What Is Remote Field Eddy Current Testing?
Remote Field Eddy Current Testing (RFET) is an electromagnetic inspection technique
specifically developed for the inspection of ferrous (magnetically permeable) tubes — the
material category for which conventional eddy current testing has limited effectiveness due to
the ferromagnetic properties that attenuate and distort standard ECT signals.
RFET uses a low-frequency exciter coil located inside the tube that transmits electromagnetic
energy outward through the tube wall. This energy travels through the wall, propagates along
the outside of the tube, and re-enters the tube through the wall again — where it is detected by a
receiving coil located approximately two tube diameters behind the exciter. Because the signal
has made two complete traversals of the tube wall, it is equally sensitive to inner-wall and outer
wall defects — a significant advantage over techniques that are more sensitive to one surface
than the other.
RFET is applicable to:
- Carbon steel heat exchanger tubes
- Cast iron tubes (cooling water systems, older installations)
- Ferritic stainless steel tubes
- Carbon steel boiler tubes and finned tubes
RFET detects:
- Generalised wall thinning and pitting — ID and OD
- Baffle cut wear and support plate erosion
- General corrosion and localised metal loss
- Through-wall perforations