Sonic devices

A mathematical analysis of the action in Kady and other colloid mills checks well with experimental performance [Turner and McCarthy, Am. Inst. Chem. Eng. J., 12(4), 784 (1966)], Various models of the Kady mill have been described, and capacities and costs given by Zimmerman and Lavine [Co.st Eng., 12(1), 4-8 (1967)]. Energy requirements differ so much with the materials involved that other devices are often used to obtain the same end. These include high-speed stirrers, turbine mixers, bead mills, and vibratoiy mills. In some cases, sonic devices are effec tive. 

Ultra-sonic devices 1000 Several metres < 5 cm Special devices... 

Other Transducers. Ultrasound also has been used for the measurement of force, vibration, acceleration, interface location, position changes, differentiation between the composition of differing materials, grain size in metals, and evaluation of stress and strain and elasticity in materials. Sonic devices can used to detect gas leaks, and to count discrete parts by means of an interrupted sound beam. Frequently, an ultrasonic device can be applied where photoelectric derices are used. Particularly tn situations where light-sensitive materials are being processed (hence presence of light must be avoided), ultrasonic devices may be the detectors of choice. 

Flammable or explosive volatiles may be driven out by cavitation and ignition. Virtually no sonication devices are explosion-proof and only extreme measures can render them explosion resistant. 

Each application will require different transducer properties to get the expected effect. For example, ultrasonic cleaning requires a broad uniform sound field, drills and welders require high amplitude motions, ultrasonic flowmeters utilize narrow uniform sound beams with stable amplitudes, and so on. Thus it is unlikely that one dosimetry method can be used for all types of transducers and sonic devices, a feature previously highlighted by Welkowitz [22]. 

The sonic device or horn, generally operates at an audible frequency of around 220 Hz producing a sound not unlike that of a ship s foghorn with an intensity of around 130 dB. Low frequency resonant sound in the region of 0 - 20 Hz may be used to create a sound field for the removal of soot. An example of equipment for this duty consisted of a 5 m mild steel horn with a weight of 250 Kg. An activating air supply of 300 - 1200 rri h at about 5 bar was necessary for effective operation. The cost of such equipment is usually considered to be similar to the more traditional soot blowing facilities. 

After thoroughly cleaning the specimen first with a sonic device then with an alcohol spray, and drying with forced warm air, the polished section can be examined in reflected light. An etched surface may be necessary for study with a scanning electron microscope and microprobe. 

A variety of blending techniques have been used to improve particular properties that a polymer might not possess, or are lacking. Although some of the blends were found to be immiscible, which resulted in poor mechanical properties, recent attempts to overcome this problem involved the application of ultrasound irradiation to the immiscible polymer blend pairs during melt mixing, using a mixer fitted with a sonication device. 

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