Liquid Penetrant Control (PT)

The Non-Destructive Testing is carried out to highlight surface defects on all materials (castings, welds, pipes, etc.).

The method of penetrating liquid control is based on the visual examination of the surface after the application, in sequence, of a penetrating product and a detector .

of the Method with Penetrants

In the field of welding all the pressure components of the chemical, petrochemical and energy industries, the method with penetrating liquids allows to highlight, with greater sensitivity than visual inspection, the success of a weld seam.

In the field of plastic materials and composites, it can represent a valid alternative to the inapplicability of magnetoscopic methods and induced currents for the detection of surface discontinuities.

In the aeronautical sector it finds more extreme uses with highly sensitive products capable of discovering even very small cracks on aircraft components subjected to fatigue or thermal stress.

In the automotive and motor industry in general, the automation of control with penetrating liquids allows you to associate high productivity with a higher and constant quality of vehicle components, turbines, etc.





of the Penetrating Liquid Method

Among the ADVANTAGES of non-destructive testing with penetrating liquids, the most important are:

  • applicability on all materials, metallic and not;
  • the wide applicability, independent of the geometry of the pieces to be examined;
  • highlighting of outcropping discontinuities in surfaces, even of very small dimensions;
  • a fair speed in applying the process.

The method never allows the identification of subsurface discontinuities, nor of discontinuities emerging on the surface but with traces of contaminants such as: paints, greases and oils, oxides, liquids, etc.
For this last reason, the surface preparation phase is very important in the application process, which essentially consists in its thorough cleaning.

The method does not allow, for obvious reasons, the control of very porous materials.

in the control with penetrating liquids

For the application of the process two products are always required: the PENETRANT LIQUID and the DETECTOR.
Depending on the method of removing the penetrant, the following may also be required: the emulsifier or the remover solvent.

It is that liquid which, with its penetration characteristics resulting from the three properties, surface tension , wetting power and viscosity , is capable of penetrating into discontinuities even of very small dimensions .

The colored trace that is created as soon as the application process is completed highlights the geometry of the discontinuity itself.
Penetrating liquids are mixtures generally consisting of a base product consisting of oils or light oils from aromatic and aliphatic hydrocarbons, modified with specific additives in order to increase the flash point, and colored or fluorescent pigments.

Depending on the color, the penetrants are divided into:

    usually red in color, they contain colored pigments visible in natural light. The defect is identified by contrasting the color between penetrant and the white of the detector.
    yellow, they contain fluorescent pigments visible on inspection only by exciting the fluorescence with special Idi Wood or ultra violet black light lamps), in a darkened environment.
    usually reddish in color, they are a particular blend of the two types of penetrants described above.
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