Magnetic Particle Testing (MPT)
Magnetic Particle Testing is also known as Magnetic particle Inspection (MPI). Magnetic particle Inspection (MPI) is a non-destructive testing (NDT) process for detecting surface and slightly subsurface discontinuities in ferromagnetic materials such as nickel ,iron, cobalt, and some of their alloys. The process puts a magnetic field into the part. The piece can be magnetized by direct or indirect magnetization.
Direct magnetization occurs when the electric current is passed through the test object and a magnetic field is formed in the material. Indirect magnetization occurs when no electric current is passed through the test object, but a magnetic field is applied from an outside source. The magnetic lines of force are perpendicular to the direction of the electric current, which may be either alternating current (AC) or some form of direct current (DC) (rectified AC).
Non-Destructive Testing for MPT
The presence of a surface or subsurface discontinuity in the material allows the magnetic flux to leak, since air cannot support as much magnetic field per unit volume as metals. A wet horizontal MPI machine is the most commonly used mass-production inspection machine.
This requires special equipment that works the opposite way of the magnetizing equipment. The magnetization is normally done with a high current pulse that reaches a peak current very quickly and instantaneously turns off leaving the part magnetized. To demagnetize a part, the current or magnetic field needed has to be equal to or greater than the current or magnetic field used to magnetize the part
This course contains Level 1 and 2 study material from NDT Consultancy Services and covers the theory of Magnetic Particle Examination. Magnetic fields, flux leakage, magnetization processes, particles/mediums, applications, basic principles, and safety considerations are addressed.
This 24-hour course exceeds the instruction outline and criteria specified in the ASNT Recommended Practice SNT-TC-1A and ASNT Standard Topical Outlines for Qualification of Nondestructive Testing.