Eddy current(ET) and Remote Field Testing（RFT） ：
a. Purpose: Detecting surface flaws and corrosion of tube or metal.
b. Principle:
1). General eddy current: When the coil probe carrying AC approaches the metal specimen by electromagnetic induction, the metal conductor is induced to generate countless eddy currents under its alternating magnetic field, and this eddy current then generates a secondary magnetic field, induces a voltage signal so that flaws and condition of the specimen can be detected.
2). Remote Field Eddy Current: RFT is used to detect the defects and corrosion in ferromagnetic materials. RFT uses a low frequency signal which allows electromagnetic energy to penetrate the tube walls, so that external and internal flaws can be detected.
c. Application (ET) (RFT):
1). Tubes of titanium, stainless steel, Monel, Copper....
2). feed water heater, heat exchanger…
3). Condenser, Air cooler, Air conditioner
4) Al-finned carbon steel tube
5) Boiler tube
6) Buried tube
7) RFT is applied on Ferro-magnetic tubes
8) Weld Joints
