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Ultraprobe applications
Leak detection
This section will cover airborne leak detection of pressure and vacuum systems. (For information con-
cerned with internal leaks such as in Valves and Steam Traps, refer to the appropriate sections).
What produces ultrasound in a leak? When a gas passes through a restricted orifice under pressure, it is
going from a pressurized laminar flow to low pressure turbulent flow (Fig. 1). The turbulence generates a
broad spectrum of sound called "white noise". There are ultrasonic components in this white noise. Since
the ultrasound will be loudest by the leak site, the detection of these signals is usually quite simple.
Figure 1: Pressure Leak
Figure 2: Vacuum Leak
A leak can be in a pressurized system or in a vacuum system. In both instances, the ultrasound will be
produced in the manner described above.
The only difference between the two is that a vacuum leak will usually generate less ultrasonic
amplitude than a pressure leak of the same flow rate. The reason for this is that the turbulence
produced by a vacuum leak is occurring within the vacuum chamber while the turbulence of a
pressure leak is generated in the atmosphere (Fig.2).
What type of gas leak will be detected ultrasonically? Generally any gas, including air, will produce a
turbulence when it escapes through a restricted orifice. Unlike gas specific sensors, the Ultraprobe is
sound specific. A gas specific sensor is limited to the particular gas it was designed to sense (e.g., heli-
um). The Ultraprobe can sense any type of gas leak since it detects the ultrasound produced by the tur-
bulence of a leak. Because of its versatility, the Ultraprobe may be utilized in a wide variety of leak de-
tection. Pneumatic systems may be checked, pressurized cables, such as those utilized by telephone
companies, may be tested. Air brake systems on railroad cars, trucks, and buses may be checked.
Tanks, pipes, housings, casings and tubes are easily tested for leakage by pressurizing them. Vacuum
systems, turbine exhausts, vacuum chambers, material handling systems,
condensers, oxygen systems can all easily be tested for leakage by listening for the turbulence of the
leak.
How to locate leaks
1. Use the SCANNING MODULE.
2. Start off with the sensitivity selection at 70 (Maximum).
3. Begin to scan by pointing the module towards the test area. The procedure is to go from the
"gross" to the "fine" more and more subtle adjustments will be made as the leak is
approached.
4. If there is too much ultrasound in the area, reduce the sensitivity setting and continue to scan.
5. If it is difficult to isolate the leak due to competing ultrasound, place the RUBBER FOCUSING
6. PROBE over the scanning module and proceed to scan the test area.
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