Dye penetrant inspection DPalso called liquid penetrate inspection LPI or penetrant testing PTis a widely applied and low-cost inspection method used to check surface-breaking defects in all non-porous materials metals, plastics, or ceramics. The penetrant may be applied to all non-ferrous materials and ferrous materials, although for ferrous components magnetic-particle inspection is often used instead for its subsurface detection capability. LPI is used to detect casting, forging and welding surface defects such as hairline cracks, surface porosityleaks in new products, and fatigue cracks on in-service components.
Nondestructive testing NDT is a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The six most frequently used NDT methods are eddy-currentmagnetic-particleliquid penetrantradiographicultrasonicand visual testing. Various national and international trade associations exist to promote the industry, knowledge about non-destructive testing, and to develop standard methods and training.
For visitors who are not already familiar with NDT, the general information below is intended to provide a basic description of NDT and the most common test methods and techniques used when performing NDT. Nondestructive testing NDT is the process of inspecting, testing, or evaluating materials, components or assemblies for discontinuities, or differences in characteristics without destroying the serviceability of the part or system. In other words, when the inspection or test is completed the part can still be used.
An understanding of the benefits and drawbacks of each form of nondestructive examination can help you choose the best method for your application. The philosophy that often guides the fabrication of welded assemblies and structures is "to assure weld quality. The application determines what is good or bad.
Penetrant test is performed by cleaning the test surface thoroughly, applying coloured or fluorescent penetrant, allowing penetration time, removal of excess penetrant followed by application of developer dry or liquid form. The developer assists to draw penetrant out from the surface breaking discontinuities. After developer dwelling the test surface is examined for bleed out under natural light or black UV light depending on the type of penetrant.
Dye Penetrant Inspection DPI also called as Liquid Penetrant Inspection is an efficient, economical and widely used non destructive test method to detect surface-breaking discontinuities in all non-porous materials. More Announcements More Events
However, weld inspections involve far more than simple visual inspections to determine the quality of the weld connections. Destroying the weld is not an option, as it would destroy the structure or assembly that the weld secures. Instead, technicians use nondestructive testing NDT to determine the quality of a weld.
A dye penetration test is done to locate surface-breaking defects on ceramics, plastics, metals and other non-porous materials. As the name implies, this inspection method involves the penetration of dye into the surface defects and discontinuities. The dye or penetrant is applied through spraying, dipping or brushing.
Liquid penetrant examination is one of the most popular Nondestructive Examination NDE methods in the industry. It is economical, versatile, and requires minimal training when compared to other NDE methods. Liquid penetrant exams check for material flaws open to the surface by flowing very thin liquid into the flaw and then drawing the liquid out with a chalk-like developer.
Liquid penetrant inspection 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. DPI is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities. Penetrant may be applied to the test component by dipping, spraying, or brushing. After adequate penetration time has been allowed, the excess penetrant is removed, a developer is applied.