Dye penetrant inspection

Liquid penetrant testing (according to DIN EN 571-1: penetrant, basic information ) is a non-destructive material testing, in which the capillary forces of fine surface cracks and pores are used to make them visible. A distinction is made between the dye penetration test and the fluorescent penetrant.

  • 3.1 General
  • 3.2 standards

Dye penetrant inspection ( in daylight )

The dye penetration test (FEP ), the surface of the component to be tested by grease and oil residue is freed and then applied a penetrant ( Kontraster ). This can be done by applying with a brush, by dipping in a bath or in a well- ventilated places, by spraying ( all of the above methods of application are also called "forced wetting "). The creep properties of the penetrant is high, uses the capillary action of the finest material separations, and it has a strong color contrast to the developer.

After the material to be tested is dependent on the exposure time, the surface is cleaned with water or a detergent, dried and applied to the developer. The developer is a fine powder (usually on lime ( chalk), suspended in water or solvent) by the capillary action of their own cavities ( absorbency ) that in the fine cracks (pores) pulls remaining penetrant. As a rule, the penetrant ( dye solution) is red and the developer knows. The high color contrast makes it easy to locate the error positions and the determination of the crack paths.

Fluorescent penetrant ( in the dark ( < 20 lux ) )

In low light can be used with fluorescent penetrant, which is made visible by means of UV irradiation. This test is much more sensitive than the penetration process, because the fluorescent particles produce a luminance contrast by converting the UVA radiation into visible light. The human eyes respond to luminance contrasts significantly more sensitive than color contrast. Main applications of the fluorescent penetrant are the automotive industry, aerospace industry.

Excitation sources for the fluorescent test

According to EN ISO 3059 a UV-A radiation source to excite the fluorescence must be used in a standard-compliant, fluorescent test. While in recent decades only discharge lamps ( mercury vapor, xenon, or metal halide lamps ) were used, UV-A LED lights are used today primarily.

In addition to the fluorescence excitation by means of UV light and blue light (450 nm) can be used. The use of blue-light systems is not in compliance with standards and requirements before the practical use of extensive qualifications and tests, since the UV- A radiation ( 365 nm) designed test equipment available on the market may develop sufficient luminosity under blue light.

UV radiation and blue light can severely endanger eyes and skin, therefore a corresponding risk analysis and adequate protection measures are very important.

UV radiation posed a known hazard to the eyes and skin but dar. Whereby the usual radiation exposure with the use of high-quality UV-A radiation sources and lighter personal protective equipment ( covering clothing and protective eyewear ) within an 8 hour shift is so small that there is no long-term damage and the permissible radiation dose will not be exceeded by far. The hazards caused by pure UV -A radiation, such as is used for the fluoresziernede surface crack testing, is quite harmless in itself. A strong increase of UV radiation dose by a lack of protective measures, such as the solarium (without protection ), where much UV - B and UV -C radiation is emitted in the eye, an inflammation of the cornea, as well as, increased at a, unprotected dose over months, years or even decades cataract disease ( cataract ) and cause the skin to sunburn or skin cancer.

Blue light in the visible range of the light spectrum and passes unhindered eye lens and is incident on the retina. ( - 480 nm 420) emitted, which is a high photochemical hazard (blue light hazard, blue light hazard ) to the eye from blue light systems, as they are partially used in the fluorescent crack detection is highly energetic ( actinic ), blue light. The emitted blue light can damage the retina to melt or burn ( photoretinitis ), which in a very short time to an incurable total or partial blindness ( minute range ) or impairment of color vision ( of seconds) can result. From a risk to the skin is not expected in the use of blue light systems.

Both types of radiation have a potential risk that must be identified and assessed in each individual case. For use on standard workstations, the German Society for Nondestructive Testing (DGZfP ) has issued a fact sheet (EM 6), which allows an easy and safe labor law in classification. This policy is available from the DGZfP in Berlin or the Beuth Verlag of DIN.

For the assessment of occupational exposure to optical radiation is relevant, such as Directive 2006/25/EC Regulation.

The indentation test is applicable to all materials that allow a clear indication of surface defects ( non-porous ), mainly on metals, plastics ( with limitations, such as Teflon), glazed ceramics and the like. For machine parts made of steel, a developer equal to the magnetic particle testing is due to the high susceptibility to corrosion against water usually used solvent-based, or, in ferro- magnetic (non- austenitic ) steels used.

The dye penetrant testing is apt to find cracks (up to a thousandth of a millimeter width) in the surface of the material quickly. However, there may be so-called false indications in harsh or brittle surfaces. These ads are no voids. Also, the method does not allow any statement about the missing depth ( crack depth ) with respect to the display intensity: an example pink colored display does not necessarily indicate a less deep crack out as a deep red display. This partial lack of sensitivity has meant that this method is no longer permitted as test methods, for example, in tests in general aviation.

Standards for liquid penetrant

General

Penetrant, particularly in the aviation and aerospace industry, are not performed by the original German DIN EN ISO 3452, but primarily by the American AMS 2644, the ISO 3452-2 now is very similar. To test according to this standard may only products that are listed in QPL ( qualified products list ) of the AMS 2644 and thus allowed to be used. Main differences are present in the ISO classification of the sensitivity at Farbeindringprüfmitteln and the consideration and approval of fluorescent Farbeindringmitteln.

Standardize

  • DIN 25435-2, Recurring inspections of the components of the primary circuit of light water reactors - Part 2: Magnetic particle and penetrant
  • DIN EN 1371-1, Founding - Liquid penetrant testing - Part 1: Sand, gravity die and low pressure
  • DIN EN 1371-2, Founding - Liquid penetrant testing - Part 2: Precision castings
  • DIN EN 2002-16, Aerospace series - Metallic materials; Test methods - Part 16: Non-destructive testing, penetrant testing
  • DIN EN 10228-2, Non-destructive testing of steel forgings - Part 2: Penetrant
  • DIN EN ISO 10893-4 Non-destructive testing of steel tubes - Part 4: penetrant inspection of seamless and welded steel tubes for the detection of surface imperfections
  • DIN EN ISO 3059, Non-destructive testing - Penetrant testing and magnetic particle testing - Viewing conditions
  • DIN EN ISO 3452-1, Non-destructive testing - Penetrant testing - Part 1: General principles
  • DIN EN ISO 3452-2, Non-destructive testing - Penetrant testing - Part 2: Testing of penetrant materials
  • DIN EN ISO 3452-3, Non-destructive testing - Penetrant testing - Part 3: Control body
  • DIN EN ISO 3452-4, Non-destructive testing - Penetrant testing - Part 4: Equipment
  • DIN EN ISO 3452-5, Non-destructive testing - Penetrant testing - Part 5: Penetrant testing at temperatures above 50 ° C
  • DIN EN ISO 3452-6, Non-destructive testing - Penetrant testing - Part 6: Penetrant testing at temperatures below 10 ° C
  • DIN EN ISO 12706, Non-destructive testing - Penetrant testing - Terminology
  • DIN EN ISO 23277, Non-destructive testing of welds - Penetrant testing of welds - Acceptance levels
  • ASTM E 165, Standard Practice for Liquid Penetrant Examination for General Industry
  • ASTM E 1417, Standard Practice for Liquid Penetrant Testing
Lens (anatomy) Austenite
299029
de