Description
Around a world a large volume of potable water is lost every year from leaks in water distributions networks. Such leaks may go undetected for a long time. When water leaks are suspected to occur from a distribution network, it is usually necessary to appoint a specialist contractor to locate the leak(s), who may use a range of technologies for this purpose. However, all these technologies require the contractor to search for the leak.
A passive means of leak detection can be achieved by burying a suitable fibre optic cable with a new water pipe upon installation. A water leak can affect the optical fibre in three ways. Firstly, the leaking of usually colder water into the ground results in a temperature change around the leak location. Secondly, water leaks affect the pore pressure in the ground, changing the effective stress, causing a degree of ground deformation which, in turn, deforms a fibre optic cable passing through the ground. A third effect may occur when the leak causes soil erosion, resulting in significant straining of the cable. Fibre optic leak detection on pipelines is especially effective in unsaturated soils, which typically experience significant pore water suctions in its in situ state. Changing these suctions due to a leak, results in significant deformation.
Brillouin frequency shift in optical fibres is sensitive to changes in both temperature and mechanical strain, allowing fibres to act as efficient leak detection sensors. Purpose-made fibre optical cable may be expensive, but telecommunication grade cables generally have a low cost and area readily available around the world. This paper will demonstrate the performance of a range of fibre optic cables, including communication grade fibre optic cables, to act as leak detection sensors in the ground.
