Liquid Penetrant (PT) testing is used for finding discontinuities open to the surface on materials with relatively smooth, nonporous surfaces. It works based on the properties of capillary action, or the ability of a liquid to rise or climb when confined to a small opening due to surface wetting properties of the liquid. It uses a dye (visible or fluorescent) to penetrate discontinuities open to the surface, is removed after a short dwell time, and then is covered with a developer which provides a background to see indications against. PT is very versatile and can be used in both field and shop applications.
Weld Procedure and Welder Performance Certification
Ground Penetrating Radar (GPR)