Surface Methods
Magnetic particle inspection using electromagnetic yokes.
Overview
Magnetic particle inspection (MT / MPI) detects surface and slightly subsurface discontinuities in ferromagnetic materials (iron, nickel, cobalt and many of their alloys). A magnetic field is induced; flux leakage at a discontinuity attracts magnetic particles, forming a visible indication.
Applications
- Welds, castings, forgings, pressure vessels, fittings, shafts, and structural steel
- Fabrication and in-service inspection
Technique Notes
Surfaces must be clean and free of thick paint, scale, or contaminants that could mask indications. AC magnetization is preferred for surface discontinuities; DC can aid detection of slightly subsurface flaws. Demagnetization is available when residual magnetism must be reduced (see our De-Magnetization service).