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Magnetic Particle Inspection (MPI) also sometimes called as Magnetic Test (MT) is an effective method for the detection of surface and sub-surface discontinuities in ferrous materials.

images/stories/NDT_01.jpgThe test method is accomplished by inducing a magnetic field in a ferromagnetic material and then dusting the surface with iron particles (either dry or suspended in liquid). Surface and near-surface flaws disrupt the flow of the magnetic field within the part and force some of the field to leak out at the surface. Iron particles are attracted and concentrated at sites of the magnetic flux leakages. This produces a visible indication of defect on the surface of the material.The same effect can be seen when iron filings are attracted to both the north and south ends of a magnet.

There are several ways to induce a magnetic field to the test parts.

images/stories/mag_particle_testing.jpgA current flow method through contact heads, encircling coil magnetising, threaded bard magnetising are the examples of magnetising methods on a magnetic particle bench. The most common method utilised in general industries is the magnetic flow method using electromagnetic yoke as shown to the right.

The particles are often colored and usually coated with fluorescent dyes that are made visible with a hand-held ultraviolet (UV) light (black light).

The test method using fluorescent coated particles is called as Fluorescent Magnetic Particle Inspection or test (FMPI) and the usage of other coloured particles is termed as colour contrast Magnetic Particle Inspection or test (MPI).

Magnetic Particle Inspection (MPI) is the economical and comparative faster non-destructive test method used widely in Aerospace, Locomotive, automotive, power generation, nuclear, petrochemical industries.

The most common examples are testing of crank shafts, cam shafts, connecting rods, engine gears, landing gear, bearing caps, engine blocks, motor shafts, engine bolts, nuts, washers, threaded bars, studs, piping joints ( fabricated joints, welds) in power generation and petrochemical industries, etc.

Magnetic particle test (MT) is a very sensitive test method. It can detect tight in-service fatigue cracks in rotating parts or creep cracks on steam piping. Magnetic Particle Inspection cannot be used for non-ferrous materials and non-magnetic ferrous materials such as austenitic stainless steels.

Vertest performs MPI / MT every day in accordance with AS 1171, ASME V Article 7, ASTM E1444, ASTM E125, ASTM E709, BS 6072, EN 1290 and similar national and international standards.

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