Magnetic particle testing (MT)
Magnetic particle testing (MT) is a non-destructive testing technique utilized to detect defects or discontinuities (such as cracks) at or near the surface in ferromagnetic metals such as iron, steel, nickel, cobalt, etc. Magnetic particle testing (as well as other non-destructive testing techniques) is primarily utilized in the industrial sector to test metal materials such as oil & gas pipelines and various metal machinery components to prevent failures or accidents. Some of the most common industries that utilize magnetic particle testing include petrochemical, automotive, aerospace and structural steel – just to name a few. In addition, magnetic particle testing may be utilized to inspect underwater structures such as pipelines.
So exactly how does magnetic particle testing work? The concept is actually relatively simple. Any metal object that is magnetized will be surrounded by an invisible magnetic field. If there is a defect – such as a crack or hole in the metal object – the defect will cause a disruption in the magnetic field. Magnetic particle testing allows you to easily see that disruption – and thus identify the defect.
Here is how the actual process takes place. The first step is to magnetize the object being inspected (for example, a pipe weld). Electronic equipment – ranging from a hand-held magnetic yoke to a horizontal MT machine – is used to magnetize the object. Ferrous iron particles (similar to metal filings or shavings) are then applied to the object. The iron particles will be attracted to any area where the magnetic field is disrupted and will form clusters – thus plainly revealing the defect.
Magnetic Particle Testing is done by inducing a magnetic field in a ferromagnetic material and dusting the surface with iron particles. Surface imperfections will distort the magnetic field an concentrate the iron particles near the imperfections, thus indicating their presence.
The training includes : Theory on types of Magnetization, Poles, Current, Demagnetization, Inks, Field indicators and Practical.