Magnetic Particle Inspection- Applications And Equipments

By Author: Nicola Jackson
Total Articles: 40
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Magnetic Particle Inspection (MPI) is a process that detects the surface and subsurface discontinuities in certain metals, like iron, cobalt and nickel, as well as some rare metals, like gadolinium, by Non-Destructive Testing (NDT). These metals are referred to as ferroelectric materials or alloys. In the early days, magnetizing was usually applied to inspection of cannon barrels. After the magnetisation of the barrel, the defects in the barrel were detected by moving a compass along its length. The needle movement detected the defects in the surface of the barrel.
The metals can be magnetised by an indirect as well as a direct process. In the direct process of magnetization, electric current is passed through the objected that is being tested due to which a magnetic field is formed in it. Indirect magnetization takes place when an electric current is not passed through the object but magnetic field is attained when it is applied from an outside source.
The magnetic lines and the electric current are perpendicular to each other. The electric current may be Alternating Current (AC) or Direct Current (DC). During ...
... the process of magnetization with electric current or an electromagnet, the magnetic particles get attracted by the surface area that has a defect. The particles stick to the defective area. The MT method usually takes six to eight hours.
TYPES OF EQUIPMENTS USED

MPI machine – A wet MPI machine is one of the most important equipments that are required for detecting detects on the surface of the metals. The object to be inspected is placed on the head and tail stock of the machine. An induction coil is attached between the head and tail stock that is used to alter the orientation of the magnetic field.

Magnetic yolk – It is a hand-held device that is used for magnetic field induction. They are used for various purposes, like weld inspection. The yoke has to be rotated 90degrees while conducting the process of inspection.

APPLICATIONS

Some of the applications of MPI method are:

Wet particle inspection – The particles are left suspended while they are applied to its surface. Te particles in this method are smaller and can prove to be immobile when applied on a rough surface. This indicates that this method is more suited to objects with smooth surfaces.
Dry particle inspection – Contrary to wet particle inspection, this method is better suited to rough surfaces. The surface of the object is magnetized and the dry particles are applied to its surface. To create a pulsating magnetic field, a half-wave DC current can be used.
Residual magnetism - The particles are applied to the surface of the object after the process of residual magnetism has ended or while a part of the object is being magnetised. Applying the parts when the object is being magnetised will impart maximum strength to the leakage field. However, prolonged magnetisation may prove to be harmful, as the surface may get damaged.

In Edmonton, the process of Magnetic Particle Inspection is very advanced. The above read will give you an idea about the tools and applications that are followed in regards to Magnetic Particle Inspection in Edmonton.