Water Management through Acoustic Leak Detection Logger
Water management has been an integral part of the smart city development and InSell, with its experience has been working in this area not only analyzing solutions but also capturing the water networking through Smallworld GIS technology for German cities.
Freshwater is one of the basic elements for human beings and water pipelines can be viewed as their lifeline to some extent. However, these water pipelines are prone to leakage due to various reasons. This poses new challenges to the water supply system which has already been a challenging issue for cities and concerned authorities. How to solve this leak problem? Who can be trusted to act as a patrol recording and reporting the real-time data of the groundwater?
D.M. Carrey (2011) defined water management as „the activity of planning developing, distributing, managing, and optimizing the use of water resources, in order to minimize damages to life and property and to maximize efficient beneficial use.“ Water leak detection, as part of the water management, is working to fulfill the usage optimization. There are different types of water detection techniques, and the choice highly depends on the operating conditions and construction materials of the pipeline. All techniques are classified into two general types: acoustic and non-acoustic.
Non-acoustic water leak detection
Non-acoustic water leak detection solutions are normally model base, including pressure/flow monitoring, balancing methods, and RTTM methods (Real-Time Transient Model). These non-acoustic methods record the mass flow, pressure, density, and temperature into a database, and based on it, they build models to test the possible leaking level.
Acoustic water leak detection
Acoustic water leak detection works based on the different level of noise created from the supply pipeline. When leakage occurs, the water floods out from the leaking point and as a result, a relatively high noise level can be recorded. By analyzing the sound data of the pipeline, it is able to distinguish whether there are leaks or not and pinpoint the location of leakage using different equipment.
Escaping liquids create an acoustic signal as they passs through a hole in the pipe. When a leak occurs, a resulting low-frequency acoustic signal is detected and analyzed. There are two machines to finish this detection process; loggers and the receiver.
The Loggers and the Receiver
As Picture 1 shows, the loggers need to be put directly along the pipe, and when the receiver is coming close to the logger, it will receive the signal with information automatically. The signal inside the receiver can be stored and later be output into a database for the local area. In other words, to test the water leak situation, we need to install a specific number of loggers depending on the area, but only one receiver is required.
Picture 1: Flow of information from loggers to the database
A cumulative historical database can be maintained for local water leak detection. Such a database will make it possible to trace back the historical incidents, for instance, which pipeline area is the most likely to have leak problems in future, or what is the possibility for a new pipeline to have leak problem within 5 years for example. And the longer the data are being recorded and the database is being maintained, the more precise the detection will be.
Table 1 further explains the different operating conditions for acoustic water leak detection usage. Acoustic water leak detection is mainly designed for the 24 hours water supply, however, it can also be adjusted and then used for intermittent water supply. As for the material requirements of the pipeline, acoustic leak detection is only suitable for metal pipes, but not plastics ones.
Table 1: Acoustic Leak Detection Application Types
Economically speaking, economy of scale is present into the acoustic water leak detection system. As when the area of the leakage is getting bigger, the cost of the complete set is not increasing, instead, the quantity-price line will bend down.
A case study in Luxemburg City
Service des Eaux de la Ville de Luxembourg (VDL) is the public authority responsible for the provision of water to Luxembourg City. It supplies 105,000 residents over an area of 51 km2. Most of the water is supplied from local springs which can provide up to 60% of requirements. The remainder must be purchased in from a third party, which is more expensive. This makes the cost of lost water through leakages very apparent. Although Luxembourg City is not particularly large, it poses a number of challenges for the water provider. That is because the city layout is complex, as it straddles hills and drops into two gorges. The water infrastructure must cope with elevation changes of over 100 meters. Additionally, the number of people present in the city during the day is almost twice the number of people during the night. For this reason, VDL has a history of investing in technology to reduce leakages.
To solve this problem, the Acoustic Zone Monitoring was introduced. Loggers were directly installed into pipes, valves or fittings. By comparing over time minimum noise levels during periods of usage, it is possible to determine the likelihood of a leak.
An initial 18 noise loggers were deployed and immediate advantages became apparent. The success of these loggers clearly evident, thus VDL increased their numbers to 120. These were used on a “lift and shift” basis and moved around the different zones. In parallel, the recorded data was saved which enabled comparisons over time. With the introduction of these additional loggers, the time taken to find and repair a leak reduced from a month to a week
Results and influences
As for the influences, firstly, passive monitoring ensured the infrastructure was not being put under any additional stress and so new leaks were not being introduced. Secondly, the data collected gave a more accurate indication of the leak location. Consequently, repairs were quicker and the manpower required to conduct the leak surveys was less. There are other socially and economically positive local impacts which have been kept out of this scope.
Results have been impressive with successive rounds of investment yielding a tenfold reduction in water lost through leakage from 36.6% to 3.7%. In 1994 prior to the introduction of the loggers, 398 leaks had been recorded, in 2006 this had fallen to 84.
InSell represents the complete range of services associated with innovative Leak Detection Systems. It has been sharing experiences on water leak detection, together with German company F.A.S.T GmbH. The services broadly cover zone measurement using immobile or mobile meters and locate leaks with the help of acoustic water leak technology. The whole leak detection system is integrated with the GIS system in order to develop further applications for better water management in cities.