Eddy Current Testing

Eddy Current testing is based on measuring the impedance of a coil or inducing electrical currents (Eddy Currents) in a conductive material. Any changes in the coils impedance due to geometry, material changes, or discontinuities- such as pitting, erosion, corrosion, baffle fretting, cracking, and/or other anomalies will disrupt the flow of Eddy Current and produce a representative signal on the ET instrument.

Eddy Current testing is commonly used to inspect nonmagnetic and slightly magnetic alloys. Further, Eddy Current testing is very sensitive to small defects such as stress corrosion cracking, however it is critical to use proper Eddy Current techniques and procedures. Interpretation of Eddy Current data is very complex and requires years of experience to correctly characterize signal formations (See Figure 3).

In using Eddy current, QIL inspectors are able to detect cracks in metal blocks using a coil of wire wrapped around a piece of iron to generate the magnetic field that caused the eddy currents to form in the metal. The magnetic field that is generated by the eddy currents can be detected using this same probe.
QIL staff can monitor the magnetic field being produced by these eddy currents through use of an eddyscope. When a change in the magnetic field is detected, it would inform QIL inspectors that some sort of defect in the material has been detected.

The main advantages of this method of testing is the portability of the equipment making it ideal for on-site applications with the added benefit that it is not necessary to remove any surface paint. QIL currently undertakes testing of surface and near surface flaw detection, metal sorting by grade, hardness and coating thickness measurement.

For additional information on the how Quality Inspectors Limited can meet your inspection needs using Eddy Current Inspection, please contact us info@qil.co.ke

  • • Detection of very small cracks in or near the surface of the test part
  • • Physically complex geometries can be investigated
  • • Electrical conductivity measurement
  • • Coating thickness measurement
  • • Provides immediate feedback
  • • Portable
  • • No couplant is required
  • • Checking for surface breaking cracks on metal
  • • Metal tube inspection for discontinuities
  • • Heat treat verification of metals
  • • Checking conductivity of metals, thickness of coatings and of thin metals
  • • Inspection of friction stir welds
  • • Testing gas turbine blades
  • • Inspection of a cast iron bridge
  • • Inspection of Hurricane propeller hubs
  • • Testing nozzle welds in nuclear reactor