... bringing integrity to bolted joint assembly
The MIN-MMX, Ultrasonic Bolt Tension Monitor, defines the state of the art in the measurement of the actual elongation produced by tightening a threaded fastener. Used by proficient Technicians, the MIN-MMX can measure the elongation very accurately in fasteners of virtually any material from 1/2 inch to 8 feet in length. The measurement is achieved by determining the change in the transit time of an ultrasonic shock wave along the length of the fastener as the fastener is tightened by any method. The on-board microcomputer automatically interprets this time measurement to display the time(nanoseconds), elongation, load, stress, or %strain from stretching a fastener. Through the use of high speed digital signal processing and automated diagnostics, the MIN-MMX minimizes the requirement for extensive operator training. With built in data recordation and reporting through an RS232 interface, the MIN-MMX offers a reliable solution to the most difficult bolting problems.
In attempt to address industry's dangerous and mistaken practice of relying on "torque" as an indication of bolt preload, a number of methods have been devised to control bolt loads: