Eddy Current

Quality and NDT Solutions, LLC (QNS) delivers quick and affordable support, services and solutions to multiple industries, including Aerospace, Petrochemical, Power Generation.   QNS provides a variety of Nondestructive Testing and Evaluation (NDT/NDE) services, including Eddy Current (EC) and Advanced EC inspections, training and support.

Eddy Current inspection is a type of Electromagnetic testing.  Eddy currents are created in a material through a process called electromagnetic induction.  When an eddy current probe is applied to a conductive material, electrical currents are created which flow in a circular path, similar to eddies found a river or stream.  Minute changes in the flow of eddy currents and resulting magnetic fields are measured and amplified through specialized circuitry for readout and interpretation by certified inspectors.

Applications

The aerospace industry regularly utilizes Eddy Current for crack detection, conductivity, corrosion detection, coating thickness and bolt hole flaw detection. 

Petrochemical, power generation and other industrial sectors utilize eddy current for corrosion detection, material and coating thickness, and tube thinning.  Heat exchanger and boiler tubes are commonly inspected using Eddy Current and Remote Field Testing for ferromagnetic materials (see below for Advanced Eddy Current methods).

Eddy current inspection is fast and results are real time.  The need for surface preparation needed for Penetrant or Magnetic Particle testing is eliminated. 

In most cases, testing can be performed through coatings, thus eliminating the need to stripping of finishes.  Inspections can be performed through multiple layers of material, although interpretation of test results can be complex and require the need for experienced individuals.

Eddy current is sensitive to small cracks and other defects, and can detect surface and near surface defects.  Equipment is portable and the inspection results are immediate.

Like any nondestructive inspection, the Eddy current inspection method has its limitations.  Materials to be tested must be electrically conductive and the surface finish typically must be consistent.  To enable flaw detection, flaw orientation must be understood and managed by the technician performing the test.  Reference standards similar to the material being tested must be used and the degree of skill and training required for eddy current is typically more extensive than other NDT methods.

Equipment and Training Requirements

Eddy Current equipment ranges from basic to complex.  Basic flaw detectors are widely available from a variety of manufacturers.  Probes, cables and calibration standards are typically unique to the application and material being tested and can become quite costly. 

Electromagnetic testing training and experience requirements vary by industry.  Regardless of the industry, a thorough training program is essential.  Technicians must have a comprehensive understanding of the test method to ensure a reliable test.   A potential Level 2 technician candidate in the aerospace is required to have 80 hours of classroom training and 800 experience hours prior to becoming certified.  This is due to the complexities of the method and the various applications of the inspection method.