remote field testing (rft)

Remote Field Testing is an electromagnetic examination which utilizes the through transmission effect to produce a resulting field that is affected by anomalies. It is measured a few or more tube diameters away from the AC excitation source without any tube magnetization or saturation. The remote field phenomenon is an electromagnetic testing technique used primarily for in-service, baseline, or QC inspection of ferromagnetic tubing and piping.

We at Horizon Testing Inc. utilizes the Zetec MIZ-28 in conjunction with Carbon Steel Inspection (CSI), advanced design probes, remote field amplifier, and software. This inspection consists of a full-length examination performed from the inside of the tubes with equal inner and outer surface discontinuity detection and sizing. An alternating current is applied to an excitation coil which generates a strong electromagnetic field that propagates out of, and extends away from, the exciter along the tube length. The field then re-enters the tube wall axially from the exciter.

The inducer voltage is measured through the use of a detector coil, bobbin, or pancake that is placed in the remote field zone providing for a volumetric inspection with equal sensitivity to ID and OD anomalies of the tube. The sensor coils pick up the disturbance of the field due to the presence of any anomaly caused by corrosion, stress, foreign object, or mechanical vibration. The signal is measured relative to the X-axis in degrees which equates to flaw depth. The technology has the ability to display in a (X-Y) format.

This allows the data analysis to use pattern recognition for characterizing the signals. Typically, the analysis parameters are established where the phase or angular relationship of the signal is measured relative to the X-axis in degrees, which equates to flaw depth.