Multisensor data fusion for the simultaneous location and condition assessment of underground water pipelines

Pipeline Leak Detection Systems and Data Fusion: A Survey

“…Future directions for developing and improving leak detection systems are varied from increasing the accuracy, by minimizing the false alarms and precisely determining the leak position, to using the new technologies in improving these types of monitoring systems, such as machine learning, Internet of Things, and drones monitoring. [20], [17], [21] Acoustic-Fiber Optic -Long Term monitoring -Fiber can be additionally used for data communication purposes -Excellent in detection of leaking joints and weld leaks -Expensive -Easy to break but difficult to repair [27], [17] Acoustic-Inline -Applicable for all Pipe size and diameter -Tethered accurately pinpoint leaks, non-tethered can survey long distances -Risk of losing free swimming hydrophones -Tethered hydrophone needs flow rate to flow along the pipe [2], [30], [53], [10] Broadband Electromagnetic(BEM)…”

“…-Independent of frequency so independent of electromagnetic interference -Detect cracks and other anomalies -Works only for ferrous pipes, Intensive postprocessing -Pipe must be drained, exposed and opened -Exorbitant amount of data to be processed -Manual, time consuming and labor intensive -Subjective as it depends heavily on expert judgment [10], [2] Closed Circuit Television Inspection (CCTV) -Examine pipe wall surface for defects -Lack of consistency and reliability -Surveys only above the waterline -Real time assessment needed-though some new automated processing techniques [11], [32], [8], [17] Eddy Current -Good for small metallic pipes -Access to pipe required -Skin effect limits testing only on the surface near to the probe [52], [17] Ground penetrating radars (GPR)…”

“…-Used from the surface -Independent of pipe materials -Hard to interpret, highly skilled personnel needed to interpret results -Need to choose a right frequency for different soils -Metal objects in ground can raise false alarms [53], [10], [8], [12] Impact Echo or Spectral Analysis of Surface waves -Detects voids, cracks and overall condition can detect entire length of pipe investigate both pipe and soil conditions -Thorough cleaning needed -Access to pipe needed to excite the pipe Presence of tuberculation in pipe mains will render the echo dysfunctional -Cannot detect extent of cracks [8] Infrared Thermography -Used from the surface, non-invasive -Can cover large areas without excavation -Accurately determine geometry and defects -Can scan entire length of pipe -Useful only with liquids and gas having higher temperature than surroundings -Weather restrictions such as wind speed and ground cover can influence results Expensive -Significant Training and Experience needed -Unable to measure depth [17], [10], [8], [2] Laser Scanning -Reduce the cost of testing considerably -Can be coupled with algorithms to classify the detects -Inspect only dry portions of pipe -Time consuming [53], [11], [17] Listening Sticks -Simple and cheap -Success depends on experience of user -Background noise can cause erroneous detection -Can only detect area of the leak, not the number and positions of leaks [17], [8], [21] Magnetic Flux Leakage (MFL) -Exact location, size and shape of the defects -Reliable, low operational costs, suitable for small diameter pipes(<=12 in) -Suitable for cast iron and steel pipes -Access to Pipe required -Test results require human expertise -In-line MFL has size limitation, external MFL requires costly excavation of pipes [28], [42], [32], [8], [17], [1] Remote Field Eddy Current (RFEC) -Reliable, low operational costs -Suitable for small diameter pipes(<=12 in) -Only for metallic pipes -Health and safety issues -Not available for cement/asbestos pipes small leaks not detectable -Pipelines need to be dewatered [28], [1] [40]…”

“…A good use of the complementary features from sensors reduced the false alarm rate significantly. Reference [2] proposed a multisensory data fusion architecture to assess the locations and structural conditions of the buried pipes.…”

Ground Penetrating Radar as a Contextual Sensor for Multi-Sensor Radiological Characterisation

“…The fusion of radiation and EMI sensors discussed in Section 2.2.2 tries to solve the case of radiation waste buried underground. However, EMI sensors can only detect metals and provide limited and unreliable target depth information [ 46 ]. Nevertheless, the successful fusion of both sensors shows the possibility of integrating radiological sensors with more advanced geophysical sensors like GPR.…”