Liquid Penetrant Testing
Detecting Surface-breaking Flaws
Liquid penetrant testing, also known as liquid penetrant inspection, dye penetrant testing, penetrant testing or LPI, is reliable for detecting surface-breaking flaws in materials with a non-porous surface such as metals, plastics, glass and ceramics. This method relies on a fluorescent or visible dye penetrant seeping into a flaw such as a lap, seam, fracture or crack to form a surface indication that can be evaluated under special lighting. Both fluorescent and visible dye penetrant testing are performed at LTI on products up to 25 ft. in length.
LTI is equipped with three large liquid penetrant testing dip tanks, a 25 ft. dwell tank for pipe, tubing, bar, etc., and a large testing room with three high-intensity black lights. Water-washable and post-emulsifiable fluorescent penetrants in sensitivity levels 2, 3 and 4 are available to meet your specification or application. All orders are processed with the highest quality Magnaflux testing materials.
Inspections are performed according to customer specifications and industry requirements including MIL-STD-6866, MIL-STD-271, MIL-STD-2132 and ASTM E 1417. LTI NDT technicians are certified to ASNT SNT-TC-1A, NAS410/MIL-STD-410, Pratt & Whitney PWA-NDTQ and MIL-STD-2132. Laboratory Testing Inc. is PRI/Nadcap accredited for liquid penetrant inspection and provides a certified material test report with each order.
The Liquid Penetrant Testing Process
Before performing a liquid penetrant test, the surface of the test material must be thoroughly cleaned to remove any contaminants that could prevent the penetrant from entering flaws. Etching may be required if mechanical operations such as machining, sanding, or grit blasting have been performed on the item.
A fluorescent or red visible dye penetrant is applied to the cleaned test material, then it is left on the surface for a sufficient time to allow penetrant to seep into a defect. After this dwell time has elapsed, the excess penetrant is removed from the surface. Next, a thin layer of developer is applied to the item to assist in drawing penetrant trapped in flaws back to the surface where it will be visible as indications. The test item is viewed under special lighting so any indications can be evaluated according to the liquid penetrant testing specification or customer requirements. When performing fluorescent penetrant testing, indications must be viewed under darkened conditions with a high-intensity UV lamp.
- Dye Penetrants – Magnaflux brand
- Visible dye
- Fluorescent – water-washable and post-emulsifiable penetrants in sensitivity levels 2, 3 and 4
- Products Tested – metals and other non-porous materials
- Size Limitations – test materials up to 25 feet long
- Certified NDT Level II and Level III Inspectors – evaluate all test results
- ASTM E1417