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Dye Penetrant Inspection (DPI) also called as Liquid Penetrant Inspection (LPI) or Penetrant Test ( PT) is fast, economical, portable and widely used non destructive test method to detect surface-breaking discontinuities in all non-porous materials (metals, plastics, or ceramics).

Penetrant test is based  upon the principles of capillary action where liquid penetrates into a cavity. With this testing method, the test object is throughly cleaned and then coated with a solution that contains a visible or fluorescent dye. Excess solution is then removed from the surface of the object but is left in surface breaking defects. A developer is then applied to draw the penetrant out of the defects.

With fluorescent dyes, ultraviolet light is used to make the bleedout fluoresce brightly, thus allowing imperfections to be readily seen. With visible dyes, a vivid color contrast between the penetrant and developer makes the bleedout easy to see.

Fluorescent Dye Penetrant Inspection (FDPI) is the most sensitive test method.


Dye penetrant Inspection (DPI) is predominantly used on non-ferrous materials in aerospace industries, shipping and offshore, petrochemical industries and stainless industry.

Some of the common parts tested are stainless steel welded joints, aluminium alloys joints, turbine blades, stainless steel fittings, castings and forgings, weld overlays (stellite), aerospace engine parts, etc.

Vertest performs DPI / LPI / PT regularly in accordance with AS 2062,  ASTM E1417, ASTM E165, ASTM E1418, ASTM E433, ASTM 1209, ASTM E1219, ASTM E1220, ASME V Article 6, EN 571-1 and similar national and international standards.

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