Magnetic Particle Testing (MPT) and Magnetic Particle Inspection (MPI)

Magnetic particle testing (MPT) and magnetic particle inspection (MPI) are non-destructive testing techniques that are useful in detecting sub-surface and surface discontinuities and cracks. Since these tests use electricity to create a magnetic field, this type of test only works on ferromagnetic materials, such as iron (Fe), gadolinium (Gd), cobalt (Co), nickel (Ni), and their associated alloys. 


In MPT and MPI, a magnetic field and metallic particles are applied to the test material. If there is a surface or near-surface flaw, such as a pit or crack, the metallic particles will concentrate at the site of the imperfection known as the “indication.” 


At Red Deer Ironworks, we may use either alternating current (AC), half-wave direct current (HWDC), or full-wave direct current (FWDC) to reveal points of indication as prescribed by the client’s testing request. Some of the methods we can employ in MPI and MPT include:

  • Dry method (non-fluorescent)
  • Wet method (fluorescent)
  • Wet method (non-fluorescent)


Red Deer Ironworks provides MPT and MPI testing in Colorado, Texas, Red Deer, and the surrounding areas.


Advantages of Magnetic Particle Testing

Magnetic particle testing is cost-effective, reproducible, non-destructive, and fairly easy to apply to most ferromagnetic materials and alloys. Since indications appear on the actual part being tested, the margin of error in locating surface and near-sub-surface discontinuities is rather slim. 


MPT can be applied to high-volume production parts or one-off pieces essential to the operation of a piece of machinery or other application. One reason Red Deer Ironworks clients prefer MPT and MPI are the cost efficiencies and consistent results when compared to more advanced, yet more expensive testing methods. 


Limitations of Magnetic Particle Testing

As with any type of scientific test, magnetic particle testing is not without its limitations. Since the part must be conductive to an electrical current, it must be composed of a ferromagnetic metal or alloy. To locate discontinuities, the major dimension of indication must allow interception of the magnetic field — parts with complex geometrical patterns may alter the intensity of the magnetic field in some areas and cause difficulty in estimating the correct amperage for the test. Lastly, it is often necessary to demagnetize the part following each test.


In most inspections, the shape and composition of the test part will dictate the level of testing confidence at various depths. Near-surface depths of 1-3mm are generally within the acceptable range for magnetic particle testing. 


How Does MPI and MPT Work?

The current working model in physics shows electricity and magnetism (electromagnetism) to be essentially one and the same; when a magnetic field is manipulated, an electric field is formed; when an electric field is presented, a magnetic field also forms. Therefore, an electrical current — when passed through conductive materials — can form a magnetic field useful in magnetic particle testing and magnetic particle inspection.


Request MPT or MPI

If you are searching for a reliable, cost-effective method to detect indications in your ferromagnetic materials, contact Red Deer Ironworks Inc. for MPT or MPI testing in Colorado, Texas, or Red Deer.

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