Remote Field Electromagnetic Technique (RFET)
This is designated to quickly and accurately inspect ferrous tubing upon this technique with the help of automated software.
Brief about Technique:
Unlike the present conventional Eddy current method, the RFET probe uses two cylindrical coils, one driver or exciter coil and another pickup coil (Fig. 1). The driver coil generates a magnetic field when a low frequency AC signal is put into it. This magnetic field penetrates the tube wall and reaches the outside surface of the tube to create a sheath of Eddy current which generates its own magnetic field.
The magnetic field thus generated by the propagating eddy currents re-enters the tube wall to be detected by the pick-up coil located at least approx. 3 diameters of tube pipe away from the driver coil (Fig. 2). If the separation distance between the two coils is 3 tube diameter or more, the direct coupled signal will be reduced so much that it can be safely ignored. The tube wall signal received by the pick up coil is called RFET signal. Any defect located in the vicinity of the driver and pick-up coils will cause disturbances in the trough wall transmission path, which will be detected as a phase and amplitude changes in the RFET signal.
