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What are the advantages and disadvantages of Magnetic Particle Inspection (MPI) in Non-Destructive Examination (NDE)?


Frequently Asked Questions

Advantages of the Magnetic Particle method of Non-Destructive Examination are:

  • It is quick and relatively uncomplicated
  • It gives immediate indications of defects
  • It shows surface and near surface defects, and these are the most serious ones as they concentrate stresses
  • The method can be adapted for site or workshop use
  • It is inexpensive compared to radiography
  • Large or small objects can be examined
  • Elaborate pre-cleaning is not necessary


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Disadvantages of the Magnetic Particle method of Non-Destructive Examination are:

  • It is restricted to ferromagnetic materials - usually iron and steel, and cannot be used on austenitic stainless steel
  • It is messy
  • Most methods need a supply of electricity
  • It is sometimes unclear whether the magnetic field is sufficiently strong to give good indications
  • The method cannot be used if a thick paint coating is present
  • Spurious, or non-relevant indications, are probable, and thus interpretation is a skilled task
  • Some of the paints and particle suspension fluids can give a fume or fire problem, particularly in a confined space

Books on the subject are:

  • R Hamshaw, Introduction to the Non-Destructive Testing of Welded Joints, 2nd edition, Abington Publishing, Cambridge, UK, 1996 (ISBN 1 85573 314 5)
  • C E Betz, Principles of Magnetic Particle Examination, published by the Magnaflux Corporation, 1967.
  • Magnetic Particle Examination, NDE Monograph, published by the Non Destructive Examination Society of Great Britain, 1975
  • David Lovejoy, Magnetic Particle Inspection, A Practical Guide, published by Chapman Hall, 1993

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