Therefore, for proper inspection of a component, it is important to be able to establish a magnetic field in at least two directions. A variety of equipment exists to establish the magnetic field for MPI.One way to classify equipment is based on its portability. Some equipment is designed to be portable so that inspection can be made in the field and some is designed to be stationary for ease of inspection in the laboratory or manufacturing facility. Portable equipment will be discussed first.
PERMANENT MAGNETS:-Permanent magnets are sometimes used for magnetic particle inspection as the source of magnetism. The two primary types of permanent magnets are bar magnets and horseshoe (yoke) magnets. These industrial magnets m are usually very strong and may require significant strength to remove them from a piece of metal.Some permanent magnets require over 50 pounds of force to remove them from the surface. Because it is difficult to remove the magnets from the component being inspected and sometimes difficult and dangerous to place the magnets, their use is not particularly popular. However permanent magnets are sometimes used by diverse for inspection in underwater environments or other areas, such as explosive environments, where electromagnets cannot be used. Permanent magnets can also be made small enough to fit into tight areas where electromagnetes might not fit.