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Introduction to Magnetic Particle Inspection

Introduction
Introduction
Basic Principles
History of MPI

Physics
Magnetism
Magnetic
Mat'ls
Magnetic Domains
Magnetic Fields
Electromag. Fields
Field From a Coil
Mag Properties
Hysteresis Loop
Permeability
Field Orientation
Magnetization of Mat'ls
Magnetizing Current
Longitudinal Mag Fields
Circular Mag Fields
Demagnetization
Measuring Mag Fields

Equipment & Materials
Portable Equipment
Stationary Equipment
Multidirectional Equipment
Lights
Field Strength Indicators
Magnetic Particles
Suspension Liquids

Testing Practices
Dry Particles
Wet Suspension
Magnetic Rubber
Continuous & Residual Mag
Field Direction & Intensity
L/D Ratio

Process Control
Particle Concentration
Suspension Contamination
Electrical System
Lighting
Eye Considerations

Example Indications
Visible Dry Powder
Fluorescent Wet

Quizzes

Introduction to Magnetic Particle Inspection

Magnetic particle inspection (MPI) is a nondestructive testing method used for defect detection. MPI is fast and relatively easy to apply, and part surface preparation is not as critical as it is for some other NDT methods. These characteristics make MPI one of the most widely utilized nondestructive testing methods.

MPI uses magnetic fields and small magnetic particles (i.e.iron filings) to detect flaws in components. The only requirement from an inspectability standpoint is that the component being inspected must be made of a ferromagnetic material such as iron, nickel, cobalt, or some of their alloys. Ferromagnetic materials are materials that can be magnetized to a level that will allow the inspection to be effective.

The method is used to inspect a variety of product forms including castings, forgings, and weldments. Many different industries use magnetic particle inspection for determining a component's fitness-for-use. Some examples of industries that use magnetic particle inspection are the structural steel, automotive, petrochemical, power generation, and aerospace industries. Underwater inspection is another area where magnetic particle inspection may be used to test items such as offshore structures and underwater pipelines.