Define Underwater Magnetic Particle Testing?
Underwater magnetic particle testing (UWMT) is a non-destructive testing suited for detection of surface cracks or discontinuities in magnetic materials underwater. Magnetic particles are attracted to flux leak- ages at the surface of magnetised materials forming a ridge of magnetic particles around the surface cracks. In operation, magnetic element is magnetised using an electro- magnetic yoke specially designed for underwater use.
Where surface discontinuities exist, with the yoke's field of influence, magnetic flux will escape from the surface of the part. Slurry of magnetic particles are attracted to, and aligned along with the leaking magnetic flux. The particles are brightly coloured and form a visible indication corresponding to the location of discontinuities at or very near the part surface.