Remote
Field Testing (RFT) is an electromagnetic method of
nondestructive testing whose main application is finding
defects in steel pipes and tubes. RFT may also referred to
as RFEC (Remote Field Eddy Current) and RFET (Remote Field
Electromagnetic Technique).
An RFT probe
is moved down the inside of a pipe or tube and is able to detect inside and
outside defects with approximately equal sensitivity. Although RFT works in nonferromagnetic materials such as copper and brass, its sister
technology eddy current is also suitable for these materials.
The basic
RFT probe consists of an exciter coil (also known as a transmit
or send coil) which sends a signal to the detector (or receive
coil). The exciter coil is energized with an AC current and emits an
alternating electro-magnetic field. The field travels outwards from the exciter
coil, through the pipe wall, and along the pipe. The detector is
placed inside the pipe two to three pipe diameters away from the
exciter and detects the magnetic field that has traveled back
in from the outside of the pipe wall (for a total of two
through-wall transits).
In areas
of metal loss, the field arrives at the detector with a faster
travel time (greater phase) and greater signal strength
(amplitude) due to the reduced path through the steel. Hence the
dominant mechanism of RFT is through-transmission, and the
dominant energy source is the axial magnetic field.
Products
Remote
Field Testing
