Dye Penetrant Inspection

Dye Penetrant Inspection, also called Liquid Penetrant Inspection (LPI), is widely applied in today’s oil and gas industries and this low-cost inspection method is used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). Penetrant may be applied to all non-ferrous materials, but for inspection of ferrous components, magnetic-particle inspection is preferred for its subsurface detection capability. DPI is used to detect casting and forging defects, cracks, and leaks in new products, and fatigue cracks on in-service components.


  • Section of material with a surface-breaking crack that is not visible to the naked eye.
  • Penetrant is applied to the surface.
  • Excess penetrant is removed.
  • Developer is applied, rendering the crack visibility.