- Driver coil is excited by AC current and generate magnetic fields.
- Magnetic fields travel towards the tube wall then forms Eddy Current sheath.
- Eddy Current itself produces magnetic field and this magnetic field is traveling along the outside surface(Remote Field). Then it re-enters into the tube wall.
- If there is any wall thickness changes in the path, the magnetic field will be distorted.
- This will be detected by receiver coil then measure the phase and amplitude changes.
- Direct field is eliminated by increasing the distance between the two coils ( 2 tube OD Distance)
Advantage of RFET
- Suitable for ferromagnetic tubes such as those found in heat exchangers and boilers.
- Localized corrosion, Pittings
- Equally sensitive to internal and external flaws.
- Can inspect tubes up to 75mm OD with 5mm thickness.
- Relatively insensitive to probe liftoff or wobble.
- Typical pull speed between 6” and 12” per second.
