Liquid Penetrant Testing / Dye Penetrant Testing (PT)

Relatively simple, inexpensive and reliable, liquid penetrant testing (PT) is used to locate cracks, porosity, and other defects that break the surface of a material

With the correct application, it will detect discontinuities ranging in size from the large to the microscopic. Liquid penetrant testing is used to inspect large areas very efficiently and will work on most nonporous material

Advantages

• • Is one of the most sensitive NDT method for detecting very small surface discontinuities.
• • Can be used on a wide variety of materials, including ferrous and nonferrous metals, alloys, powdered metal products, glass and some types of organic materials.
• • Can be performed with relatively inexpensive, unsophisticated equipment.
• • Is capable of examining all of the exterior surfaces of objects, even of complex shapes
• • Magnifies the apparent size of discontinuities, making the indications more visible. In addition, the discontinuity location, orientation and approximate length are indicated on the     part, making interpretation and evaluation possible.

Limitations

• • Discontinuities must be open to the surface, as well as free of foreign material that could restrict the entry of the penetrant into the discontinuity.
• • Liquid penetrants, emulsifiers and some types of developers may cause skin irritation.
• • Liquid penetrants may harm some nonmetallic materials, such as rubber and plastic. There is also the possibility of staining of porous or coated materials.
• • Some liquid penetrant materials contain volatile solvents thus, adequate ventilation is necessary, especially in confined areas.
• • Liquid penetrants, especially in aerosol form, are flammable. Inspectors must follow manufacture's recommendations regarding necessary personnel protective equipment when     using such equipment.