Magnetic Particle Testing


 
Magnetic particle inspection (MPI) is one of the most widely utilized NDT methods since it is fast and relatively easy to apply, in addition to the fact that part surface preparation is not as critical as it is for some of the other NDT inspection methods. MPI uses magnetic fields and small magnetic particles (i.e.iron filings) to detect flaws in components. The only requirement from an inspection standpoint is that the component being inspected must be made of a ferromagnetic material (a materials that can be magnetized) such as iron, nickel, cobalt, or some of their alloys.

With respect to inspection, MPI is used to inspect a variety of product forms including castings, forgings, and weldings. Many different industries use magnetic particle inspection such as structural steel, automotive, petrochemical, power generation, and aerospace industries. Underwater inspection is another area where magnetic particle inspection may be used to test items such as offshore structures and underwater pipelines.

Some advantages of MPI include the following

  • High sensitivity (small discontinuities can be detected).
  • Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.
  • Minimal surface preparation (no need for paint removal)
  • Portable (materials are available in aerosol spray cans)
  • Low cost (materials and associated equipment are relatively inexpensive)

Magnetic particle testing, sometimes called mag particle, MPI, is ideal for identifying surface or near-surface discontinuities in parts and assemblies whose materials have a certain degree of magnetism, such as billets, bars, castings, forgings, fasteners, weldments, brazes, and extrusions.

Magnetic particle inspection (MPI) is one of the most widely utilized NDT methods since it is fast and relatively easy to apply, in addition to the fact that part surface preparation is not as critical as it is for some of the other NDT inspection methods. MPI uses magnetic fields and small magnetic particles (i.e.iron filings) to detect flaws in components. The only requirement from an inspection standpoint is that the component being inspected must be made of a ferromagnetic material (a materials that can be magnetized) such as iron, nickel, cobalt, or some of their alloys.
 

How does magnetic particle examination work?

Magnetic particle inspection is a nondestructive testing (NDT) process for detecting surface and subsurface discontinuities in ferroelectric materials such as iron, nickel, cobalt, and some of their alloys. The process puts a magnetic field into the part and the piece is magnetized by direct or indirect magnetization.
 

Wet MT and dry MT methods

The presence of a surface or subsurface defect or discontinuity in the material allows the magnetic flux to leak. Ferrous iron particles are applied to the part in a dry or in a wet suspension, these variations can be referred to as dry magnetic particle inspection or wet magnetic particle inspection. If an area of flux leakage is present, the particles will be attracted to the defect. The particles will build up around the leakage and form an “indication.” The indication is evaluated to determine its characteristics, its cause, and how to proceed.
 

QIL MPI Inspection

QIL uses MPI to inspect a variety of product forms including castings, forgings, and weldings. QIL’s MPI inspection is carried out, but not limited to the following industries, structural steel, automotive, petrochemical, power generation, and aerospace industries. Some advantages of MPI include the following

  • High sensitivity (small discontinuities can be detected).
  • Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.
  • Minimal surface preparation (no need for paint removal)
  • Portable (materials are available in aerosol spray cans)
  • Low cost (materials and associated equipment are relatively inexpensive)

QIL has an eoerienced of engineers and inspectors who have multiple years of experience in providing MPI inpection services to a wide variety of clients. Please contact us for additional information on what services QIL MPI team can provide you with.

For additional information on the how Quality Inspectors Limited can meet your inspection needs using Magnetic Particle Inspection (MPI), please contact us info@qil.co.ke

• 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
• 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