Leak detection is elementry

Radcom Technologies explains how its new Soundsens system can improve and simplify leak location by combining noise logging and leak noise correlation in a single process.

The water industry in England and Wales is giving itself a well-earned pat on the back. With leakage reduced by 37%, enough to supply 12.5M people, things have come a long way since the 'dark days' of the early 1990s.

Add to this Ofwat's softening view of the need for mandatory leakage targets for most companies and some might say that perhaps the pat on the back is being prematurely delivered.

Decade of change
At least one long-standing issue of consensus remains constant - waste is a bad thing. Whether the waste is water leaking into the ground or money spent on locating difficult to find leaks, depends on your perspective. Whatever your point of view, there is no doubt that the science of leakage management has substantially improved in the last decade. Since privatisation, the creation of thousands of DMAs has enabled water companies to handle network losses in manageable chunks. In parallel with this, leakage detection and location technologies have developed rapidly.

In the mid-1990s a water company facing a large disparity between its reported leakage and its target might have contemplated region-wide deployment of noise loggers, devices that register noise anomalies in pipes and thus give an indication of local leakage. However, such a scatter-gun approach would be considered overkill today.

So where are we with leakage detection technology? Most water companies no longer routinely carry out step-testing, the process of systematically closing distribution valves to localise a leak, thanks, in part, to the targeted rather than widespread use of noise loggers. They are a powerful tool, but do not do enough to complete the job. Correlation teams are still required in most companies to convert a localised leak into a pinpointed leak. Thus there is a three-step process employed by most water companies. Firstly, an increase in minimum night flow is detected by a DMA flow data logger, which probably indicates the presence of a leak. Next, the leak is localised to an area using noise loggers. Last, a specialist team travels to the area to accurately pinpoint the location of the leak using a conventional correlator system.

Although this approach works, its efficiency is limited by two factors. The first of these is that many water companies have struggled to fully justify the cost of adding telemetry to network data loggers. Using lower cost data loggers, which have to be manually downloaded, results in a significant time delay between when the burst occurs and when the data from the relevant logger is collected and analysed. Secondly, there is an additional delay between the deployment/collection of noise loggers and the arrival of the correlator team. This is further exacerbated in some companies because the noise logger activities and the correlator activities have been outsourced to separate, often competing, contractors.

One of the equipment suppliers to the leakage industry, Radcom Technologies, suggests that there is a way to substantially improve the efficiency of the process. Radcom was one of the companies that pioneered DMA monitoring and network data logging in the 1980s, and is now keen to extend its role in leakage management to encompass detection and pinpointing as well.

Simply better
Radcom believes the current method of leak location can be radically improved and simplified by combining noise logging and leak noise correlation into a single process.

The system developed for this process, Soundsens, is already in use at many water companies and is being trialled at several others.

Dr Gurch Chana, technical director and co-founder of Radcom described the system. "The Soundsens approach is based on the deployment of highly sensitive and accurate loggers, called 'pods'. The pods, which are time synchronised, record sound in short bursts lasting a few seconds. The recording is repeated multiple times to separate genuine use from suspected leakage." The duration of recording, the number of recordings and the dwell time between each recording is programmable and depends upon the pipe material in question, whether the test is taking place during the day or at night and whether the pipework being tested is a trunk or distribution main.

The pods have at their heart an advanced digitally amplified accelerometer, developed in conjunction with Southampton University, which is capable of detecting lower levels of sound than can be expected from conventional designs, which simply correlate sound velocity between two points.

However, the company claims that the key aspect of Soundsens is the way that the data recorded by the pods is then handled, as Chana continued, "The data from each pod is transferred to a laptop, where a layout of the pipework is graphically drawn using either GIS data or as a simple sketch. The layout enables the software to both link and take into account the spatial relationship between the pods."

Once the layout is complete, the software uses proprietary algorithms to amplify the sound and filter out anomalies. Correlation takes place between each pod in the array and all of the others. The company says that this process, called cross-correlation, is unique to the Soundsens system and enables greater certainty in pin-pointing leaks as it discerns leak noise profiles from other water sounds.

Any leaks are pin-pointed on the pipe layout diagram, tabulated and ranked in order of probability. The software will also show any correlations that should be subjected to further investigation. To help with this, the operator can listen to the sound using the software's audio feature. The data files can then be stored for transfer or use at a later date.

The system has already won plaudits. At the IWEX 2001 Innovations Awards, Soundsens received the highly commended accolade in the measurement and instrumentation category.

Water companies using Soundsens are reportedly having success with the system in situations that would normally be difficult for leak noise correlators. In particular, Soundsens has recently found leaks on trunk mains in the Wessex Water region and on long length MDPE distribution mains in the Anglian Water region.

Technology alone cannot answer all of the water industry's questions about leakage. However, developments that improve efficiency and save time and money will help to reduce water loss and go some way to reducing leakage, even if the remaining questions mean that such a reduction is measured in relative rather than absolute terms



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