Magnetic Particle Testing - Advantages and Disadvantages

What is Magnetic Particle Testing? 

    Magnetic particle testing is Used for detect Flaws or Discontinuous in any ferromagnetic material surfaces or nearby surfaces like iron, Nickel, Cobalt etc. Magnetic Particle testing is also known as Magnetic Testing or Magnetic Particle Inspection.

What-is-MPI

Basic Principle of Magnetic Particle Testing:

    Basic Principle of Magnetic particle testing is the specimen or component is magnetized to produce magnetic lines of flux or force on surface of material.

    In this page you will learn about magnetic particle testing and their advantages and disadvantages.

    This method is used to detect surface and subsurface discontinuities in ferromagnetic substances. This is also used to test the well works the component which is to be tested is clean first. After cleaning the specimen can be magnetized either by direct magnetization or by indirect magnetization.

Direct Magnetization in Magnetic Particle Testing:

    Direct magnetization occurs when electric current is passed directly through a specimen to produce a magnetic field.

Indirect Magnetization in Magnetic Particle Testing:

    In indirect magnetization magnetic field is applied by using a strong external magnetic field without passing current through the specimen. Indirect magnetization can be done by using permanent magnets or electromagnets.

    Since magnetic fields in permanent magnet cannot be varied electromagnets are preferred usually for testing electromagnet consists of coil of wires through which current is supplied to produce magnetic field. The amount of magnetic field produced depends on amount of current passed through the coil. Magnetic flux just created is used to detect the flaws in the specimen. This flux lines running along the surface will deviate from the path if it approaches a crack find magnetic particles are applied to the surface of specimen. For visible indication of cracks these fine magnetic particles are attracted to the area of flux deviation creating a visible indication of flaw.

Advantage of Magnetic Particle Testing:

    Simplicity of operation is the main advantage of magnetic particle testing. It is quick and simple. Magnetic particle inspection is Uncomplicated then other methods of inspect specimen surfaces. The method is used in sites or workshops. It shows immediately defects of surfaces.

Disadvantages of Magnetic Particle Testing:

    Major disadvantage of this method is that it is limited to ferromagnetic substance surface like iron, Nickel, Cobalt etc. On your surface flaws thus you have learned about magnetic particle testing and their advantages and disadvantages.

Magnetic particle testing is a simple process for two conditions:

    Wet Magnetic Particle Testing (WMPT) and Dry Magnetic Particle Testing (DMPT).

    In any one process, the process begins by a magnetic current through the specimen or component. Any cracks, flows or defects in the surface or nearby surface in specimen will interrupt the flow of current and will effect on magnetism to spread out from them. This will create a “flux leakage field” at the defect or flow.

    The second step of process is spreading particles of metal over the component or specimen surface. If there is any crack or defects on or near the surface, the flux leakage field will draw the particles to the damage site on specimen. This helps to provide a visible indication of the approximate size and shape of the flaw or defect. In this process the material must be ferromagnetic material.

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