Articles & Case Studies

Trunk main leaks find it harder to hide!

Posted: Thursday 15th January 2009

Primayer’s Enigma system is enabling the location of leaks where never previously felt possible, often with the successful correlation over an incredible distance. This new level of performance is now enabling efficient management of leakage and reduced risk of failure on one of the most critical elements of a water network, the trunk mains!

Leak detection on trunk mains using correlation techniques has always been viewed as being of potentially limited success for the basic reasons of poor sound propagation, scarcity of accessible fittings and limited signal recording and process capabilities. However, the new digital noise correlation and signal coherence frequency analysis processing, within Enigma technology, has overcome many of these problems and increased performance dramatically.

One excellent example can be found in Slovakia. The Bratislava Water Company (BVS) purchased two Enigma systems for preventive leak detection in rural areas. Having now used the systems for over a year, they have found over 160 leaks, even finding 6 leaks in one deployment.

In particular, BVS had a suspected leak on an important 300mm diameter cast iron main but there was no indication of where the leak might be and the distance between fittings was considerable. The leak was found due to systematic Enigma deployment along the trunk main. Four access points onto the main were available. Accelerometer sensors were used as hydrophone access was not available. Sound information was collected on Enigma loggers and then data transferred to a PC for post processing.

The raw data provided a strong and conclusive correlation result between the two closest loggers over 1455 metres, without any additional post processing. Additional post processing also revealed that correlation was possible between two of the loggers over the much greater distance of 2615 metres! Even over such long distances the result was accurate. The leak was located and repaired saving approximately 1.5 litres/second and reducing the subsequent risk of main failure.

These exceptional results are based on using Enigma accelerometer sensors only (sensors attached to the external fittings of the mains). If hydrophones were employed (acoustic sensors fitted into the water) even greater correlation distances would expect to be achieved with Primayer’s Enigma.

More information is available from Steve France at Primayer on +44 (0)23 9225 2228 or sales@primayer.co.uk




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