The following factors affect the loudness and the frequency range of the sounds made by water leaks, and the way the noise spreads:

Transcription

1 1. LEAK DETECTION AND LOCATION 1.1 ACOUSTIC LEAK DETECTION AND LOCATION Acoustic Leak Detection in General Acoustic leak detection methods are those that utilise the noise generated by the leak to detect the leak and determine its location Principle of operation When pressurised water leaks out from a hole in a pipe, there will be a loss in energy in the water. Some of this energy is transformed to noise, which spreads in all directions through the soil, and some of this noise reaches the surface. Some noise spreads longitudinally through the pipe and through the water in the pipe (a very complicated phenomenon not described in detail here). Different techniques can be used to find the leakage from locating the source of the noise Noise produced by leakage There are three different, commonly identified sounds produced by water leaks in underground pressurized water pipes: Pipe resonance and vibration from orifice pressure reduction. Water impact on the surrounding soil. Water circulation and flow in the surrounding soil cavity (1 of 113)20/02/

2 Loudness and frequency of leakage noise The following factors affect the loudness and the frequency range of the sounds made by water leaks, and the way the noise spreads: Water pressure in the pipe (pressure drop in the water) Pipe material and pipe diameter Soil type and soil compaction Depth of soil over the pipe Surface cover: grass, loose soil, asphalt, concrete slab, etc Sound frequency Frequency is measured in Hertz (Hz). Filters can be used to pick up only the desired frequencies, and hence filtering away unwanted noise. From theory, the first fundamental frequency occurs at approx Hz Pressure loss and noise The pressure loss in the water traveling from the pipe to the surroundings is to some extent proportional to the loudness or intensity of the leak sound (for lower frequencies, the amplitude does not increase so much as for higher frequencies with increasing pressure) Technology attributes Refer to the specific technologies for acoustic leak detection Requirements of use aaaaa \' Pipe diameter Large diameter pipes transmit less sound from water leaks and produce lower frequency sounds than small diameter pipes (this is not only due to the diameter, but also the SDR value of the pipe) Pipe material Metal pipes transmit water leak sounds that are louder and have higher frequency than the noise from PVC pipes or asbestos-cement pipes. For that reason, leaks in metal pipes are easier to detect using acoustics. (2 of 113)20/02/

3 Surrounding soil sound absorption Sandy soil and "loose" soils, do not transmit the sounds of water leaks very well, nor do water saturated soils such as bogs and swamps. Hard, compacted soil transmits the sounds of water leaks best Noise reduction The noise does not decline linearly, it declines faster near the noise source (mathematically it varies exponentially with the reciprocal of the noise), and the decline also varies for different frequencies. Example - NRC study on plastic pipes - noise amplitude diminish rate: 0.25 db/m or higher Pipe depth Because soil absorbs the sounds of water leaks, it is difficult to hear the sounds of water leaks deeper than 2 m from the surface (but for longitudinal spreading the depth doesn\'t matter) Surface cover The ground cover can make a difference. Hard surfaces resonate with the sounds of the water leak, and the leak may be heard several metres on either side of the water pipe. Grass and loose dirt surfaces do not offer such a resonating plate-like surface. However, the surface listening equipment must be located precisely above the pipe in order to measure the peak in the signal Outline price In general, costs are for acoustic methods medium to low compared to the other leak detection and location technologies described in this project. The table below assesses cost for investment and operation for the sub-groups of acoustic methods. Technology Investment Operational cost (labour) microphones medium medium listening sticks low high noise loggers medium medium correlators medium medium (3 of 113)20/02/

4 Some useful links Manufacturers normally offer acoustic listening devices such as microphones, ground microphones, listening sticks, noise loggers, correlators, software, etc. in a wide range of options. RADCOM Technologies, Inc. 150-L New Boston Street, Woburn, MA01801, USA Casella Spectrascan Regent House, Wolseley Road, Kempston, Bedford, MK42 7JY, United Kingdom Tel: Fisher Research Laboratory 200 West Willmott Road, Los Banos, CA93635, USA Tel: Flow Metrix Inc. 2 Clock Tower Place, Suite 425, Maynard, MA01754, USA (4 of 113)20/02/

5 Tel: Fluid Conservation Systems, 2001 FORD CIRCLE SUITE F, MILFORD, OHIO, 45150, USA Tel: Fuji Tecom 1-11 Izumi-cho, Kanda, Chiyoda-ku, Tokyo, JAPAN Tel: Goldak / UDSEC P.O. Box 1988, Glendale, CA 91209, USA Tel: Gutermann Messtechnik Alte Landstrasse 116, CH-8702 Zollikon, Switzerland Heath Consultants (5 of 113)20/02/

6 2085 Piper Lane, London, OntarioN5V 3S5, CANADA Tel: Hermann Sewerin GmBH Robert-Bosch-Str.3 D Gütersloh GERMANY Tel: Joseph G. Pollard Co. 200 Atlantic Avenue, New Hyde Park, NY11040, USA Tel: Metravib R.D.S. 1, rue des Vergers, Limonest, FRANCE Tel: Palmer Environmental Ty Coch House, Llantarnam Park Way, Cwmbran,NP44 3AW, United Kingdom (6 of 113)20/02/

7 Primayer Limited 2, The Spinney, ParklandsBusinessPark, Denmead, Hampshire, PO7 6AR, England Tel: Metrotech 488 Tasman Drive, Sunnyvale, CA 94089, USA Tel: SebaKMT Vertrieb Dr.-Herbert-Iann-Str.6, D Baunach, Germany SubSurface Leak Detection, Inc Moorpark Avenue, Suite #104, San Jose, California 95117, USA Wagamet (7 of 113)20/02/

8 Staffelnhofstr.18, CH-6015 Reussbühl, SWITZERLAND Tel: Leak Noise Correlators Method that uses the "fingerprint" of a noise simultaneously measured with a sensor on each side of a leakage and cross-correlated to find time delay in signal to pinpoint the leakage location. The noise from a leakage produces a special frequency pattern that varies over time (one could say it sends out "fingerprints"). Microphones are used to record the noise on both sides of the leakage, typically in manholes or on the spindle extension of a valve. The time delay of the frequency pattern ("fingerprint") is then measured, and knowing the velocity of the sound spreading from the leakage, the time delay is used to calculate the distance from either manhole to the leakage (modern equipment calculates this automatically) Principle of operation Technology attributes The necessary equipment is: two sensors (microphones) with transmitters correlator unit transmitter/ radio unit headphones transport case with adapters, chargers etc. software (8 of 113)20/02/

9 Microphones Two types are used: accelerometer (piezoelectric) which measures vibrations hydrophones, which measure the sound Both types normally have magnets for easy attachment to a valve. Two microphones are used for one measurement, they typically have different colours (red and blue) Correlator Correlation means mutual relation or dependence. The modern correlator receives the signal from the microphones, and can utilise some filtering to concentrate on the desired frequency range. The signals from the two microphones are compared, and the distance to the leak is calculated and strategic information shown in a LCD display. Correlators integrated in laptops are also available Software Data is transferred to a PC by RS 232 cable (typical), and software allows analysis of measured results and storage Optional: correlator operating on the surface A correlator called "Magic Carpet" that works on the surface is commercially available. The equipment consists of a 1.5 metres long "carpet" and has an array of sensors which use surface noise correlation to display any leak noise profile on a LCD screen. Headphones can be used to sample the channels sequentially in stereo, acting as a row of eight simultaneous listening sticks. The equipment is used for pinpointing leaks, as a major limitation is the spreading of noise to the surface. The exact pipe location should be known, but can also be found using the equipment. The system is supposed to locate most leaks, even when the noise produced by the leak is very low, or when there is intermittent background noise Optional: combination with pressurized air If the operating water pressure is low, it\'s possible to add pressurized air to increase the energy drop over the leakage, and hence increase the noise produced. The air can be inserted through service valves or through a customer service connection. Equipment and operations are complicated using this technique. (9 of 113)20/02/

10 Requirements of use Sound velocity The velocity of the sound (m/s, km/h, ft/s...) can either be measured by sending noise from one measuring point to the other, or it can be estimated when the pipe material, diameter and wall thickness is known Pipe length The length of the pipe (or rather the length between the two measuring points) must be measured exactly. If this is not measured exactly, the error in distance to the leak will be half the error in measure distance between the measuring points (if the pipe is measured 4 metres too long, the error in distance from the measuring point to the leak will be 2 metres) Pipe homogeneity The pipe must be of uniform material and diameter on the section between the measuring points. If this is not the case, this can be compensated if the exact locations of the change of material or diameter are known Health issues-operator No particular issues with this equipment compared to other field detection leak equipment. Coaching of the operators is advised Health issues - hygiene When inserting a device directly into the water in the pipe, it is imperative that the equipment is sterile and that all operations take into consideration that no pollution shall enter the pipe Outline price Correlator 20k (10 of 113)20/02/

11 Potential suppliers Manufacturers normally offer acoustic listening devices such as microphones, ground microphones, listening sticks, noise loggers, correlators, software, etc. in a wide range of options. RADCOM Technologies, Inc. 150-L New Boston Street, Woburn, MA01801, USA Casella Spectrascan Regent House, Wolseley Road, Kempston, Bedford, MK42 7JY, United Kingdom Tel: Fisher Research Laboratory 200 West Willmott Road, Los Banos, CA93635, USA Tel: Flow Metrix Inc. 2 Clock Tower Place, Suite 425, Maynard, MA01754, USA Tel: (11 of 113)20/02/

12 Fluid Conservation Systems, 2001 FORD CIRCLE SUITE F, MILFORD, OHIO, 45150, USA Tel: Fuji Tecom 1-11 Izumi-cho, Kanda, Chiyoda-ku, Tokyo, JAPAN Tel: Goldak / UDSEC P.O. Box 1988, Glendale, CA 91209, USA Tel: Gutermann Messtechnik Alte Landstrasse 116, CH-8702 Zollikon, Switzerland Heath Consultants 2085 Piper Lane, London, OntarioN5V 3S5, CANADA Tel: (12 of 113)20/02/

13 Hermann Sewerin GmBH Robert-Bosch-Str.3 D Gütersloh GERMANY Tel: Joseph G. Pollard Co. 200 Atlantic Avenue, New Hyde Park, NY11040, USA Tel: Metravib R.D.S. 1, rue des Vergers, Limonest, FRANCE Tel: Palmer Environmental Ty Coch House, Llantarnam Park Way, Cwmbran,NP44 3AW, United Kingdom (13 of 113)20/02/

14 Primayer Limited 2, The Spinney, ParklandsBusinessPark, Denmead, Hampshire, PO7 6AR, England Tel: Metrotech 488 Tasman Drive, Sunnyvale, CA 94089, USA Tel: SebaKMT Vertrieb Dr.-Herbert-Iann-Str.6, D Baunach, Germany SubSurface Leak Detection, Inc Moorpark Avenue, Suite #104, San Jose, California 95117, USA Wagamet Staffelnhofstr.18, CH-6015 Reussbühl, SWITZERLAND (14 of 113)20/02/

15 Tel: Permanent Noise Loggers Principle of operation Set of several digital correlating loggers placed in a water network for a period of time (one night up to permanent installation) with the purpose to give alarms when leaks are detected or locate the exact position of leaks combining the results from all the loggers. Leak sound loggers are placed at strategic locations in the network on valves or other pipe fittings. For permanent logging, the purpose is to give alarms when leak noise is detected. For pinpointing of leaks, loggers are installed for a period of time, typically one night. The exact location of each logger is placed in a digital map of the network. Information in the loggers is downloaded to a computer via a special docking device, or by wireless communication. The data is then analysed (correlated) using special software to locate leaks in the network Technology attributes The necessary equipment is: Loggers Data transfer unit (docking station) PC for analysis of results Software headphones for in situ listening of acoustic signal Logger Is typically small, compact, battery powered, waterproof, easy to operate, communicate wireless for data transfer, and have some basic programming functions. (15 of 113)20/02/

16 Data transfer Some systems transfer data from logger to PC via IR, others use radio, which allows "drive-by" download of data, and some use GSM, which allows downloading of data to a desktop PC. Some loggers also have a receiver, which enables remote programming of the logger Map of network Digital/GPS. Necessary for logical placement of loggers. Some have GPS/ automatic transfer of location to GIS systems Analysis software Features automatic correlation or noise interpretation analysis, some can access via internet. Trend analysis, storage of historical data. Some also have software for PocketPC Requirements of use Number of loggers From three upwards Distance between loggers m Required skill of operator Equipment is easier to use and requires less experience than for example listening devices Health issues-operator No particular issues with this equipment compared to other field detection leak equipment. Coaching of the operators is advised Health issues hygiene None Outline price Less than one thousand Euro (16 of 113)20/02/

17 Potential suppliers Manufacturers normally offer acoustic listening devices such as microphones, ground microphones, listening sticks, noise loggers, correlators, software, etc. in a wide range of options. RADCOM Technologies, Inc. 150-L New Boston Street, Woburn, MA01801, USA Casella Spectrascan Regent House, Wolseley Road, Kempston, Bedford, MK42 7JY, United Kingdom Tel: Fisher Research Laboratory 200 West Willmott Road, Los Banos, CA93635, USA Tel: Flow Metrix Inc. 2 Clock Tower Place, Suite 425, Maynard, MA01754, USA Tel: (17 of 113)20/02/

18 Fluid Conservation Systems, 2001 FORD CIRCLE SUITE F, MILFORD, OHIO, 45150, USA Tel: Fuji Tecom 1-11 Izumi-cho, Kanda, Chiyoda-ku, Tokyo, JAPAN Tel: Goldak / UDSEC P.O. Box 1988, Glendale, CA 91209, USA Tel: Gutermann Messtechnik Alte Landstrasse 116, CH-8702 Zollikon, Switzerland Heath Consultants 2085 Piper Lane, London, OntarioN5V 3S5, CANADA (18 of 113)20/02/

19 Tel: Hermann Sewerin GmBH Robert-Bosch-Str.3 D Gütersloh GERMANY Tel: Joseph G. Pollard Co. 200 Atlantic Avenue, New Hyde Park, NY11040, USA Tel: Metravib R.D.S. 1, rue des Vergers, Limonest, FRANCE Tel: Palmer Environmental (19 of 113)20/02/

20 Ty Coch House, Llantarnam Park Way, Cwmbran,NP44 3AW, United Kingdom Primayer Limited 2, The Spinney, ParklandsBusinessPark, Denmead, Hampshire, PO7 6AR, England Tel: Metrotech 488 Tasman Drive, Sunnyvale, CA 94089, USA Tel: SebaKMT Vertrieb Dr.-Herbert-Iann-Str.6, D Baunach, Germany SubSurface Leak Detection, Inc Moorpark Avenue, Suite #104, San Jose, California 95117, USA (20 of 113)20/02/

21 Wagamet Staffelnhofstr.18, CH-6015 Reussbühl, SWITZERLAND Tel: Listening Sticks and Ground Microphones Principle of operation Devices for listening, on the ground surface or on a valve/fitting, for the actual noise of a leak, and using the noise level to pinpoint it. Units: db, Hz, m Noise from a leak is detected by the human ear, either directly or after some sort of electronic interpretation. The noise level and frequency spectrum can be logged for later comparison with other measuring points. Can be applied on the surface or on a valve/fitting. Normally, the section with the leak is found by listening to the fittings. Then, the two options are: use the difference in noise level measured on both sides of a water leak to pinpoint it, or use ground microphones on this section to pinpoint the leak by listening with 1 m intervals and assess noise volume or use the equipment\'s built-in noise logging unit to find the noise peak. When applied on the surface, the exact pipe location must be known and the equipment must be placed directly above the pipe. (21 of 113)20/02/

22 Technology attributes Old equipment consisted of a listening rod made of wood. Today, listening sticks are normally electronic, and have a microphone built-in. The advantage of using a stick is easier access to a fitting, or even penetration into soft ground. Ground microphones are also hand-held, but heavier, and have better microphones. Signals can either be accessed through a headset directly, or processed through a special unit for filtering etc. Some equipment has all the above mentioned options. Equipment packages typically consist of: amplifier/computer ground microphone headphones contact rod (listening stick) carrying case Equipment is used both for finding the pipe section with a leak, and exact location of leaks Computer/amplifier for sound analysis/digital filt Analogue or micro-processor based analyzing equipment is commercially available. This equipment allows the user to filter the sounds, analyze frequencies and volumes, record data for comparison with other listening points, and log noise level. Has meter or digital display Software Data can be transferred to a PC, and software allows analysis of measured results and storage. (22 of 113)20/02/

23 Optional: combination with pressurized air Air under pressure can be inserted in the pipe to increase the noise from the leak. Either, the pipe can be emptied for water, while pressurized air is inserted in one end of the pipe. The hole in the pipe will "whistle", making it easier to detect. For under-water applications or under ground water level, this method is well suited, as bubbles can be seen on the surface or "heard" by ground microphones. Air can also be inserted through a house connection (e.g. a tap), possibly while the pipe is in operation. This is well-suited for low pressure systems, where the energy loss over the leak is small, and hence difficult to detect Requirements of use Pipe length The length of the pipe (or rather the length between the two measuring points) must be known in order to pinpoint the leak Pipe homogeneity The pipe must be of uniform material and diameter on the section between the measuring points Pipe location The pipe location must be known when using ground microphones. Some equipment combines pipe detection and leak detection into one instrument Health issues-operator Care must be taken when pressurised air is used, and danger of explosions or damage to infrastructure due to excessive pressure must be considered. When using headset, avoid loud noise that can damage hearing Health issues - hygiene Pressure variations in the system, and the possible risk of insertion of polluted air, must be considered when using air under pressure. (23 of 113)20/02/

24 1.1.5 Outline price 70 for listening stick 2k for ground microphone Potential suppliers Manufacturers normally offer acoustic listening devices such as microphones, ground microphones, listening sticks, noise loggers, correlators, software, etc. in a wide range of options. RADCOM Technologies, Inc. 150-L New Boston Street, Woburn, MA01801, USA Casella Spectrascan Regent House, Wolseley Road, Kempston, Bedford, MK42 7JY, United Kingdom Tel: Fisher Research Laboratory 200 West Willmott Road, Los Banos, CA93635, USA Tel: Flow Metrix Inc. (24 of 113)20/02/

25 2 Clock Tower Place, Suite 425, Maynard, MA01754, USA Tel: Fluid Conservation Systems, 2001 FORD CIRCLE SUITE F, MILFORD, OHIO, 45150, USA Tel: Fuji Tecom 1-11 Izumi-cho, Kanda, Chiyoda-ku, Tokyo, JAPAN Tel: Goldak / UDSEC P.O. Box 1988, Glendale, CA 91209, USA Tel: Gutermann Messtechnik Alte Landstrasse 116, CH-8702 Zollikon, Switzerland (25 of 113)20/02/

26 Heath Consultants 2085 Piper Lane, London, OntarioN5V 3S5, CANADA Tel: Hermann Sewerin GmBH Robert-Bosch-Str.3 D Gütersloh GERMANY Tel: Joseph G. Pollard Co. 200 Atlantic Avenue, New Hyde Park, NY11040, USA Tel: Metravib R.D.S. 1, rue des Vergers, Limonest, FRANCE Tel: (26 of 113)20/02/

27 Palmer Environmental Ty Coch House, Llantarnam Park Way, Cwmbran,NP44 3AW, United Kingdom Primayer Limited 2, The Spinney, ParklandsBusinessPark, Denmead, Hampshire, PO7 6AR, England Tel: Metrotech 488 Tasman Drive, Sunnyvale, CA 94089, USA Tel: SebaKMT Vertrieb Dr.-Herbert-Iann-Str.6, D Baunach, Germany SubSurface Leak Detection, Inc. (27 of 113)20/02/

28 4040 Moorpark Avenue, Suite #104, San Jose, California 95117, USA Wagamet Staffelnhofstr.18, CH-6015 Reussbühl, SWITZERLAND Tel: Gas Tracing General Gas is injected into the main via a standard pressure tapping. In pressurised pipelines the gas is usually carried in solution. A `slug\' of gas-saturated water moves along the pipeline at a rate determined by pipe diameter and the downstream demand (this is likely to be influenced by pressure, and may be due solely to the leak). When the slug of water escapes via the leak the gas will come out of solution. Gas detection equipment is used to take readings for the occurrence of the gas along the pipeline. The technique relies on the accurate knowledge of the position of the pipelines and valving arrangements. This technique is widely used for the location of very small leaks in pressurised telecommunication cables, cooling water systems and gas pipelines. Water industry application in the UK has generally been restricted to leak location on new mains, which fail hydrostatic tests prior to commissioning. Any tracer gas used for water industry applications must be chemically inert, non-toxic, odourless, tasteless and must not affect the appearance of the water. Possible gases include sulphur hexafluoride (SF6), hydrogen (H2), helium (He) and `cocktails\' of gases produced by individual manufacturers. SF6 tracing is an established technique and is approved for use on live mains. (28 of 113)20/02/

29 1.2.1 Helium/ Hydrogen tracer Principle of operation The injection of helium and nitrogen gas into a water pipe and the external monitoring for helium gas along the pipe length using a gas detection system to locate leaks. Units: Nitrogen gas concentration as parts per million (ppm). the injection of a mixture of Hydrogen and Nitrogen gas into a water pipe and the external monitoring for hydrogen gas along the pipe length using a gas detection system to locate leaks.units: Hydrogen concentration as parts per million (ppm) Technology attributes Attribute No. or Range Comment Tracer gas Helium tracer in nitrogen Incombustible, non-toxic, noncorrosive Probe types Above ground probe, can be vehicle mounted Gas Sensor weatherproof Yes Gas Sensors battery life/ Charging Battery powered, typical life Gas Sensors sensitivity He concentration 1 ppm Traceability Gas Sensors response time 1 second Leak accuracy Leak sensitivity 1-3 l /day Success rate Commonly 100% Reset time Time delay for gas penetration through surrounding material Seconds Similar to other methods Operating temperature 0-45oC Bar holes Not required Tracer travels vertically upwards from the leak Accurate location of the leak (29 of 113)20/02/

30 Requirements of use Applications Yes or No Comments Leak Location Yes Works on all pipe material Yes Works on all ground types Yes Will diffuse through materials such as concrete Works on live pipes No? No info on use in live main Suitable for all size leaks Yes Use where moisture detection has failed Yes Moisture from a leak may travel laterally for a significant distance. Gas tracer is unlikely to behave similarly Skill level required Specialist Outline price Projects priced individually Potential suppliers Hetek Solutions Inc. Canada Gas Tracer SF Principle of operation The injection of Sulphur hexafluoride gas into a water pipe and the external monitoring for Sulphur hexafluoride gas along the pipe length using a gas detection system to locate leaks. Units: Sulphur hexafluoride gas leakage grams / year Technology attributes Attribute No. or Range Comment Tracer gas SF6 Sulphur hexafluoride Probe types Hand held Gas Sensor weatherproof Yes Hand held gas dispenser system Gas Sensors battery life/ Battery Charging Gas Sensors sensitivity 3 g /yr (ppb level) Traceability Gas Sensors response time Instantaneous 1 minute Leak accuracy Within 1 meter (30 of 113)20/02/

31 Leak sensitivity 1 l /hour Success rate 100% Reset time 2 5 seconds Time delay for gas penetration through surrounding material Operating temperature Bar holes Not required Tracer travels vertically upwards from the leak Commonly hours, but may have to wait up to 2 days in heavy clays Accurate location of the leak Requirements of use Applications Yes or No Comments Leak Location Yes Works on all pipe material Yes Works on all ground types Yes Works through dense materials such as concrete Works on live pipes Yes Suitable for all size leaks Yes Use where moisture detection has failed Yes Moisture from a leak may travel laterally for a significant distance. Gas tracer is unlikely to behave similarly Skill level required Specialist Outline price Projects priced individually Potential suppliers Conco systems, (31 of 113)20/02/

32 1.3 Ground Penetrating Radar GPR Ground Penetrating Radar GPR Main principle - electromagnetic signal General term (ground probing radar, subsurface radar, georadar, earth sounding radar) applied to techniques which employ radio waves, typically in the MHz frequency range, looking downwards into earth, water, ice and man-made materials for non-destructive detection of anomalies and mapping underground structures. Main output unit is distance from surface to structure (m). An electromagnetic pulse is sent into the ground, reflected by objects in the ground, and received by an antenna. The signal can then be interpreted to locate infrastructure, water, different soil types, pollution, and other things Technology attributes The GPR unit consists of: a timing unit, which controls the generation of the radar signal and the detection of the receive signals as a function of time, a transmitter component, which transmits the radar signal and contains electronics and antenna, a receiver, which is similar to the transmitter as it contains an antenna (same type as the transmitter antenna) and an electronics package, device to record and display data Object reflection dielectric properties The reflection of the radar signal depends on the difference in dielectric properties between an object and its\' surroundings. Dielectric properties tend to be the most dominant factor controlling GPR responses. The dielectric constant decides the wave velocity in the medium. Penetration varies with soil/rock type and moisture, being deepest in dry sand and least in wet clays. When this constant is known, it is used to decide the depth from the surface to an object Radar signal weakening The signal is weakened on its way in many steps (source power => radiated power => power in target direction => power reaching target => power scattered by target => power reflected in receiver direction => power at receiver => power actually received => power to receiving electronics). (32 of 113)20/02/

33 System performance factor Q (db) The ratio of the source power to the receiver noise power. Is the primary factor to determine the range the radar can "see". In order for a feature to be detectable, the received power must be in excess of the noise level in the receiver Frequency Normally indicated by the centre frequency of the operating band. Has a major impact on the penetration of the radar system. As the frequency decreases, the effective area of the receiving antenna increases. Table 7.1 shows the relationship between the penetrating depth and the centre frequency. The main factors for deciding frequency are desired spatial resolution, clutter limitations, and exploration depth. Table 3.1 Typical values of depth penetration Penetrating depth (m) Centre Frequency (MHz) Bandwidth The frequency range over which the radar has available power. The wider the bandwidth is, the better is the resolution Signal processing Several types of signal processing exist, from no processing to the very advanced. Is expected to develop into more advanced methods Antenna patterns The antennas are normally dipole antennas with broad bandwidth (which means gaining better resolution, but loosing energy), and are placed on (or very close to) the ground surface, often being pulled on carts (33 of 113)20/02/

34 Typical technical system characterisation Attribute Value Comment console control and data RS232 serial port and other typical output ports console power requirement V dc typical Min: 18 x 12 x 12 cm console size Max: "large" console weight 0.5 kg more than 10 kg typical kg Trolley or cart containing all Wheeled console necessary operating equipment 100 x 50 x 50 cm in (GPR, recording unit, battery, "transport" mode odometer, etc) signal penetrating depth m Depends on energy applied and soil conditions signal frequency MHz Low frequency has better penetration and more energy demand. external computer for desktop evaluation of data digital storage up-to-date laptop hard drive & any PC medium or special data storing device typical output PC compatible printers typical recording unit Data processing and mapping software "Noggin" from Sensors & Software maximum system performance 162 db programmable sampling 10 ps 20,000 ps in 2 ps typical interval steps equivalent time sampling typical to 100 GHz rate programmable stacking 1 2,048 stacks typical programmable time window 1 ns 32,767 ns typical transmitter output 200 V typical Weatherproof (IP67), wide possible temperature range, 2 GB storage, full digital recording, 0.7A-12V, several ports Allows advanced filtering, amplifying, and other treatment and translation of signals, and also topographic corrections and linkage to geographic information typical (34 of 113)20/02/

35 transmitter size 23 x 16 x 5 cm typical transmitter weight 1.7 kg typical receiver output 16 bit digital typical receiver lsb 1.5 uv typical receiver size 23 x 16 x 5 cm typical receiver weight 1.5 kg typical GPS Yes Possible combination with GPS for most models Requirements of use Health issues The frequencies used by GPR are lower than those used by communication, and should therefore not interfere (example: GPS and GPR work well together). The power transmitted is 1/1000 of that of a mobile phone. Many primary uses of GPR relate to public health and security. Still, health provisions must be taken for the system operator, and coaching of the operators is advised Technology applicability Applications Yes or No Comments Is the target within the detection range of the radar irrespective of any unusual target characteristics? Solution: Calculate or measure the ground attenuation coefficient, and use as rule of thumb that radar will be ineffective if the actual depth is greater than 50% of the maximum Will the target generate a response detectable above the background clutter? Are there any factors that preclude GPR? range. Solution: Two rules of thumb are that the reflection coefficients between two interfaces/geological surfaces should be at least 0.01, and that the ratio of target depth to the smallest target dimension should not exceed 10:1. Solution: Infrastructure and objects in the ground may reflect and disturb the GPR, and so may objects above ground like trees and buildings. Nearby radio transmitters or other electronic devices (like cellular phones!) will also saturate the signal. (35 of 113)20/02/

36 Pipe material Method is independent of pipe material, but metallic pipes may disturb the radar signal. Soil general A soil can be thought of as a three phase system consisting of a mixture of the soil matrix, air and water. Depending on the degree of water and air in the pore space of the soil matrix on can greatly vary the electrical properties of the material, and hence the dilution of the radar signals. Clay In fine grade soils like clay, surface conduction is a major factor, and such materials will attenuate the radar signal. The use of GPR for water leakage measurements is therefore not suited in areas with clay. Ground water The presence of water is one of the most important factors determining electrical properties (dielectric constant increases dramatically with increasing water content). Depending on surrounding soil, GPR can be used to locate water in the ground, and also different types of water with different electrical properties. Salt groundwater Salt water has very high dielectric constant, and is difficult to penetrate with GPR. Strong magnetic properties Magnetic variations in the ground are normally weak or small, but may in some cases give rise to radar responses. (36 of 113)20/02/

37 Non-destructive infrastructure detection and condition assessment GPR is typically used to detect infrastructure, for example water pipes. The range of applications for this use is more extensive than for leakage detection. Other fields of use include concrete structures, geology and geophysics, building highway bridge and railway bed inspection, archaeology, environmental, snow/ ice thickness measurements, mining, and other Outline price Cost for buying GPR equipment for suitable for locating water leaks is considered to be high Potential suppliers Comprehensive list of manufacturers and contractors at: Some of the leading manufacturers are: Geophysical Survey Systems Inc. ("World Leader in Ground Penetrating Radar") 13 Klein Drive, PO Box 97, NorthSalem, NH USA Malå GeoScience Skolgatan 11 (37 of 113)20/02/

38 S Malå Sweden Sensors & Software Inc Stacey Court, Mississauga, ON, Canada In-Pipe Methods Sahara Leak Location Principle of operation SAHARA is a system for finding and accurately locating the position of leaks in trunk mains. It was designed to provide accurate results in any type, size or material of trunk main or aqueduct. The system is used in live pressurised water mains without disruption to the water supply. The system is considered to be leading edge technology. Internal acoustic inspection of a pipeline is undertaken by inserting a hydrophone into a pressurised water main. The hydrophone is attached to and driven along the pipe from the insertion point by means of pressure of water on a drogue (parachute). The hydrophone is mounted on an umbilical cable that can be retracted along the pipe using a winch adjacent to the insertion point. The hydrophone senses the noise emitted from a leak and transmits this to a monitor. An operator can manipulate the position of the hydrophone within the pipe and the position of a leak can be accurately pinpointed by means of an above-ground mobile sensor. Leak noise is detected audibly and also graphically on a monitor. (38 of 113)20/02/

39 Technology attributes Attribute Value Comment Leak noise is detected Detected audibly and also graphically on a monitor Operates effectively independent of pipe material Positional accuracy ±0.5 m Location sensor is located on ground surface immediately above in-pipe noise sensor to pin-point the leak Tethered system permits absolute control of deployment of the sensor Full operational control of forward, reverse and stopped Drogue and sensor are withdrawn through the point of entry Can be used to prove no leak exists Maximum cable length 2 km The sensor is tethered to the aboveground facilities via a cable Real time results can be viewed as survey progresses Useful tool at pipeline commissioning Can be used on a new pipe Useful tool at pipeline commissioning with pressure but no flow Sensitivity Better than 1l/hr Depends on pressure during survey higher pressure gives greater sensitivity Maximum operating pressure 16 bar Potable water quality of all insertion equipment materials Minimum operating pressure Successfully used at 0.2 bar Live water mains may be surveyed No detrimental effect on potable water Increased pressure gives increased sensitivity Maximum flowrate Has been used up to 4m/sec Minimum flowrate 0.2 m/sec On live mains where flow cannot reliably be controlled. On mains where the flow can be controlled lower flowrates can be accommodated Maximum survey length 2000m Maximum survey length depends on cable length. 2000m is currently longest economically viable length. Reliability 100% Given a point to excavate, a leak has always been found. (39 of 113)20/02/

40 Enabling works 2 tapping or larger Requires entry point of 48 mm minimum diameter Minimum diameter of pipe to be surveyed 250 mm diameter Smaller pipes (down to 150 mm) may be surveyed with appropriate entry facilities Cost Approx 2/m System outline Van based system operated by two crew Output Leak position identified and guide to size of leak Availability Service hire Requirements of use Applications Yes or No Comments Live water mains Yes Apart from sensor entry point, no valve operation required Potable water applications Yes Any pipe material Yes Risk assessment of critical pipelines Yes Proving no leak exists gives confidence in the condition of the main, and also the impact on the surrounding soil Location of a leak at an inaccessible location Yes For example in a pipe tunnel or on a pipe bridge Commissioning tool Yes Because of high sensitivity, can be used to prove no leak exists Accurate tracing of pipe routeyes This may be a further benefit in some circumstances Skill level required Specialist Outline price Projects priced individually Potential suppliers WRc (40 of 113)20/02/

41 1.4.2 Leak Location Pig Principle of operation Free flowing pipeline pig monitoring pipelines for leakage and indicating position. Internal acoustic inspection of a pipeline is undertaken by launching a pipeline pig containing a hydrophone into a pressurised water main. The pig complete with hydrophone is driven along the pipe from the insertion point by means of the flow of water. The hydrophone senses the noise emitted from a leak as the pig passes by and transmits this to a monitor. The position of the hydrophone within the pipe cannot be manipulated. Since it is free-flowing, the hydrophone cannot be retracted along the pipe to revisit a leak site without withdrawing and relaunching the pig. Leak noise is detected audibly, and also graphically on a monitor Technology attributes Attribute Value Comment Leak noise is detected Detected audibly and graphically on a monitor Operates effectively independent of pipe material Location Accuracy 0.5% of run length Velocity controlled by Can move forward and be stopped, velocity of motive water Enabling works Pig launching and receiving stations required. but reverse not normally possible As the device is a full bore pig it requires a full bore launch and receive facility on the line. Line must be piggable The line must be sufficiently smooth internally, and with limited variation in diameter to ensure the smooth passage of the pig along the line. Can be used to prove no leak exists Sensitivity 10 l/hour Maximum operating pressure 65 bar Useful tool at pipeline commissioning (41 of 113)20/02/

42 Minimum operating pressure Not known The system requires a differential pressure to drive the pig through the line. The size of leak that can be detected will increase as pressure increases. Maximum flowrate 10m/s Minimum flowrate 0.5m/s Maximum survey length >50km (or 24hours run time) Pipe size range mm Pig must be selected for particular pipe size. Maximum pipe wall 10 mm thickness Output Identification of leak position measured from ends of pipeline Requirements of use Applications Yes or No Comments In-pipe system at any length Yes Live water mains Yes Apart from sensor/ pig launch and retrieval point, no valve operation required Potable water applications Yes Any pipe material Yes Risk assessment of critical pipelines Yes Proving no leak exists gives confidence in the condition of the main, and also the impact on the surrounding soil Location of a leak at an inaccessible location Yes For example in a pipe tunnel or on a pipe bridge Commissioning tool Yes Because of high sensitivity, can be used to prove no leak exists Control of deployment of pig No Pig may follow any pipe branch where flow exists Security against pig Possibly not becoming stuck Positive location of sensor No Reverse available No An obstruction within the pipeline (tee, valve, tuberculation) may cause the pig to get stuck (42 of 113)20/02/

43 Skill level required Specialist Outline price Projects priced individually Potential suppliers BHR Hearleak system at Leak location pig: Remote Sensing Systems Thermo or Infrared photography Principle of operation Detection of temperature differences on a surface using a camera or other device that transforms the normally invisible IR rays to a picture in the visible part of the light spectrum (Latin: "thermo" = heat, "graphe" = depiction). Units: Degrees C (or F). All objects warmer than absolute zero (0 Kelvin or C) emit energy somewhere in the IR range. The warmer the object, the brighter it can be seen using a thermal camera. The camera "sees" the temperature on an objects surface. It has no ability to penetrate into an object to see what the temperature is in the interior. A water leak can therefore only be seen with an IR camera if it increases or decreases the temperature on the surface. IR wavelengths: Infrared is an invisible portion (to the human eye) of the light spectrum with wavelengths between visible light and microwaves. (0.75 to 1000 microns). Other names used for technology Infrared, infrared thermography, thermal imaging, infrared radiometry, infrared imaging, and IR condition monitoring. (43 of 113)20/02/

44 Technology attributes Different types of equipment exists, but in general the equipment consists of: infrared camera with display or eye viewer digital camera for simultaneous photography of object\'s visible light emission (for comparison and recognition) regular PC (desktop/ laptop) for evaluation of results and reporting Software Software exists for data managing, reporting etc, and is adapted to the equipment Typical technical system characterisation Attribute Value Comment Camera weight (includes 1-4 kg Typical batteries) Operating Temperature -15 to 50 C Typical Water repellency Yes (IP54) Typical (in operation) Dimensions 20x9x25 cm Typical Temperature accuracy degree C Temperature range degrees C IR wavelengths used by 8-14 micron Typical for modern equipment camera Total price for equipment Euro (xxx Typical, basic equipment sjekk lavest pris med sr automasjon) Voice recording Yes Simultaneous recording of thermal image and voice data Focusing range 50 cm to infinity Image pixels 320 (H) x 240 (V) Typical Memory Media Compact flash memory card Capacity depends on selected card Memory capacity ~1000 images Typical Video Output Analog RGB, NTSC/PAL Data transfer to PC Cable (RS), memory card etc. (44 of 113)20/02/