Non destructive testing

The penetrant method of non-destructive testing is based on capillary penetration of indicator
liquid (penetrant) into the surface defects (cracks, pores etc.). After intermediate cleaning and
subsequent drying, a developer is applied as a thin, white layer onto the surface to be
inspected. The developer “pulls” the penetrant out of the surface defects and makes them
visible as coloured, linear or rounded indications. Documentation is possible by means of
adhersive foil, photographic or video techniques.
Penetrant testing systems
Met-L-Chek, Standard Chek, Nord-Test
are reliable in detecting the defects with a
width down to the range of µm.
Necessary condition: defects must be open
to surface.
Systems are also used for the leak testing.
The examination of testing
media adequacy is done in
accordance with :
• AMS 2644
• AMS 2647
• DIN EN ISO 3452-2 (3)
• ASME
Penetrant inspection can accurately and
easily detect surface defects independent of
types, materials and surface configurations of
the objects to be tested. Other methods of
non destructive testing, can only be applied
for these requirements with restrictions.
Procedure of penetrant inspection.
Precleaning
Application of
penetrant.
Mechanically, with brush By stream process Degreasing with hot steam Cleaning with solvent
Predrying
Dip in bath Laying with brush Application by spraying Application by electrostatic mean
Intermediate
cleaning
With lint free cloth, water-moistened or a
sponge
With water-moistened brush Rinse with water With lint free cloth or sponge,
moistened with a special solvent
Drying
Dry in open air Wipe with a lint free cloth Blow with dry, clean air Dry with warm air
Application of
developer
Examination of the
surface and
documentation
By immersion(aqueous developer) Application from the diffuser /
aerosol (non-aqueous developer)
Viewing under day light or in artificial
illumination min.. 500 Lux (EN 571-1/EN
3059)
Electrostatic application(nonaqueous
developer)
Application of dry powder developer(
in special cases, e.g. extremely porous
surfaces)
If using fluorescent penetrant:
Documentation by adhasive foil
Ambient illumination: < 20 Lux
Photo-optical documentation Documentation by means of video
Intensity of UV: 1000µW/cm 2 filming or photocamera
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