Fluorescent penetrant inspection is a type of non-destructive testing that detects surface cracks in non-porous safety critical components.

Fluorescent Penetrant Inspection is a non-destructive testing method that is used to detect surface cracks, seams, or discontinuities in parts. Parts that undergo the fluorescent penetrant inspection process are typically safety-critical components in aerospace and automotive vehicles. These surface defects show up during the inspection process as ‘indications’ under black light. These parts are specifically used in airplanes, helicopters, automobiles, and in medical implants.

Dye penetrant inspection and liquid penetrant inspection are synonymous with Fluorescent Penetrant Inspection (FPI). This inspection process is robust and harmless for the part being tested. FPI uses a dye penetrant that will fluoresce under UV-A (365 nm) black light. The fluorescent dye becomes ‘stuck’ in the surface indications on the surface of the part after processing according to ASTM 1417. The penetrant that is stuck then becomes observable under black light during the inspection process. The cracks will hold the fluorescent penetrant within, and when a developer is applied, the cracks are made visible to the naked eye.

REL Engineered Solutions LED Lighting UV-A C4 Nomad-GO Inspection

Fluorescent Penetrant Inspection Process for Non-Destructive Testing

Fluorescent penetrant inspection is used on non-porous materials, such as metals, plastics, ceramics, and glass. This inspection is a critical part of manufacturing safety-critical components. Surface cracks propagate once a critical size is reached. This phenomenon causes catastrophic part failure. It is important that proper processing is performed to reveal indications of surface cracks so that the part can be repaired or replaced. As a safety-critical part goes through its life cycle, it is important to perform routine non-destructive evaluation in the form of fluorescent penetrant inspection to minimize failure of parts in service.

Testing can be done on new products or parts that are in use and need to be analyzed for cracks that may have developed over time.

Simplified Steps of Fluorescent Penetrant Inspection

  1. Clean the part or prepare the surface to be inspected
  2. Apply the penetrant to the product and allow it to dwell while the penetrant is ‘wetting’ the surface of the part
  3. Remove excess penetrant
  4. Apply Developer to ‘blot’ the penetrant to the surface of the part
  5. Inspect the part under a ultraviolet light to look for indications that may be cracks or other surface discontinuities.
  6. Document indications.

ASTM E 1417 Standards

Liquid Penetrant Inspection testing needs to meet the standard practice ASTM E1417. The ASTM standards set the basic parameters for levels, sprays, brush, application, dwell time, process time, and temperatures. Each manufacturing company or OEM will have a local process specification (LPS) that also dictates the Fluorescent Penetrant Inspection testing methods for their specific parts. The local process specification generally dictates the drying time, dwell times, method, form of developer, and rinse requirements.

Learn more about ASTM E1417.

Industries that Use Fluorescent Penetrant Inspection

Fluorescent Penetrant Inspection is used in industries that are manufacturing safety-critical components. OEM’s, MRO facilities, and Manufacturers for Aerospace, Aviation, Medical, Automotive, Energy, Defense, All Terrain Vehicles, and more use FPI to limit the failure of parts in service.

FPI Equipment & LED UV-A Lighting

REL partners with customers around the world by providing state-of-the-art technology and engineering with automated, intelligent Fluorescent Penetrant Inspection Equipment and LED UV-A Lighting.

REL Engineered Solutions Non-Destructive Testing Automated FPI Testing Penetrant

Automated Fluorescent Penetrant Inspection

An automated Fluorescent Penetrant Inspection (FPI) processing line is a system that is driven by a computer. Automated FPI processing ensures processing that is precisely performed to a preset recipe to ensure that there is no process variability between operators. An automated system can automatically clean, etch, apply penetrant, emulsifier, rinse, dry the part, and apply the developer.

High throughput can be achieved with minimal operator interaction can also be achieved in situ with a processing database that can provide an exact time-stamped history of all processes that were performed on a particular part and be stored for decades! REL specializes in communicating with plant-wide DCS systems that monitor processes throughout the manufacturing process.

Learn more about our Automated Fluorescent Penetrant Inspection Systems.

Human-Driven FPI Lines

REL’s human-driven FPI lines feature modular stations and are built to rigorous specifications. Our systems increase facility throughput and are engineered to be reliable, robust, and precise.

Learn more about our human-driven FPI lines.

REL Engineered Solutions LED Lighting UV-A Dunk
LED UV-A Lighting

LED UV-A lamps are used to inspect the surface for cracks as the penetrant moves to the surface of the part. REL manufactures LED UV-A Lamps to meet the needs of the industry. Our lamps are tested and comply with Rolls-Royce RRES 90061 requirements and ASTM E3022 standards and meet specifications of ISO 3059.

Learn more about our LED UV-A Lighting.