What is Dye Penetrant Inspection

Dye Penetrant Inspection (DPI), also called Liquid Penetrant Inspection (LPI) or Penetrant Testing (PT), is one of the oldest and simplest NDT methods. This technique is used to detect any surface-connected discontinuities such as cracks from fatigue, quenching, and grinding, as well as fractures, porosity, incomplete fusion, and flaws in joints.


Why is Dye Penetrant Inspection used

The purpose of DPI is to identify defects in good time in order to prevent premature or unexpected machine failure which can result in accidents, loss of productivity and costly downtime.

  • High sensitivity (small discontinuities can be detected).
  • Few material limitations (metallic and non-metallic, magnetic, non-magnetic, and conductive and nonconductive materials may be inspected).
  • Rapid inspection of large areas and volumes.
  • Suitable for parts with complex shapes.
  • Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.
  • Portable (materials are available in aerosol spray cans).
  • Low cost (materials and associated equipment are relatively inexpensive).