Remote field testing (RFT) is applied in the testing of ferromagnetic heat exchanger tubes such as those made of carbon steel. The test is performed with a bobbin coil that transmits an electromagnetic field in the tube. These coils look similar to those for saturation only the housing is longer and there are two connections to the testing unit as opposed to one. . RFT is a relativity fast technique. For example, it is possible to test from 400-420 5-6 meter heat exchanger tubes in a 12-hour shift. This depends both on how clean the tubes are and to some extent the number of defects or indications needing evaluation. Remote field testing is limited to detection of large discontinuities and severe wall loss.