MAGNETIC PARTICLE TESTING

2.2.1        MAGNETIC PARTICLE TESTING:-

NDT method is accomplished by indicating a magnetic filled in a ferromagnetic material and then dusting the surface with iron particles (either dry or suspended in liquid).

Surface and near-surface flows produces magnetic poles or distort the magnetic filled in such a way that the iron particles are attached and concentrated. This produces a visible indication of defects on surface of material.

Type of MPT:
            1. visual testing

2. Fluorescent testing

Main uses of MPI:

                 It is used to inspect ferromagnetic materials (those that can be magnetized) for                     defects that result in a transmission in the magnetic permeability of a material.

Magnetic particle inspection can defect surface and near surface.

Equipment’s used:

A).Yoke

B). Magnetic particle (liquid &solid form)

C).pieguage

D).controller

E) UV Light source

Procedureof MPI:

1. clean the surface & hold the yoke on a given component and apply the current to produce the magnetic filled.

2. Apply the ferrous indicator (generally black in color) on the surface area of the component.

3. By holding the yoke in a different angles observe the discontinuities (if any)

4. Inspection & demagnetization.

Advantages of MPI:

1. The large surface area of complex parts can be inspected rapidly.

2. It can detect surface and subsurface flaws.

3. Surface preparation is less critical than it is in penetrant inspection.

4. MPI are produced directly on the surface of the parts and form an image of the discontinuity.

5. The cost is low.

Disadvantages of MPI:

1. Only ferromagnetic materials can be inspected.

2. Proper alignment of magnetic filled and defect is critical.

3. Large currents are needed for very large parts.

4. It requires smooth surface