If you have any questions you would like posted here please contact us. The number that can be inspected depends very much on the condition of the tubes and the ease of access to the tube ends. A Differential probe is suited for smaller defects, while the Absolute probe is suited for general wall loss, sizing, etc. 4 . In a remote field probe, the field energy from the exciter coil flows out through the tube wall, along the outside of the tube, and back through the tube wall at the detector coil.
Aluminum fins on the outside of the tube alter the energy flow patterns.
If the tubes are in perfect, as-new condition, the remote field signal is weakened but not destroyed. But if there are damaged or bent fins, their characteristic signals may mimic or obscure defect signals. The remote field probe becomes a bent-fin detector. For this reason we recommend IRIS over remote field as the most suitable technology for aluminum-finned tubes. The ultrasonic IRIS was developed to examine air finned tubes.