kejuruteraan bekalan air & air sisa

POLITEKNIK SULTAN SALAHUDDIN ABDUL AZIZ SHAHKEJURUTERAAN BEKALAN AIR & AIR SISA | C5305

1

Index

No. Contents Page

1 Index 1

2 Introduction 2

3 Leak Noise Sounding Corelator 3

4 Conclusion 8

5 Reference 9

6 Appendix 10


2

Introduction

Leak correlators require accurate information on the materials in which the leak sound

is traveling in order to do an accurate correlation. The user normally has to input the size and

type of pipe as well as the distances of the loggers from each other. Many standard pipe sizes

have known speeds of sound which can be used for the correlation calculation. If the materials

are unknown, the speed of sound through the materials will have to be calculated on site to get

an accurate leak correlation. Most correlators can also analyze the sound levels and sound

frequencies to determine other information about the leak such as the size and severity of the

leak or whether it's on the pipe, a valve or hydrant, or in a service line. Most leak correlators

serve two major purposes. First to detect the presence of a leak, second to pinpoint the

location of the leak for repair when detected.


3

Leak Noise Sounding Corelator

A leak in a pipe under pressure creates noise that travels through the pipe walls. The

noise is detected at two separate points, (water valves, hydrants, meters) by highly sensitive

microphones. The leak noise takes longer to travel to the microphone furthest from the

source.

A leak noise correlator is an electronic device used for Leak Detection and as a leak

locator to find leaks in pressurized water lines. ALM leak Detection uses a

surface microphone, a computer leak correlator sound sensor, and accelerometers that are

placed at two or more places in contact with the pipe to detect and record sound emitted by

leaks. The sound data is processed through a mathematical algorithm which compares or

correlates the speed of sound that the leak noise travels from the point of the leak to each of

the sensors. The correlation can then be used to determine the location of the leak.


4

Water Leaks Create Different Sounds.

Water leaking from an underground pipe normally generates an audible sound due to the

water pressure. This leakage sound contains four elements:

Water flow sound

Impact sound

Friction sound of the water against the pipe

Pipe vibration sound

Sounds from water leaks: transmission through pipe walls and soil, factors that impact sound

transmission

Water Leaks create different sounds. Higher Frequencies are More

Attenuated (Absorbed) in Soil than

Lower Frequencies.

Sound Intensity Increases with Various Pipe Materials Transmit Sound

Water Pressure. Differently.


5

What Affects Leak Sounds & Our Ability to hear them.

Water Pressure in Pipe

Type of pipe material and pipe diameter

Soil Type and Soil Compaction

Ground Surface for microphone: concrete versus sod

Extraneous noises: wind, highways, buildings, machinery

Water Leak Surveys and Water Leak Pinpointing.

1. Water Leak Surveys

Listen at hydrants, Valves, meters, curb stops, and other exposed sections / fittings.

No sounds at all: then no leak nearby.

2. Water Leak Pinpointing

Only after performing surveys.

Between two loudest fittings (hydrants, meters, etc.)

Directly over top of line.

LEAK SURVEY at Meters Water Leak Pinpointing


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What are Sounds of Leaks Like?

1. Good water pressure, crop leak or small leak: "hiss".

2. Good water pressure, main break or big leak: "whoosh".

3. Very close to leak (15-20 feet during pinpointing): rapid "thumping" noises of water

against soil in cavity or "clink, clink" of small stones bouncing off pipe.

4. Water splashing on the pipe: may be close to leak or may be water traveling along

pipe for long distance.

5. Pipe resonance noises (i.e., "hiss" or "whoosh"); always very constant.

6. Intermittent and on again / off again noises: not a leak.

7. "um and ringing”: transformers, motors, or gas lines.

8. "Click, click, click”: meter turning (not a leak).

Advantage of an Accoustic Leak Detector.

1. Not too expensive.

2. Maintenance free and pretty reliable (Don't drop the sensor!).

3. Pretty easy to operate.

4. Can be used inside of buildings for leaks inside of walls and under floors (turn off

HVAC system and other building noises).

5. Almost never wrong: where leak is loudest is almost always where leak is located.

6. Last for many years: 10-15 years life expectancy.

Disadvantage of Accoustic Leak Detector.

1. Practice required to lean leak sounds and techniques.

2. Maximum depth for pinpointing: 1 to 1.5m for pinpointing.

3. Pinpointing over soft or grass cover more difficult.

4. Pinpointing is sometimes possible only at night.


7

Water Leak Surveys: How to do them?

For most complete surveys, listen at EVERY curb stop, meter, hydrant, valve, etc.

For iron and steel lines, listen at hydrants or Meters every 100 to 200m.

For AC pipe, listen at hydrants and at a curb stop/meter between them (max distance

between points: 100m).

For 13mm to 150mm PVC pipe, (Max distance between points 150m).

For 150mm and larger PVC pipe, (Max distance between points 100m).

When listening at curb stops/meter boxes, pick side of street with shorter length

services.

No Leak Sounds? Then, No Leak nearby.

Water Leak Pinpointing: How to do it.

Only after performing surveys.

Between two loudest fittings (hydrants, meters, etc.).

Directly over top of line.

Listening at Meter by FSB-8D.


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Conclusion

Simply throwing resources at issues such as pressure management and active leak

control is one way of improving those aspects of water loss management, however such a

brute force effort is always going to be limited in its scope for effectiveness, and even more

limited in its efficiency. Gathering information is the first step in identifying how any

problems can be best resolved, before the best approach to tackle them can be chosen.

Training and information sharing at all levels of service is essential to achieving success, and

personal experience is still invaluable to a leakage engineer, but the use of up-to-date

technology and methodology can ease the entire process. When time and resources have gone

into building an effective system – any system – those investments are saved many times over

when the system is implemented. This is particularly evident in largely automated (typically

computerised) systems, where the burden of processing is placed with devices specially

designed to do them. By separating and specialising responsibilities not just between people

but also by sharing them with technological systems, each aspect becomes more efficient –

and the whole benefits greatly as a result.


9

Reference

http://en.wikipedia.org/wiki/Leak_noise_correlator

http://www.almleakdetection.net/water-main-leak-detection.html

http://www.fujitecom.com/howto/Howtofindleaks.html

http://www.fujitecom.com/howto/FSB8D.html

http://halmapr.com/news/hwm/water-lost-is-water-wasted-%E2%80%93-working-with-the-

water-loss-task-force/

http://halmapr.com/news/hwm/water-lost-is-water-wasted-%E2%80%93-working-with-the-water-loss-task-force/

http://halmapr.com/news/hwm/water-lost-is-water-wasted-%E2%80%93-working-with-the-water-loss-task-force/

http://www.fujitecom.com/howto/FSB8D.html

http://www.fujitecom.com/howto/Howtofindleaks.html

http://www.almleakdetection.net/water-main-leak-detection.html

http://en.wikipedia.org/wiki/Leak_noise_correlator


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Appendix

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