United Kingdom Society for Trenchless Technology: UKSTT - Location, Detection & Inspection
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Click here to view all UKSTT Members involved with CCTV.
Click here to view all UKSTT Members involved with Radio/Electromagnetic Detection.
Click here to view all UKSTT Members involved with Ground Probing Radar.
The first ground penetrating radar survey was performed in Austria in 1929 to sound the depth of a glacier. Since then its development has permitted extensive use in many sectors of industry from utilities to archaeology. GPR uses electromagnetic wave propagation and scattering to image, locate and quantitatively identify changes in electrical and magnetic properties in the ground (Olhoeft, 2000).
It can be used on the earth's surface, in pipelines such as sewers, in or between boreholes and from aircraft or satellites. The resolution of the image produced depends on the ground strata but with favourable conditions it is in the magnitude of centimetres. Again depending on antennae and the material properties of the soil, it can successfully penetrate down to about 10m to detect most utility network services. In chalk strata for example, surveys have recorded accurate feature sizes down to depths of 22m. Sub surface detection of features depends on the location of the antenna and the contrast in magnetic and electrical properties of the feature. Careful interpretation of the raw radar data can provide valuable information such as depth, orientation, size and shape of buried objects, density and water content of soils, and much more. It is this ability to detect differences in the density and water content of soils around pipe lines that allows GPR to be used to detect water leakage from mains, voids and infiltration to and ex-filtration from sewers.
The need to "interpret" the data continues to deter Water Companies from more extensive use of GPR. The example shows a colour image of the raw data direct from the radar system. From this example it can be seen that a high level of skill and experience is required to interpret the raw data prior to filtering and provide the Water Companies with data that they can understand and use. It also remains the bottleneck between the collection of data and the supply of useful information to the client.
Example of GPR data courtesy of Wide World (www.wideworld.co.uk)
Click here to view all UKSTT Members involved with Sonar.
Click here to view all UKSTT Members involved with Infra-Red Thermography.
Click here to view all UKSTT Members involved with Mapping & GIS.
Most if not all Utilities hold information about their networks electronically. These systems provide the ability to display a utility's networks in relation to a background map. This allows utilities to hold accurately surveyed information to pinpoint the exact location of their services although data accuracy is still a contentious issue with many utilities. Data in systems such as Geographical Information Systems (GIS) is held as features or objects and each feature can be held as a separate map layer allowing users to customise the display. GIS is essentially a large database holding both spatial attributes such as "X" and "Y" coordinates or grid reference and textual attributes such as size, material or year laid. The spatial attributes allow the other data to be displayed against a map background.
There are many GIS on the market today offering utilities a wide choice of functionality. Most systems require additional application development over and above the "off the shelf" package to allow specialist spatial analysis of the data.
Click here to view all UKSTT Members involved with Leak Detection.
Since its peak in 1994/95 leakage has fallen by a commendable 33% or the equivalent of the daily needs of about 12 million people. The 2001/02 leakage level was down to 146 litres per person per day, the equivalent of 1.5 baths per person per day. However, although UK leakage is being reduced, at 3240 Ml/d or about 2050 Olympic size swimming pools a day, UK leakage is still quite considerable. The average cost of producing portable water at the tap is 0.07p per litre making the cost of UK leakage about £2million a day.
Against this background of continuing pressure to reduce leakage levels many water companies find themselves at or near to their Economic Level of Leakage (ELL) and are therefore needing to look at the advances in detection technology, trench less renovation methods and other rehabilitation techniques to provide the reduction in costs. Traditional methods such as correlation and step testing can now be supplemented by exciting new techniques such as Ground Penetrating Radar
Click here to view all UKSTT Members involved with Intelligent Pigging.
The purpose of intelligent pigging is to assess the condition of a metallic pipeline. By far the majority of pipeline inspection is on steel pipes with some on Ductile Iron pipe. There is a selection of pigs available to determine different aspects of pipe condition. The loss of wall thickness can be determined, lamination can be detected as can damage to a pipeline. In the majority of instances differential pressure across the pig is used to move it forwards at a controlled speed. On board intelligence records data regarding the pipelines condition and location, which can then be used to locate any faults found from ground level, following down loading of the information at a data gathering facility.
For smaller pipelines ie. 100/150 mm dia and for short lengths of pipeline a tether pig can be used. This enables live data to be transmitted via an umbilical cable from the pig to an above ground station. Conventional pigs are commonly run live, meaning whilst the pipeline is in operation. Tethered pigs are most usually used whilst the pipeline is not in use.
