The RFT system is ideally suited to the inspection of ferromagnetic materials such as carbon steel, nickel and magnetic stainless steels.

The RFT system uses the principle of the "Remote Field Effect". The phase response of an input signal is changed in proportion to the wall thickness.

Exciter and detection coils are typically separated by 3 to 5 times the tube diameter.

The minimum wall loss detectable varies with wall thickness and extent of defect area, but as little as 10% wall loss is detectable in wall thicknesses up to 10mm. Through holes as small as 3mm in diameter are detectable depending on tube diameter and composition.

The accuracy of defect depth measurements is of the order of ±10%. Ideally suited for thick wall tubing.

Probes can be made flexible and hence a major application is in the inspection of boiler tubing. Results are displayed on strip chart format and on a voltage plane display in which defect depth and circumferential extent are displayed.