Liquid Penetrant Testing

Detecting Surface-breaking Flaws

Liquid penetrant testing (PT), also known as liquid penetrant inspection (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 penetrant inspection and visible dye penetrant testing are performed at LTI on products up to 25 ft. in length. Water-washable and post-emulsifiable fluorescent penetrants in sensitivity levels 2, 3 and 4 are available to meet your specification or application.

LTI is equipped with three large penetrant inspection dip tanks, a 25 ft. dwell tank for pipe, tubing, bar, etc., and a large testing room with three high-intensity black lights. 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 Test 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 red visible dye or fluorescent 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 test specification or customer requirements. When using fluorescent penetrant inspection, indications must be viewed under darkened conditions with a high-intensity UV lamp.

LTI Capabilities

• Penetrants – visible dye, water-washable and post-emulsifiable fluorescent dye in sensitivity levels 2, 3 and 4
• Products Tested – non-porous
• Size Limitations – test materials to 25 feet long

Specifications

• ASTM E1417