MT Free Quiz
Applications of Magnetic Particle Testing (MT)
Magnetic particle inspections work by running a magnetic current through the material that is being inspected.
When the current is interrupted by a discontinuity; magnetic flux lines change direction to follow the easiest path (same as when an stream of river is diverted and goes around a blockade), indicating its presence by re-arrangement of magnetic particles that follow the magnetic flux lines; therefore allowing inspectors to identify its location in the material.
ADVANTAGES OF MT
- It is quick and relatively uncomplicated.
- It gives immediate indications of defects.
- It shows surface and near surface defects, and these are the most serious ones as they concentrate stresses.
- The method can be adapted for site or workshop use.
- It is inexpensive compared to radiography.
- Large or small objects can be examined.
- Elaborate pre-cleaning is not necessary.
LIMITATIONS OF MT
- It is restricted to ferromagnetic materials – usually iron and steel, and cannot be used on austenitic stainless steel.
- It is messy.
- Most methods need a supply of electricity.
- It is sometimes unclear whether the magnetic field is sufficiently strong to give good indications.
- The method cannot be used if a thick paint coating is present
- Spurious, or non-relevant indications, are probable, and thus interpretation is a skilled task.
- Some of the paints and particle suspension fluids can give a fume or fire problem, particularly in a confined space.