14-04-2011, 11:43 AM
Amit Golait
Poonam Kanojia
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NON-DESTRUCTIVE TESTING
Definition
The use of noninvasive techniques to determine the integrity of a material, component or structure or quantitatively measure some characteristic of an object.
Features
Any complicated objects can be tested without disturbing its configuration.
No effect on future use of test object.
Higher accuracy of fault finding than any other methods.
NDT can test faults deep inside the object .
Potential low cost.
On line testing.
Methods of NDT
Visual inspection
Tap testing
X-ray
Ultrasonic Testing
Acoustic Emission
Flux Leakage
Laser Interferometry
Acoustic Microscopy
Liquid Penetrant
Replication
Magnetic Particle testing
Thermography
Microwave
Eddy current
Magnetic Testing
Six most common NDT Methods
• Visual
• Liquid Penetrant
• Magnetic
• Ultrasonic
• Eddy Current
• X-ray
Visual Inspection
Most basic and common inspection method.
Tools include fiberscopes, bore scopes, magnifying glasses and mirrors.
Portable video inspection unit with zoom allows inspection of large tanks and vessels, railroad tank cars, sewer lines
Robotic crawlers permit observation in hazardous or tight areas, such as air ducts, reactors, pipelines.
Magnetic Particle Testing
The part is magnetized. Finely milled iron particles coated with a dye pigment are then applied to the specimen. These particles are attracted to magnetic flux leakage fields and will cluster to form an indication directly over the discontinuity. This indication can be visually detected under proper lighting conditions.