Credits: Polubothu Ganesh, Procurement; Reliance
Commonly used Non Destructive Testing (NDT) techniques for inspection of Weld Joints:
Liquid Penetrant Examination: Based on principle of ‘Capillary action.’
liquid with high surface wetting characteristics is applied to the surface of the part and allowed time to seep into surface breaking defects.
A developer (powder) is applied to pull the trapped penetrant out the defect and spread it on the surface where it can be seen.
penetrant used is often loaded with a fluorescent dye and the inspection is done under UV light to increase test sensitivity.
Magnetic Particle Examination
in ferromagnetic materials.
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.
Radiography Examination
passing penetrating ionizing radiation through them and recording the transmitted radiation pattern on X ray Films.
Ultrasonic Examination
High frequency sound waves are introduced into a material and they are reflected back from surfaces or flaws.
Reflected sound energy is displayed versus time, and inspector can visualize