Section 6: Selected Applications & Techniques

One of the methods used to inspect rail is ultrasonic inspection. Both
normal- and angle-beam techniques are used, as are both pulse-echo and
pitch-catch techniques. The different transducer arrangements offer different
inspection capabilities. Manual contact testing is done to evaluate small
sections of rail but the ultrasonic inspection has been automated to allow
inspection of large amounts of rail.
Fluid filled wheels or sleds are often used to couple the transducers to the
rail. Sperry Rail Services, which is one of the companies that perform rail
inspection, uses Roller Search Units (RSU's) comprising a combination of
different transducer angles to achieve the best inspection possible. A
schematic of an RSU is shown below.