Liquid penetrant is applied to the surface and is drawn into defects by capillary action.
Testing with Dye Penetrants (PT) is
- manual and slow
- only used to detect defects appearing on the surface of the material
- highly effective for surface defects
- used mostly to detect tiny cracks in the surface
- used in combination with other non-destructive testing such as radiographic or Eddy Current testing.
Illustration: Dye penetrant testing, arrangement sketch
In principle this method of testing is independent of size.
- Penetrant fluid is applied to the surface of the test object and penetrates into any cracks.
- Penetrant fluid is removed from the surface but not from the cracks.
- The developer acts as a blotting paper and sucks up penetrant fluid from the crack.