Welcome to the REL frequently asked questions page about non-destructive testing, Fluorescent Penetrant Inspection (FPI), Non-Destructive Testing (NDT), Magnetic Particle Inspection (MPI), and Dye Penetrant Inspection. Submit a question
- What is FPI?
FPI stands for Fluorescent Penetrant Inspection. It is a testing method used to detect cracks in safety critical components that are made out of non-porous materials, such as metals, plastics, ceramics, and glass. The process utilizes fluorescent dye, which is applied to the part and fills any existing cracks. A special UV light is then used to illuminate where the penetrant has gotten into the imperfections of a part being tested.
- What is non-destructive testing (NDT)?
Non-destructive testing (NDT) is a testing method that will not cause damage or alter the integrity of safety critical components being tested for imperfections. Fluorescent Penetrant Non-destructive testing methods use special dye and developer components to find cracks in parts that are not visible to the naked eye.
- What are the different types of NDT?
Non-destructive testing includes Dye Penetrant Inspection, Fluorescent Penetrant Inspection (FPI), Magnetic Particle Inspection (MPI), x-ray, Ultrasonic, and Eddy Current.
- Why is non-destructive testing important?
Non-destructive testing is important because it provides a consistent and safe method of ensuring the fidelity of safety critical components. This type of testing prevents the use of worn parts that can break and cause injury.
- What is magnetic particle inspection?
Magnetic particle inspection (MPI) is a non-destructive testing method that is used to detect surface defects and cracks in parts that are made out of magnetic materials, such as iron, nickel, cobalt, and other ferromagnetic alloys. MPI is the process of using a magnetic field to determine where a crack may be on parts such as forgings, castings, fasteners, weldments, machined, or stamped parts.
- What is Dye Penetrant Inspection?
Dye penetrant inspection, also known as liquid penetrant inspection, is also interchangeable with Fluorescent Penetrant Inspection. It is dependable and harmless to the part being tested. Fluorescent dye is applied to a part, and the cracks hold the penetrant within, making them visible to the naked eye once the developer is applied and a UV light illuminates the dye.
- Do parts have to be cleaned prior to inspection?
The first step in non-destructive testing is to clean the part. It is important that the correct cleaner is used in the cleaning process before the penetrant can be added to the surface of the part. This ensures that the defects on the part surface are accessible to the penetrant fluids.
- What is Penetrant?
A penetrant is a substance that can get into cracks and other surface defects. It is used in dye penetrant inspections to help make cracks and imperfections in parts visible to the naked eye. Fluorescent dyes are also used as penetrants and developers are used to bring them to the surface to help make cracks visible under UV-A light.
- How many times is a product tested using the FPI process during manufacturing or repair?
A product can be tested up to ten times depending on the specification. Automating a process will increase process precision to reduce process variability allow for minimizing the number of times a part needs to be processed. This reduction can be significant sometimes on the order of 1/3!
- What is a developer?
A developer is a substance that is used to bring the penetrant back to the surface of the part, thus making the penetrant visible as it emerges from a crack or imperfection in a part.
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