Dye penetration is used to examine the surface of a steel tube or welded sheet to determine if there are any surface breaking flaws (cracks) on the steel section. As Tubecon is a welded hollow section manufacturer the rest of the explanation will be done accordingly.
The dye penetration process is used predominantly to check for leaks in the weld of the steel hollow section of welded plate. Dye penetration can be used as a substitute to pressure testing, though the application is more costly than that off pressure testing.
Once the steel tube has been rolled a bright coloured liquid penetrant (the initiator) is applied to the outside surface of the steel section. This then is left to soak into the cracks, drawn by capillary action.
Once the soaking time on the steel tube has expired the excess penetrant is wiped from the steel section. A developer is applied to the steel hollow section. The developer, usually a colourless liquid spray, is applied by spraying it on the steel section. The developer then reacts with the initiator, showing the colour of the initiator on the surface. The darker the colour, the deeper the surface flaw will be. The coloured identification shows broader than the actual flaw on the surface of the steel tube, making it easier to see. The broader the coloured area the wider the flaw in the material will be.