RAIL INSPECTION IN ULTRASONIC INSPECTION.

Rail inspections were initially performed solely means. Ofcourse, visual inspections will only detect external defects and sometimes the subtle signs of large internal problems. The need for a better inspection Methley became a high priority because of aderailment at Manchester, NY in 1911, in which 29 people were killed and 60 were seriously injured. In the U.S bureau of safety's ( now the national transportation safety board)  investigation of the accident, a broken rail was determined to be the cause of the derailment. The bureau established that the rail failure was caused by defect that entirely internal and probably could not have been detected by visual means. The defect was called a transverse fissure ( example shown on the left).  The railroads began investigating the prevalence of this defect and found transverse fissures were widespread.
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 transducer arrangements offer different inspection capabilities. Manual contact testing is done to evaluate small section of rail but the ultrasonic inspection has been automated to allow inspection of large amounts of rail.
Fluid filed wheels or sleds are often used to couple the transducer to the rail. Sperry Rail services,  which is one of the companies that perform rail inspection, uses Roller search units ( RSUs)  comprising a combination of different transducer angles to achieve the best inspection possible. A schematic of an RSU is shown below.