Dye-Penetrant Examination Developers

The developer should be applied to the surface of the workpiece immediately after the excess liquid penetrant is removed from the surface. The developers used for solvent-removable dye-penetrant systems are generally suspensions of the developer powder in a quick drying solvent, that can be sprayed onto the surface of a workpiece from an aerosol can. Quick drying of the solvent allows an essentially uniform layer of developer powder to be obtained on the surface without any running, even on vertical surfaces.

The developer should be applied in a layer thick enough to completely mask the surface, but if the layer of developer is too thick, the liquid penetrant drawn out of a flaw may not reach the top of the layer and the indication of a flaw can be obscured. The minimum development time required by ASME Code, Section V, is 7 minutes.

The dye-penetrant drawn out of a flaw by the developer should stain the developer layer a deep red. A light pink color may indicate that excessive cleaning inadvertently removed penetrant from the flaws, and that smaller flaws may not have been revealed. Therefore, when pale indications are obtained, the examination should be repeated with less vigorous cleaning.

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