Dye Penetrant Inspection (DPI) also called as Liquid Penetrant Inspection (LPI) or Penetrant Test ( PT) is fast, economical 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.
Penetrant test is performed by cleaning the test surface thoroughly, applying coloured or fluorescent penetrant, allowing penetration time, removal of excess penetrant followed by application of developer ( dry or liquid form).
The developer assists to draw penetrant out from the surface breaking discontinuities.
After developer dwelling the test surface is examined for bleed out under natural light or black (UV) light (depending on the type of penetrant).
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.
LMATS can perform penetratn testing 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.
LMATS offers Liquid penetrant testing services from its laboratories in Melbourne (VIC), Albury, Sydney, Newcastle (NSW), Briabane (QLD) and Perth (WA) Laboratories. LMATS staff regularly performs Dye Penetrant testing in Tasmania, South Australia (SA), Northern Terrritory (NT). Contact one of the nearest LMATS laboratories near your job location.
Interesting Fact:
It is possible that an item tested using Liquid Penetrant test and complied in accordance with the product Standard may leak during the final hydrostatice testing. Most of the Standards specify dwelling time between 10mins to 30mins. This duration is not enough for liquid penetrant to enter cavities such as Macro Shrinkage in castings. Our experiment on one of the castings (during failure investigation) indicated that even 24 hour dwell time did not reveal this type of discontinuity. Upon cross sectioining and microscopic evalaution, this defect was located.
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