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Ultraprobe Applications
Leak Detection
This section will cover airborne leak detection of pressure and vacuum systems. (For information
concerned 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., helium). The
Ultraprobe can sense any type of gas leak since it detects the ultrasound produced by the turbulence of a
leak. because of its versatility, the Ultraprobe may be utilized in a wide variety of leak detection. 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.
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