MPI Machine (Magnetic Particle Inspection)

Magnetic Particle Inspection (MPI) Machine 

Introduction

A Magnetic Particle Inspection (MPI) machine is a non-destructive testing (NDT) device used to detect surface and near-surface discontinuities such as cracks, seams, laps, voids, or inclusions in ferromagnetic materials (e.g., iron, nickel, cobalt, and their alloys).
It works on the principle of magnetism and magnetic flux leakage.

Working Principle

When a ferromagnetic material is magnetized, the magnetic flux lines flow through the material.
If there is a defect or discontinuity (such as a crack) on or near the surface, it interrupts the magnetic field, causing flux leakage at that point.

When magnetic particles (either dry powder or wet suspension) are applied to the surface, they are attracted to the leakage field, forming a visible indication of the defect’s shape, size, and location.