Acoustic Leak Detection Logger: The Patrol of the Groundwater System

The “Tri-Kick-Off” Platform: Stage for Dialogues Between New Launched Sustainably Focused Projects, Citizen Backers and the Government

 

This project aims to introduce an acoustic water leakage detection method and its applications. By comparing it to the other leakage detection methods, its advantages and limitations will be discussed. Then, we will analyse its two case studies in Delhi, India and Luxemburg City. Thirdly, we will broaden the possibilities to the use of the China South–North Water Transfer Project.

 

Freshwater is one of the basic elements for human beings and at the risk of sounding grandiose, for cities, 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? InSell has been involved in market research and evaluation of acoustic based water leak solutions  developed by its solution providers.

Water management has been an integral part of Smart city Development and InSell has been working in this area not only to analyse the solutions but also has a vast experience capturing the water networking using Smallworld GIS for German cities.

In this proposal, we will focus on the smart cities’ water management, especially on the acoustic water leak detection solution. Two case studies will be introduced and analysed as a key application, and furthermore, we will try to illustrate the possibilities to use this solution for the on-going China South–North Water Transfer Project ( to be added).

 

Water Management and the Water Leak Detection System (Water LDS)

D.M. Carrey(2011) defined water management as “the activity of planning developing, distributing, managing, and optimising use of water resources, in order to minimise damages to life and property and to maximise efficient beneficial use.”

Water leak detection, as part of the water management, is working to fulfil the usage optimisation. There are different types of water detection techniques, and the choice highly depends on the operating conditions and construction materials of the pipeline. Here in this proposal, we classify all the techniques into two general types; acoustic and non-acoustic.

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.

While 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 analysing the sound data the pipeline, we are then able to distinguish whether it leaks or not and pin point the location of leakage using different equipments.

Acoustic water leak detection: The Loggers

InSell Consulting has been sharing experiences on water leak detection, together with German company F.A.S.T GmbH. The technique being used is called Acoustic Water Leak Detection.

Escaping liquids creates an acoustic signal as they passes through a hole in the pipe. When a leak occurs, a resulting low frequency acoustic signal is detected and analysed. There are two machines to finish this detection process; loggers and the receiver.

Pic1:

 

As the picture above 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.

This brings the economy of scale 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.

On top of this, a cumulative historical database can be maintained for local water leak detection. Such a database will make it possible to traceback the historical incidents, for instance, which pipeline area is the most likely one to have leak problems in future, or what is the possibility for a new pipeline to have leak problem within 5 years. And the longer the data are being recorded and database is being maintained, the more precise the detection will be.

Table 1 further explains the different operating conditions that acoustic water leak detection can be used on. 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.

First case study in Luxemburg City

After defining the acoustic water leak detection technique, we will now come to the first case study executed by FAST in Luxemburg City.

Background

Service des eaux de la Ville de Luxembourg (VDL) is the public authority with responsibility for the provision of water to Luxembourg City. It supplies 105,000 residents over an area of 51 km2 .

Although Luxembourg City is not particularly large, it poses a number of challenges for the water provider. 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,

Number of people present in the city during the day are almost double then number of people during nights.

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.

For this reason, VDL has a history of investing in technology to reduce leakages.

Execution Process

To solve this problem, Acoustic Zone Monitoring was introduced, a noise logging technology.

Loggers were directly installed onto 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. Crews can then be deployed to a specific site to investigate as appropriate.

After an initial 18 noise loggers were deployed, immediate advantages became apparent. With the success of these loggers clearly evident, VDL increased their numbers to 120. These were used on a “lift and shift” basis and moved around the different zones. The loggers were split into three groups of 40 loggers which were left for three days at a time. The recorded measurements were 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.

The number of leaks was also steadily decreasing. In 1994 prior to the introduction of the loggers 398 leaks had been recorded, in 2006 this had fallen to 84.

Results and influences

Results have been impressive with successive rounds of investment yielding a tenfold reduction in water lost through leakage from 36.6% to 3.7%.

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 positive local impacts socially and economically which have been kept out of this scope.

Second case study in Delhi, India

In Delhi, where the situation is quite special compared to the previous project in Luxemburg City. However, this pilot research project does show that acoustic water detection technique has the ability to adjust itself to suit the different cases, for instance, the noises during daytime and non-24 hours supply.

Background

Table 2 introduces the situation of the water supply system in Delhi, India.

As we can see, there is around 12,000 km of distribution pipes of which 80% are made from cast iron and a further 15% from asbestos-cement. The remaining pipes are constructed mainly of galvanized mild steel, PVC, mild steel, and pre-stressed concrete. More modern materials such as polyethylene and ductile iron are not yet in used in Delhi. The diameters of these pipes are mostly not known and they vary from section to section due to the partial replacement of old pipe sections. On average, the diameters of the distribution system in Delhi vary from 100 mm to 1,000 mm.

There is also a lack of records, as a result of very poor management and maintenance performed with limited tools, resources, and information.  The lack of information is further compounded by poor instrumentation, which even if available, is often not working properly.

To solve the water leak problems facing these challenges, solutions need to be technically adjusted its conventional acoustic method to suit the local situation.

Execution Process

Compared to the previous case study executed in Luxemburg City, the Delhi project mainly had two different situations; first, the water is not 24 hours supply, and secondly, the noise during the day time can be a huge influence of the acoustic signal.

Further possibilities exploration in China

The main problem is that china south-north water transfer project is for 24 hours per day, but it does not always pass through the urban area.

Then it is great to have a database centre to detect and control remotely.

To be continued in the next blog. Thanks for your patience.

Acoustic Leak Detection Logger: The Patrol of the Groundwater System

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