NDT - Phils., Inspection Services Corporation

• 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.