Penetrantprøvning

Penetrantprøvning, also known as dye penetrant inspection (DPI) or liquid penetrant testing (LPT), is a widely used non-destructive testing (NDT) method for detecting surface-breaking defects in materials. This technique is applicable to a wide range of non-porous materials, including metals, plastics, and ceramics. The principle behind penetrant testing relies on capillary action, where a liquid with low surface tension is drawn into and held within surface flaws.

The process typically involves several key steps. First, the surface to be inspected is thoroughly cleaned to remove any contaminants that could interfere with the penetrant. Next, a liquid penetrant is applied to the surface, usually by spraying, brushing, or dipping. This penetrant is allowed to dwell on the surface for a specified period, known as the penetration time, to ensure it seeps into any cracks or discontinuities. After the dwell time, any excess penetrant is removed from the surface, again taking care not to wash it out of the defects. A developer is then applied, which acts as a blotting paper, drawing the penetrant out of the defects and making them visible as colored indications against the developer background. Finally, the surface is examined under adequate lighting conditions to interpret the indications and determine the presence, size, and nature of any defects.

Penetrant testing is effective in revealing defects such as cracks, porosity, laps, and seams that are open to the surface. It is a relatively simple and cost-effective NDT method, making it a popular choice for various industries, including aerospace, automotive, and manufacturing. However, it is important to note that penetrant testing can only detect surface-breaking defects and cannot reveal subsurface flaws.