01 July 2008
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Ultrasonic bolt meter

Measurement of the torque applied to a bolt or other threaded fastener during tightening provides sufficient feedback in most applications.

"However", says Philip Brodey, Norbar Torque Tools, "there are more specialised tasks in which measurement of the fastener tension is essential in order to ensure the integrity of a mechanical joint."

In addition, ultrasonic measurement has always been a highly skilled task requiring extensive knowledge of material properties in order to determine the correct transducer diameter, the correct transducer frequency, and the ability to interpret results.

To address these matters Norbar has launched the USM-3 ultrasonic bolt meter that offers "precise measurement of elongation and load in threaded fasteners". It also meets the skill problem as it is "an accurate, yet easy to use tool for determining fastener tension". Real-time precise bolt measurement can be accomplished in fasteners of any metal from 1 inch to over 50 feet long.

Ultrasonic measurement is based on the time-of-flight principle, explains Philip Brodey. In use, a small transducer is placed against the head or stud end of the fastener. It sends an ultrasonic sound wave through the length of the bolt. When the echo signal returns a microprocessor in the USM-3 coverts the transit time to a precise length using constants based on bolt material and digital signal. A liquid crystal display provides the results of load, elongation, and wave-form.

Author
Paul Gay

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