FEATURES 25 acoustic detection has advanced , but it still relies on listening for that sound , taking note of where it is located and then proceeding with the repair .
A listening device ’ s resonance plate is held up against a wall , for example , while the plumber listens for the leak through the headphones . This essentially makes the resonance plate or microphone a leak detector ’ s stethoscope . The sensitive device picks up the sound of the leak and provides an approximation of its location .
Leak detection using gas goes together with acoustic testing . A special gas mix is used under these circumstances , usually 95 % nitrogen and 5 % hydrogen . The gases must be carefully measured out as the wrong combination of the two could result in an explosion .
The pipeline is pumped with the gas and a device is used to “ sniff out ” where the gas escapes through the ground or floor . These technological noses , depending on the instrument , can even provide readings and sound an alarm when the gas has been detected . This is a method utilised mostly outdoors and can even be used to detect leaks in swimming pools .
Using visual means in conjunction with acoustic and gas testing will create a data map that will indicate the area of any leak sounds . Correlation helps pinpoint the leak location .
3 . Correlation Correlation helps identify the area in which the leak may be located . One radio receiver is connected to a valve , whilst the other is connected to another valve . Information about the kind of material the pipe is made from , the kind of liquid or gas in the pipe and the material of the wall or concrete is important to factor in , and devices will allow you to add this information in so that it can calculate the location more accurately .
A ground microphone is used to listen to the sounds emanating from the ground , helping the leak detector confirm the location of the leak . It could even be possible to place hydrophones into the water system for the same purpose . These hydrophones would act as in-water listening devices .
However , when it comes to noisy environments such as office blocks or neighbourhoods , leak detection may pose a problem .
4 . Sound Sensing Noise loggers are used in sound sensing . They are placed over a larger area – for example a neighbourhood . These loggers are placed on valves and hydrants about 25m to 100m apart . They are switched on at a specific time , usually in the early hours of the morning when there is less noise , giving the sensors on the loggers a chance to pick up the location of the possible leak .
Loggers are performing stage acoustic in busy and larger scale areas . A CBD can be too busy to hear leak sounds , so the loggers are used during the night . In theory , a city could put
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An acoustic testing listening device .
loggers on an entire network that log it constantly . A dedicated team could patrol the city , collect the data from the loggers and review it on an area-to-area basis . This could provide vital information regarding leaks that could occur , which means that a repair team can be dispatched before any serious damage is done . These could possibly be linked via wi-fi to provide real time information in a smart city .
5 . Step Testing Step testing is no longer used in the domestic setting as there are other methods available that are far less invasive for those jobs . Step testing involves shutting off the water supply of entire neighbourhoods while attempts are made to locate possible leaks . The flow and water pressure are monitored from a single point of municipal water supply .
Valves are shut off one at a time and readings are taken . It is a long , laborious process that follows the water flow and pressure along an extensive network of pipes and is often performed by municipalities of operators contracted to the municipality . This process can be done using ultrasonic measurements . An ultrasonic flow meter on a pipe measures the flow of water and reports data back , assisting in leak location .
There are two other leak detection methods worth mentioning , although these would be employed for larger scale industrial and municipal work . In camera leak detection , a tethered camera is inserted into the pipeline . An operator then watches a screen to look and listen for leaks .
Satellite detection is also used for bulk networks – and it is the same technology deployed to find water on Mars . This method works well
November 2023 Volume 29 I Number 9
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