Low Frequency Electromagnetic Technique

The Low Frequency Electromagnetic Technique works by injecting a low frequency magnetic field into a metal plate or tube and measuring the distortions in the resulting magnetic field that occur over a flaw. This injection can be achieved by using an external horseshoe shaped driver coil. This driver coil is placed such that the return path for the magnetic field is through the area to be tested. Flaws are detected by measuring the magnetic field directly over the flaw area with sensor coils.

A flaw or defect causes the magnetic flux lines in that area to be distorted or different than expected. This distortion can be measured as a change in phase and/or amplitude. With suitable calibration tables the flaw can be analyzed and a determination of flaw depth and shape can be made. By using several sensors in the scanner array it is possible to display a 3D image of the collected data so that the shape and depth of the flaw can be determined.

Typical applications are: Service Water Piping, Fire Protection, Coal Mill Piping, and any piping with access to the pipe O.D. In addition to piping, this test can be used to quickly inspect pressure vessels and heat exchanger shells. It can also be performed through coatings.

Advantages:

• Inspection of straight sections and bends
  
• Minimal Pipe Preparation
  
• Real-Time Display
• Inspects through I.D. or O.D. scale

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