Digging Deeper: Helium gas for leak detection
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
by Nick Haskins, Business Development Manager, Suez Environnement Water Advanced Solutions UK
Around 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 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 fire hydrants. The causes include corrosion, material defects, faulty installation, excessive water pressure, ground movement, and excessive loads and vibration from road traffic. 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 effective 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 affects the predominant frequencies of leak sounds, making them susceptible to interference with low-frequency vibrations such as pumps or road traffic. 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 difficult. 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 an innovative leakage solution that offers a more precise and effective alternative to conventional acoustic methods. iDROLOC detects water leaks in both long-distance, large-diameter pipelines and in small distribution pipes and connections, where acoustic systems are not a feasible option. The new technology substitutes sound waves for helium gas. It operates on the basis of two premises: that helium is lighter than air, therefore it tends to rise naturally to the surface; and that the helium concentration in the earth’s atmosphere has a constant value. These two principles make helium gas a unique tool to detect leakages in pipes.
The system is able to trace leaks with no interference to noise vibrations. Furthermore, it is also suitable for any kind of pressure condition. This means that when iDROLOC is operating, the pipes can remain in service throughout the process, without the need for any preparatory operations such as closing valves or modifying pumps; the final consumers are therefore the ones who benefit the most from its implementation.
In 2009, Suez Environnement Water Advanced Solutions began working hard to design a tool for inspecting leakages in large diameter pipes. At that time, the market offered other tracer gases as an alternative to acoustic methods, but these gases always meant having to put pipelines off-line, implying long interruptions
to the water service.
Engineers at Suez Environnement Water Advanced Solutions realized that helium’s qualities could be very valuable when applied to tracer-gas techniques. They would not require cutting the water service. After several trials, the first pilot was carried out in 2010 in Alicante, Spain. The results were promising and, months later, Jeddah in Saudi Arabia became the first international city to take advantage of iDROLOC’s benefits. Many countries around the world are now using it for detecting leaks, including Spain, the USA, France, Mexico and Colombia. It has yet to be used in the UK, although Drinking Water Inspectorate (DWI) regulations do allow for the injecting of helium into the main drinking water network, in service, to pinpoint leaks.
How iDROLOC works
iDROLOC operates through two main phases: injection and aspiration. A stainless-steel injection kit ensures that liquid helium is correctly inserted upstream of the section to be inspected. This system calculates the amount of gas needed, depending on the water volume and pressure. The helium is absorbed by the water, which transports it at a uniform concentration. It flows through the pipes without causing contamination or affecting the water’s smell and taste.
Helium releases naturally from the water as a gas, and rises because it is lighter than air, making it easy to detect in the subsoil. If there is a leak, the helium will be released from the water, which soaks through the soil.
A robot works continuously and takes samples every three metres to detect even the smallest leak. It drills a hole in the area selected and a series of suction cups extract air from the sub-soil. The gas analyser examines the air, looking for the presence of helium. As the concentration of helium in the atmosphere is stable, any increase indicates an anomaly that iDROLOC pinpoints as a problem area. This detection stage can be carried out for up to five days as the helium is retained in the soil for this period.
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