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What are the advantages and disadvantages of utilising a permanent magnet for magnetic particle inspections?


Permanent magnets produce a longitudinal magnetic field between the poles. Modern variants of the horseshoe magnet have adjustable arms, and may have variable geometry removable pole ends. Optimum defect detectability is at 90° to the poles. Modern opinion tends not to favour permanent magnets.

  • No power supply needed
  • Direct field only
  • Cling to vertical surfaces
  • Deteriorate with wear
  • No electrical contact problems
  • Have to be pulled from test surface
  • Inexpensive
  • No control over field strength
  • No damage to testpiece
  • Magnetic particles attracted to poles
  • Lightweight
  • Legs must have area contact
  • May have to be recharged

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