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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
