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Introduction & Basic Principle

RFEC uses two coils, one of the as the driver coil or transmit-coil is excited a low frequency AC signal and the other coil, known as the pick up coil, will receive a signal which is the vector sum of

• A direct coupled signal from the driver coil
• A very weak remote-field (RFEC) signal from the tube wall.

The RFEC signal decreases much more slowly than the direct-coupled signal as the two coils are separated. With sufficient coil separation (app. 3 tube diameters), the RFEC signal will soon become dominant.

Applications

• commonly applied to examination of boilers, heat exchangers, cast iron pipes, and pipelines.

Advantages

• No need for direct contact with the pipe wall
• probe travel speed around 30 cm/s (1 foot per second
• Better in ferromagnetic materials when compare with Eddy Current Testing.

Limitation

• less sensitive to probe wobble than conventional eddy current testing (its sister technology for nonferromagnetic  materials)
• because the field travels on the outside of the pipe, RFT shows reduced accuracy and sensitivity at conductive and magnetic objects on or near the outside of the pipe, such as attachments or tube support plates.
• two coils generally create two signals from one small defect — a headache for the analyst
• Before the examination, tubes must be cleaned on the inside to bare metal.

 

 

 
 
 

ECT
IRIS
MFL
RFEC
TIR
TOFD

PAUT
CORROSION MAPPING

 
 
 


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