Page 171 - CITS - Welder - Trade Practical
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WELDER - CITS
Methods of non destructive tests
Objectives: At the end of this exercise you shall be able to
• explain the non-destructive testing methods
• explain the uses of the common non-destructive methods
• explain the uses of special non-destructive testing.
Non-destructive testing methods are classified as common testing and special testing methods.
Common non-destructive testing
– Visual inspection
– Leak or pressure test
– Stethoscopic test (Sound)
Special non-destructive tests
– Magnetic particle test
– Liquid penetrant test
– Radiography (X-ray) test
– Gamma ray test
– Ultrasonic test.
Liquid penetrant test: This test is based on the principle that coloured liquid dyes and fluorescent liquid penetrate
into the cracks and are used to check for surface defects in metals, plastics, ceramics and glass. A solution of
the coloured dye is sprayed on the clean welded joint and allowed to soak. Then the dye is washed off using a
cleaner, and the surface dried with soft cloth.
A liquid developer (white in colour) is then sprayed on the weld. The coloured dye comes out in the shape of
surface defects into the white developer coating. The defect can be seen in normal light with naked eyes.
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CITS : C G & M - Welder - Exercise 37
