Magnetic Particle Testing

• When a ferromagnetic material is magnetised the flux lines flow inside the component

• When there is a discontinuity in the material there is flux leakage

• The leaking flux attracts a magnetic medium resulting in an indication.

Types of magnetisation

• Longitudinal Magnetisation

• Circular Magnetisation

o AC Magnetisation

o DC Magnetisation

o HWDC magnetisation

MAGNETIC PARTICLE TESTINGLONGITUDINAL MAGNETISATION

COIL METHOD YOKE METHOD.

HEAD SHOT METHOD

PROD METHOD CENTRAL CONDUCTOR

Types of Magnetisation - Circular Magnetisation

KETO RING

PIE-GAUGE

GROOVE BLOCK

CURRENT REQUIREMENTLONGITUDINAL FIELD

CIRCULAR FIELD

Magnetic field within article

Magnetic material

MAGNETIC FIELD DISTRIBUTION

MAGNETIC FIELD DISTRIBUTION

DISTORTED FIELD

MAGNETIC MEDIUM

DryWet

• Fluorescent – Requires Ultra violet lamp in darkened area – More sensitive than

• Non – Fluorescent

Magnetic Medium - Dry

• Medium about 30 – 50 microns

• Mixture of spherical and elongated powders

• Spherical shape helps in mobility

• Elongated shape helps in alignment to magnetic field

Dry Medium

MAGNETIC MEDIUM - WET

• Oxides of iron used in suspension with water, kerosene, petroleum oil.

• Size : 20- 30 microns• More sensitive than dry

medium

STAGES OF MAGNETIC PARTICLE TESTING

• Pre - Cleaning

• Magnetisation

• Applying magnetic medium

• Inspection

• Post cleaning

• Demagnetization

Magnetisation

• Magnetisation to be applied in two mutually perpendicular direction

• Magnetic medium to be applied when the magnetisation is ‘ON’

• Adequacy of field to be checked by field indicator ( Pie Gage )

• Magnetic medium could be wet or dry / Fluorescent or non-fluorescent

MT Indications

MT Indications

MT Indications

MT Indications

MT INDICATIONS

MT INDICATIONS

MT INDICATIONS

Forging Burst

MT INDICATIONS

MT INDICATIONS

MT INDICATIONS

MT INDICATIONS

MT INDICATIONSLigament crack

MTNON-RELEVANT INDICATION

LOW PERMEABILITY(HARD )

HIGH PERMEABILITY (SOFT)

MTNON-RELEVANT INDICATION

Tool

Carbide tip

Indication

MTNON-RELEVANT INDICATION

MT False Indication

Demagnetisation• Residual magnetism affects

further operation such as welding.

• Demagnetisation is preferably done with AC

• Object is moved slowly away from coil

• After demagnetisation residual magnetism is checked with gauss meters

Magnetic Particle Testing

PROD METHOD