Superior Signal Company LLC
AccuTrak
®
VPE-
1000 User’s Manual
© 2015
7
Principle of Operation
The principle of operation of the AccuTrak
®
is based on the turbulent flow of fluids and
gasses. Turbulent flow has a high content of ultrasound. This is sound which is above
the human hearing range, but can be heard with the AccuTrak
®
, and traced to its
source.
Imagine air leaking from a tire. Because this is such a
large
leak, your ear
can
detect
this sound, however your ear hears only about 1/3 of the actual spectrum of sound
which exists. The sound of small leaks is mostly ultrasonic which your ear can
not
detect.
It is important to remember this example:
A piece of straight tubing
connected to a gas supply and left free to exhaust into the atmosphere will
not generate sound if the volume of gas through it is such that turbulence
does not take place. Yet for that same flow, an opening as small as 0.005
of an inch could generate enough sound to be heard several feet away.
For a leak to happen there must be an opening in the system that carries a gas or fluid.
Normally, these openings are not clean smooth holes, but passages through cracks with
many jagged edges and internal chambers. Fluid or gas escaping through an "orifice"
like this, is forced into turbulence, random circular-like motions. Inside a tube where a
gas may be flowing, the flow is normally laminar which means that a given layer of gas
does not mix with layers above it or below it. This condition happens in a straight long
tube when the velocity of the fluid is not high. A gas leaking out of a straight and long
tube will not generate as much sound as if it were leaking out of a small crack because
the flow is not turbulent.
The intensity of sound generated at a leak is a very complex function of the viscosity,
the temperature, the speed the fluid is moving, the Reynolds number, the pressure
differential across the leak and the physical dimensions and characteristics of the orifice.
This is why it is possible for a smaller leak to generate more sound than a larger one.
What this all means...
The AccuTrak
®
detects ultrasound NOT refrigerant or the presence of a specific gas. It
is NOT a sniffer. Because of this fact, the AccuTrak
®
can function in areas where heavy
wind or a concentration of fumes renders other detectors useless.
Because of the unique touch probe system in the VPE-1000, it can also be used to
detect turbulent internal flow in situations such as leaks in valves, steam traps, and
pump cavitation.
WARNING
Ultrasonic detectors will not indicate a leak if there is no turbulent flow producing sound
when you check it. If you suspect a
toxic gas, natural gas
, or other
combustible gas
leak
, and do not detect it with the AccuTrak
®
, do not assume that it does not exist as it
may not be turbulent. Use another method as verification that there is no leaking gas
present.
