ADS Environmental Services Enigma-hyQ QR 775017 A2 - Manual (Page 85)

ADS Enigma/Enigma-Compact/Enigma-hyQ User Manual
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C H A P T E R 7
Principles of Leak Noise Correlation
Note: ADS strongly recommends that all users read this section, even
those with prior experience in correlation techniques.
Leak Noise
The loss of water through a leak in a pipe creates a source of noise. This
noise, which travels from the leak in both directions (upstream and
downstream), is used to determine the location (or source) of the leak.
Leak Location
Leak noise correlation occurs by comparing the noise detected at two different
points in the pipeline. Noise travels from the leak in both directions along the
pipe at a constant velocity (depending on a variety of factors). Therefore, if
the leak exists at a location that is equidistant between two loggers, these
loggers will detect the noise at the same time. Conversely, if the leak exists a
location that is not equidistant between the loggers, the loggers will detect the
same noise, but at different times. The correlation software can measure this
difference in time.
For example, based on the following diagram, consider that loggers are
located on valves A and B (convenient access points for underground pipes)
and that the location of the leak is closer to A.
By the time a particular noise from the leak has reached A, the same noise
heading towards B has only travelled as far as X. The distance from X to B
causes a delay in time (t). The correlation software detects the delay t