Ultrasonic bolt meter demonstrates real time measurement capabilities

The company's bolt meter is designed to provide precise measurements for the elongation (resolution to 0.0001mm) and load in threaded fasteners. What was not widely appreciated before, however, was its ability to provide precise real time measurements of forces affecting a bolted joint, in this case a 2m long foundation bolt on a wind turbine tower. The foundation bolt had already been installed and, according to Borbar, it was not possible to determine its actual elongation or tension without first loosening the bolt. For the purposes of demonstration, however, the initial length of the bolt was recorded using the USM-3 meter and a magnetic transducer, which was placed onto the bolt end. After a while, the wind farm's engineer commented that the elongation measurement did not seem to be stable as the value was constantly drifting. "The tower base foundation bolt was located at a 160o angle from the wind direction," explained Norbar's ultrasonic specialist, Gregory Young. "As the wind increased, it pushed the tower in the general direction of the foundation bolt. This meant that the joint was compressed slightly and the elongation decreased. As the wind decreased, the tower rebounded and the bolt's elongation increased." Young maintained that the device's ability to read minute fluctuations in the bolt tension in real time could be of value to many companies dealing with bolted joint issues. "Many sectors such as the automotive industry will also be interested, since real time changes in bolt tension are highly important in automotive engineering," he said.