MAGNETIC FLUX LEAKAGE IN NDT TECHNOLOGY

Magnetic Flux Leakage (MFL) nondestructive test systems accurately detect defects in heavy-wall ferromagnetic tubing, including oil country tubular goods (OCTG). 

These electromagnetic test methods are also used to inspect high-permeability ferromagnetic metals such as carbon steel bar, plate, wire rope and parts. The method can also be used to detect ferritic inclusions in non-ferritic material.Magnetic flux leakage and Non destructive Testing

  • For typical OCTG and other heavy wall tube tests, Flux Leakage technology detects longitudinal and transverse defects as small as 5% on OD and ID, as well as defects within the wall, depending upon material type and condition.
  • MFL inspection uses a DC magnetizing field to create enough flux density to bring the material to near-saturation. A transverse magnetizing field is used to detect longitudinally oriented defects, while a longitudinal field is used to find transverse defects.
  • Surface or internal conditions such as cracks, pits, seams and other defects interrupt the flux field and “leak” beyond the product surface.
  • This leakage flux is detected by flux sensor probes with MAC configured rotary inspection devices which can wirelessly transmit this data to the instrumentation for processing and analysis.
  • The amplitude and frequency of the voltage generated by the flux sensor in response to a discontinuity is generally indicative of the severity and location of that discontinuity.
  • Combining MFL inspection with Ultrasonic (UT) testing fulfills certain API standards for OCTG pipe that require a second method, at the discretion of the pipe producer, when using UT as the first method.

 

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