ULTRASONIC MEASUREMENT ENSURES MECHANICAL JOINT INTEGRITY

Although measurement of the torque applied to a bolt or other threaded fastener during tightening provides sufficient feedback in most applications, there are more specialised tasks where measurement of the fastener tension is essential to ensure the integrity of the mechanical joint. To address this requirement, Norbar has introduced the USM-3 ultrasonic bolt meter – a compact, lightweight, field-portable unit that gives precise measurement of elongation and load in threaded fasteners.

Traditionally, ultrasonic measurement has been a highly skilled task, requiring extensive knowledge of material properties to determine the correct transducer diameter, the correct transducer frequency, and to interpret the results. The USM-3 overcomes all of these challenges, and gives the operator a highly accurate yet easy-to-use tool for determining the tension in a fastener. 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. In use, a small transducer placed against the head or stud end of the fastener sends an ultrasonic sound wave through the length of the bolt. When the echo signal returns, the microprocessor in the USM-3 converts the transit time to a precise length, using constants based on the bolt material, and digital signal.