Articles & Case Studies

Seba KMT UK say listen first, dig later


Posted: Friday 23rd March 2007

Technology is one way to help manage leaks, but it is not what you do, it is the way that you use it that makes the real difference. Mike Napper of Seba KMT explains.

Leaks are something of a way of life for water companies. Unwanted, disliked and far too frequent they are part and parcel of the management and maintenance of ageing water mains networks. Life would be easier if the leaks could be detected more easily. But this is easier said than done. With something like two-thirds of leaks not reaching the surface and the industry and its supply chain struggling to determine the best way to locate leaks, water companies and contractors are obliged to manage the best they can with the current tools and systems.

The knock on effect of this is more holes in the UK’s roads. Better application of more accurate location systems will in turn make site assessment easier, which can also have a positive impact on the wider use of no-dig techniques. This will speed up the repair and renewal process for the water companies and maintain better relations with the highways authorities.

Certain situations highlight the difficulties water companies face. A team from Seven Trent were trying to locate the specific location of a leak from an eight inch cast iron main that ran beneath the A45 Coventry by-pass. They had tried to locate the pipe itself using cable avoidance tools in a passive mode, but this gave the wrong position. They knew the approximate location, but had to be accurate as making an exploratory excavation required closing the nearside lane of the dual carriageway. Matt Clarke, a product specialist with Seba KMT, explains what happened next.

“We work in a framework with STW, helping each other develop systems and testing some of our products. They asked me to try and locate this leak to avoid digging any dry-holes. Having agreed with the team that the leak was not where they thought it was we used a tri-frequency locator and we quickly identified not just the location but also the depth of the water main. It was about four metres away from the planned exploratory excavation.”

The senior STW team assessed the findings and then using a digital correlator, the leak itself was pinpointed – six metres away from the planned hole. So, work commenced in the outside lane and two blow holes were found and two metres of pipe replaced.

Seba KMT, like other suppliers, works closely with water companies. It is important to be able to demonstrate the technology and the techniques in real world situations so that the customers can see the benefits for themselves and have real proof the kit does what it says on the tin.

“Working closely with Seba KMT gave the STW team access to our support and advice as well as the chance to see the latest and most appropriate equipment in action,” explains Matt Clarke. “In this case an unnecessary excavation was avoided, which saved a lot of money and made the site assessment itself by the senior team a lot simpler and also helped to speed up the repair process.”

Using a combination of detection equipment is the best solution – it is always best to double check the findings. For example, at the A45 using a cable avoidance tools was not adequate for the precise location of the specific service. It is important to understand the propagation of sound frequencies within a water network and the effect of different materials upon this. This gives the best chance of removing unwanted sounds detected by leak location equipment.

Engineers might use listening sticks – essentially an ash, beech or steel rod with an ear “cup” – to identify a leak, just by listening for the sound of water. Less experienced employees might use an electronic listening stick. Severn Trent use noise loggers supplied by Seba KMT. This is a device that listens for the amplitude and frequency, or the tone, of noise coming from a leak. It gives their team accurate readings to help avoid unnecessary digging.

The STW team will use a combination of logger, correlator and cable avoidance tools to pinpoint the leak. After all, nobody, including the public and the local authorities that grant access to the water companies and contractors, like to see needless dry-holes in the highway. Knowing exactly where the leak is speeds up the site assessment process allowing the team to make a decision about the best way to rehabilitate the pipe. So, if the technical kit is applied correctly, using a combination of detection equipment such as correlators, cable avoidance tools and loggers, the rate that leaks can be located should improve and the overall performance of contractors and utilities can be enhanced.

Seba KMT UK is demonstrating the new Correlux P-200 correlator and Easyloc as well as its other products at stand N90 at IWEX, as part of Sustainability Live at the NEC, 1-3 May, 2007 and then also at SED, 22-24 May on stand 52 in the Pavilion at SED.

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