Liquid Penetrant Testing (PT)

Liquid Penetrant Testing or Penetrant Testing is an NDT technique used to detect surface flaws in all non-porous materials (metals, plastics, or ceramics). PT may also be applied to ferrous material, although for ferrous components the go to NDT method is Magnetic Particle Testing. PT is one of the easiest and least expensive NDT method and most used in many industries including oil and gas, refineries, aerospace, fabrication shops etc. PT is used to detect forging, casting, and welding surface defects sucks as surface porosity, cracks, etc. Surface preparation is required for this method. PT is based on the principle of capillary action. Penetrant can be applied by dipping, brushing, or spraying.  A Dwell Time is set which allows the dye to penetrate the surface, all excess penetrant should be removed, and a developer is then applied. The developer assists to draw the penetrant out of the flaws. PT is carried out under an ultraviolet or white light.