Methodology for leak detection

Sep 28, 2006

New pipelines and in particular existing mains and service lines can start to leak due to bad joints, deterioration, stress in the soil and corrosion. This could lead to more extensive damage and loss of precious water, and therefore revenue. Finding a leak and pin-pointing the location will have an impact on the extent of rectification works, environmental burden and investment.

Utility Services possesses years of experience in undertaking proactive leak detection of water mains and service pipes to identify the location of hidden water leaks.
The initial survey of water mains is carried out using electronic listening sticks that analyse any unusual noise coming from a water main fitting or a water meter in order to determine the likely location of leakage. For accuracy, any operational noise generated by normal usage will be eliminated.
Once a potential leak is evident, the specialist leak detection technician determines the exact location of the leak through data evaluation.
The preferred method of finding water leaks is a system called 'Soundsens' that was developed by UK company Radcom. It is a radically improved system that combines noise logging and leak noise correlation into a single process.
The Soundsens approach is based on the deployment of highly sensitive and accurate loggers, called 'pods'. The pods, which are time synchronised, record sound in short bursts that last for a few seconds. This recording is repeated multiple times to separate normal use from suspected leakage. The duration of recording, the number of recordings and the dwell time between each recording is programmable and depends upon the pipe material in question and also whether the test is taking place during the day or at night.
The pods have a built-in digitally amplified accelerometer that is capable of detecting lower levels of sound that can be expected from conventional designs which correlate sound velocity between two points.
The data from each pod is then transferred to a laptop where a layout of the pipe work is graphically drawn either using GIS data or as a simple sketch. The layout enables the software to both link and take into account the spatial relationship between the pods.
Once the layout is complete, the software uses proprietary algorithms to amplify the sound and filter out anomalies. Correlation takes place between each pod in the array. The cross-correlation is unique to the Soundsens system and enables greater certainty in pin-pointing leaks as it discerns leak noise from other water sounds.
All leaks are then identified on the pipe layout diagram, tabulated and ranked in order of probability. The software will also show any correlations that should be subjected to further investigation. To help with this, the operator can listen to the sound using the software’s audio feature. The data files can be stored on a computer for additional analysis or to be used at a later date for reporting and tracking purposes.
As with any technical equipment, it is only effective in combination with the operator's skill. Utility Services employees have many years of experience in the field of using this equipment with proven success in the water industry.
The Soundsens pod will then be deployed on valves, hydrants and or water meters to ensure coverage of no more than 200 m between pods. This will ensure a greater reliability of locating water leaks.
As the loggers do not require a transmitter like the conventional correlator, there is no great need for traffic management or diversion during the correlation process.
Data management is integral in ensuring the effective operation of the program. Utility Services is able to extract zone data from the 'Small World' GIS system into Geomedia to provide period reports and graphical presentation on the process of the program.
Utility Services is committed to the long term benefits associated with reducing non-revenue water through leakage detection, pressure management, asset renewal and emergency response to asset failures.



This article was first published in Trenchless Australasia.

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