Robinair 16455 TruTrack Ultrasonic Leak Detector - Manual (Page 5)

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Theory of Operation
The theory of operation of the TruTrack Ultrasonic Leak Detector is
based on the turbulent flow of fluids and gases. Turbulent flow has a high
content of ultrasound, which is above human hearing range but can be
heard by TruTrack and traced to its source.
Turbulence must occur for a leak to be detected. If a straight piece of
tubing is connected to a gas supply and left free to exhaust into the
atmosphere, it will not generate any sound if the volume of gas moving
through it is too gentle for turbulence to take place. Normally, at the leak
site, there will be holes and / or cracks that are jagged and have odd,
internal chambers. Fluids or gases escaping through openings like this
are forced into turbulence—random circular-like motions.
The intensity of sound generated at a leak is a complex combination
of the viscosity, temperature, speed the fluid is moving, Raynolds
number, pressure differential across the leak, and physical dimensions
and characteristics of the crack or hole. Because of these variables, it is
possible for a smaller leak to generate more sound than a larger one.
WARNING
Ultrasonic detectors do not indicate a leak
if there is no turbulent flow producing
soundwaves. If you suspect a toxic gas,
natural gas, or other combustible gas leak, but
do not detect it with the TruTrack Ultrasonic Leak
Detector, DO NOT ASSUME that a leak does not
exist. To prevent personal injury, use another
method of verification to ensure no dangerous
gases are present.
Introduction