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Transmission Main Leak Location
(Sahara)
The tether-controlled Sahara sensor inside a pipeline pinpoints even the smallest leaks in water mains.
Without any disruption to pipeline service, Sahara can be used in any pipeline 12" diameter or larger of any material to:
- Verify hydraulic integrity. Sahara has proven so sensitive that it has been accepted as assurance of zero leakage;
- Assess the condition of critical pipes. Pipes leak before they fail. Sahara can detect leakage from the hairline cracks,
corrosion pinholes, and leaking joints that are a the early warning signs of pipe failure;
- Pass a pressure test. Sahara locates elusive leaks, helping contractors pass hydrostatic pressure tests quickly;
- Reduce non-revenue water. Utilities have used Sahara to recover as much as 17,000,000 Gallons per day of non-revenue water;
- Set a higher bar for new pipelines. Utilities are specifying Sahara surveys on new pipelines to pinpoint even the small
leaks considered acceptible in a hydrostatic pressure test.
- Map your pipeline. Sahara provides the above-ground location of a pipeline to within inches, allowing for accurate location of buried
assets;
Technology Development
PPIC is the exclusive North American licensee of the Sahara system.
Sahara was developed in the United Kingdom by the Water Research Center (WRc). WRc developed correlators, the most commonly used technique for the identification of leaks, in the early 1970's.
Of all the 'passive' forms of leak detection, correlators have been the most effective.
They have helped to significantly reduce water leakage in many areas, especially within smaller diameter
distribution networks. However, they were found to have the following limitations:
- Multiple leaks within a given monitored area often yield an unlocalizable signal.
- Leak signal strength dissipates rapidly within large diameter pipelines - pipelines over 12" (300mm) in diameter - inferring that the acoustic signal of the leak may not be practically detectable by correlators in large diameter pipe.
- Multiple diameter mains may lead to inaccurate identification of leak location.
- The leak signal is lost within pipelines that contain air pockets.
- Non-metallic mains (HDPE, PVC, asbestos cement or concrete) do not conduct the leak signal effectively. The leak noise is attenuated very rapidly as it travels away from the source in these types of pipe, inferring that correlators may have difficulty in practically identifying leaks in non-metallic mains.
- At any significant distance from the leak point background noise can corrupt the leak noise signal.
As a result, the use of correlators carries a risk, common to all forms of passive leak detection, that a leak-free survey may incorrectly classify a line as leak-free.
WRc recognized these limitations and investigated alternative methods of leak location in
large diameter water transmission mains. After careful investigation, WRc concluded that the most
reliable method of detecting leaks, and pinpointing their position accurately, would be to pass a
sensor through the pipe and determine the point where the leak noise signal was at maximum amplitude.
This development work formed the basis of the system that is currently used under the name "Sahara".
How does it work?
The system is inserted into a live transmission main through any tap 2" or greater in diameter and is completely safe for all potable water systems. In operation, the probe is carried along the pipe by the flow of water. The system locates leaks as small as 0.25 gallons/hr, in real time, through identification of the distinctive acoustic signals generated by leaks in the pipe wall, the joints or steel welds.
Once a leak has been detected, the sensor head can be stopped at the precise position of the leak. Its location within the main can be identified from the surface and accurately marked for subsequent excavation and repair. Consequently, operators can also use Sahara to accurately map the course of a pipeline.
Depending on the pipe configuration, lengths up to 6,000' can be surveyed with a single insertion.
Inspections can be carried out in mains with a diameter of at least 12"; there is no limit on the maximum diameter.
Sahara locates leaks through identification of the distinctive acoustic signals generated by leaks in the pipe wall, the joints or steel welds. The magnitude of the leaks is estimated by quantification of the acoustic signal recorded by the sensor.
Sahara Wastewater
Over the last 20 years inspection technologies and protocols for gravity systems have been well developed and adopted around the world. However, the same can not be said for pressurized systems. The challenge for the inspection of pressurized systems is that most inspection technologies require the line to be taken out of service. Often this is not possible due to the lack of system redundancy.
Sahara wastewater is the first service to allow utilities to assess the condition of critical wastewater forcemains and siphons, such as major non-redundant lines, waterway crossings, and lines through environmentally sensitive areas, while keeping the line in service.
A series of pilot studies conducted across North America in 2006 have been held to demonstrate that the Sahara leak detection system can be adapted to detect leaks in pressurized wastewater forcemains and siphons under typical North American operating conditions.
Sahara Wastewater can operate in most wastewater forcemains and inverted siphons. The lines must have sufficient flow speeds to pull the sensor through the line, and must have sufficient pressure to ensure that any water escaping from the pipe generates the acoustic signature recognized by the system.
System operating parameters required for
Sahara Wastewater inline surveys
For more information call:
Hugh Leavens, Marketing, at 905-624-1040 x 307
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