Magnetic particle testing (MPT) is a non-destructive method for detecting surface and subsurface flaws in ferromagnetic materials:

A magnetic field is created by passing a low-voltage, high-amperage current through the material being tested. When there are flaws, the magnetic field lines distort, creating a “magnetic leakage field”. Dyed or fluorescent magnetic particles are then applied to the surface. The particles migrate to the flaw, forming an indication that’s much larger than the actual flaw. An inspector can then visually identify the flaw.

MPT is used in many industries, including aerospace, automotive, marine, power, oil and gas, engineering, and fabrication. It’s often used to determine if a component is fit for service.

The most popular method for MPT is the yoke technique, which uses an electric coil to create a magnetic field. Yoke kits can be used indoors, outdoors, and inside vessels and tanks.

AC is recommended for rough surfaces because it gives the particles more mobility. DC is recommended for detecting subsurface discontinuities because it can magnetize materials more deeply.

Cracks can be preserved for later inspection by using photography or peel-off transparent adhesive film

APPLICATIONS

Weld inspection – Structural / Piping
Casting / Forgings / Valves