ADS Environmental Services Enigma-hyQ QR 775017 A2 - Manual (Page 86)

ADS Enigma/Enigma-Compact/Enigma-hyQ User Manual
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between the arrival of the noise at A and at B. Assume the velocity of sound
is V, and the distance between the loggers is D. If the distance from X to B =
V * t, then D = (2 * L) + (V * t). Rearranging this equation provides the
distance from the logger that is closer to the leak location (L):
2
) * ( t V D
L
−
=
Based on the velocity of the sound (calculated from the pipe diameter and
material) and the distance between the loggers, the correlation software can
calculate and display the location of the leak as the direct distance from the
logger located closer to the leak.
Positioning Errors
This detection system operates effectively only when the leak exists at a
location between the two loggers. Several scenarios can hinder effective
operation.
Leak Beyond Loggers
If the leak is located outside the span of pipe between the loggers, the
correlation software will ignore the transit time from the leak to the nearest
logger, giving the impression that the leak exists at the exact location of the
logger closest to the leak (referred to as out-of-bracket). Under this condition,
the user must move one of the loggers to locate the leak position.
Leak on Connecting Pipe
If a leak exists in a pipe connecting to the pipe undergoing testing, the noise
will appear to spread from the connection point of the two pipes, falsely
indicating a leak at that point. This requires moving one logger to the
connecting pipe (to ensure the leak falls between the loggers) to accurately
locate the leak. The user must have a thorough knowledge of the entire pipe
network layout to ensure that the loggers are taking measurements on the
correct section of pipe and to eliminate the possibility of leaks on branch pipes
producing false readings.