PENETRANTS - TESTING OF WELDED JOINTS BY NON-DESTRUCTIVE METHODS

Penetrant testing is based on the capillarity effect. By applying the penetrant to the surface of the object, the penetration of the penetrant into surface irregularities occurs. By cleaning the test surface and applying the developer, the penetrant is extracted from the irregularities and then the indications of the irregularities become visible.

Frnon-transit testing or penetrant testing is often used in the testing of welded joints on structures as a non-destructive test. A penetrant (usually red) is applied to the previously cleaned and degreased surface. After penetrating into a possible crack (the time of penetration, i.e. penetration into the cracks depends on the type of penetrant and the dimensions of the crack, but it takes approximately 10 to 15 minutes), the penetrant is removed in an appropriate way (water, dry

cloth). With penetrants that are removed with water, you should be careful and direct the water jet parallel to the surface of the sheet, so that the water jet does not push the penetrant out of the crack. After drying the surface of the sheet (dry cloth), a developer (usually white) is applied, which draws the penetrant from the crack, so a red line from the penetrant from the crack is easily visible on the white surface of the sheet. For thinner sheets, a penetrant is applied on one side and a developer on the other. If there is a crack through the full thickness of the sheet, then the developer will draw the penetrant to its side, which will be detected as an easily visible red line of penetrant from the crack on the white (from the developer) surface of the sheet. With this method, it is possible to detect cracks with a length of 0.1 mm and a width of 0.03 mm.

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