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Test method and apparatus for noncontact and nondestructive recognition of irregularities in the wall thickness of ferromagnetic pipes

  • US 6,727,695 B2
  • Filed: 10/09/2002
  • Issued: 04/27/2004
  • Est. Priority Date: 04/24/2002
  • Status: Expired due to Fees
First Claim
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1. A test method for noncontact and nondestructive recognition of irregularities in the wall thickness of ferromagnetic pipes, comprising:

  • passing an electric current through a pipe under test, wherein the electric current comprises a plurality of harmonic components;

    measuring a spectrum of the harmonic components of the electric current;

    measuring a magnetic field produced outside said pipe as a result of passing said electric current through said pipe;

    analyzing a spectrum of the harmonic components of said measured magnetic field; and

    evaluating ratios between identical spectral components of said electric current and said magnetic field to recognize pipe wall thickness irregularities based on frequency dependency of the magnetic field upon the electric current.

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