METHOD AND APPARATUS FOR DETECTING FLAWS IN RAILS

A rail inspection device 30 having a compliant, approximately circular spacer 36, and a spring-loaded electromagnetic sensor, which may be an eddy current sensor 34, within the spacer 36. The inspection device 30 may be on an engine driven train carriage or a pedestrian controlled unit and preferably comprises a locating device. The spacer 36 has an inner surface and outer surfaces 38 and 40, defining the spacer 36 thickness. The thickness varies, preferably smoothly, around the circumference of the spacer 36, the minimum thickness preferably being opposite the maximum thickness. The electromagnetic sensor 34 is against the inner surface 38 of the spacer 36 and is preferably driven by an alternating current controlled by a control unit. The outer surface 40 of the spacer 36 contacts the inspected rail 32. The control unit preferably contains a signal processing unit 50 that isolates frequencies in the output signal of the sensor 34 and performs Fourier transforms on the output. A method of using the inspection device 30 wherein the a constant sinusoidal lift-off variation is isolated from the output signal is disclosed. The method may involve displaying the output signal and adjusting the Argand angle to realign the crack signal.