Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Rail Inspection
One of the major problems that railroads have faced since the earliest days is
the prevention of service failures in track. As is the case with all modes of
high-speed travel, failures of an essential component can have serious
consequences. The North American railroads have been inspecting their
most costly infrastructure asset, the rail, since the late 1920's. With increased
traffic at higher speed, and with heavier axle loads in the 1990's, rail
inspection is more important today than it has ever been. Although the focus
of the inspection seems like a fairly well-defined piece of steel, the testing
variables present are significant and make the inspection process challenging.
Rail inspections were initially performed solely by visual means. Of course,
visual inspections will only detect external defects and sometimes the subtle
signs of large internal problems.