SERVICES >> ADVANCED NDT HEAD E&B TUBES

Remote Field Electromagnetic Testing (REFT)

RFET is a Low Frequency Technique that accurately measures wall loss especially in Ferromagnetic tubes. It uses a relatively simple instrument and is not affected by high magnetic permeability of ferromagnetic material assuming that it is uniform in the length of the tube.

Two primary paths exist for coupling the energy between the exciter and the receivers. The direct field which carries no useful information of the tube wall condition is rapidly attenuated with distance down the pipe and is undetectable beyond about two pipe diameters. The indirect field diffuses radically outward through the pipe wall, moves along the pipe, and re-diffuses radically back through the pipe wall. The zone in which this indirect field is dominant is named the "remote field zone".

Any discontinuity present in the material will affect the Remote Field signal . These changes in the Remote field can be compared to those measured on known machined flaws in a calibration tube with properties similar to the one being tested. A comparative analysis provides the value of tube wall loss on the tube being tested.  RFET can be used to inspect Ferro-magnetic tubes in

• Shell and Tube Heat Exchangers
• Boilers 

It is well suited for the detection of the following types of corrosion

• General Corrosion / Erosion
• Localized Corrosion and Pitting
• Support Plate Fret wear extending beyond the baffle
  

It has limitations in the detection and sizing of

• Under Baffle Corrosion
• Isolated pitting / pin holes
  

Signal Display