Fluorescent Penetrant Inspection

What is Fluorescent Dye Penetrant Inspection?

Fluorescent Penetrant Inspection (FPI) is a non-destructive testing technique used to detect surface defects in metallic and non-metallic components. The FPI examination process reveals cracks, inclusions, porosity, and other surface flaws that cannot be detected with a visual inspection. At American Metal Testing, we offer industry-leading Fluorescent Penetrant Inspection services to ensure you have safe components that meet your specification requirements.

FPI Testing & Examination Services for Non-Destructive Testing

At American Metal Testing, before we begin the fluorescent liquid penetrant testing process, we clean the components to ensure all surfaces are free of contaminants that could prevent the penetrant from properly entering discontinuities. The component is submerged in a Level 3 high-sensitivity fluorescent liquid penetrant containing a dye that fluoresces when exposed to ultraviolet light.

The components are then placed into a temperature-controlled oven to ensure a thorough drying process. Once the component is adequately dry, a thin, uniform layer of developer is applied for the time necessary to allow the penetrant to be drawn back to the surface. This process creates a contrasting background that reveals discontinuities under black light. The component is then interpreted and evaluated to each customer’s requirements. Upon inspection completion, the component is cleaned to remove any examination material residues that may be detrimental to the subsequent operations.

What is the Liquid Pentrant Inspection Process?

The Fluorescent Liquid Penetrant Inspection process follows five primary steps: pre-cleaning, application of penetrant, excess penetrant removal, inspection, and post-cleaning.

1. Pre-Cleaning:

The test surface is cleaned to remove any dirt, paint, oil, grease, or any loose scale that could either keep penetrant out of a defect or cause irrelevant or false indications. Cleaning methods may include solvents, alkaline cleaning steps, vapor degreasing, or media blasting.

2. Application of Penetrant:

The penetrant is then applied to the surface of the item being tested. The penetrant is allowed to soak into any flaws. As expected, smaller flaws require a longer penetration time.

3. Excess Penetrant Removal:

The excess penetrant is then removed from the surface. The removal method is controlled by the type of penetrant used. Water-washable or solvent-removable, or hydrophilic post-emulsifiable penetrants are the common choices. Emulsifiers represent the highest sensitivity level, chemically interacting with the oily penetrant, making it removable with a water spray. 

4. Inspection:

The inspector will use visible light with adequate intensity (100 foot-candles or 1100 lux is typical) for visible dye penetrant. Ultraviolet (UV-A) radiation of sufficient intensity (1,000 micro-watts per centimeter squared) and low ambient light levels for fluorescent penetrant examinations are common. Inspection of the test surface should take place after 10- to 30-minute development time, depending on the product. This time delay allows the blotting action to occur. The inspector may observe the sample for indication formation when using visible dye. It is also good practice to observe indications as they form because the characteristics of the bleed-out are a significant part of the interpretation characterization of flaws.

5. Post Cleaning:

The test surface is often cleaned after inspection and recording of defects, especially if post-inspection coating processes are scheduled.

What Are the Applications of Dye Penetrant Inspection Services?

At American Metal Testing, we provide metal testing services for customers in some of the world’s most demanding industries, including military & defense, transportation, wind energy, and more. As a NADCAP-accredited non-destructive testing laboratory, we are qualified to provide testing services to aerospace manufacturers such as Boeing, Parker Aerospace, UTC Aerospace Systems, and others.

Contact American Metal Testing to Learn More About Our FPI Services

Questions about our Fluorescent Liquid Penetrant Inspection services? Contact our knowledgeable staff at American Metal Testing today to learn more. We offer a wide range of industry-leading non-destructive metal testing and inspection services. Choose American Metal Testing for all your industrial component testing services.