Choosing the Right FPI Penetrant System

Choosing the right liquid penetrant system can be tough given that there are multiple varieties of developer types and options for use. FPI systems use a form of non-destructive testing (NDT) to detect flaws in materials.

Within aerospace, the NDT supplies are used in the manufacture, design and maintenance of aircraft. However, one set of penetrant materials does not automatically work in every application.

Factors to Consider

When selecting the right penetrant materials, several factors need to be considered. Note that the FPI penetrant system varies in capabilities, size and shape. Therefore, for each application, several factors must be considered.

These may include:

  • The material: Solvent removable methods may damage the surface because of the incompatibility existing between the under test and the penetrant.
  • Size and type of defect: A post-emulsifiable method can detect wide and shallow defects. The fluorescent method is the best for detecting fine defects.
  • The number of parts to be tested: Fluorescent systems are best for batch inspections due to their high sensitivity to fluorescent indications.
  • Geometry and intricacy: Post-emulsifiable methods may leave tracks of excessive background coloration.

If sensitivity is your primary drive when choosing a penetrant system, decide if you will need a visible dye penetrant or a fluorescent penetrant. FPI systems produce a detectable indication from small defects.

Naturally, because the human eyes are sensitive to dark indications on dark backgrounds, they tend to be drawn more to fluorescent indications. Bespoke NDT systems reveal the material’s characteristics, including the tensile strength, the toughness of the fracture and ductility.

The use of NDT in Aerospace

In aviation, the most critical factor is safety. This is why NDT is employed in the lifecycle of each product. That includes the designing of new aircraft, the inspection of engines and structures and the qualification of new industry material.

In the development phase, this system may be used to help in the production of flexible and light materials. Engineers use this system to test the aircraft and certify its performance and durability. It is also used to investigate issues within the aircraft.

Determining the Best Option

The visible penetrant may be the best choice under certain circumstances. When inspecting large defects, a highly sensitive system may not be your best choice, given that it may give an extended length of irrelevant indications.

In past inspections, this type of dye has been seen to give excellent results when the flaws are located in weldments or when the surface is rough. Because visible dye penetrants do not need a dark area, they are easier to use in the field.

The other consideration would be deciding on whether to use post-emulsifiable, solvent removable or water washable penetrants.

The use of FPI Electrostatic Penetrant Line is increasing, thanks to the advanced technology and data handling. Aerospace testing is vital for the safety of passengers. For NDT to be carried out, adherence to the stipulated standards must be observed.