Liquid penetrant inspection (LPI, or PT for "penetrant testing")

is used to inspect parts and weldments for open-

to-surface discontinuities. A penetrant solution is applied

to a clean, bare surface and allowed to dwell for a certain

amount of time. This allows the penetrant to be drawn into

tiny cracks and other discontinuities that are of interest to

the inspector. The surface is then wiped clean and a

developer applied. This draws out the trapped penetrant,

which soaks through the developer on the part surface

and reveals tiny indications which may not be visible to the

naked eye. Penetrant is used instead of magnetic particle

inspection when looking for cracks in non-ferrous metals

or in plastics and composites.

LPI can be performed using visible or fluorescent dyes,

and is available in a wide variety of sensitivity levels.




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