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Sound waves provide a reliable image of the condition of asbestos-cement pipes 

Cheaper pipe inspection can save water companies millions

20 May 2013BTO

KWR helps water companies inspect and replace water pipes cost-efficiently. If, for example, the water companies in the Netherlands all conducted acoustic inspections of their asbestos-cement pipes, this would produce a cost-saving of millions for the country as whole – even if the saving is only one euro per meter of pipe.

The Dutch water companies have 117,000 km of underground water mains. This allows them to provide drinking water of a quality and with a supply reliability unequalled in neighbouring countries. The mains network is a valuable asset: it would cost € 20 to 30 billion to replace it entirely. To maintain their excellent performance, the water companies must regularly replace sections of the network. The art is to know which mains should be given priority – for example, because their deteriorated condition. Replacement is costly, but so too is the inspection of underground mains. Sometimes “uninspected” replacement is, in the long term, the cheapest solution, even if the water company is never certain whether its expenditures are well targeted.

One euro saved per meter makes a big difference

Comparison with other methods and development of a business case

BTO, the Dutch water sector’s joint research programme in which KWR collaborates with the water companies, also includes research on suitable techniques aimed at cutting the cost of pipe inspections and limiting unnecessary replacements. Measuring sound waves in different types of mains can for instance provide valuable information about their condition. The greatest utility of this “echopulse” method seemed to be its rapid and relatively inexpensive assessment of a pipe’s condition. In 2013, echopulse is being compared in greater detail with other inspection methods and a business case is being developed.

Acoustic measurement by Echologics. At point 0 a noise is produced, which is received at points 1 and 2. Differences in the sound spectrum at 1 and 2 provide information about the average wall thickness  and therefore about the condition of the pipe section L between 1 and 2. (source: Echologics)

Acoustic measurement by Echologics. At point 0 a noise is produced, which is received at points 1 and 2. Differences in the sound spectrum at 1 and 2 provide information about the average wall thickness and therefore about the condition of the pipe section L between 1 and 2. (source: Echologics)

 

 

 

 

 

 

 

 

 

 

 

 

Inspection is more advantageous than uninspected replacement

The reliability of echopulse for the inspection of asbestos-cement pipes (30% of the distribution network) is so high, that conducting echopulse inspections, and only replacing the bad pipe sections, is a slightly cheaper option according to the business case. Moreover, a more widespread application of the method would reduce costs further. The difference between uninspected replacement and replacement following inspection amounts today to about one euro per meter of asbestos-cement pipe. That does not seem like much, but if one makes the calculation for all of the asbestos-cement mains in the Netherlands the difference amounts to € 35 million…

© 2017 KWR Watercycle Research Institute

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