparatus may comprise a closure means adapted to isolate the test section of conduit from adjacent sections of the conduit.
The closure means may be adapted to loosely obstruct the input end and/or a finish end of a test section of conduit to prevent a significant proportion of the emitted acoustic waves and/or reflected/transmitted waves from passing beyond the ends of the test section of conduit. Preferably, the closure means comprises a seal adapted to more or less tightly close off or completely isolate the test section of conduit.
The closure means may comprise a bung, plug or stopper. For example, the closure means may comprise an inflatable object or a compressible plug (possibly made from rubber-like material) to fill the cross-section of the conduit.
The emitter may be mounted in an enclosure body adapted to be inserted into a test section of conduit. The enclosure body may employ an inflatable tube therearound adapted to fill the space between the enclosure body and the conduit wall when inflated.
A similar arrangement may be provided with one or more detectors or without detector (if no measurement there is sought), and adapted to be inserted into the test section of conduit away from the emitter.
Preferably, the emitter is adapted to emit the acoustic stimulus as a sound, ultrasound or infrasound. The emitter may be adapted to emit a deterministic signal such as maximum length sequences or an exponential swept sine.
Preferably, the emitter/or and detector comprise a transducer.
Preferably, the apparatus further comprises a signal generator. The signal generator may comprise an amplifier.
Preferably, the apparatus comprises a signal processor. The signal processor may process the signal measured by one or more detectors to get the impulse response (or derived quantities). The signal processor may temporarily or permanently store the measured signal and the impulse response (or derived quantities), as well the parameters and configuration used to generate the emitted signal, measure the response and analyse the test section of conduit.
The signal processor may be adapted to:
(a) identify positive and negative spikes, which are indicative of a decreases and increases in cross-sectional area of the test section of conduit, respectively;
(b) compare the impulse response obtained with the finish end of the test section of conduit open with the impulse response obtained with the finish end of the test section of conduit closed, the open-ended and close-ended impulse responses being different if the test section of conduit is not blocked; (c) compare the impulse response (or any other quantity derived from the measurement) with a set of predetermined impulse responses (or derived quantities) obtained with the same configuration and parameters for the same section of conduit at an earlier date, or for a different section of conduit known to have the same characteristics/condition, or even for a theoretical model of the section of conduit, in order to detect changes.
(d) numerically carry out a bore reconstruction of the conduit by, for example, using a layer by layer reconstruction algorithm;
The signal processor may comprise a database of predetermined impulse responses (or derived quantities) along with the parameters and configuration used to measure them and may be linked with a unique conduit identifier.. The signal processor may be adapted to compare the test impulse response (or derived quantities) with one or more impulse responses (or derived quantities) predetermined.
The signal processor may comprise a database of conduit characteristics
(such as the location of inlets) so that they may be accounted for in the spike detection analysis.
According to a further aspect of the invention there is provided a method for inspecting conduits comprising:
(a) identifying a section of a conduit for testing,
(b) emitting an acoustic wave within the test section of conduit at one end thereof, and
(c) measuring reflected/transmitted waves within the test section of conduit. It will be appreciated that the preferred features described in relation to the first aspect of the invention apply to this aspect of the invention.
According to yet another aspect of the present invention there is provided an apparatus for inspecting conduits comprising:
an emitter for emitting an acoustic wave within a test section of conduit at one end thereof, and
a detector for measuring reflected/transmitted waves within the test section of conduit.
It will be appreciated that the preferred features described in relation to the second aspect of the invention apply to this aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention, and to show how exemplary embodiments may be put into effect, reference will now be made to the accompanying drawings in which:
Figure 1 is a schematic view of a system for inspecting conduits to detect defects and/or blockages;
Figure 2 is a flowchart showing the steps of a method for inspecting conduits to detect defects and/or blockages; and
Figure 3 shows an example of an exponential swept sign signal with (a) non-flat frequency response, (b) the inverse filter (c) it is convolved with, which also has a non-flat frequency response (d) but with the opposite slope, the obtained approximation of an impulse (e), which exhibits a flat frequency response (f) in a desirable frequency range. DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
As shown in Figure 1 , an apparatus for inspecting conduits 1 to detect defects and/or blockages 1 comprises an emitter in the form of a speaker 2, a detector in the form of one or more microphones 4, a signal processor 5 and a signal generator 6.
The speaker 2 is mounted in an enclosure body 7 such that a diaphragm 2a of the speaker 2 is supported in a front wall 8 of the enclosure body 8 and the frame 2b and other components extend into the enclosure body 7. The enclosure body 7 has a cross-section that generally matches that of the cross-section of the section of conduit 1 being tested. For example, where the section of conduit 1 is circular in cross-section, so is the enclosure body 7.
In the present embodiment, inflatable tubes 9 are provided around the enclosure body 7. The inflatable tubes 9 are attached to a periphery of a side wall 1 1 of the enclosure body 7, one located close to a front end where the side wall 1 1 adjoins the front wall 8 and another around a rear end where the side wall 1 1 adjoins a rear wall 10, so as to be adapted to fill the gap between the side wall 1 1 of the enclosure body 7 and an inner wall of the conduit 1 once inflated. It will be appreciated, that in a different embodiment, there is only one inflatable tube 9 that could be attached to the periphery of the side wall 1 1 at any point between the front wall 8 and the rear wall 10 of the enclosure body 7. In the present embodiment, the enclosure body 7 comprises a handle 12 mounted on the rear wall 10 of the enclosure body 7.
In the present embodiment, the speaker 2 is connected to the signal generator 6 via connection 13, the microphones 4 are connected to the signal processor 5 via connection 14 and the signal processor 5 is connected to the signal generator via connection 15.
In the present embodiment, connections 13, 14, 15 are hard wired, although it will be appreciated that for ease, the hard wired connections 14 and 15 are substitutable for wireless connections and may employ a wireless communication protocol.
In the present embodiment, the signal processor 5 communicates with a memory unit 16 comprising a database 17 used to store impulse responses. The database 17 comprises the following information in a number of records, each record comprising:
(a) a unique identifier for a section of conduit;
(b) condition of the test section of conduit (for instance presence and extent of the blockage, nature of the blockage, distance from the input end, cleanliness of the internal walls and whether the conduit had been previously jetted, etc.);
(c) parameters and configuration used for the measurement (including the register length, seed and output frequency for maximum length sequences, and the start/end frequencies, fade in/out and output frequency for a exponential swept sine, location and orientation of microphones, etc.);
(d) impulse response (or derived quantities) obtained when the finish end of the test section was opened and/or closed.
As shown in Figure 1 , a system for detecting defects and/or blockages in a conduit comprises the speaker 2 located at an input end 3 of an identified test section of conduit 1 and one or more microphones 4 located within the test section of conduit 1 . The microphones 4 are located anywhere in the conduit between the input end 3 and finish end of the section of conduit. In the present embodiment, the microphones 4 are located in front of the enclosure body 7 and are suspended in front of the speaker 2 on supports 4a extending from the front wall 8 of the enclosure body 7. It is appreciated that the location and orientation of the microphones 4 with respect to the speaker 2 is to be recorded and preferably remain the same to allow the accurate comparison against other impulse responses (or derived quantities).
The enclosure body 7 containing the speaker 2 is sized (and shaped) so as to slide comfortably into the input end 3 of the test section of conduit 1 with the inflatable tubes 9 provided around the side wall 1 1 in order to adapt to the specific shape and diameter of the conduit if needed.
In use, a test section of conduit 1 is identified. Typically, the test section of conduit 1 is governed by existing conduit access points, such as manholes or the like. Therefore, a section between two access points is chosen.
The whole apparatus is inserted from the input end 3 of the section of conduit 1 .
The handle 12 on the enclosure body 7 is then used to position the enclosure body 7 at the input end 3 of the test section of conduit 1 . At this stage, a gap between the side wall 1 1 of the enclosure body 7 and an inner wall of the test section of conduit 1 is present around at least a proportion of the side walls 1 1 .
The inflatable tubes 9 are inflated using any suitable means, for example, an integrated or manual pump, until the then inflated tubes 9 fill the gap between the side wall 1 1 of the enclosure body 7 and the test section of conduit 1 .
From a finish end of the test section of conduit 1 , a similar enclosure body arrangement, or a bung is inserted into the section of conduit 1 to act as a closure arrangement.
The role of the enclosure body 7 at the input end 3 and closure arrangement provided at the finish end (when used) is to isolate the section of conduit 1 from other sections of conduit and provide at least a partial sound barrier. The arrangements reduce and may minimise or altogether prevent sound leakage from the test section of conduit 1 and may minimise or altogether prevent sound pollution from upstream and downstream sections of conduit in order that a more accurate impulse response can be recorded.
In one embodiment, measurements made with and without the closure arrangement provided at the finish end are used to determine if the conduit is blocked, whereby the impulse response (or other derived quantities) would be expected to be the same or similar if the section of conduit 1 was blocked, but different if not blocked.
If the impulse responses are the same or similar, other measurements may be carried out with this time the whole apparatus inserted from the finish end of the test section of conduit (with and without the closure arrangement provided at the input end) for confirmation of the blockage and to inspect the section of the conduit not yet covered.
Referring to Figures 1 and 2, the signal generator 6 is used to generate the stimulus (A). This acoustic signal is amplified (B) and sent to the speaker 2 via connection 13, from which the signal is emitted (C) as an acoustic wave into the section of conduit 1 downstream of the speaker 2. The acoustic wave travels through the test section of conduit 1 .
When the travelling acoustic wave encounters a change in cross-sectional area of the test section of conduit 1 between the input end 3 and the output end due to blockage or defect, the wave is partially reflected by the blockage or defect. Depending on the extent of the blockage or defect, the acoustic wave may be partially transmitted beyond the blockage or defect.
The microphones 4 detect the emitted acoustic wave and any reflected/transmitted waves (D) and convert the response back to an analogue or digital electrical signal. The electrical signal is communicated to the signal processor 5 via connection 14 (E).
Depending on the accessibility and on the configuration of the test section of the conduit 1 the following is true:
(a) a single measurement is made with only the enclosure body 7 at the input end 3 and the finish end of conduit left open (i.e., open-ended conduit configuration);
(b) two measurements are made, one with the finish end of conduit 3 left open (i.e., open-ended conduit configuration), and another one with a similar arrangement or a bung provided at the finish end of conduit 17 (i.e., close-ended conduit configuration).
Once received by the signal processor 5, the electrical signal is processed to obtain the impulse response of the section of conduit (F).
Referring to Figure 2, the impulse response obtained in the open-ended conduit configuration is subject to one of the following: • analysed to detect spikes that cannot be attributed to the design of the conduit, but to an increase or decrease of the cross-sectional area (G);
• compared against the impulse response obtained when the finish end of the conduit was closed (if it has been possible to carry out this measurement), to determine if the conduit is blocked (H);
• used to numerically perform a bore reconstruction of the conduit, for instance using a "layer peeling" algorithm (I);
• compared against the impulse response or any other quantity derived from the measurement obtained for the same section of conduit at an earlier date or for a different section of conduit having comparable characteristics (cross- section, material, construction, etc.) and condition (clean walls, etc.), to determine if any change has taken place in the conduit since the measurement was obtained or if the response of the test section of conduit differs from what would be expected from a virtually identical section of conduit (J).
The test parameters, measuring configuration and related impulse responses (or derived quantities) for the test section of conduit 1 can then be recorded in the database for future use as a predetermined impulse response (K).
Once the condition of the section of conduit 1 has been determined, a decision as to whether further investigation of the section of conduit 1 is required can be taken. Where a blockage is found, the nature of the blockage may be further investigated using known visual/manual techniques.
With the present arrangement, a simple and time efficient preliminary investigation can be made to identify whether a section of conduit requires further investigation before employing time consuming techniques and expensive equipment and implementing heavy traffic management. The method, apparatus and system therefore, minimise time spent on conduits with minor or no problems, loss of expensive equipment and traffic disruption.
The above embodiment is described by way of example only. Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention.