A contact-type ultrasonic inspection system, mounted on a carriage that is pulled behind any hi-railer vehicle on a railroad track. This is a skid type inspection fixture that slides onto the top face of the joint bars (one each side of the rail) and uses ultrasonic energy to inspect the back (hidden side) of the joint bar for cracks. These cracks develop at the top of the joint bar where it contacts the rail, just under the rail head.
Cracks developing on the inside surface of the joint bar cannot be seen by visual inspection until they propogate to the outside surface, in which case it may be too late, causing an open joint wth the potential of a train derailment. And, UT inspection was limited to a person with a hand-held analyzer and transducer. Because of the time involved manually inspecting joint bars, and all of the joint bars that are in place on the North american railroad tracks, UT inspection rarely ever happened.
This system allows two men to travel up to 10-mph on the track and reliably inspect each joint bar, returning an overall detection rate of 83% on flaws as small as 1/8-in.