Liquid Penetrant Testing is one of the most common surface crack detection in regular use. The Dy-Mark Flawchek Crack Detection System makes use of the Colour Contrast method for detecting fine cracks, flaws and surface discontinuities in welded metalwork. The process for applying the Colour Contrast method is as follows:

The first step is to ensure that the surface being tested is clean and free from all contamination e.g. grease, oil, rust and paint. Spray the test area with the Dy-Mark Flawchek Cleaner, wipe the surface with a cloth and allow the area to dry thoroughly.

In the second stage of the process, a penetrating liquid is applied to the surface of the weld to be tested. After Dy-Mark Flawchek Penetrant has been applied, it must then be allowed to “dwell” for at least 10 minutes. The “dwell” time is a predetermined soak period that allows for the adequate penetration of the liquid penetrant into any surface breaking discontinuities. Allow excess Penetrant to drain and wipe over the test area with a cloth.

The interpretation and evaluation of the test results involves the detection of penetrant bleed-out from within any surface discontinuity.

The method of detection for the Colour Contrast method is dependent on the bright contrast between the red penetrant dye and the white developer background covering the surface of the weld being tested.

Test evaluations using the Colour Contrast method are able to be conducted in ordinary light.

Liquid Penetrant Testing can only detect flaws, cracks and surface discontinuities in welds that are open to the surface and to which Penetrant can be applied.

Liquid Penetrant Testing cannot detect flaws and cracks that are sealed within the body of the weld.

The testing of rough and uneven surfaces or porous substrates is not recommended as results can be hindered by false indications.