Magnetic Particle Testing (MT)
Magnetic Particle Testing (MT) is a non-destructive testing (NDT) technique used to inspect pipelines for surface and slightly subsurface discontinuities, such as cracks, porosity, and laps. MT is often used to inspect pipelines that are coated with metal or other magnetic materials, as it relies on the interaction between magnetic fields and magnetic particles to detect discontinuities.
The process of Magnetic Particle Testing involves the following steps:
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Preparation of the surface: The surface to be inspected must be cleaned and degreased to remove any contaminants that could interfere with the magnetic particle inspection.
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Magnetization: A magnetic field is applied to the surface of the pipeline by either an electromagnet or a permanent magnet.
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Application of magnetic particles: Fine iron oxide or iron oxide-coated magnetic particles are suspended in a liquid medium and applied to the surface of the pipeline. The magnetic particles are attracted to the surface of the pipeline by the magnetic field, and any discontinuities present will cause the magnetic particles to congregate and form an easily visible indication.
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Inspection: The pipeline is inspected under ultraviolet (UV) light or visible light to detect any indications formed by the magnetic particles. The inspector will look for any areas where the magnetic particles have formed a concentrated indication, which could indicate the presence of a discontinuity.
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Demagnetization: Once the inspection is complete, the magnetic field is removed to release the magnetic particles from the surface of the pipeline.
Magnetic Particle Testing has several advantages, including the ability to inspect pipelines quickly and efficiently, the ability to inspect pipelines that are coated with metal or other magnetic materials, and the ability to inspect pipelines in difficult-to-reach areas. However, MT is not suitable for the detection of subsurface discontinuities, and it may not be effective in detecting discontinuities in pipelines made from non-magnetic materials.
In conclusion, Magnetic Particle Testing is a non-destructive testing technique used to inspect pipelines for surface and slightly subsurface discontinuities, such as cracks, porosity, and laps. The process involves the application of a magnetic field to the surface of the pipeline, the application of magnetic particles, and the inspection of the pipeline under ultraviolet (UV) light or visible light to detect any indications formed by the magnetic particles. MT has several advantages, but it may not be effective in detecting discontinuities in pipelines made from non-magnetic materials.