Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | JUNE 2015 | 33 In the know Digging deeper: leak detection Helium gas: the leak detective A technique for seeking out leaks in pipes using helium gas could provide utilities with a marked improvement on acoustic methods, without an interruption to supply A round 3.36BN litres of drinkable water is lost through leakage every day in the UK. These losses would be enough to supply 22.4M households, or 34% of water companies´ supply to domestic BY NICK HASKINS BUSINESS DEVELOPMENT MANAGER SUEZ ENVIRONNEMENT WATER ADVANCED SOLUTIONS UK customers. Every last drop of this precious natural resource would have previously been gathered, cleaned, treated and pumped to our homes. Leakage thus not only wastes both water and money, but can also become a public health risk if contaminants enter pipes through the opening of leaks. Where and why does this happen? Leaks can arise in several parts of the distribution system: transmission pipes, distribution pipes, service- connection pipes, joints, valves, and … re hydrants. The causes include corrosion, material defects, faulty installation, excessive water pressure, ground movement, and excessive loads and vibration from road tra‡ c. Leakage is water companies´ most frequently occurring and most resource-consuming issue, as existing prevention and treatment methods currently on the market are simply not e‰ ective enough to tackle this widespread problem. Issues with acoustic methods The most commonly used existing leakage detection tool is sound vibration. Detection crews identify the sound or vibration induced by water leaking from pressurised pipes. Leak sounds are transmitted through the pipe itself and through the surrounding soil in the immediate area of the leak. Acoustic leak-detection methods are based on the idea that if "no noise is heard, no leak exists". However, whether a leak can be "heard" depends on several factors including pipe size, type, and depth; leak size; system pressure; and interfering noise. Acoustic methods are not operational in large pipelines and large diameters due to the attenuation of leak signals in the pipe. The type of material is also crucial, because it a‰ ects the predominant frequencies of leak sounds, making them susceptible to interference with low-frequency vibrations such as pumps or road tra‡ c. Plastic pipes are characterised by relatively low noise-frequencies and amplitudes which mean it is almost impossible to accurately detect wastage with typical leak noise correlators. Detecting leaks on plastic pipes using acoustic methods is painstakingly di‡ cult. Overall, acoustic methods have only managed to reduce the amount of water lost to leakage by 8% over the past 10 years. How helium could help Suez Environnement Water Advanced Solutions (formerly known as Aqualogy) has developed A diagram of the iDROLOC process. 1 Our Technical Solution The Pipes in Service