DPI, also called liquid penetrant inspection (LPI) or penetrant testing (PT), is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). DPI is used to detect casting, forging and welding surface defects such as cracks, surface porosity, leaks in new products, and fatigue cracks on in-service components.
In the laboratory Inidam operate three stand alone DPI facilities operated by trained and highly dedicated team of technicians and inspectors:
1) Britemor 455 Fluorescent Water Wash Level 2 sensitivity Line incorporating an PD3 powder developer and UV-A black light inspection booth.
2) Britemor 446 Fluorescent Water Wash Level 3 sensitivity Line incorporating an PD3 powder developer and UV-A black light inspection booth.
3) Britemor 768 Fluorescent Post Emulsified Level 3 sensitivity Line incorporating an PD3 powder developer and UV-A black light inspection booth.
Both systems are capable of handling both small batches of items or very large volumes of components.
Typically Inidam can achieve a 1 – 3 day turnaround of work, with a collection and delivery service available to clients. Available in the laboratory and on site is a portable, visible DPI system, which utilises aerosol spray cans containing Red Dye, Developer, and Solvent Cleaner. We operate with:
- Chemetall Red Dye Solvent Removable/ Post Emulsified Checkmor 240.
- Chemetall Solvent Remover S76.
- Chemetall Developer LD7
This system is extremely portable and can be used anywhere at short notice by our flexible DPI inspectors.
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. The developer helps to draw penetrant out of the flaw where a visible indication becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending upon the type of dye used – fluorescent or non-fluorescent (visible).
DPI inspection is an extremely sensitive process and can be influenced by a number of environmental factors. The cleanliness of the component tested is considered vital to the integrity of the test. Inidam operate a vapour degreasing plant that can be used on a majority of metals.