AE06.pdf

Applications of ultrasonic tone generator airborne

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Applications of Ultrasonic Tone Generator Airborne ultrasound emitted by an artificial ultrasonic tone generator is detected using an ultrasound detection probe. This procedure allows detection of porosity ruptures and other leaks in containers and other objects that may not be subjected to pressure. The tone generator is switched on and placed outside or inside of the test object. The ultrasound detection probe can now be used on the other side of the containment wall to detect possible leaks. It is important for the operator to keep in mind that the ultrasound is reflected by hard surfaces and could be picked up by the ultrasound detection probe indirectly. To prevent false measurements, all natural openings have to be sealed before the test. Checking for leaks of windshields, window seals on buildings and vehicles, door seals, trunk seals, pressure tanks and storage bins, hulls, 194 Acoustic Emission Testing F IGURE 13. Rubber focusing attachment. F IGURE 14. Ultrasonic tone generator. S OUND . Audible analog of ultrasonic signal.
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switching cabinets, walls, ceilings, heated pipes, refrigerator door seals and ventilation ducts are all applications using an artificial ultrasonic tone generator. Types of Portable Ultrasound Leak Detectors Portable ultrasound leak detectors are available with a variety of capabilities. For example, one manufacturer has provided the following versions: (1) a hand held, gun shaped sound probe, with earphones (Fig. 15) and sound level meter; (2) a model designed for the telephone industry for detecting leaks in pressurized cables to the exclusion of noise from wind and traffic; (3) models for vacuum and pressure leak testing; (4) a contact model for acoustically determining mechanical malfunctions such as worn shafts, bearings, engine valves, gears and hydraulic systems; (5) a model for spotting electrical leaks in power transmission systems; and (6) a tone generator to assist in locating leaks in nonpressurized areas such as the cold box of refrigerators. All of these units either detect or generate frequencies in the ultrasonic range. Control Adjustments of Ultrasound Leak Detector Instrumentation Various configurations of ultrasound leak detectors are available for numerous industrial systems and applications. The adjustable signal gate and alarm lengths can be preset for high speed production leak tests such as on aerosol packages or pressure valves. A typical example of a quality assurance program is the inspection of two-way relief valves certified for opening at pressures as low as 3.5 kPa (0.5 lb f ·in. –2 gage). A signal attenuator gives the instruments the flexibility to perform a variety of quality assurance tests. The signal required to trigger the alarm can be set to any level in an 85 dB range above inherent noise with fine attenuation continuously adjustable over a 20 dB range. Examples of the uses of this feature are the inspection of ultrahigh pressure hydraulic and pneumatic systems in which a photographic record of the intensity meter during pressure testing
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  • Fall '19
  • Acoustic Emission

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